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Journal Cover   Catalysis Today
  [SJR: 1.283]   [H-I: 129]   [8 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2589 journals]
  • Selective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol
           over vanadium modified Ir/SiO2 catalyst
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Boonrat Pholjaroen , Ning Li , Yanqiang Huang , Lin Li , Aiqin Wang , Tao Zhang
      For the first time, V modified Ir/SiO2 (Ir–VO x /SiO2) catalyst was used for the selective hydrogenolysis of tetrahydrofurfuryl alcohol (THFA) to 1,5-pentanediol and exhibited better performance than those of V modified other noble metal (Rh, Ru, Pt and Pd) catalysts. The optimum V/Ir atomic ratio for the 4% Ir–VO x /SiO2 catalyst is about 0.10. Over the 4% Ir–VO x /SiO2 (V/Ir=0.1) catalyst, high THFA conversion and 1,5-pentanediol selectivity can be achieved even at low reaction temperature or system pressure. To understand the reason for its excellent performance, the Ir–VO x /SiO2 catalysts were characterized by XRD, N2-physisorption, TEM, CO chemisorption, H2-TPR, XPS and DRIFTS for CO adsorption. It was found that the modification with V has no evident effect on the average size of Ir particles on the 4% Ir/SiO2 catalyst. The close interaction between V oxide and Ir particle promoted the reduction of VO x at lower temperature. The synergy between the closely contacted Ir particles and the partially reduced isolated VO x species attached on them is the reason for the excellent performance of Ir–VO x /SiO2 catalyst.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Hydrogen storage systems based on solid-state NaBH4/CoxB composite:
           Influence of catalyst properties on hydrogen generation rate
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): O.V. Netskina , A.M. Ozerova , O.V. Komova , G.V. Odegova , V.I. Simagina
      Hydrogen generation from solid-state pellets of sodium borohydride with cobalt boride catalysts has been studied. The nature of the reducing agent (NaBH4, NH3BH3) and the catalyst precursor (CoCl2·6H2O, Co3O4) was shown to have a substantial influence on the rate of hydrogen evolution. The effect of pH on the activity of the catalysts added to the solid-state pellets of sodium borohydride was estimated. It was found that the cobalt catalysts formed under the action of sodium borohydride undergo strong changes in an alkali medium due to boron leaching from cobalt boride and formation of low active Co0 and Co(OH)2.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Electroless plated Cu–Ni anode catalyst for natural gas solid oxide
           fuel cells
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Azadeh Rismanchian , Jelvehnaz Mirzababaei , Steven S.C. Chuang
      A Ni/YSZ anode and a Ni/YSZ modified by Cu electroless plating were investigated for direct utilization of CH4, the major component in natural gas. The catalytic activity of the anodes toward H2 and CH4 oxidation reactions were investigated by comparing the Faraday resistance, R F , of the cells obtained from impedance spectroscopy. The R F ratio of Cu–Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu–Ni/YSZ anode toward CH4 oxidation. The addition of Cu to the Ni/YSZ anode decreased the catalytic activity, but increased the long-term stability of the anode in CH4 fuel. The Cu–Ni/YSZ anode showed long-term stability of 138h in dry CH4 at 750°C. The Raman spectra of the fuel cell cross-section showed a change in type of carbon as a function of Cu concentration. The Cu rich surface showed more disordered carbon as opposed to graphitic carbon on Cu deficient areas in which Cu concentration gradually decreased toward the interlayer. Graphitic carbon produced on highly active Ni surface is known as a precursor to coking. Thus, optimizing the distribution of Cu in the Ni/YSZ anode will be required to develop a stable and high performance anode catalyst for direct CH4 utilization.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Contents list
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246




      PubDate: 2015-02-25T01:02:29Z
       
  • Preface
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246




      PubDate: 2015-02-25T01:02:29Z
       
  • Co3S4/NCNTs: A catalyst for oxygen evolution reaction
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Hongjuan Wang , Zhongping Li , Guanghua Li , Feng Peng , Hao Yu
      Nitrogen-doped carbon nanotubes (NCNTs) immobilized cobaltic sulfide (Co3S4/NCNTs) was prepared by the first formation of Co(OH)2/NCNTs and the subsequent anion-exchange of S2− with OH-, accompanied with the partial oxidation of Co2+. The morphology and microstructure of the prepared Co3S4/NCNTs nanocomposite were characterized by TEM, SEM, XRD and XPS. The electrochemical properties of Co3S4/NCNTs nanocomposite for oxygen evolution reaction (OER) were evaluated by polarization curves and cyclic voltammetry (CV). The results show that Co3S4/NCNTs composite exhibits excellent performance for OER with potential of 0.65V vs. SCE, corresponding to over-potential of 0.43V at the current of 10mAcm−2 in 0.1M KOH electrolyte, being a promising OER electrocatalyst.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Electrochemical reduction of CO2 on electrodeposited Cu electrodes
           crystalline phase sensitivity on selectivity
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Gopalram Keerthiga , Balasubramanian Viswanathan , Raghuram Chetty
      The product distribution of electrochemical reduction of CO2 can be altered by modifying the surface of pure copper by deposition. In this study, chronoamperometric deposition of Cu on Cu (Cu/Cu) was carried out at two different CuSO4 bath concentrations, 0.25M (high) and 0.025M (low), termed as Cu/Cu-H and Cu/Cu-L respectively. These deposits were characterized by X-ray diffraction and they vary in their crystal orientation. Pure Cu and Cu/Cu were aligned towards (111) and (220) plane with a texture coefficient of 1.2 and 1.7, respectively. Electrodeposited electrodes were tested for the electrochemical reduction of CO2 in KCl electrolyte and the results were compared with that of pure Cu electrode. Electrochemical reduction of CO2 showed methane and ethane, with hydrogen as the byproduct. The product distribution varied with the crystal orientation of Cu electrodes. The maximum Faradaic efficiency of methane was 26% obtained on pure Cu electrode with (111) and (200) orientation, whereas Cu/Cu-L with dominating (220) orientation showed a maximum formation of ethane with Faradaic efficiency of 43%. A possible mechanism of product formation on Cu towards C1 and Cu/Cu towards C2 is also discussed.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Functionalized zeolitic imidazolate framework F-ZIF-90 as efficient
           catalyst for the cycloaddition of carbon dioxide to allyl glycidyl ether
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Tharun Jose , Yeseul Hwang , Dong-Woo Kim , Moon-Il Kim , Dae-Won Park
      In this study, zeolitic imidazolate framework (ZIF-90) was synthesized from Zn(NO3)2·4H2O and imidazolate-2-carboxyaldehyde (ICA), then it was post-functionalized to form F-ZIF-90 using hydrazine followed by quaternization. The ZIFs were characterized by elemental analysis (EA), BET, XRD, 13C NMR, FT-IR, and SEM. The surface area and pore volume of F-ZIF-90 were smaller than those of ZIF-90 due to functionalization inside the pores. The F-ZIF-90 showed excellent catalytic activity for the synthesis of the cyclic carbonate from allyl glycidyl ether (AGE) and carbon dioxide. The effects of the reaction parameters such as catalyst amount, reaction time, CO2 pressure, and reaction temperature on the reactivity of F-ZIF-90 were also studied, and reaction mechanism including the role of F-ZIF-90 catalyst was proposed. The F-ZIF-90 catalyst, however, partially lost its crystalline structure and superior catalytic performance when it was reused.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Pilot-scale synthesis of a zirconium-benzenedicarboxylate UiO-66 for CO2
           adsorption and catalysis
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Se-Na Kim , Yu-Ri Lee , Seung-Hwan Hong , Min-Seok Jang , Wha-Seung Ahn
      Synthesis of a zirconium-benzenedicarboxylate, UiO-66, was carried out in increasing production scales of 250mL, 1L and 5L at 393K. Investigation on the effect of synthesis parameters on the product yield and textural properties was carried out using autoclaves of 250mL capacity, whereas systematic scale up works were conducted using glass reactors fitted with condensers under ambient pressure conditions. Finally, 100L pilot scale synthesis of UiO-66 was carried out using commercial terephthalic acid as ligand with industrial-grade dimethylformamide solvent. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption–desorption measurements. The pelletized UiO-66 using polyvinyl alcohol as a binder demonstrated excellent CO2/N2 separation (36:1) with moderately high CO2 adsorption capacity (191mg/g) at 20bar room temperature conditions. UiO-66 also showed excellent catalytic activity in cycloaddition of CO2 to styrene oxide at 2.0MPa and 373K with close to 100% selectivity to carbonate. No appreciable particle size effect on the catalytic activity was observed, and UiO-66 could be reused 3 times without loss of catalytic activity.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Photocatalytic and photoelectrocatalytic degradation and mineralization of
           small biological compounds amino acids at TiO2 photoanodes
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Guiying Li , Xiaolu Liu , Jibin An , Hai Yang , Shanqing Zhang , Po-Keung Wong , Taicheng An , Huijun Zhao
      Quantitative evaluation of photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of small biological compounds like amino acids (AAs) were systematically investigated at illuminated nanoparticulate TiO2 photoanode using a thin-layer photoelectrochemical cell. Three model AAs like phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp), were found to be photocatalytically and photoelectrocatalytically degradable. PEC degradation efficiency was much higher than that of PC method for all compounds investigated, and the superiority becomes more obvious at higher concentrations. Organic nitrogen atoms in AAs can be oxidized to either NH3/NH 4 + or NO3 –, or both, depending the chemical structures of AAs and degradation methods used. HPLC analysis found that, for a given AA except Phe, the hydrophilicity characteristics of intermediates are differed slightly between PC and PEC process. For a given method, similar hydrophilicity characteristics were obtained from all AAs investigated except Phe. Theoretically calculated results showed that initial reaction sites for all single-ringed AAs are likely to occur on the atoms within 6-membered ring structure, while for double-ringed AA, the initial reaction sites are likely to occur at 6-membered ring structure (PC) or at 5-membered ring structure (PEC). Both experimental and theoretical results demonstrated PEC reaction mechanisms differed remarkably from that of PC process.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Facile synthesis of three-dimensionally ordered macroporous
           LaFeO3-supported gold nanoparticle catalysts with high catalytic activity
           and stability for soot combustion
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Yuechang Wei , Zhen Zhao , Jinqing Jiao , Jian Liu , Aijun Duan , Guiyuan Jiang
      A strategy for the facile synthesis of three-dimensionally ordered macroporous (3DOM) LaFeO3-supported gold nanoparticle catalysts is reported, namely in situ colloidal crystal template (CCT) method. The synthetic process involving in three steps are listed in detail, for example, the synthesis of monodisperse polymethyl methacrylate (PMMA) microspheres accompanied with polyelectrolyte brushes ([NH2]+·Cl−, PEBs), the preparation and assembling of CCT with spherical Au/PMMA compound, and the formation of 3DOM LaFeO3-supported gold catalysts via calcination to remove the CCT. All the catalysts have well-defined 3DOM structures, and gold nanoparticles are uniformly dispersed on the inner wall of 3DOM LaFeO3 support. 3DOM structure can improve the contact efficiency between soot particle and catalyst, and the strong metal (Au)-oxides (LaFeO3) interaction provides the active sites for activation of O2. 3DOM Au n /LaFeO3 catalysts obtained by in situ CCT method show high catalytic activity and stability for diesel soot oxidation. It suggests that 3DOM Au n /LaFeO3 catalysts are excellent systems for catalytic oxidation of solid soot particle, and the design concept and facile synthesis method of 3DOM oxide-supported Au nanoparticle catalysts can be extended to other metal/oxide compositions.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Three-dimensionally ordered macroporous Pr6O11 and Tb4O7 with mesoporous
           walls: Preparation, characterization, and catalytic activity for CO
           oxidation
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Yujuan Zhang , Jiguang Deng , Han Zhang , Yuxi Liu , Hongxing Dai
      Three-dimensionally ordered macroporous (3DOM) praseodymium oxide and terbium oxide with mesoporous walls and cubic crystal structures have been successfully fabricated with polymethyl methacrylate (PMMA) as hard template and F127, sucrose, and l-lysine as surfactant. Physicochemical properties of the materials were characterized by means of numerous techniques. It is shown that the Pr6O11 and Tb4O7 samples displayed a 3DOM architecture with polycrystalline wormhole-like mesoporous walls. The nature of surfactant and solvent and calcination condition had important effects on the pore structure and surface area of the final product. The introduction of surfactant and the partial carbonization of sucrose or l-lysine favored the enhancement in surface area of the 3DOM-structured materials, with the 3DOM Pr6O11 and Tb4O7 samples derived with F127 showing the highest surface areas of 32.0 and 25.2m2/g, respectively. The low-temperature reducibility of the Pr6O11 and Tb4O7 samples decreased according to the sequences of Pr6O11-F127>Pr6O11-Sucrose>Pr6O11-Lysine and Tb4O7-F127>Tb4O7-Sucrose>Tb4O7-Lysine, coinciding with the order in surface oxygen vacancy density. The improved physicochemical properties associated with the generation of 3DOM skeletons and wormhole-like mesoporous walls rendered the Pr6O11-F127 and Tb4O7-F127 samples to perform the best in the oxidation of CO.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Catalytic properties of copper-manganese mixed oxides supported on SiO2
           for benzene oxidation with ozone
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Hisahiro Einaga , Nanako Maeda , Shintaro Yamamoto , Yasutake Teraoka
      Catalytic oxidation of benzene was carried out over SiO2-supported manganese oxides and manganese-containing mixed oxides at 333–373K. The catalysts were prepared by impregnation methods from metal nitrate precursor and calcined at 673–873K. The addition of Cu, Ni, and Fe to Mn oxides suppressed the decrease of benzene oxidation activity and improved the steady state activity for benzene oxidation at 343K, whereas the addition of Co decreased the activity. The highest activity was obtained for Cu-Mn/SiO2 catalysts with the molar ratio of Cu-Mn 1:1. XRD studies revealed that Cu3Mn3O8 and CuMn2O4 spinel phases were formed in the Cu-Mn/SiO2 catalysts. The catalytic activity of Cu-Mn mixed oxides increased with the increase in their calcination temperature, in accordance with the increase in the spinel type Cu-Mn mixed oxide phases.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Mechanism of propene poisoning on Cu-SSZ-13 catalysts for SCR of NOx with
           NH3
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Lei Ma , Wenkang Su , Zhenguo Li , Junhua Li , Lixin Fu , Jiming Hao
      Application of Cu-exchanged chabazite catalysts for Urea-SCR of NO x in diesel engines is limited to some extent by catalyst deactivation with hydrocarbons (HCs). In this work, catalytic activity of commercial Cu-SSZ-13 catalysts with or without propene for selective catalytic reduction of NO x with ammonia (NH3-SCR) was tested, and results showed that the DeNO x activity was obviously inhibited in the whole temperatures, especially in medium temperatures. Furthermore, BET, NH3-TPD, NO x -TPD, and in situ DRIFTS were employed to elaborate the propene poisoning effects on Cu-SSZ-13 catalysts. In the low temperature ranges, the competitive adsorption process between NO x and C3H6 contributed to the deactivation of Cu-SSZ-13 catalysts. The presence of propene would inhibit the NO x adsorption and activation on the catalyst surface. In the medium temperature ranges, coke depositions were very critical for the deactivation of Cu-SSZ-13 catalysts. The active copper sites would be covered by the coke depositions, while the chabazite zeolite pores were also blocked by coke depositions. At higher temperatures above 450°C, coke could be quickly removed and the catalysts could be regenerated in the presence of rich oxygen.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Effect of the calcination temperature on the performance of a CeMoOx
           catalyst in the selective catalytic reduction of NOx with ammonia
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Jihui Wang , Xuesong Dong , Yujie Wang , Yongdan Li
      The effect of the calcination temperature on the structure and the catalytic performance of a CeMoOx mixed oxide catalyst in the selective catalytic reduction (SCR) of NOx with NH3 has been investigated. Compared to the catalyst calcined at 400°C, the one calcined at 500°C shows a performance of a slightly lower NOx conversion in the reaction temperature range below 200°C, and a higher NOx conversion above 350°C. However, further increase of the calcination temperature to 600 and 700°C leads to a drop of the NOx conversion and the N2 selectivity in both the low and high reaction temperature ranges. For the samples calcined at 600 and 700°C, Mo significantly enriches on the surface. These samples also favor the formation of N2O, and show a poor redox ability in NO oxidation reaction. The low ratio and low mobility of the surface chemisorbed oxygen correlates to the poor redox ability of the samples calcined at high temperatures. Furthermore, an abrupt drop of the surface area for the sample calcined at 600°C is observed and the destruction of acid sites during the high temperature calcination also recorded.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Multipollutant control of Hg/SO2/NO from coal-combustion flue gases using
           transition metal oxide-impregnated SCR catalysts
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Chun-Hsiang Chiu , Hsing-Cheng Hsi , Hong-Ping Lin
      This research investigated the effects of transition metal oxide impregnation on the physical/chemical properties and the multipollutant (i.e., Hg/SO2/NO) control of a V2O5-WO3/TiO2-SiO2 selective catalytic reduction (SCR) catalyst. Additional V, Mn, and Cu of 5wt% as their precursor metal hydroxides were impregnated onto the catalyst surface. The impregnated metal oxides presenting in nanoscales caused an increase in total surface area of catalysts. SEM images suggested that the raw and treated catalysts presenting as bean-shaped nanoparticles within 10–30nm. V4+/V5+, Mn4+, and Cu2+ were the major valence states presenting on the surface of VO x -, MnO x -, and CuO x -impregnated catalysts, respectively. Hg0 oxidation, SO2 removal, and NO reduction of the SCR catalyst can be enhanced after the metal oxide impregnation. VO x - and CuO x -impregnated catalysts had not only excellent Hg0 oxidation but also great NO reduction. However, the increase in SO2 removal after metal oxide impregnation, assumed to be partly caused from enhancing SO2–SO3 conversion, may be of concern considering the potential downstream corrosion. Langmuir–Hinshelwood model can successfully explain the Hg0 oxidation by VO x - and MnO x -impregnated catalysts. Overall, multipollutant emission control using surface-impregnated SCR catalysts can be practically applied at 350°C under the tested coal-combustion flue gas condition.
      Graphical abstract image

      PubDate: 2015-02-25T01:02:29Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245




      PubDate: 2015-02-25T01:02:29Z
       
  • Contents list
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245




      PubDate: 2015-02-25T01:02:29Z
       
  • Preface
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Soofin Cheng , Shawn D. Lin



      PubDate: 2015-02-25T01:02:29Z
       
  • Preparation of porous ceramometal composites through the stages of
           mechanical activation and hydrothermal partial oxidation of Me–Al
           powders
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Serguei F. Tikhov , Vladislav A. Sadykov , Konstantin R. Valeev , Aleksey N. Salanov , Svetlana V. Cherepanova , Yulia N. Bespalko , Vladimir E. Ramanenkau , Yavgenii Ya. Piatsiushyk , Sergey V. Dimov
      Basic stages of porous cermets preparation from MeAl (Me=Cr, Cu, Co, Fe) powders are elaborated including mechanical activation of Me–Al blends, soft hydrothermal treatment of mechanically alloyed blends followed by thermal treatment thus allowing to control their mechanical, thermophysical and textural properties. Ceramometal monoliths with metallic particles (up to 80wt.%) randomly distributed in the oxide matrix are characterized by the hierarchical pore structure with developed ultramacropores which provides their high permeability. Mesoporosity of ceramometal monoliths was developed by incorporation of mesoporous components into their structure. Monolithic catalysts based on these cermet substrates were shown to be promising for different fields of application in catalysis.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Preparation of bimetallic gold catalysts by redox reaction on
           oxide-supported metals for green chemistry applications
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): E.A. Redina , O.A. Kirichenko , A.A. Greish , A.V. Kucherov , O.P. Tkachenko , G.I. Kapustin , I.V. Mishin , L.M. Kustov
      The major problem in successful preparation of bimetallic supported catalysts is the formation of an extended contact area between the monometallic phases. The selective deposition of Au on the surface of nanoparticles of a primary oxide-supported metal has been performed by a redox method that is based on the reduction of the second metal (M2) ions with hydrogen adsorbed on the surface of first metal (M1) or with M1 itself. The gold containing bimetallic catalysts with different atomic ratios and metal combinations Au–M1 (M1 =Pd, Pt, Rh, Ru, and Au–RuO x ) deposited on oxide supports (TiO2, SiO2 or θ-Al2O3) have been prepared by this method with special emphasis on the preparation of low-loaded gold containing bimetallic catalysts. The samples were characterized by X-ray diffraction analysis (XRD), scanning transmission electron microscopy (STEM), temperature programmed reduction (TPR) analysis, CO adsorption, X-ray photoelectron spectroscopy (XPS), Diffuse reflectance Fourier-transform IR spectroscopy of adsorbed CO (DRIFTS-CO). By varying the conditions of the preparation procedure, the direct contact area was obtained either between two metal phases (Au/M1) or between metal and a metal oxide phase (Au/M1O x ) that changed the catalytic properties of primary supported M1. The prepared bimetallic catalysts exhibited the high activity in various reactions: from the Cl-VOC oxidative degradation to the up-to-date “green” reactions aimed at the synthesis of fine chemicals from ethanol and glycerol.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Application of the Catalyst Wet Pretreatment Method (CWPM) for catalytic
           direct synthesis of H2O2
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Pierdomenico Biasi , Stefano Sterchele , Francesco Bizzotto , Maela Manzoli , Sten Lindholm , Paul Ek , Johan Bobacka , Jyri-Pekka Mikkola , Tapio Salmi
      This work concerns a new technique to post-modify the catalytic material intended for use in H2O2 direct synthesis. The catalyst chosen was a commercially available 1wt.% Pd/C. The catalyst was modified with the so-called Catalyst Wet Pretreatment Method (CWPM) that is used to post-modify prepared catalysts with aqueous solutions of NaBr, in different concentrations. The performance of pristine and the pretreated materials were then compared in the H2O2 direct synthesis and characterized before and after the catalytic tests in order to understand the role of the different concentrations of bromide in the CWPM procedure. The surface features of the different catalysts were analyzed with CO chemisorption (metal dispersion and mean particle size), Transmission Electron Microscopy (TEM, for Pd morphology and Pd particle size distributions), Inductive Coupled Plasma (ICP, for Pd content) and Ion Chromatography (IC, for bromide content). Various features of the materials prepared with the CWPM were correlated with the catalytic performance. It was found that the bromide has an active role in the reconstruction of metal phase and it does not only act as a poison for the most active catalytic sites as often reported in literature. By using this new protocol, the production H2O2 was almost doubled compared to the non-modified material when no direct promoters were added to the reaction environment.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Mechanochemical preparation of Ag catalysts for the n-octane-SCR de-NOx
           reaction: Structural and reactivity effects
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Kathryn Ralphs , Sarayute Chansai , Christopher Hardacre , Robbie Burch , Sarah F.R. Taylor , Stuart L. James
      Mechanochemical preparation of Ag/Al2O3 catalysts used for the selective catalytic reduction of NO x using hydrocarbons has been shown to substantially increase the activity of the catalyst in comparison with Ag/Al2O3 prepared by wet impregnation. The effect of using different ball-milling experimental parameters on both the structure of the material as well as the catalyst activity has been investigated and the optimum conditions established. A phase transition from γ- to α-alumina was observed milling at high speeds which was found to result in lower catalyst activities. At lower milling speeds both fracturing and agglomeration of the alumina support can be observed depending on the grinding time. However, due to ball-milling, a general enhancement in the NO x reduction activity was observed for all catalysts compared with the conventionally prepared catalysts irrespective of the reductant used. Transient DRIFTS-MS experiments were performed to investigate the effect of H2 in the absence and presence of water on the SCR reaction over catalysts prepared by both ball milling and wet impregnation. In-situ DRIFTS-MS analysis revealed significant differences in both gas phase and surface species. Most notably, isocyanate species were formed significantly more quickly and at higher surface concentration in the case of the mechanochemically prepared catalyst.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Catalytically active gauze-supported skeletal nickel prepared from
           Ni–Zn alloys electrodeposited from an acetamide–dimethyl
           sulfone eutectic mixture
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Kam Loon Fow , Murugan Ganapathi , Ivo Stassen , Koen Binnemans , Jan Fransaer , Dirk E. De Vos
      Nickel–zinc alloys were electrodeposited on copper gauze from an acetamide–dimethyl sulfone eutectic mixture containing nickel chloride and zinc chloride. The as-deposited nickel–zinc alloys have compact microstructures with very small crystallites (approximately 3nm) and smooth surfaces. The nickel content could be varied between 20 and 90wt.% by controlling the temperature of the electrolyte. After alkaline leaching, a gauze-supported zinc based Raney nickel catalyst was obtained. The catalyst was benchmarked against commercial aluminum based Raney nickel in liquid phase hydrogenation of acetophenone. The gauze-supported zinc based skeletal nickel was more active and selective as compared to the commercial aluminum based Raney nickel. In addition, the gauze-supported zinc based Raney nickel catalyst could be reused without any hydrogen pretreatment. The activity of the reused catalyst decreased by 20%, but it retained its excellent selectivity.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Incorporation of the precursors of Mo and Ni oxides directly into the
           reaction mixture of sol–gel prepared γ-Al2O3-ZrO2 supports
           – Evaluation of the sulfided catalysts in the thiophene
           hydrodesulfurization
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Eduardo Prado Baston , Alexandre Boscaro França , Alano Vieira da Silva Neto , Ernesto Antonio Urquieta-González
      Mo and NiMo oxides supported on γ-Al2O3-ZrO2 were successful one-pot synthesized and characterized by XRF, XRD, N2 sorption, UVVISDRS and Zeta Potential. The sulfide catalysts were evaluated between 240 and 300°C in the thiophene HDS, used as a model reaction. XRD data evidenced the presence of γ-Al2O3 in the obtained solids, with its crystallinity being reduced with the incorporation of Zr and metallic species. XRD data also indicated that Zr, Ni and Mo were highly dispersed on the support. N2 sorption and UVVISDRS analyses showed that the one-pot synthesis procedure led to Mo and NiMo supported solids with high SBET areas and to Mo species with a low polymerization degree. Zeta Potential and H2-TPR analyses showed the influence of Ni and Zr in the Mo redox properties that contributed to the well HDS performance of the studied catalysts. The NiMo-γ-Al2O3-ZrO2 catalysts prepared in this work by a one-pot synthesis procedure, especially the NiMo/80A20Z, presented specific activities (QTOF) in the same order that those obtained for a commercial and for a traditional catalyst prepared by wet impregnation. The used one-pot method reduced the synthesis steps, minimizing the preparation time and the energy consumption.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Nickel silicides prepared from organometallic polymer as efficient
           catalyst towards hydrogenation of phenylacetylene
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Kaixuan Yang , Xiao Chen , Jingchao Guan , Changhai Liang
      A single-phase Ni2Si nanoparticle catalyst was prepared successfully by using temperature programmed pyrolysis method with polydimethylsilane-Ni(acac)2 as precursor and was characterized by thermogravimetric analysis, X-ray diffraction, X-ray photoelectron emission microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The pyrolysis temperature for generating pure Ni2Si in H2/Ar mixture is significantly lower than that for treatment in Ar. Ni2Si nanoparticles would be reduced to Ni nanoparticles by H2 with increasing pyrolysis temperature (>600°C). The catalytic hydrogenation of phenylacetylene on Ni2Si nanoparticles was investigated at 1.0MPa hydrogen and 80°C. The catalysts show suitable conversion of phenylacetylene and notable selectivity to styrene with 90%. In addition, catalytic performance on Ni2Si prominently improves after removing the SiO2 layer around Ni2Si nanoparticles by alkali treatment.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Photocatalytic property of strontium–niobium mixed oxide prepared by
           utilizing organic mediators to the overall splitting of H2O
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Yoshihisa Sakata , Hirokazu Munemasa , Shinichiro Suenaga , Takao Onishi , Hayao Imamura , Junko N. Kondo
      The effects of the polymer precursor in polymerizable complex (PC) method for the preparation of a Sr–Nb mixed oxide photocatalyst were studied. A polymer made of citric acid and ethylene glycol, which is generally applied in the PC method, as well as that made of succinic acid and 2-(2-aminoethylamino)ethanol (AEEA) were used as polymer chelating ligands. The photocatalytic activity of prepared mixed oxides for the overall H2O splitting depended on the oxide crystal structure, which was affected by the chelating complex polymer precursors and the calcination temperature. In particular, the Sr–Nb mixed oxide prepared from succinic acid and AEEA precursors showed the significantly high photocatalytic activity for the overall splitting of H2O after calcination at 973K. The influences of the origin of polymer precursors to the crystal structure and the composition of the Sr–Nb mixed oxide and its photocatalytic performance to the overall H2O splitting are discussed.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Synthesis of graphene-like MoS2 nanowall/graphene nanosheet hybrid
           materials with high lithium storage performance
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Jin Guo , Xiao Chen , Shaohua Jin , Mingming Zhang , Changhai Liang
      A facile method to synthesize graphene-like MoS2 nanowall/graphene sheet (GL-MoS2 nanowall/GNS) composites has been developed through a solvothermal method, and followed by annealing at 400°C under Ar. The characterization results indicate that the thin flaky wall type GL-MoS2 nanowall was supported well on the crumpled graphene flakes with good dispersion. The as-obtained nanowall-nanosheet hybrids are more robust and still retain the reversible capacity of 700mA h g−1 after 100 cycles at a charge–discharge rate of 500mAg−1. The outstanding performance in electrochemistry is attributed to both the robust nanocomposite structure and the synergistic interactions between graphene and GL-MoS2 nanowall, which makes it an efficient stable lithium storage material.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Improvement in the coating homogeneity in electrosynthesized Rh structured
           catalysts for the partial oxidation of methane
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Patricia Benito , Marco Monti , Wout De Nolf , Gert Nuyts , Gertjan Janssen , Giuseppe Fornasari , Erika Scavetta , Francesco Basile , Koen Janssens , Francesca Ospitali , Domenica Tonelli , Angelo Vaccari
      The precipitation of Rh/Mg/Al and Rh/Al hydroxides on the surface of FeCrAlloy foams by a base electrogeneration method was investigated to improve the properties of the deposited film (homogeneity and composition) and therefore the performances of the structured catalysts, obtained by calcination, in the Catalytic Partial Oxidation of CH4 to syngas. The work focussed on decreasing current gradients within open-cell foam cylinders by increasing the number of electrical contacts from 1 to 3 points to promote a more homogeneous precipitation of the hydroxides. Electrochemical and catalytic tests as well as SEM/EDS and μ-XRF/XRD analyses allowed to correlate the effect of the number of electrical contact points with materials properties. Lastly, syntheses were performed on Pt plates to study the effect of the electrical behaviour and shape of the support on the composition of the film. A more homogeneous coating of the foam surface was achieved by adopting a configuration with 3 contact points since the reduction of nitrates and water molecules that generates the basic media in the vicinity of the support was enhanced. Layer thicknesses up to 5–15μm were deposited; however, the sequential precipitation of a film with composition closer to the expected one and a layer enriched in Al and Rh (outer layer) was not avoided. The improvement in the coating gave rise to enhanced performances for a sample prepared at −1.1V for 3000s. Contrarily, the low adherence of the outer layer in a sample prepared at −1.2V for 2000s during both calcination and catalytic tests may be responsible of the unexpected decrease in catalytic performances. The same sequential precipitation was observed by performing the syntheses on Pt plates, showing that the electrical nature the support did not play a key role on this phenomenon.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Theoretical study on the reaction mechanisms of the aldol-condensation of
           5-hydroxymethylfurfural with acetone catalyzed by MgO and MgO+
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Shu Chen , Huaqing Yang , Changwei Hu
      The reaction mechanisms and the turnover frequencies of the aldol-condensation of 5-hydroxymethylfurfural (HMF) with acetone catalyzed by the neutral MgO and the cationic MgO+ have been theoretically investigated at B3LYP/6-311++G(d,p) level, using the polarizable continuum model in aqueous solution at the temperature of 326K. The aldol-condensation of HMF with acetone catalyzed by the neutral MgO or the cationic MgO+ is thermodynamically favorable. The reaction mechanism involves the crucial reaction steps of H-shift and CC bond formation, while the rate-determining step is concerned to the H-shift. The Lewis acidity of the cationic MgO+ makes it exhibit better catalytic performance than the neutral MgO. Water, as a bridge in the H-shift, interacts with both the neutral MgO and the cationic MgO+ moieties, leading to the Brønsted basicity, and then promoting the catalytic performance both of the neutral MgO and the cationic MgO+. Both the Lewis acidity and Brønsted basicity of active sites can enhance the catalytic performance in the aldol-condensation of HMF with acetone.
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      PubDate: 2015-02-25T01:02:29Z
       
  • The rational synthesis of Pt-Pd bimetallic catalysts by electrostatic
           adsorption
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Hye-Ran Cho , John R. Regalbuto
      To improve the often poor metal dispersion and poor metal1–metal2 contact of bimetallic catalysts prepared by dry impregnation (incipient wetness), we demonstrate several ways to employ strong electrostatic adsorption using Pt and Pd over silica, alumina, carbon, and oxidized carbon. Metal uptake versus pH was monitored for single metal solutions and mixtures of metal precursors. Catalysts were characterized by powder XRD, aberration-corrected STEM imaging, and EDXS line scans and mapping of individual nanoparticles. Electrostatic adsorption of mixed metal precursors (co-SEA) results in well dispersed, homogeneously alloyed nanoparticles, while sequential SEA gives well dispersed nanoparticles with core–shell morphologies. Shell metal loading can be increased by additional cycles of SEA, which gives some flexibility at catalyst composition in exchange for more synthesis steps. Dry impregnation yields larger, agglomerated, inhomogeneously alloyed particles.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Kaolinite-titanium oxide nanocomposites prepared via sol-gel as
           heterogeneous photocatalysts for dyes degradation
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Lorrana Vietro Barbosa , Liziane Marçal , Eduardo J. Nassar , Paulo S. Calefi , Miguel A. Vicente , Raquel Trujillano , Vicente Rives , Antonio Gil , Sophia A. Korili , Katia J. Ciuffi , Emerson H. de Faria
      A purified natural kaolinite was functionalized with titanium(IV) isopropoxide via the hydrolytic sol-gel route and thermally treated at several temperatures, between 100 and 1000°C, for 24h. The resulting solids were used for photodegradation (λ=365nm, 30W) of Methylene Blue (MB) and Methyl Orange II (MOII) dyes. All the solids efficiently degraded the dyes and almost total bleaching of the aqueous solutions was observed after 1h. The best results were found for the solid heated at 400°C, which degraded 93% of MOII and 99% of MB. Comparative studies with titanium oxide P25 from Degussa were tested and the results reveal lower yields than our systems (45% MB and 15% MOII, 1h). Kaolinite could promote the dispersion of TiO2 on the clay surface allowing a fast degradation of dyes. This effect was confirmed by comparison of the results from isolated components (titanium oxide and kaolinite) and titanium oxide-kaolinite nanocomposites.
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      PubDate: 2015-02-25T01:02:29Z
       
  • A novel preparation method for “small” eggshell
           Co/γ-Al2O3 catalysts: A promising catalytic system for compact
           Fischer–Tropsch reactors
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Laura Fratalocchi , Carlo Giorgio Visconti , Luca Lietti , Enrico Tronconi , Ugo Cornaro , Stefano Rossini
      Due to the need of limiting pressure drop, and the consequent necessity of adopting “big” catalyst pellets, low-temperature Fischer–Tropsch synthesis in industrial fixed-bed reactors may suffer of strong intra-particle mass transport limitations, which are known to result in decreased CO conversion rate and C5 + selectivity. Upon decoupling the pellet diameter and the diffusive length, eggshell catalysts represent an engineering solution for the intensification of the Fischer–Tropsch reactors. In this work, preparation, characterization and testing of impregnated Co/γ-Al2O3 eggshell catalysts with sharply defined outer shell regions are reported. The method developed to impregnate the active phase only on the outer layer of the support is based on the “protection” of the inner pores of the support with an organic liquid and on the control of the contact time between the impregnating solution and the protected support. The method is particularly suitable to prepare “small” eggshell pellets, with diameters below 1mm, to be used in compact FT reactors. It is shown that 600μm pellets, with catalytically active layers 75μm thick, grant a remarkable combination of high CO conversion rate and high C5 + selectivity, thus resulting extremely interesting for operations in reactors 3–6m long.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Ionic liquid-initiated polymerization of epoxides: A useful strategy for
           the preparation of Pd-doped polyether catalysts
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Ulrich Arnold , Christiane Altesleben , Silke Behrens , Sarah Essig , Ludger Lautenschütz , Dieter Schild , Jörg Sauer
      Palladium compounds (Pd(OAc)2 and Pd(acac)2) were dissolved in commercially available epoxy resins (glycidyl derivatives of bisphenol A and p-aminophenol) and the formulations were polymerized employing the ionic liquid 1-ethyl-2-methylimidazolium acetate (EMIM acetate) as polymerization initiator. Thus, palladium species could be incorporated in the network of the resulting polyether materials. Polymerization reactions were investigated by DSC and the curing behavior of different formulations was compared. High polymerization enthalpies were observed indicating high crosslinking in the materials. Accordingly, the materials exhibited high glass transition temperatures and thermogravimetric data revealed high thermal stability. Due to the good solubility of the palladium compounds in the epoxy resins, a widely homogeneous dispersion of palladium species in the polyether matrix could be realized. This was confirmed by SEM-EDX and TEM measurements. XPS measurements revealed that reduction of Pd(II) to Pd(0) species occurred during catalyst preparation and this was also proven by XRD. The materials were ground and successfully employed as catalysts for the hydrogenation of several alkenes under mild reaction conditions. High conversions and selectivities could be reached within a few hours at room temperature and moderate hydrogen pressure of 2.5bar. Palladium leaching from the catalysts to reaction solutions was investigated. To determine very low quantities, metal concentrations were enriched by removal of volatile components. Subsequent ICP-AES measurements revealed low palladium contents in the range of a few μg. These amounts correspond to values around 0.007% with respect to palladium originally loaded on the polymer. Catalyst recycling experiments were also carried out and it was shown that the catalysts can be employed in numerous consecutive reactions without any catalyst treatment and without loss of activity. Within a series of reactions, palladium leaching decreased while catalytic activity was not affected.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Pd–Cu interaction in Pd/Cu-MCM-41 catalysts: Effect of silica source
           and metal content
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Patricia Benito , Manuel Gregori , Sara Andreoli , Giuseppe Fornasari , Francesca Ospitali , Stefano Millefanti , Maria Sol Avila , Teresita F. Garetto , Stefania Albonetti
      Pd/Cu-MCM-41 catalysts for the hydrodechlorination of CF3OCFClCF2Cl to CF3OCFCF2 were prepared. Palladium- and copper-containing samples (Pd/Cu=1 molar ratio) were synthesized by adding Pd2+ and Cu2+ during the formation of MCM-41, and then the slurries were aged by microwave-hydrothermal treatment. The effect of the silica source (silicates or TEOS) and total metal loading (2.4 and 4.0wt.%) on the chemical–physical properties and catalytic performances was studied. Bimetallic silicate-derived samples show features similar to those of the pristine MCM-41, regardless of the total metal content. Conversely, the long-range order of the mesoporous structure decreases for TEOS-derived catalysts, and large metal contents seem to alter the structure for these materials. During template removal by thermal treatment, palladium and copper are on the surface of MCM-41 particles, forming Pd1−x Cu x O solid solutions whose composition is silica source-dependent. The amount of copper in Pd1−x Cu x O is greater for TEOS-derived samples. After reduction, both Pd- and Cu-enriched alloys were found by XRD in silicate-derived samples, while XPS measurements indicated that the surface of the catalyst is enriched with copper. XRD and XPS analyses on TEOS samples indicated that the surface Cu/Pd ratio is closer to 1, and fcc PdCu alloys with a high copper content were identified. The composition of metallic particles modifies the selectivity, TEOS-derived catalysts being more selective to the target CF3OCFCF2.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Design of multicomponent aerogels and their performance in photocatalytic
           hydrogen production
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Rafael O. da Silva , Florian J. Heiligtag , Michael Karnahl , Henrik Junge , Markus Niederberger , Sebastian Wohlrab
      Multicomponent aerogels were prepared from the preformed components (i) crystalline TiO2 nanoparticles, (ii) Pt nanoparticles as well as (iii) multilayer reduced graphene oxide (m-rGO) and were subsequently tested for photocatalytic H2 evolution. The multicomponent photocatalysts showed a 3D architecture consisting of crosslinked TiO2 nanoparticles which are decorated with (1–2nm) platinum nanoparticles with embedded m-rGO. The three-component materials retained the mesoporosity and high surface area of pure TiO2 aerogels, as illustrated by transmission electron microscopy and nitrogen sorption experiments. This architecture is responsible for the enhancement of the photocatalytic activity, which reached a maximum hydrogen production rate of 11.61mmolH2 g−1 h−1 for the TiO2 aerogel with a cocatalyst content of 0.4wt% Pt. In comparison, a Pt/TiO2 reference powder produced only about 3.28mmolH2 g−1 h−1. In this way, the aerogel architecture enables the design of compositions other than Pt/TiO2 or even the co-assembly of further active materials such as conducting components into the aerogel matrix as shown by the addition of m-rGO to the Pt/TiO2 aerogels.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Ternary and quaternary Cr or Ga-containing ex-LDH
           catalysts—Influence of the additional oxides onto the microstructure
           and activity of Cu/ZnAl2O4 catalysts
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Stefanie Kühl , Julia Schumann , Igor Kasatkin , Michael Hävecker , Robert Schlögl , Malte Behrens
      The stepwise substitution of Al by Cr and Ga leads to quaternary LDH precursors for Cu/ZnM2O4 (M=Al, Ga, Cr) catalysts. With the substitution of Al by Cr the interaction of the Cu phase with the oxide matrix is gradually weakened, which is caused by the participation of the chromium oxide phase in the redox processes during catalyst preparation. Such reactive Cr oxide matrix is less efficient than the inert Al oxide matrix in stabilizing the special microstructure of Cu/ZnM2O4 catalysts. These weakened interactions led to a lowering of the Cu particle embedment, coinciding with a pronounced Cu crystallite growth during reduction. Both effects partially compensate each other and a maximum in Cu surface area is observed for intermediate Cr contents. In the Ga-substituted catalysts, two distinct Cu species were found for high Ga contents. This is attributed to the presence of partially crystalline spinel and the resulting different strength of interface interaction of the CuO phase with the crystalline and the amorphous oxide. After reduction Cu catalysts with similar average Cu particle sizes as well as Cu surface areas were obtained. In both sample series, the catalytic activity in methanol synthesis does not scale with the Cu surface area and the experiments show that a strong interaction to the oxide is necessary to gain stability and activity of the Cu phase. Al substitution thus confirms that interface interactions between Cu and the oxide seem to beneficially affect the activity of the Cu particles and the optimal catalyst requires a compromise of exposed surface and interface.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Role of shaping in the preparation of heterogeneous catalysts: Tableting
           and slip-casting of oxidation catalysts
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): V.G. Baldovino-Medrano , M.T. Le , I. Van Driessche , E. Bruneel , C. Alcázar , M.T. Colomer , R. Moreno , A. Florencie , B. Farin , E.M. Gaigneaux
      The process and impact of shaping mixed vanadium aluminum (hydr)oxides, VAlOH and VAlO, respectively, and BiMo catalysts by tableting and slip-casting were examined. Graphite (G) was employed as a shaping agent for tableting. Without it tableting was impracticable. Graphite was found to enhance the mechanical resistance of VAlOH-xG and BiMo-xG and changed the surface area by increasing it for the non-porous BiMo and by decreasing it for the mesoporous VAlOH. In addition, graphite modified the catalytic performance despite changing neither the chemical nor the structural state of the base VAlO(H) and BiMo catalysts. A positive effect on the performance of VAlO-xG in propane oxidative dehydrogenation was found. It was proposed that catalytic active sites are formed on graphite during calcination. Conversely, graphite was harmful for non-calcined VAlOH-xG and BiMo-xG. On the other hand, the preparation of chemically and physically stable VAlO(H) suspensions for slip-casting was accomplished. Chemical stability was achieved at pHs near the isoelectric point of these catalysts. For physical stability, the use of a dispersing agent, poly(acrylic acid), combined with a control of the solids concentration was necessary. A simple and reliable method for preparing VAlOH and BiMo pellets by slip-casting was thus developed with the use of colloidal silica as binding agent. The so prepared pellets were mechanically resistant and kept the surface area of the base materials. A decrease in the surface concentration of the active metals due to surface active site masking by silicon for VAlOH-xSi and BiMo-xSi led to an inferior catalytic performance.
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      PubDate: 2015-02-25T01:02:29Z
       
  • A universal method to form Pd nanoparticles on low-surface-area inorganic
           powders and their support-dependent catalytic activity in hydrogenation of
           maleic acid
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): M.A. Kulagina , E.Yu. Gerasimov , T.Yu. Kardash , P.A. Simonov , A.V. Romanenko
      A simple method for preparation of Pd catalysts supported on low-surface-area inorganic powders as carbons, oxides (SiO2, diatomites, WO3, Ta2O5, Nb2O5, V2O5, TiO2, CeO2, ZrO2, Ga2O3, In2O3, Cr2O3, Fe2O3, Al2O3) and salts (CaF2, BaSO4, Ca3(PO4)2) was developed. It implies hydrolytic deposition of Pd(II) precursors onto a support in basic solutions. Regularities of the hydrolysis process without and in the presence of the support are studied by various physicochemical methods. A scheme of the formation of catalytically active component was put forward. Reduced with H2 at 50–120°C, the palladium catalysts demonstrate strong dependence of their specific activity in hydrogenation of aqueous maleic acid on the support nature. TOF value for palladium nanoparticles supported onto an oxide surface slows down with increasing polarizing ability of cations in the lattice of the oxide, that testifies to the influence of the electrostatic field intensity at the support surface on the reaction rate.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Morphological effects of CeO2 nanostructures for catalytic soot combustion
           of CuO/CeO2
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Keizo Nakagawa , Takuya Ohshima , Yoshiki Tezuka , Megumi Katayama , Masahiro Katoh , Sigeru Sugiyama
      Rod and ellipsoid shaped CeO2 nanostructures were prepared using self-assemblies of amine surfactants as templates through the decomposition of cerium carbonate hydroxide. The morphologies of the products were greatly influenced by amine surfactants with different alkyl chain lengths. Different shaped CeO2 nanostructures supported CuO (CuO/CeO2) catalysts were prepared by a conventional impregnation method. CuO/CeO2 nanorods showed high reducibility at lower temperature, larger amount of oxygen species from H2-TPR and possessed larger external surface area and mesopore volume from N2 adsorption as compared with CuO/CeO2 with uncontrolled morphology. These catalysts showed effective soot combustion at lower temperature under tight contact condition using carbon black (CB) as a model of soot particle, as compared with CuO/CeO2 with uncontrolled morphology. Larger external surface area and mesopore volume of CuO/CeO2 catalysts contributed to the improved physical contact condition between CeO2 catalysts and aggregated CBs. Surface reducibility and the improved physical contact condition affected greatly their catalytic activity for soot combustion.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Coprecipitation: An excellent tool for the synthesis of supported metal
           catalysts – From the understanding of the well known recipes to new
           materials
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Malte Behrens
      Constant-pH co-precipitation is a standard synthesis technique for catalyst precursors. The general steps of this synthesis route are described in this work using the successfully applied industrial synthesis of the Cu/ZnO/(Al2O3) catalyst for methanol synthesis as an example. Therein, co-precipitation leads to well-defined and crystalline precursor compound with a mixed cationic lattice that contains all metal species of the final catalyst. The anions are thermally decomposed to give the mixed oxides and the noblest component, in this current case copper, finally segregates on a nano-metric level to yield supported and uniform metal nanoparticles. Recent examples of the application of this synthesis concept for supported catalysts are reported with an emphasis on the layered double hydroxide precursor (Cu,Zn,Al; Ni,Mg,Al; Pd,Mg,Al; Pd,Mg,Ga). This precursor material is very versatile and can lead to highly loaded base metal as well as to mono- and bi-metallic highly dispersed noble metal catalysts.
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      PubDate: 2015-02-25T01:02:29Z
       
  • A temperature programmed desorption study of the interaction of ethyl
           cyanoacetate and benzaldehyde on metal oxide surfaces
    • Abstract: Publication date: 1 May 2015
      Source:Catalysis Today, Volume 245
      Author(s): Jerry Pui Ho Li , Michael Stockenhuber
      Reagents from a base catalysed condensation reaction (Knoevenagel condensation reaction between ethyl cyanoacetate and benzaldehyde), were adsorbed on ZnO and Al2O3 catalyst surfaces and subject to temperature programmed desorption experiments, monitored using mass spectrometry. Ethyl formate, ketenimine species, carbon dioxide and carbon monoxide were desorption products from ethyl cyanoacetate, while benzene, carbon dioxide and carbon monoxide were desorbed from the catalysts loaded with benzaldehyde. The formation of the ketenimine species was confirmed by in situ FTIR experiments. The observation of the decomposition species further substantiates a proposed reaction mechanism for the Knoevenagel condensation reaction on the catalyst surface of some oxide catalysts.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Catalysts based on pillared clays for the oxidation of chlorobenzene
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): A. Aznárez , R. Delaigle , P. Eloy , E.M. Gaigneaux , S.A. Korili , A. Gil
      The aim of this work was to reveal the main factors which affect the oxidation of chlorobenzene (PhCl) over palladium and platinum supported on alumina pillared clays. The catalysts were prepared by wet impregnation of an alumina-pillared montmorillonite (Al-PILC) with palladium and platinum solutions and characterized by several physicochemical techniques before and after the catalytic tests. During oxidation of PhCl over the catalysts, the formation of carbon dioxide along with small quantities of carbon monoxide, PhCl x and coke was found. The nature of the supported metal, the temperature, the metal loading, the support, and the time on stream, are factors affecting the combustion of PhCl.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Counteranion effects on the catalytic activity of copper salts immobilized
           on the 2,2′-bipyridine-functionalized metal–organic framework
           MOF-253
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Pieterjan Valvekens , Eric D. Bloch , Jeffrey R. Long , Rob Ameloot , Dirk E. De Vos
      The charge-neutral, aluminium-based metal–organic framework containing accessible 2,2′-bipyridine (bpy) sites, MOF-253, is a suitable host material for the immobilization of various copper catalysts. The catalytic performance of CuCl2, Cu(NO3)2, Cu(BF4)2 and Cu(CF3SO3)2 before and after coordination to the bpy ligands in MOF-253 was studied in the Meinwald rearrangement of α-pinene oxide to campholenic aldehyde (CA). The coordination environment of Cu2+ in MOF-253 was further studied via EPR spectroscopy. Although the catalytic activity of the copper salts decreased upon heterogenization through coordination with the bpy linker, the selectivity to campholenic aldehyde markedly increased. Furthermore, the catalytic performance of the MOF loaded with copper salts was shown to vary greatly with the choice of charge compensating anion, allowing for improvement of the heterogeneous catalyst.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Ti3+-containing titania: Synthesis tactics and photocatalytic performance
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Wibawa H. Saputera , Guido Mul , Mohamed S. Hamdy
      Three different synthesis techniques were applied to prepare Ti3+-containing TiO2. The first is a self-doped technique in which TiO2 was reduced in situ at 500°C by NO and CO gases to produce blue powder (blue titania). The second method is a calcination treatment of a physical mixture consisting of commercial TiO2 Hombikat and Ti2O3 at 600°C to produce a yellow powder (composite). The third technique is hydrogenation of different commercially available titania (Rutile, P25, and Hombikat) samples at elevated temperatures to produce yellowish white powders. The prepared samples were characterized by means of X-ray diffraction (XRD), nitrogen physisorption measurements, diffuse reflectance UV–Vis and Raman spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of the prepared materials was tested in the decolourization reaction of methyl orange (MO) under the illumination of ‘black light’ (λ =375nm). The kinetic data of the photocatalytic reactions show that reduced titania samples exhibit higher photocatalytic activity than titania. Furthermore, the highest photocatalytic activity was obtained by hydrogenation of P25 at 500°C. Moreover, the photo-deposition of platinum nanoparticles on the prepared materials enhanced the photocatalytic performance significantly. Titania samples which were firstly platinized and then hydrogenated were much more active than samples which were hydrogenated first and then platinized. The stability of the Ti3+ containing titania samples in aqueous conditions was found to be low, and needs to be improved to allow application in practice.
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      PubDate: 2015-02-25T01:02:29Z
       
  • Chemisorption–XRD particle size discrepancy of carbon supported
           palladium: Carbon decoration of Pd?
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): John Meynard M. Tengco , Yuliana K. Lugo-José , John R. Monnier , John R. Regalbuto
      A systematic discrepancy is often observed between chemisorption versus X-ray diffraction and/or electron microscopy-determined nanoparticle size estimates for metals supported on carbon. It is hypothesized that lower than expected chemisorption capacity is due to decoration of the metal surface by the carbon support. To test this, a series of carbon supported Pd nanoparticles with different pretreatments was prepared and analyzed using Temperature Programmed Oxidation. Carbon oxidation peaks distinct from high temperature bulk carbon burn off were observed for all samples at around 250°C and 300°C. A short oxidation at the latter temperature appears to remove the decorating layer as the TPO peaks disappear and the reduced metal surface chemisorbs at close to the expected capacity.
      Graphical abstract image

      PubDate: 2015-02-25T01:02:29Z
       
  • Can Ni phosphides become viable hydroprocessing catalysts?
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): S. Soled , S. Miseo , J. Baumgartner , J. Guzman , T. Bolin , R. Meyer
      We prepared higher surface area nickel phosphides than are normally found by reducing nickel phosphate. To do this, we hydrothermally synthesized Ni hydroxy phosphite precursors with low levels of molybdenum substitution. The molybdenum substitution increases the surface area of these precursors. During pretreatment in a sulfiding atmosphere (such as H2S/H2) dispersed islands of MoS2 segregate from the precursor and provide a pathway for H2 dissociation that allows reduction of the phosphite precursor to nickel phosphide at substantially lower temperatures than in the absence of MoS2. The results reported here show that to create nickel phosphides with comparable activity to conventional supported sulfide catalysts, one would have to synthesize the phosphide with surface areas exceeding 400m2/g (i.e. with nanoparticles less than 30Å in lateral dimension).
      Graphical abstract image

      PubDate: 2015-02-25T01:02:29Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246




      PubDate: 2015-02-25T01:02:29Z
       
  • Effects of amine structure and base strength on acid–base
           cooperative aldol condensation
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Jeroen Lauwaert , Els De Canck , Dolores Esquivel , Pascal Van Der Voort , Joris W. Thybaut , Guy B. Marin
      Aminated silica materials are known to efficiently catalyse aldol condensations, especially when silanol groups are neighbouring the amine function. The effect of the amine structure and base strength has been analysed experimentally and by kinetic modelling using commercially available precursors to graft primary, secondary and tertiary amines on the silica surface. While primary amines are arranged in a clustered manner on the catalyst surface, secondary amines are arranged randomly which results in a higher percentage of promoted amines in the low silanol-to-amine ratio range. An enamine compound formed by the reaction between the amine active site and acetone has been identified as the key intermediate to explain the experimental observations. In the case of a primary amine this enamine intermediate can form an inhibiting imine with which it is in equilibrium. As a secondary amine has only one hydrogen atom bonded to the nitrogen atom, the inhibiting imine cannot be formed, resulting in a comparatively higher concentration of reactive enamines on the catalyst surface. In case of a tertiary amine the formation of the reactive intermediate is impossible due to the absence of any hydrogen atom bonded to the nitrogen atom. The activation entropies of all reaction steps occurring on the amine sites, as obtained by regression, could be correlated to the deprotonation entropies of the amine sites. As the deprotonation enthalpy does not account for steric effects, no such correlation could be found between the activation energies of these reaction steps and the deprotonation enthalpies of the amine sites.
      Graphical abstract image

      PubDate: 2015-02-25T01:02:29Z
       
  • Tailoring preparation, structure and photocatalytic activity of
           layer-by-layer films for degradation of different target molecules
    • Abstract: Publication date: 15 May 2015
      Source:Catalysis Today, Volume 246
      Author(s): Jan Rongé , Jeroen Bets , Shruti Pattanaik , Tom Bosserez , Sara Borellini , Sreeprasanth Pulinthanathu Sree , Gero Decher , Johan A. Martens
      Photocatalytic thin films composed of titanium dioxide and poly(styrene sulfonate) with hierarchical porosity and high transparency were prepared by the layer-by-layer self-assembly method. The influence of preparation conditions on the structure and photocatalytic activity of the films was investigated. It was found there is no need to reach adsorption equilibrium during layer deposition. Using very short deposition times, films with better transparency and higher activity for methylene blue photo-oxidation were obtained. Diffusion limitations due to strong adsorption of dye molecules and ammonia to the polyelectrolyte were revealed. These results indicate that films could be devised to selectively degrade specific target molecules in a mixture. The films were deposited on a three-dimensional carbon substrate and successfully demonstrated in a photoelectrochemical water splitting experiment.
      Graphical abstract image

      PubDate: 2015-02-25T01:02:29Z
       
 
 
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