for Journals by Title or ISSN
for Articles by Keywords
help
  Subjects -> ENGINEERING (Total: 2235 journals)
    - CHEMICAL ENGINEERING (188 journals)
    - CIVIL ENGINEERING (178 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1194 journals)
    - ENGINEERING MECHANICS AND MATERIALS (374 journals)
    - HYDRAULIC ENGINEERING (54 journals)
    - INDUSTRIAL ENGINEERING (60 journals)
    - MECHANICAL ENGINEERING (85 journals)

ENGINEERING (1194 journals)            First | 1 2 3 4 5 6 7 8 | Last

BER : Retail Survey : Full Survey     Full-text available via subscription   (Followers: 2)
BER : Survey of Business Conditions in Manufacturing : An Executive Summary     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Retail : An Executive Summary     Full-text available via subscription   (Followers: 3)
Bharatiya Vaigyanik evam Audyogik Anusandhan Patrika (BVAAP)     Open Access   (Followers: 1)
Biointerphases     Open Access   (Followers: 1)
Biomaterials Science     Full-text available via subscription   (Followers: 4)
Biomedical Engineering     Hybrid Journal   (Followers: 11)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 14)
Biomedical Engineering Letters     Hybrid Journal   (Followers: 5)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 18)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 16)
Biomedical Engineering: Applications, Basis and Communications     Hybrid Journal   (Followers: 6)
Biomedical Microdevices     Hybrid Journal   (Followers: 7)
Biomedical Science and Engineering     Open Access   (Followers: 2)
Biomedizinische Technik - Biomedical Engineering     Hybrid Journal  
Biomicrofluidics     Open Access   (Followers: 5)
BioNanoMaterials     Hybrid Journal   (Followers: 1)
Biotechnology Progress     Hybrid Journal   (Followers: 23)
Boletin Cientifico Tecnico INIMET     Open Access  
Botswana Journal of Technology     Full-text available via subscription  
Boundary Value Problems     Open Access   (Followers: 1)
Brazilian Journal of Science and Technology     Open Access  
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 5)
Bubble Science, Engineering & Technology     Hybrid Journal   (Followers: 1)
Bulletin of Canadian Petroleum Geology     Full-text available via subscription   (Followers: 2)
Bulletin of Engineering Geology and the Environment     Hybrid Journal   (Followers: 3)
Bulletin of the Crimean Astrophysical Observatory     Hybrid Journal  
Cahiers, Droit, Sciences et Technologies     Open Access  
Calphad     Hybrid Journal  
Canadian Geotechnical Journal     Full-text available via subscription   (Followers: 16)
Canadian Journal of Remote Sensing     Full-text available via subscription   (Followers: 13)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 4)
Case Studies in Thermal Engineering     Open Access   (Followers: 1)
Catalysis Communications     Hybrid Journal   (Followers: 5)
Catalysis Letters     Hybrid Journal   (Followers: 2)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 7)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 4)
Catalysis Today     Hybrid Journal   (Followers: 6)
CEAS Space Journal     Hybrid Journal   (Followers: 1)
Cellular and Molecular Neurobiology     Hybrid Journal   (Followers: 3)
Central European Journal of Engineering     Hybrid Journal   (Followers: 1)
CFD Letters     Open Access   (Followers: 2)
Chaos : An Interdisciplinary Journal of Nonlinear Science     Hybrid Journal   (Followers: 2)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 1)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 1)
Chinese Journal of Engineering     Open Access  
Chinese Science Bulletin     Open Access  
Ciencia e Ingenieria Neogranadina     Open Access  
Ciencia en su PC     Open Access  
Ciencias Holguin     Open Access  
Cientifica     Open Access  
CIRP Annals - Manufacturing Technology     Full-text available via subscription   (Followers: 11)
CIRP Journal of Manufacturing Science and Technology     Full-text available via subscription   (Followers: 10)
City, Culture and Society     Hybrid Journal   (Followers: 16)
Clay Minerals     Full-text available via subscription   (Followers: 9)
Clean Air Journal     Full-text available via subscription   (Followers: 2)
Clinical Science     Full-text available via subscription   (Followers: 8)
Coal Science and Technology     Full-text available via subscription   (Followers: 6)
Coastal Engineering     Hybrid Journal   (Followers: 9)
Coastal Engineering Journal     Hybrid Journal   (Followers: 2)
Coatings     Open Access   (Followers: 2)
Cogent Engineering     Open Access   (Followers: 1)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Color Research & Application     Hybrid Journal   (Followers: 2)
COMBINATORICA     Hybrid Journal  
Combustion Theory and Modelling     Hybrid Journal   (Followers: 6)
Combustion, Explosion, and Shock Waves     Hybrid Journal   (Followers: 11)
Communications Engineer     Hybrid Journal  
Communications in Numerical Methods in Engineering     Hybrid Journal   (Followers: 3)
Components, Packaging and Manufacturing Technology, IEEE Transactions on     Hybrid Journal   (Followers: 15)
Composite Interfaces     Hybrid Journal   (Followers: 4)
Composite Structures     Hybrid Journal   (Followers: 160)
Composites Part A : Applied Science and Manufacturing     Hybrid Journal   (Followers: 123)
Composites Part B : Engineering     Hybrid Journal   (Followers: 142)
Composites Science and Technology     Hybrid Journal   (Followers: 106)
Comptes Rendus Mécanique     Full-text available via subscription   (Followers: 2)
Computation     Open Access   (Followers: 1)
Computational Geosciences     Hybrid Journal   (Followers: 13)
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computational Science and Discovery     Full-text available via subscription  
Computational Water, Energy, and Environmental Engineering     Open Access   (Followers: 3)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 7)
Computer Science and Engineering     Open Access   (Followers: 9)
Computers & Geosciences     Hybrid Journal   (Followers: 8)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 4)
Computers and Electronics in Agriculture     Hybrid Journal   (Followers: 3)
Computers and Geotechnics     Hybrid Journal   (Followers: 8)
Computing and Visualization in Science     Hybrid Journal   (Followers: 3)
Computing in Science & Engineering     Full-text available via subscription   (Followers: 14)
Conciencia Tecnologica     Open Access   (Followers: 1)
Concurrent Engineering     Hybrid Journal   (Followers: 4)
Conference Proceedings - Lucian Blaga University Sibiu     Open Access  
Continuum Mechanics and Thermodynamics     Hybrid Journal   (Followers: 3)
Control and Dynamic Systems     Full-text available via subscription   (Followers: 5)
Control Engineering Practice     Hybrid Journal   (Followers: 34)
Control Theory and Informatics     Open Access   (Followers: 5)
Corrosion Science     Hybrid Journal   (Followers: 24)
CT&F Ciencia, Tecnologia y Futuro     Open Access  
Current Applied Physics     Full-text available via subscription   (Followers: 4)

  First | 1 2 3 4 5 6 7 8 | Last

Journal Cover AIChE Journal
  [SJR: 1.098]   [H-I: 104]   [24 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0001-1541 - ISSN (Online) 1547-5905
   Published by John Wiley and Sons Homepage  [1598 journals]
  • A Chemical Engineering Perspective on Nanoparticle‐based Targeted
           Drug Delivery: A Unit Process Approach
    • Authors: Aaron C. Anselmo; Samir Mitragotri
      PubDate: 2016-01-29T05:19:32.037737-05:
      DOI: 10.1002/aic.15189
       
  • A model to predict liquid bridge formation between wet particles based on
           direct numerical simulations
    • Authors: Mingqiu Wu; Johannes Khinast, Stefan Radl
      Abstract: We study dynamic liquid bridge formation, which is relevant for wet granular flows involving highly viscous liquids and short collisions. Specifically, the drainage process of liquid adhering to two identical, non‐porous wet particles with difference initial film heights is simulated using Direct Numerical Simulations (DNS). We extract the position of the interface, and define the liquid bridge and its volume by detecting a characteristic neck position. This allows us building a dynamic model for predicting bridge volume, and the liquid remaining on the particle surface. Our model is based on two dimensionless mobility parameters, as well as a dimensionless time scale to describe the filling process. In the present work model parameters were calibrated with DNS data. We find that the proposed model structure is sufficient to collapse all our simulation data, indicating that our model is general enough to describe liquid bridge formation between equally sized particles. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-29T02:37:03.301491-05:
      DOI: 10.1002/aic.15184
       
  • Electrically accelerated removal of organic pollutants by a
           three‐dimensional graphene aerogel
    • Abstract: Fast and effective methods for the removal of pollutants are crucial for the development of new sustainable water treatment technologies. In this work, we have reported the electrically accelerated removal of some typical organic pollutants by a three‐dimensional graphene aerogel (3DG). The porous 3DG was fabricated by chemical reduction of graphene oxide. The morphology and structure of 3DG were characterized by microscopic and spectroscopic approaches. The experiments indicated that 3DG‐based electrosorption could accelerate the removal of positively and negatively charged pollutants, such as Acid Red 88, Orange II and Methylene Blue, as well as enhance the maximum adsorption capacity towards these contaminants. The interaction mechanisms between these organic pollutants and 3DG surface were further elucidated by Dispersion corrected Density Functional Theory (DFT‐D) calculations. This 3DG‐based system offers a potentially effective method for the rapid removal of organic pollutants and provides a new sustainable approach for water and wastewater treatment. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-29T02:36:23.611872-05:
      DOI: 10.1002/aic.15185
       
  • Particle‐resolved direct numerical simulation of gas‐solid
           dynamics in experimental fluidized beds
    • Authors: Kun Luo; Junhua Tan, Zeli Wang, Jianren Fan
      Abstract: Particle‐resolved direct numerical simulations (PR‐DNS) of a simplified experimental shallow fluidized bed and a laboratory bubbling fluidized bed are performed by using immersed boundary method coupled with a soft‐sphere model. Detailed information on gas flow and individual particles' motion are obtained and analyzed to study the gas‐solid dynamics. For the shallow bed, the successful predictions of particle coherent oscillation and bed expansion and contraction indicate all scales of motion in the flow are well captured by the PD‐DNS. For the bubbling bed, the PR‐DNS predicted time averaged particle velocities show a better agreement with experimental measurements than those of the computational fluid dynamics coupled with discrete element models (CFD‐DEM), which further validates the predictive capability of the developed PR‐DNS. Analysis of the PR‐DNS drag force shows that the prevailing CFD‐DEM drag correlations underestimate the particle drag force in fluidized beds. The particle mobility effect on drag correlation needs further investigation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-29T02:35:51.331676-05:
      DOI: 10.1002/aic.15186
       
  • CFD‐DEM investigation into the scaling up of spout‐fluid beds
           via two inter‐connected chambers
    • Authors: Shiliang Yang; Yuhao Sun, Jingwei Wang, Andy Cahyadi, Jia Wei Chew
      Abstract: The hydrodynamics and chamber interaction in a three‐dimensional spout‐fluid bed with two inter‐connected chambers is investigated via CFD‐DEM (Computational Fluid Dynamics coupled with Discrete Element Method), because multiple inter‐connected chambers are key to scaling up spout‐fluid beds. The overall solid motion, spouting evolution and spout‐annulus interface is studied, followed by time‐averaged hydrodynamics, particle‐scale information, spout‐annulus interaction and inter‐chamber interaction. The results show that inter‐chamber interactions lead to unique characteristics distinct from that for a single‐chamber system, including (i) asymmetry of the hydrodynamics within each chamber, (ii) alternative spouting behavior in the two chambers, (iii) smaller pressure drop in terms of magnitude and fluctuations, (iv) two peaks in the solid residence time (SRT) frequency histogram of the annulus, (v) average SRT in the spout is twice that in a single‐chamber, and (vi) larger solid dispersion in all three directions. The results provide meaningful understanding for the scale‐up of spout‐fluid beds. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-29T02:35:18.244616-05:
      DOI: 10.1002/aic.15188
       
  • Coupled fluid‐particle modeling of a slot die coating system
    • Authors: V. Akbarzadeh; A. N. Hrymak
      Abstract: This work seeks to develop a fundamental understanding of particle motion in the slot die coating process through studying the interaction of forces between particles, with the die walls and the fluid phase. Coupled computational fluid dynamics and the discrete element method is employed for evaluating the motion of individual suspended particles near moving surfaces in a complex 3‐D flow field, motivated by the flow of particle laden fluid in a slot die coating system, including the presence of free surfaces. Overall, the particles follow the flow streamlines and their final position in the coating depends on the initial entry region of the particles. Particles experiencing adhesion with each other agglomerate in the low velocity regions of the coating gap, and have long residence times near the edge of the die at the end of the feed slot in the coating gap. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-29T02:34:42.951742-05:
      DOI: 10.1002/aic.15187
       
  • Characterisation of extensional rheological filament stretching with a
           dual‐mode Giesekus model
    • Authors: Bart Hallmark; Nicolas Pistre, D. Ian Wilson
      Abstract: A new, simple, formulation that describes capillary thinning as predicted by a two‐mode Giesekus model is derived, and its application in analysing data from extensional rheometry (capillary thinning) experiments is discussed. An algorithm is presented that can be used to fit the expressions obtained from the Giesekus model to extensional rheometry data. Examples of data fitting are given for an idealised data set, for measurements obtained for aqueous solutions of 6 wt% 900,000 molecular weight polyethylene oxide, and for biological fluids obtained from pitchers of Nepenthes Rafflesiana. Good fits to the data were obtained, with coefficients of determination in excess of 0.98. For each data set, it was possible to calculate values of extensional viscosity and relaxation time for each of the two modes, allowing quantitative comparison of different fluids or of the same fluid as it ages. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-28T18:25:39.900812-05:
      DOI: 10.1002/aic.15182
       
  • PtCu alloy nanotube arrays supported on carbon fiber cloth as flexible
           anodes for direct methanol fuel cell
    • Abstract: The rapid development of flexible and portable electrochemical energy devices has pro‐moted the demand for flexible and lightweight electrocatalysts. Here we report flexible high performance electrocatalysts based on PtCu alloy nanotube arrays on carbon fiber cloth (CFC) (PtCu ANTAs/CFC) for direct methanol fuel cell. Compared with Pt NTAs/CFC and commercial Pt/C, the PtCu ANTAs/CFC electrocatalysts exhibit significantly improved electrocatalytic activity and durability. Furthermore, the PtCu ANTAs/CFC electrocatalysts show excellent flexibility and it can keep almost constant electrocata‐lytic performance under the different distorted states, such as normal, bending and twisting states. The improved performance of the flexible PtCu ANTAs/CFC electrocatalysts can be ascribed to unique ANTAs, synergistic effect between Pt and Cu, and porous structure of CFC. This work shows the significant progress of high‐performance Pt‐based flexible anodes for direct methanol fuel cells. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-28T03:51:27.243325-05:
      DOI: 10.1002/aic.15178
       
  • Correction: A Mechanistic Growth Model for Inorganic Crystals: Growth
           Mechanism
    • Authors: Jinjin Li; Preshit Dandekar, Mark Joswiak, Michael F. Doherty
      PubDate: 2016-01-27T18:01:30.891432-05:
      DOI: 10.1002/aic.15180
       
  • Characterization of the liquid film flow in a centrifugal separator
    • Authors: H.E.M. Ninahuanca; H. Stel, C. Ofuchi, M.J. da Silva, F. Neves, R.E.M. Morales
      Abstract: This work presents the characterization of the flow in a centrifugal separator. The study is focused on the behavior of the liquid phase in this kind of equipment, so that only single‐phase liquid flow at the inlet of the separator is considered. The parameters investigated are the film thickness, the flow velocity components, the flow streamlines angles and the liquid level height above the inlet. These quantities were assessed for different flow rates using numerical simulations and experimental measurements. Results show that an increase on the inlet flow rate causes an increase on the liquid film thickness and the liquid level height. Also, the centrifugal movement is intensified when the flow rate increases. The numerical results proved to describe the overall flow behavior satisfactorily when compared to the experiments. From the outcomes of the present study, information can be extracted to understand the separation process in this type of separator. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-27T18:01:02.580638-05:
      DOI: 10.1002/aic.15181
       
  • Multi‐stage Adjustable Robust Optimization for Process Scheduling
           under Uncertainty
    • Authors: Nikos H. Lappas; Chrysanthos E. Gounaris
      Abstract: Variations in parameters such as processing times, yields, and availability of materials and utilities can have a detrimental effect in the optimality and/or feasibility of an otherwise “optimal” production schedule. In this paper, we propose a multi‐stage adjustable robust optimization approach to alleviate the risk from such operational uncertainties during scheduling decisions. We derive a novel robust counterpart of a deterministic scheduling model, and we show how to obey the observability and non‐anticipativity restrictions that are necessary for the resulting solution policy to be implementable in practice. We also develop decision‐dependent uncertainty sets in order to model the endogenous uncertainty that is inherently present in process scheduling applications. A computational study reveals that, given a chosen level of robustness, adjusting decisions to past parameter realizations leads to significant improvements, both in terms of worst‐case objective as well as objective in expectation, compared to the traditional robust scheduling approaches. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-27T18:00:36.007109-05:
      DOI: 10.1002/aic.15183
       
  • Subsystem Decomposition and Configuration for Distributed State Estimation
    • Authors: Xunyuan Yin; Kevin Arulmaran, Jinfeng Liu, Jing Zeng
      Abstract: Distributed state estimation plays a very important role in process control. Improper subsystem decomposition for distributed state estimation may increase the computational burdens, degrade the estimation performance or even deteriorate the observability of the entire system. In this work, we investigate the subsystem decomposition problem for distributed state estimation of nonlinear systems. A systematic procedure for subsystem decomposition for distributed state estimation is proposed. Key steps in the procedure include observability test of the entire system, observable states identification for each output measurement, relative degree analysis and sensitivity analysis between measured outputs and states. Considerations with respect to time‐scale multiplicity and direct graph are discussed. A few examples are used to illustrate the applicability of the methods used in different steps. The effectiveness of the entire distributed state estimation configuration procedure is also demonstrated via an application to a chemical process example used in coal handling and preparation plants. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-27T10:28:47.289718-05:
      DOI: 10.1002/aic.15170
       
  • Reversed Micelle Synergistic Extraction from Phosphonium Ionic Liquid
           Extractants in Diluent for Rare Earth
    • Authors: Yamin Dong; Xiaoqi Sun, Yujun Chai, Yanliang Wang
      Abstract: The first synergistic extraction between quaternary phosphonium type ionic liquid extractants in toluene for rare earth was reported in this article. There were two different ion‐association mechanisms in the synergistic extraction system. The formed reversed micelles contributed to increase extractability of the synergistic extraction system to a considerable extent. On the one hand, million tons of saponification wastewater from acidic extractants may be avoided by developing the extraction system using bifunctional ionic liquid extractants. On the other hand, the novel synergistic extraction offers an effective strategy to increase the extractabilities of industrial extractants. This paper reveals sustainable and efficient potentials for industrial rare earth separation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-25T11:29:16.911218-05:
      DOI: 10.1002/aic.15179
       
  • Study on rheology and thermal stability of mixed (nonionic‐anionic)
           surfactant based fracturing fluids
    • Authors: Atrayee Baruah; Akhilendra K. Pathak, Keka Ojha
      Abstract: Mixed surfactant systems have gained significant importance in the development of fracturing fluid due to polymorphism of self‐assembly structures that have combined properties of the surfactants in the mixture. In this paper, a comparative study on the phase behavior and viscoelastic properties of mixed surfactant based fluids, prepared from Tween 80+NaOA/2‐ethyl hexanol/clove oil/water and Tween 20+NaOA/2‐ethyl hexanol/clove oil/water quaternary system is investigated in details. The viscoelastic surfactant (VES) based fluids prepared from the former system offered superior rheological properties than the latter system. The addition of 0.1% NaOH and 500 ppm ZnO nano‐particles in the VES fluids presented enhanced viscoelastic properties as concluded by static and dynamic rheological tests. Miscibility test indicated the miscibility of the VES fluids with water, unlike in the presence of diesel oil and satisfactory proppant suspension capabilities were exhibited by the developed fluids. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-23T02:47:27.159642-05:
      DOI: 10.1002/aic.15175
       
  • Development of on‐line pyroprocessing for liquid thorium fueled
           reactors
    • Authors: Milan Stika; Devin Rappleye, Sang Mun Jeong, Michael F. Simpson
      Abstract: The electrochemical behavior of thorium and uranium in molten LiF was examined separately and simultaneously at 1173 K using cyclic voltammetry. Inert molybdenum wire served as a working electrode. A platinum wire served as a quasi‐reference electrode (QRE). The quality of voltammograms was highly dependent on the degree of dryness of the salt. The experimental results confirmed previous findings for similar salt matrices that thorium is reduced in a single, 4‐electron [Th(IV)/Th] step, whereas uranium is reduced in a two‐step process, including a 1‐electron exchange [U(IV)/U(III)] followed by a 3‐electron exchange [U(III)/U]. Diffusion coefficients for thorium and uranium were calculated and plotted as a function of concentration. Calibration curves of peak current density versus analyte concentration were developed. Separability of uranium from the thorium‐rich matrix was confirmed feasible. Satisfactory concentration monitoring of uranium was demonstrated, whereas thorium concentration monitoring in the ternary salt was found problematic. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-23T02:45:57.860993-05:
      DOI: 10.1002/aic.15177
       
  • Multi‐period planning, design and strategic models for
           long‐term, quality‐sensitive shale gas development
    • Authors: Markus G. Drouven; Ignacio E. Grossmann
      Abstract: In this work we address the long‐term, quality‐sensitive shale gas development problem. This problem involves planning, design and strategic decisions such as where, when and how many shale gas wells to drill, where to lay out gathering pipelines, as well as which delivery agreements to arrange. Our objective is to use computational models to identify the most profitable shale gas development strategies. For this purpose we propose a large‐scale, nonconvex, mixed‐integer nonlinear programming (MINLP) model. We rely on generalized disjunctive programming (GDP) to systematically derive the building blocks of this model. Based on a tailor‐designed solution strategy we identify near‐global solutions to the resulting large‐scale problems. Finally, we apply the proposed modeling framework to two case studies based on real data to quantify the value of optimization models for shale gas development. Our results suggest that the proposed models can increase upstream operators' profitability by several million U.S. dollars. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-23T02:43:13.60821-05:0
      DOI: 10.1002/aic.15174
       
  • Drying of a system of multiple solvents: Modeling by the reaction
           engineering approach (REA)
    • Authors: Aditya Putranto; Xiao Dong Chen
      Abstract: Drying is a very important industrial operation in society. In drying, solute may dissolve in an aqueous solvent, a non‐aqueous solvent or a mixture of solvents. Many mathematical models have been published previously to model drying of solute in water. The reaction engineering approach (REA) is known to be an easy‐to‐use approach. It can describe well many drying cases of water removal. Currently, no simple lumped model has been attempted to describe drying of porous materials containing a mixture of solvents. In this study, for the first time, REA is constructively implemented to model drying in a mixture of one aqueous and one non‐aqueous solvent. The REA is applied here to model the drying of polyvinyl alcohol (PVA)/methanol/water under constant and time‐varying environmental conditions. Similar to the relative activation energy of water, that of methanol is generated through one accurate drying run. For modeling the time‐varying drying, the relative activation energies are the same as those for modeling convective drying under constant ambient conditions but combined with the equilibrium activation energies at the corresponding humidity, methanol concentration and temperature for each drying period. The REA is accurate to model drying of a solute in non‐aqueous solvent as well as in a mixture of non‐interacting solvents. In the future, spatially distributed REA for non‐aqueous or mixtures of both aqueous and non‐aqueous solvent will be explored for fundamental understanding and for practical application. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-23T02:42:25.385468-05:
      DOI: 10.1002/aic.15176
       
  • Issue information
    • Abstract: Cover illustration. Hydrodynamic and oxygen concentration profile in hollow and porous electrocatalyst layer. Image courtesy: Arif A. Farhan. 10.1002/aic.15048
      PubDate: 2016-01-22T12:47:09.37952-05:0
      DOI: 10.1002/aic.14983
       
  • Actuator Stiction Compensation via Model Predictive Control for Nonlinear
           Processes
    • Authors: Helen Durand; Panagiotis D. Christofides
      Abstract: In this work, we address the problem of valve stiction, which is a nonlinear friction phenomenon that causes poor performance of control loops in the process industries. We develop an MPC stiction compensation formulation including detailed dynamics for a sticky valve and additional constraints on the input rate of change and actuation magnitude to reduce control loop performance degradation and to prevent the MPC from requesting physically unrealistic control actions due to stiction. Though developed with a focus on stiction, the MPC‐based compensation method presented is general and has potential to compensate for other nonlinear valve dynamics which have some similarities to those caused by stiction. Feasibility and closedloop stability of the proposed MPC formulation are proven for a sufficiently small sampling period when Lyapunov‐based constraints are incorporated. Using a chemical process example with an economic model predictive controller (EMPC), we demonstrate the selection of appropriate constraints for the proposed method and show that the incorporation of the stiction dynamics and actuation magnitude constraints in the EMPC causes it to select set‐points that the valve output can reach and that cause the operating constraints to be met. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-21T18:04:02.922258-05:
      DOI: 10.1002/aic.15171
       
  • Functional Unfold Principal Component Regression Methodology for Analysis
           of Industrial Batch Process Data
    • Abstract: This work proposes a methodology utilizing functional unfold principal component regression (FUPCR), for application to industrial batch process data as a process modelling and optimization tool. The methodology is applied to an industrial fermentation dataset, containing 30 batches of a production process operating at Novozymes A/S. Following the FUPCR methodology, the final product concentration could be predicted with an average prediction error of 7.4%. Multiple iterations of pre‐processing were applied by implementing the methodology in order to identify the best data handling methods for the model. It is shown that application of functional data analysis and the choice of variance scaling method have the greatest impact on the prediction accuracy. Considering the vast amount of batch process data continuously generated in industry, this methodology can potentially contribute as a tool to identify desirable process operating conditions from complex industrial datasets. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-21T18:03:35.968746-05:
      DOI: 10.1002/aic.15172
       
  • Aggregation Thermodynamics for Asphaltene Precipitation
    • Abstract: Asphaltene precipitation has been a major concern for petroleum industry due to its adverse effect upon upstream production, midstream transportation, and downstream refining. As a complex phenomenon involving solubility, aggregation, and clustering, asphaltene precipitation has been extensively investigated and correlated with empirical models and equations. Based on the insight regarding hierarchical structure of asphaltenes recently elucidated by Mullins, we present a thermodynamic formulation for asphaltene aggregation, the onset of asphaltene precipitation. The thermodynamic formulation accounts for asphaltene aggregation driving force as a two‐step process: 1) molecular asphaltene forming imaginary” nanocrystals,” and 2) “nanocrystals” re‐dissolving as colloidal nanoaggregates. Applying UNIFAC with this thermodynamic formulation, we show semi‐quantitative predictions of asphaltene precipitation in 13 binary solvents with wide varieties of chemical structures and solvent combination. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-21T18:02:51.740364-05:
      DOI: 10.1002/aic.15173
       
  • Integrated gasoline blending and order delivery operations: Part I.
           Short‐term scheduling and global optimization for single and
           multi‐period operations
    • Authors: Jie Li; Xin Xiao, Christodoulos A. Floudas
      Abstract: Gasoline is one of the most valuable products in an oil refinery and can account for as much as 60‐70% of total profit. Optimal integrated scheduling of gasoline blending and order delivery operations can significantly increase profit by avoiding ship demurrage, improving customer satisfaction, minimizing quality give‐aways, reducing costly transitions and slop generation, exploiting low‐quality cuts, and reducing inventory costs. In this paper, we first introduce a new unit‐specific event‐based continuous‐time formulation for the integrated treatment of recipes, blending, and scheduling of gasoline blending and order delivery operations. Many operational features are included such as non‐identical parallel blenders, constant blending rate, minimum blend length and amount, blender transition times, multi‐purpose product tanks, changeovers, and piecewise constant profiles for blend component qualities and feed rates. To address the non‐convexities arising from forcing constant blending rates during a run, we propose a hybrid global optimization approach incorporating a schedule adjustment procedure, iteratively via a MIP and NLP scheme, and a rigorous deterministic global optimization approach. The computational results demonstrate that our proposed formulation does improve the MILP relaxation of Li and Karimi, Ind. Eng. Chem. Res., 2011, 50, 9156‐9174. All examples are solved to be 1%‐ global optimality with modest computational effort. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-19T18:44:20.893338-05:
      DOI: 10.1002/aic.15168
       
  • An elastic analog model for controlling the impingement point position in
           confined impinging jets
    • Abstract: Confined impinging jets, CIJs, are highly efficient mixers. The scales of mixing in CIJs are controlled by the opposed jets interaction. A mechanistic model is described here, which accurately predicts the impinging position of the opposed jets for a large range of flow rate ratios. The impinging point position is shown to impact the dynamic properties of the flow and the achieved mixing quality. The opposed jets kinetic energy ratio is shown to have a critical impact on mixing, similar to the Reynolds number. A mixing chamber design relation is proposed and verified for the opposed injectors diameters ratio, d1/ d2, which enables to operate CIJs under optimum mixing conditions for large ranges of flow rate ratios, viscosity and density ratios between the opposed streams. Optimum d1/d2 values have asymptotes for large and small Reynolds number depending on the process stoichiometry, viscosity and density ratios of the opposed jet streams. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-19T18:23:38.049407-05:
      DOI: 10.1002/aic.15169
       
  • Optimal reuse of flowback wastewater in hydraulic fracturing including
           seasonal and environmental constraints
    • Abstract: This paper presents a mathematical programing formulation for the optimal management of flowback water in shale gas wells. The formulation accounts for the time‐based generation of the flowback water, the options for treatment, storage, reuse, and disposal. The economic and environmental objectives are considered. The economic objective function is aimed at determining the minimum cost for the fresh water, treatment, storage, disposals and transportation. The environmental objectives account for the fresh water usage and wastewater discharge. To carry out the water integration, a reuse network including treatment is proposed. Additionally, the model considers seasonal fluctuations in the fresh water availability. A given scheduling for the completion phases of the wells is required to implement the methodology. Finally, an example problem is presented to show the applicability of the proposed methodology. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-13T03:50:56.352402-05:
      DOI: 10.1002/aic.15167
       
  • Conversion of Isopropanol and Mixed Alcohols to Hydrocarbons Using
           HZSM‐5 Catalyst in the MixAlco™ Process Part 2: Studies at
           5000 kPa (abs)
    • Abstract: This study employed HZSM‐5 (SiO2/Al2O3 = 280 mol/mol) to produce hydrocarbons from reagent‐grade isopropanol and mixed alcohols made from lignocellulosic biomass (waste office paper and chicken manure) using the MixAlco™ process. All studies were performed at P = 5000 kPa (abs). The experiments were conducted in two sets: (1) vary temperature (300–450°C) at weight hourly space velocity (WHSV) = 1.92 h−1, and (2) vary WHSV (1.92–11.52 h−1) at T = 370°C. For isopropanol at higher temperatures, the olefins undergo more cracking reactions to produce smaller molecules and more aromatics. At low temperatures, the molecules have less energy so they do not crack and therefore form larger molecules. At T = 300°C, the carbon distribution is bimodal at C9 and C12, which shows trimerization and tetramerization of propene. At 300°C, propene was the only gas produced, cracking did not occur and therefore preserved high‐molecular‐weight molecules. For mixed alcohols, higher temperatures show significant catalyst deactivation; however, isopropanol did not show any catalyst deactivation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-11T17:50:14.072972-05:
      DOI: 10.1002/aic.15166
       
  • Ultrasonically Enhanced Bulk ATRP of Methyl Methacrylate at High
           Conversion with Good Livingness and Control
    • Authors: Ali Mohammad Rabea; Shiping Zhu
      Abstract: A great challenge in controlled radical polymerization (CRP) such as atom transfer radical polymerization (ATRP) has been related to keep the livingness and molecular weight control of the reaction at high conversion, especially in bulk polymerization. The objective of this work is to investigate the effects of ultrasound power on the polymerization at high conversion. The initiator for continuous activator regeneration (ICAR) ATRP is used for bulk polymerization of methyl methacrylate (MMA) as the model system. Good livingness and control up to high conversion are obtained through employing ultrasonic waves. By this method, MMA is polymerized in bulk up to “glass state” (88%) at 70°C with polydispersity about 1.2 under an operating frequency of 40 kHz and output power of 100 W. Chain extension reaction proves the livingness of the synthesized polymers at glassy state. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-11T17:49:45.96302-05:0
      DOI: 10.1002/aic.15165
       
  • Dynamic modeling and collocation‐based model reduction of cryogenic
           air separation units
    • Abstract: High purity distillation columns and multi‐stream heat exchangers are critical units in cryogenic air separation plants. This article focuses on modeling approaches for the primary section of a super‐staged argon plant. A full‐order stage‐wise model (FOSM) for distillation columns in air separation units (ASUs) that considers key process phenomena is presented, followed by a reduced‐order model using a collocation approach. The extent of model reduction that can be achieved without losing significant prediction accuracy is demonstrated. A novel moving boundary model is proposed to handle multi‐stream heat exchangers with phase change. Simulation results demonstrate the capability of the proposed model for tracking the phase change occurrence along the length of the heat exchanger. Dynamic simulation studies of the integrated plant show that the thermal integration between the feed and product streams captured in the primary heat exchanger is critical to accurately capture the behavior of ASUs. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-11T03:22:02.999873-05:
      DOI: 10.1002/aic.15164
       
  • The Selectivity for Sulfur Removal from Oils: An Insight from Conceptual
           Density Functional Theory
    • Authors: Hongping Li; Yonghui Chang, Wenshuai Zhu, Siwen Zhu, Wei Jiang, Ming Zhang, Yuwei Zhou, Jiexiang Xia, Huaming Li
      Abstract: The selectivity for sulfur removal from oils is an important topic. In the present work, the selectivity for different sulfur removal methods has been studied by conceptual density functional theory (CDFT) at the B3LYP/6‐311++G(3df,2p) level of theory. In principle, the selectivity is directly related to the mechanisms of sulfur removal. It cannot be precisely elucidated until the mechanisms are totally known. However, current work shows that relationships can be constructed between CDFT and the selectivity. That is, for hydrodesulfurization, good descriptors will be ionization energy, hardness, and bond lengths of S‐C; for adsorptive desulfurization, the hardness is a good descriptor; for oxidative desulfurization, good descriptors are electron density and Fukui function. And for extractive desulfurization (non‐metal‐based ionic liquids), electron affinity and electrophilicity may be good descriptors. In addition, structures and frontier orbitals of various sulfides have also been discussed. It is hoped that these relationships between CDFT and selectivity can give useful information to develop highly efficient sulfur removal methods for specific sulfides, like 4,6‐dimethyldibenzothiophene, and 4‐methyldibenzothiophene. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-09T04:03:39.906019-05:
      DOI: 10.1002/aic.15161
       
  • Kinetic Modeling of 1,2‐Dichloropropane (PDC) Free‐Radical
           Chlorination
    • Authors: Hangyao Wang; Max Tirtowidjojo, Christina Zarth, David Laitar
      Abstract: Recent government mandates have lowered the permissible global warming potential (GWP) for refrigerants in mobile air conditioning substantially below that of the hydrofluorocarbon (HFC) products that are used currently. Potential replacements, hydrofluoro‐olefins (HFO), have a reduced impact on the ozone layer and lower GWP. Many desirable HFO compounds, such as HFO‐1234yf, can be produced utilizing chlorocarbons as feedstocks such as the preferred 1,1,2,3‐tetrachloropropene (TCPE). TCPE can be produced by several routes; however, producing TCPE from 1,2‐dichloropropane (PDC) is potentially more desirable environmentally and economically since PDC is a byproduct of propylene oxide (PO) and allyl chloride production. One process option is to convert PDC to pentachloropropane (PCP) intermediates by chlorination, followed by dehydrochlorination of the PCPs to produce TCPE. In this work, we show that PCPs can be produced through the chlorination of PDC in a free‐radical liquid phase reaction and have developed a kinetic model for PDC chlorination based on the relevant free radical elementary reactions. Thermodynamic properties including standard heats of formation, standard entropies of formation and heat capacities for the radical and non‐radical species were estimated by using ab initio and COSMOtherm calculations and validated against available experimental data. The reaction equilibrium constants were determined from the Gibb's free energies of the reactants and products. Phase equilibria were calculated by means of a consistent set of thermodynamic properties of the species. In addition, physical properties such as the vapor pressure of pure components involved in the reaction network were also estimated. Ab initio transition state calculations were employed to estimate the rate parameters including pre‐exponential factors and activation energies for the relevant reactions. The activation energies of some key reactions were then adjusted to match experimental data. The resulting kinetic model provided a basis for process yield optimization and scale up. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-09T04:03:02.200596-05:
      DOI: 10.1002/aic.15163
       
  • A numerical study exploring the effect of particle properties on the
           fluidization of adhesive particles
    • Authors: Robert Wilson; Daniele Dini, Berend van Wachem
      Abstract: The effects of varying the elastic modulus, coefficient of restitution, and coefficient of friction of adhesive particles on fluidized bed dynamics have been investigated via numerical simulations. It is found that lower values of the elastic modulus and coefficient of restitution lead to a greater degree of particle clustering, and the formation of smaller bubbles. Coordination numbers are found to initially increase, and then fall, with increasing coefficient of friction, while bubble velocities follow the opposite trend. It is concluded that artificially reducing the elastic modulus of adhesive particles has a significant impact on the fluidization behaviour. The change in dynamics of the fluidized bed due to varying the coefficient of friction is more complex: particle clustering increases up to a point, beyond which clusters become increasingly rigid. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-08T19:12:56.953562-05:
      DOI: 10.1002/aic.15162
       
  • (nBuCp)2ZrCl2‐catalyzed Ethylene‐4M1P Copolymerization:
           Copolymer Backbone Structure, Melt Behavior, and Crystallization
    • Abstract: The judicious design of methylaluminoxane (MAO) anions expands the scope for developing industrial metallocene catalysts. Therefore, the effects of MAO anion design on the backbone structure, melt behavior, and crystallization of ethylene−4‐methyl‐1‐pentene (E−4M1P) copolymer were investigated. Ethylene was homopolymerized, as well as copolymerized with 4M1P, using (i) MAO anion A (unsupported [MAOCl2]−) premixed with dehydroxylated silica, (nBuCp)2ZrCl2, and Me2SiCl2; and (ii) MAO anion B (Si−O−Me2Si−[MAOCl2]−) supported with (nBuCp)2ZrCl2 on Me2SiCl2‐functionalized silica. Unsupported Me2SiCl2, opposite to the supported analogue, acted as a co‐chain transfer agent with 4M1P. The modeling of polyethylene melting and crystallization kinetics, including critical crystallite stability, produced insightful results. This study especially illustrates how branched polyethylene can be prepared from ethylene alone using particularly one metallocene‐MAO ion pair, and how a compound, that functionalizes silica as well as terminates the chain, can synthesize ethylene−α‐olefin copolymers with novel structures. Hence, it unfolds prospective future research niches in polyethyne systhesis. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-08T10:29:27.119107-05:
      DOI: 10.1002/aic.15159
       
  • Predicting Effective Conductivities Based on Geometric Microstructure
           Characteristics
    • Authors: Ole Stenzel; Omar Pecho, Lorenz Holzer, Matthias Neumann, Volker Schmidt
      Abstract: Empirical relationships between effective conductivities in porous and composite materials and their geometric characteristics such as volume fraction ε, tortuosity τ and constrictivity β are established. For this purpose, 43 virtually generated 3D microstructures with varying geometric characteristics are considered. Effective conductivities σeff are determined by numerical transport simulations. Using error‐minimization the following relationships have been established: and (simplified formula) with intrinsic conductivity σ0, geodesic tortuosity τgeod and relative prediction errors of 19% and 18%, respectively. We critically analyze the methodologies used to determine tortuosity and constrictivity. Comparing geometric tortuosity and geodesic tortuosity, our results indicate that geometric tortuosity has a tendency to overestimate the windedness of transport paths. Analyzing various definitions of constrictivity, we find that the established definition describes the effect of bottlenecks well. In summary, the established relationships are important for a purposeful optimization of materials with specific transport properties, such as porous electrodes in fuel cells and batteries. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-08T10:29:00.288289-05:
      DOI: 10.1002/aic.15160
       
  • Realization and Control of Multiple Temperature Zones in
           Liquid‐containing Gas‐solid Fluidized Bed Reactor
    • Authors: Yefeng Zhou; Qiang Shi, Zhengliang Huang, Zuwei Liao, Jingdai Wang, Yongrong Yang
      Abstract: Fluidized bed reactors (FBRs) have been developed to establish multiple temperature zones for various industrial processes. In order to overcome the common weakness, this work proposed to spray liquid into bottom and upper zones respectively, to realize multiple temperature zones FBR (MTZFBR). Temperature, pressure and acoustic emission techniques were applied to fully characterize liquid interaction and hydrodynamics. Compared with the bottom liquid‐spraying approach, the upper liquid‐spraying approach showed higher temperature difference (ΔT) and better fluidization stability, thus was selected for further control studies. Effects of liquid flow‐rate, static bed height and inlet gas temperature on MTZFBR were studied systematically. The results showed that increasing liquid evaporation behavior or decreasing liquid bridge behavior enhance ΔT and fluidization stability and vice versa. G‐L‐S fluidization pattern depended mostly on the liquid behaviors and fluidization stability, and thus the stabilized MTZFBR could be regarded as a coexisted mode of two distinctive G‐L‐S fluidization patterns. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-08T04:44:35.898562-05:
      DOI: 10.1002/aic.15157
       
  • Teflon AF2400/Ultem composite hollow fiber membranes for alcohol
           dehydration by high‐temperature vapor permeation
    • Abstract: High‐temperature vapor permeation has a stringent requirement of membrane stability under harsh feed environments. This work reports the design of Teflon AF2400/Ultem composite hollow fiber (HF) membranes for alcohol dehydration via vapor permeation. Fabrication parameters such as Teflon concentration and coating time were systematically investigated. Interestingly, the fabricated composite HF membranes possess an unusual surface with honeycomb‐like microstructure patterns. Owing to the Teflon protective layer, the newly developed composite HF shows a promising and stable separation performance with a flux of 4265 gm−2h−1 and a separation factor of 383 for 95% isopropanol dehydration at 125 oC. The composite HF also performs well under extreme vapor feed compositions from 87 to 99 wt% isopropanol. In addition, it exhibits impressive separation performance for the dehydration of ethanol and n‐butanol. This work may provide useful insights of designing thermal‐stable and high‐performance composite polymeric membranes for vapor permeation. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-08T04:43:51.234557-05:
      DOI: 10.1002/aic.15158
       
  • Modeling, Optimization and Cost Analysis of an IGCC Plant with a Membrane
           Reactor for Carbon Capture
    • Authors: Fernando V. Lima; Prodromos Daoutidis, Michael Tsapatsis
      Abstract: This paper presents a theoretical study on the integration of a membrane reactor (MR) for carbon capture into an integrated gasification combined cycle (IGCC) plant. First‐principles, simplified systems‐level models for the individual IGCC units and the MR are introduced for their subsequent plantwide integration. The integrated plant model is then used for simulation studies that assume different MR characteristics. Using this model, an optimization problem is formulated to analyze the MR effects when adding it to the IGCC plant, while satisfying all of the process constraints in streams and performance variables. The solution of this optimization problem indicates improvements in the original case studies, including capital cost savings as high as $18 million for the optimal case under nominal process conditions. To determine the cost implications of inserting the MR into the IGCC plant, a differential cost analysis is performed taking into account major plant capital and operating costs. This analysis considers the same amount of coal and power generation for cases with and without the MR. The results of this analysis based on a present value of annuity calculation show break even costs for the MR within the feasible range for membrane fabrication, even for short membrane lifetimes. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-06T18:18:17.910621-05:
      DOI: 10.1002/aic.15153
       
  • Effect of Confinement on the Bubble Points of Hydrocarbons in Nanoporous
           Media
    • Authors: Sheng Luo; Jodie L. Lutkenhaus, Hadi Nasrabadi
      Abstract: The bubble point of reservoir petroleum fluids in nanoporous media is an important parameter in shale oil production. We present experimental results on the bubble points of octane and decane confined in controlled‐pore glasses (CPGs) with pore sizes of 4.3 and 38.1 nm. Differential scanning calorimetry (DSC) is used to measure the temperature at which the vapor phase begins to form (i.e. the bubble point). We find that the bubble point is dramatically affected by pore diameter: at 38.1 nm the confinement effect is insignificant, but at 4.3 nm two distinct bubble points appear, suggesting two distinct populations of evaporating fluid. Deviations are as great as +/‐15 K for both peaks relative to the bulk bubble point for 4.3 nm CPGs. Thermogravimetric analysis (TGA) is consistent with DSC, supporting the validity of these results. Based on these experiments and previous simulations, we propose a two‐state model for the nanoconfined hydrocarbons. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-06T18:00:00.463578-05:
      DOI: 10.1002/aic.15154
       
  • Efficient adsorptive desulfurization by task‐specific porous organic
           polymers
    • Abstract: A task‐specific mesoporous organic polymer (TSPOP) with unique features like good porosity and rich aromatic phenyl groups was facilely made and utilized as a promising adsorptive desulfurization (ADS) absorbent for the first time. The material exhibits an efficient saturated adsorption of dibenzothiophene (DBT), as high as 111.1 mg g−1. In addition, the intrinsic mesoporous skeleton of TSPOP gave rise to a facile incorporation of uniform Ag(I) species inside the network which facilitated the uptake of organosulfur compounds. A significantly higher saturated DBT adsorption for Ag(I)‐loaded TSPOP [Ag(I)‐TSPOP] reaches 203.7 mg g−1 via a multiple‐site interaction. A detailed model study based on the density functional calculation provides a deeper understanding of the origin of this high activity. In addition to the π‐π stacking between DBT and phenyl rings, there exists an additional π‐complexation adsorption with Ag(I) ions, thus, significantly improving the DBT capture performance. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-06T17:59:30.766066-05:
      DOI: 10.1002/aic.15156
       
  • Subspace identification for data‐driven modeling and quality control
           of batch processes
    • Authors: Brandon Corbett; Prashant Mhaskar
      Abstract: In this work we present a novel, data‐driven, quality modeling and control approach for batch processes. Specifically, we adapt subspace identification methods for use with batch data to identify a state‐space model from available process measurements and input moves. We demonstrate that the resulting LTI, dynamic, state‐space model is able to describe the transient behavior of finite duration batch processes. Next, we relate the terminal quality to the terminal value of the identified states. Finally, we apply the resulting model in a shrinking‐horizon, model predictive control scheme to directly control terminal product quality. The theoretical properties of the proposed approach are studied and compared to state‐of‐the‐art latent variable control approaches. The efficacy of the proposed approach is demonstrated through a simulation study of a batch polymethyl methacrylate (PMMA) polymerization reactor. Results for both disturbance rejection and set‐point changes (that is, new quality grades) are demonstrated. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-06T17:59:02.052425-05:
      DOI: 10.1002/aic.15155
       
  • Multi‐Scale Systems Engineering for Energy and the Environment:
           Challenges and Opportunities
    • Authors: Christodoulos A. Floudas; Alexander M. Niziolek, Onur Onel, Logan R. Matthews
      PubDate: 2016-01-05T11:10:13.722218-05:
      DOI: 10.1002/aic.15151
       
  • Model‐Predictive Safety System for Proactive Detection of Operation
           Hazards
    • Authors: Taha Mohseni Ahooyi; Jeffrey E. Arbogast, Warren D. Seider, Ulku G. Oktem, Masoud Soroush
      Abstract: This paper presents a method of designing model‐predictive safety systems that can detect operation hazards proactively. Such a proactive safety system has two major components: a set of operability constraints and a robust state estimator. The safety system triggers alarm(s) in real time when the process is unable to satisfy an operability constraint over a receding time‐horizon into the future. In other words, the system uses a process model to project the process operability status and to generate alarm signals indicating the presence of a present or future operation hazard. Unlike typical existing safety systems, it systematically accounts for nonlinearities and interactions among process variables to generate alarm signals; it provides alarm signals tied to un‐measurable, but detectable, state variables; and it generates alarm signals before an actual operation hazard occurs. The application and performance of the method are shown using a polymerization reactor example. This article is protected by copyright. All rights reserved.
      PubDate: 2016-01-05T11:09:22.081091-05:
      DOI: 10.1002/aic.15152
       
  • Issue information ‐ table of contents
    • Pages: 349 - 349
      PubDate: 2016-01-22T12:47:05.552425-05:
      DOI: 10.1002/aic.14982
       
  • Flow field during eccentric discharge from quasi‐two dimensional
           silos –extension of the kinematic model with validation
    • Authors: Ritwik Maiti; Sanjay Meena, Gargi Das, Prasanta Kumar Das
      Abstract: A comprehensive investigation of granular discharge through the eccentric opening of rectangular silos has been presented. Slip flow of the grains over the vertical wall closer to the orifice was observed experimentally. This has not been emphasized by the earlier researchers. Considering slip flow at the wall, the kinematic model of granular discharge has been extended to simulate the hydrodynamics during drainage through any eccentric opening. The simulation is applicable over the entire range of eccentricity possible and for both the uniform and the triangular velocity profile through the orifice. Results from the experiments using sand grains (300‐500 μm) and glass beads (400‐600 μm) have been used for validating the model. The excellent agreement not only justifies the application of the kinematic model for eccentric discharge, it also extends the model for irregular and much smaller grain size. Finally, some limitations of the kinematic model have been examined critically. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-31T10:43:04.678577-05:
      DOI: 10.1002/aic.15149
       
  • An Elucidation for the Central Stress Minimum in Granular Piles Using the
           Smoothed Particle Hydrodynamics
    • Authors: Shinichi Yuu; Toshihiko Umekage
      Abstract: Stress distributions on bases of granular piles were predicted based on the constitutive relations obtained by the DEM using the Smoothed Particle Hydrodynamics to elucidate the mechanism of the central stress minimum beneath piles. The calculated stress distributions are in good agreement with the experimental data of many researchers. A stress peak and a central stress minimum are mainly formed by the granular flows in a pile construction. The location of the stress peak was the same location of the minimum granular velocity before the granular pile became stationary. This suggests that the location of the stress peak corresponds to the base of the granular arching. The stresses distributions on the bases by a homogeneous falling showed the central stress maximum. The low shear stress gradient by the homogeneous falling produces a central stress peak with a gentle slope. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-31T10:42:15.323632-05:
      DOI: 10.1002/aic.15148
       
  • Particles mixing induced by bubbles in a gas‐solid fluidized bed
    • Authors: Zahra Amiri; Salman Movahedirad, Mansour Shirvani
      Abstract: The effect of bubble injection characteristics on the mixing behavior of a gas‐solid fluidized bed is investigated using a discrete particle model. The effect of different parameters including gas injection time, velocity, and mode are studied. Simulation results show that injecting gas at a constant gas flow rate in the form of small bubbles results in a better overall particle mixing. It was also found that the injection velocities have limited effect on particle mixing behavior for the same total gas volume injected into the bed. Moreover, the mixing index of continuous gas jet bubbling regime is compared with the mixing index obtained in uniform gas injection regime and the results revealed that the mixing index of continuous jet bubbling regime has a larger value than that of uniform gas injection regime at the fixed total gas flow rate. In both regimes, z‐direction mixing index is larger than x‐direction index. The differences between two direction indices are more noticeable in continuous jet bubbling in comparison with the uniform gas injection regime. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-31T10:41:26.811463-05:
      DOI: 10.1002/aic.15150
       
  • Characterization of Products from Fast and Isothermal Hydrothermal
           Liquefaction of Microalgae
    • Authors: Julia L. Faeth; Jacqueline M. Jarvis, Amy M. McKenna, Phillip E. Savage
      Abstract: We investigated non‐isothermal (fast) and nominally isothermal hydrothermal liquefaction (HTL) of Nannochloropsis sp. microalgae for the production of biocrude. Biocrude yields ranged from 36 wt % to 45 wt % (dry weight), with fast HTL with low mass loading giving the highest yield. This condition also gave the biocrude with the lowest heating value, which indicates there are compromises to be made between biocrude quantity and quality. The aqueous phase and biocrude product fractions were characterized using elemental analysis and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT‐ICR MS). This detailed level of analysis identified more than 30,000 unique molecular products. The aqueous phase products included compounds with the same molecular formulae as known herbicides, which may inform efforts in genetic engineering of algae and/or bacteria for cultivation on the aqueous phase. This detailed molecular‐level characterization provides some clues regarding the types of reactions that may take place during HTL. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-30T20:12:57.794867-05:
      DOI: 10.1002/aic.15147
       
  • Mixture design using derivative‐free optimization in the space of
           individual component properties
    • Authors: Nick D. Austin; Apurva P. Samudra, Nikolaos V. Sahinidis, Daniel W. Trahan
      Abstract: In this work, we propose a new methodology for mixture design. By projecting the problem on the space of individual component properties, the methodology exploits a natural problem decomposition and capitalizes on fast methods for pure compound design and mixture fraction design. We demonstrate the proposed methodology through application to two illustrative examples and then to two problems from the mixture design literature concerning the purification of ibuprofen. In all cases, the proposed approach finds optimal solutions while exploring a small number of feasible molecular structures. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-26T09:36:35.020875-05:
      DOI: 10.1002/aic.15142
       
  • Simulation, model‐reduction and state estimation of a
           two‐component coagulation process
    • Authors: Negar Hashemian; Antonios Armaou
      Abstract: We address the issue of state estimation of an aggregation process through (i) using model reduction to obtain a tractable approximation of the governing dynamics, and (ii) designing a fast moving‐horizon estimator for the reduced‐order model. We first use the method of moments to reduce the governing integro‐differential equation down to a nonlinear ordinary differential equation (ODE). This reduced‐order model is then simulated for both batch and continuous processes and the results are shown to agree with constant Number Monte Carlo (cNMC) simulation results of the original model. Next, the states of the reduced order model are estimated in a Moving Horizon Estimation (MHE) approach. For this purpose we first employ Carleman linearization and represent the nonlinear system in a bilinear form. This representation lessens the computation burden of the estimation problem by allowing for analytical solution of the state variables as well as sensitivities with respect to decision variables. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-24T18:30:15.579415-05:
      DOI: 10.1002/aic.15146
       
  • A new differential pressure flow meter for measurement of human breath
           flow: Simulation and experimental investigation
    • Authors: Devon Bridgeman; Francis Tsow, Xiaojun Xian, Erica Forzani
      Abstract: This paper presents the development and performance characterization of a new differential pressure‐based flow meter for human breath measurements. The device, called a “Confined Pitot Tube”, is comprised of a pipe with an elliptically‐shaped expansion cavity located in the pipe center, and an elliptical disk inside the expansion cavity. The elliptical disk, named Pitot Tube, is exchangeable, and has different diameters, which are smaller than the diameter of the elliptical cavity. The gap between the disk and the cavity allows the flow of human breath to pass through. The disk causes an obstruction in the flow inside the pipe, but the elliptical cavity provides an expansion for the flow to circulate around the disk, decreasing the overall flow resistance. We characterize the new sensor flow experimentally and theoretically, using Comsol Multiphysics® software with laminar and turbulent models. We also validate the sensor, using inhalation and exhalation tests and a reference method. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-23T18:44:02.025396-05:
      DOI: 10.1002/aic.15143
       
  • Production of benzene, toluene, and xylenes from natural gas via methanol:
           Process synthesis and global optimization
    • Authors: Alexander M. Niziolek; Onur Onel, Christodoulos A. Floudas
      Abstract: A systematic global optimization based process synthesis framework is presented to determine the most profitable processes to produce aromatics from natural gas. Several novel, commercial, and/or competing technologies are modeled within the framework, including methanol‐to‐aromatics, toluene alkylation with methanol, selective toluene disproportionation, and toluene disproportionation and transalkylation with heavy aromatics, among others. We propose a stand‐alone chemicals facility: the main products are aromatics with allowable by‐products of gasoline, liquefied petroleum gas, and electricity. Several case studies are discussed that produce varying ratios of para‐, ortho‐, and meta‐xylene across multiple refinery capacities. The results indicate that utilizing natural gas for the production of aromatics is profitable with net present values as high as $3800 MM dollars and payback periods as low as 6 years. The required investment for these refineries represents as much as a 65% decrease compared to published estimates of similar coal‐based capacity plants. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-23T18:43:36.220037-05:
      DOI: 10.1002/aic.15144
       
  • Towards efficient water/oil separation material: Effect of copolymer
           
    • Abstract: Interest in functional soft matter with stimuli‐responsive wettability has increasingly intensified in recent years. From the chemical product engineering viewpoint, this study aims to fabricate reversible pH‐responsive polymeric surfaces with controllable wettability using [poly(2,2,3,4,4,4‐hexafluorobutyl methacrylate)‐block‐ poly(acrylic acid) (PHFBMA‐b‐PAA)] block copolymers. To attain this aim, three block copolymers with different PAA segment lengths were synthesized for the first time through Cu(0)‐mediated reversible‐deactivation radical polymerization and hydrolysis reaction. pH‐induced controllable wettability was achieved by spin‐coating the resulting block copolymers onto silicon wafers. Results showed that the pH‐responsive wetting behavior was introduced by incorporating the PAA block, and that the responsiveness of as‐fabricated surfaces was greatly influenced by PAA content. All three evolutions of water contact angle with pH shared a similar inflection point at pH 5.25. Furthermore, on the basis of the wetting properties and mechanism understanding, the application of copolymer coated meshes in layered water/oil separation was exploited. Given their superhydrophilicity and underwater superoleophobicity, PHFBMA70‐b‐PAA148 and PHFBMA70‐b‐PAA211 coated stain steel meshes (SSMs) can efficiently separate water from different mixtures of organic solvent and water with high flux. However, considering long‐term use, the PHFBMA70‐b‐PAA148 coated SSM with good stability may be the best copolymer for water/oil separation. Therefore, a coordination of structure, composition, and functionality was necessary to enable practical applications of the functional materials. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-23T18:43:09.084774-05:
      DOI: 10.1002/aic.15145
       
  • Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for
           ethanol dehydration via pervaporation
    • Authors: Hao Zhang; Yan Wang
      Abstract: In this work, ethanediamine (EDA)‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH2) is synthesized and incorporated in the polyvinylalcohol (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH2 mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH2 MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH2 loading in the MMMs is studied and the MMM with a 7.5 wt% ZIF‐8‐NH2 loading shows the best pervaporation performance for ethanol dehydration at 40 oC. Various characterization techniques (FTIR, SEM, contact angle, sorption test, etc) are employed to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH2 particles. The impact of operation conditions on pervaporation performance is also carried out. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-22T19:29:21.405803-05:
      DOI: 10.1002/aic.15140
       
  • Advanced fundamental modeling of the kinetics of fischer‐tropsch
           synthesis
    • Authors: Liping Zhou; Gilbert F. Froment, Yong Yang, Yongwang Li
      Abstract: The paper reports on the kinetic modeling of Fischer‐Tropsch Synthesis on an iron catalyst starting from experimental data collected in a spinning basket reactor and proceeding through the Single Event approach to limit the number of independent parameters. The elementary steps are based on the carbide mechanism with hydrogen assisted CO insertion and CH2 as the growth monomer. The evolution with the chain length of alkane‐, alkene‐ and alcohol‐selectivities in the synthesis product and their exponential‐like behavior is fundamentally generated by accounting for the effect of the structure of reactants and transition state intermediates on the rate coefficients. The olefin readsorption is included in the model but its influence on the product distribution is found to be negligible. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-22T19:27:59.735252-05:
      DOI: 10.1002/aic.15141
       
  • Group Additive Kinetic Modeling for Carbon‐centered Radical Addition
           to Oxygenates and β‐Scission of Oxygenates
    • Abstract: A consistent set of 32 group additive values is determined for the Arrhenius parameters of carbon‐centered radical addition to oxygenates and the reverse β‐scission of oxygenate compounds, covering a wide temperature range (300‐2500 K). These values are derived based on a training set of 66 reactions for which the Arrhenius parameters are calculated using the CBS‐QB3 method in the high‐pressure limit, including corrections for hindered internal rotation. The accuracy of the model is established by comparing model predictions with an ab initio validation set containing 24 reactions. The mean factor of deviation between the group additively calculated and the ab initio rate coefficients is 3, for both radical additions and β‐scissions. Therefore, the developed group additive model, constituting an extension of the existing model for carbon‐centered radical additions and β‐scissions of hydrocarbons, can be safely applied for an accurate prediction of kinetics of the corresponding reactions involving oxygenate compounds. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-22T19:23:52.193028-05:
      DOI: 10.1002/aic.15139
       
  • Fluid Flow through Compressible Soft Particle Beds
    • Abstract: The fluid flow through a soft particle bed was studied theoretically and experimentally in this report. Several correction factors were introduced to modify the Ergun equation and account for the deformed shape and reduced volume of compressed particles in a compressible soft particle bed. To acquire the correction factors, both uni‐compression tests and computational fluid dynamics simulation methods were used. The pressure drop estimated from the customized modeling equation was further compared with the experimental data obtained from a bed composed of calcium‐alginate gel particles. In contrast to the conventional Ergun equation, the pressure drop estimated from the customized modeling equation was highly consistent with the experimental data. The result suggests that the customized modeling equation is a convenient tool for accurately predicting the pressure drop across a compressible soft particle bed. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-15T10:13:13.652543-05:
      DOI: 10.1002/aic.15138
       
  • Optimal design of renewable energy systems with flexible inputs and
           outputs using the P‐graph framework
    • Authors: Adrian Szlama; Istvan Heckl, Heriberto Cabezas
      Abstract: The P‐graph framework introduced by Friedler et al. (1992) is a general mathematical methodology based on Graph Theory which is applicable to many process design problems. We propose an extension of the P‐graph framework and the associated MILP model to account for operating units and systems where the inputs and outputs are variable. This is important because the P‐graph framework in its current form would otherwise apply only to systems where the ratios of inputs to outputs are fixed. Consequently, it is difficult to apply the method to many emerging systems without the new mathematical model presented here. We discuss and develop the model in detail, and we then illustrate its application with the case study of an energy system. We establish a structure with optimal cost for a baseline heat demand, and we further explore how the energy system structure and the feedstocks change as the heat demand increases. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-14T10:29:01.751877-05:
      DOI: 10.1002/aic.15137
       
  • A sparse PCA for nonlinear fault diagnosis and robust feature discovery of
           industrial processes
    • Authors: Hongyang Yu; Faisal Khan, Vikram Garaniya
      Abstract: Pearson's correlation measure is only able to model linear dependence between random variables. Hence, conventional principal component analysis (PCA) based on Pearson's correlation measure is not suitable for application to modern industrial processes where process variables are often nonlinearly related. To address this problem, a non‐parametric PCA model is proposed based on nonlinear correlation measures, including Spearman's and Kendall tau's rank correlation. These two correlation measures are also less sensitive to outliers comparing to Pearson's correlation, making the proposed PCA a robust feature extraction technique. To reveal meaningful patterns from process data, a generalized iterative deflation method is applied to the robust correlation matrix of the process data to sequentially extract a set of leading sparse pseudo‐eigenvectors. For online fault diagnosis, the T2 and SPE statistics are computed and analyzed with respect to the subspace spanned by the extracted pseudo‐eigenvectors. The proposed method is applied to two industrial case studies. Its process monitoring performance is demonstrated to be superior to that of the conventional PCA and is comparable to those of Kernel PCA and kernel independent component analysis (KICA) at a lower computational cost. The proposed PCA is also more robust in sparse feature extraction from contaminated process data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-13T03:11:40.726651-05:
      DOI: 10.1002/aic.15136
       
  • Single gold atoms stabilized on nanoscale metal oxide supports are
           catalytic active centers for various reactions
    • Abstract: In this article, we summarize key recent findings that demonstrate that single‐site atomic gold, stabilized through –O bonds on various metal oxide supports are the unique catalytic sites for a variety of reactions, including the water‐gas shift reaction, methanol partial oxidation and steam reforming reactions, and the selective dehydrogenation of ethanol. Atomic dispersion of gold on various metal oxides was followed with ac‐HAADF‐STEM imaging and x‐ray absorption spectroscopy (XANES/EXAFS). Gold nanoparticles and sub‐nanometer clusters are active only through their interfacial atoms directly interacting with the support, hence if present, they entail precious metal waste. From a design perspective, the important feature in these supported catalysts is the creation of many single‐site gold species anchored on the oxide support to maximize activity. Atomic gold‐centered catalyst designs afford 100% atom efficiency, and more importantly, have distinct product selectivity, different from that of extended metal surfaces. Novel experimental synthesis methods of atomically dispersed Au catalysts are discussed, which pave the way for the efficient use of precious metals, broadening the application of properly designed gold and other precious metals (Pt, Pd) to different reactions in energy conversion and green chemicals production. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-11T10:55:59.662165-05:
      DOI: 10.1002/aic.15134
       
  • Fe‐substituted Ba‐hexaaluminates oxygen carrier for carbon
           dioxide capture by chemical looping combustion of methane
    • Authors: Ming Tian; Xiaodong Wang, Xin Liu, Aiqin Wang, Tao Zhang
      Abstract: Fe‐substituted Ba‐hexaaluninates (BFA‐x (x=1‐3), x indicates Fe content) oxygen carrier (OC) were found to exhibit excellent sintering‐resistance under cyclic redox atmosphere at 800 oC thanks to the reservations of the structure during the CH4 reduction step, thus preventing the agglomeration of particles during the subsequent re‐oxidation step. Lattice oxygen highly active for the total combustion of CH4 was observed in the hexaaluminate structure and its chemical state was influenced by Fe content. The highest amount of active O coordinated with Fe3+ in the mirror plane (O‐Fe3+(M)) for the total combustion was reacted (0.77 mmol/g) for BaFe3Al9O19 hexaaluminate OC. As a result, it exhibited the best reactivity with the CH4 conversion of 83% and CO2 selectivity of 100%. Moreover, superior regeneration and recyclability was also obtained, which originated from the fully recovery of O‐Fe3+(M) in the hexaaluminate structure. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-11T10:55:33.080272-05:
      DOI: 10.1002/aic.15135
       
  • Rapid Green Manufacture of High Yield CdTe@Ca(OH)2 Nanocrystals and Their
           Performance on WLED
    • Abstract: The bottleneck of large‐scale production of semiconductor quantum dots (QDs) is how to solve heavy metal ions waste water and the rapid separation during industrial process. We report herein a facile strategy for fabricating CdTe@Ca(OH)2 nanocrystals exhibiting both improved photoluminescence (PL) stability and prolonged PL lifetime via an economical coprecipitating technology. The procedure on capping CdTe QDs into Ca(OH)2 crystals can enable the products to be easily filtrating separation and the content of residual Cd2+ filtrate solution to be reached to 0.238 ppm level. Also, we constructed fluorescent rod‐like heterocrystals by addition of saturated CaCl2 solution. We further utilize the CdTe@Ca(OH)2 nanocrystals as phosphor powders to construct white light emitting diode (WLED). The WLED presented here has good photoelectric properties with CRI of 82.4 at 350 mA, a color temperature of 4643 k and CIE coordinate of (0.3548, 0.3532), belonging to the white gamut, showing great potential in industrial application. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-11T10:51:57.218838-05:
      DOI: 10.1002/aic.15133
       
  • Flame Synthesis of Mixed Tin‐Silver‐Copper Nanopowders and
           Conductive Coatings
    • Authors: Munish K. Sharma; Di Qi, Raymond D. Buchner, William J. Scharmach, Vasilis Papavassiliou, Mark T. Swihart
      Abstract: We report the single‐step direct synthesis of tin‐silver‐copper nanopowders and nanostructured coatings using the flame‐based high‐temperature reducing jet (HTRJ) process. Nanostructured coatings were deposited and sintered within the HTRJ reactor to study the effect of reductive sintering temperature on their electrical conductivity and surface morphology. Although the ultimate application of these nanoparticles is in printed electronics, which requires dispersing them as stable inks before depositing and sintering them, our approach of direct deposition from the gas phase provides an upper limit on the conductivity achievable with a given composition. The directly deposited coatings had high electrical conductivity, including a value of 2 × 106 S/m for 36 wt% Cu ‐ 40 wt% Ag – 24 wt% Sn sintered at 200oC. This is twice the conductivity of a pure silver coating prepared under similar conditions. Moreover, similarly high electrical conductivity was achieved using only 20% Ag with sintering at 300 oC. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-11T10:51:29.89617-05:0
      DOI: 10.1002/aic.15132
       
  • The formulation of optimal mixtures with generalized disjunctive
           programming: A solvent design case study
    • Abstract: Systematic approaches for the design of mixtures, based on a Computer‐Aided Mixture/blend Design (CAMbD) framework, have the potential to deliver better products and processes. In most existing methodologies the number of mixture ingredients is fixed (usually a binary mixture) and the identity of at least one compound is chosen from a given set of candidate molecules. We present a novel CAMbD methodology for formulating the general mixture design problem where the number, identity and composition of mixture constituents are optimised simultaneously. To this end, Generalized Disjunctive Programming (GDP) is integrated into the CAMbD framework to formulate the discrete choices. This generic methodology is applied to a case study to find an optimal solvent mixture that maximises the solubility of ibuprofen. The best performance in this case study is obtained with a solvent mixture, showing the benefit of using mixtures instead of pure solvents to attain enhanced behaviour. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-08T18:09:48.36763-05:0
      DOI: 10.1002/aic.15122
       
  • Sublimation as a Function of Diffusion
    • Authors: Gang Qian; Nathan T. Morgan, Russell J. Holmes, E. L. Cussler, D. Wayne Blaylock, Robert C. Froese
      Abstract: Purification of large organic molecules in a tubular sublimator occurs by a combination of laminar flow, Knudsen diffusion, and volume diffusion. For laminar flow, the amount purified per area per driving force varies with pd2, where p is pressure and d is tube diameter. For Knudsen diffusion, it varies with d and is not a function of pressure. For volume diffusion, it is constant, consistent with experiment. This volume diffusion mechanism may offer an alternative explanation to slip flow for dilute gas transport of both organic semiconductors and common low molecular weight gases. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-08T18:09:19.573645-05:
      DOI: 10.1002/aic.15119
       
  • Low Concentration Sand Transport in Multiphase Viscous Horizontal Pipes An
           Experimental Study and Modeling Guideline
    • Authors: Kamyar Najmi; Brenton S. McLaury, Siamack A. Shirazi, Selen Cremaschi
      Abstract: Low concentration particle transport in multiphase horizontal pipes in the presence of a viscous liquid is experimentally investigated in this study. The experiments were conducted for a wide range of liquid and gas flow rates in both intermittent and stratified flows. Critical flow rates (velocity) is defined as the minimum required liquid and gas flow rates (velocities) to keep particles constantly moving in the pipe. This study investigates the effects of physical parameters such as sand concentration, sand size, pipe size and liquid viscosity are also experimentally investigated. It is observed that that critical velocity is a function of sand concentration and sand size and increases by increasing either within the ranges of particle concentrations and sizes examined. Regarding the effect of carrier liquid viscosity, the experimental data reveals that by increasing viscosity the minimum required flow rates to constantly move sand along the pipe increases within the range examined. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-08T11:05:54.29066-05:0
      DOI: 10.1002/aic.15131
       
  • Advances in Materials
    • Authors: Sotiris E. Pratsinis
      PubDate: 2015-12-08T11:04:31.5906-05:00
      DOI: 10.1002/aic.15129
       
  • Local Hydrodynamic Parameters of Bubble Column Reactors Operating with
           non‐Newtonian Liquids: Experiments and Models Development
    • Authors: Amin Esmaeili; Christophe Guy, Jamal Chaouki
      Abstract: This work is aimed at investigating the effects of liquid phase rheology on the local hydrodynamics of bubble column reactors operating with non‐Newtonian liquids. Local bubble properties, including bubble frequency, bubble chord length, and bubble rise velocity, are measured by placing two in‐house made optical fiber probes at various locations within a bubble column reactor operating with different non‐Newtonian liquids. It was found that the presence of elasticity can noticeably increase the bubble frequency but decreases the bubble chord length and its rise velocity. The radial profiles of bubble frequency, bubble chord length and bubble rise velocity are shown to be relatively flat at low superficial gas velocity while they become parabolic at high superficial gas velocity. Moreover, the bubble size and gas holdup are correlated with respect to dimensionless groups by considering the ratio between dynamic moduli of viscoelastic liquids. The novel proposed correlations are capable of predicting the experimental data of bubble size and gas holdup within a mean absolute percentage error of 9.3% and 10%, respectively. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-08T10:59:08.496762-05:
      DOI: 10.1002/aic.15130
       
  • On Fingering of steam chambers in steam‐assisted heavy oil recovery
    • Authors: D. Zhu; J.A. Bergerson, I.D. Gates
      Abstract: Western Canadian oil sands reservoirs are among the largest petroleum accumulations in the world. Given original oil viscosity up to 5,000,000 mPa‐s, these oils are currently recovered from these reservoirs by using steam which heats the oil to ∼250°C with reduced viscosities
      PubDate: 2015-12-08T07:32:58.2977-05:00
      DOI: 10.1002/aic.15121
       
  • The importance of gravity in droplet evaporation: A comparison of pendant
           and sessile drop evaporation with particles
    • Authors: Nicole Raley Devlin; Katherine Loehr, Michael T. Harris
      Abstract: As a droplet with particles evaporates, the particles deposit on the substrate surface. In this work, we show the extent of gravitational effects on the particle deposition profile and propose a new model for particle tracing in an evaporating droplet which accounts for gravitational effects. Experimentally, we compare pendant and sessile water droplets with 1 µm and 3 µm polystyrene particles. Numerically, the finite element method was used to create a transport model of the evaporating droplet system and particle deposition. The numerical and experimental results have excellent agreement and show that a pendant water droplet with 1 µm and 3 µm polystyrene spheres has significant separation of the two particle sizes. Finally, a phase diagaram was created to map different deposition profiles for various graviational Péclet numbers (PeG) and ratios of Péclet number to Damköhler number (Pe/Da). This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-08T07:31:15.408884-05:
      DOI: 10.1002/aic.15120
       
  • Separation of C6H6 and C6H12 from H2 using ionic liquid/PVDF composite
           membrane
    • Authors: Yuichiro Hirota; Yohei Maeda, Takashi Furusawa, Norikazu Nishiyama, Akira Ito
      Abstract: Hydrogen has been proposed as a clean energy carrier that helps in alleviating environmental pollution caused by fossil fuels. However, there are many difficulties in storing and transporting H2. A system that has a low potential risk for H2 storage and transportation is needed to be established, since it has an explosive combustion rate and very low combustion temperature. Organic chemical hydrides (OCH), which means hydrogenated aromatic hydrocarbon (like cyclohexane, methylcyclohexane and decaline) offer many advantages, such as high H2 content (e.g. 7.2 wt% of cyclohexane) and the easy transporting system1. Recently, Chiyoda Corporation started up demonstration plants of the OCH system2. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-06T03:15:48.663506-05:
      DOI: 10.1002/aic.15127
       
  • A review of the statistical turbulence theory required extending the
           population balance closure models to the entire spectrum of turbulence
    • Authors: Jannike Solsvik; Hugo A. Jakobsen
      Abstract: The models for fluid particle breakage and coalescence due to turbulence are generally limited to the inertial subrange of isotropic turbulence and infinite Reynolds numbers. A rigorous procedure for extending the fluid particle breakage and coalescence closures to the entire spectrum of isotropic turbulence and for a wider range of Reynolds numbers can be established based on statistical turbulence theory. The modeling procedure consists of a three‐dimensional literature model energy spectrum for the dissipation, inertial and energy containing subranges of isotropic turbulence1, and an exact literature integral relation for determining the second‐order longitudinal structure function from the three‐dimensional energy spectrum2. A review of the requisite statistical turbulence theory and the use of the model energy spectrum is provided in this work because the necessary details are not easily accessible in the chemical engineering literature and misconceptions are found in the publications of the previous modeling attempts. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-06T03:15:44.599328-05:
      DOI: 10.1002/aic.15128
       
  • Editorial – A Progress Report
    • Authors: Mike Harold
      PubDate: 2015-12-06T03:12:44.601155-05:
      DOI: 10.1002/aic.15123
       
  • Novel carboxyethyl amine sodium salts as draw solutes with superior
           forward osmosis performance
    • Authors: Qing Wu Long; Yan Wang
      Abstract: In this work, a series of carboxyethyl amine sodium salts (CASSs) with different carboxyl group numbers, are synthesized as draw solutes for FO application. Their chemical structures are examined by 1HNMR and HRMS. FO performances are investigated and compared in terms of different physicochemical properties. The effects of the CASS concentration on the osmotic pressure and viscosity of the draw solutions, as well as the resulted FO performance are also systematically investigated. A high water flux of 23.07 LMH and an acceptable reverse salt flux of 0.75 gMH can be achieved with 0.5 g/mL TTHP‐Na draw solution under PRO mode, which is superior to most other draw solutes reported in previous literatures. Triethylenetetramine hexapropionic acid sodium (TTHP‐Na) draw solution is further evaluated as the draw solution to recycle the Congo red solution via FO process to examine its applicability for waste water treatment. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-06T03:12:41.891936-05:
      DOI: 10.1002/aic.15126
       
  • Ethanol/Water Mixture Pervaporation Performance of b‐oriented
           Silicalite‐1 Membranes Made by Gel‐Free Secondary Growth
    • Abstract: b‐oriented silicalite‐1 membranes on porous silica supports were synthesized using gel‐free secondary growth. The porous silica supports were made by pressing crushed quartz fibers followed by sintering and polishing, and further modified by slip‐coating three layers of Stӧber silica particles (1,000, 350 and 50 nm). The b‐oriented seed layers were prepared by rubbing silicalite‐1 particles (2 μm × 0.8 μm × 3 μm along a‐, b‐, and c‐axis, respectively) after depositing a polymeric layer on the support. After silicalite‐1 seed deposition, a final coating of spherical silica particles was applied. Well‐intergrown, μm‐thick, b‐oriented membranes were obtained, which, after calcination, exhibited ethanol permselectivity in ethanol/water mixture pervaporation. At 60°C and for ∼5 wt% ethanol/water mixtures, the best membrane exhibited overall pervaporation separation factor of 85 (corresponding to membrane intrinsic selectivity of 7.7) and total flux of 2.1 kg/(m2·h). This performance is comparable to the best performing MFI membranes reported in the literature. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-06T03:12:37.413984-05:
      DOI: 10.1002/aic.15124
       
  • Crystallinity Dynamics of Gold Nanoparticles during Sintering or
           Coalescence
    • Authors: Eirini Goudeli; Sotiris E. Pratsinis
      Abstract: The crystallinity of gold nanoparticles during coalescence or sintering is investigated by molecular dynamics. The method is validated by the attainment of the Au melting temperature that increases with increasing particle size approaching the Au melting point. The morphology and crystal dynamics of nanoparticles of (un)equal size during sintering are elucidated. The characteristic sintering time of particle pairs is determined by tracing their surface area evolution during coalescence. The crystallinity is quantified by the disorder variable indicating the system's degree of disorder. The atoms at the grain boundaries are amorphous, especially during particle adhesion and during sintering when grains of different orientation are formed. Initial grain orientation affects final particle morphology leading to exposure of different crystal surfaces that can affect the performance of Au nanoparticles (e.g. catalytic efficiency). Coalescence between crystalline and amorphous nanoparticles of different size results in polycrystalline particles of increasing crystallinity with time and temperature. Such simulations of free‐standing Au nanoparticle coalescence are relevant also to Au nanoparticles on supports that do not exhibit strong affinity or strong metal support interactions. This article is protected by copyright. All rights reserved.
      PubDate: 2015-12-06T03:12:23.988879-05:
      DOI: 10.1002/aic.15125
       
  • Amine‐functionalized mesoporous silica. A material capable of CO2
           adsorption and fast regeneration by microwave heating
    • Abstract: The surface of ordered mesoporous (MCM‐48) silica has been subjected to covalent grafting with silane molecules containing one to three amino groups. The dielectric properties of the materials were studied in detail, and the functionalized materials were used for CO2 adsorption at room temperature, followed by regeneration under either conventional heating or microwave irradiation. It has been found that, as the intensity of functionalization with amino groups increases (from mono to tri‐amino silanes) both the CO2 load and the dielectric response at microwave frequencies increase. In particular, functionalization with a tri‐amino silane derivative gave the highest CO2 adsorption and the fastest microwave heating, resulting in a 4‐fold acceleration of adsorbent regeneration. The grafted material was fully stable for at least 20 adsorption‐regeneration cycles, making it an ideal candidate for microwave‐swing adsorption (MWSA) processes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-26T11:05:39.238678-05:
      DOI: 10.1002/aic.15118
       
  • Fabrication of high aspect ratio and open‐ended TiO2 nanotube
           photocatalytic arrays through electrochemical anodization
    • Authors: Roong Jien Wong; Sanly Liu, Yun Hau Ng, Rose Amal
      Abstract: Well‐aligned, high aspect‐ratio and open‐ended TiO2 nanotube arrays secured within a Ti foil (TiO2 nanotubes cartridge) were successfully prepared through the double‐sided anodization method. With ∼210 µm of nanotube length, the anodic growth of TiO2 was accelerated and stabilized by the lactic acid‐containing ethylene glycol electrolyte. In the absence of lactic acid, the anodization led to detachment of nanotubes from the Ti foil after 5‐6 hours of high voltage (80 V) anodization. Transmission electron microscope image and Raman spectrum revealed that the as‐anodized TiO2 nanotube arrays without annealing treatment were partially crystalline anatase and demonstrated photocatalytic activity in the mineralization of formic acid. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-25T18:09:36.473216-05:
      DOI: 10.1002/aic.15117
       
  • Influence of slip on the flow of a yield stress fluid around a flat plate
    • Authors: Fiacre Ahonguio; Laurent Jossic, Albert Magnin
      Abstract: This experimental study deals with the influence of slip on the non‐inertial flow of a viscoplastic fluid around a flat plate moving at a constant velocity. The bulk and interfacial properties of the viscoplastic fluid have been finely characterized. The drag force has been analyzed with regards to the flow velocity and for two tribological conditions: adherence and slip. The drag force decreases with the velocity and is reduced in the presence of slip. Kinematic fields have been measured by PIV, to determine the influence of both the velocity and the tribological conditions on the liquid and solid regions of the flow. The results highlight no significant influence of the flow velocity on the thickness of the boundary layer and rigid zones. The wall shear stresses along the plate obtained from force measurements and slip velocities are then compared to rheometrical measurements. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-24T11:18:20.814059-05:
      DOI: 10.1002/aic.15116
       
  • Optimization of Grade Transitions in Polyethylene Solution Polymerization
           Processes
    • Authors: Jun Shi; Lorenz T. Biegler, Intan Hamdan
      Abstract: This study considers the development of optimization models for grade transition of polyethylene solution polymerization processes. A detailed mathematical model is developed to capture the dynamics of the solution polymerization process. This includes time delay models for vapor and liquid recycle streams as well as a reduced, yet accurate, vapor‐liquid equilibrium (VLE) model derived from rigorous VLE calculations. Simultaneous dynamic optimization approach is applied to solve the optimization problem to reduce off‐spec production time and transition time. Two optimization formulations, single stage and multistage, are developed to deal with single‐value target and specification bands of product properties, respectively. The results show significant reductions in grade transition time and off‐spec production time. In addition, the multistage formulation designed for problems with specification bands is developed and demonstrated. The mutistage formulation outperforms its single stage counterpart. It minimizes transition time and off‐spec production directly, and leads to higher performance control profiles. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:50:08.558568-05:
      DOI: 10.1002/aic.15113
       
  • Kinetic Modeling of Pt/C Catalyzed Aqueous Phase Glycerol Conversion with
           In Situ Formed Hydrogen
    • Authors: Xin Jin; Prem S. Thapa, Bala Subramaniam, Raghunath V. Chaudhari
      Abstract: Detailed kinetic modeling of Pt/C catalyzed conversion of glycerol to lactic acid, glycols and alcohols with in‐situ formed hydrogen is reported. Experimental concentration‐time profiles were obtained in a batch slurry reactor at different glycerol concentrations, nitrogen partial pressures, and NaOH concentrations in a temperature range of 130 ‐ 160 oC. Six different kinetic models, were evaluated to describe the competing dehydrogenation, hydrogenolysis, dehydration and C‐C cleavage reactions, and discriminated to fit the experimental data. It is found that a “dual‐similar‐site” mechanism involving alkali promoted dehydrogenation, on two adjacent Pt sites to affect C‐C and C‐O cleavage best describes the experimental data. The dehydrogenation reaction proceeds with a significantly lower activation barrier (Ea = 53 kJ/mol) compared to the non‐catalytic hydrothermal conversion (Ea = 128 kJ/mol). The activation energy for glycerol hydrogenolysis on Pt/C catalyst without adding hydrogen is estimated to be 64 kJ/mol. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:49:41.540332-05:
      DOI: 10.1002/aic.15114
       
  • Ceramic Tubular MOF Hybrid Membrane Fabricated through In Situ
           Layer‐by‐Layer Self‐Assembly for Nanofiltration
    • Abstract: Nanofiltration has been playing an important role in water purification, in which the developments of novel membrane materials and modules are among significant. Herein, a metal‐organic framework (MOFs) hybrid membrane, ZIF‐8/PSS was fabricated on a tubular alumina substrate through a layer‐by‐layer self‐assembly technique. ZIF‐8 particles in situ grow into PSS layers to improve their compatibility and dispersion, thereby getting high quality membrane, which was loaded into a steel tubular module for nano‐filtrating dyes from water. Under optimized conditions, it shows outstanding nanofiltration properties towards methyl blue, with the flux of 210 Lm−2 h−1 MPa−1 and the rejection of 98.6%. Furthermore, the good pressure resistance ability and running stability of the membrane were revealed, which can be attributed to use the ceramic substrate and the inherent stability of ZIF‐8. This work thus illustrates a simple approach for fabricating MOFs hybrid membranes on tubular ceramic substrates, having great potential for industrial applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-20T17:48:32.332626-05:
      DOI: 10.1002/aic.15115
       
  • Simulation of biomass char gasification in a downdraft reactor for syngas
           production
    • Authors: Augustina Ephraim; Victor Pozzobon, Olivier Louisnard, Doan Pham Minh, Ange Nzihou, Patrick Sharrock
      Abstract: A steady‐state, one‐dimensional computational fluid dynamics model of wood char gasification in a downdraft reactor is presented. The model is not only based on reaction kinetics and fluid flow in the porous char bed but also on equations of heat and mass conservation. An original OpenFOAM solver is used to simulate the model and the results are found to be in good agreement with published experimental data. Next, a sensitivity analysis is performed to study the influence of reactor inlet temperature and gas composition on char conversion, bed temperature profile and syngas composition. In addition, the evolution of the complex reaction mechanisms involved in mixed atmosphere gasification is investigated, and the most suitable operating parameters for controlling syngas composition are evaluated. Our simulation results provide essential knowledge for optimizing the design and operation of downdraft gasifiers in order to produce syngas that meets the requirements of various biofuel applications. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-18T18:44:36.733649-05:
      DOI: 10.1002/aic.15111
       
  • Natural convection in shear‐thinning yield stress fluids in a square
           enclosure
    • Abstract: The influence of viscoplastic rheological features on the Rayleigh‐Bénard convection is investigated by numerical means in order to compare with first experimental results given by Darbouli et al, (Phys. Fluids 2013;25). The fluid is modelled by a regularized Herschel‐Bulkley law which is often used to fit numerous pasty fluids. We consider natural convection in a 2D square cavity heated from below. Critical values of Oldroyd number Od and yield number Y are provided. Numerical results highlight a stabilizing effect of the yield stress as well as a destabilizing effect of increasing shear‐thinning coefficient n since the increase in n enhances the heat transfer in the range of our calculations. Unyielded regions are located in the square corners of the cavity and in the cavity where convection occurs. The unyielded zones size increases with the increase in Od and can invade all the cavity for sufficiently large values of Od. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-18T18:44:08.673039-05:
      DOI: 10.1002/aic.15112
       
  • Osmotic power production from seawater brine by hollow fiber membrane
           modules: Net power output and optimum operating conditions
    • Abstract: This study analyzes the net energy output and optimum operating conditions for osmotic power generation from seawater brine based on the currently available hollow fiber membranes in the module scale. Factors that are influential on membrane performances, such as external concentration polarization, internal concentration polarization, salt reverse diffusion and dilution have been taken into account. Net power density is defined and applied to characterize the efficiency of the PRO system, in terms of power production minus pumping energy, pre‐treatment cost and energy consumption by pressure drop in the membranes. When using 1M NaCl as the draw solution and 10 mM NaCl as the feed, it is found that up to 7 W m−2 net power density can be harvested by the PRO system depending on the water sources. Coupling with the existing RO plant is highly beneficial in terms of readily available high pressure source, high salinity and less or negligible pre‐treatment costs for the draw solution. Sources with higher salt concentrations are preferred. The optimum hydraulic pressure, module length, flow rate to membrane area ratio and feed to draw flow rate ratio have also been analyzed to maximize the net power output. In addition, implications on hollow fiber development are discussed. Fibers with high water permeability, lower structural parameter, good mechanical stability, better fouling resistance and outer‐selective configurations are recommended for further studies. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:18:24.29555-05:0
      DOI: 10.1002/aic.15109
       
  • Impact of ownership structure along the value chain in the manufacturing
           business
    • Authors: Jan H Scholtz
      Abstract: In the chemical and petrochemical industry it is quite common that the manufacturing of a final product is the result of several consecutive steps which can be owned and operate by one or many participants. Although not always practical, equal ownership among all partners along the value chain is often recommended as a way to simplify business structure, ensuring all partners share equally in the ups and downs of an uncertain market. In contrast to this approach, there are instances where more benefit can be derived from having different owners and operators along the value chain. Examples which are common practise in the industry are the supply of utilities (e.g. electricity), feedstock and services. In these cases the non‐integrated approach offers value as: It provides the operator of the upstream or utility plants the opportunity to specialize, for example, by operating very similar plants around the world. Such specialization enables the use of regional operating centres, minimum onsite cash costs, optimized operating conditions, minimized energy consumption and the optimal use of other variable cost parameters. This paper shows that if outsourcing results in a cash cost saving by an upstream operator, the benefit to the downstream owner will (in financial reward) be proportional to the cash cost saving achieved. In absolute terms, the magnitude of the benefit is moderated by the size of the downstream capital investment. (The bigger the downstream investment relative to the upstream investment, the smaller the impact of the saving on the economics of the downstream company.) As a “utility provider” an upstream operator benefits from lower risk in terms of offtake and market price uncertainties. Such owners benefit from a lower cost of capital, and as such also have lower return expectations than players further along in the value chain (who are exposed to all the uncertainties in volatile markets). This paper shows that the positive impact of such benefits to the return of the downstream partner is directly proportional the difference in return expectations between the upstream and downstream company. Once again, the absolute magnitude of the saving becomes more substantial as the ratio of upstream capital investment increases relative to the downstream capital investment. Economy of learning may also enable a specialized upstream company to obtain an asset at a lower capital than a less specialized downstream operator. This paper shows that the positive impact of such a benefit is very similar to that of a lower return expectation by the upstream company. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:17:35.390268-05:
      DOI: 10.1002/aic.15108
       
  • Understanding hydrotropism: A chemical engineering perspective
    • Authors: Qian Gao; Jie Xiao, Xiao Dong Chen
      Abstract: The mechanism of root hydrotropism has been a mystery for many years, due to the complexity of the interactions between the external environment and plants themselves. In order to gain an engineering perspective, the time‐dependent hydrotropism of a single root has been modeled, initially using a two‐dimensional model. Based on the water and nutrient distribution in rhizosphere as computed with the conservation equations, together with a basic reaction‐kinetics‐type growth model and an intuitive root bending model, it has been found that the root already possesses the property of hydrotropism. For the first time, hydrotropism could be tracked by a process engineering model, which is a new idea based upon chemical engineering concept, suggesting an alternative mechanism of hydrotropism. The effects of different initial root widths, lengths and other growth/transport coefficients on root hydrotropism have then been explored in this study. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T18:17:10.182728-05:
      DOI: 10.1002/aic.15110
       
  • Fast Pyrolysis of Glucose‐Based Carbohydrates with Added NaCl Part
           1: Experiments and Development of a Mechanistic Model‡
    • Authors: Xiaowei Zhou; Michael W. Nolte, Heather B. Mayes, Brent H. Shanks, Linda J. Broadbelt
      Abstract: Sodium ions, one of the natural inorganic constituents in lignocellulosic biomass, significantly alter pyrolysis behavior and resulting chemical speciation. Here, experiments were conducted using a micropyrolyzer to investigate the catalytic effects of NaCl on fast pyrolysis of glucose‐based carbohydrates (glucose, cellobiose, maltohexaose and cellulose), and on a major product of cellulose pyrolysis, levoglucosan. A mechanistic model that addressed the significant catalytic effects of NaCl on the product distribution was developed. The model incorporated interactions of Na+ with cellulosic chains and low molecular weight species, reactions mediated by Na+ including dehydration, cyclic/Grob fragmentation, ring‐opening/closing, isomerization, and char formation, and a degradation network of levoglucosan in the presence of Na+. Rate coefficients of elementary steps were specified based on Arrhenius parameters. The mechanistic model for cellulose included 768 reactions of 222 species, which included 252 reactions of 150 species comprising the mechanistic model of glucose decomposition in the presence of NaCl. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T08:20:41.400962-05:
      DOI: 10.1002/aic.15106
       
  • Fast Pyrolysis of Glucose‐Based Carbohydrates with Added NaCl Part
           2: Validation and Evaluation of the Mechanistic Model‡
    • Authors: Xiaowei Zhou; Michael W. Nolte, Heather B. Mayes, Brent H. Shanks, Linda J. Broadbelt
      Abstract: A mechanistic model considering the significant catalytic effects of Na+ on fast pyrolysis of glucose‐based carbohydrates was developed in Part 1 of this study. A computational framework based on continuous distribution kinetics and mass action kinetics was constructed to solve the mechanistic model. Agreement between model yields of various pyrolysis products with experimental data from fast pyrolysis of glucose‐based carbohydrates dosed with NaCl ranging from 0 − 0.34 mmol/g at 500°C validated the model and demonstrated the robustness and extendibility of the mechanistic model. The model was able to capture the yields of major and minor products as well as their trends across NaCl concentrations. Modeling results showed that Na+ accelerated the rate of decomposition and reduced the time for complete thermoconversion of carbohydrates. The sharp reduction in the yield of levoglucosan from fast pyrolysis of cellulose in the presence of NaCl was mainly caused by reduced decomposition of cellulose chains via endchain initiation and depropagation due to Na+ favoring competing dehydration reactions. Analysis of the contributions of reaction pathways showed that the decomposition of levoglucosan made a minor contribution to its yield reduction and contributed less than 0.5% to the final yield of glycolaldehyde from fast pyrolysis of glucose‐based carbohydrates in the presence of NaCl. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T08:16:05.658271-05:
      DOI: 10.1002/aic.15107
       
  • Facile Growth of 1‐D Nanowire‐based WO3 Thin Films with
           Enhanced Photoelectrochemical Performance
    • Abstract: We developed a flame reactor embedded with a constant tungsten wire feeding system to prepare 1‐D nanostructured tungsten oxide thin film for photoelectrochemical water splitting. Photoactive vertically‐aligned nanowire‐based WO3 thin films could be obtained with a controlled thickness via a flame vapor deposition process followed by air‐annealing. The photoelectrochemical performances of WO3 photoelectrodes for different thin film thicknesses were examined. The optimum thickness of WO3 thin film was found to be about 7.2 μm for PEC water splitting based on IPCE plots and I‐V curves. The WO3 prepared with optimum thickness showed better PEC performance than those of recently reported nanostructured WO3 photoanodes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-17T05:19:44.421123-05:
      DOI: 10.1002/aic.15105
       
  • The dissipation rate of news in online mass media evaluated by chemical
           engineering and process control tools
    • Authors: Robert N. Grass; Wendelin J. Stark
      Abstract: Basic chemical engineering and processes control tools were utilized to describe the flow of news information in the Internet. Data on the news coverage of scientific articles provided by Altmetric were analyzed for six chemistry journals. The timecourse of the news was modeled using linear system dynamics, resulting in an interpretable description of the timescales involved. The model was additionally tested by applying it to the flow of non‐scientific news information. An investigation on the distribution of news items per scientific article further identified online news generation as a preferential growth process. The model results allowed a discussion on scientific impact in public media and an analysis on how this impact can be influenced by authors and journals. In respect to the field of engineering the work shows that traditional ChemE and process control tools developed for the abstraction of physical and chemical systems can also be utilized to describe social and information related processes. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-13T23:36:28.348331-05:
      DOI: 10.1002/aic.15103
       
  • Gas‐liquid mass transfer behavior in a surface‐aerated vessel
           stirred by a novel long‐short blades agitator
    • Authors: Peicheng Luo; Jun Wu, Xiang Pan, Yueqiao Zhang, Hua Wu
      Abstract: For a recently developed long‐short blades (LSB) agitator, we have investigated its critical rotational speed for the onset of gas entrainment, power number and gas‐liquid mass transfer behavior, in the case of surface aeration. The effect of the LSB configurations and the liquid level on the agitator performance has been studied in details. The obtained results clearly show several advantages of the LSB agitator in gas‐liquid mass transfer with respect to the agitators in the literature. It is found that its gas‐liquid volumetric mass transfer coefficient at a given specific power can be several times larger than those shown in the literature. It can also avoid decrease in the gas‐liquid mass transfer rate as the liquid level increases. In addition, the bubble distribution in the system is more uniform with respect to conventional agitators, resulting from better distribution of the dissipated energy for the LSB agitator. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-13T23:32:47.937379-05:
      DOI: 10.1002/aic.15104
       
  • Synthesis, characterization, and tunable adsorption and diffusion
           properties of hybrid ZIF‐7‐90 frameworks
    • Authors: Fereshteh Rashidi; Catherine R. Blad, Christopher W. Jones, Sankar Nair
      Abstract: Hybrid zeolitic imidazolate frameworks (ZIFs), containing more than one type of imidazolate linker, can allow highly tunable molecular sieving and adsorption. Their crystallization becomes more challenging when the end‐member (single‐linker) ZIFs crystallize in different crystal systems. We demonstrate the controlled synthesis and detailed characterization of hybrid ZIF‐7‐90 frameworks containing linkers of ZIF‐7 (rhombohedral) and ZIF‐90 (cubic). ZIF‐7‐90 materials with SOD‐type topology are obtained in three crystalline phases depending on the linker composition and synthesis technique. The effect of synthesis conditions on the activation‐induced phase transition from rhombohedral to other topologies is studied. Nitrogen physisorption at 77 K and CO2 physisorption at 273 K shows the tunability of the pore size distribution and the framework flexibility as a function of framework composition. Measurements of water adsorption and butane isomer diffusion illustrate the tunability of diffusivity over seven orders of magnitude and control of hydrophobic to hydrophilic adsorption behavior. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-11T18:39:56.729568-05:
      DOI: 10.1002/aic.15102
       
  • The Effect of Inter-particle Cohesion on Powder Mixing in a Ribbon Mixer
    • Authors: H. Musha; G. R. Chandratilleke, K.J. Dong, A.B. Yu
      Abstract: The effect of inter-particle cohesion on powder mixing in a ribbon mixer was studied by means of the discrete element method. It is shown that with an increase in the cohesion, the mixing rate and uniformity of mixing deteriorate, the coordination number increases indicating the loss of the ability of particles to be engaged in free flowing motion, and a majority of particles have a stronger tangential velocity allowing bulk angular motion of particles. Conversely, with a decrease in the cohesion, more particles have larger axial velocities, which will increase convective motion in the axial direction. When the cohesion is reduced, the number of particles having large radial stresses increases, and normal stress in the axial direction remains mostly unchanged. The ribbon mixer can mix cohesive particles in a wide range of the Bond numbers without causing large stresses. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:44:40.907281-05:
      DOI: 10.1002/aic.15101
       
  • Multi-Cycle Investigation of a Sol-Gel-Derived Fe2O3/ATP Oxygen Carrier
           for Coal Chemical Looping Combustion
    • Authors: Qingjie Guo; Mingming Yang, Yongzhuo Liu, Qinqin Yang, Yunpeng Zhang
      Abstract: Fe-based oxygen-carrier (OC) particles with attapulgite (ATP) as a support material for coal chemical looping combustion (CLC) have been prepared using a sol-gel approach. The multi-redox characteristics of the prepared Fe4ATP6 (Fe2O3 to ATP mass ratio of 40:60) were experimentally examined in a batch fluidized bed reactor at 900°C. The experimental results indicated that the synergistic reactions between ATP and Fe2O3 increased the coal conversion. Fe4ATP6 exhibited high reactivity, particularly for low-rank coals, in the CLC process. The improved pore structure and surface area were responsible for the high reactivity of Fe4ATP6. In 60 redox cycles, H2 was mainly generated in the outlet gas as the carbon conversion efficiency had reached 95%, and both the coal combustion efficiency and CO2 capture efficiency were greater than 95%. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:44:16.117854-05:
      DOI: 10.1002/aic.15100
       
  • Performance of a Medical Oxygen Concentrator Using Rapid Pressure Swing
           Adsorption Process: Effect of Feed Air Pressure
    • Authors: Rama Rao Vemula; Mayuresh V. Kothare, Shivaji Sircar
      Abstract: The effects of feed air pressure on the steady state performance of a medical oxygen concentrator (MOC) was experimentally evaluated using a novel design of a MOC unit which produced a continuous stream of ∼ 90% O2 employing a rapid pressure swing adsorption (RPSA) process scheme. Dry, CO2 free air containing ∼ 1% Ar at different feed gas pressures was used in the tests in conjunction with a commercial sample of LiLSX zeolite as the N2 selective adsorbent in the process. The study showed that the bed size factor (BSF) can be systematically reduced by increasing the feed air pressure for any given total cycle time. The effect of feed air pressure on the oxygen recovery (R) is, however, more complex; it increases with increasing feed pressure only at longer cycle times while the effect is marginal at shorter cycle times. The study also shows that the BSF cannot be indefinitely reduced by lowering total process cycle time at any pressure – a minimum is exhibited in the BSF-cycle time plot. The minimum value of the BSF decreases as the feed pressure is increased. The cycle time for the minimum BSF is, however, not significantly altered by the feed pressure in the data range of this work. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-04T21:41:06.825359-05:
      DOI: 10.1002/aic.15099
       
  • Mean-Squared-Error-Based Method for Parameter Ranking and Selection with
           Non-Invertible Fisher Information Matrix
    • Authors: Zahra Eghtesadi; Kimberley B. McAuley
      Abstract: Two approaches are developed to rank and select model parameters for estimation in complex models when data are limited, the Fisher information matrix (FIM) is non-invertible, and accurate predictions are desired at key operating conditions. These approaches are evaluated using synthetic data sets in a linear regression example to examine the influence of several factors including: the quality of initial parameter guesses, uncertainty ranges for initial parameter values, noise variances, and the operating region of interest. It is shown that using a reduced FIM with full rank leads to more reliable model predictions for a variety of cases than the alternative approach using the pseudo-inverse of the FIM. The proposed reduced-FIM methodology also provides better predictions than related techniques that do not consider the operating region where reliable predictions are required. The methodology is illustrated using a nonlinear differential equation model of a polymer film casting process. This article is protected by copyright. All rights reserved.
      PubDate: 2015-11-03T17:50:30.605706-05:
      DOI: 10.1002/aic.15096
       
  • Probing Pore Blocking Effects on Multiphase Reactions within Porous
           Catalyst Particles Using a Discrete Model
    • Abstract: A discrete model coupling mass transfer, reaction, and phase change in porous catalyst particles is proposed to probe pore blocking effects on multiphase reactions. This discrete model is validated by comparing the results with experiments and those obtained using a continuum model, for the hydrogenation of benzene to cyclohexane in Pd/γ‐alumina catalyst particles. The results show that pore blocking has a significant effect on the effectiveness factor and can contribute to up to 50% of the hysteresis loop area for multiphase reactions in porous catalysts, indicating that pore blocking must be accounted for. Moreover, the pore blocking effects are significantly enhanced when the pore network is poorly connected and the pore size distribution is wide, while the pore blocking effects are insensitive to the volume‐averaged pore size. Multiphase catalyst material characterization and design should account for this effect. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-31T09:50:00.184894-05:
      DOI: 10.1002/aic.15095
       
  • Highly Porous Ti4O7 Reactive Electrochemical Water Filtration Membranes
           Fabricated via Electrospinning/Electrospraying
    • Authors: Melissa C. Santos; Yin Jing, Lei Fang, Brian P. Chaplin, Yossef A. Elabd
      Abstract: Porous, flexible, reactive electrochemical membranes (REMs) for water purification were synthesized by a novel simultaneous electrospinning/electrospraying (E/E) technique, which produced a network of poly(sulfone) fibers and Ti4O7 particles as evidenced by scanning electron microscopy. Cyclic voltammetry indicated that the kinetics for water electrolysis reactions and the Fe(CN)64‐/3‐ redox couple were enhanced by Ti4O7 deposition using the E/E technique. Membrane filtration experiments using phenol as a model contaminant showed a 2.6‐fold enhancement in the observed first‐order rate constant for phenol oxidation (kobs,phenol) in filtration mode relative to cross‐flow operation. Phenol oxidation in filtration mode was approaching the pore diffusion mass transfer limit, and was 6 to 8 times higher than measured in a previous study that utilized a ceramic Ti4O7 REM operated in filtration mode and is comparable to rate constants obtained with carbon nanotube flow‐through reactors, which are among the highest reported in the literature to date. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-30T17:56:53.330876-05:
      DOI: 10.1002/aic.15093
       
  • A theoretical unsteady‐state model for kL of bubbles based on the
           framework of wide energy spectrum
    • Authors: Luchang Han; Jin Fu, Ming Li, Shenggao Gong, Ningning Gao, Chi Zhang, He'an Luo
      Abstract: An unsteady‐state model for predicting mass transfer coefficient kL of bubbles with mobile surface was developed for turbulent gas‐liquid dispersions. This model was derived from an unsteady‐state convection and diffusion equation through a characteristics method. Unlike the previous work, this model considered the contributions of the amount of fluid structures of different scales (i.e. eddies) existing in the turbulent flows, the frequency of eddies arriving at the surface, the deformation and oscillation of bubbles to mass transfer. This model was based on the framework of wide energy spectrum and can account for the role of eddies of different sizes in mass transfer. Thus the assumption adopted by the previous models that mass transfer was controlled by eddies of certain sizes is no more needed. The overall kL predicted by the proposed model showed a better agreement with the reported experimental data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-29T18:49:15.382865-05:
      DOI: 10.1002/aic.15092
       
  • Hybrid model for optimization of crude oil distillation units
    • Authors: Gang Fu; Yoel Sanchez, Vladimir Mahalec
      Abstract: Planning, scheduling and real time optimization (RTO) are currently implemented by using different types of models, which causes discrepancies between their results. This work presents a single model of a crude distillation unit (preflash, atmospheric, and vacuum towers) suitable for all of these applications, thereby eliminating discrepancies between models used in these decision processes. Product true boiling point (TBP) curves are predicted via partial least squares model from the feed TBP curve and operating conditions (flows, pumparound heat duties, furnace coil outlet temperatures). Combined with volumetric and energy balances, this enables prediction of crude distillation on par with a rigorous distillation model, with 0.5% RMSE over a wide range of conditions. Associated properties (e.g. gravity, sulfur) are computed for each product based on its distillation curve and corresponding property distribution in the feed. Model structure makes it particularly amenable for development from plant data. This article is protected by copyright. All rights reserved.
      PubDate: 2015-10-28T18:48:57.133376-05:
      DOI: 10.1002/aic.15086
       
  • A systematic comparison of PCA‐based statistical process monitoring
           methods for high‐dimensional, time‐dependent processes
    • Authors: Tiago Rato; Eric Schmitt, Bart De Ketelaere, Mia Hubert, Marco Reis
      Abstract: High‐dimensional and time‐dependent data pose significant challenges to Statistical Process Monitoring (SPM). Most of the high‐dimensional methodologies to cope with these challenges rely on some form of Principal Component Analysis (PCA) model, usually classified as non‐adaptive and adaptive. Non‐adaptive methods include the static PCA approach and Dynamic PCA for data with autocorrelation. Methods, such as Dynamic PCA with Decorrelated Residuals, extend Dynamic PCA to further reduce the effects of autocorrelation and cross‐correlation on the monitoring statistics. Recursive PCA and Moving Window PCA, developed for non‐stationary data, are adaptive. These fundamental methods will be systematically compared on high‐dimensional, time‐dependent processes (including the Tennessee Eastman benchmark process) to provide practitioners with guidelines for appropriate monitoring strategies and a sense of how they can be expected to perform. The selection of parameter values for the different methods is also discussed. Finally, the relevant challenges of modeling time‐dependent data are discussed, and areas of possible further research are highlighted. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-30T18:42:10.034627-05:
      DOI: 10.1002/aic.15062
       
  • Thermal Coupling Links to Liquid‐only Transfer Streams: An
           Enumeration Method for New FTC Dividing Wall Columns
    • Authors: Gautham Madenoor Ramapriya; Mohit Tawarmalani, Rakesh Agrawal
      Abstract: Novel dividing wall columns (DWCs) can be obtained by converting thermal couplings to liquid‐only transfer streams. Here, we develop a simple four‐step method to generate a complete set of DWCs containing n‐2 dividing walls, for a given n‐component fully thermally coupled (FTC) distillation. Among the novel DWCs, some easy‐to‐operate DWCs possess the property that the vapor flow in every section of the DWC can be controlled during operation by means that are external to the column. We develop a simple method to enumerate all such easy‐to‐operate DWCs. We expect that the easy‐to‐operate DWCs can be operated close‐to‐optimality; leading to a successful industrial implementation of the n‐component (n≥3) FTC distillation in the form of a DWC. As an illustration, we show figures of all easy‐to‐operate DWCs with two dividing walls for the four‐component FTC distillation. This article is protected by copyright. All rights reserved.
      PubDate: 2015-09-24T12:26:21.956674-05:
      DOI: 10.1002/aic.15053
       
  • In situ metal doping during modified anodization synthesis of Nb2O5 with
           enhanced photoelectrochemical water splitting
    • Authors: Chenyan Hu; Wey Yang Teoh, Shulin Ji, Changhui Ye, Akihide Iwase
      Pages: 352 - 358
      Abstract: A new technique of in situ doping of alkali metal (Li+, Na+, K+, Rb+, and Cs+) in Nb2O5 was showcased by the modified anodization of Nb foils at high frequency, negative‐to‐positive pulsed voltage. At the optimized dopant concentration and synthesis condition, the doped‐Nb2O5 shows twofold enhancement in photoelectrochemical water splitting efficiencies compared with the undoped Nb2O5 electrode, as a result of improved charge carrier density and enhanced surface charge transfer. © 2015 American Institute of Chemical Engineers AIChE J, 62: 352–358, 2016
      PubDate: 2015-10-01T11:16:10.712047-05:
      DOI: 10.1002/aic.15048
       
  • A concept of reactive compatibilizer‐tracer for studying reactive
           polymer blending processes
    • Pages: 359 - 366
      Abstract: A concept called reactive compatibilizer‐tracer is proposed. The latter bears reactive groups capable of reacting with its counterpart on forming a copolymer for in situ compatibilization, and fluorescent labels allowing determining very small amounts of the in situ formed compatibilizer and formation of micelles when it occurs. Owing to this concept, it is shown that a reactive compatibilizer may be very efficient at the beginning of a reactive blending process and may suddenly become completely inefficient, resulting in an abrupt and drastic increase in size of the dispersed phase domains. © 2015 American Institute of Chemical Engineers AIChE J, 62: 359–366, 2016
      PubDate: 2015-10-28T10:19:44.865041-05:
      DOI: 10.1002/aic.15074
       
  • Chemical nature of active sites for defect‐mediated nucleation on
           silicon dioxide
    • Authors: Joseph M. McCrate; John G. Ekerdt
      Pages: 367 - 372
      Abstract: Germanium nanoparticle growth on SiO2 proceeds via defect‐mediated nucleation and particle density can be enhanced by chemically treating the SiO2 with SiHx. The influence of SiHx fragments on SiO2 surface sites is studied using a fluorescent probe‐based technique to understand the chemical nature of the inherent defect trapping sites and the chemical nature of the additional trapping sites formed by SiHx. Oxygen‐vacancy sites on SiO2 are the inherent sites for defect‐mediated nucleation. SiHx fragments, generated by cracking disilane on a hot tungsten filament, are shown to react with strained siloxane sites, leading to a conversion of these strained siloxane sites into a different low density defect site that is shown to display reactive characteristics similar to the oxygen‐vacancy defect sites. Previous work demonstrating an increased density of Ge nuclei on SiO2 surfaces with increasing SiHx exposure is interpreted in the context of the current experimental results. © 2015 American Institute of Chemical Engineers AIChE J, 62: 367–372, 2016
      PubDate: 2015-09-14T12:46:41.924459-05:
      DOI: 10.1002/aic.15023
       
  • Continuous synthesis of palladium nanorods in oxidative segmented flow
    • Authors: Victor Sebastian; Soubir Basak, Klavs F. Jensen
      Pages: 373 - 380
      Abstract: Laminar and segmented flow methods are presented for producing Pd rod‐shaped nanostructures from Na2PdCl4 in mixtures of water, ethylene glycol, polyvinyl pyrrolidone, and KBr. Synthesis in laminar flow produced an evolution from Pd nanoparticles to short nanorods with residence time. Use of air as the segmentation gas tuned the oxidative environment promoting anisotropic growth of Pd. Moreover, the elevated temperatures (160°C and 190°C) and pressure (0.8 MPa) reduced the synthesis time from hours for most batch systems to 2 min. The ratio of polyol and Pd precursor metal flow streams controlled the anisotropic growth, obtaining nanorods with a diameter approximately 4 nm and an aspect ratio up to 6. Nanorods were single crystal with the {100} lattice spacing of fcc structure, and without any dislocation, stacking fault, or twin defects. The resulting Pd nanorods had high activity at moderate temperature (40ºC) and pressure (0.2 MPa) in the catalytic hydrogenation of styrene. © 2015 American Institute of Chemical Engineers AIChE J, 62: 373–380, 2016
      PubDate: 2015-09-23T14:35:25.478198-05:
      DOI: 10.1002/aic.15029
       
  • The role of microexplosions in flame spray synthesis for homogeneous
           nanopowders from low‐cost metal precursors
    • Pages: 381 - 391
      Abstract: One of the most versatile and rapid manufacturing processes for a variety of nanopowders is flame spray pyrolysis (FSP). The production costs of this scalable process are largely controlled by the raw materials, pushing for the utilization of low‐cost metal precursors. These, however, typically yield inhomogeneous products containing large particles up to micrometer size along with fine nanoparticles. Here, the release mechanism of nitrate and carboxylate precursors from spray droplets has been investigated by single‐droplet combustion experiments and thermogravimetric analysis. The results show that neither precursor evaporation nor choice of solvents is prerequisite for homogeneous nanopowders but droplet microexplosions with continuing combustion. It is shown that even low‐cost metal nitrates yield homogeneous nanopowders if precursors are formulated such that droplet microexplosions occur by internal superheating. The proposed precursor release mechanisms are verified with lab‐ and pilot‐scale FSP, demonstrating that single‐droplet combustion experiments can be employed to predict the product quality. © 2015 American Institute of Chemical Engineers AIChE J, 62: 381–391, 2016
      PubDate: 2015-10-01T10:57:05.329971-05:
      DOI: 10.1002/aic.15056
       
  • Engineering uniform nanocrystals: Mechanism of formation and
           self‐assembly into bimetallic nanocrystal superlattices
    • Pages: 392 - 398
      Abstract: The preparation of metal nanocrystals (NCs) with precise and tunable size is of great interest for many applications. Following previous reports on the synthesis of monodisperse nickel, palladium, and platinum NCs, we here show that the narrow size distributions are the result of an optimized combination of surfactants that play a dynamic, synergistic role in stabilizing the particles at different stages (nucleation, growth) of their preparation. This dynamical process allows the temporal separation of nucleation and growth responsible for the narrow size distributions achievable with this heat‐up method. Finally, the uniform NCs are exploited in the preparation of binary nanocrystals superlattices entirely based on metal components, with promising applicability in the fields of catalysis, sensing, and optics. © 2015 American Institute of Chemical Engineers AIChE J, 62: 392–398, 2016
      PubDate: 2015-10-14T15:43:52.826082-05:
      DOI: 10.1002/aic.15063
       
  • In situ ETEM study of composition redistribution in Pt‐Ni octahedral
           catalysts for electrochemical reduction of oxygen
    • Pages: 399 - 407
      Abstract: Dynamics of thermally induced composition redistribution of sandwich‐like Pt‐Ni octahedral electrocatalysts was studied in situ using a variable‐temperature environmental transmission electron microscope (ETEM). Dislocations were observed and on heating treatment moved toward the surface over time, resulting in an alloy nanoparticle with significant increase Ni content on the surface, which was confirmed by X‐ray photoelectron spectroscopy. The thermally treated Pt‐Ni octahedral catalysts showed significant improvement in catalyzing oxygen reduction reaction over the as‐made nanoparticles, reaching values of 1.4 A/mgPt in mass activity and 4.8 mA/ cmPt2 in area specific activity. Our study shows the important effect of postsynthesis treatment on the optimization of Pt and Ni atomic distribution, thus the catalytic activity and stability; and the power of in situ ETEM in understanding the structural origin of enhanced catalytic performance with atomic level of details. © 2015 American Institute of Chemical Engineers AIChE J, 62: 399–407, 2016
      PubDate: 2015-10-15T15:02:12.817533-05:
      DOI: 10.1002/aic.15070
       
  • Morphology‐dependent electrocatalytic activity of nanostructured
           Pt/C particles from hybrid aerosol–colloid process
    • Authors: Ratna Balgis; Aditya F. Arif, Takahiro Mori, Takashi Ogi, Kikuo Okuyama, Gopinathan M. Anilkumar
      Pages: 440 - 450
      Abstract: An optimum nanostructure and pore size of catalyst supports is very important in achieving high catalytic performances. In this instance, we evaluated the effects of various carbon nanostructures on the catalytic performances of carbon‐supported platinum (Pt/C) electrocatalysts experimentally and numerically. The Pt/C catalysts were prepared using a hybrid method involving the preparation of dense, hollow, and porous nanostructured carbon particle via aerosol spray pyrolysis followed by microwave‐assisted Pt deposition. Electrochemical characterization of the catalysts showed that the porous Pt/C catalyst gave the best performance; its electrochemical surface area was much higher, more than twice than those of hollow or dense Pt/C. The effects of pore size on electrocatalysis were also studied. The results showed the importance of a balance between mesopores and macropores for effective catalysis with a high charge transfer rate. A fluid flow model showed that good oxygen transport contributed to the catalytic activity. © 2015 American Institute of Chemical Engineers AIChE J, 62: 440–450, 2016
      PubDate: 2015-10-02T14:28:27.878894-05:
      DOI: 10.1002/aic.15059
       
  • Thermally induced phase separation and electrospinning methods for
           emerging membrane applications: A review
    • Authors: Jeong F. Kim; Ji Hoon Kim, Young Moo Lee, Enrico Drioli
      Pages: 461 - 490
      Abstract: In this review, thermally induced phase separation (TIPS) and electrospinning methods for preparation of fluoropolymer membranes are assessed, particularly for the polyvinylidene fluoride (PVDF) and polyethylene chlorotrifluoroethylene membranes. This review focuses on controlling the membrane morphology from the thermodynamic and kinetic perspectives to understand the relationship between the membrane morphology and fabrication parameters. In addition, the current status of the nonsolvent induced phase separation (NIPS) method and the combined NIPS‐TIPS (N‐TIPS) method, which is a new emerging fabrication method, are discussed. The past literature data are compiled and an upperbound curve (permeability vs. tensile strength) is proposed for the TIPS‐prepared PVDF membranes. Furthermore, the key parameters that control and determine the membrane morphology when using the electrospinning method are reviewed. Exploiting the unique advantages of the electrospinning method, our current understanding in controlling and fine‐tuning the PVDF crystal polymorphism (i.e., β‐phase) is critically assessed. © 2015 American Institute of Chemical Engineers AIChE J, 62: 461–490, 2016
      PubDate: 2015-11-05T15:42:53.740963-05:
      DOI: 10.1002/aic.15076
       
  • Ultrathin carbon molecular sieve membrane for propylene/propane separation
    • Authors: Xiaoli Ma; Y. S. Lin, Xiaotong Wei, Jay Kniep
      Pages: 491 - 499
      Abstract: Ultrathin (down to 300 nm), high quality carbon molecular sieve (CMS) membranes were synthesized on mesoporous γ‐alumina support by pyrolysis of defect free polymer films. The effect of membrane thickness on the micropore structure and gas transport properties of CMS membranes was studied with the feed of He/N2 and C3H6/C3H8 mixtures. Gas permeance increases with constant selectivity as the membrane thickness decreases to 520 nm. The 520‐nm CMS membrane exhibits C3H6/C3H8 mixture selectivity of ∼31 and C3H6 permeance of ∼1.0 × 10−8 mol m−2 s−1 Pa−1. Both C3H8 permeance and He/N2 selectivity increase, but the permeance of He, N2, and C3H6 and the selectivity of C3H6/C3H8 decrease with further decrease in membrane thickness from 520 to 300 nm. These results can be explained by the thickness‐dependent chain mobility of the polymer film which yields thinner final CMS membranes with reduction in pore size and possible closure of C3H6‐accessible micropores. © 2015 American Institute of Chemical Engineers AIChE J, 62: 491–499, 2016
      PubDate: 2015-08-31T11:47:03.919881-05:
      DOI: 10.1002/aic.15005
       
  • Defect engineering in semiconducting oxides: Control of ZnO surface
           potential via temperature and oxygen pressure
    • Authors: Ming Li; Edmund G. Seebauer
      Pages: 500 - 507
      Abstract: The technological usefulness of a semiconductor often depends on the types, concentrations, charges, spatial distributions, and mobilities of the atomic‐scale defects it contains. For semiconducting metal oxides, defect engineering is relatively new and involves complex transport and reaction networks. Surface‐based methods hold special promise in nanostructures where surface‐to‐volume ratios are high. This work uses photoreflectance augmented by X‐ray photoelectron spectroscopy to show that the surface potential VS for Zn‐terminated ZnO(0001) can be manipulated over a significant range 54.97–79.08 kJ/mol (0.57–0.82 eV) via temperature and the partial pressure of O2. A defect transport model implies this variation in VS should affect the injection rate of oxygen interstitials by a factor of three. Such injection plays an important role in controlling the concentrations of oxygen vacancies deep in the bulk, which often prove troublesome as trapping centers in photocatalysis and photovoltaics and as parasitic emitters in light‐emitting devices. © 2015 American Institute of Chemical Engineers AIChE J, 62: 500–507, 2016
      PubDate: 2015-09-21T11:59:37.358904-05:
      DOI: 10.1002/aic.15031
       
  • Formation and stability of string phase in polyamide 6/polystyrene blends
           in confined flow: Effects of nanoparticles and blend ratio
    • Authors: Miqiu Kong; Yajiang Huang, Yadong Lv, Qi Yang, Guangxian Li
      Pages: 564 - 573
      Abstract: Influences of silica nanoparticles on the microstructural evolution of polyamide 6 (PA6)/polystyrene (PS) blends with varying blend ratios were investigated in confined shear flow. Hydrophilic silica nanoparticles were found to promote the formation of PA6 strings with excellent shape stability during shearing. It was ascribed to the promoted coalescence of PA6 droplets induced both by the significantly increased droplet viscoelasticity and confinement, and the reduced interfacial tension by adding silica nanoparticles. Additionally, the width and aspect ratio of droplets obtained by experiments were compared with the predictions of Maffettone–Minale, Minale, Shapira‐Haber, MMSH, and modified M models. Good agreements were found in the droplet width in blends with low nanoparticle concentrations, whereas the experimental aspect ratio showed a negative deviation to model predictions, which was attributed to the enhanced droplet viscoelasticity and the omitted droplet orientation angle in these models. © 2015 American Institute of Chemical Engineers AIChE J, 62: 564–573, 2016
      PubDate: 2015-10-02T14:28:58.642114-05:
      DOI: 10.1002/aic.15058
       
  • Synergetic effect of graphene sheet and three‐dimensional crumpled
           graphene on the performance of dye‐sensitized solar cells
    • Pages: 574 - 579
      Abstract: Herein, an improved structure of the dye‐sensitized solar cell (DSSC) is demonstrated which is composed of surface modified fluorine‐doped tin oxide (FTO) glass with graphene (GR) sheets and TiO2 films incorporated with three‐dimensional crumped graphene (3‐D CGR)/GR sheets. The morphologies of the as‐prepared GR sheets on FTO glasses and 3‐D CGR/GR sheets/TiO2 films were observed by field‐emission scanning electron microscopy. Light harvesting and charge recombination kinetics were investigated with a solar simulator and electrochemical impedance spectroscopy analysis. In addition to the reduced charge resistance by the GR modified FTO, the enhanced dye loading capability of the 3‐D CGR, and the rapid charge transport by the 2‐D GR sheets, the power conversion efficiency was 7.2%, which was an increase of 56% compared to a “conventional” structured DSSC. © 2015 American Institute of Chemical Engineers AIChE J, 62: 574–579, 2016
      PubDate: 2015-11-13T13:31:22.835799-05:
      DOI: 10.1002/aic.15089
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2015