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Journal Cover Catalysis Today
  [SJR: 1.378]   [H-I: 142]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2969 journals]
  • Hydroconversion of paraffinic wax over platinum and palladium catalysts
           supported on silica–alumina
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Rodrigo Suárez París, Mario Enrico L’Abbate, Leonarda Francesca Liotta, Vicente Montes, Javier Barrientos, Francesco Regali, Atte Aho, Magali Boutonnet, Sven Järås
      Two bifunctional catalysts consisting of platinum or palladium supported on amorphous silica–alumina were prepared and tested in hydrocracking/hydroisomerization of paraffinic wax. The performance of both noble metals was studied at the following reaction conditions: P =35bar; T =300–330°C; H2/wax=0.1wt/wt; WHSV=1–4h−1. The platinum sample was more active in hydrocracking of C22+ compounds and more selective to middle distillates. On the other hand, the palladium-based catalyst resulted in a higher isomerization degree of the products and lower amounts of methane and ethane. The higher production of light compounds over platinum is attributed to a monofunctional hydrogenolysis mechanism, in addition to the classical bifunctional route. Characterization studies showed that both catalysts had comparable metal and acid site distributions. These observations would indicate that the different catalyst performance is due to the different nature of platinum and palladium as hydrogenation/dehydrogenation function.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Effectiveness of catalyst passivation techniques studied in situ with a
           magnetometer
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Moritz Wolf, Nico Fischer, Michael Claeys
      Using an in house developed in situ magnetometer the passivation in diluted oxygen or pure carbon dioxide of a platinum promoted and silica supported cobalt catalyst was studied. No passivation of cobalt was observed after treatment in CO2, neither at 30°C nor at 150°C. The magnetic cobalt metal phase content remained constant during these treatments and decreased in the subsequent exposure to air. The catalyst exposed to 1% O2 in N2 was stable in air at 30°C. However, no long-term stability was observed. The magnetic measurements during passivation in 1% O2 indicate partial oxidation of the nanoparticles in form of a CoO layer. The degree of reduction decreased from 89% to 51%, which corresponds to a theoretical oxide layer thickness of 1.3nm surrounding the metallic core with a diameter of 9.8nm. Upon re-reduction full recovery of the metal phase was obtained. The re-reduction occurred at significantly lower temperatures than the reduction of the freshly prepared catalyst or the re-reduction of a reduced catalyst after exposure to air without any passivation.
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      PubDate: 2016-08-23T13:27:14Z
       
  • The role of carboxylic acid in cobalt Fischer-Tropsch synthesis catalyst
           deactivation
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): D. Kistamurthy, A.M. Saib, D.J. Moodley, H. Preston, I.M. Ciobîcă, W. Janse van Rensburg, J.W. Niemantsverdriet, C.J. Weststrate
      Oxygenated compounds have previously been detected on spent Co/Al2O3 FTS catalyst and have also been proposed to be precursors for carbon formation. Build-up of polymeric carbon on the catalyst during Fischer-Tropsch synthesis (FTS) can negatively influence activity over an extended reaction time. Adsorbed oxygenates detected on spent Co/γ-Al2O3 FTS catalyst are deduced to be located on the γ-Al2O3 support using attenuated total reflectance infrared spectroscopy (ATR-IR). The formation of a metal-carboxylate compound is not detected (ATR-IR) and deduced to be unlikely since acetic acid decomposes at low temperature on a Co metal surface (single crystal Co(0001) experiments under ultra-high vacuum conditions). Acetic acid undergoes dissociative adsorption on the γ-Al2O3 (110) and (100) surfaces (DFT), forming an acetate species. Acetic acid vapor, contacted with reduced Co/Pt/Al2O3 catalyst at model FTS conditions (i.e. 1bar(a) H2/CO:2/1 at 230°C), results in predominantly atomic carbon deposition on the catalyst. Co-feeding of excess acetic acid during FTS does not enhance Co/Pt/Al2O3 catalyst deactivation nor does it significantly impact methane selectivity. Therefore, carboxylic acids can cause atomic carbon formation on Co/γ-Al2O3 catalyst during FTS and result in strongly adsorbed carboxylates on γ-Al2O3 support, but these factors do not significantly impact catalyst deactivation.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Further insights into the effect of sulfur on the activity and selectivity
           of cobalt-based Fischer–Tropsch catalysts
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): J. Barrientos, V. Montes, M. Boutonnet, S. Järås
      A sulfur poisoning study was performed by ex situ poisoning of a platinum-promoted cobalt/alumina catalyst with different sulfur amounts. The poisoned catalyst samples were tested at relevant Fischer–Tropsch reaction conditions and at the same CO conversion in order to evaluate the effect of sulfur on catalyst activity and product selectivity. It was found that the activity and the selectivity to long-chain hydrocarbons decrease with increasing sulfur content. Moreover, it was found that sulfur has no significant effect on the CO2 selectivity. It was also shown that sulfur significantly enhances olefin hydrogenation. Finally, a deactivation model relating the catalyst activity and the sulfur to cobalt active site ratio was proposed and used to describe the experimental results.
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      PubDate: 2016-08-23T13:27:14Z
       
  • A quantum-chemical DFT study of CO dissociation on Fe-promoted stepped Rh
           surfaces
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Ivo A.W. Filot, Farid Fariduddin, Robin J.P. Broos, Bart Zijlstra, Emiel J.M. Hensen
      The present density functional theory study provides insight into the effect of Fe promotion on the CO dissociation reaction on a stepped Rh surface. On the basis of a density of states analysis we demonstrate that Fe is able to promote the CO dissociation reaction by stabilizing the oxygen atom in the transition state. This effect critically depends on the location of the Fe substitution in the Rh(211) surface and the pathway of the CO dissociation reaction. This work explains the higher activity and selectivity encountered in experimental studies during CO hydrogenation on Rh nanoparticles.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Reflections on the Fischer-Tropsch synthesis: Mechanistic issues from a
           surface science perspective
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): C.J. Weststrate, P. van Helden, J.W. Niemantsverdriet
      The current paper presents a mechanistic view on important steps in the Fischer-Tropsch synthesis on cobalt catalysts, inspired by surface science studies. By revisiting the relation between activity and selectivity that results from the ASF assumption we highlight that knowledge about the number of growing chains as well as their residence time (∼growth rate) is of crucial importance to sketch a physically realistic scenario for FTS. This motivates further investigations into the microscopic scenario for FTS chain growth on fcc cobalt nanoparticles, by looking into the reaction mechanism in relation to surface structure and by determining the activation energies for key elementary steps. Such studies indicate that the modest activity of Co FTS catalysts might very well be attributable to the difficulty to remove chemisorbed oxygen from the metallic surface, rather than to dissociation of CO, which was found to proceed readily at step edge sites. Chain growth is envisaged to take place on the close-packed surfaces, with chain initiation via CH+CH to form acetylene, followed by hydrogenation to form ethylidyne, CCH3, a reaction that is shown to be promoted by co-adsorbed CO. Ethylidyne then couples with CH to form propyne, HCCCH3, etc. We propose that a fairly large number of surface sites is involved in the growth of a single chain. In such a “growth ensemble” multiple active step sites produce CHx monomer species that spill over onto the same close-packed coupling terrace, where one or only a few chains grow at the same time. In such a scenario diffusion of hydrocarbonaceous surface species is an essential step in the overall reaction sequence. We explore which factors need to be taken into account when considering of CxHy species under realistic reaction conditions. In addition, we note that the coupling reaction itself, via CH+CCnH2n+1, is a source of growing chain mobility.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Effects of co-feeding with nitrogen-containing compounds on the
           performance of supported cobalt and iron catalysts in Fischer–Tropsch
           synthesis
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Vitaly V. Ordomsky, Alexandre Carvalho, Benoit Legras, Sébastien Paul, Mirella Virginie, Vitaly L. Sushkevich, Andrei Y. Khodakov
      The performance of supported cobalt and iron catalysts in low and high temperature Fischer–Tropsch synthesis was investigated in the presence of small amounts of ammonia in syngas. Ammonia was co-fed to the reactor either by in-situ hydrolysis of acetonitrile or by addition of aqueous ammonia. The addition of acetonitrile and ammonia resulted in significant irreversible deactivation of alumina supported cobalt catalysts. Lower methane and higher C5+ hydrocarbon selectivities were observed. Iron based catalysts did not show any noticeable deactivation in the presence of acetonitrile or ammonia. Moreover, Fischer–Tropsch reaction rate slightly increased after addition of the nitrogen-containing compounds to silica and alumina supported samples. Lower methane selectivity and higher C2–C4 olefin to paraffin ratio were observed in the presence of ammonia when the catalysts were reduced in hydrogen. Iron catalysts activated in carbon monoxide did not demonstrate any significant effect of ammonia on the selectivity. The catalytic data were explained by irreversible formation of inactive cobalt nitrides in cobalt catalysts and transformation of metallic iron and iron oxides in the presence of acetonitrile and ammonia into iron nitrides and iron carbides active in Fischer–Tropsch synthesis.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Enhanced olefin production in Fischer–Tropsch synthesis using ammonia
           containing synthesis gas feeds
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): A.K. Rausch, L. Schubert, R. Henkel, E. van Steen, M. Claeys, F. Roessner
      The impact of ammonia in Fischer–Tropsch synthesis was studied using iron- and cobalt-based catalysts. Ammonia was co-fed to the synthesis gas feed with ammonia concentrations varying between 0 and 26vol%. During conventional Fischer–Tropsch experiments the formation of paraffins, α-olefins, alcohols and carboxylic acids was observed. Upon ammonia addition, the selectivity to α-olefins could be significantly increased at all levels of ammonia addition. The conversion of CO was only affected slightly for low NH3 contents, but decreased rapidly at high NH3 concentrations in the synthesis gas feed. The formation of oxygenated products was suppressed in the presence of ammonia and the formation of nitrogen-containing compounds such as amines and amides was observed, suggesting a reaction of ammonia with oxygen containing compounds or surface intermediates.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Ruthenium nanoparticles encapsulated inside porous hollow carbon spheres:
           A novel catalyst for Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Tumelo N. Phaahlamohlaka, David O. Kumi, Mbongiseni W. Dlamini, Linda L. Jewell, Neil J. Coville
      Two novel Ru Fischer–Tropsch (FT) catalysts were made that were supported on the inside of two hollow carbon spheres that differed in terms of their shell porosity. Mesoporous Stober spheres were made and Ru deposited on the silica. The Ru/silica spheres were encapsulated with carbon deposited by CVD (toluene) or from resorcinol/formaldehyde. Removal of the silica gave Ru@HCS (dRu =5.5) and Ru@MHCS (3.2nm) that had carbon shells (d =ca. 20nm) with different physicochemical properties as evidenced by the TEM, nitrogen adsorption-desorption, TGA, Raman spectroscopy and XRD measurements. FT studies were performed on the two catalysts (10bar; 190/220/250°C; 2/1 ratio H2/CO). Classical Fischer–Tropsch data was obtained indicating that the catalysts could access the reactants and that FT products could escape from the inside of the spheres (acting as a nanoreactor). Activity data indicated diffusion control of CO/H2 into the nanoreactor and selectivity data indicated an alpha value of 0.74–0.78 (220°C). Typical product selectivity associated with small Ru particles was observed and the methane content increased with reaction temperature. No substantial Ru sintering occurred below 220°C. It is thus seen that the porosity of the two hollow carbon architectures is suitable for the FT polymerization reaction.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Role of water-gas-shift reaction in Fischer–Tropsch synthesis on
           iron catalysts: A review
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Dragomir B. Bukur, Branislav Todic, Nimir Elbashir
      Water-gas-shift (WGS) reaction plays a significant role in industrial application of Fischer–Tropsch synthesis (FTS) for coal-to-liquid (CTL) processes with iron-based catalysts. This reaction provides necessary hydrogen for synthesis gas with low H2/CO molar ratio, and has influence on concentrations of reactants, water and carbon dioxide, which in turn has effect on product distribution, rate of FTS and catalyst deactivation. We provide information on the effect of process conditions (H2/CO feed ratio, reaction temperature and pressure), syngas conversion, and catalyst composition and activation procedure on the WGS activity. H2/CO consumption (or usage) ratio and the exit H2/CO ratio vary with conversion and the extent of WGS reaction. The extent of variation is much greater for H2/CO feed ratios greater than 1.7, than it is for the CO rich syngas (H2/CO=0.5–1). This in turn places limits on maximum practical single pass conversion which can be achieved with different feed compositions and results in different types of operation (low single pass conversion with tail gas recycle, and high once through single pass conversion).
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      PubDate: 2016-08-23T13:27:14Z
       
  • Product distribution of CO2 hydrogenation by K- and Mn-promoted Fe
           catalysts supported on N-functionalized carbon nanotubes
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Praewpilin Kangvansura, Ly May Chew, Worasarit Saengsui, Phatchada Santawaja, Yingyot Poo-arporn, Martin Muhler, Hans Schulz, Attera Worayingyong
      An iron based catalyst supported on an N-functionalized carbon nanotube (NCNT) was promoted with potassium and manganese as follows: Fe/NCNT, K/Fe/NCNT, Mn/Fe/NCNT, and K/Mn/Fe/NCNT for CO2 hydrogenation. Time-resolved reduction X-ray absorption near edge spectroscopy (XANES) showed mixed phases of Fe, FeO, Fe3O4, and Fe2O3 resulting from K/Fe/NCNT, and of FeO and Fe3O4 resulting from Mn/Fe/NCNT. The product distributions and growth probability of n-alkanes during CO2 hydrogenation indicated that the potassium-promoted iron catalysts performed Fischer-Tropsch (FT) synthesis under steady state at 60h. 1-Alkenes desorbed from the FT sites with the potassium-promoted catalysts, (K/Fe/NCNT and K/Mn/Fe/NCNT), with low methane formation. Small amounts of 1-alkene, along with high methanation, were produced from the potassium-unpromoted catalysts, (Fe/NCNT and Mn/Fe/NCNT), indicating high local H2:CO ratios on the catalyst surfaces. K/Fe/NCNT and K/Mn/Fe/NCNT catalysts also produced ethanol. Thus, potassium is a key promoter providing active species of the catalysts for alkene and ethanol formation. Reduced surrounding of the NCNT support, potassium as an electronic promoter together with manganese as a structural promoter made the iron-active phase well suitable for CO2 hydrogenation producing mainly alkenes and ethanol.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Fischer–Tropsch synthesis and water gas shift kinetics for a
           precipitated iron catalyst
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Wenping Ma, Gary Jacobs, Dennis E. Sparks, Jennifer L.S. Klettlinger, Chia H. Yen, Burtron H. Davis
      A large number of kinetic data points (83 sets) was obtained over a wide range of CO conversion (7–90%), pressure (1.3–2.5MPa) and H2/CO ratio (0.67–1.5) with an iron catalyst (100 Fe/5.1 Si/1.25K). The kinetics of the catalyst in the low (XCO <70%) and high conversion (XCO >70%) regions were studied separately. Twenty six Fischer–Tropsch synthesis (FTS) and water gas shift (WGS) kinetic models were tested and discriminated. Water and CO2 inhibition was evaluated. While all thirteen FTS models gave a satisfactory fit, the new FTS models that included CO2 inhibition surpassed the others. Water inhibition of the FTS rate was insignificant over both low and high conversion ranges. For the WGS kinetics of the iron catalyst, a newly constructed empirical model and one from the literature provided the best fits of the WGS rates, while nine mechanistic models and one power law WGS model were unable to satisfactorily fit the WGS kinetic data. Water did not significantly limit the WGS rate and CO2 only inhibited the rate at high CO conversions. The equations obtained for the low and high CO conversion ranges varied greatly. The errors for the models for 85% of the FTS and WGS data points were less than 10%, and the errors of the remaining points fell in the range of 10–15%.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Development of a chemical selective iron Fischer Tropsch catalyst
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Gideon F. Botes, Tracy C. Bromfield, Roelof L.J. Coetzer, Renier Crous, Philip Gibson, Alta C. Ferreira
      In the chemical industry C2–C4 olefins are critical building blocks for high value commodity products. One of the key challenges in Fischer Tropsch Synthesis (FTS) technology development is to manipulate process conditions and/or catalytic systems in order to suppress methane selectivity while still producing mainly C2–C4 products with maximum olefin content. Sasol developed an iron catalyst promoted with sodium and sulphur that yielded a fairly high proportion of C2–C4 products with lower than expected methane selectivity. Due to the unexpected low methane selectivity in combination with high olefin selectivity necessitated the evaluation of other promoters similar to sulphur in combination with alkali promoters (i.e. sodium and potassium) in order to understand whether the combination of sulphur and sodium is unique or whether other alkali and non-metal promoters will yield similar results or even improve the selectivity further. By employing high throughput experimentation, a total of 306 catalysts were synthesised and tested in order to identify whether other possible non-metal FTS promoters could either match or improve the selectivities observed for sodium and sulphur and to also identify potential optimum promoter levels for maximum C2–C4 olefin selectivity and minimum methane formation. The results showed that from the series of catalysts evaluated sulphur and sodium yielded the highest olefin selectivity in combination with low methane selectivity and that a mole ratio of at least 2:1 Na:S is required for optimum C2–C4 selectivity. Apart from the statistical analysis of data and subsequent comparison of catalyst selectivity, the catalysts were also evaluated based on the expected Schulz Flory selectivity correlation. For unique catalyst selectivity a significant shift should be observed. In this paper the results of high throughput experimentation are presented and discussed using the direct relations of C2–C4 selectivity and methane selectivity in order to distinguish unique catalyst systems that are selective towards C2–C4 olefin production.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Fischer Tropsch synthesis using cobalt based carbon catalysts
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Sarwat Iqbal, Thomas E. Davies, David J. Morgan, Khalid Karim, James S. Hayward, Jonathan K. Bartley, Stuart H. Taylor, Graham J. Hutchings
      The catalytic activity of a series of carbon-supported cobalt manganese oxide (CoMnO x ) catalysts was investigated for the Fischer Tropsch synthesis reaction. The catalysts were compared with an unsupported CoMnO x catalyst under the same reaction conditions, and it was shown that the use of an activated carbon support increased both the catalyst activity and the selectivity to C2+ hydrocarbons, whilst lowering the selectivity to CH4 and CO2. Additionally, the effects of varying heat treatment temperatures and increasing the precursor ageing times were also investigated. Increasing the heat treatment temperature of the catalyst precursor between 300 and 500°C led to an increase in activity, as well as an increase in selectivity to C2+ hydrocarbons, but it also increased the selectivity to CO2. At 600°C there was a marked decrease in activity, and the main product was C5+ hydrocarbons. Ageing the initial precipitate led to a decrease in activity and also decreased the selectivity towards hydrocarbons.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Hydrogen spillover in the Fischer–Tropsch synthesis: An analysis of gold
           as a promoter for cobalt–alumina catalysts
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Doreen Nabaho, J.W. (Hans) Niemantsverdriet, Michael Claeys, Eric van Steen
      This study investigated the operation of gold as a potential substitute for the platinum promoter in the Co/Al2O3 Fischer–Tropsch catalyst. Au–Co/Al2O3 was tested in conjunction with a model Hybrid Au–Co sample (comprised of a mechanical mixture of Au/Al2O3 +Co/Al2O3) to investigate hydrogen spillover which has been demonstrated to play a vital role in the reduction promotion mechanism. TPR, TGA and in situ XRD provided evidence to support the improved reducibility of supported cobalt oxide crystallites in Au–Co/Al2O3. However, no improvement in the reducibility of the Hybrid Au–Co catalyst was observed, in contrast to previous studies on noble metal reduction promoters. It was hypothesized that even though gold-to-cobalt spillover occurred during reduction in Au–Co/Al2O3, the great separation between the gold and cobalt crystallites, combined with gold’s much lower affinity for hydrogen activation adversely affected the efficiency of the spillover process in the hybrid sample. Nevertheless, Au–Co/Al2O3 had an improved mass-based activity, and a turnover frequency comparable to a platinum promoted sample, which highlighted the potential of gold as a reduction promoter for Co/Al2O3 catalysts.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Kinetic modeling of transient Fischer–Tropsch experiments over Co/Al2O3
           catalysts with different microstructures
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): E. Rebmann, P. Fongarland, V. Lecocq, F. Diehl, Y. Schuurman
      Processes like Fisher–Tropsch synthesis that yield a very large spectrum of products present challenges for modeling approaches due to the large networks that are involved. The number of species involved in such a network increases exponentially if the model concerns isotopic exchange experiments due to the distribution of the labeled atom into the products. Special tools such as a code for computer to generate a reaction network have been developed to deal with the complexity of Steady-State Isotopic Kinetic Analysis (SSITKA) experiments. This approach makes it easier to model both steady-state and SSITKA experiments based on a microkinetic reaction mechanism. The methodology is applied to 12CO→ 13CO SSITKA experiments for Fisher–Tropsch synthesis over a 13wt.% Co/Al2O3 catalyst oriented towards two different Co phase structures, face-centered cubic and hexagonal close-packed, by different pre-treatments.
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      PubDate: 2016-08-23T13:27:14Z
       
  • On the support in cobalt Fischer–Tropsch synthesis—Emphasis on
           alumina and aluminates
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Erling Rytter, Anders Holmen
      Impact of the support in Fischer–Tropsch synthesis is discussed with emphasis on alumina and aluminates; in particular γ-alumina, α-alumina, Mg-aluminate and Ni-aluminate. Topics covered are the support in industrial type catalysts, pore characteristics, attrition of particles, pore diffusion, loading and heat treatment of aluminates, turn-over-frequency and selectivity to C5+ products. Comparison is made between the supports including γ-alumina with narrow, medium, large and ultra-large pore size. An attempt is made to decouple the effects of cobalt crystallite size, pore size and type of support; all of which are important for the degree of polymerization. Selectivity to C5+ is favored by supports containing large pores, i.e., pores made up of large crystallites of the support material that also are more inert in nature. Cobalt surface coverage of CH x reaction intermediates is coupled directly to product selectivity as well as to catalytic activity. A model is suggested to link changes in composition of the surface pool of intermediates with properties of the support. Strain in cobalt crystallites as they extend over several crystallites of the support is expected to play a decisive role. Finally, the effect of conversion and added water on Fischer–Tropsch synthesis is analyzed. It is shown that all supports exhibit a positive selectivity response to water vapor pressure, but more so for the large pore supports titania, Ni-aluminate and γ-alumina with larger pores. Adsorbed water on cobalt may facilitate CO activation and suppress hydrogen coverage. Activity response of water is similar, although an anomalous reduction in activity upon added water for narrow pore alumina is observed. The reduction in activity is ascribed to oxidation of cobalt, possibly due to condensation of water vapor.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Application of water-tolerant Co/β-SiC catalysts in slurry phase
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): J. Labuschagne, R. Meyer, Z.H. Chonco, J.M. Botha, D.J. Moodley
      High surface area, porous β-SiC has significant potential for use as a catalyst support in Fischer–Tropsch synthesis (FTS) due to its high hydrothermal stability. In recent times there has been a large amount of work done utilizing β-SiC as catalyst support for FTS but these have been applied to fixed bed reactor (FBR) systems. In this study we first review the existing literature for cobalt supported on β-SiC in FTS and secondly outline selected aspects of our in-house study of water tolerant catalysts for application in slurry phase reactors, which present a more hydrothermally demanding environment than FBR’s. Co/β-SiC catalysts have been prepared by slurry impregnation of cobalt nitrate and tested for the first time in slurry phase CSTR reactors at high water partial pressures (ca 10bar). These catalysts appear to have a high water tolerance compared to standard refractory oxide catalysts and upon optimal calcination afford excellent activities and low methane selectivity’s. Further modification of the β-SiC surface by acid washing and extended oxidation or surface modification with TiO2 can lead to significant improvements in catalytic performance over the unmodified supports.
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      PubDate: 2016-08-23T13:27:14Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275




      PubDate: 2016-08-23T13:27:14Z
       
  • Contents list
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275




      PubDate: 2016-08-23T13:27:14Z
       
  • Dedication
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275




      PubDate: 2016-08-23T13:27:14Z
       
  • Preface
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Michael Claeys, Eric van Steen, Hans Niemantsverdriet, Manie Vosloo, Nico Fischer



      PubDate: 2016-08-23T13:27:14Z
       
  • Phase changes studied under in situ conditions—A novel cell
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): N. Fischer, M. Claeys
      We present a newly developed in situ/operando sample presentation device for radiation based characterization techniques. Although originally designed for use on commercial X-ray diffractometers it has also been successfully used in a high energy light source environment. We could show that the device allows monitoring phase and crystallite size changes at elevated temperatures and pressures under various atmospheres, including corroding gases such as steam. In addition and in contrast to most previously described cells the presented device allows for the collection of fully industrially relevant kinetic data from catalytic processes. As an example we show a comparison of the catalytic performance of a cobalt based Fischer-Tropsch catalyst obtained with the developed device which uses a capillary reactor to a performance test conducted in a standard 1/2” stainless steel laboratory scale reactor.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Experimental evaluation of catalyst layers with bimodal pore structure for
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Henning Becker, Robert Güttel, Thomas Turek
      As catalyst pores are typically filled with liquid, long-chained hydrocarbons during low-temperature Fischer–Tropsch synthesis internal mass transport limitations can impede conversion rate and C5+ selectivity. Utilization of transport pores may improve reactant diffusion and thereby reduce these negative effects. In this work preparation, characterization and experimental testing of CoRe/γ-Al2O3 catalyst layers, with and without transport pores, of different thickness is presented. All prepared layers with thicknesses in the range from 50 to 600μm exhibit similar cobalt crystallite sizes of 8.7nm irrespective of the presence of transport pores. Experimental results showed an increase in methane selectivity from 10 to 40% and a drop of C5+ selectivity from 80 to 42% with increasing diffusion length. These negative effects could be retarded by use of transport pores. The highest CO conversion was achieved for layers of about 140μm thickness exhibiting 50–70% higher values than obtained with the thinnest layers (50–60μm). This trend holds also for layers with transport pores but use of additional pores did not result in a significant improvement of conversion and space time yield. Nonetheless, on a catalyst mass basis transport pores lead to a benefit in productivity of 25–50%.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Lab-scale experimental studies of Fischer–Tropsch kinetics in a
           three-phase slurry reactor under transient reaction conditions
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Hilko Eilers, Maria Iglesias González, Georg Schaub
      Fluctuating electricity can be converted into hydrocarbon fuels via hydrogen as intermediate, thus replacing fossil fuels and possibly be attractive as a long-term storage in excess electricity generation situations. In this context, flexible operation of the chemical synthesis reactor may be motivated by the possibility of reducing the size of the hydrogen storage and the investment needed. The present study has the aim to identify general aspects and limitations of flexible Fischer–Tropsch reactor operation considering catalyst behavior and reactor operation in a three-phase system. In this contribution, methodology and first results of lab-scale experiments with a stirred slurry reactor are presented. Results of step-change experiments can be described by a mathematical model of the lab-scale setup, using steady-state kinetics determined in separate experiments. During periodic-change experiments, average rates of CO consumption and CH4 formation are not affected by period length. In contrast, analysis of periodic-change experiments with emphasis on hydrocarbon product distribution indicate that long chain hydrocarbon molar flows cannot follow forced oscillation as fast as methane molar flow.
      Graphical abstract image

      PubDate: 2016-08-23T13:27:14Z
       
  • Interplay of reaction and pore diffusion during cobalt-catalyzed
           Fischer–Tropsch synthesis with CO2-rich syngas
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Ferdinand Pöhlmann, Andreas Jess
      For cobalt-catalyzed Fischer–Tropsch synthesis (FTS), a model was developed to analyze numerically the reaction–diffusion performance in catalyst particles. The model is based on a mesoporous particle and is valid for CO2-free and -rich syngas. The kinetic parameters of all three relevant reactions, CO hydrogenation to C2+ hydrocarbons as well as CH4 and CO2 hydrogenation (mainly) to CH4, were derived at intrinsic conditions (d p =150μm). Thereafter, the effective kinetics considering pore diffusion limitations were derived by using a homemade catalyst in 5mm diameter. From the data measured, a kinetic approach for conversion of CO2 inside the catalyst particle was developed. The experimentally derived Langmuir–Hinshelwood type rate expressions and a variable chain growth parameter α, dependent on temperature and syngas ratio, were implemented into the model. Furthermore, the change of the local reaction rates and selectivities, as a consequence of changing syngas ratio due to diffusion limitation is taken into account. The simulated data of effective kinetics and selectivities are in agreement with the measured data. The simulation predicts that CO2 is only converted in the CO-free core region of large catalyst particles at high temperatures and strong pore diffusion limitations. For CO2 converts mainly to CH4 (selectivity 95%C), a slightly increased overall methane selectivity is expected indicating consumption of CO2. However, this effect was not measurable even with 5mm particles at high temperatures as methanation of CO2 occurs only to a minor extent even at pronounced diffusion limited conditions and is negligible at industrial conditions.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Influence of the spatial arrangement of catalyst components in the
           single-stage conversion of synthesis gas to gasoline
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Enrico Lorenz, Paul Wehling, Maximilian Schlereth, Bettina Kraushaar-Czarnetzki
      Aiming at the synthesis of gasoline in a single reaction stage, the conversion of synthesis gas was studied over several spatial arrangements of the catalyst components required for the synthesis of dimethyl ether and for the subsequent formation of hydrocarbons. At pressures of 40bar and temperatures between 270°C and 350°C, extruded catalyst bodies of Cu/ZnO/γ-alumina and of H-ZSM-5/γ-alumina were employed as well as trifunctional composite extrudates of Cu/ZnO/γ-alumina/H-ZSM-5. Using physical mixtures or trifunctional composite catalyst, carbon monoxide conversions can be achieved far above thermodynamic equilibrium levels because dimethyl ether is continuously withdrawn upon conversion to hydrocarbons. However, light hydrocarbon products are prevailing, and gasoline selectivities are very low. In sequential arrangements of copper- (up-flow) and zeolite-based (down-flow) catalysts, boosting of the CO conversion is not possible, but the product distribution is shifted to higher hydrocarbons. The highest gasoline yields were obtained when the copper and zeolite containing catalyst layers were divided in two different temperature zones operating at 270°C up-flow and at 350°C down-flow.
      Graphical abstract image

      PubDate: 2016-08-23T13:27:14Z
       
  • Industrial viability of homogeneous olefin metathesis: Beneficiation of
           linear alpha olefins with the diphenyl-substituted pyridinyl alcoholato
           ruthenium carbene precatalyst
    • Abstract: Publication date: 15 October 2016
      Source:Catalysis Today, Volume 275
      Author(s): Jean I. du Toit, Percy van der Gryp, Monique M. Loock, Tegene T. Tole, Sanette Marx, Johannes H.L. Jordaan, Hermanus C.M. Vosloo
      The catalytic performance of the diphenyl-substituted pyridinyl alcoholato ruthenium carbene precatalyst of the Grubbs 2-type was optimized for 1-octene metathesis by varying operating parameters, such as reaction temperature (30–100°C) and catalyst load (Ru/1-octene molar ratio between 1:5000 and 1:14000). Secondly, the catalyst was tested with other linear alpha olefins (LAOs). Quantities such as product distribution, selectivity, catalyst lifetime, TON and activity were used in comparing and evaluating the efficiency of the precatalyst. It was found that the precatalyst showed both metathesis and isomerization activity for the reaction with 1-octene that was strongly temperature dependent. The precatalyst also showed significant secondary metathesis activity at the optimal reaction temperature of 80°C. In this study, it was postulated and demonstrated with molecular modelling, that the metathesis reaction with the chelating bidentate precatalyst could accurately be described by a hemilabile dissociative mechanism. The reaction kinetics of the model reaction could be described by a set of three interdependent elementary reaction rate equations. In order to determine if the precatalyst is of broader value in LAO metathesis reactions it was also tested with different alpha olefins (1-hexene, 1-heptene, 1-nonene and 1-decene). The results of the LAO metathesis reactions showed that the precatalyst increased the lifetime to 35 days and thermal stability when compared to Grubbs 1 (1h lifetime) and Grubbs 2 (3h lifetime). The TON, selectivity and activity is comparable to those of the Grubbs 2 precatalyst, whilst an improvement on the Grubbs 1 results was obtained.
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      PubDate: 2016-08-23T13:27:14Z
       
  • Study on compositions and changes of SEI film of Li2MnO3 positive material
           during the cycles
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Meng Cheng, Weiping Tang, Yong Li, Kongjun Zhu
      In this article, we investigated the surface series of Li2MnO3 electrodes and the composition variation of the SEI film. XPS and FT-IR analysis indicated the compositions of a primary SEI film, containing about 20at.% LiF, varied upon cycling including the dissolution of LiF and the accumulation of LixPOyFz and organic species, accompanied by surface corrosion. Whereas organic species showed minor change by the static corrosion. The unstable passive film caused high impedance and could not restrain the electrolyte corrosion in both dynamic and static process.
      Graphical abstract image

      PubDate: 2016-06-12T23:08:33Z
       
  • The delaminating and pillaring of MCM-22 for Fischer–Tropsch
           synthesis over cobalt
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Qing-Qing Hao, Chun-Yan Lei, Yong-Hong Song, Zhao-Tie Liu, Zhong-Wen Liu
      To investigate the effect of structural evolution of layered zeolite on the performance of Co/MCM-22 derived zeolites for Fischer–Tropsch (FT) synthesis, the MCM-22, MCM-36 and delaminated zeolite characterized by different arrangement of MWW nanosheets were prepared through directly calcination, pillaring and delaminating of the layered precursor of the MCM-22 (MCM-22(P)). The results show that the extent of reduction of cobalt was increased over Co-supported pillared and delaminated zeolites, and the activities of the catalysts (i.e., CO conversions) were increased in the order of Co/MCM-22<Co/Al2O3–MCM-36<Co/SiO2–MCM-36<Co/delaminated zeolite. Compared to Co/MCM-22, the selectivity of CH4 over Co-supported pillared and delaminated zeolites was decreased clearly. Moreover, Co-supported SiO2–MCM-36 and Al2O3–MCM-36 can effectively narrow the product distribution of FT synthesis showing clearly increased C4–C12 selectivity. However, the selectivity of C21+ hydrocarbons over Co/delaminated zeolite was significantly increased. The results are well explained based on the structural and acidic properties of the MCM-22 derived zeolites together with the reduction behaviors of the catalysts.
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      PubDate: 2016-06-12T23:08:33Z
       
  • Tuning shape of three dimensional graphene sheets
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Hui Wang, Wei Wei, Yun Hang Hu
      3D graphene has been explored as an important material and catalyst for many applications. However, it is still a challenge to tune the shape of 3D graphene sheets. Herein, it is demonstrated that the shapes of 3D graphene sheets, which were synthesized from the reaction between Li2O and CO, are strongly dependent on the particle size of Li2O. When Li2O particle size was very small (about 400nm), the formed graphene sheets possessed a granulated shape. However, as Li2O particle size increased, the shape of the synthesized graphene sheets changed to flower-structure and then to honeycomb-structure. Furthermore, the shape change of graphene from the granulated to the honeycomb-structured can increase its electro-catalytic efficiency as a counter electrode catalyst for dye-sensitized solar cells (DSSCs).
      Graphical abstract image

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




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




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



      PubDate: 2016-06-12T23:08:33Z
       
  • Photocatalyst of organic pollutants decomposition: TiO2/glass fiber cloth
           composites
    • Abstract: Publication date: 1 October 2016
      Source:Catalysis Today, Volume 274
      Author(s): Peng Sun, Ruiyang Xue, Wang Zhang, Imran Zada, Qinglei Liu, Jiajun Gu, Huilan Su, Zhijian Zhang, Jianzhong Zhang, Di Zhang
      Herein TiO2 coated on glass fiber cloth (TiO2/glass fiber cloth, TGFC) was synthesised by sol-gel method. We demonstrated the property about TGFC of photocatalytic decomposition of organic pollutants under ultraviolet-visible (UV–vis) light and sunlight. Glass fiber cloth (GFC) was chosen as the support of TiO2 in order to improve the practical applications for water purification. TGFC-1–6 were characterized by ERSEM, XRD and XPS. Photocatalytic decomposition of crystal violet (CV) was carried out to investigate the photocatalytic activity of TGFC. The efficiency of TGFC-3 was the best. And its photocatalytic decomposition rate of the second to fifth cycle was higher than the first cycle. The photocatalytic decomposition rate of TGFC-3 was 85% under sunlight from 8:00–14:00. We could design and regulate the shape of TGFC and estimate the area, weight and thickness of TiO2, more easily than glass fibers. TGFC is suitable for photocatalytic decomposition of organic pollutants in the water, especially to be fixed in sewage treatment pool and reused.
      Graphical abstract image

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