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Journal Cover Catalysis Today
  [SJR: 1.348]   [H-I: 164]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [3039 journals]
  • Methanation of carbon dioxide on Ru/Al2O3: Catalytic activity and infrared
           study
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Gabriella Garbarino, Daria Bellotti, Elisabetta Finocchio, Loredana Magistri, Guido Busca
      3% Ru/Al2O3 catalyst is active in converting CO2 into methane at atmospheric pressure. At 673K and above the thermodynamic equilibrium is nearly attained. At 623K CH4 yield is above 85%. CO selectivity increases by decreasing reactants partial pressure apparently more than expected by thermodynamics. The reaction order for CO2 partial pressure is confirmed to be zero, while that related to hydrogen pressure is near 0.38 and activation energy ranges 60–75kJ/mol. Arrhenius plot demonstrates that only at reduced reactant partial pressure (3% CO2) or high contact times, a contribution due to some diffusional limitation is present. IR study shows that the H2—reduced catalyst has high-oxidation state Ru oxide species able to oxidize CO to CO2 at 173–243K, while after oxidation/reduction cycle the alumina surface acido-basic sites are freed and the catalyst surface contains both extended Ru metal particles and dispersed low valence Ru species. IR studies show that the formation of methane, both from CO and CO2, occurs when both surface carbonyl species and surface formate species are observed. Starting from CO2, methane is formed already in the low temperature range, i.e., 523–573K, even when CO is not observed in the gas phase.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Supramolecular chemistry of chiral (1R,2S)-ephedrine confined within the
           AFI framework as a function of the synthesis conditions
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Beatriz Bernardo-Maestro, M. Dolores Roca-Moreno, Fernando López-Arbeloa, Joaquín Pérez-Pariente, Luis Gómez-Hortigüela
      In an attempt to promote chirality in AFI-based materials through spatial distributions of dopants, a systematic variation of the synthesis conditions of Mg-doped aluminophosphate-based microporous materials using chiral (1R,2S)-ephedrine as structure-directing agent has been carried out in order to understand the supramolecular chemistry and packing arrangements of these molecules when confined within the AFI channels. The formation of ephedrine dimers is strongly dependent on the synthesis conditions, especially the ephedrine/H2O ratio (higher concentrations of ephedrine favour the incorporation of dimers), crystallisation temperature (higher temperatures enhance the supramolecular aggregation) and Mg content (lower Mg contents increase the formation of dimers). The latter influence is explained by molecular simulations in terms of an electrostatic repulsion between the ammonium groups of closely-located adjacent dimers when a high density of protonated ephedrine molecules is required in order to compensate for the high Mg incorporation. In this situation, dimers are only incorporated if the system is forced by increasing the concentration of ephedrine in the gel and increasing the temperature. Our results show that a similar number of ephedrine molecules and Mg dopants are incorporated in the AFI unit cell because of charge-balancing purposes, suggesting a strong electrostatic interaction between both species with opposite charge.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Heterogeneous oligomerization of ethylene to liquids on bifunctional
           Ni-based catalysts: The influence of support properties on nickel
           speciation and catalytic performance
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Sara Moussa, Maria A. Arribas, Patricia Concepción, Agustín Martínez
      In this work we present a comparative study of the catalytic performance for the heterogeneous oligomerization of ethylene to liquids of bifunctional catalysts comprising Ni (ca. 5wt%) impregnated on three aluminosilicate supports exhibiting distinct acidic, textural, and structural properties. Specifically, a nanocrystalline Beta zeolite, a mesostructured Al-MCM-41 sample, and a commercial silica-doped alumina (Siralox-30) were employed as supports. The materials were characterized by ICP-OES, XRD, N2-physisorption, FTIR-pyridine, 27Al MAS NMR spectroscopy, electron microscopy (HAADF-STEM, TEM), and low-temperature FTIR-CO. The characterization results revealed significant differences in the nickel speciation depending on the support identity. Thus, while isolated Ni2+ cations in ion exchange positions were the prevailing species on the zeolitic Ni/Beta catalyst, Ni2+ interacting with weakly acidic surface hydroxyl groups (i.e., silanols and aluminols) and under-coordinated Ni2+ on the surface of sub-5nm NiO nanoparticles predominated on Ni/Al-MCM-41 and Ni/Siralox-30 catalysts. In the absence of appreciable deactivation the latter two catalysts displayed significantly higher catalytic activity (related to the Ni sites), thus questioning the general believe that ion exchanged Ni2+ cations are the unique active Ni species in Ni-based catalysts. On the other hand, the higher density and strength of the Brønsted acid sites in Ni/Beta determined a higher selectivity to the targeted liquid (C5+) oligomers and a higher degree of branching (i.e., higher octane-number) of the gasoline-range product in comparison to the amorphous catalysts. The C5+ productivity, however, was maximum for the most active Ni/Al-MCM-41 catalyst, reaching values as high as 12mmol/(Kgcat s).
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      PubDate: 2016-09-27T11:24:06Z
       
  • Carbon microspheres preparation, graphitization and surface
           functionalization for glycerol etherification
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Leone Frusteri, Catia Cannilla, Giuseppe Bonura, Andrey L. Chuvilin, Siglinda Perathoner, Gabriele Centi, Francesco Frusteri
      An easy and cost-effective method to prepare mono-disperse carbon microspheres via a hydrothermal carbonization process (CHT) under moderate conditions (200°C) has been investigated. The preparation was carried out using glucose in aqueous solution. The results clearly revealed that the procedure employed allowed obtaining amorphous microspheres, 200–300nm in size, and spheres of 1–2μm, characterized by a surface area close to 600m2/g. TEM-EELS and XRD analyses demonstrated that the crystallinity grade of carbon micro-spheres significantly increases after N2 treatment at 1000°C for 6h. Moreover, the presence of surface functional groups, revealed by DRIFT analysis, allowed functionalizing the carbon spheres by sample inorganic acid treatment or by inorganic acid treatment followed by impregnation with fluorinated superacid ionomer (Hyflon). These catalytic systems resulted to be very active in glycerol etherification reaction, allowing obtaining, differently from a commercial A15 catalyst, a mixture of tert-butylethers containing a very low amount of side products.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Total oxidation of ethanol over layered double hydroxide-related mixed
           oxide catalysts: Effect of cation composition
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Květa Jirátová, František Kovanda, Jana Ludvíková, Jana Balabánová, Jan Klempa
      Ethanol total oxidation over mixed oxide catalysts containing various transition metal cations was studied. The MII–MIII layered double hydroxide (LDH) precursors with MII/MIII molar ratio of 2 (MII =Cu, Co, Ni, Cu–Ni, Cu–Co, and Co–Ni; MIII =Mn or Al) were prepared by coprecipitation of nitrate solutions. The ternary mixed oxides containing Mn were more active than the binary Cu–Mn, Co–Mn, and Ni–Mn ones as well as the ternary Al-containing catalysts; the Cu–Ni–Mn mixed oxide was the most active. The catalytic activity increased with increasing amount of easily reducible components and amount of oxygen desorbed from catalysts surface at lower temperatures (up to 500°C). Main byproduct of the ethanol oxidation was acetaldehyde. Ethanol oxidation over Al-containing catalysts produced lower amounts of acetaldehyde than that over the catalysts comprising Mn; both the Cu–Ni–Mn and Co–Ni–Mn catalysts showed the lowest temperatures of acetaldehyde disappearance.
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      PubDate: 2016-09-27T11:24:06Z
       
  • The effect of UTL layer connectivity in isoreticular zeolites on the
           catalytic performance in toluene alkylation
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Naděžda Žilková, Pavla Eliášová, Sulaiman Al-Khattaf, Russell E. Morris, Michal Mazur, Jiří Čejka
      Toluene alkylation with isopropyl alcohol was used as a model reaction to investigate the effect of UTL-type layer connectivity in a series of isoreticular zeolites and related zeolitic materials. All prepared catalysts possess the same structure of the layers but their connectivity differs from amorphous pillars (IPC-1PI), double-four-rings (UTL), single-four-rings (IPC-2=OKO, International Zeolite Association code), oxygen bridges (IPC-4=PCR), or their combinations (IPC-6 and IPC-7). X-ray powder diffraction, scanning electron microscopy, and nitrogen adsorption isotherms were employed to characterize structural and textural properties of the studied catalysts. Deuterated acetonitrile was adsorbed on catalysts to determine the concentrations and type of individual acid sites. Toluene alkylation with isopropyl alcohol evidenced that toluene conversion increases with increasing size of zeolite channels. Simultaneously, selectivity in cymenes increased as open structure of these catalysts did not present optimum reaction volume for the bimolecular reaction of cymenes with toluene to n-propylbenzenes.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Catalytic features of CuZnZr–zeolite hybrid systems for the direct
           CO2-to-DME hydrogenation reaction
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): G. Bonura, F. Frusteri, C. Cannilla, G. Drago Ferrante, A. Aloise, E. Catizzone, M. Migliori, G. Giordano
      The direct hydrogenation of CO2 to dimethyl ether (DME) has been studied in a fixed bed reactor, in presence of supported CuZnZr/zeolite hybrid catalysts. To study the effects of zeolite topology on catalyst performance, two different home-made zeolite structures (i.e., FER and MOR) were used as carriers during gel-oxalate coprecipitation of CuZnZr precursors. The hybrid FER-based catalyst showed a very good activity-selectivity pattern at 5.0MPa, also exhibiting an interesting DME productivity (STY, 752gDME/Kgcat/h), with no coke formation under the adopted experimental conditions (T R, 280°C; GHSV, 8800 NL/Kgcat/h). The presence of well dispersed metal-oxide clusters of the precursors on the 2-D zeolite framework of FER was indicated as a key factor to realize a more efficient mass-transferring of MeOH from CuZnZr sites to zeolite surface, favoring so the formation of DME with higher yields than obtained using MOR as support.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Direct incorporation of B, Al, and Ga into medium-pore ITH zeolite:
           Synthesis, acidic, and catalytic properties
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Mariya V. Shamzhy, Cristina Ochoa-Hernández, Valeryia I. Kasneryk, Maksym V. Opanasenko, Michal Mazur
      Direct crystallization of B-, Al- and Ga-substituted medium-pore ITH zeolites was carried out using hexamethonium hydroxide (HMH) and N,N,N′,N′,-tetramethyl-1,6-hexanediamine (TMHDA) as structure-directing agents. The type of organic SDA was found determining the crystal size and the nature of Brønsted acid sites in isomorphously substituted ITH zeolites. The use of HMH resulted in formation of tiny (length of 0.5–3μm) needle-like ITH crystals having bridging Si(OH+)E(−) (E=B, Al, Ga) groups with acidic strength increasing in the following sequence B<Ga<Al. In contrast, ITH zeolites with bulky (length of 40–50μm) crystals prepared using TMHDA possess loosely bond framework and [(SiO)3AlOH]−H+ and (SiO)2BOH groups (absorption band at 3670cm−1) perturbing upon interaction with pyridine. B-, Al- and Ga-ITH possessing tiny crystals showed improved catalytic performance in tetrahydropyranylation of 1-hexanol in comparison with non-acidic heteroelement-free germanosilicate zeolites and isomorphously substituted ITH zeolites with bulky crystals. The yield of target ether is enhanced with increasing strength of acid sites (e.g. B-<Ga-<Al-ITH) or with growth in their concentration.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Methanol-to-olefin reaction on SAPO-35 catalysts synthesized with
           controlled crystal size and using mesoporogen additives
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Irene Pinilla-Herrero, Carlos Márquez-Álvarez, Enrique Sastre
      SAPO-35 molecular sieves have been synthesized using different additives. Monosaccharides were employed in order to decrease the crystal size and classical mesoporogen agents (carbon black and chitosan) were combined with the sugar additives to generate small crystals of SAPO-35 with intracrystalline mesoporosity. This synthesis strategy produces silicoaluminophosphate materials with larger non-microporous surface area, which facilitates the mass transfer within the catalyst. Thus, the use of these synthesis additives allows to retard catalyst deactivation in the methanol-to-olefin process.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Contents list
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1


      PubDate: 2016-09-27T11:24:06Z
       
  • Selected papers from the 6th Czech-Italian-Spanish Conference on Molecular
           Sieves and Catalysis, Amantea, Italy, from June 14th to 17th 2015
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Girolamo Giordano, Leonardo Marchese, Siglinda Perathoner


      PubDate: 2016-09-27T11:24:06Z
       
  • UTL titanosilicate: An extra-large pore epoxidation catalyst with tunable
           textural properties
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Jan Přech, Jiří Čejka
      The UTL titanosilicate was prepared together with related lamellar Ti-IPC-1PISi material and zeolites Ti-IPC-2 (OKO) and Ti-IPC-4 (PCR) via top-down synthesis. The titanium can be incorporated to the UTL framework by conventional hydrothermal synthesis and it does not affect the so-called ADOR chemistry of the UTL material. Silica-titania pillaring concept was successfully applied providing very active Ti-IPC-1PITi catalyst for bulky molecules epoxidation with hydrogen peroxide. The textural properties of catalysts prepared can be tuned widely keeping the same crystalline titanosilicate active phase. All the materials were characterised by XRD, nitrogen sorption measurement, SEM, and DR-UV/vis spectroscopy. Ti-IPC-1PITi was the most active catalyst in cyclooctene, norbornene, and linalool epoxidation due to the lowest diffusion constraints and sufficient titanium content. Ti-UTL showed activity similar to Ti-BEA in epoxidation of cyclooctene and it provided different products than other titanosilicates in oxidation of linalool with hydrogen peroxide.
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      PubDate: 2016-09-27T11:24:06Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1


      PubDate: 2016-09-27T11:24:06Z
       
  • Nanosized inorganic metal oxides as heterogeneous catalysts for the
           degradation of chemical warfare agents
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Chiara Bisio, Fabio Carniato, Chiara Palumbo, Sergey L. Safronyuk, Mykola F. Starodub, Andrew M. Katsev, Leonardo Marchese, Matteo Guidotti
      Nanosized inorganic metal oxides, such as TiO2, ZnO, γ-Al2O3, are proposed as heterogeneous catalysts for the oxidative degradation of chemical warfare agents (CWA), particularly of organosulfur toxic agents, into oxidised products with reduced toxicity. The morphology, structural and textural properties of the catalysts were investigated. Furthermore, their catalytic properties were evaluated in the oxidative abatement of (2-chloroethyl)ethylsulfide, CEES, a simulant of sulfur mustard (blistering CWA). Their performance was also compared to a conventional decontamination powder and a commercial Nb2O5 sample. The metal oxides powders were then employed in the active oxidative decontamination of CEES from a cotton textile substrate, mimicking a real contamination occurrence. Remarkable results in terms of abatement and degradation into desired products were recorded, achieving good conversions and decontamination efficiency with Nb2O5, TiO2 and γ-Al2O3, under very mild conditions, with hydrogen peroxide (as aqueous solution or as urea-hydrogen peroxide adduct), at room temperature and ambient pressure. In the aim of a real on-field use, the potential environmental impact of these solids was also evaluated by bioluminescence toxicity tests on reference bacteria (Photobacterium leiognathi Sh1), showing a negligible negative impact for TiO2, γ-Al2O3, and Nb2O5. A major biotoxic effect was only found for ZnO.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Experimental investigations of hydrogen production from CO catalytic
           conversion of tar rich syngas by biomass gasification
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Simeone Chianese, Silvester Fail, Matthias Binder, Reinhard Rauch, Hermann Hofbauer, Antonio Molino, Alessandro Blasi, Dino Musmarra
      In this paper, the activity of a cobalt/molybdenum (Co/Mo) commercial catalyst for the Water Gas Shift Reaction for hydrogen production was investigated in a three fixed-bed reactor pilot plant using a tar-rich synthesis gas from a full-scale biomass gasification plant as feed-stream. A parametric variation study was carried out to assess CO conversion (XCO) and selectivity for the water gas shift reaction as a function of the operating temperature (T) in the range 300–450°C. The effects of four dry gas hourly space velocities (GHSV), Case A-Case D, two steam to dry synthesis gas ratios (H2O/SG), 56% v/v and 67% v/v, and a H2S concentration in the range 100–220ppmv,db were investigated: the highest CO conversion (∼95%) was observed in the base case (Case A GHSV) at 67% v/v H2O/SG, and 450°C, the lower the operating temperature the lower the CO concentration, the lower the gas hourly space velocity the higher the CO conversion and the higher the H2O/SG the higher the CO conversion. The effect of H2S variation on CO conversion was also studied, keeping the operating temperature constant (≈365°C) and using the Case D GHSV: CO conversion increased as the H2S concentration increased and XCO ≈40%. Selectivity was not influenced by the parameters investigated. Finally, the effect of the catalyst on tar removal was studied and a CO conversion close to 85% was found.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Lamellar and pillared ZSM-5 zeolites modified with MgO and ZnO for
           catalytic fast-pyrolysis of eucalyptus woodchips
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Javier Fermoso, Héctor Hernando, Prabhas Jana, Inés Moreno, Jan Přech, Cristina Ochoa-Hernández, Patricia Pizarro, Juan M. Coronado, Jiří Čejka, David P. Serrano
      Lamellar and pillared ZSM-5 materials modified with Mg and Zn oxides were synthesized and tested for in-situ catalytic upgrading of eucalyptus woodchips fast-pyrolysis vapors. The introduction of silica pillars into the lamellar ZSM-5 support led to a higher BET area, but also reduced the overall catalyst acidity. The incorporation of MgO and ZnO occurred with a high dispersion over the zeolitic supports, causing also a significant reduction in the value of their textural properties due to a partial blockage of the zeolite pores. Likewise, the acid features of the zeolitic supports underwent sharp changes by the addition of both MgO and ZnO with a strong decrease in the concentration of the Brønsted and Lewis acid sites present in the parent zeolite, as detected by pyridine adsorption followed FTIR spectroscopy. However, additional Lewis acid sites were created associated to the metal oxides deposited onto the zeolitic supports. Pyrolysis tests were accomplished using a lab-scale downdraft fixed-bed reactor working at atmospheric pressure and a temperature of 500°C. The use of zeolitic catalysts increased the gas yield, mostly due to the formation of CO and CO2, to the detriment of bio-oil production. However, the so obtained bio-oils presented higher quality in terms of H/C and O/C ratios, and larger heating values. The incorporation of MgO and ZnO allowed tailoring the zeolite activity to avoid an excessive cracking of the bio-oil, which in turn resulted in a higher yield of the organic compounds present in the bio-oil, and decreasing the formation of undesired polyaromatic hydrocarbons and coke.
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      PubDate: 2016-09-27T11:24:06Z
       
  • CO2 hydrogenation to hydrocarbons over Co and Fe-based Fischer-Tropsch
           catalysts
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Carlo Giorgio Visconti, Michela Martinelli, Leonardo Falbo, Laura Fratalocchi, Luca Lietti
      The performances of representative Co-based and Fe-based Fischer-Tropsch catalysts have been comparatively investigated in the hydrogenation of CO and CO2. Over an un-promoted Co/γ-Al2O3 catalyst, CO2 is easily hydrogenated and its conversion rate is even faster than that of CO; however, the selectivities of the two processes are extremely different, with methane largely dominating the product distribution in the case of CO2 hydrogenation and long-chain hydrocarbons dominating the products pool during CO hydrogenation. As opposite to cobalt, CO2 hydrogenation rate over K-promoted 100Fe/10Zn/1Cu (at/at) catalysts is slower than that of CO, but the products are dominated by middle distillates when CO2 replaces CO in the feed. Such behaviors depend on the different adsorption strengths of CO and CO2, which affect the H/C atomic ratio on the catalyst surface. In the case of Fe-based catalyst, we have also found that the catalytic sites active in the chain growth process (iron carbides) are transformed into sites active in the hydrogenation reactions (iron oxides/reduced iron centers) at low CO partial pressures. Potassium has a key role in promoting the stability of chain growth sites, thus decreasing the secondary reactions of olefins.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Hydrogen production by methane decomposition over pure silica SBA-15
           materials
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Gema Gómez, Juan Ángel Botas, David P. Serrano, Patricia Pizarro
      The effect of the synthesis procedure of SBA-15 on its catalytic behavior in methane decomposition (DeCH4) for hydrogen production has been investigated. Three different SBA-15 materials have been synthesized: SBA-15 (C), by a conventional method with a final calcination step; SBA-15 (MW), replacing the calcination by microwave digestion; and SBA-15 (ULP), using a micelle expander to generate ultra-large pores. All SBA-15 samples exhibit a reaction induction time necessary for the formation of Si–C linkages associated with the creation of active sites. After a sharp decay of the reaction rate due to the appearance of mass transfer limitations, all the SBA-15 materials reach a quasi-stationary state which is maintained during the rest of the reaction time tested (24h). The long-term activity is mainly due to fact that the carbon deposits grow towards the outer part of the SBA-15 particles, keeping part of the active sites accessible to methane molecules. Among the materials tested, SBA-15 (C) exhibits the highest long-term activity and resistance to deactivation, mainly due to its higher thermal stability. Finally, the activation energy (217.8±0.5kJmol−1) and reaction order (0.5) corresponding to SBA-15 (C) indicate that DeCH4 proceeds with crystallite growth as controlling process and a dissociative reaction mechanism.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Pd-Nb binfunctional catalysts supported on silica and zirconium phosphate
           heterostructures for O-removal of dibenzofurane
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): A. Infantes-Molina, E. Moretti, E. Segovia, A. Lenarda, E. Rodríguez-Castellón
      Bifunctional PdNb catalysts were studied in the hydrodesoxygenation (HDO) reaction of dibenzofuran (DBF) at 275°C and 15bar of H2 pressure. The influence of both the support employed (silica and zirconium phosphate heterostructure (PPH)) and the catalyst preparation procedure were evaluated in the catalytic response in the HDO reaction. The catalysts were prepared by incipient wetness impregnation by using two synthetic routes. The catalysts were characterized by means of X-ray diffraction (XRD), N2 adsorption-desorption, thermoprogrammed desorption of NH3 (TPD-NH3), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and elemental analysis. The results show that silica supported catalysts are much more active than those supported on PPH. While the characterization results point to a higher dispersion of the supported catalysts on PPH and better textural and acidic properties, the PdCl2 precursor salt remains on these catalysts even after calcination and catalytic tests, explaining the lower catalytic performance presented by these systems: fewer active centers and more residues of carbon. With respect to the preparation method, regardless the support employed, the catalysts synthesized by incorporating Pd after Nb incorporation and calcination, are more active, most probably due to a better phase dispersion and therefore to a higher amount of active centers.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Mesoporous niobiosilicate NbMCF modified with alkali metals in the
           synthesis of chromene derivatives
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Agata Smuszkiewicz, Jesús Lopez-Sanz, Izabela Sobczak, Maria Ziolek, Rosa M. Martín-Aranda, Elena Soriano, Elena Pérez-Mayoral
      We report the synthesis, characterization and activity of new series of catalysts based on Niobium Mesoporous Cellular Foams (NbMCF), modified with alkaline metal elements. These materials exhibit very different acid-base properties attributed to the Nb source for the preparation of the catalysts and the presence and loading of different alkaline metals. The Me/NbMCF materials (where Me are alkaline metals) were tested in the reaction of 2-hydroxybenzaldehyde and ethyl cyanoacetate, under solvent-free conditions, at room temperature, leading to mixtures of the corresponding chromenes 4 and 5, as mixtures of diastereomers erythro/threo, in a 2:1 ratio, respectively, with good to excellent yields. Our experimental results indicate that the metal loading on the catalysts and the acid-base character, and the texture parameters are probably determining factors in the reactivity and the observed diastereoselectivity. The computational study suggests that the presence of alkaline oxides on Me/NbMCF catalyst, exhibiting strong basicity, activates the formation of the nucleophile species, the corresponding enolate, and initiates the reaction. However, the cation size has a deep impact on the stability of the reactant complex so that the effective aldolization could be obstructed by the presence of the bulkier centers.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Sulphur poisoning of alumina supported Rh catalyst during dry reforming of
           methane
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): G. Mancino, S. Cimino, L. Lisi
      The impact of sulphur poisoning during dry reforming (DR) of methane on a Rh/γ-Al2O3 catalyst was studied by adding up to 30ppmv of SO2 or H2S to the feed (CH4/CO2/N2 =1/1/2) at reaction temperatures in the range 800–900°C. As low as 1ppmv of sulphur in the feed adversely affected the H2 and CO yield, and S-poisoning reached a saturation level for contents ≥10ppmv, independently from the type of S-bearing compound. The impact of S addition on the RWGS reaction, occurring simultaneously to DR, was also investigated under steady state operation. Transient poisoning experiments showed a rapid drop of syn-gas production and a corresponding increase in the temperature level, suggesting that sulphur directly bonded to Rh active sites. An increase of coke formation on the catalyst was detected with respect to S-free conditions, and this effect was studied by Raman spectroscopy and thermogravimetric analysis. Sulphur inhibition was reversible and the Rh-catalyst slowly recovered its initial activity after the removal of sulphur from the feed.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Kinetics and dynamic behaviour of toluene desorption from ZSM-5 using in
           situ high-temperature synchrotron powder X-ray diffraction and
           chromatographic techniques
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): E. Rodeghero, A. Martucci, G. Cruciani, R. Bagatin, E. Sarti, V. Bosi, L. Pasti
      In situ high-temperature (HT) synchrotron X-ray powder diffraction (XRPD), was used in this study as a tool to understand the adsorption/desorption process features of toluene adsorbed in organophilic ZSM-5 zeolite (SiO2/Al2O3 ∼280), as well as framework structural modifications upon thermal treatment from room temperature to 600°C. Rietveld refinements showed that toluene release starts in the 75°C< T <200°C temperature range. Furthermore, extraframework structural changes take place when toluene removal starts. Significant internal pressure is developed with the composition product diffusion causing a corresponding transient expansion in the 10-ring channels. Our results clearly demonstrated that ZSM-5 regeneration is effective when it is thermally treated at about 400°C. Above this temperature, when all the organic have been ejected, non-equilibrium distortions in the framework are relaxed and channel apertures become more circular. ZSM-5 shows no significant difference in saturation capacity once regenerated after toluene reloading, thus demonstrating that thermal regeneration under mild conditions appears to be both very effective even after several cycles of adsorption/desorption.
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      PubDate: 2016-09-27T11:24:06Z
       
  • The interaction of Pd clusters with the bulk and layered two-dimensional
           Silicalite-1 supports
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Ángel Morales-García, Miroslav Rubeš, Petr Nachtigall
      The interaction of Pd atoms and Pd n (n =4 and 6) clusters with the regular three-dimensional (3D) and layered 2D Silicalite-1 was investigated computationally. The interaction of Pd clusters with Silicalite-1 is driven by dispersion interactions, and has only a small electrostatic contribution, therefore, Pd clusters are preferably located inside the channel system of bulk Silicalite-1. The Pd6 cluster fits inside the main channel, where the density of framework atoms around the metal cluster is larger. The interaction of a single Pd atom with Silicalite-1 is stronger with dominant contributions coming from induction and electrostatic effects; isolated Pd atoms preferably bind in the vicinity of surface silanol on the external surface. These conclusions are based on the calculations employing the periodic models of Silicalite-1 and DFT/CC correction scheme that accounts for the dispersion interactions. The DFT/CC approach provides a reliable description of the system based on CCSD(T) calculations for cluster models. The comparison of different exchange-correlation functionals with and without dispersion correction is also shown. It can be concluded that commonly employed functionals underestimate the interaction between Pd–silica and adding the dispersion correction either empirical or non-local causes significant overestimation of the Pd–silica interaction energy.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Nanosized TiO2—A promising catalyst for the aldol condensation of
           furfural with acetone in biomass upgrading
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Dong Nguyen Thanh, Oleg Kikhtyanin, Ruben Ramos, Maadhav Kothari, Pavel Ulbrich, Tasnim Munshi, David Kubička
      Nanosized TiO2 catalyst was successfully prepared by a simple green procedure and used in liquid phase aldol condensation of furfural with acetone, a key step in bio-fuel processing. In order to determine the effect of calcination temperature on catalytic properties of TiO2, the as-prepared TiO2 and calcined TiO2 (150–900°C) were studied by XRD, BET, TPD-CO2/NH3, TGA/DTG and FTIR evaluation. The catalytic performance of TiO2 samples in aldol condensation of furfural with acetone was evaluated and compared with that of Mg–Al hydrotalcites and a BEA zeolite. These experiments showed that uncalcined TiO2 possessed reasonable activity in aldol condensation of furfural to acetone and resulted in commonly produced condensation products. The observed catalytic behavior of TiO2 could be competitive with that reported for other inorganic solids. The calcination of TiO2 resulted, however, in a decrease in its catalytic activity due to extensive dehydration and surface dehydroxylation as well as due to changes of textural properties resulting in a decrease in the amount of accessible active sites. Thanks to its advanced properties, nanosized TiO2 is a promising catalyst for aldol condensation of furfural with acetone and could broaden possibilities for optimizing conditions for bio-fuel production.
      Graphical abstract image

      PubDate: 2016-09-27T11:24:06Z
       
  • Reactivity of bare and Fe-doped alumino-silicate nanotubes (imogolite)
           with H2O2 and the azo-dye Acid Orange 7
    • Abstract: Publication date: 15 November 2016
      Source:Catalysis Today, Volume 277, Part 1
      Author(s): Ehsan Shafia, Serena Esposito, Marco Armandi, Elnaz Bahadori, Edoardo Garrone, Barbara Bonelli
      The adsorption and catalytic properties are reported of aluminosilicate nanotubes (NTs) of the imogolite-type both bare (IMO, (OH)3Al2O3SiOH) and Fe-doped. Iron-doped NTs were obtained by either direct synthesis (Fe-x-IMO) or post synthesis loading (Fe-L-IMO), with 0.70wt.% Fe (Fe-0.70-IMO) and 1.4wt.% Fe content (both Fe-1.4-IMO and Fe-L-IMO). The samples were characterized by X-ray diffraction (XRD); N2 sorption isotherms at −196°C; diffuse reflectance (DR) UV–vis spectroscopy; IR spectroscopy, and electrophoretic mobility in water (ζ-potential). In water, the intrinsic acidity of Fe(OH)Al groups, formed by isomorphic substitution (IS) of Fe3+ for Al3+, is only marginally different from that of parent Al(OH)Al groups, as shown by ζ-potential measurements. Substitution of one octahedral Al3+ site, however, gives rise to the formation of three Fe–O–Al groups and three Fe(OH)Al groups: such process modifies the adsorption and catalytic properties of NTs outer surface, as shown by adsorption of the azo-dye Acid Orange 7 (NaAO7) from water solutions and by AO7− catalytic degradation by H2O2. Interaction with AO7− anions in water occurs in different ways: (i) with bare IMO, AO7− anions preferentially adsorb by electrostatic interaction with the positively charged surface, and by H-bonding; (ii) with Fe-1.4-IMO, IS Fe3+ cations act as coordination centres for N atoms in the AO7− moiety, through a ligand displacement mechanism; (iii) with Fe-L-IMO, AO7− adsorption is hindered by the presence of Fe2O3 clusters. Concerning AO7− degradation by H2O2, the outer surface of proper IMO is much more reactive than Fe-doped IMO towards hydrogen peroxide, by forming very reactive Al-OOH bridges. IS Fe3+ species are probably not accessible to H2O2, and (the expected) Fenton reaction between Fe3+ and H2O2 is not observed.
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      PubDate: 2016-09-27T11:24:06Z
       
  • Structure and property of PFSA/PES porous catalytic nanofibers
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Xiao-Hua Ma, Si-Wen Gu, Zhen-Liang Xu
      Perfluorinated sulfonic acid (PFSA)/polyether sulfone (PES) porous catalytic nanofiber was fabricated and applied to esterification reaction as catalyst in this work. To this aim, PES porous nanofibers were firstly prepared through electrospinning, and PFSA resin as catalyst was successfully anchored on these PES porous nanofibers through dip-coating method. Mesoporous structure was observed in PES porous nanofibers with high specific surface area of 40.6m2/g. The catalytic properties of PFSA/PES porous catalytic nanofibers were measured by esterification of ethanol and acetic acid as model reaction. The recovery of PFSA/PES porous catalytic nanofibers remained 93.8% after three cycles of esterification, and the ion exchange capacity almost remained at a constant level, showing excellent recovery. For PFSA/PES porous catalytic nanofibers loaded with 5wt% of PFSA as catalyst, the conversion rate and forward reaction kinetics constant achieved 85.8% at 1h and 9.03×10−4 m3 kmol−1 s−1 g−1, respectively.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Electrocatalytic dehydrogenation of 2-propanol in electrochemical hydrogen
           pump reactor
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Shiqi Huang, Xuemei Wu, Wei Chen, Lin Ma, Shishui Liu, Gaohong He
      There are few concerns on the hydrogen source except pure hydrogen and water for anode of electrochemical hydrogen pump (EHP) reactor. In this paper, the possibility of 2-propanol as the substitute of conventional hydrogen source was investigated. Dehydrogenation reaction conditions of 2-propanol were optimized, high performance of dehydrogenation could be obtained under 60°C with 1.0–2.0molL−1 2-propanol. Within 1.2V, the available current density of 2-propanol reaches 37.7mAcm−2, which could be equivalent to hundreds of bars hydrogen partial pressure in conventional three-phase hydrogenation reactor. When coupled with phenol hydrogenation in one EHP reactor, results indicate 2-propanol could be successfully performed as anode feed, and performance of phenol is almost as excellent as that in the phenol EHP reactors with hydrogen.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Microwave-assisted hydrogen releasing from liquid organic hydride over
           Pt/CNT catalyst: Effects of oxidation treatment of CNTs
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Liujie Shi, Xing Li, Yongxiao Tuo, Hao Jiang, Xuezhi Duan, Ping Li
      Three oxidation treatment methods have been adopted to bring oxygen functional groups into the structure of carbon nanotubes (CNTs). The structure and morphology of original and oxidized CNTs have been characterized using Raman, FTIR, XPS, TG, N2 cryonic adsorption and TEM techniques. The thermal behaviour of various CNTs-containing suspensions in decalin has been measured under microwave irradiation, and correlated with their electrical conductivity. The results show that the oxidation treatments not only introduce the oxygenated groups but also partially damage or even break the graphene layer structure of CNTs. The electrical conductivity of CNTs decreases consequently rendering the thermal behaviour of the oxidized CNTs inferior. The catalytic performance of Pt catalysts supported on the original and the oxidized CNTs has been evaluated in the reaction of hydrogen releasing from decalin under microwave irradiation and compared with that presented using conventional heating. The Pt catalysts supported on the oxidized CNTs performs worse than the Pt/CNT-Original catalyst in terms of average reaction rate and selectivity by taking whatever heating methods. The depressed catalytic activity can be ascribed to the limitation of hydrogen diffusion due to the entrapment of a majority of Pt particles inside the hollow tubes of the oxidized CNTs. The strong coupling effect of CNT suspensions with microwave can induce higher reaction temperatures, which can explain the superior catalytic performance under microwave irradiation than using conventional heating.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Comparison study for the oxidative dehydrogenation of isopentenes to
           isoprene in fixed and fluidized beds
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Qi Wang, Chenxi Zhang, Zhenxing Zhu, Muhammad Tahir Arslan, Ling Yang, Fei Wei
      The oxidative dehydrogenation (ODH) of hydrocarbons is an important route to obtain olefins and diolefins. Fluidized bed is good choice for the highly exothermic ODH of isopentenes to isoprene. A novel Zn-Fe layered double hydroxide catalyst was synthesized for fluidized beds. The catalytic tests were conducted in a micro fluidized-bed reactor with a tapered inner diameter from 4 to 9mm and a fixed-bed reactor of the same size. In comparison with the fixed bed, the micro fluidized bed showed higher conversion and selectivity with a low ratio of steam to olefin over a wide range of conditions. This unusual results lie in the coupling of the intense back-mixing in fluidized beds with the Mars-van Krevelen ODH mechanism. Our simplified modelling reveals the strong nonlinearity of the kinetics coupled with strong back mixing can achieve better conversion and selectivity in the fluidized bed than the fixed bed at isothermal condition. Our results also suggest that isothermal fixed bed catalyst tests cannot guarantee the best conversion and selectivity for complex ODH reactions. Catalyst tests should be carried out both in fixed beds and micro fluidized beds with back mixing as early as in the stage of catalyst screening and development.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Synthesis of efficient SBA-15 immobilized ionic liquid catalyst and its
           performance for Friedel–Crafts reaction
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Yibo He, Qinghua Zhang, Xiaoli Zhan, Dang-guo Cheng, Fengqiu Chen
      Friedel–Crafts alkylation of benzene with 1-dodecene, which is an important reaction of synthetic detergent, was studied via ionic liquid [bmim][TFSI]/AlCl3 (1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide/AlCl3) immobilized on SBA-15 catalysts. XRD, BET, TEM, TG, ammonia TPD investigations were used to search insight into catalyst characteristic. The immobilized catalysts preserved ordered structure and presented high specific surface areas. The utilization of active sites was significantly improved by immobilization. Based on ammonia TPD, immobilized catalysts exhibited higher Lewis acidity than aluminum chloride grafted SBA-15. TG indicated that thermal stability of ionic liquid has been improved by immobilization. The influences of various reaction conditions including reaction time, benzene/1-dodecene ratio were studied. Immobilized ionic liquids have better performance of no matter 1-dodecene conversion or 2-linear alkyl benzene (2-LAB) selectivity, than bulk ionic liquid catalysts or aluminum chloride grafted mesoporous materials. 2-LAB selectivity can be increased from about 35% with bulk ionic liquid to more than 60% with immobilized catalysts. Under optimal condition, 2-LAB selectivity reached as high as 80%. The immobilized catalysts could be reused. And at 3th cycle of catalysts, 1-dodecene conversion could still reach more than 50%. The role of deactivation was proposed based on TEM, BET and TG investigations. By-products as oligomer, produced by oligomerization of olefin, blocked or covered the pores, led to deactivation of catalysts.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Selective aromatization of biomass derived diisobutylene to p-xylene over
           supported non-noble metal catalysts
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Gangli Zhu, Pinhong Li, Feng Zhao, Huanling Song, Chungu Xia
      To obtain the valuable p-xylene from biomass with a high selectivity, several transition non-noble metals as main components of catalysts for aromatization of diisobutylene were explored. A volcano curve with the top marked by Cr(3d54s1) could be found between the activity and the atomic outer-shell electrons number of transition metals. The further addition of alkaline earth metal showed that the modification of surface properties by Mg doping could improve the catalytic performance. With Cr–Mg–Al–O as catalysts, the enhanced selectivity and single pass yield for the p-xylene formation could be obtained. Meanwhile, the side reaction of cracking could be suppressed, which might be attributed to the increment of the weak/strong acid ratio by Mg addition. Moreover, the catalysts kept a stable catalytic performance in the regeneration and reuse cycles.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Selective oxidation of furfural in a bi-phasic system with homogeneous
           acid catalyst
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Xiaodan Li, Xiaocheng Lan, Tiefeng Wang
      The selective catalytic oxidation of furfural to 2(5H)-furanone, succinic acid (SA) and maleic acid (MA) was studied. Under optimized conditions, furfural was oxidized to 2(5H)-furanone with a yield of 60–62% in an aqueous/organic bi-phasic system using 1,2-dichloroethane or ethyl acetate as the solvent and formic acid as the catalyst, while the total yield of SA and MA was 15–20%. Compared with other homogeneous and heterogeneous acid catalysts, formic acid gave a much higher selectivity to 2(5H)-furanone because it reacted with hydrogen peroxide to generate performic acid that had a strong oxidizing nature and good solubility in both the aqueous and organic phases. The solvent had a significant influence on the product distribution. A simplified reaction network was established to quantitatively analyze the solvent effect based on the reaction rate constants. In the homogeneous system, the yield of 2(5H)-furanone decreased while the yield of SA increased with an increasing dielectric constant of the solvent. The formic acid/furfural molar ratio, reaction temperature and furfural concentration were optimized for the selective oxidation of furfural to 2(5H)-furanone in the bi-phasic reaction system.
      Graphical abstract image

      PubDate: 2016-09-06T19:06:32Z
       
  • Modeling and kinetics study of Bisphenol A (BPA) degradation over an
           FeOCl/SiO2 Fenton-like catalyst
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Xue-jing Yang, Xi-meng Xu, Xin-chao Xu, Jing Xu, Hua-lin Wang, Raphael Semiat, Yi-fan Han
      A heterogeneous Fenton-like catalyst was used for the oxidation of Bisphenol A (BPA), which is a typical endocrine disruptor. A simple semi-empirical kinetic equation was developed to define the effects of experimental conditions (initial concentration of H2O2, initial concentration of BPA, temperature and the catalyst loading) on the reaction rate. The plausible pathway of the degradation process was proposed. A pseudo-first-order reaction rate expression with respect to BPA concentration was developed to fit all data for these experiments, and the equation of k obs (observed rate constant) was obtained with the apparent activation energy of 42.2kJ/mol. In order to reduce the operational cost, the values of parameters (temperature, initial concentration of H2O2 and pH) that optimize the catalytic performance were studied by means of a response surface methodology. Finally, a plausible mechanism was proposed on the basis of kinetics and optimization studies, which illustrates the reaction process and optimization in a microscopic view.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Light olefins from renewable resources: Selective catalytic dehydration of
           
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Xin Li, Amit Kant, Yingxin He, Harshul V. Thakkar, Marktus A. Atanga, Fateme Rezaei, Douglas K. Ludlow, Ali A. Rownaghi
      Propylene is an important constituent of many products that we rely upon in our daily life. This essential raw material is currently produced from fossil-derived feedstocks such as oil and natural gas. However, conversion of bioethanol to propylene represents an interesting opportunity for the utilization of renewable feedstocks such as bioethanol as one of the main biomass-derived products via dehydration process. The catalytic production of propylene from bioethanol has gained significant attention recently as a renewable alternative to conventional technologies. This review will discuss the state-of-the-art on the use of catalytic materials, such as zeolites and transition metals, in catalytic conversion of bioethanol to propylene and related reactions. The corresponding mechanisms are reviewed with emphasis on the possibilities provided by these materials to develop alternative processes for selective production of propylene and other olefins from bioethanol. Important aspects such as catalyst texture and architecture, the impact of promoters and co-feeding water on ethanol to propylene reaction and fundamental understanding of reaction mechanisms involved in ethanol dehydration reaction are discussed accordingly.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Commercial analysis of catalytic hydroprocessing technologies in producing
           diesel and gasoline by light cycle oil
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Chong Peng, Xiang-chen Fang, Rong-hui Zeng, Rong Guo, Wen-yue Hao
      Four main catalytic hydro-processing technologies of light cycle oil (LCO) were investigated in detail under typical pilot-scale operations aiming to provide industrial analysis of oil quality upgrading and to meet the various end-use applications. It is found that ultra-deep hydrodesulfurization (HDS) technology can effectively remove sulfur and nitrogen, however its performance on the improvement of cetane number and decreasing of density is limited. The property makes it suitable for production of fuel oils. Maximally improving LCO cetane number (MCI) technology is favorable for producing diesel with high cetane number by partial ring-opening of aromatics without side-chain cleavage. Medium-Pressure Hydro-upgrading (MHUG) technology partially converts LCO into naphtha for production of diesel with low density and high cetane number at medium pressure. Meanwhile, the by-product-heavy naphtha with high potential aromatic content occurs. Moreover, LCO hydrocracking (FD2G) technology employs relatively higher temperature with varied pressure, avoiding thermodynamic limits, to promote the conversion of di- and tri-aromatics into monoaromatics. This technology not only produces high octane number gasoline, but also upgrades the quality of diesel. The industrial analysis here could guide the design and optimization of LCO hydro-processing technology for fuel quality upgrading.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Contents list
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276


      PubDate: 2016-09-06T19:06:32Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276


      PubDate: 2016-09-06T19:06:32Z
       
  • Atomically dispersed Pd catalysts for the selective hydrogenation of
           succinic acid to γ-butyrolactone
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Chi Zhang, Lifang Chen, Hongye Cheng, Xuedong Zhu, Zhiwen Qi
      Heterogeneous palladium catalysts with high atom-efficiency offer practical value for selective hydrogenation. Here, we prepared atomically dispersed Pd species supported on γ-AlOOH nanosheets (Pd/γ-AlOOH), which contain clusters and dominated single atoms. Even with an extremely low amount of Pd loading, the catalytic activity of 0.1Pd/γ-AlOOH leads to 50.3% of succinic acid conversion at 4h. At the time, the succinic acid conversion reaches 90.7% and 97.1%, and the selectivity to γ-butyrolactone is high up to 96.9% and 93.8% over 0.5Pd/γ-AlOOH and 1.0Pd/γ-AlOOH, respectively. The supported Pd single atom (Pd1/γ-AlOOH) Exhibits 30- and 1100-fold increase in the catalytic activity compared with the supported clusters Pd13/γ-AlOOH and Pd55/γ-AlOOH for the selective hydrogenation of succinic acid to γ-butyrolactone, respectively. Analysis of the structural properties confirms that Pd single atoms on γ-AlOOH (010) surface have high adsorption energy, which is in agreement with catalytic efficiency. In addition, Pd single atoms in the catalyst 0.2Pd/γ-AlOOH account for 86.6% of the overall catalytic activity and can serve as the most efficient catalytic active sites.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Low temperature catalytic hydrogenation naphthalene to decalin over
           highly-loaded NiMo, NiW and NiMoW catalysts
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Huan Liu, Chenguang Liu, Changlong Yin, Bin Liu, Xuehui Li, Yanpeng Li, Yongming Chai, Yunqi Liu
      Hydrogenation of naphthalene to decalin at low temperatures (140–240°C) was studied over highly-loaded sulfided NiMo, NiW, and NiMoW catalysts with a supported NiMo/γ-Al2O3 catalyst as comparison. The NiMo, NiW, and NiMoW catalyst precursors were synthesized by hydrothermal reactions, and the corresponding highly-loaded catalysts were made by mixing the precursors with an alumina gel. The catalyst precursors, oxide and sulfided highly-loaded catalysts were characterized by XRD, N2 adsorption-desorption, SEM, and TPR techniques. A highly crystalline phase of ammonium nickel molybdate was detected on the NiMo precursor, and the NiW precursor exhibited sharp XRD peaks attributed to a phase of hydrated tungsten oxide. Typical Ni3S2 and MoS2/WS2 nanoparticles were observed over the sulfided highly-loaded catalysts, and a main reduction peak was detected due to nickel sulfide as revealed by TPR. Catalytic results showed that more than 99.0% of naphthalene was hydrogenated over the sulfided highly-loaded catalysts at 200°C or higher temperatures, with a very high selectivity to decalin (more than 99.9%) during the same temperature regions over the NiMo and NiMoW catalysts. As a comparison, the reference NiMo/γ-Al2O3 catalyst showed a moderate hydrogenation activity with a naphthalene conversion of 49.6% and a decalin selectivity of 40.1% at 300°C. The ratios of trans- to cis-decalin on the highly-loaded catalysts and on the NiMo/γ-Al2O3 catalysts varied.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Synthesis of hydrogen peroxide over Pd/SiO2/COR monolith catalysts by
           anthraquinone method
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Yanyan Guo, Chengna Dai, Zhigang Lei, Biaohua Chen, Xiangchen Fang
      In this work, a series of Pd/SiO2/COR (cordierite) catalysts with different Pd contents were successfully prepared by impregnation method. The obtained Pd/SiO2/COR catalyst samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), BET, hydrogen temperature programmed reduction (H2-TPR), inductively coupled plasma-atomic emission spectrometry (ICP-AES), and X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectroscopy (XPS) show that Pd element is mainly in the state of PdO, and 1.5% Pd/SiO2/COR catalyst with the theoretical Pd content of 1.5% has the most PdO content on the monolith channel surface when compared to other Pd content monolith catalysts in this paper. Then in the experiment it was found the optimum catalyst is 1.5% Pd/SiO2/COR, which is consistent with XPS results. The STY can achieve 793.2g H2O2 g−1 Pdh−1 over 1.5% Pd/SiO2/COR catalyst.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Ni-containing Cu/SiO2 catalyst for the chemoselective synthesis of ethanol
           via hydrogenation of dimethyl oxalate
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Yujun Zhao, Shuo Zhao, Yaochen Geng, Yongli Shen, Hairong Yue, Jing Lv, Shengping Wang, Xinbin Ma
      A highly efficient nickel doped Cu/SiO2 catalyst was investigated for the vapor-phase selective hydrogenation of dimethyl oxalate to ethanol. Nickel species were introduced into a silica-supported copper catalyst by an impregnation method. An appropriate amount of Ni significantly enhanced the ability of H2 to adsorb and dissociate on the Cu/SiO2 catalyst. Consequently, the catalytic performance of the catalyst was greatly improved and a selectivity for ethanol of 90% was achieved with the catalyst with 1wt% Ni. Moreover, the addition of nickel resulted in the formation of Cu–Ni bimetallic nanoparticles and surface segregation occurs in bimetallic nanoparticles. When excessive amount of nickel was introduced into the Cu/SiO2 catalyst, the catalytic performance deteriorated because of serious surface segregation and aggregation of the copper.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Silver/hydroxyapatite foam as a highly selective catalyst for acetaldehyde
           production via ethanol oxidation
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Jing Xu, Xin-Chao Xu, Xue-Jing Yang, Yi-Fan Han
      In this study, highly dispersed sliver (Ag) nanoparticles supported on a hydroxyapatite showed a surprisingly high activity (1.38s−1 in turnover frequency (TOF)), selectivity (∼100%) and durability (∼100h) for the oxidative dehydrogenation of ethanol to acetaldehyde. The structure of Ag nanoparticles is characterized using transmission electron microscopy (TEM), X-Ray Diffraction (XRD), in-situ and ex-situ X-ray photoelectron spectroscopy (XPS) and temperature-programmed surface reaction (TPSR). Density Functional Theory (DFT) calculations on Ag(111) were performed to understand the mechanism of catalytic reactions at a molecular level. The calculation results revealed that the barrier for the formation of acetaldehyde is 38.6kJ/mol, and 126.4kJ/mol for CO2 formation, thus leading to high selectivity to acetaldehyde. By combination of DFT calculation and experimental work, it can be concluded that ethanol oxidation predominantly took place on the terrace surface although step surface are more active. This study provides a methodology to develop completely selective practical catalysts especially for the utilization of biomass.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Simulation of hydrodynamic and mass transfer performances in monolith
           channel
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Zhigang Lei, Yanyan Guo, Chengna Dai, Linghua Zi, Biaohua Chen
      In this work, the gas-liquid two-phase flow patterns and characteristics in Taylor flow regime in monolith channel were simulated by means of volume of fluid (VOF) method taking benzene and propylene as model system. Four types of flow patterns (i.e., bubbly flow, Taylor flow, Taylor-annular flow, and annular flow) were first identified in the range of gas velocity from 0.01 to 3.0ms−1 and liquid velocity from 0.01 to 0.05ms−1. Then, the effect of contact angle and superficial velocity on hydrodynamic performance was investigated, confirming that the angle 0° is more appropriate. The hydrodynamic performance was intensified in the region of thin liquid film between gas bubble and the wall as well as the interface between gas bubble caps and liquid slug. Finally, the mass transfer performance of two-phase flow in monolith channel was investigated using one Taylor unit cell model. It was found that the mass transfer coefficients for monolith catalyst in Taylor flow regime is at least one order of magnitude higher than those for both structured catalytic packings and traditional pellet catalyst, exhibiting the advantage of monolith catalyst for process intensification.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Kinetics of poly(3-hydroxybutyrate) hydrolysis using acidic functionalized
           ionic liquid as catalyst
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Xiuyan Song, Fusheng Liu, Shitao Yu
      Hydrolysis of poly(3-hydroxybutyrate) (PHB) was studied using acidic functionalized ionic liquid 1-methyl-3-(3-sulfopropyl)-immidazolium hydrogen sulfate ([HSO3-pmim][HSO4]) as catalyst. The influences of experimental parameters, such as reaction temperature, reaction time, the amount of catalyst and mole ratio of water to PHB were investigated. Under the conditions of reaction temperature 160°C, reaction time 4.0h, m([HSO3-pmim][HSO4]):m(PHB)=0.06:1 and n(H2O):n(PHB)=7:1, the conversion of PHB was over 98%. The ionic liquid could be reused up to 6 times without apparent decrease in the conversion of PHB. In addition, the kinetics of the reaction was investigated, the result indicated that hydrolysis of PHB in [HSO3-pmim][HSO4] was a first-order kinetic reaction and the activation energy was 171.1kJ/mol.
      Graphical abstract image

      PubDate: 2016-09-06T19:06:32Z
       
  • Synthesis of 7-hydroxy-4-methylcoumarin via the Pechmann reaction with
           PVP-supported phosphotungstic acid catalyst
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Sifang Li, Xiaoxia Qi, Binbin Huang
      A novel method for synthesis of 7-hydroxy-4-methylcoumarin from resorcinol and ethyl acetoacetate via the Pechmann reaction with polyvinylpyrrolidone-supported phosphotungstic acid (PVP–HPW) catalyst is developed. The catalysts were characterized by FTIR, TGA, elemental analysis, UV–vis and a Hammet acidity function test. HPW protonated PVP to form polymeric cations. The polymeric cations interacted strongly with phosphotungstic anions, leading to an ionic liquid structure. The performance of the PVP–HPW were compared with other catalysts such as HPW, NMP–H2SO4 and PVP–H2SO4. For PVP–HPW dosage of 9% based on the weight of resorcinol, the yield of 7-hydroxy-4-methylcoumarin reached 96.73% after two hours reflux reaction at 110°C, which exhibited much higher value than other catalysts. The PVP–HPW can be easily separated from the reaction mixture and retains the activity during recycling.
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      PubDate: 2016-09-06T19:06:32Z
       
  • Gas-phase epoxidation of propylene by molecular oxygen over Ag/BaCO3
           catalysts: Effect of preparation conditions
    • Abstract: Publication date: 1 November 2016
      Source:Catalysis Today, Volume 276
      Author(s): Qing Zhang, Yanglong Guo, Wangcheng Zhan, Yun Guo, Li Wang, Yunsong Wang, Guanzhong Lu
      Ag/BaCO3 catalysts with different Ag crystallite sizes, prepared by the reduction-deposition method, were developed for gas-phase epoxidation of propylene to propylene oxide (PO) by molecular oxygen. Effects of preparation conditions, such as pretreatment of organic amines of BaCO3 support, pretreatment way of ethylene diamine, reduction temperature of HCHO and calcination temperature, on the catalytic performance and Ag crystallite size of Ag/BaCO3 catalyst were investigated. Ag/BaCO3 * catalyst, with pretreatment of BaCO3 support by ethylene diamine and prepared at the reduction temperature of HCHO of 10°C and the calcination temperature of 250°C, exhibited better catalytic performance and good durability, in which 12.5% of propylene conversion and 36.9% of PO selectivity were achieved under the reaction conditions of 20%C3H6–10%O2–70%N2, 200°C, 0.1MPa and GHSV of 3000h−1. Both lower reduction temperature of HCHO and lower calcination temperature can get smaller Ag crystallite sizes, which is more effective for epoxidation of propylene over Ag/BaCO3 * catalyst. The catalytic reaction mechanism of Ag/BaCO3 * catalyst for epoxidation of propylene is that propylene in the gas phase reacts with molecular oxygen species adsorbed on the catalyst surface to produce PO and follows Rideal–Eley mechanism.
      Graphical abstract image

      PubDate: 2016-09-06T19:06:32Z
       
  • 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
       
 
 
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