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Publisher: Elsevier   (Total: 2807 journals)

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Tetrahedron: Asymmetry     Hybrid Journal   (Followers: 7)
Textile Science and Technology     Full-text available via subscription   (Followers: 4)
The Alkaloids: Chemistry and Biology     Full-text available via subscription   (Followers: 1, SJR: 0.348, h-index: 20)
The American J. of Cardiology     Hybrid Journal   (Followers: 26, SJR: 2.315, h-index: 169)
The American J. of Emergency Medicine     Hybrid Journal   (Followers: 23)
The American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 3, SJR: 1.322, h-index: 36)
The American J. of Medicine     Hybrid Journal   (Followers: 41, SJR: 1.847, h-index: 168)
The American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
The American J. of Surgery     Hybrid Journal   (Followers: 24, SJR: 1.328, h-index: 114)
The Arts in Psychotherapy     Hybrid Journal   (Followers: 6)
The Breast     Hybrid Journal   (Followers: 5)
The British Accounting Review     Hybrid Journal   (Followers: 6, SJR: 0.634, h-index: 34)
The Chemical Physics of Solid Surfaces     Full-text available via subscription  
The Cytoskeleton: A Multi-Volume Treatise     Full-text available via subscription  
The Electricity J.     Partially Free   (Followers: 3, SJR: 0.517, h-index: 25)
The Enzymes     Full-text available via subscription   (Followers: 1, SJR: 0.339, h-index: 7)
The Extractive Industries and Society     Hybrid Journal  
The Foot     Hybrid Journal   (Followers: 8)
The Geochemical Society Special Publications     Full-text available via subscription   (Followers: 1)
The History of Neuroscience in Autobiography     Full-text available via subscription   (Followers: 1)
The Internet and Higher Education     Hybrid Journal   (Followers: 81, SJR: 2.565, h-index: 40)
The Intl. J. of Accounting     Hybrid Journal   (Followers: 1)
The Intl. J. of Biochemistry & Cell Biology     Hybrid Journal   (Followers: 4, SJR: 2.423, h-index: 128)
The J. for Nurse Practitioners     Hybrid Journal   (Followers: 4, SJR: 0.136, h-index: 7)
The J. of Arthroplasty     Hybrid Journal   (Followers: 40)
The J. of Chemical Thermodynamics     Hybrid Journal   (Followers: 3, SJR: 1.292, h-index: 52)
The J. of Foot and Ankle Surgery     Full-text available via subscription   (Followers: 10)
The J. of Hand Surgery     Full-text available via subscription   (Followers: 32)
The J. of Heart and Lung Transplantation     Hybrid Journal   (Followers: 6, SJR: 2.881, h-index: 86)
The J. of High Technology Management Research     Hybrid Journal   (Followers: 1, SJR: 0.245, h-index: 26)
The J. of Logic and Algebraic Programming     Hybrid Journal   (Followers: 2, SJR: 0.647, h-index: 38)
The J. of Mathematical Behavior     Hybrid Journal   (Followers: 1, SJR: 0.766, h-index: 24)
The J. of Molecular Diagnostics     Hybrid Journal   (Followers: 1, SJR: 1.974, h-index: 57)
The J. of Nutritional Biochemistry     Hybrid Journal   (Followers: 1, SJR: 1.627, h-index: 88)
The J. of Pain     Hybrid Journal   (Followers: 9)
The J. of Pediatrics     Hybrid Journal   (Followers: 75)
The J. of Prosthetic Dentistry     Full-text available via subscription   (Followers: 2)
The J. of Socio-Economics     Hybrid Journal   (Followers: 4, SJR: 0.356, h-index: 29)
The J. of Strategic Information Systems     Hybrid Journal   (Followers: 15, SJR: 2.903, h-index: 50)
The J. of Supercritical Fluids     Hybrid Journal   (Followers: 3, SJR: 1.141, h-index: 69)
The J. of the American College of Certified Wound Specialists     Hybrid Journal   (Followers: 1, SJR: 0.14, h-index: 3)
The J. of Thoracic and Cardiovascular Surgery     Hybrid Journal   (Followers: 7, SJR: 2.268, h-index: 143)
The J. of Urology     Full-text available via subscription   (Followers: 57)
The Kaohsiung J. of Medical Sciences     Full-text available via subscription  
The Knee     Hybrid Journal   (Followers: 13, SJR: 1.137, h-index: 44)
The Lancet     Full-text available via subscription   (Followers: 1357, SJR: 11.563, h-index: 514)
The Lancet Diabetes and Endocrinology     Full-text available via subscription   (Followers: 17)
The Lancet Global Health     Open Access   (Followers: 20)
The Lancet Haematology     Full-text available via subscription  
The Lancet HIV     Full-text available via subscription   (Followers: 1)
The Lancet Infectious Diseases     Full-text available via subscription   (Followers: 76, SJR: 9.527, h-index: 133)
The Lancet Neurology     Full-text available via subscription   (Followers: 24, SJR: 11.052, h-index: 165)
The Lancet Oncology     Full-text available via subscription   (Followers: 27, SJR: 14.764, h-index: 153)
The Lancet Psychiatry     Full-text available via subscription   (Followers: 6)
The Lancet Respiratory Medicine     Full-text available via subscription   (Followers: 9)
The Leadership Quarterly     Hybrid Journal   (Followers: 40, SJR: 2.069, h-index: 76)
The North American J. of Economics and Finance     Hybrid Journal   (Followers: 1, SJR: 0.667, h-index: 20)
The Quarterly Review of Economics and Finance     Hybrid Journal   (Followers: 13, SJR: 0.565, h-index: 26)
The Social Science J.     Hybrid Journal   (Followers: 4, SJR: 0.255, h-index: 18)
The Spine J.     Hybrid Journal   (Followers: 13, SJR: 1.493, h-index: 62)
The Surgeon     Hybrid Journal   (Followers: 1, SJR: 0.784, h-index: 25)
The Veterinary J.     Hybrid Journal   (Followers: 10, SJR: 1.005, h-index: 63)
Theoretical and Applied Fracture Mechanics     Hybrid Journal   (Followers: 6, SJR: 1.179, h-index: 35)
Theoretical and Computational Chemistry     Full-text available via subscription   (Followers: 7)
Theoretical Computer Science     Hybrid Journal   (Followers: 4, SJR: 0.932, h-index: 74)
Theoretical Ecology Series     Full-text available via subscription   (Followers: 1)
Theoretical Population Biology     Hybrid Journal   (Followers: 11, SJR: 0.973, h-index: 61)
Theriogenology     Hybrid Journal   (Followers: 2, SJR: 1.059, h-index: 89)
Thermochimica Acta     Hybrid Journal   (Followers: 16, SJR: 0.645, h-index: 77)
Thin Films and Nanostructures     Full-text available via subscription   (Followers: 3)
Thin Solid Films     Hybrid Journal   (Followers: 10, SJR: 0.884, h-index: 130)
Thin-Walled Structures     Hybrid Journal   (Followers: 1, SJR: 1.786, h-index: 38)
Thinking Skills and Creativity     Hybrid Journal   (Followers: 11, SJR: 0.709, h-index: 15)
Thoracic Surgery Clinics     Full-text available via subscription   (Followers: 1, SJR: 0.311, h-index: 35)
Thrombosis Research     Hybrid Journal   (Followers: 25, SJR: 1.098, h-index: 80)
Ticks and Tick-borne Diseases     Hybrid Journal   (Followers: 5, SJR: 0.943, h-index: 12)
Tissue and Cell     Hybrid Journal   (Followers: 2, SJR: 0.464, h-index: 35)
Topics in Companion Animal Medicine     Hybrid Journal   (Followers: 1, SJR: 0.521, h-index: 28)
Topics in Inorganic and General Chemistry     Full-text available via subscription  
Topology     Full-text available via subscription  
Topology and its Applications     Full-text available via subscription   (SJR: 0.663, h-index: 28)
Tourism Management     Hybrid Journal   (Followers: 9, SJR: 1.961, h-index: 80)
Tourism Management Perspectives     Hybrid Journal   (Followers: 1, SJR: 0.476, h-index: 4)
Toxicologie Analytique et Clinique     Full-text available via subscription  
Toxicology     Hybrid Journal   (Followers: 12, SJR: 1.196, h-index: 105)
Toxicology and Applied Pharmacology     Hybrid Journal   (Followers: 12, SJR: 1.429, h-index: 117)
Toxicology in Vitro     Hybrid Journal   (Followers: 7, SJR: 0.923, h-index: 63)
Toxicology Letters     Hybrid Journal   (Followers: 8, SJR: 1.098, h-index: 101)
Toxicology Reports     Open Access  
Toxicon     Hybrid Journal   (Followers: 3, SJR: 1.008, h-index: 88)
TrAC Trends in Analytical Chemistry     Full-text available via subscription   (Followers: 20, SJR: 2.325, h-index: 103)
Trace Metals and other Contaminants in the Environment     Full-text available via subscription   (Followers: 2, SJR: 0.101, h-index: 5)
Trace Metals in the Environment     Full-text available via subscription   (Followers: 2)
Transactions of Nonferrous Metals Society of China     Hybrid Journal   (Followers: 8, SJR: 0.893, h-index: 27)
Transfusion and Apheresis Science     Hybrid Journal   (SJR: 0.56, h-index: 37)
Transfusion Clinique et Biologique     Full-text available via subscription   (Followers: 1, SJR: 0.396, h-index: 30)
Transfusion Medicine Reviews     Hybrid Journal   (Followers: 1, SJR: 1.821, h-index: 48)
Translational Oncology     Open Access   (SJR: 1.282, h-index: 23)
Translational Proteomics     Open Access  
Translational Research     Full-text available via subscription   (Followers: 3, SJR: 1.443, h-index: 66)

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Journal Cover   Catalysis Today
  [SJR: 1.378]   [H-I: 142]   [6 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2807 journals]
  • Green bioprocesses in sponge-like ionic liquids
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Pedro Lozano, Juana M. Bernal, Celia Gómez, Eduardo García-Verdugo, M. Isabel Burguete, Gregorio Sánchez, Michel Vaultier, Santiago V. Luis
      Ionic liquids (ILs) are a new class of liquid solvent, whose use has led to a green chemical revolution because of their unique array of physico-chemical properties, headed by their negligible vapour pressure and their exceptional ability to stabilize biocatalysts. Hydrophobic ILs based on cations with long alkyl side-chains, e.g. N,N,N,N-hexadecyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([C16tma][NTf2]), are temperature switchable ionic liquid/solid phases that behave as sponge-like systems (sponge-like ionic liquid, SLILs). Based on this new property, SLILs have been used to develop straightforward and clean approaches for producing nearly pure synthetic compounds with added value (e.g. geranyl acetate, anisyl acetate, methyl oleate, etc.) in two steps: an enzymatic synthetic step as liquid phase, and then a product separation step involving simple centrifugation as a solid phase.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Preface
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Pedro Lozano, Santiago V. Luis, Eduardo Garcia-Verdugo, Roberto Fernández-Lafuente



      PubDate: 2015-07-23T17:42:23Z
       
  • Enzymatic synthesis of butyl acetate in a packed bed reactor under liquid
           and supercritical conditions
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): J. Escandell, D.J. Wurm, M.P. Belleville, J. Sanchez, M. Harasek, D. Paolucci-Jeanjean
      In this work we studied the synthesis of butyl acetate in an enzymatic packed bed reactor using lipase B, from Candida antarctica, immobilized by simple physical adsorption on porous pellets. The enzymatic reaction was carried out in two different solvents: a conventional organic solvent (n-hexane) and a green solvent (supercritical carbon dioxide). The highest ester productivity in hexane ( 119   μ mol min − 1   g pellets − 1 ) was reached at 323K, whereas in supercritical CO2, a maximum productivity of 501   μ mol min − 1   g pellets − 1 was achieved at 333K and under 12MPa. The environmental impacts of each process were estimated by means of the E-factor (mass ratio of amount of waste produced divided by amount of desired product) and the values obtained under the previous conditions were 28.7 and 12.0 respectively. Results show that replacing hexane by supercritical CO2 in a continuous process increases ester productivity and reduces environmental impact, thus allowing making a more environmentally friendly process.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Synthesis of cetyl ricinoleate catalyzed by immobilized Lipozyme®
           CalB lipase in a solvent-free system
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): M.C. Montiel, M. Serrano, M.F. Máximo, M. Gómez, S. Ortega-Requena, J. Bastida
      A green process has been performed for the synthesis of the emollient ester cetyl ricinoleate with a new immobilized derivative of Candida antarctica lipase B, which has been prepared by physical adsorption of Lipozyme® CalB L on a macroporous anionic exchange resin (Lewatit® MonoPlus MP 64). An immobilized CalB lipase with protein content over 30mg/g has been obtained and it has been successfully used as biocatalyst to produce cetyl ricinoleate from esterification of ricinoleic acid with cetyl alcohol. Influence of amount of biocatalyst and temperature was studied in the open-air reactor, and optimal values could be fixed in 2mg and 70°C, respectively. Biocatalyst storage stability study was developed in this reactor and it was showed the high storage stability of the immobilized derivative, because it keeps 100% of its enzymatic activity after eight months. Studies of recovery and reuse of the immobilized derivative were performed in the vacuum reactor, and it was proved the possibility of using the same biocatalyst in three consecutive reaction cycles without apparent loss of activity. Finally, the characterization of the cetyl ricinoleate obtained in the vacuum reactor demonstrated that the product obtained after only 3 or 4h of reaction meets manufacturers’ specifications.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Lipase-mediated dynamic kinetic resolution (DKR) of secondary alcohols in
           the presence of zeolite using an ionic liquid solvent system
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Ken-ichi Shimomura, Hiroyuki Harami, Yui Matsubara, Toshiki Nokami, Naonobu Katada, Toshiyuki Itoh
      Transition metal free dynamic kinetic resolution (DKR) of 1-phenyethanol and 2,3-dihydro-1H-inden-1-ol has been accomplished by the combination of Candida antarctica lipase (CAL-B) and zeolite using vinyl octanoate or p-chlorophenyl pentanoate as acyl donor in a mixed solvent system of ionic liquid and hexane in the presence of 1.0eq. of water. Duplicated use of the catalysts has also been demonstrated in the DKR of 2,3-dihydro-1H-inden-1-ol using this reaction system.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Xylitol production from cashew apple bagasse by Kluyveromyces marxianus
           CCA510
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Tiago Lima de Albuquerque, Sandy Danielle Luncindo Gomes, José Edvan Marques Jr., Ivanildo José da Silva Jr., Maria Valderez Ponte Rocha
      The production of xylitol, a polyol with high employability in the food and pharmaceutical industry, from cashew apple bagasse hydrolysate (CABH) by a new strain of Kluyveromyces marxianus was studied. Initially, the use of activated charcoal in the detoxification of hydrolysates from CABH was evaluated. Then, the influence of the supplementation of CABH with various nitrogen sources was studied. The activated charcoal reduced the concentration of acid and phenolic compounds. K. marxianus CCA510 was able to produce xylitol using CABH, with the highest yield of 0.36gg−1 and maximum concentration of 12.73gL−1. When it was added urea in the medium the highest xylitol yield was observed, reaching 0.50gg−1, showing that substance as nitrogen source improved the xylitol production. The cashew apple bagasse hydrolysate is a potential medium for biotechnological production of xylitol and detoxification treatments can be employed to reduce potential toxic compounds present in the medium without significant loss of sugars.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Use of Lecitase-Ultra immobilized on styrene-divinylbenzene beads as
           catalyst of esterification reactions: Effects of ultrasounds
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Joana S. Alves, Cristina Garcia-Galan, Daiane Danelli, Natália Paludo, Oveimar Barbosa, Rafael C. Rodrigues, Roberto Fernandez-Lafuente
      In this work it was evaluated for the first time, the ester synthesis catalyzed by the phospholipase Lecitase-Ultra immobilized styrene-divinylbenzene beads (MCI-Lecitase), comparing the mechanical stirring and the ultrasonic energy. It was studied the specificity of the enzyme using carboxylic acids from C4 to C18, as well as the effects of alcohol chain, organic solvents, biocatalyst content, reaction temperature and substrate concentration. Caprylic and myristic acids were those with the highest reaction rates and yields, using ethanol as substrate. The shorter the alcohol chain, the higher the enzyme activity. Regarding the secondary alcohols, while MCI-Lecitase had no activity versus isopropanol, using 2-pentanol the activity was similar to that with 1-pentanol. Comparing the agitation systems, MCI-Lecitase presented an initial reaction rate more than 2-times higher in the ultrasound-assisted reaction than under traditional mechanical stirring. Moreover, under ultrasonic energy the maximum rate was achieved using 0.5M of substrates, while under mechanical stirring the maximum enzyme activity was reached at 0.3M of substrates. Concerning the operational stability, MCI-Lecitase was quite unstable, losing its activity after 6 reaction cycles. By adding molecular sieves in the reaction medium, MCI-Lecitase retained 30% of its initial activity after 6 cycles.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Asymmetric hydrolysis of dimethyl-3-phenylglutarate in sequential batch
           reactor operation catalyzed by immobilized Geobacillus thermocatenulatus
           lipase
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Nadia Guajardo, Claudia Bernal, Lorena Wilson, Zaida Cabrera
      The main goal of this work was to study the stereoselective behavior of immobilized Geobacillus thermocatenulatus lipase (BTL2) in a sequential batch reactor using the partial and asymmetric hydrolysis of dimethyl-3 phenylglutarate (DMFG) as a model reaction. To reach this goal, BTL2 lipase was immobilized on Sepharose and silica supports with cyanogen bromide and octyl groups (monofunctional supports) and undecanol-glyoxyl and octyl-epoxides groups (heterofunctional supports), to determine the effect of the enzyme orientation during the immobilization process on their catalytic properties. In the hydrolysis of DMFG, the biocatalyst obtained with undecanol-glyoxyl Sepharose proved to be the most stereolective with an enantiomeric excess (e.e.) value of 90% in aqueous media. This behavior can be attributed to differences in the orientation of the lipase on the support. In sequential batch reactor operation, the e.e. remained constant in the first two batches; however, from the third batch on the e.e. decreased slightly maybe due to a change in the conformation of the enzyme at the reaction conditions. Finally, the high purity S-methyl-3-phenyl glutarate produced in sequential batch reactor operation shows that the biocatalyst can be reused at least twice without losing stereoselectivity, favoring a reduction in the process cost.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Kinetic resolution of esters from secondary and tertiary benzylic
           propargylic alcohols by an improved esterase-variant from Bacillus sp.
           BP-7
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Amanda Fillat, Pedro Romea, F.I. Javier Pastor, Fèlix Urpí, Pilar Diaz
      We described in a recent work the rational improvement of an esterase from Bacillus sp. BP7 aimed at investigating the efficiency of several esterase variants for enantiomeric resolution of acetate esters of tertiary alcohols. Variant EstBP7-AGA, bearing two aminoacidic changes in the oxyanion hole, showed an excellent E >100 enantioselectivity value towards a complex tertiary alcohol acetate (2-(4-pyridyl)-3-butyn-2-yl acetate) at low reaction temperature (4°C). We here go further in the investigation of such esterase variant by analyzing the kinetic resolution of benzylic propargylic esters to prove that this enzyme is a powerful tool to obtain enantiomerically pure tertiary as well as secondary alcohols, provided that the structural integrity of the parent benzylic propargylic ester is maintained. Understanding the mode of action and interaction of such esterase variant with the assayed substrates will allow production of interesting pharmaceutical building blocks.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Production of a biosurfactant by Bacillus subtilis ICA56 aiming
           bioremediation of impacted soils
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Ítalo Waldimiro Lima de França, Andrea Parente Lima, João Alexandre Monteiro Lemos, Celina Gentil Farias Lemos, Vania Maria Maciel Melo, Hosiberto Batista de Sant’ana, Luciana Rocha Barros Gonçalves
      This work aimed to study the production of a biosurfactant by a new strain of Bacillus subtilis ICA56 isolated from a Brazilian mangrove and to evaluate its functional properties and applicability for bioremediation. The use of agro-industrial wastes (glycerol, sunflower oil, cheese whey and cashew apple juice) as alternative substrates for biosurfactant production was tested as this may lead to a reduction in the cost of the bioprocess. Glycerol was the best carbon source yielding 1290mgL−1 of crude biosurfactant. The critical micellar concentration of the crude biosurfactant produced by ICA56 was 25mgL−1 and, at this concentration, it was able to reduce the surface tension of the water from 72 to 30mNm−1 and to reduce the interfacial tension on a water/gasoline system from 15 to 3mNm−1. Furthermore, the crude biosurfactant retained its tensoative properties in a broad range of pH, temperature and salinity and it was not toxic to Artemia salina. In this work, model experiments were conducted to simulate the removal of hydrocarbons and heavy metals from contaminated environmental systems in the laboratory by the crude biosurfactant produced by ICA56. Results showed that it was very efficient, highlighting its potential for bioremediation.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255




      PubDate: 2015-07-23T17:42:23Z
       
  • Contents list
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255




      PubDate: 2015-07-23T17:42:23Z
       
  • Advanced nanostructured catalysts for hydroboration
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Virginie Liautard, Oana Pascu, Cyril Aymonier, Mathieu Pucheault
      Metal nanocrystals have been prepared in onium salts using supercritical carbon dioxide assisted synthesis. During the process, metal salts precursors are reduced by H2 in an organic solvent free media, the onium salts allowing both the stabilization of the nanostructured material and the preparation of an air and moisture stable powder made of embedded metal nanocrystals. Those catalysts proved to be highly effective in the hydroboration of alkyne process.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Microwaves under pressure for the continuous production of quinoline from
           glycerol
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): H. Saggadi, I. Polaert, D. Luart, C. Len, L. Estel
      Microwave heating is an interesting technology for chemical engineering, since it can provide effective volumetric heating of the reaction medium and reduce energy costs. Many commercially available laboratory-scale microwave reactors have already been used to carry out chemical reactions on a small scale (a few milliliters), and at high temperatures and pressures. Some research has been undertaken to scale-up microwave processes and make them suitable for a larger scale production. Indeed, combining wave propagation through the walls of a reactor with resistance toward high pressure and temperature as well, is not an easy task. For these reasons, this work focuses on the development of a pilot scale microwave apparatus used for the heating of larger reaction volumes under pressure, and under controlled conditions. The specially designed microwave apparatus allows chemical reactions in batch or continuous mode. The applicator operates in single mode enabling a uniform electromagnetic field, and well controlled operating conditions. The main advantage of the setup is the quite large reactor volume that permits either relatively long residence times or relatively high mass flowrates (up to 1kg/h). The developed microwave apparatus was then used for quinoline synthesis from glycerol via a modified Skraup reaction. The major advantage of our system is the ability to carry out continuous chemical synthesis, at a large pilot scale, and high temperatures (200–220°C), while ensuring a better control of the pressure (max. 19bar) through the control of the power absorbed by the reaction medium.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Direct thermo-catalytic transformation of pine wood into low oxygenated
           fuel: Influence of the support
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Anthony Garron, Walid Al Maksoud, Cherif Larabi, Philippe Arquillière, Kai C. Szeto, Jean-Jacques Walter, Catherine C. Santini
      The direct catalytic thermo-catalytic transformation of wood in presence of molecular hydrogen has been demonstrated. The resulting organic liquid consists of saturated alkanes and aromatics and was obtained with a yield up to 30wt.%. Importantly, the oxygen content is about 3wt.% (<5wt.% required for bio-fuel formulation) and has a Higher Heating Value of 41MJkg−1 which is very close to standard diesel (44MJkg−1) used in automotive fuel. The catalysts comprise multi-functional Cu–Ru supported on Cs exchanged heteropolyacid (H3PW12O40 and H3PMo12O40), featuring depolymerisation, deoxygenation and hydrogenation in a single batch reactor. Current results present an alternative approach to convert highly oxygenated lignocellulosic biomass to a low oxygenated organic liquid suitable as additives in biofuels, in one step and one reactor.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Selective transformation of fructose and high fructose content biomass
           into lactic acid in supercritical water
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Danilo A. Cantero, Luis Vaquerizo, Celia Martinez, M. Dolores Bermejo, M. José Cocero
      The reactions of fructose in sub- and supercritical water were analyzed changing the chemical properties of the reaction medium (Kw, ɛ, pH and free radical kidnapers). The reactions were performed in a continuous reactor at 260°C, 330°C and 400°C, at 23MPa and 27MPa using water as reaction medium. The pH of the medium was modified using oxalic acid and sodium hydroxide. Also, scavengers (TEMPO and BHT) were tested in order to determine its influences in the radical reactions. The main product of fructose hydrolysis in supercritical water was pyruvaldehyde (>80%, w·w−1) at 400°C and 23MPa with a reaction time of 0.7s. Furthermore, the reactions of fructose were analyzed in combination with glucose. It was determined that different retro-aldol condensation products can be obtained depending on the starting material. Fructose produced mainly C-3 molecules (pyruvaldehyde) and glucose produced mainly C-2 molecules (glycolaldehyde). The isomerization of fructose to glucose was negligible and so was the production of C-2 when the starting material was fructose. The yield of 5-HMF was negligible when the starting material was glucose. Three different biomass enriched in fructose (sugar cane molasses, beet molasses and inulin) were tested as starting material for the hydrolysis process. It was determined that lactic acid (50%, w·w−1) was the main product of molasses and inulin hydrolysis in a supercritical water medium modified with basic catalysts.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Solubility of greenhouse and acid gases on the [C4mim][MeSO4] ionic liquid
           for gas separation and CO2 conversion
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Fèlix Llovell, Mariana B. Oliveira, João A.P. Coutinho, Lourdes F. Vega
      Ionic liquids (ILs) are an exciting class of compounds of high interest from a technological point of view. One of the applications that is raising more interest is their possible use as solvents to carry out the conversion of CO2 into more valuable compounds. Theoretical approaches provide an attractive option to screen ILs properties and give quick answers to guide the experiments, becoming a crucial tool for process design. This work illustrates a practical example based on the solubility of greenhouse and acid gases on the butylmethylimidazolium methylsulfate [C4mim][MeSO4] IL, in order to study its feasibility for gas separation and conversion. A simple but reliable molecular model is presented for the ionic liquid based on structural information and molecular simulations, and coarse-grained models are used to model the different gases. The absorption of relevant gases for the separation/conversion process (CO2, CH4, CO, H2, SO2, H2S) in [C4mim][MeSO4] is modeled and compared with experimental data using a minimum amount of binary data. From this information, the ternary diagrams of [C4mim][MeSO4] with CO2 and the acid gases SO2 and H2S are predicted, and the selectivity of CO2 by respect all the gases is evaluated, with particular attention to the contaminants above mentioned.
      Graphical abstract image

      PubDate: 2015-07-23T17:42:23Z
       
  • Gold nanoparticles immobilized onto supported ionic liquid-like phases for
           microwave phenylethanol oxidation in water
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Julian Restrepo, Pedro Lozano, M. Isabel Burguete, Eduardo García-Verdugo, Santiago V. Luis
      Advanced crosslinked polymeric materials based on poly(ionic liquid)s, also named supported ionic liquid-like phases (SILLPs) combine some unique characteristics of ionic liquids with the general property profile of macromolecular architectures, and present huge potential in energy-/environment-/catalysis-oriented applications, in the development of “smart” dispersants and stabilizers, etc. One of these relevant applications is highlighted by the present results that involve their use for the preparation and stabilization of different type of catalytic units, in particular metal nanoparticles (MeNPs) in order to develop greener catalytic processes. Different kinds of stable AuNPs can be prepared from SILLPs-related polymeric materials and have been used for the efficient oxidation of phenyl ethanol, under aerobic conditions, using H2O2 as the oxidant and under microwave irradiation.
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      PubDate: 2015-07-23T17:42:23Z
       
  • Oxodiperoxomolybdenum complex immobilized onto ionic liquid modified
           SBA-15 as an effective catalysis for sulfide oxidation to sulfoxides using
           hydrogen peroxide
    • Abstract: Publication date: 15 October 2015
      Source:Catalysis Today, Volume 255
      Author(s): Carlos J. Carrasco, Francisco Montilla, Luis Bobadilla, Svetlana Ivanova, José Antonio Odriozola, Agustín Galindo
      A supported ionic-liquid-phase (SILP) was prepared by the reaction of 1-methyl-3-(3-(triethoxysilyl)propyl)-1H-imidazol-3-ium chloride with a mesoporous SBA-15 silica and then an oxodiperoxomolybdenum complex was immobilized onto the obtained SILP. The resulting material, identified as SBA-15+ImCl+MoO5, was characterized by solid state NMR (1H, 13C and 29Si), and their textural and thermogravimetric properties were determined. The SBA-15+ImCl+MoO5 material was investigated as catalyst for the oxidation of methylphenylsulfide, as model reaction, with aqueous hydrogen peroxide as oxidant at room temperature. The presence of the molybdenum species was crucial for achieving good conversions and methanol was selected as the best solvent (conversion of 95% and selectivity toward sulfoxide 98%). The optimized reaction conditions were applied for the oxidation of several selected sulfides. In general, good catalytic activity and selectivity to sulfoxide were obtained and, remarkably, the selectivity toward sulfoxide is higher than those observed in the study of the same process carried out in [C4min][PF6] (C4mim=1–butyl-3-methylimidazolium) and catalyzed by a molecular molybdenum complex, under the same reaction conditions. The importance of the IL-functionalization in the SBA-15 material was evidenced by recycling experiments. The SBA-15+ImCl+MoO5 catalyst was used for the sulfoxidation of the methylphenylsulfide substrate for ten reaction cycles without a significant change in conversion, selectivity to sulfoxide and molybdenum content.
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      PubDate: 2015-07-23T17:42:23Z
       
  • The non-innocent role of cerium oxide in heterogeneous catalysis: A
           theoretical perspective
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): M. Verónica Ganduglia-Pirovano
      Ceria (CeO2) is the most significant of the oxides of rare-earth elements in industrial catalysis with its reducibility being essential to its functionality in catalytic applications. The complexity of real (powder) catalysts hinders the fundamental understanding of how they work. Specifically, the role of ceria in the catalytic activity of ceria-based systems is still not fully understood. To elucidate it, well-defined ceria-based model catalysts are prepared experimentally or created theoretically and studied. The purpose of this brief review is to discuss recent results on model ceria-based catalysts using CeO2(111), VO x /CeO2(111), and Ni/CeO2(111) as examples of catalysts for partial alkyne hydrogenation, oxidative dehydrogenation, and hydrogen production, respectively. The emphasis is here put on theoretical studies and special attention is given to the effects of ceria as catalyst support.
      Graphical abstract image Highlights

      PubDate: 2015-06-24T06:56:26Z
       
  • Dynamic redox properties of vanadium and copper in microporous supports
           during the selective oxidation of propene
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Katrine Lie Bøyesen , Tina Kristiansen , Karina Mathisen
      Vanadium(V) and copper(II) were co-deposited into the microporous neutral AlPO-5 and the acidic ZSM-5, obtaining VCu:AlPO-5 and VCu:ZSM-5. In this study we seek to investigate the effect of feed gas composition for the selective oxidation of propene applying C3H6/O2 ratios from 4 to 0.25 over VCu:AlPO-5 and VCu:ZSM-5. The results from catalytic measurements were correlated with in situ X-ray Absorption Spectroscopy (XAS) to monitor metal speciation for different feeds. VCu:AlPO-5 produces acrolein over the whole feed composition range, reaching maximum yield (1.5%) for C3H6/O2 =0.5. In situ XAS reveal that when the major valence fractions present are the Cu(I)/Cu(II) and V(III)/VIV) redox pairs, the selectivity and activity is improved over VCu:AlPO-5. By comparison, VCu:ZSM-5 produce acrolein for C3H6/O2 =1 and 0.5 only, but with significantly lower yields (0.1% and 0.2%, respectively). At these conditions copper is mainly present as Cu(0), whereas vanadium exists as V(III)/V(IV). We believe activity is governed by the presence of available oxygen associated with a binuclear Cu/V complex in VCu:AlPO-5, not formed in the zeolite. Also, the activity is independent of copper valence state, indicating a possible Cu0/VO x interface is present in VCu:AlPO-5.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Total oxidation of propane in vanadia-promoted platinum-alumina catalysts:
           Influence of the order of impregnation
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Tomas Garcia , Said Agouram , Stuart H. Taylor , David Morgan , Ana Dejoz , Isabel Vázquez , Benjamin Solsona
      Differently prepared vanadium promoted Pt/alumina catalysts have been prepared, characterized and tested for propane total oxidation. V-promoted Pt/Al2O3 catalysts have shown remarkably higher catalytic activity than V-free Pt/Al2O3 catalyst. Among V-promoted Pt catalysts that prepared by coimpregnation gave the highest alkane conversions in the whole range of reaction temperatures studied. Factors such as Pt particle size or the oxidation state of platinum do not seem to be the responsible for the enhanced performance. Modification of the redox properties of the catalyst (i.e. high reducibility of vanadium species) likely provoked by the close contact between platinum particles and vanadium species and the partial introduction of vanadium in the platinum particles can be related to the improved reactivity of the PtV catalysts.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Formation of BaMnO3 in Ba/MnOx–CeO2 catalyst upon the hydrothermal
           ageing and its effects on oxide sintering and soot oxidation activity
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Yuxi Gao , Xiaodong Wu , Shuang Liu , Duan Weng , Hongwei Zhang , Rui Ran
      MnO x –CeO2 mixed oxides were synthesized using a sol–gel method and the barium-loaded catalyst was prepared by a wet impregnation. Both catalysts were hydrothermally aged at 800°C for 10h. The fresh and aged catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), high-resolution transmission electron microscopy (HRTEM), H2 temperature-programmed reduction (H2-TPR), NO temperature-programmed oxidation (NO-TPO) and soot temperature-programmed oxidation (soot-TPO). Compared with MnO x –CeO2, the Ba-modified mixed oxides show a much higher hydrothermal stability. Barium exists in the form of orthorhombic carbonate and cubic nitrate on the fresh sample. BaMnO3 nanoparticles are identified to form at the interface of CeO2 crystallites upon the hydrothermal ageing. The formation of the perovskites prohibits the sintering of ceria significantly, and consequently maintains the redox property of the aged mixed oxides to a great degree. Additionally, the nanoscaled perovskites themselves also contribute to the catalytic activity of the aged oxides catalyst.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Effect of the CeZrNd mixed oxide synthesis method in the catalytic
           combustion of soot
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Jorge González Mira , Verónica Rico Pérez , Agustín Bueno-López
      Ce0.64Zr0.27Nd0.09O δ mixed oxides have been prepared by three different methods (nitrates calcination, coprecipitation and microemulsion), characterized by N2 adsorption, XRD, H2-TPR, Raman spectroscopy and XPS, and tested for soot combustion in NO x /O2. The catalyst prepared by microemulsion method is the most active one, which is related to its high surface area (147m2/g) and low crystallite size (6nm), and the lowest activity was obtained with the catalyst prepared by coprecipitation (74m2/g; 9nm). The catalyst prepared by nitrates precursors calcination is slightly less active to that prepared by microemulsion, but the synthesis procedure is very straightforward and surfactants or other chemicals are not required, being very convenient for scaling up and practical utilization. The high activity of the catalyst prepared by nitrates calcination can be attributed to the better introduction of Nd cations into the parent ceria framework than on catalysts prepared by coprecipitation and microemulsion, which promotes the creation of more oxygen vacancies.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Reactivity and reaction intermediates for acetic acid adsorbed on
           CeO2(111)
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Florencia C. Calaza , Tsung-Liang Chen , David R. Mullins , Ye Xu , Steven H. Overbury
      Adsorption and reaction of acetic acid on a CeO2(111) surface was studied by a combination of ultra-high vacuum based methods including temperature desorption spectroscopy (TPD), soft X-ray photoelectron spectroscopy (sXPS), near edge X-ray absorption spectroscopy (NEXAFS) and reflection absorption IR spectroscopy (RAIRS), together with density functional theory (DFT) calculations. TPD shows that the desorption products are strongly dependent upon the initial oxidation state of the CeO2 surface, including selectivity between acetone and acetaldehyde products. The combination of sXPS and NEXAFS demonstrate that acetate forms upon adsorption at low temperature and is stable to above 500K, above which point ketene, acetone and acetic acid desorb. DFT and RAIRS show that below 500K, bridge bonded acetate coexists with a moiety formed by adsorption of an acetate at an oxygen vacancy, formed by water desorption.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Influence of isovalent and aliovalent dopants on the reactivity of cerium
           oxide for catalytic applications
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): T. Vinodkumar , Bolla Govinda Rao , Benjaram M. Reddy
      The influence of dopant size and valence state on the reduction properties, oxygen defects, and lattice strain in doped ceria has been studied fastidiously. This is of particular importance in environmental application, such as soot and CO oxidation. Herein, isovalent (Zr4+) and aliovalent (La3+, Eu3+, and Sm3+) metal ions doped ceria catalysts were synthesized by coprecipitation method with aqueous ammonia as the precipitant. The interplay of dopant size and valence in the ceria lattice is experimentally analysed in detail at the structural and electronic level by XRD, BET, TEM, Raman, TPR, and XPS techniques, and finally evaluated for soot and CO oxidation reactions. According to the analysis results, the size or the valence of the dopant or both together positively influence the ceria properties. The isovalent substituent (Zr4+), which is different in size with respect to ceria, enhanced the ceria intrinsic activity by decreasing its reduction temperature and oxygen vacancy formation energy, thereby increased the activity. Whereas, aliovalent dopants (La3+, Eu3+, and Sm3+) having different in size and valence compared to pure ceria further improved the structural and catalytic properties of bare ceria by inducing additional oxygen vacancies. The observed activity of doped materials towards soot and CO oxidation reactions is as follows: aliovalent doped ceria>isovalent doped ceria>ceria. The marked influence of isovalent and aliovalent dopants on the ceria properties are highlighted in this study.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Noble metal ion substituted CeO2 catalysts: Electronic interaction between
           noble metal ions and CeO2 lattice
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): M.S. Hegde , Parthasarathi Bera
      In last 40 years, CeO2 has been found to play a major role in the area of auto exhaust catalysis due to its unique redox properties. Catalytic activity is enhanced when CeO2 is added to the noble metals supported Al2O3 catalysts. Reason for increase in catalytic activity is due to higher dispersion of noble metals in the form of ions in CeO2. This has led to the idea of substitution of noble metal ions in CeO2 lattice acting as adsorption sites instead of nanocrystalline noble metal particles on CeO2. In this article, a brief review of synthesis, structure and catalytic properties of noble metal ions dispersed on CeO2 resulting in noble metal ionic catalysts (NMIC) like Ce1−x M x O2−δ , Ce1−x−y Ti x M y O2−δ , Ce1−x−y Zr x M y O2−δ , Ce1−x−y Sn x M y O2−δ and Ce1−x−y Fe x M y O2−δ (M=Pt, Pd, Rh and Ru) are presented. Substitution of Ti, Zr, Sn and Fe in CeO2 increases oxygen storage capacities (OSC) due to structural distortion, whereas dispersion of noble metal ions in Ti, Zr, Sn and Fe substituted CeO2 supports increase both OSC and catalytic activities. Electronic interaction between noble metal ions and CeO2 in NMICs responsible for higher OSC and higher catalytic activities is discussed.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Local structure in CeO2 and CeO2–ZrO2 nanoparticles probed by Eu
           luminescence
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Vasile I. Parvulescu , Carmen Tiseanu
      We report on the local structure properties of trivalent lanthanide-doped CeO2 based nanoparticles by using Eu luminescence as a structural probe. To this aim, we investigate Eu doped CeO2 and CeO2–ZrO2 (Ce/Zr=1) by use of site-selective time-resolved luminescence spectroscopy, in situ/ex situ X-ray diffraction (XRD) and in situ/ex situ Raman spectroscopy. The CeO2 nanoparticles were synthesized by oil in water microemulsion as well as citric acid method and investigated in the as-synthesized state or after calcination in air at 500, 750 and 1000°C. For the as-synthesized Eu–CeO2 nanoparticles by oil-in-water microemusion method, the analysis of the emission/excitation spectra and emission decays of Eu suggest that only surface doping was achieved. In general, the emission of Eu in CeO2 indicates the co-existence of two main Eu centers differentiated by the mode of interaction with the oxygen vacancy. The addition of 10% Eu via wet impregnation onto pre-formed CeO2–ZrO2 followed by calcination induces a remarkable homogenous solid solution of pseudo-cubic phase. The analysis of in situ XRD, in situ Raman and in situ luminescence data evidences for the defect reconfiguration in Eu doped CeO2 during the heating/cooling cycles (30–500 at 30°C). Finally, it is suggested that the structural data inferred from luminescence complements significantly the structural information indicated by X-ray diffraction and Raman spectroscopy, such as the phase content and homogeneity and the presence of defects.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Preface
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): M. Olga Guerrero-Pérez , José Rodríguez-Mirasol , Tomás Cordero



      PubDate: 2015-06-24T06:56:26Z
       
  • Role of surface vanadium oxide coverage support on titania for the
           simultaneous removal of o-dichlorobenzene and NOx from waste incinerator
           flue gas
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): M. Gallastegi-Villa , A. Aranzabal , Z. Boukha , J.A. González-Marcos , J.R. González-Velasco , M.V. Martínez-Huerta , M.A. Bañares
      The catalytic activity of VO x species supported on TiO2 was investigated in the simultaneous destruction of NO and 1,2-dichlorobenzene (o-DCB), as typical pollutants molecules in the off-gases from municipal waste incinerator (MWI) plants. Catalysts with different vanadium loading were prepared in order to obtain different VO x species and characterized by ICP-AES, XPS, N2 adsorption at −196°C, XRD, H2-TPR, Raman and UV–vis–NIR DRS spectroscopy. The characterization results show that molecularly dispersed isolated and polymeric vanadia species form below the dispersion limit loading (“monolayer coverage”), while crystalline species form above it. We used moderate HNO3 treatment to partially leach vanadium oxide species, creating a series of catalysts with variable vanadia loading. The catalytic activity of the VO x /TiO2 catalyst shows that it is able to catalyze the destruction of both pollutants, although higher temperature is required for o-DCB oxidation than for NO reduction. Surface vanadia coverage has a clear effect on TOF and activation energy values, which underline that isolated vanadia species are more efficient for o-DCB oxidation, while the polymeric ones are more efficient for NO reduction.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Re-dispersion of Pd on Ce0.5Zr0.5O2 upon cooling in the presence of oxygen
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Jie Wan , Rui Ran , Xiaodong Wu , Yidan Cao , Min Li , Duan Weng , Kaisheng Huang
      Pd/Ce0.5Zr0.5O2 catalyst was prepared by impregnation method and subjected to different cooling procedures (rapid cooling vs. slow cooling in O2 or in He) after pretreated at 950°C for 30min. The obtained catalysts were characterized by CO chemisorption, transmission electron microscope (TEM), CO temperature-programmed oxidation (CO-TPO), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The results revealed that Pd species on Ce0.5Zr0.5O2 (CZ) suffered severe sintering during high-temperature calcination, but the Pd dispersion increased remarkably after slow cooling in O2. Further investigations ascribed this phenomenon to the Pd re-dispersion process, which needed three essential factors, i.e. sufficient cooling time, oxidizing atmosphere and active support which had strong interaction with Pd species. The re-dispersion process was proved to be mainly due to both the re-oxidization of the sintered Pd particles and the slow migration of the PdO x under the driving of the interaction between Pd and CZ.
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      PubDate: 2015-06-24T06:56:26Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253




      PubDate: 2015-06-24T06:56:26Z
       
  • Contents list
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253




      PubDate: 2015-06-24T06:56:26Z
       
  • Catalysis by ceria
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Paolo Fornasiero , Alessandro Trovarelli



      PubDate: 2015-06-24T06:56:26Z
       
  • Invited Review: Some recent developments in the atomic-scale
           characterization of structural and transport properties of ceria-based
           catalysts and ionic conductors
    • Abstract: Publication date: 15 September 2015
      Source:Catalysis Today, Volume 253
      Author(s): Masatomo Yashima
      Ceria-based materials are utilized as automotive exhaust catalysts for the removal of noxious compounds, as catalysts for reforming ethanol and methane to produce hydrogen in fuel cells, as materials for solar-energy-to-fuel conversion, and as cathode, anode, and electrolyte materials in solid oxide fuel cells (SOFCs). The present paper is a critical review on the atomic-scale characterization of oxide-ion diffusion pathway, the existing phases, the phase transformations, “metastable” and stable phase diagrams, and oxygen storage capacity (OSC) of ceria-based materials. “Metastable,” compositionally (x) homogeneous t′- and t″-ceria–zirconia Ce x Zr1–x O2 solid solutions (0.2< x <0.9) are key materials to obtain a high OSC, leading to high catalytic activity. Here, the t′- and t″-forms are unstable compared to the two-phase mixture of stable ZrO2-rich tetragonal and CeO2-rich cubic (or t″) phases, but are stable in the partitionless, compositionally homogeneous phases. The axial ratio, c/a F where the subscript F represents the pseudo-fluorite lattice, of the t′-form is larger than unity, while the c/a F ratio of the t″-form equals unity. Formation of the t′- and t″-Ce x Zr1–x O2 is depicted in the “metastable” phase diagram consisting of allotropic phase boundaries in the CeO2–ZrO2 system and is explained using the schematic Gibbs energy–composition (G–x) diagram. The composition (CeO2 content x)-induced t′–t″ transition in Ce x Zr1–x O2 is discrete and of first order. The c–t″ phase transition of Ce x Zr1–x O2 is induced by the oxygen displacement from the regular fluorite position 1/4,1/4,1/4 along the c-axis. The c–t″ transition is continuous and might be of higher order. The c–t″ phase boundary at room temperature is located at around x =0.85–0.9 in both bulk and nanocrystalline Ce x Zr1–x O2. The tetragonal symmetry of compositionally homogeneous nano-sized Ce0.5Zr0.5O2 in air is retained up to 1176K. The c/a F ratio, and the oxygen displacement are smaller in the nanocrystalline Ce0.5Zr0.5O2 than in bulk Ce0.5Zr0.5O2. Bulk oxide-ion diffusion is an important step of oxygen storage and release in ceria-based catalysts, and the oxide-ion diffusivity is essential for high OSC and efficiency of the SOFCs and the solar-energy-to-fuel conversion. The present paper reviews the atomic-scale characterization of ion diffusion in ceria-based catalysts and fluorite-type ionic conductors and discusses the correlation between their bulk ion diffusivity and structural properties. The spatial distributions of neutron scattering length density, bond valence sum (BVS), and bond-valence-based energy (BVE) in the unit cell of tetragonal ceria–zirconia compounds, cubic fluorite-type ceria-based materials, and other fluorite-structured compounds such as Ce0.5Zr0.5O2, CeO2, ceria–yttria Ce0.97Y0.07O1.96, bismuth oxide solid solution δ-Bi1.4Yb0.6O3, and copper iodide α-CuI indicate the three-dimensional network of curved 〈100〉F ion diffusion pathways and anisotropic 〈111〉F thermal vibration of mobile ions, which are responsible for the bulk ion diffusion and conduction. Here, the subscript F denotes the pseudo-fluorite lattice. The BVE distributions of Ce0.5Zr0.5O2 and CeO2 indicate lower activation energy and higher mobility of oxide ions in Ce0.5Zr0.5O2 compared with CeO2.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Biofuel steam reforming catalyst for fuel cell application
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): P. Kowalik , K. Antoniak-Jurak , M. Błesznowski , M.C. Herrera , M.A. Larrubia , L.J. Alemany , I.S. Pieta
      Within the ongoing project, related to fuels and energy production from biomass, agricultural and other wastes, the technology based on SOFC stack and steam reforming is under development. The project aims to present an efficient technology for biogas reforming and continuous supply of reformate fuel to the working SOFC stack. The decision, concerning reforming unit and the stack separation, has been made after detailed analysis of advantages and disadvantages of internal reforming. The set of Ni-based catalysts was prepared and investigated for the external biogas steam reforming. To determine the optimal condition of the reforming process the effect of reaction temperature (RT–773K) for steam to carbon (S/C) molar ratio of 2.5 in the feedstock was investigated. Conversions rates and H2/CO ratios in the produced syngas were influenced by the feedstock composition and catalyst used. The increase in the catalyst activity can be attributed to the specific catalyst–promoter interactions such as the redox capacity of V2O5 and its influence on surface Ni-species.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Synthesis, characterisation and photocatalytic activity of N-doped
           TiO2–Nb2O5 mixed oxides
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): A.M. Ferrari-Lima , R.G. Marques , M.L. Gimenes , N.R.C. Fernandes-Machado
      Nitrogen-doped TiO2 and TiO2–Nb2O5 catalysts were prepared by sol–gel technique using titanium isopropoxide (TIP) and potassium niobate. The obtained samples were subsequently calcined at 380 and 500°C. Undoped TiO2 and TiO2–Nb2O5 samples were also prepared by way of comparison. The photocatalytic activities of the synthesised catalysts were evaluated on the photodegradation of benzene, toluene and xylenes (BTX) solution under UVA and visible light. The level of nitrogen incorporated on N-doped TiO2–Nb2O5 catalyst was found to be 0.49 at%. Concentrations of BTX were analysed by gas chromatography applying the headspace technique. The N-doped TiO2–Nb2O5 catalyst calcined at 500°C led to reductions of benzene, toluene and xylenes greater than 65wt% after 150min of irradiation. The photocatalytic reactions followed the first order kinetics.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Esterification processes based on functionalized mesoporous solids
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Maciej Trejda , Beata Pokora , Maria Ziolek
      The abilities of niobium and manganese to enhance oxidation of thiol groups in (3-mercaptopropyl)trimethoxysilane (MPTMS) used for functionalization of SBA-15 and MCF materials, by hydrogen peroxide in order to form catalysts with acidic properties were evaluated. Materials obtained were characterized by: N2 adsorption, XRD, XRF, elemental and thermal analyses and titration of acid sites. The highest concentration of acidic sites was found for SBA-15 structure modified with niobium. The catalytic activities of materials obtained were examined in esterification of acetic acid with ethanol and 2-propanol. Both niobium containing samples (MP-NbSBA-15 and MP-NbMCF) showed high yields of ethyl and 2-propyl acetate. The amount of 2-propyl acetate formed was found to linearly depend on the number of acid sites on the catalyst surface. The reuse tests proved that the drop in the catalyst activity in consecutive catalytic cycles is not too high, which suggests possible application of the materials obtained after further optimization.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Mesostructured cellular foams modified by niobium or tantalum and
           functionalized with (3-mercaptopropyl)trimethoxysilane – Raman
           inspired reduction of synthesis time
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Katarzyna Stawicka , Vanesa Calvino-Casilda , Maciej Trejda , Miguel A. Bañares , Maria Ziolek
      The synthesis of mesostructured cellular foams (MCF) modified by niobium or tantalum source and functionalized with MPTMS (3-mercaptopropyl)trimethoxysilane was monitored in situ by Raman spectroscopy. The results from Raman monitoring prompted us to check for a possibility of shorter time synthesis of mesostructured cellular foams. A series of MCFs materials prepared using different times of gel mixing (5h and standard 20h) were synthesized. The samples obtained were characterized by N2 adsorption/desorption, XRD, TEM, XRF, elemental analysis, UV–Vis, FTIR and amperometric titration. The effects of niobium and tantalum on the rate and efficiency of thiol oxidation as well as on the time of silica formation were explored. The most important outcome of the study is the evidence of the formation of MCFs materials having strong Brønsted acidic centers in a shorter preparation time. SO3H groups form faster than in MP-MCF material in the presence of niobium or tantalum in the synthesis gel. The extension of synthesis time for silica and tantalosilicate samples leads to more efficient oxidation of thiol species. This feature does not depend on the synthesis time of niobiosilicate materials.
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      PubDate: 2015-06-24T06:56:26Z
       
  • Influence of preparation methods and structure of niobium oxide-based
           catalysts in the epoxidation reaction
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Rosa Turco , Antonio Aronne , Paolo Carniti , Antonella Gervasini , Luciana Minieri , Pasquale Pernice , Riccardo Tesser , Rosa Vitiello , Martino Di Serio
      The catalytic activity of niobium oxide-based materials, containing the same amount of Nb2O5 (∼15wt%) and prepared by different methods, with that of pure Nb2O5 in the epoxidation of methyl oleate with hydrogen peroxide was compared. The catalytic performances of the catalyst prepared by impregnation do not differ substantially from the ones of Nb2O5. The performances of Nb-supported catalysts prepared by sol–gel can be modulated by controlling the process parameters. The high dispersion of the active NbO x species obtained by this preparation method gives very higher selectivity than in the case of pure Nb2O5. Morphologic and structural characterization of the catalysts helped justifying the obtained catalytic results in terms of activity and selectivity.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • Amphiphilic property of niobium oxyhydroxide for waste glycerol conversion
           to produce solketal
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Talita E. Souza , Izabela D. Padula , Mariana M.G. Teodoro , Poliane Chagas , Jarbas M. Resende , Patterson P. Souza , Luiz C.A. Oliveira
      Amphiphilic catalysts are synthesized using NbCl5 in the presence of the CTAB (cetyltrimethylammonium bromide) to generate partial hydrophobicity to the catalysts. The partial hydrophobicity of the niobium oxyhydroxides improved the acetalization reaction of a residual glycerol from biodiesel production by decreasing the interaction between the water molecules and the acid sites of the catalyst. A waste glycerol conversion of 73% with a selectivity to solketal (2,2-dimethyl-[1,3]dioxolan-4-yl)methanol of 95% was obtained. Many reuses of the catalysts showed glycerol conversions between 70 and 80%.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • Exploitment of niobium oxide effective acidity for xylose dehydration to
           furfural
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Maria José Campos Molina , Manuel López Granados , Antonella Gervasini , Paolo Carniti
      Xylose together with other pentose and hexose sugars can be dehydrated to produce interesting platform chemical compounds, like 5-hydroxyfurfural (HMF) and furfural. This study continues our investigation on the niobium oxide based catalysts in connection with the research of adequate solvents systems to minimize catalyst deactivation and increase catalyst stability and durability during the dehydration of sugars. Silica-zirconia supported niobia samples (10wt.% of Nb) prepared by impregnation or sol–gel in comparison with pure niobic acid are here presented for xylose dehydration. The reactions have been studied at different temperatures (130–180°C) in batch or fixed bed continuous catalytic reactors in various solvents. Green solvents soluble in the aqueous solution of xylose or biphasic systems have been taken into account: water, water–isopropanol mixtures, water-γ-valerolactone, and water-cyclopentylmethyl ether. The surface acidities of the catalysts have been measured in cyclohexane (intrinsic acidity) and also in water to determine the effective catalyst acidity. The continuous tests and batch-recycling tests showed that the supported Nb-catalysts, even if initially less active, are more stable than niobic acid. The presence of isopropanol in water improves both the activity and stability of the catalysts in comparison with water and the use of cyclopentylmethyl ether gave the most interesting selectivity to furfural preserving the catalyst stability.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • TiO2/SiO2 supported vanadia catalysts for the ODH of propane
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Soumik Chakraborty , Sudhir C. Nayak , Goutam Deo
      Supported vanadia catalysts were prepared on two TiO2/SiO2 supports, which contained 70% and 90% TiO2. The supports were thermally stable up to 1023K and surface vanadia species were formed on them. The supported catalysts were characterized by Raman and FTIR spectroscopy, XRD and TPR. The surface area of the catalysts was also determined. The supported vanadia catalysts were active for the propane oxidative dehydrogenation (ODH) reaction and the most active and selective catalyst contained 6% vanadia, which appeared to be the monolayer limit on these supports. Furthermore, the catalyst formed with 70% TiO2 in the support was more active than the catalyst containing 90% TiO2. The kinetic parameters were determined and were able to explain the variations in conversion at iso-contact time and selectivity at iso-conversion for the different catalysts.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • Au–Cu on Nb2O5 and Nb/MCF supports – Surface properties and
           catalytic activity in glycerol and methanol oxidation
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Izabela Sobczak , Łukasz Wolski
      Nb2O5 and Nb/MCF were used as supports for gold and copper (Au–Cu system). The activity of these catalysts in the oxidation of glycerol in the liquid phase and methanol in the gas phase was compared with that of monometallic gold catalysts. The oxidation states of metals in the samples prepared were characterised by XRD, TEM, UV–Vis, XPS and H2-TPR. It was found that gold was present in metallic form, whereas copper in the form of CuO, oligonuclear [Cu δ+⋯O δ−⋯Cu δ+] n clusters and isolated cations. The introduction of copper changed the electronic state of gold in Au–Nb2O5 and Au–Nb/MCF and the reduction of copper was found easier in bimetallic AuCu catalysts, which was interpreted as a result of the interaction between gold and copper. Nb2O5 supported catalysts were active in the glycerol oxidation. Monometallic catalysts show high selectivity to glyceric acid, whereas an increase in the selectivity to glycolic acid was found over bimetallic samples due to the presence of copper species active in the oxidative dehydrogenation of glyceric acid. Au–Cu catalysts exhibit very high activity in methanol oxidation towards CO2 as a result of the presence of basic oxygen from CuO-like species on the catalyst surface. Superior performance of bimetallic catalysts in oxidation reactions is due to the synergy between gold and copper.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • A first-principles modeling of glycerol and ammonia interactions on the
           cation-deficient VSbO4(110) surface
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): Ignacio M. Alliati , Beatriz L. Irigoyen
      Glycerol, a major by-product of biodiesel production, is usually involved in reactions of low selectivity. Recently, it has been reported that new reaction of glycerol ammoxidation on vanadium antimonate led to very promising results in terms of conversion and selectivity to acrylonitrile, a valuable monomer for the chemical industry. Therefore, in this work we performed theoretical calculations based on the density functional theory (DFT), in order to study glycerol and ammonia interactions on the cation-deficient VSbO4(110) surface. Our results show that glycerol and ammonia interactions on Brønsted acid sites are rather weak, reaching adsorption energy values of −0.72eV and −0.67eV, respectively. However, the interactions of those molecules on Lewis acid sites are more favorable. Glycerol adsorption mainly involves V sites (−2.83eV); while the most stable interaction of ammonia (−2.08eV) leads to a new NSb bond, suggesting the participation of Sb sites in CN bonds formation.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • V and V–P containing Zr-SBA-15 catalysts for dehydration of glycerol
           to acrolein
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): J.A. Cecilia , C. García-Sancho , J.M. Mérida-Robles , J. Santamaría-González , R. Moreno-Tost , P. Maireles-Torres
      A series of solid acid catalysts based on vanadium and vanadium–phosphorous supported on a zirconium doped mesoporous SBA-15 silica has been synthesized, characterized by using XRD, N2 sorption, NH3–TPD, FT-IR spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance UV–vis spectroscopy, and evaluated in the gas-phase dehydration of glycerol. Under the operating conditions used, all materials are active in the glycerol dehydration, being acrolein the main product in all cases. Although higher values of conversion are obtained in the presence of vanadium oxide based catalysts, acrolein yield improves after the treatment with phosphoric acid, attaining a value of 42% after 2h of reaction at 325°C with the 12VP0.2 catalyst, which contains 12wt.% of V2O5 and a V/P molar ratio of 0.2. However, the incorporation of phosphorous to the catalytic system partially destroys the mesoporous structure. Allyl alcohol has been also detected using vanadium based catalysts, due to a partial reduction of V2O5 species during the reaction, increasing its yield with the vanadium oxide loading. All catalysts suffer from deactivation by coke deposition on the catalyst surface, being the carbon content considerably higher for catalysts without phosphorous.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • Vanadium oxide supported on porous clay heterostructure for the partial
           oxidation of hydrogen sulphide to sulfur
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): M.D. Soriano , J.A. Cecilia , A. Natoli , J. Jiménez-Jiménez , J.M. López Nieto , E. Rodríguez-Castellón
      Vanadium oxide supported on porous clay heterostructures (PCH) catalysts have been synthesized, characterized and evaluated in the selective oxidation of H2S to elemental sulfur. The catalysts were characterized by XRD, adsorption–desorption of N2 at −196°C, diffuse reflectance UV–vis, H2-TPR, Raman spectroscopy and XPS. The catalysts with higher vanadium content are more active and selective, exhibiting a H2S conversion close to 70% after 360h on stream with a high selectivity toward elemental sulfur and a low formation of undesired SO2. The catalysts with V2O5 crystallites have shown a higher activity and resistance to the deactivation. The analysis of the spent catalyst has revealed the formation of V4O9 crystals during the catalytic test, which has been reported as the active phase in the selective oxidation of the H2S.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • Mesostructured vanadia–alumina catalysts for the synthesis of
           vitamin K3
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254
      Author(s): M. Florea , R.S. Marin , F.M. Pălăşanu , F. Neaţu , V.I. Pârvulescu
      Liquid-phase selective oxidation of 2-methylnaphtalene to the vitamin K3 was investigated on a series of mesostructured vanadia–alumina catalysts with different V/Al ratios (0.1–1). They were prepared by the co-precipitation of ammonium metavanadate and aluminum nitrate at pH 5 and characterized by XRD, Raman, TG–DTA, elemental analysis and adsorption-desorption isotherms of nitrogen at −196°C. The influence of the catalyst composition and calcination temperature upon the physico-chemical properties were closely investigated in relation with the catalytic performances. The result of this investigation indicated the catalysts containing a higher vanadium loading and calcined at 300°C as the most active. Thus, the VAl07 catalyst led to a selectivity in vitamin K3 of 54% for a conversion of 2-methylnaphtalene of 76%. Such an activity corresponded to mixtures where metavanadate (Raman line at 940cm−1) and decavanadate (Raman line at 990cm−1) species were the most abundant. No lines of V2O5 (around 705cm−1) were detected in the catalysts calcined below 600°C.
      Graphical abstract image

      PubDate: 2015-06-24T06:56:26Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254




      PubDate: 2015-06-24T06:56:26Z
       
  • Contents list
    • Abstract: Publication date: 1 October 2015
      Source:Catalysis Today, Volume 254




      PubDate: 2015-06-24T06:56:26Z
       
 
 
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