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Journal Cover Catalysis Today
  [SJR: 1.348]   [H-I: 164]   [8 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [3043 journals]
  • One-pot synthesis of benzimidazole using DMF as a multitasking reagent in
           presence CuFe2O4
    • Abstract: Publication date: Available online 16 October 2017
      Source:Catalysis Today
      Author(s): Kalidas B. Rasal, Ganapati D. Yadav
      One pot synthesis of benzimidazole from o-nitroaniline was achieved by using CuFe2O4 as a catalyst. It comprises the reduction of o-nitroaniline followed by cyclization, without using an external H2 source. The thermal decomposition of DMF in situ generates CO, which undergo water gas shift reaction (WGSR) in presence of CuFe2O4 to produce hydrogen. It reduces −NO2 (nitroaniline) to −NH2 (o-phenylenediamine, OPD). The further cyclisation of OPD to benzimidazole was done by using DMF as a C1 source, in presence of magnetically separable CuFe2O4 as catalyst. This is the first example of its kind being reported here. The catalyst was prepared by a simple hydrothermal method, with the environmentally benign starting material. CuFe2O4 is cheap and reusable having very low toxicity. This is an economical synthetic protocol for benzimidazole from o-nitroaniline with 100% conversion in 12h with 97.5% selectivity. A variety of o-nitroaniline substrates were studied for this protocol with excellent conversion and selectivity.
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      PubDate: 2017-10-18T00:32:47Z
       
  • Membrane assisted propane dehydrogenation: experimental investigation and
           mathematical modelling of catalytic reactions
    • Abstract: Publication date: Available online 16 October 2017
      Source:Catalysis Today
      Author(s): Antonio Ricca, Francesca Montella, Gaetano Iaquaniello, Emma Palo, Annarita Salladini, Vincenzo Palma
      Selective propane dehydrogenation is one of the commercialised technology for the production of propylene. The main drawback of such process is closely linked to the high temperature required to reach a sustainable propane conversion that affects catalyst stability owing to coke formation on the catalyst surface. Accordingly, a periodic regeneration of catalytic bed is required. The simultaneous actions of performing the reaction in the presence of Pd-based membrane and optimization of employed catalyst could lead to a substantial reduction in the operating reaction temperature, decreasing the extent of reactions responsible for coke formation. To this aim a comprehensive study of catalytic behaviour is essential and accordingly a dedicated experimental program is reported for propane dehydrogenation on a Pt-based catalyst, by focusing the attention on the operating conditions compatible with membrane integration. Both activity and stability of the catalyst system was evaluated in the investigated conditions, in addition mathematical models were optimized to effectively describe the system behaviour and the catalyst deactivation.
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      PubDate: 2017-10-18T00:32:47Z
       
  • Pd catalysts supported on hydrogen titanate nanotubes for Suzuki-Miyaura
           cross-coupling reactions
    • Abstract: Publication date: Available online 16 October 2017
      Source:Catalysis Today
      Author(s): Mark E. Martínez-Klimov, Patricia Hernández-Hipólito, Marcos Martínez-García, Tatiana E. Klimova
      Palladium catalysts supported on hydrogen titanate nanotubes (HTN) were prepared by impregnation of palladium(II) acetate, characterized by N2 physisorption, powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and tested in the Suzuki-Miyaura cross-coupling reactions between 4-bromobenzaldehyde and phenylboronic acid (reaction 1) or 4-hydroxyphenylboronic acid (reaction 2). The aim of this work was to determine the activity of these catalysts in the Suzuki-Miyaura reactions and the possibility of their reusing in several catalytic cycles. The results showed that 3.6wt. % of Pd was the optimum metal loading in the Pd(x)/HTN catalysts. The Pd(3.6)/HTN catalyst resulted in 97 and 88% yields of biphenyl products in the cross-coupling reactions 1 and 2, respectively, and its activity decreased by about 10% after five catalytic cycles. This deactivation was attributed to different reasons: an amount of the catalyst was lost during its separation by filtration after each catalytic cycle, Pd leaching, the presence of organic and inorganic species on the spent catalyst’s surface acting as poisons, as well as the agglomeration of palladium species.
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      PubDate: 2017-10-18T00:32:47Z
       
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296


      PubDate: 2017-09-26T09:34:37Z
       
  • Contents list
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296


      PubDate: 2017-09-26T09:34:37Z
       
  • XXV Iberoamerican Congress on Catalysis (CICat-2016)
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Juan Bussi, Jorge Castiglioni, Carlos R. Apesteguía


      PubDate: 2017-09-26T09:34:37Z
       
  • V- and Nb-containing tungsten bronzes catalysts for the aerobic
           transformation of ethanol and glycerol. Bulk and supported materials
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): N. La Salvia, D. Delgado, L. Ruiz-Rodríguez, L. Nadji, A. Massó, J.M. López Nieto
      This work report the applicability of reflux to the synthesis of supported tungsten bronzes (i.e. W-V-O and W-Nb-O), using mesoporous KIT-6 as inert support. For comparison, the corresponding bulk materials prepared by reflux or by hydrothermal synthesis have been also prepared. The catalysts were characterized by several techniques (X-ray diffraction, N2 adsorption, temperature programmed desorption (NH3), and Raman and FTIR spectroscopies) and tested in the selective aerobic transformation of ethanol and glycerol. These results demonstrate the formation of V- and Nb-containing tungsten oxide bronzes in all of the heat-treated samples (bulk and supported materials), as well as the effective incorporation of metals (V or Nb) in the framework of tungsten bronzes. During the aerobic transformation of ethanol, diethyl ether and ethylene (in Nb-containing catalysts) and acetaldehyde, diethyl ether and ethylene (in V-containing catalysts) were the main reaction products, with very small formation of carbon oxides. During the aerobic transformation of glycerol, acrolein was mainly formed over Nb-containing catalysts, whereas acrylic acid, acrolein and COx were mainly observed over V-containing catalysts. The differences between bulk and supported catalysts have been explained according to changes in their physico-chemical properties: V-containing catalysts presenting both acid and redox sites; and Nb-containing catalysts presenting acid sites. In this way, supported materials seems to be effective in both redox and acid reactions due to the small modifications of the acid characteristics of catalysts.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Hydrothermal synthesis of Mo-V mixed oxides possessing several crystalline
           phases and their performance in the catalytic oxydehydration of glycerol
           to acrylic acid
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Letícia F. Rasteiro, Luiz H. Vieira, Luiz G. Possato, Sandra H. Pulcinelli, Celso V. Santilli, Leandro Martins
      The one-step oxydehydration of glycerol to acrylic acid over molybdenum and vanadium mixed oxides was investigated. The Mo-V oxide catalysts were prepared by a simple hydrothermal method under different synthesis and calcination atmospheres and were characterized by in situ XRD, TPD-NH3, N2 adsorption/desorption, X-ray absorption near vanadium K-edge spectroscopy and thermogravimetry. The catalytic performance of the samples at different temperatures (290, 320 and 350°C) and under different gas flow compositions (20% O2 in N2, 100% O2, or 100% N2) revealed that the arrangement of the crystallographic structures of the active phases directly influenced the catalytic performance. It was found that the catalysts heat-treated in oxidizing atmosphere gave superior catalytic results comparing with the catalysts heat-treated in inert atmosphere due to the equilibrium between the crystalline phases MoVO5 and Mo4.65V0.35O14 that contains V+4 and V+5. Catalytic oxydehydration at 320°C under a flow of 100% O2 gave the best performance, achieving selectivity of 33.5% towards acrylic acid and 100% conversion of glycerol.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Vapor phase hydrogenolysis of glycerol to 1,2-propanediol at atmospheric
           pressure over copper catalysts supported on mesoporous alumina
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): M.L. Dieuzeide, R. de Urtiaga, M. Jobbagy, N. Amadeo
      The present work explores the hydrogenolysis of glycerol to produce 1,2-propanediol in vapor phase at atmospheric pressure over copper catalysts supported on mesoporous alumina. Catalysts were prepared by alumina impregnation varying CuO loading between 3wt% and 30wt%. The textural and structural characteristics of the catalysts were determined by N2 sorptometry (BET), powder X-ray diffraction (PXRD), temperature programmed reduction (TPR) and N2O chemisorption (copper metallic area). The characterization showed that all catalysts present textural properties characteristic of mesoporous solids, such as the adsorption isotherms which are type IV. Based both on characterization and activity results, it was possible to conclude that the yield to 1,2-propanediol presented a non-monotonic dependence on total copper metallic area. In addition, it was proved that 1,2-propanediol production is associated with the presence of highly dispersed CuO phase in the solids. Promising results were obtained with CuO(15)Al catalysts, taking into account that the performance can be improved by increasing residence time.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Bio-propylene glycol by liquid phase hydrogenolysis of glycerol with
           Ni/SiO2-C catalysts
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Martín N. Gatti, Francisco Pompeo, Gerardo F. Santori, Nora N. Nichio
      The development of catalytic materials, hydrothermally stable and selective to the desired products, is still a challenge. The aim of the present work is to prepare a nickel catalyst with a metal loading of 5wt% Ni supported on a SiO2-C composite, to be used in the liquid-phase glycerol hydrogenolysis reaction. The most active and selective catalyst to 1,2-propylene glycol (1,2-PG) was Ni/SC-095, which presented surface acidity fundamentally represented by the presence of carboxylic groups which promoted the CO cleavage reactions of the glycerol primary carbon to produce acetol, and subsequently by hydrogenation to produce 1,2-PG. Concerning the selection of operating conditions, the influence of the most relevant variables of the process were analyzed, i.e., temperature (220–260°C), glycerol concentration (30–65%), and hydrogen partial pressure (0–4MPa). The best result was obtained at 260°C with 30wt% glycerol, 6h on reaction and a hydrogen partial pressure of 2MPa. Under these conditions, selectivities of 77% towards 1,2-PG and 3% to acetol were obtained, with 56% of conversion. It was demonstrated that there are no important structural changes through the characterization of the used samples. Both the SC-095 support and the Ni/SC-095 catalyst maintained their BET surface area. By XRD and TEM, there could be a slight increase in particle size, which would indicate good resistance to sintering against the severe hydrothermal conditions of this reaction.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Pt catalysts supported on ion exchange resins for selective glycerol
           oxidation. Effect of Au incorporation
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Bárbara S. Sánchez, Martín S. Gross, Carlos A. Querini
      In this paper, bimetallic Pt-Au catalysts were studied for the selective liquid phase oxidation of glycerol. The support used was a macroporous weak anion exchange resin. Two different preparation methods were employed: simultaneous exchange of both metals, and a sequential exchange using the controlled surface reaction technique. PtAu catalysts with a total metal content of 0.4wt% were prepared, with different Pt:Au molar ratios: 1:1; 2:1 and 1:2. The monometallic Au catalyst resulted inactive for the reaction. Nevertheless, it was found that the addition of Au improved the monometallic Pt catalyst activity. XPS results suggest the formation of a Pt-Au alloy, which could be related with conversion improvement. Not only the presence of Pt-Au alloyed particles, but also the Pt/Au ratio on the catalyst surface influences the activity. When the Au particles reduced on top of Pt (controlled surface reaction method), the Pt amount exposed at the catalyst surface was considerably reduced. For this reason, this Pt-Au sample did not show a significant improvement of conversion with respect to the monometallic platinum.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Aqueous phase hydrogenation of furfural using carbon-supported Ru and RuSn
           catalysts
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Juan J. Musci, Andrea B. Merlo, Mónica L. Casella
      The aqueous phase hydrogenation (APH) of furfural was studied over carbon-supported monometallic Ru and bimetallic RuSn catalysts at 90°C and 1.25MPa. Tin was added via Surface Organometallic Chemistry on Metals techniques and its effect was a function of the Sn/Ru atomic ratio. Thus, the addition of Sn in a Sn/Ru ratio of 0.4 promoted the CO hydrogenation reaching a selectivity towards furfuryl alcohol over 85% throughout the course of the reaction. A higher concentration of tin does not improve the situation. It seems to be a compromise between the dilution of Ru sites, active for the hydrogenation reaction, and the promoting effect of Sn. TEM, TPR and XPS characterization indicate the strong interaction between Ru and Sn in all the bimetallic catalysts. Finally, the reuse of the catalyst was analyzed.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Degradation of Atrazine over a heterogeneous photo-fenton process with
           iron modified MCM-41 materials
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Tamara B. Benzaquén, Natalia I. Cuello, Orlando M. Alfano, Griselda A. Eimer
      In this work, MCM-41 materials have been synthesized and modified with different metal loadings of iron by the wet impregnation method. The different meso-structures obtained were characterized by XRD, UVVIS-RD, ICP and TEM and their behaviors as heterogeneous catalysts in the photo-Fenton reaction were studied. Thus, iron-containing mesostructured materials have been successfully tested for the heterogeneous photo-Fenton degradation of atrazine aqueous solutions using UV–vis irradiation at room temperature and close to neutral pH. In order to assess the effectiveness of the herbicide degradation in the heterogeneous photo-Fenton process, and to compare experimental results obtained, a study of the photonic efficiency is presented. The photonic efficiency of Atrazine degradation was evaluated considering different experimental conditions employed two factorial designs. The results showed that the iron modified MCM-41 with a nominal metal loading of 2.5wt.% exhibited the highest activity. Consequently, the high performance of this material indicates that the heterogeneous via of the photo-Fenton process can also be efficiently employed for the treatment of simulated wastewater containing atrazine, thus presenting advantages unlike the homogeneous process.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Bio-hydrogen production by APR of C2-C6 polyols on Pt/Al2O3: Dependence of
           H2 productivity on metal content
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): H.A. Duarte, M.E. Sad, C.R. Apesteguía
      The effect of the platinum loading on the production of hydrogen by aqueous-phase reforming of ethylene glycol, glycerol, xylitol and sorbitol was studied on Pt/Al2O3 catalysts containing 0.30, 0.57, 1.50 and 2.77 Pt%. Catalytic runs were performed at a space velocity of 1.2h−1, 498K, 29.3bar and using a polyol(1.0%)/water feed. The total polyol conversion and the polyol conversion to gaseous products increased with surface Pt concentration (Pts, μmol Pt/gcat). Similarly, the yield and the productivity to hydrogen (Pr, molH2/gh) increased continuously with Pts in all the cases, but the Pr values diminished with the polyol chain length. Coke formation depended on Pts and the polyol size; the amount of carbon formed on the catalyst increased indeed with Pts and diminished with the polyol chain length. The metal fraction was severely sintered during the APR reaction, irrespective of the reactant size. Nevertheless, the magnitude of the Pt dispersion drop was not dependent on the amount of platinum on Pt/Al2O3 catalysts.
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      PubDate: 2017-09-26T09:34:37Z
       
  • The role of cobalt in bimetallic iron-cobalt magnetic carbon xerogels
           developed for catalytic wet peroxide oxidation
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Rui S. Ribeiro, Adrián M.T. Silva, José L. Figueiredo, Joaquim L. Faria, Helder T. Gomes
      Three magnetic carbon xerogels were developed by inclusion of iron and/or cobalt precursors during the synthesis procedure. The synthesized materials were tested in the catalytic wet peroxide oxidation (CWPO) of aqueous solutions containing 4-nitrophenol (4-NP) − a refractory organic model pollutant, under a water treatment process intensification approach. For that purpose, the experimental runs were performed with high pollutant load (5gL−1), low catalyst dosage (2.5gL−1, corresponding to a fixed pollutant/catalyst mass ratio of 2), atmospheric pressure, 50°C, pH=3 and stoichiometric amount of hydrogen peroxide (H2O2). The bimetallic magnetic carbon xerogel catalyst (CX/CoFe) was more active than each of the monometallic catalysts (CX/Fe or CX/Co). The better performance was explained in terms of a synergic association of factors: (i) the enhanced accessibility to the active iron species at the surface of CX/CoFe promoted by the simultaneous incorporation of cobalt, (ii) the ability of metallic Co to catalyse H2O2 decomposition via hydroxyl radicals (HO) formation, and (iii) the efficient reduction of Fe3+ to Fe2+ promoted by metallic Co on the surface of CX/CoFe. A 4-NP conversion of 98.5% was determined after 30min of CWPO reaction. Leaching of the iron species in the bimetallic CX/CoFe was considerably reduced with relation to the monometallic iron catalyst. However, partial catalyst deactivation occurred due to lower stability of oxidized cobalt species. A detailed reaction mechanism is proposed for the surface catalytic reactions occurring over the CX/CoFe catalyst.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Stacked wire-mesh monoliths for VOCs combustion: Effect of the
           mesh-opening in the catalytic performance
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Oihane Sanz, Ezequiel D. Banús, Aintzane Goya, Haizea Larumbe, Juan José Delgado, Antonio Monzón, Mario Montes
      Structured reactors based on low cost metallic wire-mesh substrates of highly enhanced transport properties can be an interesting alternative to parallel channel monolithic reactors. In this work stacked wire-mesh monoliths were studied for volatile organic compounds elimination. Monoliths of different mesh-opening were homogeneously and adherently dip-coated with Pt/Manganese Octahedral Molecular Sieve (OMS-2) bifunctional catalyst. The catalytic activity was tested in toluene and methanol complete oxidation reactions. Catalytic activity increases using stacked wire-mesh monoliths instead of parallel channel monoliths and decreases when increasing the wire-mesh opening, showing the importance of the mass-transfer phenomena (contact between the gas phase and the solid catalyst).
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      PubDate: 2017-09-26T09:34:37Z
       
  • Use of pillared clays in the preparation of washcoated clay honeycomb
           monoliths as support of manganese catalysts for the total oxidation of
           VOCs
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): José M. Gatica, Jorge Castiglioni, Carolina de los Santos, M. Pilar Yeste, Gustavo Cifredo, Martín Torres, Hilario Vidal
      Manganese catalysts supported by impregnation onto honeycomb monoliths extruded from commercial clay, previously coated with aluminium-pillared clay, were prepared and tested in the total combustion of propane and acetone. Samples characterization included chemical analysis, nitrogen physisorption, electron microscopies (SEM-EDS, HAADF and EELS), XRD, TPR and O2-TPD experiments. The active phase (around 5wt%), consisting of MnO2 particles as majority phase, with homogeneous size and shape, that tends to concentrate in some regions of the surface of the clay support, exhibited high efficiency to oxidize the two model VOCs investigated and stability in severe reaction conditions. Light-off temperatures as low as 225 and 330°C were found for the oxidation of acetone and propane respectively. The better performance observed in comparison to the monoliths without pillared clay was attributed to the higher active phase loading. Differences found as function of the VOC's nature and concentration were related to the different oxidation mechanisms proposed in literature, either just Mars-van Krevelen or this with also Eley-Rideal contribution, for acetone and propane respectively. These results combined with the intrinsic advantages of the honeycomb monolithic design open up new possibilities for using pillared clays as catalytic support in VOCs oxidation under more affordable conditions.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Steady-state NH3-SCR global model and kinetic parameter estimation for NOx
           removal in diesel engine exhaust aftertreatment with Cu/chabazite
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Unai De-La-Torre, Beñat Pereda-Ayo, Miguel A. Gutiérrez-Ortiz, José A. González-Marcos, Juan R. González-Velasco
      A steady-state global kinetic model for the NOx NH3-SCR reaction system, including NH3 oxidation, NO oxidation, standard SCR reaction, fast SCR reaction, NO2 SCR reaction, and N2O formation and decomposition is proposed, based on the Eley-Rideal formalism in which only ammonia is adsorbed and NO reacts directly from the gas phase. The experimental runs were designed under operational conditions simulating NO, NH3, NO2 feed stream composition near to the real application for NOx removal from diesel engine automobile exhaust aftertreatment. An initial set of 62 experiments, with only NO2 and NH3 in the feed stream allows a preliminary estimation of some kinetic parameters. Additional extensive experimentation up to 176 runs under a wide range of feed stream composition, temperature and space time was carried out. The experimental outlet NO, NH3, NO2 and N2O concentrations are analyzed for kinetic parameter estimation of seven reactions included in the proposed global NOx NH3-SCR system, resulting in activation energy values for standard SCR reaction, fast SCR reaction and NO2 SCR reaction of 91.5, 42.0, and 118kJmol−1, respectively. The proposed model resulted of high statistical significance deduced from the analysis of variance, with a determination coefficient of 0.952, and excellent F-test for a probability superior to 99%.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Catalytic activity and stability of Pd/Co catalysts in simultaneous
           selective catalytic reduction of NOx with methane and oxidation of
           o-dichlorobenzene
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Manuel Cano, Felipe Guarín, Beatriz Aristizábal, Aída-Luz Villa, Lina-María González
      Nitrogen oxides (NOx) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are well known as hazardous pollutants that may be generated during combustion processes, and which simultaneous removal is highly desired. Here the Selective Catalytic Reduction of NO by methane (CH4-SCR) with the simultaneous oxidation of 1,2-dichlorobenzene (o-DCB) was studied over Pd/Co-HMOR and Pd/Co-SZ catalysts under lean, dry and wet conditions. Catalysts were characterized by XRD, BET, TGA, H2-TPR, NH3-TPD, TEM/EDS and Raman spectroscopy. Pd/Co-HMOR showed better catalytic performance than Pd/Co-SZ in terms of activity and durability under both dry and wet conditions at 500°C. The presence of Co2+ ion in both catalysts explains partially the high activity towards o-DCB oxidation. The deactivation of Pd/Co-HMOR for CH4-SCR at reaction temperatures above 500°C may be related with the formation of PdO specie while the loose of sulfate groups of Pd/Co-SZ can be correlated with the deactivation of this catalyst towards CH4-SCR. According to NH3-TPD analysis, both Pd/Co-HMOR and Pd/Co-SZ catalysts present strong acid sites in the temperature range from 300 to 600°C, which can be associated with their considerable active towards both reactions. The higher performance of Pd/Co-HMOR compared with Pd/Co-SZ, mainly in the CH4-SCR reaction, can be related with the higher total acidity of the catalyst supported on HMOR. The XRD analysis of used samples showed that Pd/Co-HMOR losses crystallinity at reaction temperatures greater than 500°C and that monoclinic phase appears in Pd/Co-SZ owing to sulfate group loss.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Reductive amination of levulinic acid to different pyrrolidones on
           Ir/SiO2-SO3H: Elucidation of reaction mechanism
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): José J. Martínez, Leonardo Silva, Hugo A. Rojas, Gustavo P. Romanelli, Lucas A. Santos, Teodorico C. Ramalho, María H. Brijaldo, Fabio B. Passos
      Levulinic acid (LA) transformation to different pyrrolidones via reductive amination was studied using an Ir/SiO2-SO3H catalyst in liquid phase. The effects of solvent, amine concentration, H2 partial pressure, catalyst mass, and reuse were studied. The spent catalysts were evaluated by DRIFTS to obtain evidence of the interaction of levulinic acid with aniline on the catalyst surface. The sulfonic groups on SiO2 improved the yield to pyrrolidones and avoided side reactions. A reaction mechanism is proposed where the reductive amination occurs between LA and amine towards an intermediate amine that is then cycled. The Gibbs free energy for the reaction mechanism was evaluated. Besides, the HOMO and LUMO of the amine reactants and intermediates using density functional theory (DFT) with the B3LYP-D3 method were theoretically determined to understand the rate-limiting and the cyclization steps.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Kinetic and mechanistic study of the synthesis of ionone isomers from
           pseudoionone on Brønsted acid solids
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): V.K. Díez, C.R. Apesteguía, J.I. Di Cosimo
      The kinetics of the liquid-phase synthesis of α-, β- and γ-ionones from pseudoionone was studied on Brønsted acid solids. Four silica-supported tungstophosphoric acid catalysts containing different heteropolyacid loadings, as well as a silica-supported triflic acid sample and a commercial resin (Amberlyst 35W) were tested in a batch reactor at 343–383K under autogenous pressure. The final composition of the ionone isomer mixture depended on the catalyst acidic properties and operational conditions. The reaction pathways leading to the three ionone isomers were elucidated by postulating a heterogeneous Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model. First order rate expressions, participation of a single Brønsted acid site in each reaction step and a cationic cyclic intermediate shared by the three ionone isomers were the main model assumptions. It was found that α-, β- and γ-ionones form directly from pseudoionone by cyclization. However, the final concentration of α- and β-ionones is enhanced in consecutive pathways involving the isomerization of γ-ionone. The relative importance of the isomerization steps and the selective formation of α- or β-ionone depend on the Brønsted acid site strength and reaction temperature.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Ethanol steam reforming on nanostructured catalysts of Ni, Co and CeO2:
           Influence of synthesis method on activity, deactivation and regenerability
           
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): N. Pinton, M.V. Vidal, M. Signoretto, A. Martínez-Arias, V. Cortés Corberán
      The catalytic behavior of nanostructured catalysts based on nickel, cobalt and cerium oxide in ethanol steam reforming (ESR) was studied to investigate the effect of the nature of the metal, their combination and the method of preparation. Mono- and bimetallic catalysts with equal metal content (M:Ce=4:6, M=Ni, Co, or Ni/Co=1) were prepared by two methods, impregnation and coprecipitation within reverse microemulsions, characterized by SBET, XRD, TPO and HRTEM, and tested for ESR at 500°C. The nickel catalyst prepared from microemulsions exhibited the best performance in terms of catalytic activity (close to 100% conversion), stability and hydrogen yield. Al the other catalysts deactivated at different paces due to formation of carbon deposits. The oxidative regeneration treatment of the deactivated catalysts recovered the initial activity of the impregnated catalysts but increased markedly those of catalysts from microemulsions. Thus, the catalytic behavior in ESR of the (Ni, Co)-Ce-O system depends on the preparation method, its composition and the catalyst history.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Steam reforming of acetic acid over MgAl2O4-supported Co and Ni catalysts:
           Effect of the composition of Ni/Co and reactants on reaction pathways
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Stefanie C.M. Mizuno, Adriano H. Braga, Carla E. Hori, João Batista O. Santos, José Maria C. Bueno
      The steam reforming of acetic acid (AcH), a model compound of pyrolysis-oil, was studied over MgAl2O4-supported Co-Ni catalysts with different Co/Ni ratios, prepared by impregnation using the incipient wetness method. The catalysts were characterized by X-ray powder diffraction, temperature programmed reduction, temperature programmed desorption, and thermogravimetry. In the steam reforming reaction of AcH, both Ni and Co catalysts suffered partial oxidation due to contact with the reaction mixture. The ketonization reaction occurred on the MgAl2O4 support and the presence of Co or Ni changed the reaction pathway of species adsorbed on the support, which suppressed the formation of acetone. The cleavage of CC bonds was favored on the Ni surface, resulting in CHx species, which in the presence of H2 were preferentially hydrogenated to CH4 at low temperatures. On the other hand, on the Co surface the CHx species were decomposed to C* and H* as the temperature increased. The addition of Co to Ni catalysts inhibited CH4 formation and carbon accumulation.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Structural and catalytic stability assessment of Ni-La-Sn ternary mixed
           oxides for hydrogen production by steam reforming of ethanol.
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): J. Bussi, M. Musso, A. Quevedo, R. Faccio, M. Romero
      NixLaSn trimetallic catalysts (x=5 and 15% by weight) were prepared by a coprecipitation technique by pH change and then calcined at 700°C, 850°C, 900°C and 950°C. XRD analysis of the fresh and unreduced catalysts showed the formation of crystalline phases corresponding to the pyrochlore structure La2Sn2O7 and NiO following calcination at 850°C, 900°C and 950°C. Ni3Sn and Ni3Sn2 compounds were formed under a pure hydrogen atmosphere and 650°C in the well crystallized catalyst containing the pyrochlore. This catalyst was highly active in the ethanol steam reforming reaction at 650°C, giving yield to gaseous mixtures containing hydrogen, carbon monoxide, carbon dioxide and methane. XRD analysis of the spent catalyst showed the presence of Ni3Sn2, Ni3Sn and the pyrochlore as unique phases after 80 hours of reaction time. After an initial decay, H2 yield kept stable until the end of the test. Carbon formation was observed by TEM, TG and elemental analysis. Lanthanum carbonates were also revealed by Raman spectroscopy. The highly stable biphasic structure containing Ni-Sn intermetallic compounds and the La2Sn2O7 could be the basis of catalysts for the production of H2-rich gaseous mixtures starting from bioethanol.
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      PubDate: 2017-09-26T09:34:37Z
       
  • High purity hydrogen from coupled dry reforming and steam iron process
           with cobalt ferrites as oxygen carrier: Process improvement with the
           addition of NiAl2O4 catalyst
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): J. Lachén, P. Durán, J.A. Peña, J. Herguido
      Cobalt ferrite with additive (alumina) has been proposed as oxygen carrier, to jointly carry out the dry reforming of a synthetic biogas, and the reduction stage of an oxide for producing hydrogen by “steam-iron” process. These reactions, as well as the associated reoxidation stage are performed within the same unit: a fixed bed reactor operating on a cyclic manner (redox) looking for the intensification at once of both, production and purification, of PEMFC quality hydrogen. This procedure is intended to be an alternative to traditional methods for producing hydrogen, which simultaneously consumes renewable raw materials and energy sources like biogas. Since catalytic activity of ferrites decays along cycles, the activity of the solid has been enhanced with the aid of small proportions of nickel aluminate with over-stoichiometric nickel oxide acting as catalyst. The addition of NiO/NiAl2O4 has allowed maintaining the catalytic activity in the reduction steps, increasing the amount of reactive solid in the subsequent oxidation steps, and hence the amount of high purity hydrogen obtained per 100g of solid. In fact, the production of hydrogen for catalytic tests at Treduction =800°C reaches a value around 2.6g H2/100g of ferrite, when the non-catalytic counterpart gives only around 0.5g H2/100g of ferrite.
      Graphical abstract image

      PubDate: 2017-09-26T09:34:37Z
       
  • The impact of support surface area on the SMSI decoration effect and
           catalytic performance for Fischer-Tropsch synthesis of Co-Ru/TiO2-anatase
           catalysts
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Francine Bertella, Patricia Concepción, Agustín Martínez
      A series of Co-Ru/TiO2 catalysts (10wt% Co, 0.5wt% Ru, nominal loadings) were prepared by impregnation of TiO2-anatase supports synthesized with different specific surface areas (Ti-L: 53m2/g, Ti-M: 117m2/g, and Ti-H: 148m2/g) by tuning the conditions of the hydrothermal synthesis and/or the calcination treatments. The most relevant physicochemical properties of supports and catalysts were determined by a set of techniques including ICP-OES, XRD, N2 physisorption, electron microscopy (FESEM, HAADF-STEM, HR-TEM), H2-TPR, H2 chemisorption, and IR-CO. Oxidized precursors were reduced in-reactor under flowing pure H2 at 400°C for 10h and evaluated for Fischer-Tropsch synthesis (FTS) in a fixed bed reactor at 220°C, 2.0MPa, and H2/CO molar ratio of 2. These catalysts exhibited the well-known strong metal-support interaction (SMSI) effect reported for TiO2 materials by which partially reduced TiOx species formed during the catalyst reduction step migrate and decorate the surface of the supported metal phases. The extent to which the SMSI effect occurred was found to increase with the surface area of the TiO2-anatase carrier, as supported by H2 chemisorption, TEM, and IR-CO surface titration experiments. As a consequence, the activity per total mass of cobalt or cobalt-time-yield (CTY) of the Co-Ru/TiO2 catalysts gradually declined with the increase in support surface area: Co-Ru/Ti-L>Co-Ru/Ti-M>Co-Ru/Ti-H. The catalysts, however, displayed similar initial TOFs, implying a negligible influence of the SMSI effect on the initial intrinsic activity of the surface Co0 sites. The high surface area Co-Ru/Ti-H catalyst exhibiting the most pronounced SMSI also presented the lowest C5+ selectivity. This behavior was explained by considering the contribution of two effects: the lower resistance to the intraparticle diffusion of α-olefins when increasing the support surface area, as inferred from the olefin-to-paraffin ratios and the values of the diffusion-related parameter χ, and the reduction in size of the cobalt ensembles on the terraces of Co0 nanoparticles, connected to the extent of SMSI, on which chain growth events are favored.
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      PubDate: 2017-09-26T09:34:37Z
       
  • CO2 reduction over Cu-ZnGaMO (M=Al, Zr) catalysts prepared by a sol-gel
           method: Unique performance for the RWGS reaction
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Xianyun Liu, Pilar Ramírez de la Piscina, Jamil Toyir, Narcis Homs
      Cu-ZnGaMO (M=Al, Zr) catalysts prepared by a surfactant-free sol-gel method were characterized and tested in the reverse water-gas shift (RWGS) reaction. Their catalytic behavior was analyzed under 0.1–3MPa at 250–325°C and using a reactant mixture of CO2/H2 =1/3. The catalytic results are analyzed in the light of the characteristics of the catalysts. The Cu-ZnGaZrO catalysts were highly selective for the RWGS reaction; a major role of surface copper and interface oxygen vacancies is proposed. CO2 conversion and CO selectivity increased on increasing the reaction temperature. CO2 conversion reaches 16.8% with 99.7% selectivity for CO under 0.1MPa at 325°C over the Cu-ZnGaZrO1 catalyst. It is suggested that CO and methanol production proceed via independent reaction pathways.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Mixed NiMo, NiW and NiMoW sulfides obtained from layered double hydroxides
           as catalysts in simultaneous HDA and HDS reactions
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Santiago Arias, Yordy E. Licea, Douglas Soares, Jean Guillaume Eon, Luz Amparo Palacio, Arnaldo C. Faro
      NiMoAl, NiWAl and NiMoWAl hydrotreating catalysts were prepared from NiAl-terephthalate layered double hydroxides (LDHs), by ion exchange of the therephthalate anion by heptamolybdate (Mo7O24 6−) and/or metatungstate (H2W12O40 6−). The Mo- and/or W-containing LDHs were sulfided, either by direct sulfidation (DS route) or after previous calcination (PC route).
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      PubDate: 2017-09-26T09:34:37Z
       
  • Naphthalene hydrogenation over Mg-doped Pt/Al2O3
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): José Escobar, María C. Barrera, V. Santes, José E. Terrazas
      Mg-doped alumina carriers at various alkaline earth contents (0.5–8wt%) were prepared by incipient wetness impregnation of corresponding nitrate on sol-gel Al2O3 support. Pt (1wt%) supported catalysts were obtained by pore-filling deposition from H2PtCl6·6H2O on magnesium-modified carriers. Prepared materials were characterized by N2 physisorption, infrared (IR) and UV–vis spectroscopies and temperature-programmed reduction. Textural properties of alumina substrate were not significantly affected by MgO deposition at any content suggesting well-dispersed magnesia patches. According to CO2 adsorption analyzed by IR, surface basic properties of mixed supports were clearly enhanced with alkaline earth concentration. Reduction temperature of Pt4+ species slightly shifted to lower values by augmenting Mg content in binary supports pointing out to weakening of noble metal-mixed carriers interaction. Reduced (at 623K, under hydrogen flow) noble metal catalysts were tested in liquid-phase naphthalene hydrogenation in tri-phasic slurry batch reactor (T=523K, P=3.92MPa). The reduced Pt catalysts supported over the binary carrier at 2wt% Mg content had the best properties in both naphthalene conversion and consecutive tetralin hydrogenation. Nevertheless, addition of the basic additive at higher loading in the support resulted detrimental on saturating properties of corresponding noble metal-based catalyst. Selectivity to preferred cis-decalin isomer decreased over Pt materials by increasing alkaline-earth concentration in the carrier.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Incorporation of Ni and Mo on delaminated clay by auto-combustion and
           impregnation for obtaining decane hydroconversion catalysts
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Juan Carlos Cortés, Mónica Muñoz, Lorena Macías, Rafael Molina, Sonia Moreno
      A series of solids was synthesized by the incorporation of Ni and Mo active species on delaminated clay with novel acidic properties, by impregnation and auto-combustion. The resulting solids were characterized by X-ray fluorescence, X-ray diffraction (XRD), textural analysis by N2 physisorption, temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and, in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). Decane hydroconversion was used to evaluate the potential of the materials as hydrocracking catalysts for vacuum bottoms. XRD was used to confirm modification of the material and good active phase dispersion. TPR revealed an important decrease in the reduction temperatures with auto-combustion method. Low-temperature reducible species play a key role in the catalytic performance for decane hydroconversion.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Highly active CoMo/Al (10) KIT-6 catalysts for HDS of DBT: Role of
           structure and aluminum heteroatom in the support matrix
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): C. Suresh, L. Pérez-Cabrera, J.N. Díaz de León, T.A. Zepeda, G. Alonso-Núñez, S. Fuentes Moyado
      Herein we report the synthesis of CoMo catalysts for the hydrodesulfurization of dibenzothiophene reaction as a function of morphological effect and heteroatom substitution on KIT-6 supports. The interconnected pores of KIT-6 seem to play a vital role in the active catalyst preparation. The activity and direct desulfurization selectivity trends of the different catalysts resulted as follows: CoMo/Al(10)-KIT-6>CoMo/KIT-6>CoMo/γ-Al2O3. The improved catalytic activity and direct desulfurization selectivity are attributed to: (I) the high surface area and interconnected pores of KIT-6 which allow large quantities of nanosized (<4nm) active CoMoS species and (II) the aluminum deposition on the surface of KIT-6 that creates mild acidity on the support, facilitating the dispersion of these nano-sized CoMoS species. Finally, evidence of the Al incorporation into the silica Matrix is presented.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Support effect and metals interactions for NiRu/Al2O3, TiO2 and ZrO2
           catalysts in the hydrodeoxygenation of phenol
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): O.U. Valdés-Martínez, V.A. Suárez-Toriello, J.A. de los Reyes, B. Pawelec, J.L.G. Fierro
      The bio oil of pyrolysis can be upgraded via hydrodeoxygenation to remove unfavorable characteristics related to high levels of oxygen. Sulfided NiMo and CoMo catalyst have been studied extensively in hydrodeoxygenation. However, significant deactivation may occur, due to the lack of sulfur in the charges or to coke deposition, induced by strong acidic supports. Therefore, development of new catalytic materials with alternative supports and active phases is relevant. In this work, Ni, Ru, and Ni-Ru catalysts were prepared by wet impregnation of Ni(NO3)2·6H2O and Ru(NO)(NO3)3 solutions. Al2O3, TiO2, and ZrO2 were used as supports, evidencing influence on hydrodeoxygenation (HDO) of phenol activity and selectivities. TPR and XPS characterization revealed a promoter effect of ruthenium over Ni reducibility and in some cases, a synergetic effect on catalytic activity in phenol HDO reaction was observed. The metallic ruthenium particles were reduced at low temperatures, and they enhanced reduction of Ni by H2 spillover effect, due to a close contact between metals. Furthermore, TPD-NH3 indicated a possible correlation between catalyst acidity and HDO reaction rate.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Conversion of guaiacol over supported ReOx catalysts: Support and metal
           loading effect
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): K. Leiva, R. Garcia, C. Sepulveda, D. Laurenti, C. Geantet, M. Vrinat, J.L. Garcia-Fierro, N. Escalona
      In the present work, the catalytic activity and selectivity for the conversion of 2-methoxyphenol over ReOx catalysts supported on SiO2, Al2O3 and SiO2-Al2O3 in a batch reactor at 300°C and 5MPa of hydrogen pressure were studied. Additionally, several SiO2-supported ReOx catalysts were synthesized with different metal loadings. These catalysts were characterized by N2 adsorption, X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (TPR), temperature-programmed desorption of ammonia (TPD-NH3), Raman spectroscopy and ultraviolet visible (UV–vis-DR) spectroscopy. ReOx catalyst supported over SiO2 revealed the highest catalytic activity and selectivity towards deoxygenated products. This was attributed to a higher formation of oxygen vacancies (active sites) on SiO2, due to a weaker metal-support interaction. The increase of Re content on SiO2 resulted in an increase of guaiacol conversion, reaching a maximum at about 1.8 atoms of Re per nm2 of support. The decrease of activity over 1.8 atoms of Re per nm2of support was correlated to loss of active site due to the formation of aggregates of ReOx.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Ionothermal preparation of triclinic SAPO-34 and its catalytic performance
           in the MTO process
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Manuel Sánchez-Sánchez, Álvaro A. Romero, Irene Pinilla-Herrero, Enrique Sastre
      This work reports the ionothermal synthesis of SAPO-34 material, which is the per-excellence catalyst in the methanol-to-olefins (MTO) process. The direct addition of Si sources to the aluminophosphate and ionic liquid (1-ethyl-3-methyl imidazolium) mixture gave rise to the undesired AEL-structured materials. Therefore, some other strategies were necessary to apply. In particular, two unexplored strategies have been developed: (i) the addition of further heteroatom ions able to direct CHA materials, V ions being particularly efficient; and (ii) to carry out the synthesis in open systems rather than in autoclaves under autogenous pressure. Interestingly, the combination of both strategies led to V4+-free SAPO-34 samples, so any Brönsted acidity of the samples should be assigned to the incorporated Si atoms. These materials, far from being conventional SAPO-34, have triclinic CHA structure, which provides some structural singularities and have not been tested as catalysts in the MTO reaction yet. Despite their conversion level achieved was lower than that given by conventional SAPO-34, probably because of the scarce optimization of the physicochemical properties of the material, the selectivity towards the different olefins is interestingly different, favoring C4 olefins at the expense of ethylene and propylene.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Intracrystalline mesoporosity over Y zeolites. Processing of VGO and
           resid-VGO mixtures in FCC
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Juan Rafael García, Marisa Falco, Ulises Sedran
      Prototypes of FCC catalysts containing 30%wt. Y zeolite with different intracrystalline mesoporosity generated by alkaline desilication, on an inert silica matrix, were tested in cracking a conventional vacuum gasoil (VGO) feedstock, alone and mixed with an atmospheric tower residue (ATR). The experiments were performed in a fluidized bed CREC Riser Simulator reactor (reaction time: 5–30s, temperature: 550°C, catalyst/feedstock: 4.5). Independently of the catalyst, the conversions of the ATR-VGO mixture were higher than those of the VGO at the same conditions. With both feedstocks, the catalyst including the zeolite with increased intracrystalline mesoporosity and higher acidity showed a higher observed activity than the catalyst with the parent zeolite. In addition, the catalyst with the modified zeolite showed higher selectivity to LCO, which is an intermediate product in FCC and a contributor to the diesel pool, especially with the ATR-VGO mixture. This effect was the consequence of the enhanced diffusion transport of primary product molecules in the zeolite pore system which, in diffusing faster, have fewer chances to be further cracked. The catalyst with higher mesoporosity showed higher coke selectivity, coke being less condensed, due to the higher free volume in the porous system allowing accommodate precursors of coke.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Layered double hydroxides as base catalysts for the synthesis of dimethyl
           carbonate
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Jesús Gandara-Loe, A. Jacobo-Azuara, Joaquín Silvestre-Albero, Antonio Sepúlveda-Escribano, Enrique V. Ramos-Fernández
      In this work, we have prepared two series of layered double hydroxides (LDHs) based on three different divalent cations (Zn2+, Ni2+ and Mg2+), that were ion-exchanged by a trivalent cation (Al3+). The charge was balanced with interlayer anions, either silicate or carbonate. Thus, we have synthetized six different samples and we have studied their physicochemical properties by a wide range of techniques, in order to elucidate their properties. Finally, we have used the prepared materials as catalysts in the transesterification of ethylene carbonate with methanol to produce dimethyl carbonate and ethylene glycol. We have found that materials containing Ni as divalent cation present better catalytic activity due to their basic properties, whereas catalysts containing silicate as interlayer anion yield better selectivity, since they have a lower amount of acid sites.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Hydrogen purification over lanthanum-doped iron oxides by WGSR
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Maria do Carmo Rangel, Peterson Santos Querino, Sarah Maria Santana Borges, Sergio Gustavo Marchetti, José Mansur Assaf, Doris Polett Ruiz Vásquez, Cristiane Barbieri Rodella, Tatiana de Freitas Silva, Alisson Henrique Marques da Silva, Adriana Paula Ramon
      Hydrogen technology has been greatly increased in last decades as a promising solution to protect the environment. When carbon-based feedstocks are used, such as natural gas, biomass and biogas, the water gas shift reaction (WGSR) plays an important step in the production of high pure hydrogen for several purposes. By this reaction, the residual carbon monoxide in the gaseous stream (coming from steam reforming of carbon-based feedstocks) can be converted to carbon dioxide and then removed from the stream, avoiding the poisoning of industrial metallic catalysts as well as of electrocatalysts in fuel cells. Aiming to obtain no toxic catalysts that can replace the commercial chromium-doped hematite catalysts, lanthanum-doped hematite was studied in this work. Iron oxide-based samples with different amounts of lanthanum (La/Fe (molar)=0.02; 0.08 and 0.2) were obtained by sol-gel method and calcined at 600°C. The catalysts were characterized by X-ray diffraction, specific surface area measurements, temperature programmed reduction, Raman spectroscopy, Mössbauer spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. It was found that lanthanum affected the textural and reducing properties of hematite, depending on the amount. Moreover, lanthanum oxide increased the activity of hematite by decreasing the size of hematite crystals and then increasing the number of exposed active sites. In addition, lanthanum favored hematite reduction to produce magnetite (active phase). The activity increased with the amount of lanthanum in solids, the lanthanum-richest sample being the most active catalyst.
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      PubDate: 2017-09-26T09:34:37Z
       
  • Fluorine substitution effect in bis(imino)pyridine cobalt complex in
           propylene oligomerization
    • Abstract: Publication date: 1 November 2017
      Source:Catalysis Today, Volume 296
      Author(s): Anna Paula Rodrigues Ehlert, Eduardo Miraglia Carvalho, Daniel Thiele, Cristiano Favero, Isabel Vicente, Katia Bernardo-Gusmão, Rafael Stieler, Roberto Fernando de Souza, Michèle Oberson de Souza
      Two bis(imino)pyridine cobalt complexes have been synthesized, the dichlorido-(2,6-bis[1-(phenylimine)ethyl]pyridine)cobalt(II) ([Co-NNNPhH]) and the dichlorido-(2,6-bis[1-(2-trifluoromethyl-4-fluorophenylimine)ethyl]pyridine)cobalt(II) ([Co-NNNPhF]) and used as catalyst precursor in association with methylaluminoxane (MAO) as cocatalyst in propylene oligomerization. The presence of a fluorine group in [Co-NNNPhF] have been investigated and compared to those of [Co-NNNPhH] regarding the catalytic properties in propylene oligomerization and the structure of the complexes. The correlation of the catalytic properties of the cobalt complexes and their structures have been evidenced.
      Graphical abstract image

      PubDate: 2017-09-26T09:34:37Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295


      PubDate: 2017-09-02T10:48:03Z
       
  • Contents list
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295


      PubDate: 2017-09-02T10:48:03Z
       
  • Water at Interfaces (WAIT)
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Jaeyoung Lee, Young Dok Kim, Bongjin Simon Mun


      PubDate: 2017-09-02T10:48:03Z
       
  • Influence of humidity on the removal of volatile organic compounds using
           solid surfaces
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Eun Ji Park, Hyun Ook Seo, Young Dok Kim
      In recent years, much attention has been devoted to understand how the humidity affects the volatile organic compound (VOC) removal efficiencies using absorbents, photocatalysts or dark-catalysts and both positive and negative effects of humidity on VOC removal have been reported. We show that sorption capability of VOCs of absorbents with high surface areas can be significantly reduced by the competitive adsorption with water in the air and, by hydrophobically modifying the absorbent surfaces, selective sorption of VOCs to water molecules is achieved. For the TiO2 photocatalysts, humidity was found to have both positive and negative effects on catalytic activity; humidity facilitates the total oxidation of toluene to CO2 allowing the long-term stability of the catalytic activity, on the other hand, reduces the adsorption of VOCs on the catalyst surface. By depositing TiO2 islands on hydrophilic nanodiamond nanoparticles, positive effect of humidity becomes more pronounced. Positive and negative effects of humidity analogous to those on photocatalyst were also observed for the dark-catalysts, NiO nanoparticle decorated mesoporous silica. TiO2 interlayer with a high affinity toward toluene was applied between SiO2 and NiO and, as a result, negative effect of humidity, reduction of toluene adsorption in the presence on water, is suppressed.
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      PubDate: 2017-09-02T10:48:03Z
       
  • A comprehensive review on wettability, desalination, and purification
           using graphene-based materials at water interfaces
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Seongpil An, Bhavana N. Joshi, Jong-Gun Lee, Min Wook Lee, Yong Il Kim, Min-woo Kim, Hong Seok Jo, Sam S. Yoon
      Graphene has several outstanding properties that make it suitable for use in a wide range of electronic devices and applications. Although the use of graphene has led to considerable increases in the performance of such devices, recent global concerns regarding water pollution have necessitated studies on graphene as a green material. The fact that graphene shows unique wetting characteristics and has a carbon-based porous structure suggests it should hold great promise for use in water desalination and purification. Thus, understanding the behavior of water at graphene interfaces is necessary for further enhancements in the desalination and purification processes. Hence, this review focuses on the recent advances made in these research areas, while considering the wettability of graphene, and aims to provide insights into the development of graphene-based water desalination and purification technologies.
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      PubDate: 2017-09-02T10:48:03Z
       
  • Catalytically active highly metallic palladium on carbon support for
           oxidation of HCOO−
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Myounghoon Choun, Kahyun Ham, Dongyoon Shin, Jae Kwang Lee, Jaeyoung Lee
      Catalytically active highly metallic palladium (A-I-Pd/C) catalyst for oxidation of formate (HCOO−) was synthesized via borohydride reduction method assisted by ammonia and iodine ion. The physico-chemical characterizations were conducted to investigate properties of the synthesized catalysts and we confirmed A-I-Pd/C is consisted with palladium hydride. The catalytic activity of the catalysts for oxidation of HCOO− are characterized by electrochemical analysis and A-I-Pd/C catalysts performed the best catalytic activity for oxidation of HCOO− in terms of Tafel slope and onset potential. The enhanced catalytic activity of A-I-Pd/C is explained by enhanced kinetics of oxidation of Hads, which is caused by weaken adsorption strength of Hads on Pd due to electron transfer from H to Pd. The enhanced performance of A-I-Pd/C was also confirmed and compared with the others in a single cell system.
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      PubDate: 2017-09-02T10:48:03Z
       
  • Electrochemical corrosion of a glassy carbon electrode
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Youngmi Yi, Gisela Weinberg, Marina Prenzel, Mark Greiner, Saskia Heumann, Sylvia Becker, Robert Schlögl
      Glassy carbon is widely used in electrochemistry due to its properties of high temperature resistance, hardness, low density and low electrical resistance. The present study focuses on the chemical resistance under electrochemical oxidative conditions, which occur under oxygen-involving reactions like oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrochemical performance of glassy carbon investigated in alkaline, neutral and acidic media reveal the same chemical processes during the OER but showing different degradation mechanism. The electrochemical signature of the corrosion in different media could be directly associated with the formation of oxygen functional groups determined by spectroscopic methods like Raman, infrared (IR) and x-ray photoelectron spectroscopy (XPS). The morphology change of the carbon surface caused by carbon oxidation was investigated by microscopy. A rough surface was obtained in the acidic case, whereas dents were seen in alkaline media. It is assumed that the glassy carbon electrode in acidic media degrades by forming surface oxides by acid catalyzed process leading to ring opening in the graphitic structure and therefore oxidation in the bulk. In alkaline media OH radicals preferentially react with alkyl site chains, leading to oxidation of the edges of carbon layers until they become hydrophilic and dissolve.
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      PubDate: 2017-09-02T10:48:03Z
       
  • Electrochemical immunoassay for amyloid-beta 1–42 peptide in biological
           fluids interfacing with a gold nanoparticle modified carbon surface
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Farhana Sharmin Diba, Suhee Kim, Hye Jin Lee
      An electrochemical immunosensor involving the formation of a surface sandwich complex on a gold nanoparticle (NP) modified screen printed carbon electrode (SPCE) is demonstrated for the femtomolar detection of amyloid-beta 1–42 peptide (Aβ) in both serum and plasma. Both bioreceptors forming the assay are highly selective antibodies for Aβ, namely antiAβ (12F4) and (1E11) which possess different binding sites for the Aβ peptide. In order to improve the sensing performance for complex biological fluidic matrix analysis, different mixed monolayers of thiol modified polyethylene glycol (PEG) and mercaptopropionic acid (MPA) were self-assembled onto the Au NP-SPCE followed by tethering antiAβ (12F4) to MPA using a heterobifunctional cross linker. Surface sandwich complexes of antiAβ (12F4)/Aβ/antiAβ (1E11)-ALP were then formed via sequential adsorption with the latter antiAβ (1E11) conjugated to alkaline phosphatase (ALP) enzyme. The reaction of surface immobilized ALP with the substrate, 4-amino phenyl phosphate (APP), generated voltammetric detection signals that linearly increased as a function of Aβ concentration. Differential pulse voltammetry was applied to establish a lowest detectable concentration of 100 fM of Aβ with a linear response range from 100 fM to 25 pM. Following optimization, the immunoassay platform was applied in diluted human serum and plasma samples to determine the native concentration of Aβ and the results were validated using a commercially available ELISA test.
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      PubDate: 2017-09-02T10:48:03Z
       
  • An electro-Fenton system using magnetite coated metallic foams as cathode
           for dye degradation
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Thi May Do, Ji Young Byun, Sang Hoon Kim
      An electro-Fenton system with a magnetite washcoated metal foam as cathode and graphite as anode was successfully applied for the discoloration of methylene blue in aqueous. The effect of pH, applied voltage, supporting electrolyte, electrode inner space, and catalyst dosages were investigated and optimized. Using this cathode, methylene blue was removed with >99.8% removal rate at 10ppm after 60min and with >95.2% at 50ppm after 120min of reaction. Furthermore, those cathodes could be reused at least three times without performance degradation. Due to high degradation capability, simple recovery and high reusability, magnetite washcoated metal foams could be an effective cathode for electro-Fenton systems for removing dyes in wastewater.
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      PubDate: 2017-09-02T10:48:03Z
       
  • Activity of catalysts consisting of Fe2O3 nanoparticles decorating entire
           internal structure of mesoporous Al2O3 bead for toluene total oxidation
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Il Hee Kim, Eun Ji Park, Chan Heum Park, Sang Wook Han, Hyun Ook Seo, Young Dok Kim
      Fe2O3 nanoparticles with a mean size of ∼1nm were evenly distributed inside the mesoporous Al2O3 with a diameter of ∼1mm using temperature-regulated chemical vapor deposition (TR-CVD), in which Fe(Cp)2 vapor and air were use as metal precursor and oxidizing agent, respectively. For comparison, NiO/Al2O3 was prepared by a similar method using Ni(Cp)2 vapor as Ni precursor, and the resulting structure showed NiO nanoparticles decorating only the shell part of the Al2O3 bead with a shell depth of ∼50μm. After post-annealing of these samples under air at 450–750°C, these structures were used as catalysts for oxidation of toluene in the reaction temperature range of 150–350°C. Fe2O3/Al2O3 showed significantly higher catalytic activity than NiO-based catalysts, which can be attributed to the unique structure of Fe2O3/Al2O3, i.e., very small catalytically active nanoparticles are distributed inside the entire structure of the mesoporous supporting material. 100% conversion of toluene into CO2 with a long-term stability of the catalytic activity was realized at 350°C using Fe2O3/Al2O3 under both dry and humid conditions with a toluene concentration of 10,000ppm in the feed gas. It is worth noting that the unique structure of the Fe2O3/Al2O3 is stable after air-post-annealing at 750°C. Our Fe2O3/Al2O3 catalysts are active for toluene oxidation, and stable upon annealing at high temperature, showing that one can use our Fe2O3/Al2O3 as a component of catalytic converter of harmful volatile organic compounds.
      Graphical abstract image

      PubDate: 2017-09-02T10:48:03Z
       
  • Hybrid cathode catalyst with synergistic effect between carbon composite
           catalyst and Pt for ultra-low Pt loading in PEMFCs
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Won Suk Jung, Branko N. Popov
      Due to the high cost of Pt catalyst, reducing the amount of Pt in electrodes is one of the primary issues in polymer electrolyte membrane fuel cells. In this study, the hybrid cathode catalyst using the electrochemically active carbon composite catalyst and Pt catalyst is developed in order to reduce the amount of Pt and increase the overall catalytic performance. The carbon composite catalyst (CCC) is synthesized by pyrolysis of Fe-Co chelate compound followed by acid leaching. The current density of Pt/CCC is 1.5–6-fold higher than that of Pt/CB when employing ultra-low Pt loading (0.04mgPt cm−2). It is found that the Pt/CCC with the ultra-low Pt loading at tuned operating conditions exhibits a higher fuel cell performance than the Pt/CB and commercial Pt/C with four times higher Pt loading (0.16mgPt cm−2). The extensive activity of Pt/CCC is ascribed to the synergistic effect through (1) the combined activity of catalytic sites present in the CCC support and Pt, (2) the well-distributed nanoparticles and (3) the increased metallic Pt0 concentration which indicated that the pyridinic-N played a role of oxide-cleanser.
      Graphical abstract image

      PubDate: 2017-09-02T10:48:03Z
       
  • New cyclopentadienyl rhodium catalysts for electrochemical hydrogen
           production
    • Abstract: Publication date: 15 October 2017
      Source:Catalysis Today, Volume 295
      Author(s): Jinheung Kim, Eswaran Rajkumar, Soojin Kim, Yu Mi Park, Youngmee Kim, Sung-Jin Kim, Hye Jin Lee
      The electrocatalytic activity of two new molecular rhodium catalysts was investigated in a hydrogen evolution system in the presence of a proton source using glassy carbon electrodes in acetonitrile and water. Rhodium complexes supported by pbi and pbt ligands, i.e., [Cp*Rh(pbt)Cl](PF6) (1) and [Cp*Rh(pbi)Cl] (2) (where Cp* is pentamethylcyclopentadienyl, pbt is 2-(2′-pyridyl)benzothiazole, and pbi is 2-(2′-pyridyl)benzimidazole), were observed to electrocatalytically evolve H2 at potential of −0.90V vs Ag/AgCl in CH3CN and CH3CN/H2O. Cyclic voltammetry of 1 and 2 in the presence of acid revealed redox waves consistent with the Rh(III)/Rh(I) couple. Bulk electrolysis were used to confirm the catalytic nature of the process for complexes 1 and 2, with turnover numbers in excess of 100 and essentially quantitative faradaic yields for H2 production. The potentials at which these Rh complexes catalyzed H2 evolution were close to the thermodynamic potentials for the production of H2 from protons in CH3CN and CH3CN/H2O, with the small overpotential being 50mV for 1 as determined by electrochemistry. The complex 1 with more positive Rh(III/I) redox potentials exhibited higher activity for H2 production.
      Graphical abstract image

      PubDate: 2017-09-02T10:48:03Z
       
 
 
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