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  Subjects -> ENGINEERING (Total: 2270 journals)
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ENGINEERING (1199 journals)                  1 2 3 4 5 6 | Last

Showing 1 - 200 of 1205 Journals sorted alphabetically
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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  [3031 journals]
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289


      PubDate: 2017-05-16T20:10:21Z
       
  • Contents list
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289


      PubDate: 2017-05-16T20:10:21Z
       
  • Editorial
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Victor Teixeira da Silva, Maria do Carmo Rangel, Sibele Pergher


      PubDate: 2017-05-16T20:10:21Z
       
  • Synthesis and properties of MCM-41 with polymerizable CADMA cationic
           surfactant
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Laura L. Silva, Isabella P. Alkimim, Pablo A.S. Vasquez, Dilson Cardoso
      The synthesis route of MCM-41 was modified by using a cationic surfactant different from the usual CTMABr (cetyltrimethylammonium bromide). This surfactant, cetylallyldimethylammonium bromide (CADMABr), differs from CTMABr by the substitution of a methyl group located in the hydrophilic head by a polymerizable allyl group. The CADMABr surfactant and the CADMA-MCM-41 hybrid silica were synthesized using different times. Formation of the surfactant was confirmed using elemental analysis (CHN), 13C nuclear magnetic resonance (13C NMR), and small-angle X-ray scattering (SAXS) applied to the dispersions of different concentrations of the surfactants in water. The aqueous dispersions of CADMABr and the hybrid silicas were irradiated at different doses of gamma (γ) radiation in order to obtain information about the polymerization of the surfactant. The hybrid silicas were characterized using X-ray diffraction (XRD) for phase identification, together with thermogravimetry (TGA), nitrogen physisorption, and scanning electron microscopy (SEM). The catalytic properties of the silicas were evaluated using the transesterification reaction of monoalcohols as a model for application in biodiesel manufacture.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Coupling of monoterpenic alkenes and alcohols with benzaldehyde catalyzed
           by silica-supported tungstophosphoric heteropoly acid
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Rafaela F. Cotta, Kelly A. da Silva Rocha, Elena F. Kozhevnikova, Ivan V. Kozhevnikov, Elena V. Gusevskaya
      The reactions of biomass-based substrates, i.e., limonene, α-pinene, β-pinene, terpinolene, α-terpineol, nerol and linalool, with benzaldehyde in the presence of tungstophosphoric heteropoly acid H3PW12O40 (HPW) supported on silica give an oxabicyclo[3.3.1]nonene compound with fragrance characteristics in good to excellent yields. The reactions apparently involve the formation of α-terpenyl carbenium ion by the protonation of alkene or dehydration of alcohol followed by the nucleophilic attack of benzaldehyde. The subsequent oxonium-ene cyclization of the resulting oxocarbenium ion gives the oxabicyclic product. The process is an environmentally benign and heterogeneous and can be performed under mild conditions with low catalyst amounts and no significant leaching of active components.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • The multiple benefits of glycerol conversion to acrolein and acrylic acid
           catalyzed by vanadium oxides supported on micro-mesoporous MFI zeolites
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Luiz G. Possato, Thiago F. Chaves, Wellington H. Cassinelli, Sandra H. Pulcinelli, Celso V. Santilli, Leandro Martins
      The ZSM-5 zeolite (MFI structure, Si/Al=40) was treated using NaOH and either oxalic acid or HCl to obtain hierarchical materials with different characteristics, followed by impregnation with vanadium oxides (V2O5) to generate redox-active sites. The impact of the multiple treatments on the efficiency and stability of the catalysts in the conversion of glycerol to acrolein and acrylic acid was investigated and correlated with catalyst porosity, acidity, and chemical composition. The treated and impregnated V2O5 catalysts were subjected to XRD, 27Al NMR, nitrogen physisorption, TPD-NH3, TG, and UV–Vis analyses, in order to associate the properties of the catalysts with their activities. The studies showed that the catalytic performance of the materials depended on the acidic and textural properties of the zeolites, which influenced both the dispersion of V2O5 and its interaction with the acid sites of the supporting zeolites. All the catalysts provided conversion values exceeding 65%, even after 6h on glycerol stream. The distribution of products strongly reflected the effects of pore formation, acid treatment with oxalic acid or HCl, and the presence of vanadium oxide. The effects of these modifications resulted in higher selectivity to acrolein and acrylic acid, a reduced rate of coke accumulation in the zeolite, and a longer catalyst lifetime.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Kinetic study of the ethyl lactate synthesis from triose sugars on
           Sn/Al2O3 catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): E. Pighin, V.K. Díez, J.I. Di Cosimo
      The reaction kinetics of the liquid-phase synthesis of ethyl lactate from dihydroxyacetone and ethanol was studied on Sn-promoted alumina catalysts. Yields of ≈70% were obtained at 353K after 7h of reaction. The effect of the catalyst Sn loading (1–8wt.%) and reaction temperature (343–373K) on the reaction kinetics was investigated. The reaction is promoted by Lewis acid sites provided by surface Sn species. A kinetic model based on a pseudohomogeneous mechanism was postulated to describe the reaction network comprising a sequence of consecutive and parallel reaction steps. The kinetic rate constant associated to ethyl lactate formation increases with the number of Lewis acid sites confirming that surface Sn species participate in the kinetically relevant reaction steps. Catalysts were prepared by impregnation and characterized by N2 physisorption, X-ray diffraction, UV-vis-DRS, FTIR of pyridine and TPD of NH3.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Gas phase glycerol oxidative dehydration over bifunctional V/H-zeolite
           catalysts with different zeolite topologies
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Thamyris Q. Silva, Maurício B. dos Santos, Alex A.C. Santiago, Danilo O. Santana, Fernanda T. Cruz, Heloysa M.C. Andrade, Artur J.S. Mascarenhas
      The oxidative dehydration of glycerol to acrylic acid can be performed in one single step using bifunctional catalysts containing both acid and redox sites. In this sense, zeolites containing transition metals are promising catalysts. Zeolites of different topologies: FAU, FER, MEL, MFI, MOR, MWW and OFF were synthesized and further impregnated with 5% vanadium. The catalysts were characterized and evaluated in the gas phase glycerol oxidative dehydration. All catalysts showed high conversions of glycerol (100-78%). The acrolein selectivity decreases with the total density of acid sites in these zeolites. The selectivity to acrylic acid is related to the ability of each topology of stabilizing the redox pair V5+/V4+. The best performances were observed for zeolite catalysts with MWW, BEA and MFI topologies.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Highly active Pt/MoC and Pt/TiC catalysts for the low-temperature
           water-gas shift reaction: Effects of the carbide metal/carbon ratio on the
           catalyst performance
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): José A. Rodriguez, Pedro J. Ramírez, Ramón A. Gutierrez
      Pt/MoC and Pt/TiC(001) are excellent catalysts for the low-temperature water-gas shift (WGS, CO+H2O→H2 +CO2) reaction. They exhibit high-activity, stability and selectivity. The highest catalytic activities are seen for small coverages of Pt on the carbide substrates. Synergistic effects at the metal-carbide interface produce an enhancement in chemical activity with respect to pure Pt, MoC and TiC. A clear correlation is found between the ability of the Pt/MoC and Pt/TiC(001) surfaces to partially dissociate water and their catalytic activity for the WGS reaction. An overall comparison of the results for Pt/MoC and Pt/Mo2C(001) indicates that the metal/carbon ratio in the carbide support can have a strong influence in the stability and selectivity of WGS catalysts and is a parameter that must be taken into consideration when designing these systems.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Influence of the metallic content on Pt-Ir/Nb2O5 catalysts for decalin
           selective ring opening
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Viviana M. Benitez, Simone P. de Lima, Maria do Carmo Rangel, Doris Ruiz, Patricio Reyes, Carlos L. Pieck
      Ring opening of naphthenic rings on Pt-Ir catalysts supported on Nb2O5 was studied in this work. The catalysts were prepared by impregnation. In the case of the bimetallic catalyst, the total metallic load was kept constant while varying the individual quantity of impregnated Ir and Pt. The samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 sorption, NH3 TPD and model reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis). The decalin ring opening capacity of the catalysts was evaluated. Monometallic Ir and Pt catalysts as well as bimetallic catalysts were active towards cyclohexane dehydrogenation and cyclopentane hydrogenolysis. Regarding the bimetallic catalysts, an increase on the Pt content promoted the cyclohexane dehydrogenation while hindering the hydrogenolytic activity. In the selective ring opening of decalin, the bimetallic catalysts presented activities comparable to the monometallic catalysts. Nonetheless, Ir(0.3%)/Nb2O5 catalyst presented the highest selectivity towards ring opening products with the lowest selectivity towards dehydrogenated products.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Effect of the metal promoter on the performances of H-ZSM5 in ethylene
           aromatization
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Hadrien Coqueblin, Anthony Richard, Denis Uzio, Ludovic Pinard, Yannick Pouilloux, Florence Epron
      The effect of the metal and the zeolite on the physicochemical properties and catalytic performances in ethylene aromatization was investigated on M/H-ZSM5 (M=Ni, Mo, Zn and Ga). The addition of the metal to the zeolite increases the amount of Lewis acid sites and in parallel decreased the amount of Brønsted ones. The extent of the change depended mainly on the location and dispersion of the metal cation, which varied not only with the nature of the metal but also with the one of the metal precursor. The higher Lewis acidity associated with the lowest Brønsted acidity was obtained with the Zn/H-ZSM5 catalyst. Ethylene aromatization was studied at 500°C and atmospheric pressure. For the catalyst series, it was demonstrated that the ethylene conversion and yield in aromatic products were proportional to the number of Lewis acid sites, except for Ni/H-ZSM5 that presented a singular behavior with a high initial conversion but rapid deactivation, due to carbon formation. Among the other catalysts, Zn/H-ZSM5 led to the highest ethylene conversion and yield in aromatics. An increase in Zn content increased the amount of Lewis acid sites, decreased the amount of Brønsted acid sites, which favored the initial catalytic performances but also decreased the stability of the Zn/H-ZSM5 catalyst.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Generation and characterization of catalytically active sites of
           heteropolyacids on zeolite Y for liquid-phase esterification
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Elon F. Freitas, Mateus F. Paiva, Sílvia C.L. Dias, José A. Dias
      Zeolites and polyoxometalates are catalysts used in important environmental processes and their combination produces a new solid tailoring the advantages of both catalysts. In this work, supported H3PW12O40 or H4SiW12O40 on zeolite Y was prepared by incipient and aqueous impregnation, which maintained the Keggin structure. The dispersion of H3PW12O40 or H4SiW12O40 on zeolite Y surface lead to nanocrystals of 5nm and 23nm, respectively. Although the crystallinity decreased with HPA loading, the SEM images showed that the original morphology of zeolite Y was conserved and a strong interaction between the solids could be inferred from the MAS NMR spectra. Enhanced formation of secondary mesopores on the zeolite Y structure was related to the partial dealumination process that took place during the impregnation. Heteropolyacid impregnation on zeolite Y resulted on the disappearance of the Lewis sites, because of the interaction with the Keggin anion, thus causing the solid to have predominantly Brønsted type sites. The new sites kept the strengths higher than −100kJmol−1 with a generally increased number because the individual solids had about the same strength of sites (−147kJmol−1). Higher conversion (77%) for esterification reaction was observed for the samples prepared by incipient impregnation.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Hydrotalcites derived catalysts for syngas production from biogas
           reforming: Effect of nickel and cerium load
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Ananda Vallezi Paladino Lino, Elisabete Moreira Assaf, José Mansur Assaf
      Mixed oxide catalysts derived from hydrotalcites were applied to model biogas reforming (CH4:CO4 =1.5:1). Nix/MgAl and Nix/MgAlCe (x=10% or 25% w/w nominal nickel content) were prepared by the coprecipitation method. Both Ni10%/MgAl and Ni10%/MgAlCe catalysts showed potential for syngas production due to their stability. CO2-TPD measurements and XANES results helped understand the Ni10%/MgAl and Ni10%/MgAlCe catalysts performance be similar. XANES spectra suggested that the majority of Ni+2 would be present inside the solid solution in Ni10%/MgAlCe, making the activation process more difficult, which probably compromised the conversions enhancement in relation to Ni10%/MgAl. The H2/CO ratio lower than unity makes the obtained syngas suitable for the Fischer-Tropsch process. The carbon deposits on Ni10%/MgAlCe catalyst were less stable, which means that it could be gasified more easily.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Red mud based gold catalysts in the oxidation of benzyl alcohol with
           molecular oxygen
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Aline A.S. Oliveira, Demétrio S. Costa, Ivo F. Teixeira, Luciana A. Parreira, Luciano Menini, Elena V. Gusevskaya, Flávia C.C. Moura
      Red Mud (RM) based gold catalysts were prepared by supporting gold nanoparticles (AuNPs) on the RM residue reduced either with H2 or with ethanol – which promoted partial coating of the RM with carbon. The materials were characterized by X-ray diffraction, Mössbauer spectroscopy, elemental analysis CHN, transmission electron microscopy and EDS microanalysis. Their catalytic performance was evaluated in the liquid-phase oxidation of benzyl alcohol by molecular oxygen, for the first time, as far as we know. The results showed that AuNPs with diameters of around 10nm were successfully supported and distributed on the surface of red mud based materials. Furthermore, carbon coating allowed better incorporation of AuNPs on the material surface and better dispersion of the material into the reaction solutions. AuNPs supported on RM reduced in ethanol and, therefore, coated with carbon showed better catalytic performance than AuNPs supported on MR reduced in hydrogen.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Renewable hydrogen from glycerol reforming over nickel aluminate-based
           catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Daiane F.P. Suffredini, Vivian V. Thyssen, Poliana M.M. de Almeida, Ruan S. Gomes, Moisés C. Borges, Andréa M. Duarte de Farias, Elisabete M. Assaf, Marco A. Fraga, Soraia T. Brandão
      Nickel aluminate (NiAl2O4) was synthesized by citrate method and used as a precursor for supported Ni catalysts. This bulk sample as well as an alumina-supported NiAl2O4 and a dual catalytic system obtained by its simple and straightforward physical mixture with alumina were investigated on glycerol reforming at different water:glycerol molar ratio conditions. All catalyst precursors and the reduced catalysts made thereof were characterized by XRF, porosity, H2-TPR, powder XRD and temperature-resolved XRD. Spent catalysts were complementarily analyzed by TPO/TGA-MS and FE-SEM in order to infer on deactivation process. NiAl2O4 precursor structure rendered highly active systems accomplishing a level of glycerol conversion to gaseous products roughly equivalent to glycerol global conversion. Therefore, hydrogen and CO2 were the main products obtained, reaching hydrogen yields usually higher than 80% with respect to the theoretical maximum production. The way NiAl2O4 phase is settled in catalyst formulation (bulk, supported or physically mixed) revealed an important influence on catalyst deactivation. Deactivation was associated with the formation of carbon filaments as no other type of carbon species, more or less reactive, could be identified.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Biodiesel production from Jatropha curcas L. oil by simultaneous
           esterification and transesterification using sulphated zirconia
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Rodrigo Zunta Raia, Lidiane Sabino da Silva, Silvio Miguel Parmegiani Marcucci, Pedro Augusto Arroyo
      Ethyl esters were synthesized by simultaneous esterification and transesterification reactions, using Jatropha curcas L. oil as raw material and sulphated zirconia (SZ) as catalyst. SZ catalysts were synthesized by the precipitation method, and the final pH of each precipitation was 6, 7 and 8 (SZ6, SZ7 and SZ8, respectively). X-ray diffraction showed the presence and intensity of a tetragonal crystal phase, which was associated with acidity and activity of the catalysts. In addition, the BET surface area was directly proportional to the pH of precipitation. During the catalytic tests it was observed that the most acidic sample (SZ8) had the highest catalytic activity for simultaneous esterification and transesterification, resulting in a 59.4% yield of ethyl esters. Furthermore, the catalyst had activity for separate esterification and transesterification reactions, and both were influenced by the mechanism of the simultaneous reactions. It could also be seen that, in reactions at different acidity levels, free fatty acids influenced the reaction mechanism, such that for high acid contents (14.29%), higher ethyl ester yields and faster reaction rates were obtained compared with lower acid contents (2.39%).
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      PubDate: 2017-05-16T20:10:21Z
       
  • Effect of imidazolium ionic liquids anions on copolymerization of CO2 with
           cyclohexene oxide by CrIII(Salen)Cl
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Edson Comin, Roberto F. de Souza, Katia Bernardo-Gusmão
      The copolymerization of carbon dioxide and cyclohexene oxide was investigated without using solvent in the presence of ionic liquids based on 1-butyl-3-methylimidazolium with anions Cl− (BMI.Cl) and BF4 − (BMI.BF4) were used as cocatalyst. The catalyst used was chloro (1R,2R)-(−)-[1,2-cyclohexanediamine-N,N‘-bis(3,5-di-tert-butylsalicilidene)] chromium (III) [(Cr(Salen)Cl)]. Parameters like molar ratio catalyst/cocatalyst, pressure of CO2 and the nature of cocatalyst were evaluated. The imidazolium ionic liquids were effective as cocatalyst. The BMI.Cl provided better results than when used BMI.BF4. Poly(cyclohexene carbonate) PCHC with high carbonate units (98%) and lower polydispersity (1.4) was obtained under pressure of 30bar of carbon dioxide and using 10 equivalents of BMI.Cl.
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      PubDate: 2017-05-16T20:10:21Z
       
  • New mechanistic approaches for fatty acid methyl ester production
           reactions in the presence of Sn(IV) catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Rafael S. Nunes, Felyppe M. Altino, Mario R. Meneghetti, Simoni M.P. Meneghetti
      Tin complexes (BuSnCl3 and Bu2SnCl2) were investigated as catalysts for the methanolysis of soybean oil and the esterification of oleic acid with methanol under several reaction conditions. From this study, it is possible to determine that BuSnCl3 was the most active catalyst for both reactions. Studies using 1H NMR confirm this trend, and the reactions attained yields of 89 and 6% by transesterification, and 100 and 82% by esterification when BuSnCl3 and Bu2SnCl2 were used as catalysts, respectively. The results obtained by 119Sn NMR show that during transesterification or esterification, no significant change in the substituents on Sn was detected for either catalyst, and consequently, both catalysts should act as net Lewis acids. Furthermore, computational studies have rationalized the higher activity exhibited by BuSnCl3 in comparison with Bu2SnCl2 because no HCl release occurred through the protonolysis of the chloro-substituent, as shown by 119Sn NMR studies.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Alcoxycle: A novel route for glycerol reform into H2 and COx in separate
           stages
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Fabiano Gomes Ferreira de Paula, Marcelo Gonçalves Rosmaninho, Ana Paula de Carvalho Teixeira, Patterson Patrício de Souza, Rochel Montero Lago
      In this paper, it is proposed a new route, named “Alkoxycle”, for the conversion of glycerol from biodiesel production into H2 and CO/CO2 in different and separate stages. In this process, glycerol first reacts with NaOH to form an alkoxide that, in a second step, undergoes controlled thermal decomposition. Analyses of glycerol:NaOH precursor mixtures (molar ratios of 1:1, 1:2, 1:3 and 1:5) by TG, XRD, SEM, TEM, Raman, total carbon and GC–MS showed that the decomposition of the alkoxide at 400°C leads to the formation of three fractions: liquid, gas and solid. The liquid products were formed only in very small amounts whereas an important gas fraction (12–16wt%) was produced consisting mainly of H2 (95% selectivity). In the second stage, the solid products (70–86wt%) consisting of Na2O, carbon and mostly Na2CO3 can be decompose by heating at 700°C to procuce CO2 and especially CO. At the end of the Alcoxycle process, the NaOH used in the reaction and also the NaOH present in the biodiesel glycerol can be recovered and reused.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Effect of composition and thermal treatment in catalysts derived from
           Cu-Al hydrotalcites-like compounds in the NO reduction by CO
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Carla Levi Oliveira Corrêa, Yordy E. Licea, Luz Amparo Palacio, Fatima Maria Zanon Zotin
      In order to minimize the emission of pollutants in the atmosphere copper-based catalysts were studied. This is a cheaper alternative to traditional catalysts, which use noble metals. Catalysts for the NO by CO reduction reaction have been synthesized from Cu-Al type hydrotalcite with different compositions. The influence of thermal treatment at high temperatures, and the atmosphere of the pretreatment before catalytic tests, were also investigated. The characterization by chemical analysis, X-ray diffraction and thermal analysis indicated that pure hydrotalcite was obtained in the precursor with low Al/(Al+Cu) ratio, and that the catalysts were composed of mainly crystalline CuO and amorphous aluminum compounds. Temperature programmed reduction and in-situ XANES showed that some species of Cu+ are present in the catalyst with 50:50 Cu:Al. After thermal treatments, CuO and copper aluminate were formed. All catalysts showed a very good performance, with conversion of 100% in most of them. The catalyst with the least N2O yield was the 50:50 Cu:Al. The corresponding precursor (50:50 Cu:Al) treated at 900°C for 12h improved clearly the activity, and when it was in-situ reduced (before catalytic test) it was most active in comparison to the other catalysts that were evaluated.
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      PubDate: 2017-05-16T20:10:21Z
       
  • New molybdenum-based catalysts for dry reforming of methane in presence of
           sulfur: A promising way for biogas valorization
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Marine Gaillard, Mirella Virginie, Andrei Y. Khodakov
      Mo-based catalysts supported on γ-Al2O3 were synthesized by an incipient wetness impregnation method. They have been tested in the methane dry reforming reaction in a fixed-bed reactor at temperatures from 650 to 800°C. Additional tests have been carried out in presence of 50ppm of H2S to verify their stability towards sulfur poisoning. The influence of Mo loading and Ni promotion on the catalyst activity, stability, and coke deposition were investigated. The fresh and spent catalysts were characterized using N2 physisorption, X-ray Diffraction, Temperature Programmed Reduction and Thermogravimetric Analysis. Carbon deposition was the major reason of deactivation of the molybdenum catalysts, while nickel catalysts rapidly lost their activity in the presence of sulfur. The optimized nickel-promoted molybdenum catalysts exhibit a synergetic effect conferring to them better reducibility, smaller carbon deposition and better stability in presence of sulfur.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Selective hydrogenation of 1,3-butadiene in the presence of 1-butene under
           liquid phase conditions using structured catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Franklin J. Méndez, Oihane Sanz, Mario Montes, Julia Guerra, Claudio Olivera-Fuentes, Susana Curbelo, Joaquín L. Brito
      Different aluminium structured substrates (monoliths of 350 and 1100cpsi; foams of 10, 20 and 40ppi) have been loaded with NiPd/(CeO2-Al2O3) catalyst by washcoating. To improve the adherence between catalyst particles and metallic surface, aluminium substrates were previously anodized to produce a rough (cracked) surface. Catalytic layers of different thickness have been deposited onto aluminium substrates. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the selective hydrogenation of 1,3-butadiene in presence of 1-butene under liquid-phase conditions. The effects of some design parameters over the catalytic performance were studied: catalyst loading (125, 250 or 500mg), geometry of the structured substrate (monoliths or foams), and porosity (cpsi or ppi). The catalytic results show that foams present better activity than the monoliths. This can be related to better mass and heat transfer in the case of foams. In addition, the catalytic coating thickness influence directly the reaction selectivity; thicker layers produce undesired products (BA and isomers) due to diffusion limitations. However, it seems that the mass transfer of reactants to the surface of the catalyst layer plays a major role than the diffusion of reactants inside the catalyst layer.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Chemical pathways in the partial oxidation and steam reforming of acetic
           acid over a Rh-Al2O3 catalyst
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Roberto Batista da Silva, Soraia Teixeira Brandão, Andrea Lucotti, Matteo Saverio Tommasini, Chiara Castiglioni, Gianpiero Groppi, Alessandra Beretta
      The catalytic partial oxidation (CPO) and the steam reforming (SR) of acetic acid (HAc) over a 2wt% Rh/α-Al2O3 were investigated in an isothermal annular reactor. The experiments were performed at GHSV values up to 2.0×106 l(NTP)/kgcat/h by feeding highly diluted HAc/O2 and HAc/H2O mixtures; temperature was varied from 200 to 850°C. In analogy with the CPO of hydrocarbons, also the CPO of HAc showed a low temperature regime characterized by the oxidation of the acid, while the production of synthesis gas occurred above 450°C. Deep oxidation was observed below 300°C. In between 300 and 450°C, a progressive decline of O2 conversion was observed (a very unique feature), accompanied by decrease of CO2 production and formation of CO with traces of H2. C-accumulation was observed starting from 400°C. The data suggest that an increasing fraction of the surface sites was active in an oxygen-lean chemistry. This could be explained by assuming that competitive adsorption displaced oxygen in favor of acetic acid. Dedicated SR tests confirmed that the production of CO and H2 became significant only above 450–500°C, while the process was hindered, likely by C-poisoning, at lower temperatures. Raman measurements confirmed that at the intermediate temperatures (450°C) the surface was enriched by unsaturated C-species. The TPO profiles after CPO test at 450°C indicated a major peak at 350°C, suggesting the presence of C-species with intermediate reactivity or intermediate proximity to the metal particles, in between the highly reactive CHX fragments on metal sites and the polymeric C-species stored on the support.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Catalytic hydrogenation of CO2 into methanol and dimethyl ether over
           Cu-X/V-Al PILC (X=Ce and Nb) catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Francielle C.F. Marcos, José M. Assaf, Elisabete M. Assaf
      The production of methanol (MeOH) and dimethyl ether (DME) through CO2 hydrogenation is an attractive route to recycle CO2 and control its emission to the atmosphere. In the present work, the hydrogenation of CO2 into MeOH and DME over Al-pillared clays impregnated with different metals (Cu-X/V-AI PILC, where X=Ce and Nb) was investigated in the temperature range 200–300°C. The influence of additives on the physico-chemical properties of the catalysts was evaluated by N2 adsorption, ex situ XRD, TPR analysis, and in situ XANES and XRD. The acid sites were analyzed by FTIR analysis after adsorption of pyridine and NH3-TPD. The basic and metallic sites were analyzed by CO2-TPD and N2O-TPD, respectively. In situ XANES was used to investigate the Cu+ and CuO species. MeOH and DME selectivities were directly related to the presence of acid, basic and metallic sites and with the reaction temperature. The results indicated that the CuCe/V-Al PILC catalyst was the most promising catalyst for DME synthesis from CO2.
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      PubDate: 2017-05-16T20:10:21Z
       
  • TiO2 polymorph dependent SMSI effect in Co-Ru/TiO2 catalysts and its
           relevance to Fischer-Tropsch synthesis
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Francine Bertella, Patricia Concepción, Agustín Martínez
      Pure anatase and rutile TiO2 samples were synthesized by thermal treatment of reverse microemulsions and applied as supports for preparing Ru-promoted Co catalysts (0.5wt% Ru, 10wt% Co). The catalysts were characterized by ICP-OES, XRD, Raman spectroscopy, N2 physisorption, H2-TPR, electron microscopy (FESEM, HAADF-STEM), H2 chemisorption, XPS, and in situ IR-CO after H2 reduction and reaction with syngas, and their catalytic performance for Fischer-Tropsch synthesis (FTS) studied at industrial conditions (220°C, 2.0MPa, H2/CO=2). The two catalysts exhibited comparable mean Co particle sizes (5–6nm) as well as high and alike degrees of cobalt reduction (ca. 90%). The SMSI decoration effect arising during H2 reduction was much more pronounced for the anatase-supported catalyst resulting in lower cobalt-time-yield (CTY) compared to that supported on TiO2-rutile. In situ IR-CO under syngas conversion conditions showed equivalent cobalt surface reconstruction and nature of the surface Co0 sites for both catalysts in their working state, and revealed a partial reversibility of the SMSI effect during FTS by which a significant fraction of the decorated Co0 centers in the anatase-based catalyst was uncovered and became available for reaction. The implication of this effect on TOFs is discussed. The C5+ selectivity was higher for the rutile-based catalyst, although a clear impact of the SMSI effect on selectivities was not inferred from our results.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Acid-catalyzed liquid-phase alkylation of phenol with branched and linear
           olefin isomers
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Maikon A. Freire, Douglas T.S.L. Mendes, Lisiane S. Freitas, Rolf Beerthuis, Simonise F. Amarante, André L.D. Ramos
      Alkylation of phenolic compounds with olefins is an important industrial reaction to increase the chemical stability of bio-oil. In this study, the liquid-phase alkylation of phenol with linear (1-octene) and branched (diisobutylene) olefins was studied, in a batch reactor using homogeneous (sulfuric acid) and heterogeneous (Amberlyst-15) acid catalysts. Conversion and selectivity trends were compared and the effects of different operational conditions (temperature, phenol/olefin molar ratio and catalyst content) were evaluated employing factorial experimental design. The Amberlyst-15 solids acid resin was characterized by nitrogen physisorption and Brønsted acid sites titration. The heterogeneous catalyst showed satisfactory conversions with both olefins, albeit being less active than sulfuric acid. Higher conversions were obtained with diisobutylene than with 1-octene. C-alkylation was dominant in the diisobutylene reaction, including some product formation resulting from fragmentation of the diisobutylene olefin. However, mainly O-alkylation was observed under mild reaction conditions in the 1-octene reaction. Factorial experimental design showed that temperature was the variable that most influenced the conversion and selectivity trends, and the highest yields of di- and tri-alkylated products were obtained at elevated temperatures. A mechanistic model was proposed for both reactions.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Group 13 metal (Al, Ga, In) alkyls supported by N-heterocyclic carbenes
           for use in lactide ring-opening polymerization catalysis
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Gilles Schnee, Anaëlle Bolley, Frédéric Hild, David Specklin, Samuel Dagorne
      The synthesis of several N-heterocyclic carbene (NHC) group 13 metal adducts of the type (NHC)MR3 [NHC=1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp); M=Al, Ga, In; R=Me, Et] is described. In the case of the In adduct (IMes)InMe3, characterization data include its X-ray crystallographic determined molecular structure. The prepared compounds act as efficient ring-opening polymerization (ROP) initiators of rac-lactide, allowing access to either linear poly(lactic acid) (PLA) or cyclic PLA depending on the nature of the initiator and the reaction conditions. For these NHC-MMe3 systems, the addition of benzyl alcohol (acting as a chain transfer agent) was found to be beneficial both to ROP activity and control. In particular, the Al and In systems (IMes)MMe3 (M=Al, In) in combination with BnOH are highly effective ROP initiators of rac-lactide at room temperature (TOF=600h−1).
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      PubDate: 2017-05-16T20:10:21Z
       
  • Hydrogen production from steam and oxidative steam reforming of liquefied
           petroleum gas over cerium and strontium doped LaNiO3 catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Priscila P. Silva, Rondinele A.R. Ferreira, Fábio B. Noronha, Carla E. Hori
      This study investigated LaNiO3 doped with small amounts of cerium and strontium as catalyst precursors for LPG steam and oxidative reforming. La1-xCexNiO3 (x=0, 0.05, 0.1) and La1-xSrxNiO3 (x=0, 0.05, 0.1) perovskite-type oxides were prepared by precipitation. The characterization showed that samples doped with cerium had smaller nickel average particle size and higher oxygen storage capacities when compared to the samples containing strontium. All the samples were tested for LPG steam and oxidative steam reforming at 873K. The LPG steam reforming results showed that all catalysts presented strong deactivation. The addition of a small amount of oxygen to the system (oxidative steam reform) leads to better catalytic performance for all samples. The La0.95Ce0.05NiO3 precursor stood out by presenting better performance for hydrogen production in all conditions. These results can be attributed to the presence of ceria and to smaller metallic nickel average crystallite sizes. The results of the in-situ X-ray diffraction analysis indicated that for the sample originated from La0.95Ce0.05NiO3, the reduced form of the material was preserved longer, thus justifying leading to greater stability in reaction conditions. In-situ XANES data collected during steam LPG reforming showed that the samples derived from La0.95Ce0.05NiO3 presented no significant change in the increase of the white line, which, in this case, would characterize the oxidation of the precursors. The same reforming reactions were conducted at higher temperatures using La0.95Ce0.05NiO3 precursor, and the results showed that at higher temperatures it is possible to maintain high activity, with stable hydrogen production.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Influence of acidic properties of different solid acid catalysts for
           glycerol acetylation
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): B.O. Dalla Costa, H.P. Decolatti, M.S. Legnoverde, C.A. Querini
      The glycerol esterification with acetic acid is studied in this work using propylsulfonic functionalized mesoporous silica (Pr-SO3H-SBA-15), and compared with H-ZSM-5 and H-Beta zeolites. The reaction was carried out in a batch reactor using a 6:1 molar ratio of acetic acid to glycerol. The initial TOF for the glycerol conversion was significantly higher in the propylsulfonic mesoporous silica, as compared to the two zeolites. These two catalysts have acid sites densities (μmolm−2) that are less than half than that displayed by the SBA-based catalyst. It was possible to obtain 96% conversion in 2.5h, with 87% selectivity to the products of interest diacetylglycerol (DAG) + triacetylglycerol (TAG), being the ratio DAG/TAG=1.7. The catalyst deactivates partly due to sulfonic groups loss and to coke deposition during the reaction, as observed when it was used in a second reaction cycle without any treatment in between cycles. The catalyst lost activity, but maintained the selectivity, associated to a non-selective site poisoning.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Heterogeneous catalysis in complex, condensed reaction media
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): David C. Cantu, Yang-Gang Wang, Yeohoon Yoon, Vassiliki-Alexandra Glezakou, Roger Rousseau, Robert S. Weber
      Many reactions required for the upgrading of biomass into fuels and chemicals—hydrogenation, hydrodeoxygenation, hydrocracking—are ostensibly similar to those practiced in the upgrading of petroleum into fuels. But, repurposing hydroprocessing catalysts from refinery operations to treat bio-oil has proved to be unsatisfactory. New catalysts are needed because the composition of the biogenic reactants differs from that of petroleum-derived feedstocks (e.g. the low concentration of sulfur in cellulose-derived biomass precludes use of metal sulfide catalysts unless sulfur is added to the reaction stream). New processes are needed because bio-oils oligomerize rapidly, forming intractable coke and “gunk”, at temperatures so low that the desired upgrading reactions are impractically slow, and so low that the bio-oil upgrading must be handled as a condensed fluid. Ideally, the new catalysts and processes would exploit the properties of the multiple phases present in condensed bio-oil, notably the polarizability and structure of the fluid near a catalyst’s surface in the cybotactic region. Molecular simulation results of the cybotactic region adjacent to different catalyst surfaces in the hydrogenation of phenol suggest that Pd catalysts supported on hydrophilic surfaces are more active than catalysts based on lipophilic supports because the former serve to enhance the concentration of the phenol in the vicinity of the Pd. The effect stems from thermodynamics, not the rate of mass transport.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Methylene blue oxidation over iron oxide supported on activated carbon
           derived from peanut hulls
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Lindaura Almeida da Silva, Sarah Maria Santana Borges, Priscilla Nogueira Paulino, Marco A. Fraga, Sérgio Telles de Oliva, Sérgio Gustavo Marchetti, Maria do Carmo Rangel
      In order to contribute to the environment preservation, catalysts based on iron oxides supported on activated carbon were prepared from peanut hulls and evaluated in Fenton reaction to remove methylene blue from model wastewaters. The activated carbons were prepared by simultaneous carbonization and activation of peanut hulls with low amounts of sodium hydroxide and then impregnated with iron nitrate solutions to get samples with 5, 7.5,10, 12.5 and 15wt.% Fe. All solids were microporous and made of hematite and magnetite supported on activated carbon. The amount of magnetite changed with iron content and was related to surface oxidation, producing more oxygenated groups (carboxylic acids, lactones, carboxylic anhydrides and phenols) than activated carbon. Both activated carbons and iron-based catalysts were able to remove methylene blue from aqueous streams by adsorption and oxidation, the activity of activated carbon being assigned to oxygenated groups. For iron oxide-based catalysts, the adsorption capacity was related to the increase of surface oxygenated groups while the oxidation activity was assigned to the amount and crystals size of magnetite, besides the surface oxygenated groups. The association of these properties led to catalysts with close performances, being the catalyst with 10wt.% Fe slightly more efficient than the others in dye removal. The obtained catalysts produced low amounts of byproducts, being promising to remove dyes in industrial wastewaters. In addition, they have the advantage of being prepared with less sodium hydroxide than the traditional preparations, decreasing the amount of wash water, besides reducing the amounts of peanut hulls disposed in the environment.
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      PubDate: 2017-05-16T20:10:21Z
       
  • VOx-Pt/Al2O3 catalysts for hydrogen production
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Tathiana M. Kokumai, Daniel A. Cantane, Guilherme T. Melo, Luigi B. Paulucci, Daniela Zanchet
      Platinum supported catalysts are promising systems to a wide range of catalytic reactions involved in the hydrogen production chain. The performance of these catalysts can be enhanced by designing properly their nature, composition and structure. In this context, the addition of a second metal oxide on a catalyst composed of a well dispersed Pt phase over a high surface area support may be a powerful strategy. In this work we impregnated VOx species over Pt/Al2O3 and evaluated the catalysts performance for water-gas shift (WGS) and glycerol steam reforming (GSR) reactions. The catalysts characterization showed that VOx species formed over the Pt/Al2O3 surface were not deeply affected by the loading in the range of 0.5–2.0V atoms per nm2 and were reduced at mild temperatures. In situ measurements during catalysts activation and WGS reaction showed that VOx species presented mixed valence (V3+/V4+) while Pt was in metallic state. The addition of vanadium increased Pt/Al2O3 WGS activity; however, the improvement did not linearly correlate with the loading. Under GSR, the results indicated that the WGS step was favored by the presence of vanadium but the selectivity to H2 decreased, which could be attributed to the parallel reactions enhanced by the acidic nature of the VOx sites.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Nb and V-modified silicate for conversion of glycerol: Comparison between
           the waste and commercial product
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Henrique S. Oliveira, Patterson P. Souza, Luiz C.A. Oliveira
      Silicate was modified with Nb and V targeting the conversion of waste and commercial glycerol to obtain high added value chemicals. The results showed that the presence of vanadium and niobium improved the glycerol conversion (>95%) with good selectivity to allyl alcohol (commercial glycerol) or acetone (waste glycerol). The presence of Nb and V promoted the formation of nanorods morphology, generating small particle size and increasing the amount of exposed niobium. The results showed clearly that the type of glycerol can drive the selectivity of the reaction, indicating that the performance of the catalysts may be tested using both waste or commercial glycerol in order to avoid bad interpretation.
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      PubDate: 2017-05-16T20:10:21Z
       
  • Acetone from ethanol employing ZnxZr1−xO2−y
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Leydi del R. Silva-Calpa, Priscila C. Zonetti, Daniela C. de Oliveira, Roberto R. de Avillez, Lucia G. Appel
      The main purpose of this work is to contribute to the description of the acetone synthesis from ethanol employing ZnxZr1-xO2-y based catalysts. The catalytic behavior of these solids was evaluated (isoconversion) in the acetone synthesis. The most active catalyst and m-ZrO2 (used as a reference) were characterized by the following techniques: pyridine adsorption, TPD of NH3, TPD of CO2, TPD of ethanol followed by IR (DRIFTS)/MS, TPD of ethanol followed by XANES at the Zr K-edge and Zn K-edge and XRD in situ. The present study suggests that the main steps of the acetone generation from ethanol are the following: firstly, ethoxide species are generated and, then, they are dehydrogenated to acetaldehyde. Both steps are related to strong basic and acid sites. Acetaldehyde reacts with the O of the solid solution generating acetate species and vacancies on the catalyst surface. These carboxylate species condensate (strong basic sites) and generate acetone and CO2. Water dissociates on the vacancies of the catalyst and reoxidizes the its surface, closing the catalytic cycle. All these steps might occur on Zn+2 and on the species in its vicinity (XANES).
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • One-step conversion of xylose to furfuryl alcohol on sulfated
           zirconia-supported Pt catalyst—Balance between acid and metal sites
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Rafael F. Perez, Simone J. Canhaci, Luiz E.P. Borges, Marco A. Fraga
      Pt/ZrO2-SO4 catalysts bearing different acid/metal site ratios were prepared and the balance between those two sorts of surface centers was investigated on liquid-phase chemoconversion of xylose. Direct conversion of xylose to furfuryl alcohol was successfully reported for the very first time on a single multifunctional catalyst and it was found to proceed via intermediate formation of the ketopentose isomer. The impact of the disposal of acid and metal sites on catalyst surface was assessed by comparing the synthesized single multifunctional catalysts with dual catalytic systems at which active sites are placed on two different solid surfaces. Reaction network and product distribution were shown to depend on such arrangement. It was suggested that furfuryl alcohol is formed through dehydration-hydrogenation cascade reactions on independent acid and metal sites on dual catalytic systems while one-step conversion occurs on vicinal acid-metal pair sites created on single multifunctional catalysts. The creation of isolated metal centers on multifunctional catalyst surface was seen to allow the formation of xylitol while the existence of sole acid sites led to the production of furfural.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Thermocatalytic cracking kinetics of myristic acid adsorbed on catalysts
           with different acidity
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Enio D. Bruce, Roger Frety, Camila M. Teixeira, Celmy B.M. Barbosa, Jose G.A. Pacheco
      Mass losses related to the vaporization/decomposition of myristic acid, either pure or adsorbed on SiO2, γ-Al2O3, SiO2-Al2O3 and HZSM-5 catalysts were obtained by non isothermal thermogravimetric analysis from room temperature up to 650°C. The adsorption of myristic acid on catalysts greatly changed the mass loss behavior of myristic acid, suggesting a significant decomposition of this fatty acid during heating as compared to its essentially simple volatilization in absence of catalyst. A model-free kinetic was used to estimate the values of apparent activation energy of the mass losses from experiments performed at heating rates of 3, 7, 10 and 15°Cmin−1. In absence of a catalyst, myristic acid presented a single mass loss event with an activation energy value of ∼87–90kJmol−1. In the case of myristic acid adsorbed on SiO2,γ-Al2O3, SiO2-Al2O3 and HZSM-5 at least two different mass loss events occurred during linear heating, associated to myristic acid volatilization/decomposition. The activation energies calculated for both these events, with the exception of myristic acid adsorbed on silica, exhibited values much higher than 90kJmol−1. The apparent activation energy of the second mass loss events was always higher than that of the first mass loss events. Activation energy of the second mass loss reached a value as high as 190kJmol−1 at which point myristic acid was strongly adsorbed on HZSM-5. Such a high value suggests CC and CH bond ruptures and not only decarboxylation often described as the main reaction path when saturated fatty acids are pyrolyzed.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Steam reforming of toluene, methane and mixtures over Ni/ZrO2 catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): E.B. Silveira, R.C. Rabelo-Neto, F.B. Noronha
      This work studied the performance of Ni catalysts supported on three different zirconia structures for SR of toluene, methane and methane/toluene mixtures. The presence of both reactants in the feed decreased the conversion of toluene and methane. This was due to the increase in the concentration of CHx species on the surface of the metallic particle. All Ni/ZrO2 catalysts deactivated during SR of toluene, methane or the mixture. Scanning electron microscopy and thermogravimetric analysis revealed the formation of carbon deposits over the surface of catalysts. However, the amount of carbon deposited depended on the reaction conditions and the structure of zirconia. Monoclinic zirconia exhibits a lower densitiy of acid sites and a higher degree of hydration, which contributes to the lower carbon formation. The amount of carbon deposited over all catalysts significantly increased during SR of the mixture. This is due to a decrease in the rate of the gasification reaction and an increase in the rate of the CHx species formation reaction, which enhances the catalysts deactivation rate.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • Selective hydrogenolysis of glycerol over Ir-Ni bimetallic catalysts
    • Abstract: Publication date: 1 July 2017
      Source:Catalysis Today, Volume 289
      Author(s): Aracelis J. Pamphile-Adrián, Pedro P. Florez-Rodriguez, Mattheus Henrique M. Pires, Geronimo Perez, Fabio B. Passos
      The effect of the addition of Ni to Ir/γ-Al2O3 was studied for glycerol hydrogenolysis reaction. The catalysts were characterized by textural analysis, XRD, H2-TPR, XPS and TEM. In all cases, the addition of Ni to Ir/γ-Al2O3 produced a significant increase in glycerol conversion, and a high selectivity to 1,2-PDO was maintained. TOF values increased from 0.4×10−2 s−1 for Ir monometallic catalyst, to 4.3×10−2 s−1 for bimetallic IrNi2_C catalyst. The latter was the most active catalyst among the calcined bimetallic catalysts. Selectivity to 1,2-PDO had an insignificant decrease from 89.9% for Ir monometallic catalyst to 83.1% for IrNi2_C catalyst. However, non-calcined IrNi2 catalyst presented a TOF value of 1.3×10−2 s−1. This result indicates that the calcination step was fundamental to obtain a strong Ir-Ni interaction that lead to better performances of the bimetallic catalysts. Ir-Ni interaction was evidenced by XPS analyses of the calcined series of catalysts, where the presence of an Irδ+ species was observed (0<δ<4), suggesting an electronic density transferring from Ni to Ir.
      Graphical abstract image

      PubDate: 2017-05-16T20:10:21Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287


      PubDate: 2017-04-10T04:09:27Z
       
  • Contents list
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287


      PubDate: 2017-04-10T04:09:27Z
       
  • Introduction by guest editors
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Nicolas Keller, Didier Robert, Pilar Fernández-Ibañez, Sixto Malato


      PubDate: 2017-04-10T04:09:27Z
       
  • Photocatalytic treatment of saccharin and bisphenol-A in the presence of
           TiO2 nanocomposites tuned by Sn(IV)
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): K. Davididou, E. Hale, N. Lane, E. Chatzisymeon, A. Pichavant, J.-F. Hochepied
      This study deals with the photocatalytic treatment of saccharin (SAC) and bisphenol-A (BPA) under UV irradiation. For this purpose, novel submicronic anatase–rutile nanocomposite particles with tuned phase ratio, produced by thermohydrolysis of acidic Ti(IV) solutions in the presence of controlled amounts of Sn(IV), were used. These catalysts were then assessed regarding their efficiency to degrade SAC or BPA, which are contaminants of increased environmental and health concern. The effect of various operating conditions, such as the anatase-rutile ratio (100:0, 85:15, 70:30), catalyst concentration (50–600mg/L) and solute concentration (3–10mg/L) was investigated. Furthermore, catalyst reuse –an important but little studied aspect- was assessed. Anatase–rutile nanocomposites were successfully prepared presenting good crystallinity and surface quality. Their activity was about the same for removing SAC or BPA from water. It was found that photocatalytic performance was increased with catalyst loading up to 400mg/L. A further increase to 600mg/L did not significantly enhance BPA removal, thus associating this tendency with screening effects. Also, photocatalytic efficiency was increased with initial solute concentration decrease. Organics degradation followed a pseudo-first order kinetic rate in terms of both SAC and BPA removal. The reproducibility of catalyst activity was assessed in three successive reuse cycles, where the removal percentage of initially 5mg/L SAC was maintained as high as 70% at the end of the 3rd cycle, in the presence of initially 400mg/L anatase catalyst, and after 90min of treatment. Finally, additional experimental runs were carried out with ultrasound cleaning (US) being applied to the reactant mixture at the beginning of each reuse cycle, but it was found to have no significant effect on treatment efficiency.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Microcontaminant removal in secondary effluents by solar photo-Fenton at
           circumneutral pH in raceway pond reactors
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): I. De la Obra, L. Ponce-Robles, S. Miralles-Cuevas, I. Oller, S. Malato, J.A Sánchez Pérez
      This paper deals with raceway pond reactors (RPRs) as an alternative photoreactor for solar photo-Fenton applications. Raceway pond reactors are common low-cost reactors which can treat large volumes of water. The experiments were carried out with Fe3+:EDDS complex in the secondary effluent of a municipal wastewater treatment plant spiked with a mixture of 100 μg/L each of five pharmaceuticals (carbamazepine, flumequine, ibuprofen, ofloxacin and sulfamethoxazole) at circumneutral pH. In a preliminary stage, two operating strategies, sequential addition of iron sulfate and Fe3+:EDDS complex at a 1:2 molar ratio were compared, and Fe3+:EDDS complex was found to be the best option. The effect of liquid depth (10, 15 and 20 cm) was also explored. 90% pharmaceutical removal was achieved with accumulated solar UV energy of around 1kJ/L. Finally, RPRs and tubular photoreactors with compound parabolic collectors (CPC) were compared under realistic conditions. Pharmaceutical removal efficiency was four times higher, increasing from 0.26mg/kJ with CPC reactors to 1.07mg/kJ in the 15-cm-deep RPR. As far as the authors know, this is the first detailed study on the effect of liquid depth in RPRs at circumneutral pH.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Legionella jordanis inactivation in water by solar driven processes:
           EMA-qPCR versus culture-based analyses for new mechanistic insights
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): María Inmaculada Polo-López, María Castro-Alférez, Samira Nahim-Granados, Sixto Malato, Pilar Fernández-Ibáñez
      In this contribution, the validation of EMA-qPCR method for the quantification of viable Legionella spp. in water after solar treatments was carried out. EMA-qPCR was used to evaluate the different effects of several solar water disinfection processes over this bacterium, and furthermore their mode of action. Inactivation of Legionella jordanis in water by solar photocatalytic (TiO2 and TiO2/H2O2) and solar photochemical (solar/H2O2 and solar disinfection) processes have been investigated under natural sunlight. Culture-based and molecular (EMA-qPCR) techniques were systematically compared for the analysis of treated water samples. Solar tests were done under natural solar radiation (clear sky) and ambient temperature (20–35°C) for 2h, using H2O2/Solar (10, 20 and 50mg/L), TiO2/Solar (100, 200, 300, 400, and 500mg/L) and TiO2/H2O2/Solar (100/10, 200/10, 500/10mg/L). According to culture-based method, the best results of bacterial inactivation were obtained for 500/10mg/L of TiO2/H2O2. The order of efficiency to reach complete inactivation was: TiO2/H2O2/solar (5min)>TiO2/solar (15min)≈H2O2/solar (15min)>Solar only disinfection (90min). Moreover, EMA-qPCR and culturable counting results showed a direct correlation for samples treated with TiO2/solar for those catalyst concentrations that generate a strong oxidative attack over the cell wall. EMA-qPCR results demonstrated to be a good method to detect damaged and dead cells when the treatment affects the integrity of the cell’s membrane, as occurs under photocatalysis. Meanwhile for solar disinfection and solar/H2O2 (at non-toxic concentrations, <1.5mM), where membrane integrity remained unaltered, EMA-qPCR results couldn’t discriminate between alive and dead cells, even when the bacteria were not culturable.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Decahedral anatase titania particles immobilized on zeolitic materials for
           photocatalytic degradation of VOC
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): I. Jansson, K. Kobayashi, H. Hori, B. Sánchez, B. Ohtani, S. Suárez
      Decahedral anatase titania particles (DAPs) immobilized on zeolites (zeolite/DAP hybrids), have been prepared by the first time. DAPs have been synthesized from titanium chloride (TiCl4) through a gas-phase reaction process by rapid heating and quenching. DAPs with well-defined {101} and {001} facets were synthetized and dispersed onto the zeolites. The incorporation of an 8wt% of DAPs into the zeolites has been achieved by means of the freezing-drying technique. Two types of zeolites (ZSM-5 and zeolite Y) with different SiO2/Al2O3 contents have been selected as adsorbents. The photocatalytic properties for the degradation of representative volatile organic compounds (VOC), i.e. acetaldehyde, formaldehyde or trichloroethylene were analyzed under batch and continuous flow reactors. Raw materials and composites were characterized by SEM, N2 adsorption-desorption, UV–vis spectroscopy, XRD, zeta potential and the amount of VOC adsorbed was measured at dynamic conditions. Zeolite/DAP hybrids combine the textural and crystalline properties of zeolite and DAPs phases. The zeolite type (crystal structure, SiO2/Al2O3 ratio and surface net charge) play a relevant role in the dispersion of DAPs. Zeolite/DAP composites show better photocatalytic performance than those prepared with commercial TiO2 due to the presence of {001} facets in the former. The composites prepared with hydrophobic ZSM-5 and DAPs, are the most versatile materials for photooxidation of aldehydes and organochloride compounds, with substantially less formation of non-desirable reaction products respect to those based on benchmark TiO2.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • A simple non-aqueous route to nano-perovskite mixed oxides with improved
           catalytic properties
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Liwei Hou, Hui Zhang, Lihua Dong, Li Zhang, Daniel Duprez, Sébastien Royer
      Highly crystalline LaBxO3 (B=Co, Mn) perovskites are produced through a simple non-aqueous benzyl alcohol (BA) route. Textural properties of BA-derived materials were compared to those obtained for solids of comparable composition, prepared by classical citric acid complexation method. Oxygen mobility in synthesized materials was evaluated by oxygen isotopic (18O) exchange (OIE). Perovskites obtained with the BA route shows much larger specific surface area, smaller crystallite size and superior oxygen mobility. Such improvement in properties is in favor of low temperature catalytic oxidation, as evaluated by CO oxidation.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Delaminated kaolinites as potential photocatalysts: Tracking degradation
           of Na-benzenesulfonate test compound adsorbed on the dry surface of
           kaolinite nanostructures
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Péter Szabó, Balázs Zsirka, Dávid Fertig, Erzsébet Horváth, Tamás Csizmadia, János Kristóf
      Based on their bandgap values, kaolins can have semiconductive and photocatalytic properties enabling them to use as potential photocatalysts. Kaolinite nanostructures (Knano) and silver-coated kaolinite nanohybrids (Knano(Ag)) were made of ordered (Hinkley Index, HI=1.4) and disordered (HI=0.3) kaolins via intercalation/deintercalation. The book-type kaolin built up from tetrahedral(T)-octahedral(O) double layers has very low photocatalytic activity. At the same time the nanostructures made of individual TO layers show photochemical activity in spite of the fact that their bandgap values are comparable to those of the book-type ones. The presence of Ag on the surface significantly reduced the bandgap and shifted the excitation wavelength towards the visible range. This phenomenon supports the supposition that kaolinite has some semiconductive character. This work presents the connection between photocatalytic activity and morphology for the first time. The surface activity of kaolinite nanostructures and their Ag-hybrids was studied through the decomposition of sodium-benzenesulfonate (BS) test compound with attenuated total reflection Fourier transform infrared spectroscopy (FT-IR/ATR). BS decomposition can be detected on the Knano surface but with low efficiency. The presence of silver can significantly improve the mineralization efficiency. No correlation was found between the activity and the quantity of Ti and Fe contaminants and the amount of Ag on the surface. However, the activity could be correlated with the order-dependent morphology (mixture of semi-hexagonal and nanoscroll-type structures), the pore size and with the increase of the surface coverage.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Novel ‘Pickering’ modified TiO2 photocatalysts with high
           De-NOx efficiency
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): S. Karapati, T. Giannakopoulou, N. Todorova, N. Boukos, I. Papailias, D. Dimotikali, C. Trapalis
      Modified TiO2 nanoparticles were prepared by a Pickering emulsions route with the use of hydrophobic (oleylamine) and hydrophilic (polyethylene glycol) organic surfactants and their combination, as well. The attachment of modifiers to the TiO2 nanoparticles was proved via FT-IR and thermal analysis. Thicker modifier layer was formed on the TiO2 surface but lower average particle size was attained when amphiphilic modification was applied that was revealed by TEM analysis and dynamic light scattering, correspondingly. The amphiphilic modification permitted control of the hydrophobic properties of the TiO2 nanoparticles so that their incorporation in cement matrix led to preparation photocatalytic cement materials with superior De-NOx efficiency.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Titanium and zirconium-based mixed oxides prepared by using pressurized
           and supercritical fluids: On novel preparation, microstructure and
           photocatalytic properties in the photocatalytic reduction of CO2
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): K. Kočí, L. Matějová, I. Troppová, M. Edelmannová, T. Prostějovský, P. Peikertová, T. Brunátová, J. Lang, L. Čapek, L. Obalová
      The ZrxTi1-xOn mixed oxides with various Ti:Zr molar ratios and parent TiO2 and ZrO2 were prepared unconventionally, combining the reverse micelles-controlled sol-gel method with high-pressure processing by pressurized and supercritical fluids. The mixed oxides were characterized using several complementary characterization methods and investigated in the photocatalytic reduction of CO2. Applied novel unconventional processing affected significantly the (micro)structure of mixed oxides, which was further reflected to their optical and thus electronic properties. The Zr0.1Ti0.9On mixed oxide showed the best photocatalytic behavior in a consequence of the optimal crystallinity and the lowest band gap energy from all mixed oxides. The Zr0.1Ti0.9On mixed oxide was of bicrystalline TiO2 anatase-brookite structure (67:33wt.%) showing small crystallite-sizes, which allowed the optimal surface phase junction.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
  • Anatase TiO2 nanotube arrays and titania films on titanium mesh for
           photocatalytic NOX removal and water cleaning
    • Abstract: Publication date: 1 June 2017
      Source:Catalysis Today, Volume 287
      Author(s): Motola Martin, Satrapinskyy Leonid, Roch Tomáš, Šubrt Jan, Kupčík Jaroslav, Klementová Mariana, Jakubičková Michaela, Peterka František, Plesch Gustav
      An anodization method was developed for the preparation of highly photoactive titania nanotube arrays (TiNTs) on commercially available titanium mesh. The prepared material was characterized from the point of view of its structure and possible photocatalytic applications and was compared with titania films deposited on the Ti-mesh by liquid deposition (TiO2-LD) and sol-gel methods (TiO2-SG). The photoactivity was determined in gas phase using NOX decomposition according to the ISO standard no. 22 197-1 (2007) as well as in liquid phase by decolorization of organic dyes e.g. methylene blue (MB) and rhodamine B (RhB). The investigated anatase nanotube arrays on Ti mesh showed the highest photoactivity in both gaseous and liquid phases and are promising for applications in photocatalytic reactors for environmental purification.
      Graphical abstract image

      PubDate: 2017-04-10T04:09:27Z
       
 
 
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