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Journal Cover Catalysis Today
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0920-5861
     Published by Elsevier Homepage  [2563 journals]   [SJR: 1.283]   [H-I: 129]
  • IFC - Editorial Board
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B




      PubDate: 2014-08-18T16:03:27Z
       
  • Zeolites and mesoporous materials in fuel cell applications
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B
      Author(s): King Lun Yeung , Wei Han
      This review article surveys the use of zeolites and mesoporous materials in fuel cell device and, operations. Zeolites are increasingly used to modify and improve the fuel cell membrane to address the, problems of fuel crossover and membrane stability. Mesoporous carbons and carbon aerogels with, their large surface area, high porosity and good interconnectivity are considered ideal material for electrodes and electrocatalysts. Zeolites and mesoporous materials are also employed as template to create nano-, micro- and macro-scale structures for new electrocatalysts. Furthermore, zeolites are used as catalyst, adsorbent and membrane in fuel processing from hydrogen production to purification.
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      PubDate: 2014-08-18T16:03:27Z
       
  • Solid acids: Green alternatives for acid catalysis
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B
      Author(s): Princy Gupta , Satya Paul
      This review deals with the general discussion on green chemistry and catalysis; and solid acid catalysts. Various Lewis and Brønsted solid acid catalysts reported in the last few years for various synthetic protocols have been discussed in this review.
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      PubDate: 2014-08-18T16:03:27Z
       
  • Key questions, approaches, and challenges to energy today
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B
      Author(s): John N. Armor
      This perspectives article is intended to highlight global energy needs and solutions with a focus on catalysis. Market dynamics are discussed along with today's major energy resource options and emerging energy resources versus petroleum with a particular focus on those topics where catalysis can offer real impact: shale gas, biomass, and solar. Petroleum, NG, and coal continue to dominate the energy resources for most nations with the percentage of renewables growing but accounting, in total, for a much smaller share of the energy pie. Other natural resources, such as land, geology, and water do impact energy options. Over the last few years, shale gas has had a big impact on the available energy resources. Renewables will take increasing amounts of the energy pie, but this is going to depend on the region and in nations, such as the USA and China, which have a long term supply of any one of the big three energy resources: NG, petroleum, and/or coal. There have in the past and will continue to be roles for catalysis and new materials in the big three and in renewables with many new opportunities arising because of the recent development of vast fields of shale gas wells producing at regionally competitive prices.
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      PubDate: 2014-08-18T16:03:27Z
       
  • Comment on “The Critical evaluation of in situ probe techniques for
           catalytic honeycomb monoliths” by Hettel et al.
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B
      Author(s): Alexandre Goguet , William P. Partridge , Farid Aiouche , Christopher Hardacre , Kevin Morgan , Cristina Stere , Jacinto Sá



      PubDate: 2014-08-18T16:03:27Z
       
  • Answer to the Comment from Goguet et al. to the paper “The Critical
           evaluation of in situ probe techniques for catalytic honeycomb
           monoliths” by Hettel et al. [1]
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part B
      Author(s): Matthias Hettel , Claudia Diehm , Olaf Deutschmann



      PubDate: 2014-08-18T16:03:27Z
       
  • Sol–gel method for synthesis of Mn–Na2WO4/SiO2 catalyst for
           methane oxidative coupling
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): H.R. Godini , A. Gili , O. Görke , S. Arndt , U. Simon , A. Thomas , R. Schomäcker , G. Wozny
      In this experimental study, a novel sol–gel method was developed to synthesize a 1.9%Mn–5%Na2WO4/SiO2 catalyst for oxidative coupling of methane (OCM) reactions. The performance of the synthesized catalyst was investigated in fixed-bed and porous packed-bed membrane reactors. Particularly, the effects of operating temperature, methane-to-oxygen ratio and nitrogen dilution on the performance of this catalyst were investigated. It was observed that for high values of methane conversion, the sol–gel Mn–Na2WO4/SiO2 catalyst provides 5–15% higher selectivity toward the desired products (C2: C2H4 +C2H6) than the Mn–Na2WO4/SiO2 catalyst prepared by the incipient wetness impregnation method. It was also observed that for a similar set of experiments, the C2-selectivity of the sol–gel catalyst is affected relatively less by the variation of methane-to-oxygen ratio. As a result, this catalyst can be exploited under the low methane-to-oxygen feed ratio which provides an efficient performance in both the OCM reactor and the OCM process scale. The best observed performance of the sol–gel catalyst in the packed-bed membrane reactor is 78% C2-selectivity, 64% ethylene-selectivity and 24.2% C2-yield under 20% nitrogen dilution.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Kinetic enhancement of ammonia decomposition as a chemical hydrogen
           carrier in palladium membrane reactor
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Naotsugu Itoh , Atsushi Oshima , Eita Suga , Takafumi Sato
      Decomposition of ammonia as a promising chemical hydrogen carrier is carried out at low temperatures using a ruthenium supported catalyst, where a highly efficient hydrogen recovery from ammonia is being desired. The equilibrium conversion is almost 100% in the range of 623–723K but the decomposition remains in a low conversion, so that insufficient activity of present catalysts should be improved. This study attempts to prove that this kinetically limited decomposition can be enhanced in the palladium membrane reactor, while in most of membrane reactor applications the equilibrium limited reactions can be shifted to the product side by selective hydrogen separation. The Langmuir-Hinshelwood types of rate equations, seven reaction models, for ammonia decomposition using a Ru/SiO2 catalyst were derived and compared with experimental results. As the result, the combinative desorption of nitrogen atom was found to be the rate determining step in the range of 623–723K. One dimensional model for a palladium membrane reactor could show that the kinetic enhancement differed considerably according to the reaction model (rate expression). In the ammonia decomposition employing a membrane reactor with a 200μm-thick palladium tube, 15% increase in conversion compared with the conventional packed reactor and 60% of the hydrogen recovery at 723K could be obtained. Simulation showed that further enhancement would be achievable by using thinner palladium membrane.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Design and optimization of an enzymatic membrane reactor for tetracycline
           degradation
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): M. de Cazes , M.-P. Belleville , E. Petit , M. Llorca , S. Rodríguez-Mozaz , J. de Gunzburg , D. Barceló , J. Sanchez-Marcano
      The tetracycline, antibiotic considered as a recalcitrant pollutant, was successfully depleted from model aqueous solutions by immobilized laccase from Trametes versicolor in an enzymatic membrane reactor. The results obtained show that tetracycline is depleted from water solutions at room temperature and without adding any extra chemicals. The degradation of tetracycline in aqueous solutions at 20mgL−1 during 24h, with equivalent amounts of free or immobilized biocatalyst, allowed reaching a tetracycline degradation yield of 56% with an enzymatic membrane whereas it was only of 30% with free laccase. This result highlights the good reactivity and stability of the immobilized enzyme for the degradation of tetracycline. Moreover, the enzymatic membrane reactor was able to reach a constant degradation rate of 0.34mg of tetracycline per hour during 10 days.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Production of high purity hydrogen by ethanol steam reforming in membrane
           reactor
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): E. Yu. Mironova , M.M. Ermilova , N.V. Orekhova , D.N. Muraviev , A.B. Yaroslavtsev
      Production of hydrogen in the course of ethanol steam reforming (ESR) on bimetallic Pt-Ni and Pt-Ru nanocatalysts supported on detonation nanodiamonds (DND) was studied in conventional and membrane reactors. The highest hydrogen yield and purity were achieved in the case of Pt-Ru/DND catalysts at total metal content of 0.3% and atomic Pt/Ru ratio of 9/1. It is shown that realization of ESR process in the membrane reactor with simultaneous hydrogen removal through the Pd-Ru membrane produces hydrogen of high purity, free of any other gaseous products.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Studies on water–gas-shift enhanced by adsorption and membrane
           permeation
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): F.R. García-García , M. León , S. Ordóñez , K. Li
      A new sorption enhanced membrane reactor (SEMR), consisting of a packed adsorbent-catalyst bed (10% CuO/CeO2 catalyst and a hydrotalcite-derived Mg–Al mixed oxide) around a tubular Pd/Ag hollow fibre membrane, has been proposed to obtain high purity H2 and simultaneous capture of CO2 during the water gas shift reaction. For comparison purposes, catalytic activity tests were carried out at atmospheric pressure and operating temperatures between 100°C and 550°C in three different catalytic reactors: (1) a fixed-bed reactor (FBR), (2) a sorption enhanced reactor (SER) and (2) a new SEMR. In all cases, the feed mixture Ar/CO/H2O ratio was 11/1/0.75 with a space velocity of 22L/gh. The performance of the FBR was used as a reference to compare with the results obtained from the SER and SEMR. The H2 yield at 350°C using the SER was 80%, which is 33% higher than that obtained in the traditional FBR and 18% higher than the corresponding thermodynamic equilibrium. However, due to the high CO/H2O ratio (R >1), undesirable side-reactions such as C deposition become important at temperatures higher than 400°C. A similar behaviour was observed using the SEMR, however in this case, a high purity CO x free H2 production was obtained. This preliminary study shows relevant data obtained using a SER and the new SEMR, which allows for the better understanding and design of multifunctional catalytic reactors.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Performance of two photocatalytic membrane reactors for treatment of
           primary and secondary effluents
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Sylwia Mozia , Dominika Darowna , Kacper Szymański , Sara Grondzewska , Katarzyna Borchert , Rafał Wróbel , Antoni W. Morawski
      The performance of two photocatalytic membrane reactors (PMRs), utilizing ultrafiltration (UF) – PMR1, or direct contact membrane distillation (DCMD) – PMR2, during treatment of primary (PE) and secondary (SE) effluents of municipal wastewater treatment plant is presented. Additionally, single UF and DCMD were also examined. TiO2 Aeroxide® P25 (0.5–1.5g/dm3) was applied as a photocatalyst. Photocatalysis contributed to an improvement of the permeate flux in PMR1 compared to UF alone for 25–38% in case of PE and for 33% when SE were used. Based on SEM, AFM and contact angle measurements the flux improvement was attributed to the porous structure of TiO2 cake and hydrophilicity of the TiO2 – covered membrane. On the opposite, no flux decline during treatment of SE in PMR2 was found. However, in case of PE a decrease of the flux for ca. 40–50%, regardless of the presence or absence of TiO2, was observed. That was due to the formed dense fouling layer, which contributed to the increase of mass and thermal resistances. Permeate quality was higher in PMR2 than in PMR1. However, since mineralization of dissolved organic carbon in feed was very low, the treatment efficiency was attributed mainly to membrane separation rather than to photocatalysis.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Adsorption and photocatalytic degradation of methyl orange imprinted
           composite membranes using TiO2/calcium alginate hydrogel as matrix
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Kongyin Zhao , Lingzhi Feng , Hongquan Lin , Yifan Fu , Beibei Lin , Wenkui Cui , Sidi Li , Junfu Wei
      In this paper, molecularly imprinted TiO2/calcium alginate (T/CA) membrane was synthesized by using T/CA as supporting matrix, ethylenetri(β-methoxy) ethyoxysilane (KH-570) and γ-amidopropyltri- ethyoxysilane (KH-550) as functional monomers and methyl orange (MO) as template. The T/CA membranes and MO imprinted T/CA composite membranes were characterized by SEM, FT-IR and XRD. The adsorption and photocatalytic degradation of MO imprinted membranes were investigated. The results indicated that the process of dispersion in alginate and sol-gel of silanes did not have influence on the crystallization process of nano-TiO2 particles. MO was adsorbed more and faster by the molecularly imprinted membrane (MIP) than the non-imprinted membrane (NIP). Also, MIP showed good selectivity for photodegradation of MO when using MR as competitive molecules.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Phenolic wastewater treatment by an electrocatalytic membrane reactor
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Hong Wang , Qiqi Guan , Jianxin Li , Tonghua Wang
      An electrocatalytic membrane reactor (ECMR) constituted by TiO2 loading carbon membrane named TiO2/carbon electrocatalytic membrane as an anode and a stainless steel mesh as a cathode has been employed to treat phenolic wastewater. A synthetic phenol wastewater as the feed was prepared by mixing phenol and electrolyte (Na2SO4) with the concentration of 15g/L. FESEM, XPS, cyclic voltammetry (CV) and high-performance liquid chromatography (HPLC) were used to characterize and analyze the electrocatalytic membrane, phenol concentration and degraded intermediates. The results showed that the removal rate of phenol and TOC reached approximately 99.4 and 86.3% after 2h treatment at 2.0mM phenolic wastewater by ECMR, respectively. The main intermediate products of phenol degradation included benzoquinone and organic acids. The efficiency and the degraded intermediates could be controlled by the main parameters of ECMR such as residence time, current density, etc. During the ECMR operation under the conditions of 10.0mM phenolic wastewater, pH of 6, current density of 0.3mA/cm2 and residence time of 5.2min, the achieved phenol removal rate and complete mineralization fraction were 99.96 and 72.4%, respectively. The high efficiency and phenol removal obtained are related to the synergistic effect of the electrochemical oxidation and separation in the reactor.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Electrochemical synthesis of fuels by CO2 hydrogenation on Cu in a
           potassium ion conducting membrane reactor at bench scale
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Esperanza Ruiz , Domingo Cillero , Pedro J. Martínez , Ángel Morales , Gema San Vicente , Gonzalo de Diego , José María Sánchez
      The electrochemical synthesis of fuels by CO2 hydrogenation was studied over a cheap, widespread and non-precious Cu catalyst in a potassium ion conducting membrane (K-βAl2O3) reactor at bench scale, under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H2/CO2 ratios and using gas compositions representative of post-combustion CO2 capture exit streams and easily scalable catalyst–electrode configurations, as an approach towards its potential practical application. The Cu catalyst film was deposited by electroless and characterised both as prepared and after testing. The presence of Cu+ and relatively big Cu particles probably determined the high selectivity to CH3OH and the unusual small selectivity to CO and CH4. Selectivities to CH3OH, C2H5OH and C2H6O were electrochemically enhanced up to a maximum of 34, 22 and 3.4 times, respectively. The optimum temperature for the electrochemically assisted CO2 hydrogenation was selected to be 325°C. Higher gas flow rates favoured the synthesis of dimethyl ether at the expense of methanol and ethanol formation. CO2 conversion increased with H2/CO2 ratio, whereas selectivity to fuels showed a maximum for a H2/CO2 ratio of 2. Selectivity to dimethyl ether follows an opposite trend vs. H2/CO2 ratio with respect to methanol and ethanol ones.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Poly-thiosemicarbazide/gold nanoparticles catalytic membrane: In-situ
           growth of well-dispersed, uniform and stable gold nanoparticles in a
           polymeric membrane
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): L.F. Villalobos , P. Neelakanda , M. Karunakaran , D. Cha , K.-V. Peinemann
      This work presents a method that achieves the highest loading, published so far, of non-agglomerated and well-distributed gold nanoparticles (AuNPs) inside a polymeric membrane. The method uses poly-thiosemicarbazide (PTSC) as the starting material for fabricating the membranes. This polymer contains one chelate site per monomeric unit, resulting in a high content of adsorption sites. This helps to achieve such high loading without agglomeration, along with the strong interaction of the chelate sites with the metal ions and the fact that they are distributed homogeneously along the membrane structure. The simple and scalable three-step procedure developed in this work resulted in a PTSC membrane containing 33.5wt.% Au/PTSC in the form of 2.9nm AuNPs. The membrane demonstrated catalytic activity for the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP).
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      PubDate: 2014-08-14T16:01:43Z
       
  • PVA composite catalytic membranes for hyacinth flavour synthesis in a
           pervaporation membrane reactor
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): T.F. Ceia , A.G. Silva , C.S. Ribeiro , J.V. Pinto , M.H. Casimiro , A.M. Ramos , J. Vital
      Composite catalytic membranes consisting of poly(vinyl alcohol) cross-linked with glutaraldehyde and H-USY zeolite dispersed into the polymeric matrix were prepared and used in the hyacinth flavour synthesis by acetalization of phenylacetaldehyde and glycerol. In order to study the effects of catalyst loading, polymer cross-linking and hydrophilic/hydrophobic balance in the catalytic behaviour of the prepared membranes, catalytic runs were performed in batch conditions and in a pervaparation assisted catalytic membrane reactor. It was found that polymer cross-linking strongly affects the membranes’ sorption and transport properties which seem to improve with the increase of catalyst loading. Results also evidence that permeation in membrane reactor was well accomplished with good selectivity to water. The catalytic membranes were characterized by measurement of thickness, water contact angles and swelling degree as well as by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM).
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      PubDate: 2014-08-14T16:01:43Z
       
  • Application of FAU zeolite membranes to alcohol/acrylate mixture systems
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Izumi Kumakiri , Kouji Hashimoto , Yoshihiko Nakagawa , Yuko Inoue , Yohei Kanehiro , Kazuhiro Tanaka , Hidetoshi Kita
      Faujasite (FAU) zeolite membranes were prepared by secondary growth method. Separations of methanol from organic solvents by FAU zeolite membranes were investigated to gather fundamental knowledge about membrane separation assisted transesterification. The FAU zeolite membranes showed methanol-selective permeations from azeotrope forming methanol–methyl acetate and methanol–methyl methacrylate mixtures. Pervaporation performances of FAU zeolite membranes were evaluated also with transesterification mixtures formed with the acidic ion-exchange resin, Amberlyst 15, and with synthetic quaternary mixtures.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Performance of a hybrid system sorbent–catalyst–membrane for
           CO2 capture and H2 production under pre-combustion operating conditions
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): M. Maroño , M.M. Barreiro , Y. Torreiro , J.M. Sánchez
      This paper presents experimental results obtained for different approaches used for the simultaneous capture of CO2 and production of H2 under precombustion conditions. A novel hybrid system adsorbent–catalyst–membrane has been designed at Ciemat which combines a sorption enhanced WGS process (which consists of a mixture of adsorbent and catalyst) with a hydrogen selective membrane. First, the individual performance of the membrane and the binary adsorbent–catalyst system is evaluated in terms of H2 permeability, carbon monoxide conversion and CO2 capture and best operating conditions are determined for both approaches. The crucial role of temperature and steam on the overall performance of the system is especially discussed. Finally, first experimental results obtained for the hybrid adsorbent–catalyst–membrane system are presented and the advantages and challenges of adding a H2 selective membrane to the sorption-enhanced process are analysed.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Combined steam and CO2 reforming of methane using catalytic nickel
           membrane for gas to liquid (GTL) process
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Shin-Kun Ryi , Sung-Wook Lee , Jin-Woo Park , Duck-Kyu Oh , Jong-Soo Park , Sung Su Kim
      In this study, test on the combined steam and dry reforming of methane were carried out over a catalytic nickel membrane within a very short residence time of 120ms under different process conditions (CO2/H2O feed ratio and temperature). The effect of the molar ratio of CO2/H2O in the reactants on the H2/CO ratio in the products was investigated at 923–1023K. In the reaction of the combined steam and dry reforming of methane, CH4 conversion was strongly influenced by the CO2/H2O feed ratio and decreased with the increase in the CO2/H2O feed ratio at 923K, while the influence of the CO2/H2O feed ratio on CH4 conversion was not significant at temperatures ≥973K. Unlikely CH4 conversion, the conversion of CO2 increased with the increase in the CO2/H2O feed ratio over the temperature range of 923–1023K. The conversion of CH4 and that of CO2 both increased with increasing temperature because the corresponding reactions are endothermic and remained nearly constant at temperatures ≥973K. The H2/CO molar ratio could be adjusted by the CO2/H2O feed ratio for downstream applications. No carbon deposition on the catalytic nickel membrane was observed after the combined steam and dry reforming of methane tests under all process conditions.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Core–shell Pd/ZSM-5@ZIF-8 membrane micro-reactors with size
           selectivity properties for alkene hydrogenation
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Tong Zhang , Xiongfu Zhang , Xinjuan Yan , Lu Lin , Haiou Liu , Jieshan Qiu , King Lun Yeung
      A well-designed Pd/ZSM-5@ZIF-8 core–shell structure has been prepared by application of a combination of seed-induction synthesis strategy and self-assembly synthesis techniques. First, uniform ZSM-5 particles with micron size and high crystallinity were prepared from organic-template-free gel systems containing 200nm ZSM-5 seeds and exchanged with Pd(NO3)2 aqueous solution. Then incompatibility between the Pd/ZSM-5 core material and ZIF-8 shell precursor was circumvented by surface modification using a layer by layer self-assembly of polyelectrolyte, followed by a subsequent two-step temperature synthesis process inducing the formation of continuous and well-intergrown ZIF-8 shell. Thickness of ZIF-8 shell can be simply tuned by monitoring the assembly cycles. Furthermore, hydrogenations of 1-hexene and cyclohexene were chosen as model reactions to evaluate the catalytic behavior of the Pd/ZSM-5@ZIF-8 core–shell architecture and tert-dodecylthiol was used as a poison to test its anti-poisoning ability. Results show that such core–shell architecture exhibits excellent poison resistance and selectivity control properties for the hydrogenation reactions and can be potentially used as a membrane reactor in the field of heterogeneous catalysis.
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      PubDate: 2014-08-14T16:01:43Z
       
  • New synthesis strategies for Ni/Al2O3-Sil-1 core–shell catalysts for
           steam reforming of methane
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): Jian Zhang , Tong Zhang , Xiongfu Zhang , Weifeng Liu , Haiou Liu , Jieshan Qiu , King Lun Yeung
      The catalytic performance of Ni/Al2O3-Sil-1 core–shell catalysts was investigated for the steam reforming of methane (SRM). The core–shell catalysts consisting of Ni/Al2O3 core catalyst and silicalite-1 (Sil-1) zeolite shell were prepared by different synthesis routes. Catalyst characterization indicates that repeated calcination at elevated temperatures during the catalyst preparation should be avoided to prevent the formation of the inactive NiAl2O4 spinel phase. Thus, the new preparation procedure for the core–shell catalyst involves first growing a Sil-1 shell on the alumina beads to obtain Al2O3-Sil-1 core–shell beads, followed by an incipient wetness impregnation to obtain a Ni/Al2O3-Sil-1 catalyst. The catalytic activity of the catalyst for the SRM reaction displayed ca. 10% improvement over core–shell catalysts prepared by traditional method. The prepared catalysts maintained high reactivity even when exposed to alkali vapor during reaction.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Development of a RhZrO2 catalyst for low temperature autothermal reforming
           of methane in membrane reactors
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): L. Marra , P.F. Wolbers , F. Gallucci , M. van Sint Annaland
      A Rh-based catalyst for low temperature hydrogen generation in membrane microreactor applications has been developed and characterized. A RhZrO2 catalyst with 1.4wt% Rh was prepared by incipient wetness impregnation and was tested for both methane reforming and autothermal reforming at temperatures interesting for membrane reactor applications (i.e. temperatures below 700°C and steam-to-carbon ratio of 2). The kinetic parameters to describe the reaction rate of both methane steam reforming (SMR) and auto-thermal reforming (ATR) over the RhZrO2 catalyst have been determined using a 1D heterogeneous packed bed reactor model to properly account for mass and heat transfer resistances. The experimental results demonstrate that the RhZrO2 catalyst is extremely active for ATR and resistant to coke formation at much lower temperatures and steam-to-carbon ratios compared with conventional Ni-based catalysts. This makes the new catalyst especially suitable for integration in a Pd-based membrane microreactor with a maximum allowable operation temperature of about 650°C dictated by the membrane stability.
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      PubDate: 2014-08-14T16:01:43Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A




      PubDate: 2014-08-14T16:01:43Z
       
  • Contents list
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A




      PubDate: 2014-08-14T16:01:43Z
       
  • Special Issue on the 11th International Conference on Catalysis in
           Membrane Reactors
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): José M. Sousa , Angelo Basile , João Crespo



      PubDate: 2014-08-14T16:01:43Z
       
  • Noble metal catalysts supported on nanofibrous polymeric membranes for
           environmental applications
    • Abstract: Publication date: 1 November 2014
      Source:Catalysis Today, Volume 236, Part A
      Author(s): K. Soukup , P. Topka , V. Hejtmánek , D. Petráš , V. Valeš , O. Šolcová
      The effect of preparation method on the particle size of palladium and platinum nanoparticles supported on poly(2,6-dimethyl-1,4-phenylene) oxide electrospun membranes by the wet impregnation technique was investigated. Catalysts with similar metal loading (0.63–0.78wt.%) possessing various mean metal particle size (2.5–8.7nm) were prepared employing different impregnation times and nominal metal loadings. The catalysts were tested in the total oxidation of methanol (1000ppm in air). The catalytic activity of platinum catalysts increased with increasing size of Pt nanoparticles while the effect of the platinum loading was not observed. On the other hand, the catalytic activity of palladium catalysts increased with the increasing palladium loading and did not correlate with the nanoparticle size.
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      PubDate: 2014-08-14T16:01:43Z
       
  • Grafted non-ordered niobium-silica materials: Versatile catalysts for the
           selective epoxidation of various unsaturated fine chemicals
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Cristina Tiozzo , Chiara Bisio , Fabio Carniato , Matteo Guidotti
      Two kinds of niobium(V)-silica catalysts for the selective epoxidation were synthesised by post-synthesis modification of non-ordered mesoporous silica supports, starting from niobocene dichloride via solvent-less organometallic precursor dry impregnation or conventional liquid-phase grafting technique. Grafted Nb/SiO2 solids were used as catalysts, in the presence of aqueous H2O2, for the epoxidation of unsaturated cyclic and terpenic compounds of interest for fine and specialty chemistry, in particular: cyclohexene, 1-methylcyclohexene, limonene, carveol, α-terpineol, isopulegol, carvotanacetol, carvone, as well as squalene and isopulegyl acetate. These catalysts showed high yields (up to 73%) and excellent chemoselectivities to the desired epoxides (up to 98%), also in short reaction times (down to 1h).
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Enforcing Z-selectivity in olefin metathesis through use of catalysts
           grafted on well-defined phenolic hybrid material
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Nicolas Popoff , Kai C. Szeto , Nicolas Merle , Jeff Espinas , Jérémie Pelletier , Frederic Lefebvre , Jean Thivolle-Cazat , Laurent Delevoye , Aimery De Mallmann , Regis M. Gauvin , Mostafa Taoufik
      We have developed a new hybrid material, featuring single-site phenolic functions on a silica surface. This new material was used for the grafting, by surface organometallic chemistry, of tungsten perhydrocarbyl and molybdenum bispyrrolide alkylidene complexes. Dramatic improvements in terms of activity and stability were observed in propylene metathesis, when compared to the silica counterpart. Introducing a phenolic spacer between the active molybdenum center and the surface enhances the stereoselectivity towards the Z isomer.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235




      PubDate: 2014-08-05T15:59:33Z
       
  • Contents list
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235




      PubDate: 2014-08-05T15:59:33Z
       
  • Phosphine- and ammonium-functionalized ordered mesoporous carbons as
           supports for cluster-derived metal nanoparticles
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): D. Vidick , A.F. Leonard , C. Poleunis , A. Delcorte , M. Devillers , S. Hermans
      An ordered mesoporous carbon (OMC) was functionalized with ammonium or chelating phosphine ligands. In both cases, the functionalization procedure started by oxidation by nitric acid treatment, followed by activation of surface carboxylic acid groups with thionyl chloride, then formation of amide bonds with diamines. The pendant amine groups were then either quaternized or further reacted with phosphine. The introduced functions were used as anchors for molecular mixed-metal clusters. These organometallic grafted species could then be thermally transformed into hetero-metallic nanoparticles (NP) embedded within the mesoporous framework. The NP/OMC nanocomposites could find application in hydrogenation heterogeneous catalysis or as electrodes in fuel cells.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Silica, alumina and ceria supported Au–Cu nanoparticles prepared via
           the decomposition of [Au(en)2]2[Cu(C2O4)2]3·8H2O single-source
           precursor: Synthesis, characterization and catalytic performance in CO
           PROX
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): D.I. Potemkin , E.Yu. Semitut , Yu.V. Shubin , P.E. Plyusnin , P.V. Snytnikov , E.V. Makotchenko , D.Yu. Osadchii , D.A. Svintsitskiy , S.A. Venyaminov , S.V. Korenev , V.A. Sobyanin
      Silica, alumina and ceria supported bimetallic Au–Cu catalysts were prepared via the decomposition of [Au(en)2]2[Cu(C2O4)2]3·8H2O double complex salt inside the support pore structure. XRD and TEM analyses indicated the selective formation of supported Au0.4Cu0.6 alloy nanoparticles with preset stoichiometry on the support surface. Catalysts were tested in CO preferential oxidation (PROX) reaction. Au0.4Cu0.6/CeO2 catalyst showed best characteristics having higher CO consumption at higher selectivity in the realistic hydrogen-rich mixture containing CO2 and H2O, compared with Au/CeO2 catalyst.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Fabrication of metal nanoparticles in metal organic framework NH2-MIL-125
           by UV photo-assisted methods for optimized catalytic properties
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Martin Martis , Wen Meicheng , Kohsuke Mori , Hiromi Yamashita
      The influence of preparation method on the size, location and state of Pd nanoparticles were investigated within the pores of amine-functionalized metal organic frameworks NH2-MIL-125 using three different photo-assisted deposition methods and the conventional impregnation method. The oxidation state, size and location were determined by XAFS and TEM. The catalytic activity was studied for hydrolysis of ammonia borane (AB) at ambient temperature. The choice of solvent and hole scavenger/reducing medium directly influence the location and the reduction of the particles. Our study shows that the best sample is prepared by combining UV irradiation with a direct reduction by H2 gas, and finding the right amount solvent and solvent/hole scavenger ratio is necessary for successful NPs synthesis using only UV light irradiation.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Hydrophobic gold catalysts: From synthesis on passivated silica to
           synthesis on few-layer graphene
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Fabrice Vigneron , Alexandre Piquet , Walid Baaziz , Pascale Ronot , Anne Boos , Izabela Janowska , Cuong Pham-Huu , Corinne Petit , Valérie Caps
      Hydrophobic gold catalysts have recently proven useful in increasing the efficiency of the aerobic oxidation of hydrocarbons in apolar liquid media. Catalytically active 3nm gold nanoparticles can be dispersed on the surface of commercially available methyl-terminated silica by performing chemical reduction of triphenylphosphine gold(I) chloride in the presence of the support in an ethanol/dichloromethane mixture. This method is here applied to a home-made few-layer graphene which displays a pristine graphitic surface, as shown by thermogravimetric analysis. Since direct application of the protocol leads to much larger gold particles, the protocol of synthesis is subsequently adapted to the specific nature of the graphene support, in particular by performing the reaction under sonication. Further studies of the effect of several reaction parameters on both the average gold crystallite size determined by XRD and the deposition yields determined by elemental analysis reveal (1) the superiority of DMF in minimizing the gold particle size and (2) the impact of short reduction times on maximizing the deposition yields. Repeatability of the experiment is ensured by the development of an optimized protocol of synthesis, and in particular the identification of the most effective positions in the sonication bath.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Impact of organic-ligand shell on catalytic performance of colloidal Pd
           nanoparticles for alkyne gas-phase hydrogenation
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Daniel Lamey , Irina Prokopyeva , Fernando Cárdenas-Lizana , Lioubov Kiwi-Minsker
      Monodispersed Pd nanoparticles (NPs) have been prepared by colloidal technique and deposited on a structured support consisting of carbon nanofibers (CNF) grown on sintered metal fibres (SMF). The surface properties of Pd NPs have been fine-tuned by (i) changing the nature of stabilizing agent (electrostatic vs. steric), (ii) controlling Pd NPs size (2–10nm) and (iii) grafting N-containing ligands onto the CNF/SMF surface. In the semi-hydrogenation of acetylene (T =393K; P =1bar) catalytic response was insensitive to the nature of the reducing agent where equivalent activity/selectivity were obtained over Pd NPs with similar dispersion, prepared with the same stabilizer. A similar product distribution was recorded over Pd NPs with similar crystal size irrespective of the colloidal stabilizer (electrostatic vs. steric). In contrast, a stronger inhibiting effect on hydrogenation rate has been found with electrostatic stabilizer (sodium di-2-ethylhexylsulfosuccinate) as compared to the steric ones (polyvinylpyrrolidone or polyvinylalcohol) and assigned to geometric and electronic effects. Decrease (from 8→ 2nm) in Pd NPs size results in a concomitant decrease in activity (antipathetic size-sensitivity), but higher selectivity to target ethylene product. Grafting of nitrogen-containing modifiers (polyvinylpyridine or polyethylenimine) on the CNF/SMF support results in a significant increase in olefin selectivity (up to 93%) where the catalyst shows remarkable stability during 120h on-stream. This is explained by the electronic modifications promoted by interactions between the Pd NPs and the grafted ligands as confirmed by XPS analysis. In comparison, stabilizer-free Pd/CNF/SMF has low selectivity to ethylene (65%). In summary, controlled size Pd (core) nanoparticles with organic ligands (shell) demonstrated increased selectivity and remarkable stability in catalytic gas-phase alkyne semi-hydrogenation opening new tools for rational catalyst design.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Atomically well-defined Au25(SR)17/18 nanoclusters deposited on silica
           supports for the aerobic epoxidation of trans-stilbene
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Christophe Lavenn , Aude Demessence , Alain Tuel
      Two atomically well-defined thiolate gold nanoclusters, Au25(SC2H4Ph)18 and Au25(SPhNH2)17, having the same gold core but different thiolate ligands have been deposited on silica supports and the obtained catalysts have been tested in the aerobic oxidation of trans-stilbene. By properly selecting the support to maximize cluster/surface interactions, it was possible to prepare materials with small nanoparticles and very narrow particle size distributions. Au25(SPhNH2)17@SBA-15 catalyst showed an activity and a trans-stilbene epoxide selectivity comparable to the best heterogeneous catalysts. Elimination of the thiolate molecules by calcination did not significantly modify the particle size but decreased the activity, pointing out the critical role of the ligands in the reaction.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Enhanced ethylene polymerization of Ni(II) complexes supported on carbon
           nanotubes
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Liping Zhang , Eva Castillejos , Philippe Serp , Wen-Hua Sun , Jérôme Durand
      A series of nickel complexes Ni1–Ni4 containing N-(5,6,7-trihydroquinolin-8-ylidene)aminoaryl ligands was prepared in good yields. The amino group present allowed covalent anchoring of these complexes through an amido link onto the surface of two kinds of multi-walled carbon nanotubes (MWCNTs). XPS analysis evidenced that the molecular structure of these Ni(II) complexes was maintained after grafting. Activated by MAO, these catalytic systems promoted ethylene polymerization. Our studies evidenced the beneficial influence of the MWCNTs since in most cases, heterogeneized systems are more active than the corresponding unsupported catalysts, producing higher molecular weight polymers in which MWCNTs are homogeneously dispersed.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Cyclodextrin-based systems for the stabilization of metallic(0)
           nanoparticles and their versatile applications in catalysis
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Sébastien Noël , Bastien Léger , Anne Ponchel , Karine Philippot , Audrey Denicourt-Nowicki , Alain Roucoux , Eric Monflier
      In order to better respond to environmental standards, the development of metal nanoparticles using green approaches has exponentially grown for the last decade. Cyclodextrins, which are cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units, have appeared to be interesting candidates for the synthesis of metal nanoparticles. Indeed, through the ability to form inclusion complexes or supramolecular adducts with organic molecules or metal precursors, cyclodextrins can be successfully employed to stabilize size-controlled zerovalent metallic nanoparticles active for hydrogenation reactions carried out in aqueous or gas-phase media. In this summary of our works, we report that cyclodextrins could be used in various forms and environments: (i) in free form, (ii) in complexed form with appropriate guests molecules, (iii) in combination with polymer matrices, (iv) in thermosensitive hydrogels and (v) immobilized onto porous carbons supports. All these studies highlight the fact that cyclodextrins can be seen as multi-task agents for nanocatalysis.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Heterogeneous catalyst preparation in ionic liquids: Titania supported
           gold nanoparticles
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Camella Oumahi , Jean Lombard , Sandra Casale , Christophe Calers , Laurent Delannoy , Catherine Louis , Xavier Carrier
      This work reports the use of ionic liquids (ILs) as solvent for the synthesis of Au/TiO2 heterogeneous catalysts. It is shown that the versatility of the physico-chemical properties of ILs makes them interesting solvents for a broad control of supported metal nanoparticles (NPs) size and for a fine-tuning of metal–support interaction. Synthesis and deposition of Au NPs on TiO2 are carried out through a colloidal route in imidazolium-based ILs (1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and trifluoromethanesulfonate (BMIMOTf)) and in a Deep Eutectic Solvent (DES, choline chloride and urea). The stabilization of the dispersed NPs and their deposition on an oxide carrier is investigated in pure ILs and in the presence of extra stabilizing agents (1-methylimidazole or polyvinylpyrrolidone). In the absence of TiO2, the NPs stability varies with the composition of the IL (BMIMOTf>BMIMPF6 >DES) and is critically depending on the addition of an extra stabilizing agent (SA). Conversely, when gold NPs are synthesized in the presence of TiO2 in imidazolium ILs, the addition of a SA is no longer required since the oxide support acts as a stabilizer for the gold colloids and prevents aggregation of NPs. A detailed XPS investigation of the surface composition of the TiO2-supported gold catalysts shows that the cationic part of the imidazolium ILs on the one hand and urea in DES on the other hand are co-adsorbed with gold NPs upon deposition on TiO2, probably decorating and stabilizing the Au NPs. The fate of the anionic part of the ILs (PF6 −, OTf− and Cl−) is highly depending on the type of IL. Limited surface adsorption is reported for triflate (BMIMOTf) and chloride anions (DES), the latter being fully removed upon calcination, while PF6 − (BMIMPF6) remains adsorbed on the surface during Au NPs deposition and leads to PO x δ− and F− surface species upon calcination. The surface composition controls the intrinsic catalytic activity (TOF) in the selective hydrogenation of butadiene. It is shown that the surface doping of supported Au NPs with P and F anionic deposits (synthesized in BMIMPF6) has a promoting effect for the intrinsic catalytic activity.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Degradation of chlorinated phenols in water in the presence of H2O2 and
           water-soluble μ-nitrido diiron phthalocyanine
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Cédric Colomban , Evgeny V. Kudrik , Pavel Afanasiev , Alexander B. Sorokin
      Efficient disposal of pollutants is a key problem in the environmental context. In particular, chlorinated aromatic compounds are recalcitrant to biodegradation and conventional treatment methods. Iron phthalocyanines were previously shown to be efficient catalysts for the oxidative degradation of chlorinated phenols considered as priority pollutants. We have recently discovered μ-nitrido diiron phthalocyanines as powerful oxidation catalysts. Herein, we evaluate these emerging catalysts in the oxidation of chlorinated phenols in comparison with conventional mononuclear complex. Catalytic performance of iron tetrasulfophthalocyanine (FePcS) and corresponding μ-nitrido dimer [(FePcS)2N] have been compared in the oxidation of chlorinated phenols by hydrogen peroxide in water. The oxidative degradation of 2,6-dichlorophenol (DCP) and 2,4,6-trichlorophenol (TCP) has been studied. The (FePcS)2N exhibited better catalytic properties than mononuclear FePcS in terms of conversion and mineralization (transformation of organic chlorine to Cl− and decrease of total organic carbon due to the formation of CO2). Kinetics of the DCP oxidation indicated that different reaction mechanisms are involved in the presence of FePcS and (FePcS)2N. The high catalytic activity of (FePcS)2N in the degradation and mineralization of chlorinated phenols make μ-nitrido diiron phthalocyanines promising catalyst to apply also in environmental remediation.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Preface
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Catherine Louis , Xavier Carrier , Florence Epron



      PubDate: 2014-08-05T15:59:33Z
       
  • Mononuclear gold catalysts for the asymmetric intramolecular
           hydroamination of alkenes
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Christophe Michon , Marc-Antoine Abadie , Florian Medina , Francine Agbossou-Niedercorn
      The intramolecular gold catalysed asymmetric hydroamination of alkenes was studied screening a series of mononuclear gold(I) and (III) complexes in combination with silver salts. Among the various chiral mono-phosphine and diaminocarbene ligands tried, the best catalysts arose from mononuclear gold(I) complexes synthesized from BINOL based phosphoramidite ligands. The latest were improved by addition of bulky substituents at specific positions of the BINOL scaffold. The resulting gold(I) complexes were combined with selected silver salts to afford efficient catalysts for intramolecular hydroamination of alkenes at mild temperatures, with good conversions and average enantioselectivities.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Prospectives for bio-oil upgrading via esterification over zeolite
           catalysts
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Maria Milina , Sharon Mitchell , Javier Pérez-Ramírez
      A promising route to upgrade crude bio-oil prior to hydrotreating is via the catalytic esterification of intrinsic acids and alcohols. This process reduces the acidity and oxygen content of the bio-oil, thereby improving the stability and decreasing the hydrogen consumption in subsequent refining steps. Here, the applicability of microporous zeolite catalysts of different framework type and composition is explored in the liquid-phase esterification between the characteristic bio-oil constituents, acetic acid and o-cresol. Ester formation, which is significantly influenced by concurrent coke-forming reactions, is dependent on the reaction temperature and on the size of the zeolite micropores, with maximum yields observed over large-pore beta and faujasite catalysts. The benefits of introducing secondary mesoporosity through demetallation in alkaline media are remarkable for medium-pore ZSM-5 due to the alleviated diffusion constraints, while the enhanced performance of hierarchical faujasite is less pronounced, but still appreciable. Characterization of the spent catalysts by XRD and N2 sorption evidences the preserved crystallinity and microporosity of the zeolites, while IR spectroscopy of adsorbed pyridine reveals a small reduction in the concentration of Brønsted acid sites. The latter is detrimental for the ester formation upon reuse of ZSM-5 zeolites, while faujasite catalysts preserve their initial activity. These findings highlight both the potential of microporous zeolites and their hierarchical analogs for acid-catalyzed condensation reactions in the field of bio-oil upgrading and some of the possible challenges which could be faced.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Shape-selective organic–inorganic zeolitic catalysts prepared via
           interlayer expansion
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Trees De Baerdemaeker , Wannes Vandebroeck , Hermann Gies , Bilge Yilmaz , Ulrich Müller , Mathias Feyen , Dirk De Vos
      Interlayer expansion of layered zeolite precursors is achieved via the insertion of an additional T-atom in between the layers, typically by means of a silylating agent as source of the T-atom. (3-Mercaptopropyl)methyldimethoxysilane was used as Si-source in the interlayer expansion of the layered zeolite precursors RUB-36 and RUB-39. The structure expansion was confirmed with PXRD. The incorporation of the silylating agent was followed with 29Si MAS NMR, 13C CP MAS NMR and thermogravimetric analysis. The incorporated thiol groups were oxidized with H2O2 to obtain sulfonic acid groups in between the layers. 13C CP MAS NMR was used to characterize the organic species and monitor the conversion of thiol to propylsulfonic groups. The shape-selective properties of the obtained materials were investigated in acid-catalyzed tetrahydropyranylation reactions.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Comparison of mesoporous SSZ-13 and SAPO-34 zeolite catalysts for the
           methanol-to-olefins reaction
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Leilei Wu , Emiel J.M. Hensen
      Several approaches to improve the catalytic performance of SSZ-13 and SAPO-34 for application as acid catalysts in the methanol-to-olefins (MTO) reaction were explored. Silylation of mesoporous SSZ-13 with a Si/Al ratio of 20 zeolite resulted in increased lifetime in the MTO reaction. Lowering the acidity of SSZ-13 by increasing the Si/Al ratio to 50 also increased the lifetime. The generation of additional mesoporosity in SSZ-13 with a Si/Al ratio of 50 by use of the organosilane octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride (TPOAC) only resulted in a minor improvement of the lifetime. Attempts to synthesize mesoporous SSZ-13 at high Si/Al ratios by use of (C22H45 N+(CH3)2 C4H8 N+(CH3)2 C4H9)Br2 (C22-4-4Br2) were unsuccessful, and instead ZSM-5 zeolite was obtained. Similarly, SAPO-34 could not be made hierarchical by using C22-4-4Br2 as a mesoporogen. In this case, other AlPO-phases were obtained. Mesoporous SAPO-34 was synthesized by using TPOAC in the synthesis gel. The additional intracrystalline mesoporosity did not lower the deactivation rate of SAPO-34 as was earlier observed for SSZ-13. The total methanol conversion capacity per acid site for microporous and mesoporous SAPO-34 were however comparable. The lower acidity of the acid sites in SAPO-34 led to the complete utilization of the micropore space. This is to be contrasted to SSZ-13 zeolite, for which the increased rate of coke formation results in more extensive coking deactivation and underutilization of the micropore space.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Au–Pd alloy nanoparticle catalyzed selective oxidation of benzyl
           alcohol and tandem synthesis of imines at ambient conditions
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Wenjing Cui , Qi Xiao , Sarina Sarina , Wulan Ao , Mengxia Xie , Huaiyong Zhu , Zhaorigetu Bao
      Alloy nanoparticles (NPs) of gold and palladium on ZrO2 support (Au–Pd@ZrO2) were found to be highly active in oxidation of benzyl alcohols and can be used for the tandem synthesis of imines from benzyl alcohols and amines via a one-pot, two-step process at mild reaction conditions. The first step of the process is oxidation of benzyl alcohol to benzaldehyde, excellent yields were achieved after 7h reaction at 40°C without addition of any base. In the second step, aniline was introduced into the reaction system to produced N-benzylideneaniline. The benzaldehyde obtained in the first step was completely consumed within 1h. A range of benzyl alcohols and amines were investigated for the general applicability of the Au–Pd alloy catalysts. It is found that the performance of the catalysts depends on the Au–Pd metal contents and composition. The optimal catalyst is 3.0wt% Au–Pd@ZrO2 with a Au:Pd molar ratio 1:1. The alloy NP catalyst exhibited superior catalytic properties to pure AuNP or PdNP because the surface of alloy NPs has higher charge heterogeneity than that of pure metal NPs according to simulation of density function theory (DFT).
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Supported palladium–copper catalysts: Preparation and catalytic
           behavior in hydrogen-related reactions
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): M. Bonarowska , O. Machynskyy , D. Łomot , E. Kemnitz , Z. Karpiński
      Two series of highly dispersed supported Pd–Cu catalysts were prepared using different supports: highly acidic aluminum fluoride HS-AlF3, characterized by high surface area, and active carbon, both prepared by different preparation methods (fluorolytic sol–gel method and co-impregnation). A variety of techniques: chemisorption of hydrogen, XRD, TEM, and catalytic performance in two hydrogen-related probe reactions (in n-pentane hydroisomerization and CCl4 hydrodechlorination) were employed to probe metal dispersion and the extent of interaction between two metal components. A reasonable degree of bimetal intermixing in Pd–Cu/HS-AlF3 catalysts synthesized by fluorolytic co-gelation was recognized by the catalytic behavior in bifunctional hydroisomerization of n-pentane. A significantly decreased, compared to pure palladium, hydrogenation–dehydrogenation potential of Pd–Cu alloys led to a weaker performance of bimetallic catalysts. Similarly, it was found that incipient wetness co-impregnation of active carbon resulted in the formation of catalysts characterized by good metal dispersion and significant extent of Pd–Cu alloying. Although the monometallic 2wt% Cu/carbon catalyst is nearly inactive in CCl4 hydrodechlorination, copper addition to palladium in the co-impregnated catalysts had very pronounced effect, vastly increasing the selectivity toward longer than methane hydrocarbons.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Role of the preparation method on properties of Pd/Cu-MCM-41
           hydrodechlorinating catalysts
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Patricia Benito , Manuel Gregori , Sara Andreoli , Giuseppe Fornasari , Stefano Millefanti , Francesca Ospitali , Stefania Albonetti
      The effect of the preparation method on properties of Pd/Cu MCM-41 catalysts tested in the hydrodechlorination of CF3OCFClCF2Cl to CF3OCFCF2 was studied. MCM-41 samples were synthesized using sodium silicate as silica source and cetyltrimethylammonium bromide as template. The incorporation of Pd and Cu active species has been performed by impregnation, inclusion in the MCM-41 synthesis procedure and using pre-formed Pd/Cu nanoparticles. The effect of the removal of the template was also studied using calcination and ionic exchange procedures. The hexagonal structure of MCM-41, large specific surface area and pore volume were preserved after inclusion of active species both as cations during the synthesis of MCM-41 or as Pd/Cu preformed nanoparticles. PXRD and HRTEM evidenced the formation of bimetallic particles in all the prepared catalysts; however their particle size and composition varied with the synthesis procedure. The template removal by ionic exchange avoided the sintering of copper species observed in calcined sample. The use of preformed nanoparticles led to small and well dispersed bimetallic species in the MCM-41 structure; however, also in this case, the template removal by calcination provoked both the increase of the particle size and the oxidation of metals. Catalytic performances in the hydrodechlorination of CF3OCFClCF2Cl, namely the dehalogenating activity and product selectivities, were dependent on catalysts properties.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
  • Influence of the Re introduction method onto Pd/TiO2 catalysts for the
           selective hydrogenation of succinic acid in aqueous-phase
    • Abstract: Publication date: 15 October 2014
      Source:Catalysis Today, Volume 235
      Author(s): Benoit Tapin , Florence Epron , Catherine Especel , Bao Khanh Ly , Catherine Pinel , Michèle Besson
      Bimetallic Re-Pd catalysts were prepared by addition of Re onto a Pd/TiO2 monometallic catalyst, either by a catalytic reduction method or by successive impregnation. The physical and chemical properties of the bimetallic catalysts were evaluated by several characterization techniques, including analysis by transmission electronic microscopy, hydrogen chemisorption, temperature programmed reduction and X-ray photoelectron spectroscopy to explain their different catalytic performances in the selective hydrogenation of succinic acid to 1,4-butanediol in aqueous solution. The localization of the Re deposit on the parent Pd catalyst surface varied according to the Re introduction mode. The catalytic reduction method induced a selective Re deposit at the Pd–TiO2 interface compared to a random distribution obtained by successive impregnation. The oxidation state of the Re species (Re3+, Re0) on the reduced bimetallic samples was also linked to their preparation mode.
      Graphical abstract image

      PubDate: 2014-08-05T15:59:33Z
       
 
 
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