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Journal Cover Catalysis Today
  [SJR: 1.378]   [H-I: 142]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2970 journals]
  • Direct numerical simulation for flow and heat transfer through random
           open-cell solid foams: Development of an IBM based CFD model
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Saurish Das, Niels G. Deen, J.A.M. Kuipers
      In the present contribution a sharp interface Immersed Boundary Method (IBM) for flow and heat transfer has been developed to fully resolve highly complex random solid structure on a non-body fitted Cartesian computational grid. A 3D image data set from a Micro-CT (computed tomography) scan of an actual foam geometry is usually converted into a surface mesh of unstructured triangular elements and the current frame work can embed it as an immersed boundary in the CFD domain. A second-order implicit (semi-implicit) method is used to incorporate fluid-solid coupling for flow (heat transfer) at the non-conforming immersed boundary in a structured grid. Both temperature Dirichlet and Neumann boundary conditions, as well as a conjugate heat transfer condition are incorporated at the fluid–solid interface. The proposed method is validated rigorously with existing literature results. The use of a Cartesian grid for flow makes this method robust, computational friendly, and at the same time it avoids the tedious volumetric mesh generation process for very complex shapes. To demonstrate the capability of the current method, it is applied to study flow and heat transfer of a typical foam sample with different flow properties. A closure for pressure drop and heat transfer coefficient are derived for the typical foam sample.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Effect of the thermal conductivity of metallic monoliths on methanol steam
           reforming
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Oihane Sanz, Ion Velasco, Inés Reyero, Iñigo Legorburu, Gurutze Arzamendi, Luis M. Gandía, Mario Montes
      We have studied the influence of cell density of two sets of metal monoliths coated with different amounts of Pd/ZnO in the methanol steam reforming (MSR). The results indicate that the conversion increases with increasing size of the channels that is accompanied by a decrease in the monoliths cell density. To explain this unexpected result, the longitudinal and radial temperature profiles were measured. It was observed that the thermal conductivity increased with increasing cell density and temperature profiles became more marked with increasing catalyst loading on the monolith. This last result was explained by the increase of the heat required for the reaction to maintain a constant space velocity. Being fixed central temperature of the monolith and being the MSR an endothermic reaction, the average temperature increases with decreasing thermal conductivity. To assess whether this increase in average temperature justifies the observed increase in conversion, a CFD modeling of the system was performed. The simulation results showed an excellent agreement with experimental values. This confirms the fundamental role of thermal conductivity, which is mainly controlled by the cell density of the monolith.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Copper-catalyzed conversion of aryl and heteroaryl bromides into the
           corresponding iodide
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Xiujuan Feng, Lingyu Li, Xiaoqiang Yu, Yoshinori Yamamoto, Ming Bao
      An efficient method for the synthesis of aryl and heteroaryl iodides is described in this study. The reactions of aryl and heteroaryl bromides with potassium iodide proceeded smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding iodides in satisfactory to excellent yields.
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      PubDate: 2016-06-12T23:08:33Z
       
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273




      PubDate: 2016-06-12T23:08:33Z
       
  • Contents list
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273




      PubDate: 2016-06-12T23:08:33Z
       
  • Modelling and simulations of a monolith reactor for three-phase
           hydrogenation reactions — Rules and recommendations for mass
           transfer analysis
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Freddy L. Durán Martínez, Carine Julcour, Anne-Marie Billet, Faïçal Larachi
      A strategy for the scale-up of a monolith reactor dedicated to gas-liquid catalytic reactions is worked out; focus is made on the crucial step of gas-liquid mass transfer modelling via a steady-state numerical study based on a single channel and single unit cell representation, using a frame moving with the bubble and solving the liquid phase only. The relevance of this simplified approach is assessed through a specific case (given bubble shape, channel diameter and fluid flow rates), and hydrodynamics as well as mass transfer results are successfully compared to previously published numerical, semi-analytical and experimental works. Influence of unit cell length and of catalytic surface reaction rate is thoroughly investigated. Inferred overall mass transfer coefficients are found to increase with bubble frequency, due to higher interfacial area in unit cell and intensified recirculation in slug. Film contribution to mass transfer is usually found dominant in the case of short bubbles with reactive wall, and hardly varies with reaction rate. However, this contribution is strongly linked to bubble frequency, and a reliable evaluation of local mass transfer by correlations demands accurate knowledge on the precise dimensions of bubble, slug and film entities.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Effect of diffusion limitation on the performance of multi-layer oxidation
           and lean NOx trap catalysts
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Marek Václavík, Vladimír Novák, Jan Březina, Petr Kočí, Gregory Gregori, David Thompsett
      Recent effort in emission control catalyst development aims for saving space and cost by combining different catalytic functions in a single multi-layered monolith reactor. However, the overall efficiency of the converter and particularly the bottom layer performance can be negatively affected by transport limitations. This work investigates transport limitation in double-layer systems consisting of oxidation (DOC) and lean NOx trap (LNT, NOx storage) catalysts. CO/HC oxidation and NOx storage/reduction experiments were carried out in a laboratory reactor. The LNT coating in the tested samples was overlaid with an additional layer that was either inert (γ-Al2O3) or catalytically active (DOC). The inert layer served as a diffusion barrier with no catalytic activity to decouple the transport and reaction effects. The hindered transport affected both NOx storage (less efficient initial NOx uptake) and NOx reduction (changes in the selectivity, longer delay of NH3 breakthrough, shift of N2O formation from primary to secondary peak). The presence of DOC layer on the top of LNT improved the catalytic performance at lower temperatures by increasing the effective NOx storage capacity (due to NO oxidation activity) and improved regeneration efficiency (due to water gas shift, steam reforming and NH3 re-oxidation).
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      PubDate: 2016-06-12T23:08:33Z
       
  • Study on compositions and changes of SEI film of Li2MnO3 positive material
           during the cycles
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Meng Cheng, Weiping Tang, Yong Li, Kongjun Zhu
      In this article, we investigated the surface series of Li2MnO3 electrodes and the composition variation of the SEI film. XPS and FT-IR analysis indicated the compositions of a primary SEI film, containing about 20at.% LiF, varied upon cycling including the dissolution of LiF and the accumulation of LixPOyFz and organic species, accompanied by surface corrosion. Whereas organic species showed minor change by the static corrosion. The unstable passive film caused high impedance and could not restrain the electrolyte corrosion in both dynamic and static process.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Synthesis of nanostructured tungsten carbonitride (WNxCy) by carbothermal
           ammonia reduction on activated carbon and its application in hydrazine
           decomposition
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Jun Sun, Binglian Liang, Yanqiang Huang, Xiaodong Wang
      A carbothermal NH3 reduction method was introduced for the synthesis of nanostructured tungsten carbonitride using support carbon and NH3 as carbon source and nitrogen source, respectively. A series of samples synthesized by this route from WO3/AC were characterized by X-ray diffraction, temperature-programmed surface reaction-mass spectroscopy, transmission electron microscopy, and microcalorimetry. The results demonstrated that a nanostructured tungsten carbonitride (WN x C y ) was successfully synthesized on activated carbon at 800°C and the resulting WN x C y was uniformly dispersed on the carbon support with particle size less than 2nm. The WN x C y /AC prepared by the carbothermal NH3 process has stronger capability for CO adsorption and exhibited better catalytic performance for hydrazine decomposition than the WC x /AC-H catalyst prepared by the carbothermal H2 reduction process. Further bench-scale tests indicated that it could be a promising substitute for the traditional Ir/Al2O3 catalyst in hydrazine decomposition technology.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Ethylene epoxidation in microwave heated structured reactors
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Adrián Ramírez, José L. Hueso, Reyes Mallada, Jesús Santamaría
      In the present work we show the microwave-induced heating of monolithic reactors containing a thin-layered catalyst that exhibits a strong and selective heating susceptibility under microwave irradiation. The combination of microwave radiation and structured reactors has been successfully applied for the intensification of the selective oxidation of ethylene to ethylene oxide (epoxidation) while operating at lower power consumptions and with higher energy efficiencies than in conventional heating conditions. The microwave radiation selectively heats the catalyst and the monolith walls while maintaining a relatively colder gas stream thereby creating a gas/solid temperature gradient of up to ∼70°C at a reaction temperature of 225°C. Moreover, the influence of different parameters such as the distribution of the catalyst onto the structured monoliths or the temperature measurement techniques employed to determine the heating profiles (Optic Fibers and/or IR thermography) have been also thoroughly evaluated to justify the obtained catalytic results.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Silicone microreactors for the photocatalytic generation of hydrogen
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Alejandra Castedo, Ernest Mendoza, Inmaculada Angurell, Jordi Llorca
      A silicone microreactor with 500μm-width microchannels coated with a Au/TiO2 photocatalyst was manufactured and tested for the photocatalytic generation of hydrogen from gaseous water-ethanol mixtures under dynamic conditions. The manufacture of the microreactor included the fabrication of a polylactic acid (PLA) mold with a 3D printer and casting with polydimethylsiloxane (PDMS) prepolymer. After curing, the silicone microreactor was peeled off and the microchannels were coated with a Au/TiO2 photocatalyst prepared by impregnation of preformed Au nanoparticles over TiO2, and sealed with a thin silicone cover. The microreactor was tested at room temperature and atmospheric pressure under different operational conditions (photon irradiance, residence time, photocatalyst loading, and water-ethanol ratio). Hydrogen production rates of 5.4 NmLW−1 h−1 were measured at a residence time of 0.35s using a H2O:C2H5OH molar ratio of 9:1, a photocatalyst load of 1.2mgcm−2 and a UV irradiance (365nm) of 1.5mWcm−2 achieving an apparent quantum efficiency of 9.2%. The photogeneration of hydrogen with commercial bioethanol was also tested. A long-term photocatalytic test of two days revealed a stable hydrogen photoproduction rate. The use of silicone microreactors represents an attractive and customizable solution for conducting photochemical reactions for producing hydrogen at low cost.
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      PubDate: 2016-06-12T23:08:33Z
       
  • In situ analysis of gas phase reaction processes within monolithic
           catalyst supports by applying NMR imaging methods
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Jürgen Ulpts, Wolfgang Dreher, Lars Kiewidt, Miriam Schubert, Jorg Thöming
      Measuring spatially resolved concentration distributions in gas phase reaction systems is an important tool to validate simulation calculations, improve the understanding of transport processes within the catalyst, and identify potentials for improvements of monolithic catalyst supports. The commonly used measurement methods for such opaque systems are invasive and, thus, might be misleading due to alteration of the system. To overcome this issue, a 3D magnetic resonance spectroscopic imaging (MRSI) method was developed and implemented on a 7-Tesla NMR imaging system to map the concentration distributions within opaque monolithic catalysts using the ethylene hydrogenation process as case study. The reaction was catalyzed by a coated sponge packing or a honeycomb monolith within an NMR compatible packed bed reactor. Temperatures at the inlet and the outlet of the catalyst beds were simultaneously determined by analyzing the spectra of inserted ethylene glycol filled glass capsules. Steady state concentration profiles and temperature levels were measured at different reaction conditions. In order to prove the plausibility of the measured spatial distributions of compound concentrations, the experimental results were compared to a 1D model of the reactor based on kinetic data from literature. Furthermore, a comparison with integral concentration measurements using a mass spectrometer demonstrated deviations below 5%. The results show that 3D MRSI is a valuable and reliable tool to non-invasively measure spatially resolved process parameters within optically and/or mechanically inaccessible structured monolithic catalyst supports, even if only standard thermal polarization is exploited and the use of expensive and technically challenging signal enhancement techniques (hyperpolarization) is avoided. We expect that 3D MRSI can pave the way toward deeper insight into the interactions between catalyst, catalyst support, and gas phase.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Open cell foam catalysts for CO2 methanation: Presentation of coating
           procedures and in situ exothermicity reaction study by infrared
           thermography
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Myriam Frey, Thierry Romero, Anne-Cécile Roger, David Edouard
      The carbon dioxide methanation reaction is highly exothermal (ΔRH=−165kJmol−1). It is therefore essential to use processes able to control and efficiently evacuate the heat generated during the reaction. In this paper, a structured bed filled with an open cell foam was chosen due to the many advantages of this kind of reactor (high surface/volume ratio, low pressure drop, intensification of mass and heat transfer…). Three kind of open cell foams, with different thermal properties, were studied: SiC, Alumina and Aluminium. Coating procedures of a methanation catalyst (Ni/Ceria-Zirconia) developed in previous work for SiC open cell foams were adapted to alumina and aluminium open cell foams. For the first time, in situ infrared thermography was used to study the exothermicity of the reaction on the surface of different foams.
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      PubDate: 2016-06-12T23:08:33Z
       
  • On the Cu species in Cu/beta catalysts related to DeNOx performance of
           coupled NSR-SCR technology using sequential monoliths and dual-layer
           monolithic catalysts
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Unai De La Torre, Maitane Urrutxua, Beñat Pereda-Ayo, Juan R. González-Velasco
      Cu/beta catalysts are prepared starting from protonic or ammonic BEA zeolite following liquid ion exchange with copper. Alternatively, an intermediate ion exchange with Na ions is performed before copper ion exchange. Cu/beta catalysts are extensively characterized by XRF, N2 adsorption–desorption, FT-IR of NO and CO adsorption, EPR, H2-TPR, TEM and SEM in order to identify copper oxidation state (Cu+ or Cu2+) and copper species (agglomerated or Cu ions with different interaction with the support). Cu/beta catalyst prepared from ammonic BEA zeolite with intermediate Na ion exchange followed by copper ion exchange results in the most active catalyst in the NH3-SCR reaction, which is related to the coexistence of Cu+ and Cu2+ ions and to a more accessible location of such ions in the zeolite matrix. This catalyst is washcoated onto a monolithic substrate with an optimum loading of 0.32 g cm−3, in order to be placed downstream a NOx storage and reduction (NSR) monolithic catalyst, prepared by washcoating Pt-Ba/Al2O3 powder with an optimum loading of 0.25gcm−3. NSR-SCR catalyst in sequential beds results in a very active system with a NOx removal of 97% and a N2 selectivity of 96% at 275°C. NSR/SCR catalyst prepared in a unique dual layer device shows that top SCR layer loading can be tuned in order to improve DeNOx performance. Optimum SCR layer loading is observed for 0.02gcm−3, enhancing the NOx to N2 efficiency of single NSR catalyst but far away from the catalytic performance observed for the sequential NSR-SCR configuration.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Microfibrous entrapped hybrid iron-based catalysts for
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Xinquan Cheng, Hongyun Yang, Bruce J. Tatarchuk
      Fischer–Tropsch synthesis (FTS) is a highly exothermic reaction, and a FTS reactor must have an efficient heat transfer mechanism in order to maintain a stable reaction temperature. Copper microfibrous entrapped catalyst (Cu MFEC) has demonstrated an excellent intra-bed heat transfer ability for FTS thermal management. The porous structure of Cu MFEC can entrap any pre-manufactured catalyst particles, while its counterpart approaches such as metallic foams or monolith reactor structures are typically based on washcoating process and require the details about catalyst formulation and preparation procedure to proceed. In this investigation, a highly active and stable iron-based FTS (Fe-FTS) catalyst, i.e. iron supported on γ-alumina and promoted with copper and potassium, has been developed. The apparent reaction rate constant of Fe-FTS and its productivity at 27.7% of CO conversion are 167mmol (H2 +CO)/gcat/h and 0.30gC5+/gcat/h, respectively, which are comparable to the most active unsupported Fe-based catalyst. When Fe-FTS was physically mixed with equal mass of mesoporous aluminosilicate (MAS) loaded with 0.3wt% Pt, a hybrid catalyst was formed. This hybrid catalyst demonstrated an extremely low CO2 selectivity (27.7 C%) and a very high selectivity (38.1 C%) to liquid products (C5–C20). The result suggested that FTS and hydrocracking process simultaneously took place within a single reactor. Furthermore, FTS was carried out in a larger tubular reactor (34.0mm I.D.) packed with Cu MFEC. It demonstrated a radial temperature gradient less than 5°C and similar reactivity and product selectivity as those obtained in a small FTS reactor (9.5mm I.D.). While with the same catalyst loading density and the same test conditions, the comparative packed bed (34.0mm I.D.) reached radial temperature gradient around 54°C. It was also found that the FTS based Cu MFEC required negligible amount of time to reach its steady state compared with the packed bed. With these attributes and advantages, Cu MFEC approach is a promising alternative to the traditional packed bed for exothermic reactions such as FTS.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Carbon nano-fiber based membrane reactor for selective nitrite
           hydrogenation
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Roger Brunet Espinosa, Damon Rafieian, Rob G.H. Lammertink, Leon Lefferts
      Catalytic hydrogenation of nitrite in drinking water demands control over the selectivity towards nitrogen, minimizing the formation of ammonia. This selectivity is strongly influenced by the H/N ratio of reaction intermediates at the catalyst surface. Therefore, we fabricated a membrane reactor that feeds separately hydrogen gas and a nitrite solution. This allows dosing low but homogeneous hydrogen concentrations along the axial direction of the catalyst bed. As a consequence, low H/N ratios can be achieved, favouring the formation of nitrogen without limiting the nitrite conversion. We demonstrate that this reactor concept offers better nitrogen selectivity than conventional reactor configurations where hydrogen is pre-dissolved in the nitrite solution.
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      PubDate: 2016-06-12T23:08:33Z
       
  • The delaminating and pillaring of MCM-22 for Fischer–Tropsch
           synthesis over cobalt
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Qing-Qing Hao, Chun-Yan Lei, Yong-Hong Song, Zhao-Tie Liu, Zhong-Wen Liu
      To investigate the effect of structural evolution of layered zeolite on the performance of Co/MCM-22 derived zeolites for Fischer–Tropsch (FT) synthesis, the MCM-22, MCM-36 and delaminated zeolite characterized by different arrangement of MWW nanosheets were prepared through directly calcination, pillaring and delaminating of the layered precursor of the MCM-22 (MCM-22(P)). The results show that the extent of reduction of cobalt was increased over Co-supported pillared and delaminated zeolites, and the activities of the catalysts (i.e., CO conversions) were increased in the order of Co/MCM-22<Co/Al2O3–MCM-36<Co/SiO2–MCM-36<Co/delaminated zeolite. Compared to Co/MCM-22, the selectivity of CH4 over Co-supported pillared and delaminated zeolites was decreased clearly. Moreover, Co-supported SiO2–MCM-36 and Al2O3–MCM-36 can effectively narrow the product distribution of FT synthesis showing clearly increased C4–C12 selectivity. However, the selectivity of C21+ hydrocarbons over Co/delaminated zeolite was significantly increased. The results are well explained based on the structural and acidic properties of the MCM-22 derived zeolites together with the reduction behaviors of the catalysts.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Growth of carbonaceous nanomaterials over stainless steel foams. Effect of
           activation temperature
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): N. Latorre, F. Cazaña, V. Sebastian, C. Royo, E. Romeo, M.A. Centeno, A. Monzón
      Some of the problems that occur during the operation of chemical reactors based of structured catalytic substrates, as monoliths, foams, membranes, cloths, fibres and other systems, are related to the preparation of long term stable coatings. Frequently, the deposition of the catalytic layer is carried out by washcoating, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths. In the case of the deposition of layers of carbonaceous materials (CNMs), an alternative route, avoiding the washcoating, it is their direct growth by catalytic decomposition light hydrocarbons (also called CCVD), over the surface of the metallic substrate. In this case, if the metallic substrate is of stainless steel, it already contains the catalytic active phases like Fe and Ni. In order to optimize the process of CNMs growth over structured metallic substrates, we are studying the effect of the main operational variables of the ethane decomposition reaction on stainless steel foams. In this contribution we present a study of the influence of the temperature of the activation (oxidation and reduction) stage on the type and morphology of the carbonaceous materials formed. The results obtained allow us to determine the optimal operating conditions to maximize the amount and the selectivity of the process to obtain a given type of CNM.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Monolithic catalysts with Pd deposited on a structured nickel foam packing
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Ya-Zhao Liu, Yong Luo, Guang-Wen Chu, Jian-Feng Chen
      Catalyst activity and selectivity of the multiphase catalytic reactions may be strongly reduced by mass transfer limitations. A rotating packed bed (RPB) reactor can intensify the mass transfer process by 1–3 orders magnitude compared to the traditional reactors, which has great potential for catalytic reactions. The first step of the RPB reactor applied to catalytic reactions is to prepare a monolithic catalyst with excellent mechanical strength. This work selected the structured nickel foam packing as the catalyst substrate and then deposited palladium on the surface of the porous nickel foam packing. The above monolithic catalyst was then characterized by FESEM, EDS, TEM, XRD, ICP, and 3D-CT. In order to know the coating adhesivity, the monolithic catalyst was tested by the ultrasonic vibration in an ultrasonicator tank and scouring experiments in a RPB reactor. Hydrogenation of α-methylstyrene was employed to test its catalytic performance.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Pd/CeO2 catalysts as powder in a fixed-bed reactor and as coating in a
           stacked foil microreactor for the methanol synthesis
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Xuyen Kim Phan, John C. Walmsley, Hamid Bakhtiary-Davijany, Rune Myrstad, Peter Pfeifer, Hilde Venvik, Anders Holmen
      Pd/CeO2 as a catalyst for methanol synthesis has been studied in a microreactor consisting of 14 structured foils in a fixed-bed laboratory reactor. Methanol synthesis was carried out at 80bar and 300°C with a syngas composition of H2/CO/CO2/N2 =65/25/5/5. It was found that Pd/CeO2 as a foil coating was more active than the Pd/CeO2 powder catalyst on a Pd/CeO2 mass basis, both initially and after stabilization. In order to understand the Pd/CeO2 catalyst properties, both as a coating on the structured foils and as nanoparticles, techniques such as TEM, SEM, XRD and chemisorption were employed to characterize the catalysts before and after reaction experiments. The activity of the Pd/CeO2 foil coating is substantially better than the Pd/CeO2 powder despite significantly higher Pd dispersion of the Pd/CeO2 powder. This is ascribed to the Pd nanoparticles of the powder catalyst being partly covered by the ceria upon preparation and reduction. This prevents the accessibility of Pd to the gaseous reactants. A higher number of active sites are initially present in both catalysts, leading to high initial activity for methane as well as methanol formation. This may be explained by good interfacial contact between Pd and CeO2 created during preparation and reduction to form sites that are gradually lost under reaction conditions by a combination of sintering/agglomeration and enhanced coverage of the Pd by ceria layers.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Structured Reactors as an Alternative to Fixed-bed Reactors: Influence of
           catalyst preparation methodology on the partial oxidation of ethanol
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Clarissa P. Rodrigues, Elka Kraleva, Heike Ehrich, Fabio B. Noronha
      This work studied the effect of the preparation of monolithic catalysts for partial oxidation of ethanol. Cordierite monoliths coated with 10Ni/CeSiOx catalyst were prepared by washcoating with two different binders (PVA and Ludox) and a direct sol–gel techniques. Scanning electron microscopy and transmission electron microscopy analyses and adherence tests revealed that structured washcoated monoliths prepared by the slurry with Ludox and direct synthesis using citrate method exhibited excellent dispersion and adherence of catalyst coatings. For the washcoated monolith obtained by slurry with PVA, large agglomerates of catalyst over the wall were observed. The tests with the monolith without catalyst revealed that POX of ethanol only takes place in the presence of the Ni-based catalysts. The monolith catalysts synthesized by slurry with Ludox and direct synthesis using citrate method exhibited a high formation of syngas. However, the preparation method of the monolithic catalysts affects product distribution at low temperature. The addition of Pt to the NiCeSiOx monolith catalyst synthesized by citrate method significantly improved the partial oxidation of ethanol reaction.
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      PubDate: 2016-06-12T23:08:33Z
       
  • 5th International Conference on Structured Catalysts and Reactors,
           ICOSCAR-5, Donostia-San Sebastián, Spain, 22–24 June, 2016
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Luis M. Gandía, Mario Montes, José Antonio Odriozola



      PubDate: 2016-06-12T23:08:33Z
       
  • Preparation of structured catalysts with Ni and Ni–Rh/CeO2 catalytic
           layers for syngas production by biogas reforming processes
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): C. Italiano, R. Balzarotti, A. Vita, S. Latorrata, C. Fabiano, L. Pino, C. Cristiani
      Ni(7.5wt.%)/CeO2 and Ni(7.5wt.%)-Rh(0.5wt.%)/CeO2 powders (previously prepared by solution combustion synthesis) were washcoated on cordierite monolith and alumina open-cell foam by means of support dip-coating into acid-free catalyst dispersion. Catalytic performances toward the steam reforming (SR) and the oxy-steam reforming (OSR) of biogas were investigated and compared at different temperatures (700–800°C) and weight space velocities (WSV=70,000–350,000Nmlgcat −1 h−1). Coating load was controlled by multiple depositions; homogeneous and well adherent layers were found. Catalytic tests demonstrated superior performances of the bimetallic samples (Ni–Rh/CeO2) compared to the monometallic one (Ni/CeO2), especially at high space velocity. At the same time, foam showed better performances with respect to the monolithic support toward the SR and OSR processes.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Tuning shape of three dimensional graphene sheets
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Hui Wang, Wei Wei, Yun Hang Hu
      3D graphene has been explored as an important material and catalyst for many applications. However, it is still a challenge to tune the shape of 3D graphene sheets. Herein, it is demonstrated that the shapes of 3D graphene sheets, which were synthesized from the reaction between Li2O and CO, are strongly dependent on the particle size of Li2O. When Li2O particle size was very small (about 400nm), the formed graphene sheets possessed a granulated shape. However, as Li2O particle size increased, the shape of the synthesized graphene sheets changed to flower-structure and then to honeycomb-structure. Furthermore, the shape change of graphene from the granulated to the honeycomb-structured can increase its electro-catalytic efficiency as a counter electrode catalyst for dye-sensitized solar cells (DSSCs).
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      PubDate: 2016-06-12T23:08:33Z
       
  • A DFT-based study of surface chemistries of rutile TiO2 and SnO2(110)
           toward formaldehyde and formic acid
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Miru Tang, Zhenrong Zhang, Qingfeng Ge
      Rutile TiO2 and SnO2 are two structurally similar metal oxides found applications in catalysis and solid-state sensory devices as well as optics and electronics. In present work, we studied the adsorption and conversion of formaldehyde and formic acid on the (110) surfaces of rutile TiO2 and SnO2 based on density functional theory computational results. As oxygen vacancy is one of the most important and common defects on these metal oxides, the effect of the oxygen vacancy on adsorption and transformation were also examined. The results show that the adsorption of formaldehyde and formic acid resulted in similar adsorption configurations on SnO2(110) and TiO2(110). On the stoichiometric surface, SnO2 exhibits a stronger binding toward the adsorbates than TiO2. On the other hand, TiO2(110) with one bridge-bonded oxygen vacancy shows a stronger binding toward the adsorbates than SnO2(110) with the same type of defects. The bridge-bonded oxygen vacancy played important roles in adsorption and conversion and the Vo-bidentate formate species is the key intermediate in the oxidation of formaldehyde to formic acid. TiO2(110) has a higher activity than SnO2(110) for the reactions examined herein.
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      PubDate: 2016-06-12T23:08:33Z
       
  • A sustainable process for the production of 2-methyl-1,4-butanediol by
           hydrogenation of biomass-derived itaconic acid
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Xiaoran Liu, Xicheng Wang, Qiang Liu, Guoqiang Xu, Xuemin Li, Xindong Mu
      Pd–ReOx/C catalysts with different Re contents were prepared and employed to catalyze the aqueous hydrogenation of itaconic acid in this study. The Pd–ReOx/C catalysts were characterized by XRD, TEM, BET, NH3-TPD and H2-TPR. Results showed that the addition of ReOx species in supported Pd catalysts promoted the direct conversion of itaconic acid to 2-methyl-1,4-butanediol. The promoting effect was ascribed to the interaction between Pd and ReOx species, as has been proved by the characterizations. A 2-methyl-1,4-butanediol yield of above 80% could be obtained over Pd–3ReOx/C under the reaction condition of 180°C, 4MPa H2.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Highly selective hydrothermal production of cyclohexanol from
           biomass-derived cyclohexanone over Cu powder
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Zhiyuan Song, Dezhang Ren, Tian Wang, Fangming Jin, Qianhui Jiang, Zhibao Huo
      An efficient conversion of biomass-derived cyclohexanone to cyclohexanol by in situ-formed hydrogen over Cu catalyst under hydrothermal conditions was reported at first. Among the catalysts tested, Cu exhibited high catalytic activity for the conversion of cyclohexanone, and the highest yield of 100% was obtained when Zn acted as reductant. The experiment was carried out by using gaseous hydrogen as the external hydrogen source indicated that the yield of 75.1% was lower than in situ-formed hydrogen by oxidation of Zn in water. The present study provides an efficient route by environmentally benign, commercially available Cu powder as a catalyst for cyclohexanone conversion to cyclohexanol.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Wells–Dawson type Cs5.5H0.5P2W18O62 based Co/Al2O3 as binfunctional
           catalysts for direct production of clean-gasoline fuel through
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Chunling Wang, Xianni Bu, Jingwei Ma, Cheng Liu, Kuochih Chou, Xunli Wang, Qian Li
      Polyoxometalates (POMs) possess unique strong Brønsted acidity. However, little attentions were paid to the effect of POMs with respect to the hydrocracking. Herein we show that Wells–Dawson type POMs Cs5.5H0.5P2W18O62 (CsDP) combined with conventional Fischer–Tropsch catalyst Co/Al2O3 forming a highly efficient bifunctional catalyst for the direct production of clean gasoline from syngas. The Brønsted acidity of the CsDP results in hydrocracking of the heavier hydrocarbons formed on Co/Al2O3. The selectivity for the gasoline product could reach 48.8%, which has increased by 129% than that of conventional FTS catalyst. Furthermore, the catalytic performance of Wells–Dawson type POMs Cs5.5H0.5P2W18O62 and Keggin type POMs Cs2.5H0.5PW12O40 based catalyst is compared. The former exhibits higher CO conversion and C5–C12 selectivity than those of the Keggin type of Cs2.5H0.5PW12O40.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Activated carbons for the hydrothermal upgrading of crude duckweed bio-oil
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Peigao Duan, Caicai Zhang, Feng Wang, Jie Fu, Xiuyang Lü, Yuping Xu, Xianlei Shi
      This study examined a two-stage (noncatalytic pretreatment followed by catalytic upgrading) hydrothermal processing of crude bio-oil produced from the hydrothermal liquefaction of duckweed. The activities of six activated carbons (ACs)-pine wood AC, coconut shell AC, bamboo stem AC, apricot pit AC, peach pit AC, and coal AC-toward the deoxygenation and denitrogenation of the pretreated duckweed bio-oil were determined in supercritical water at 400°C for 1h with the addition of 6MPa of H2 and 10wt% AC. All of the ACs exhibited activity similar to Ru/C toward the denitrogenation and deoxygenation of the pretreated duckweed bio-oil. Of the ACs tested, bamboo stem AC produced an upgraded bio-oil with the highest yield (76.3wt%), the highest fraction (90.13%) of material boiling below 350°C, and the highest energy density (44.1MJ/kg). Decreased ash and acidic groups in the pre-treated AC disfavored the production of upgraded bio-oil but aided denitrogenation and desulfurization. The ACs are suspected to leach ions and weak acids into the reaction solution, which would catalyze denitrogenation and desulfurization. The gases mainly consisted of unreacted H2, CO2 and CH4 together with small amounts of C x H y (x ≤5, y ≤12) hydrocarbon gases produced from the cracking of the upgraded bio-oil.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Isomerization of glucose at hydrothermal condition with TiO2, ZrO2,
           CaO-doped ZrO2 or TiO2-doped ZrO2
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Haruyuki Kitajima, Yoshimasa Higashino, Shiho Matsuda, Heng Zhong, Masaru Watanabe, Taku M. Aida, Richard Lee Smith
      Catalytic activity of TiO2, ZrO2 and ZrO2 solid solutions (with CaO or TiO2) for the isomerization of glucose into fructose under hydrothermal conditions (120–180°C for 5–15min reaction time) was evaluated by experimental kinetic studies and surface acidity–basicity measurements. Kinetic studies were conducted with batch reactors heated by microwave. Under hydrothermal conditions regardless of the temperature, fructose yield was always below 10% and fructose selectivity was rapidly decreased with increasing glucose conversion. By adding 10mM NaOH, fructose yield reached 20% at 160°C for 5min. In the presence of TiO2, fructose yield and selectivity were similar (160°C, 47% of glucose conversion and 14% fructose yield). ZrO2 showed higher catalytic activity (160°C, 63% glucose conversion and 21% fructose yield) compared with TiO2. The catalytic activity of TiO2 doped ZrO2 was between TiO2 and ZrO2. To increase the basicity of ZrO2, CaO was doped into the ZrO2 matrix. For experiments with the 24wt% CaO doped ZrO2, fructose selectivity was higher than 70% even at 30% glucose conversion at 160°C for 15min. For systematical understanding catalytic activity of the metal oxides used, acidity and basicity of the catalysts were measured by temperature programmed desorption (TPD) using either CO2 or NH3. It was found that basicity on the surface increased with increasing the amount of CaO in the ZrO2 solid solution while acidity increased with amounts of TiO2. For a simple network model of glucose reactions, rate constants were fitted to the data assuming a simple network model and they were completed with the acid-base properties of TiO2, ZrO2 and CaO doped and TiO2 doped ZrO2. As a result, the reactivity was found to be correlated with the ratio of the base to acid sites on the surface and fructose formation was linearly proportional to the base/acid mole ratio on the surface of the catalysts.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Mesoporous H-ZSM-5 as an efficient catalyst for conversions of cellulose
           and cellobiose into methyl glucosides in methanol
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Laiqi Xue, Kang Cheng, Hongxi Zhang, Weiping Deng, Qinghong Zhang, Ye Wang
      The alcoholysis of cellobiose, which is a dimer of glucose and a model molecule of cellulose, has been studied in methanol medium in the presence of various solid acids. Zeolite H-ZSM-5 was found to be highly efficient for the conversion of cellobiose into methyl glucosides (including methyl-α-glucoside and methyl-β-glucoside) in methanol. The Brønsted acidity plays a key role in the catalytic alcoholysis of cellobiose. H-ZSM-5 with a lower Si/Al ratio (20) possessed higher density of acidic sites afforded a higher methyl glucoside yield (53%) for the conversion of cellobiose at 423K. The introduction of mesoporosity into the zeolite significantly enhanced its catalytic performance. Methyl glucosides with a yield of 73% were achieved from cellobiose over a mesoporous H-ZSM-5 (H-meso-ZSM-5-0.5M) sample with an average mesopore size of 6.1nm. The mesoporous ZSM-5 could also catalyze the direct transformation of cellulose in methanol, providing methyl glucosides with yields of 51% at 463K. Our comparative studies revealed that the alcoholysis of cellulose in methanol proceeded more efficiently than the hydrolysis of cellulose in water under similar reaction conditions.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Hydrogenation of levulinic acid to γ-valerolactone in dioxane over
           mixed MgO–Al2O3 supported Ni catalyst
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Kun Jiang, Dong Sheng, Zihao Zhang, Jie Fu, Zhaoyin Hou, Xiuyang Lu
      Mixed MgO–Al2O3 (with different Mg/Al ratio) supported nickel catalysts were prepared via co-precipitation method and used for hydrogenation of levulinic acid to γ-valerolactone under mild condition. Characterization results indicated that mixed MgO–Al2O3 supported Ni catalysts possessed bigger surface area than that of Ni/MgO and Ni/Al2O3, and Ni dispersed highly on the surface of mixed MgO–Al2O3 support. It was found that mixed MgO–Al2O3 supported Ni catalysts were more active and selective for the hydrogenation of levulinic acid to γ-valerolactone than that of Ni/MgO and Ni/Al2O3, and the best yield of γ-valerolactone at 160°C, 1h and 3MPa H2 reached 99.7% over Ni/MgAlO2.5, and Ni/Mg2Al2O5 could be recycled without obvious loss of its initial activity.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Hydrothermal conversion of glucose into organic acids with bentonite as a
           solid-base catalyst
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Xiaoyun Gao, Heng Zhong, Guodong Yao, Weimin Guo, Fangming Jin
      In this study, a new process of using bentonite as a solid base catalyst in the hydrothermal conversion of glucose into lactic acid was proposed. Results showed that bentonite can act as a solid-base catalyst in conversion of glucose into lactic acid, and the yield of lactic acid increased from 5% in the absence bentonite to 11% in the presence of bentonite. Also, it was found that the presence of bentonite can greatly improve the production of acetic acid, and a considerably high acetic acid yield of 27% could be obtained in the two-step reaction. Since the bentonite is quite cheap and abundant in nature, the reported results should be helpful to facilitate studies for developing a new and green process for the conversion of carbohydrate biomass into value-added chemicals.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Lactic acid production from rice straw in alkaline hydrothermal conditions
           in presence of NiO nanoplates
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Rafia Younas, Shicheng Zhang, Liwu Zhang, Gang Luo, Kaifei Chen, Leichang Cao, Yuchen Liu, Shilai Hao
      The research study is based on alkaline hydrothermal liquefaction of rice straw using NiO nanoplates where temperature, reaction time and molar concentrations of alkali (NaOH) were varied to optimize lactic acid (LA) production. The highest yield of 58.81% for lactic acid was obtained at 260°C for 2h with 1M NaOH and 0.052g NiO nanoplates attributing to complete degradation of cellulosic rice straw. Influence of different morphological forms of NiO like nanoparticles, nanoplates and porous nanosheets were also investigated in this perspective where nanoplates had better catalytic activity. Lactic acid production was found to be highly dependent on and sensitive to slight changes in alkaline conditions in the existence of NiO nanoplates as catalyst.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Pd/C-catalyzed reduction of NaHCO3 into CH3COOH with water as a hydrogen
           source
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Heng Zhong, Hansong Yao, Jia Duo, Guodong Yao, Fangming Jin
      In this paper, a simple method of NaHCO3 reduction to CH3COOH in water with Al powder as a reductant on a commercially available Pd/C catalyst is described that producing CH3COOH with a good yield of 8% from NaHCO3 on a carbon basis at 300°C under hydrothermal conditions. A high adsorption enthalpy of C1 intermediates on the Pd catalyst may act as an important role in the reduction of NaHCO3 into CH3COOH on Pd/C catalyst. This research provides a simple way to convert the CO2 into a C2 compound.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Carbon dioxide promoted reductive amination of aldehydes in water mediated
           by iron powder and catalytic palladium on activated carbon
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Ran Ma, Yue-Biao Zhou, Liang-Nian He
      A mixture of iron powder and catalytic palladium on activated carbon has been developed for reductive amination of various aromatic aldehydes, including 2-pyridinecarboxaldehyde, in water under CO2 atmosphere. The reversible reaction of CO2 with water could form carbonic acid and hydrogen transfer from water to Pd(0) took place with the presence of iron powder, leading to formation of high-active Pd hydrides for the reductive amination process. On the other hand, the reaction system could be inherently neutralized by ready removal of CO2, thus resulting in facile post-processing.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Highly photocatalytic active thiomolybdate [Mo3S13]2−
           clusters/Bi2WO6 nanocomposites
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Dongting Yue, Zichen Zhang, Zheyi Tian, Taiyang Zhang, Miao Kan, Xufang Qian, Yixin Zhao
      The Mo3S13 2−/Bi2WO6 nanocomposites were facilely fabricated by depositing [Mo3S13]2− clusters onto the hydrothermally prepared Bi2WO6 nanoparticles. This novel Mo3S13 2−/Bi2WO6 nanocomposite exhibited unprecedented visible light photocatalytic activities. The deposited [Mo3S13]2− clusters enhanced the photocatalytic activity of Bi2WO6 by promoting the migration of photoinduced charges, which restrained the recombination of photogenerated hole–electron (h+/e−) pairs on the surface of Bi2WO6. Furthermore, the high photocatalytic stability and recyclability of Mo3S13 2−/Bi2WO6 nanocomposite enable it to be a promising candidate for the environmental remediation especially in wastewater treatment. In all, [Mo3S13]2− clusters with advantages of low cost and earth-abundance are great potential as co-catalyst for photocatalysts.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Surface plasmon resonance of gold nanocrystals coupled with
           slow-photon-effect of biomorphic TiO2 photonic crystals for enhanced
           photocatalysis under visible-light
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Yufei Wang, Ding-Bang Xiong, Wang Zhang, Huilan Su, Qinglei Liu, Jiajun Gu, Shenmin Zhu, Di Zhang
      The slow photon effect in a photonic crystal (PC) can lead to delay and storage of light in the PC and has an immense potential for improving solar-to-energy efficiency. A series of biomorphic TiO2 photonic crystal (TiO2-BMPC) structures are fabricated through a sol–gel method by using butterfly wings as templates, and subsequently gold nanoparticles (Au NPs) with an average size of about 9nm are deposited in situ into the TiO2-BMPC. Varying structural characteristics of the PCs by choosing different butterfly wings, the slow photon region of the photonic band gap could be purposely tuned to overlap with strong localized surface plasmon resonance (SPR) region of the Au NPs. The matching slow photon of the TiO2-BMPC templated from the butterfly wings of Euploea mulciber intensifies the SPR responses (central at 550nm) of the Au NPs. Consequently, the visible-light harvesting capability of the Au/TiO2-BMPC is significantly improved due to this unique biomorphic architecture. As a result, the designed photocatalyst exhibits a photocatalytic activity that is several time higher than conventional Au/TiO2-P25 material, as illustrated by the example of the photocatalytic decomposition of methyl orange (MO) under visible-light illumination.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Photocatalytic conversion of terephthalic acid preparation wastewater to
           hydrogen by graphene-modified TiO2
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Qian Zhang, Dan Dan Zheng, Lv Si Xu, Chang-Tang Chang
      Using wastewater as sacrificial reagent to transfer solar energy and water as clean energy has attracted significant attention because of increasing concerns on environmental pollution and depletion of fossil fuels. In this study, wastewater from terephthalic acid preparation process was used as sacrificial reagent, and raw components and intermediates were identified by GC–MS, IC, and TOC analyzer. The characterizations of the catalyst were analyzed by XRD, TEM, and XPS. Results showed that the metal and metallic ions (Fe2+ and Fe) in wastewater were more feasible for electron provision than organics. The final products of Fe3+were also confirmed by XPS on the surface of the catalyst. By contrast, the rate of photocatalytic H2 production did not changed with the addition of terephthalic acid. The H2 production rate could reach 1.8mmolg−1 h−1 through the use of wastewater and acetic acid as sacrificial reagents.
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      PubDate: 2016-06-12T23:08:33Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274




      PubDate: 2016-06-12T23:08:33Z
       
  • Contents list
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274




      PubDate: 2016-06-12T23:08:33Z
       
  • Advances in energy and fuels
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Fangming Jin, Yun Hang Hu



      PubDate: 2016-06-12T23:08:33Z
       
  • Photocatalyst of organic pollutants decomposition: TiO2/glass fiber cloth
           composites
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Peng Sun, Ruiyang Xue, Wang Zhang, Imran Zada, Qinglei Liu, Jiajun Gu, Huilan Su, Zhijian Zhang, Jianzhong Zhang, Di Zhang
      Herein TiO2 coated on glass fiber cloth (TiO2/glass fiber cloth, TGFC) was synthesised by sol-gel method. We demonstrated the property about TGFC of photocatalytic decomposition of organic pollutants under ultraviolet-visible (UV–vis) light and sunlight. Glass fiber cloth (GFC) was chosen as the support of TiO2 in order to improve the practical applications for water purification. TGFC-1–6 were characterized by ERSEM, XRD and XPS. Photocatalytic decomposition of crystal violet (CV) was carried out to investigate the photocatalytic activity of TGFC. The efficiency of TGFC-3 was the best. And its photocatalytic decomposition rate of the second to fifth cycle was higher than the first cycle. The photocatalytic decomposition rate of TGFC-3 was 85% under sunlight from 8:00–14:00. We could design and regulate the shape of TGFC and estimate the area, weight and thickness of TiO2, more easily than glass fibers. TGFC is suitable for photocatalytic decomposition of organic pollutants in the water, especially to be fixed in sewage treatment pool and reused.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Numerical study on the wettability dependent interaction of a rising
           bubble with a periodic open cellular structure
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Xuan Cai, Martin Wörner, Holger Marschall, Olaf Deutschmann
      A phase-field method for interface resolving numerical simulations of two-phase flows with OpenFOAM® is validated for the buoyancy-driven rise of a single air bubble through a viscous stagnant liquid using experimental data from literature. The validation encompasses the terminal bubble rise velocity and the instantaneous cutting of the bubble by a solid horizontal cylinder. In the latter process, the numerical method takes into account the equilibrium contact angle of the three-phase system. The numerical method is then used to study the behavior of a single air bubble rising through a representative subdomain of a periodic open cellular structure (POCS) with cubic cell geometry filled with stagnant water. The results indicate that the bubble shape and path do significantly depend on the structure wettability. In the industrial application of POCS for enhancing mass transfer and as catalytic supports, the utilization of structures with high wettability (low contact angles) is expected to be beneficial.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Experimental investigation of gas-liquid distribution in periodic open
           cellular structures as potential catalyst supports
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Markus Lämmermann, Wilhelm Schwieger, Hannsjörg Freund
      Radial and axial liquid distribution was measured in a packed column of 500 mm length and 100 mm inner diameter under various gas- and liquid superficial velocities to achieve trickle flow regime. Liquid maldistribution was determined using a liquid collector at the outlet consisting of 21 collection zones of equal area. In this work, as packings inside the column, periodic open cellular structures (POCS) were manufactured and applied. Such POCS can be used as structured catalyst support and/or liquid distributor. The hydrodynamic behavior of packings with Kelvin cell, Diamond cell and a hybrid combination of both unit cells was studied to identify unit cells with high potential for achieving homogeneous liquid distribution over the entire reactor cross-section. The liquid superficial velocity had a strong influence on the liquid distribution, while an increasing gas flow rate did not change the flow patterns. Kelvin cell packings tend to distribute the liquid towards the center whereas Diamond cell packings predominantly spread the fluid towards the rim. As a consequence of these observations, in this work a novel POCS structure is proposed: The combination of Kelvin and Diamond unit cells, called hybrid DiaKel unit cell. With POCS consisting of this unit cell type, a significantly improved liquid distribution can be achieved. Thus, this structure features high potential as liquid distributor and/or catalyst support in gas-liquid reaction systems.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Performance of ceramic foams as gas–liquid contactors for phenol wet
           oxidation in the trickle regime
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Rita R. Zapico, Pablo Marín, Fernando V. Díez, Salvador Ordóñez
      The scope of this work was to study the performance of a foam packed bed reactor for homogeneous wet oxidation of phenol, a relevant gas–liquid reaction in industrial wastewater treatment. The use of open-cell foams, macroporous structures constituted by interconnected channels with high bed porosity and surface area, largely enhances interfacial mass transfer rates, without significantly increasing pressure drop. Phenol (45mol/m3) was oxidized in the aqueous phase by oxygen dissolved from the gas (6bar), using Cu(II) salt (0.44mol/m3) as homogeneous catalyst. Experiments were performed in a continuous reactor with partial liquid recycle. The fresh feed and total reactor flow rates have been adjusted to obtain different space times (395–1177s) and liquid superficial velocities (0.84–3.5×10−3 m/s). Temperature has also been varied within the range 110–140°C. Experimental phenol conversions are compared to that obtained from a simple perfect mixing model. Finally, the performance of the foam has been compared to that of a random packing bed made of spheres.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Highly conductive “packed foams”: A new concept for the
           intensification of strongly endo- and exo-thermic catalytic processes in
           compact tubular reactors
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Carlo Giorgio Visconti, Gianpiero Groppi, Enrico Tronconi
      We report a preliminary assessment of the heat transfer properties of innovative structured tubular reactors based on the conductive “packed foams” concept. In such reactors the catalyst is loaded in the form of small pellets packed in the voids of a highly conductive open-cell foam. This enables a catalyst inventory which is significantly higher than that of reactors loaded with the same structured substrate washcoated with catalytic material, while still exploiting the potential of enhanced heat removal through a highly conductive structured skeleton. By comparing the heat transfer performances of the packed foams with those of conventional packed beds of pellets and with those of bare (naked) open cell-foams, we show that the presence of the conductive foam within the packed bed of pellets grants optimal heat transfer performances as a result of a synergy between the enhanced conductive heat transfer in the solid structure of the foam and the effective heat transfer at the wall-bed boundary typical of packed beds. The former mechanism, which is flow independent, controls the effective radial conductivity. The latter one enhances the wall heat transfer coefficient and contributes to increase the overall heat transfer coefficient, particularly at high flow rates. This opens new perspectives for the intensification of highly exothermic/endothermic catalytic processes which require greater catalyst inventories in the reactor than those achievable with washcoated open-cell foams.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Heat transfer performance of structured catalytic reactors packed with
           metal foam supports: Influence of wall coupling
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): S. Razza, T. Heidig, E. Bianchi, G. Groppi, W. Schwieger, E. Tronconi, H. Freund
      Based on previous lab-scale heat transfer experiments performed in a test tube filled with metallic foams, extensive simulations of conjugated heat transfer were performed to systematically investigate the role of different coupling scenarios between the foam structure and the tube wall, using a 3D scanned foam geometry to enable the comparison of simulation results with experiments. The goal of this analysis is to gain insight into the prominent role of the wall coupling for radial heat transfer in a structured catalytic reactor packed with metal foams as catalyst supports. In the current numerical investigation the focus is on the characterization of the contact area between the foam and the reactor wall. Starting from perfect contact between the two, the contact area was decreased by selecting randomly some boundary spots of the foam and considering them as adiabatic. Moreover, the local distribution of the adiabatic struts was restricted to regions near the reactor inlet to additionally investigate the influence of the local distribution of the adiabatic struts at same overall contact areas. Eventually, all the contacts between the foam and the reactor wall were considered adiabatic as the other limiting case, wherein heat transfer at the foam/wall interface was governed solely by convection. The numerical analysis revealed that even if only a limited fraction of the struts have a direct contact with the tube wall, the heat transfer rate is significantly enhanced in comparison to the adiabatic case. In analogy with the previous experimental study, the numerical investigation was carried out for two different gases, nitrogen and helium, in order to address the influence of the thermal conductivity of the fluid phase. For further experimental verification, additional heat transfer measurements were performed for the case of a foam directly sintered to the tube in order to realize a perfect contact between foam and wall.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Ceramic counterflow reactor for autothermal dry reforming at high
           temperatures
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): R. Kelling, G. Eigenberger, U. Nieken
      Dry reforming (DRM) is a very promising route for producing carbon rich syngas from key future feed stocks of chemical industry: CO2 and methane. Partial combustion of methane with pure oxygen, preferably produced via water electrolysis, can be used to compensate for the required heat of reaction in autothermal operation of DRM. Therefore, a novel reactor concept is presented. The multitubular reactor consists of an inert section to perform efficient heat integration and a catalytically coated reaction section where temperatures far above 1000°C are realized by means of ceramic materials, a suitable catalyst, and simultaneous combustion. A prototype laboratory scale reactor, equilibrium models, and a detailed kinetic model are used to measure the reactor performance in laboratory and in industrial scale. A stable operation is predicted in large scale reactors since constantly high reaction temperatures around 1000°C can prevent harmful coke formation. Besides, the high temperatures enable CO2 conversions above 60% along the catalyst zone in a reactor which is characterized by a very simple and scalable design.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Scale up study of capillary microreactors in solvent-free
           semihydrogenation of 2‐methyl‐3‐butyn‐2‐ol
    • Abstract: Publication date: 15 September 2016
      Source:Catalysis Today, Volume 273
      Author(s): Nikolay Cherkasov, Ma ’moun Al-Rawashdeh, Alex O. Ibhadon, Evgeny V. Rebrov
      A 2.5wt.% Pd/ZnO catalytic coating has been deposited onto the inner wall of capillary reactors with a diameter of 0.53 and 1.6mm. The coatings were characterised by XRD, SEM, TEM and elemental analysis. The performance of catalytic reactors was studied in solvent-free hydrogenation of 2-methyl-3-butyn-2-ol. No mass transfer limitations was observed in the reactor with a diameter of 0.53mm up to a catalyst loading of 1.0kg(Pd) m−3. The activity and selectivity of the catalysts has been studied in a batch reactor to develop a kinetic model. The kinetic model was combined with the reactor model to describe the obtained data in a wide range of reaction conditions. The model was applied to calculate the range of reaction conditions to reach a production rate of liquid product of 10–50kg a day in a single catalytic capillary reactor.
      Graphical abstract image

      PubDate: 2016-06-12T23:08:33Z
       
 
 
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