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Journal Cover Catalysis Today
  [SJR: 1.378]   [H-I: 142]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2970 journals]
  • IFC - Editorial Board
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271




      PubDate: 2016-05-15T09:02:08Z
       
  • Contents list
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271




      PubDate: 2016-05-15T09:02:08Z
       
  • International symposium on advances in hydroprocessing of oil fractions
           (ISAHOF 2015)
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Jorge Ancheyta, Gilbert F. Froment



      PubDate: 2016-05-15T09:02:08Z
       
  • The use of CoMoS catalysts supported on carbon-coated alumina for
           hydrodeoxygenation of guaiacol and oleic acid
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): P.A. Nikulshin, V.A. Salnikov, A.N. Varakin, V.M. Kogan
      The objective of the work was to elucidate the effect of coating alumina by carbon on the catalytic properties of CoMoS catalysts supported on carbon-coated alumina (CCA) in hydrodeoxygenation (HDO) reactions. The catalysts were synthesized using 12-molybdophosphoric heteropolyacid, cobalt citrate and CCA and characterized by N2 physisorption, temperature-programmed desorption of ammonia, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in HDO of guaiacol and oleic acid. It was found that using the CCA as supports of the CoMo/CCA catalysts altered the morphology and structure of the CoMoS active phase species. With the increase of carbon content up to 5.6wt.%, the average length of CoMoS species passed through minimum at 2.4nm and the average stacking number increased from 1.4 to 1.6. The increase of carbon content in the CCA led to rising the sulphidation degree of both metals and effective cobalt content into CoMoS phase. Using CCA supports instead of alumina for preparation of CoMo catalysts resulted in improving their activities in HDO of guaiacol and oleic acid and significantly reduced deactivation. Enhanced catalytic properties of CoMo/C x /Al2O3 catalysts were related to lower acidity of CCA supports. CoMo/CCA catalyst with 2wt.% of carbon had maximal activity in HDO of guaiacol and oleic acid thanks to an optimal balance between cobalt content into CoMoS phase particles and their average length.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Catalytic performance of CoMo/Al2O3-MgO-Li(x) formulations in DBT
           hydrodesulfurization
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Dora Alicia Solís-Casados, Luis Escobar-Alarcón, Tatiana Klimova, Jose Escobar-Aguilar, Enrique Rodríguez-Castellón, Juan A. Cecilia, Christian Morales-Ramírez
      In this work, it is reported the catalytic performance of low acidity catalysts in the hydrodesulfurization reaction of dibenzothiophene. Catalytic CoMo formulations supported on materials based on Al2O3-MgO modified with several amounts of lithium oxide (x =1, 5 and 10wt.% of Li2O) were used. It was correlated the effect of the atomic lithium content on the dispersion of the Mo and Co phases in their oxidized and sulfided forms, in order to explain their catalytic performance. Elemental chemical composition on the catalyst surface as well as sulfurization degree and the interaction of sulfided Co and Mo phases with the support were determined by X-ray photoelectron spectroscopy (XPS). Textural properties were measured by N2 physisorption technique; the identification of the crystalline phases was studied by X-ray powder diffraction (XRD) and Raman spectroscopy (RS). The chemical coordination state was determined from diffuse reflectance spectroscopy (DRS) measurements. Reducibility was determined by temperature programmed desorption (TPR). Dispersion of MoS2 crystallites was revealed by high resolution transmission electron microscopy (HRTEM). Catalytic activity of the formulations was evaluated using a pressurized batch reaction system through the hydrodesulfurization reaction of dibenzothiophene as a model molecule, selectivity toward direct desulfurization reaction route was studied following the biphenyl and cyclohexylbenzene reaction products identified by using gas chromatography; results show that there is an optimal amount of 3.7 at.% of Li, which maintains hydrodesulfurization function and decrease the hydrogenation function compared to the conventional CoMo catalyst.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Deactivation study of K2O/NaX and Na2O/NaX catalysts for biodiesel
           production
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Gabriel E. Galván Muciño, Rubi Romero, Iván García-Orozco, Armando Ramírez Serrano, Ramiro Baeza Jiménez, Reyna Natividad
      A performance comparison of K2O/NaX and Na2O/NaX catalysts was carried out in the safflower oil transesterification. The studied variables were three: number of cycles of use, washing between cycles and type of solvent to do the washing. Parameters specified by the European standard UNE-EN 14214 were taken as response variables. These parameters were methyl esters content, viscosity and acid value. The fresh and spent catalysts were characterized by XRD, SEM, IR, AA and Hammett Method. It was found that with both catalysts after the first use, a high methyl esters content is obtained (94% and 98% with the K2O/NaX and Na2O/NaX, respectively). However, both catalysts lose activity according to a second order deactivation law. The deactivation constant of the K2O/NaX was found to be about three times higher than that calculated for the Na2O/NaX catalyst. The deactivation was found to be mainly due to leaching of active species and catalytic surface fouling. Nevertheless, the Na2O/NaX catalyst leads to attain high methyl esters content (94–96%) very close to that specified by the aforementioned standard even after several uses. Also, viscosity and acid values of the biodiesel produced with this catalyst met the norm at all uses. Therefore, between the studied catalysts here, Na2O/NaX is the recommended one to produce biodiesel from safflower oil transesterification at a greater scale.
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      PubDate: 2016-05-15T09:02:08Z
       
  • CFD prediction and experimental validation of surface cathode
           concentration in filter press parallel plate electrolysers
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): G. Rodríguez, F.Z. Sierra-Espinosa, A. Álvarez, S. Silva, J.A. Hernández
      Parallel plate electrolysers are analysed using computational fluid dynamics, CFD, with emphasis on the region close to the surface of the cathode. The numerical solution takes place inside the diffusive layer where chemical reactions occur. Numerical predictions in this region are proposed to obtain detailed calculations of electroactive species concentration (Cu2), C, which is affected by the hydrodynamic behaviour of the electrolyte. The concentration C plays a main role since it is related to the mass transport coefficient, k m , in order to define the efficiency of the reactor. This approach allows the designer of electrolysers avoiding the use of correlations where the Reynolds (Re), Sherwood (Sh) and Schmidt (Sc) numbers based on average velocity are used to calculate the value of C and k m . Therefore a fully developed flow in the reactor is not a condition, since the value of C and k m is calculated with the actual velocity of the electrolyte in the boundary layer, at a non-dimensional distance to the wall as small as y + ≈ 5. The results are compared against data reported in the literature showing good agreement. Therefore, a solution of the hydrodynamics and the electrochemistry, link together in the near wall region, is obtained by refinement of the computational grid.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Experimental design optimization of the tetralin hydrogenation over
           Ir–Pt-SBA-15
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Verónica A. Valles, Brenda C. Ledesma, Lorena P. Rivoira, Jorgelina Cussa, Oscar A. Anunziata, Andrea R. Beltramone
      Experiment design-response surface methodology (RSM) is used in this work to model and optimize two responses in the hydrogenation of tetralin to decalin using bimetallic Ir–Pt-SBA-15 catalyst. In this study, we analyze the influence of the nature of the catalyst (metal molar fraction and metal loading), the catalyst/substrate ratio and the temperature of the reaction as factors for the design. The responses analyzed were conversion at 3h and at 5h of reaction time. The response surfaces were obtained with the Box–Behnken design, finding the best combination between the reaction parameters that allowed optimizing the process. By applying the statistic methodology, the higher levels of the two objective functions were obtained employing the catalyst with 1wt.% of iridium and 0.7–0.8wt.% of platinum; the optimal ratio between mass of catalyst and mole of tetralin was 17–19g/mol and temperature between 200 and 220°C.
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      PubDate: 2016-05-15T09:02:08Z
       
  • HDS performance of NiMo catalysts supported on nanostructured materials
           containing titania
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Julio Cesar Morales-Ortuño, Rodrigo Arturo Ortega-Domínguez, Patricia Hernández-Hipólito, Xim Bokhimi, Tatiana E. Klimova
      In the present work, NiMo catalysts supported on titania-containing materials of the SBA family (Ti-SBA-15 and Ti-SBA-16) and on titania nanotubes of different pore diameters were prepared with the aim of selecting the most promising catalysts for deep hydrodesulfurization (HDS) of gas oil. Supports and catalysts were characterized by nitrogen physisorption, XRD, temperature programmed reduction, ammonia TPD, UV–vis DRS and scanning electron microscopy (SEM-EDX). Sulfided catalysts were characterized by HRTEM and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). For comparison purposes, a conventional NiMo/γ-Al2O3 catalyst was used. In HDS of DBT, all catalysts supported on titania-containing nanostructured materials showed similar activity as the NiMo/γ-Al2O3 reference, but in HDS of 4,6-DMDBT their activities were about twice higher than that of NiMo/γ-Al2O3. Regarding selectivity, for DBT HDS, the presence of titania in the supports resulted in an increase in the proportion of CHB product, whereas for 4,6-DMDBT different behavior was observed. Thus, NiMo catalysts supported on Ti-SBA-15 and Ti-SBA-16 showed similar selectivity as the NiMo/γ-Al2O3. On the contrary, the catalysts supported on titania nanotubes allowed reaching high conversions of 4,6-DMDBT with a much lower proportion of hydrogenated products, which is an interesting result not observed by us previously.
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      PubDate: 2016-05-15T09:02:08Z
       
  • NiW/MgO–TiO2 catalysts for dibenzothiophene hydrodesulfurization:
           Effect of preparation method
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Alida Elizabeth Cruz Pérez, Yesenia Torrez Jiménez, Jessica Joana Velasco Alejo, Trino A. Zepeda, Dora María Frías Márquez, María Guadalupe Rivera Ruedas, Sergio Fuentes, Jorge Noé Díaz de León
      In the present work NiW-based catalysts supported on binary MgO–TiO2 mixed oxides (MT-x, were x is the mol% of TiO2) were prepared by aqueous and non-aqueous methods. The results from the characterization techniques (N2 adsorption/desorption, XRD, UV–vis DRS and HRTEM) were used to establish a relationship between the preparation method and the structural changes of W phases as well the catalytic activity. N2 adsorption/desorption isotherms showed higher surface areas with the increase on mol% of TiO2. Catalysts characterization showed that the preparation method did not change the original structure of the supports. Furthermore, the presence of NiO and NiWO4 was not observed in any sample, thus, the supports allowed a good dispersion of Ni and W species. DRS spectra showed the presence of W6+ in octahedral coordination and tetrahedral Ni2+. Correlation of the catalytic activity in the DBT HDS reaction and the fraction of W atoms on the edge of WS2 crystallites indicated that the aqueous impregnation on MT25, followed by drying at 393K leads to the formation of a greater number of catalytically active sites available for interaction with DBT molecules.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Relation between composition and morphology of K(Co)MoS active phase
           species and their performances in hydrotreating of model FCC gasoline
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): D. Ishutenko, P. Nikulshin, A. Pimerzin
      K-Mo/Al2O3 and K-CoMo/Al2O3 catalysts with various amount of potassium (up to 15wt. %) were synthesized using H3PMo12O40, CoCO3 and KOH. The catalysts were characterised by the following techniques: low-temperature N2 adsorption, Raman spectroscopy, temperature-programmed reduction, temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy. Synthesized catalysts were tested in hydrotreating of model fluid catalytic cracking gasoline containing 1000ppm of sulphur from thiophene and 36wt. % of n-hexene-1. It was found that potassium incorporation led to the strong changes in both physical-chemical characteristics and catalytic behaviour of sulphide catalysts. Using potassium favoured the growth of average slab length and sulphidation degree of metals with selective formation of CoMoS active phase. Addition of potassium also led to the partial poisoning of the active sites what resulted in decrease of catalyst activities compared with the reference Mo/Al2O3 and CoMo/Al2O3 samples. Olefin hydrogenation was more sensitive to potassium than thiophene hydrodesulphurization what resulted in the growth of the dependence of selectivity factor on potassium content in the catalysts. Obtained results allowed us to suppose that potassium partially inserts in sulphide slabs with changing the nature of active sites and probably with formation of new type of active “KCoMoS” sites.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Sulfur elimination by oxidative desulfurization with titanium-modified
           SBA-16
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Lorena P. Rivoira, Verónica A. Vallés, Brenda C. Ledesma, María V. Ponte, María L. Martínez, Oscar A. Anunziata, Andrea R. Beltramone
      TiO2-modified mesoporous SBA-16 and titanium-substituted mesoporous SBA-16 were developed and tested in the oxidative desulfurization (ODS) of dibenzothiophene prevailing in liquid fuel. Pure TiO2 was used as reference. The titania-based catalysts were characterized by chemical analysis, XRD, EDX and TEM. The titanium state as tetrahedral (in Ti-SBA-16 sample) or octahedral (in TiO2/SBA-16 sample) coordination surrounding in the silicate matrix was determined by XPS, UV–vis DRS, FTIR, Raman and XANES. We assessed the impact exerted on performance of different reaction variables, including (nature and amount of the active catalytic species, phase system, molar ratio of oxidant H2O2 and DBT, reaction temperature, nature of the substrate and reuse of catalysts). In addition, we carried out a kinetic study and the activation energy was determined. We achieved 90% of S removal from a 0.2wt.% dibenzothiophene solution at 60°C in less than 1h of reaction. The best catalytic results are obtained with high exposed surface of nanometric TiO2 species of TiO2/SBA-16 sample. The activated catalyst is very active in ODS reaction and can be reused four times with no loss in activity.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Characterization and catalytic performance of Co-Mo-W sulfide catalysts
           supported on SBA-15 and SBA-16 mechanically mixed
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): M.A. López-Mendoza, R. Nava, C. Peza-Ledesma, B. Millán-Malo, R. Huirache-Acuña, P. Skewes, E.M. Rivera-Muñoz
      A group of hydrodesulfurization (HDS) catalysts, based on transition metal sulfides (Co-Mo-W) and supported on mechanically-mixed mesoporous silicas (SBA-15 and SBA-16), have been synthesized and characterized by physicochemical methods (DRS-UV–vis, Micro Raman spectroscopy, XRD, SEM, HRTEM, EDS and catalytic activity). It has been demonstrated that the use of a mixture of silicas with two different porous structures has an advantage with respect to the use of the SBA-15 and SBA-16 separately for the preparation of supported catalysts for hydrodesulfurization reactions of refractory sulfur compounds, such as dibenzothiophene. This is because the presence of different porous structures has a positive effect over the diffusion processes of the precursors of the active phases on the support, and the whole result is a higher catalytic activity for the HDS reactions of dibenzothiophene, even more than that of the commercial catalyst used as a comparative model; this activity is also related with the stage of the synthesis process in which the mixture is done.
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      PubDate: 2016-05-15T09:02:08Z
       
  • New approach to active sites analysis of molybdenum-containing catalysts
           for hydrodesulfurization and hydrodenitrogenation based on inverse
           problem, fractal and site-type analyses
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Masatoshi Nagai, Nguyen Thanh Tung, Yasutaka Adachi, Kentaro Kobayashi
      A new approach to the active sites of Mo-containing catalysts for hydrodesulfurization and hydrodenitrogenation was studied by three methods, i.e., the inverse problem, fractal and site-type analyses. The distribution of the active sites of the sulfided and nitrided Mo/Al2O3 catalysts was studied based on the inverse problem using the Fredholm integral equation. The two active sites of the nitrided Mo/Al2O3 catalyst have a distribution involving the reaction rate and population; one site for a fast rate and large population and the other site for a slow rate and small population. The fractal analysis was applied to the morphology of the Mo nitride and the reactivity for the carbazole hydrodenitrogenation and related to the Mo0 or Moδ+ species. The fractal dimension of the Mo nitride surfaces was calculated to be from 2.02 to 2.60 and estimated the two active sites for the hydrogenation and denitrogenation. These sites were related to the Mo3+of γ-Mo2N from the XPS analysis. The active sites for the hydrodesulfurization of 4,6-dimethyldibenzothiophene on a sulfided NiMo/Al2O3 catalyst were discussed based on the site-type analysis. A third active site of the sulfided NiMo/Al2O3 catalyst was proposed for the simultaneous desulfurization and hydrogenation from 4,6-dimethyldibenzothiophene to 3,3-dimethylbicyclohexyl as well as the two active sites for the hydrogenation to 3-methylcyclohexyltoluene and the desulfurization to 3,3-dimethylbiphenyl.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Reactions analysis during the synthesis of pseudo-boehmite as precursor of
           gamma-alumina
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Gilberto Toledo-Chávez, Juan-Carlos Paniagua-Rodríguez, Juan Zárate-Medina, Rafael Maya-Yescas
      Pseudo-boehmite is the best precursor during synthesis of gamma alumina, because only the removal of water by calcination at about 447°C is required. The control of operating variables during synthesis of pseudo-boehmite: the supersaturation of the solutions is a factor of special importance, additionally the pH, temperature, impurities and nature of the reagents [3,4]. Ensure purity of this material and these variables determine the morphology, texture and it structures of the precipitate. Therefore, it is relevant to follow phenomena that occur during synthesis, in order to predict yield and quality of the final product. In this work, synthesis of pseudo-boehmite was developed by the method of precipitation, using industrial grade aluminum sulfate supersaturated solution and concentrated ammonium hydroxide (28%) as reactants; this known method was improved decreasing reaction temperature below the boiling point of ammonia. Temperature control of the reactant medium was reached by data acquisition and automatic manipulation of the heating medium. It is shown that operating the reactor at isothermal conditions ensures the final quality of the pseudo-boehmite produced.
      Graphical abstract image

      PubDate: 2016-05-15T09:02:08Z
       
  • Photodegradation of phenol using reconstructed Ce doped Zn/Al layered
           double hydroxides as photocatalysts
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): M. Suárez-Quezada, G. Romero-Ortiz, V. Suárez, G. Morales-Mendoza, L. Lartundo-Rojas, E. Navarro-Cerón, F. Tzompantzi, S. Robles, R. Gómez, A. Mantilla
      ZnAlCe layered double hydroxides (LDH) with different content of Ce (3.5, 5.0 and 10.0%mol) were successfully synthesized in one step by the co-precipitation technique. The partial incorporation of cerium into the layers of the material can be appreciated in the XRD diffraction patterns, showing some deformation in the crystallographic direction (110) of the ZnAlCe LDHs. In the samples calcined at 400°C, the UV–vis-DRS study showed a shift of the absorption edge toward the blue region of the spectra as a result of the cerium incorporation to the ZnAl LDH; the analysis of XPS confirms the co-existence of Ce4+ and Ce3+ in the ZnAlCe LDHs. The photodegradation and mineralization of phenol under UV irradiation was remarkably improved in the sample containing 5%mol of Ce. A mechanism where cerium in the layered material promotes the separation of the photogenerated electron–hole pairs is proposed. In this mechanism, Ce4+ acts as electron scavenger, facilitating the electron transfer toward adsorbed O2 and an accumulation of holes, increasing the generation of radicals OH.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Investigation of co-promotion effect in NiCoMoS/Al2O3 catalysts based on
           Co2Mo10-heteropolyacid and nickel citrate
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): A.V. Mozhaev, P.A. Nikulshin, Al.A. Pimerzin, K.I. Maslakov, A.A. Pimerzin
      Ni(Co) x -Co2Mo10/Al2O3 catalysts with various (Co+Ni)/(Co+Ni+Mo) atomic ratio (from 0.17 to 0.45) and constant Mo loading (10wt.%) were synthesised using decamolybdodicobaltate heteropolyacid (Co2Mo10HPA) and cobalt or nickel citrate. The catalysts were characterised using N2 physisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy and tested in the hydrodesulphurisation (HDS) of dibenzothiophene (DBT). It was found that adding the Co(Ni) citrate to Co2Mo10/Al2O3 catalyst significantly altered the active phase morphology. The average slab length increased from 3.0 to 4.1nm in Co x -Co2Mo10/Al2O3 catalysts and to 3.6nm in Ni x -Co2Mo10/Al2O3 counterparts. The average stacking number of the MoS2 crystallites grew from 1.4 to 2.0 with loading the Co or Ni. Increasing the Co content in the Co x -Co2Mo10/Al2O3 catalysts decreased the Co percentage in the CoMoS phase and led to the growth of Co fraction in cobalt sulphide. With the increase of Ni content in Ni x -Co2Mo10/Al2O3 catalysts the Ni percentage in the NiCoMoS phase decreased from 47 to 25rel.% and the Co percentage in the NiCoMoS phase was constant and equal to ∼62rel.%. For both series of the catalysts, activity in DBT HDS passed through maximum at 0.33 of the atomic ratio (Co+Ni)/(Co+Ni+Mo). Ni x -Co2Mo10S/Al2O3 catalysts indicated higher rate constants in DBT HDS than Co x -Co2Mo10S/Al2O3 counterparts at the same metal content. It was concluded that Ni1-Co2Mo10/Al2O3 sample with minimal Ni/Mo ratio had mixed Ni-Co-Mo sites with high turnover frequencies values.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Role of the Si/Al molar ratio and pH in NIW/MCM41-Al2O3 catalysts for HDS
           of DBT
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): G. Hernández Cedeño, R. Silva-Rodrigo, A. Guevara-Lara, J.A. Melo-Banda, A.I. Reyes de la Torre, F. Morteo Flores, A. Castillo-Mares
      This research presents a series of catalytic supports of MCM41 modified with γ-Al2O3 with a Si/Al molar ratio of 10, 25 and 50. These materials were impregnated with Ni+W solutions at pH 7 and pH 9, respectively and were evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction. In order to modify the low acidity of MCM41, its surface acidity was modified by incorporation of alumina content in the supports. The sol–gel incorporation method of Al2O3 to the structure of the MCM41 did produce changes in the characteristic of hexagonal arrangement of mesoporous materials. The symmetries of the materials were determined through UV–vis where the octahedral and tetrahedral nickel species were found. By Raman, monotungstate (WO4) and polytunsgtate (W12O40 8−) species were observed. The HDS of DBT showed that in the NiW/AMS50 catalyst impregnated at pH 9 presents the highest reaction rate. And in the case of the catalysts impregnated at pH 7 the highest reaction rate was achieved by the NiW/AMS10 catalyst. The selectivity was mainly oriented to the production of biphenyl (BP). The low catalytic activity was attributable to low formation NiWS species responsible for the HDS activity.
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      PubDate: 2016-05-15T09:02:08Z
       
  • CoNiMo/Al2O3 catalysts for deep hydrotreatment of vacuum gasoil
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): O.V. Klimov, K.A. Nadeina, P.P. Dik, G.I. Koryakina, V.Yu. Pereyma, M.O. Kazakov, S.V. Budukva, E.Yu. Gerasimov, I.P. Prosvirin, D.I. Kochubey, A.S. Noskov
      Trimetallic Co-Ni-Mo catalysts with different Co and Ni content (Co3Ni0, Co1.8Ni1.2, Co1.5Ni1.5, Co1.2Ni1.8 and Co0Ni3) were studied. Catalysts were characterized by HRTEM, XPS, EXAFS and XANES methods. It was shown that all catalysts contain metals preferentially in the form of sulfide active component with the structure that is similar to Co-Mo-S phase. Co-Mo and Ni-Mo catalysts contain active component in the form of Co-Mo-S and Ni-Mo-S phases respectively. Trimetallic catalysts were shown to contain mixed Ni-Co-Mo-S phases. Catalytic tests showed that the catalyst with 1.8% Co, 1.2% Ni and 10% Mo has the highest activity in hydrotreating of VGO. The highest activity of the catalyst is proposed to be provided by the formation of mixed Ni-Co-Mo-S phase.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Optimization of hydrocracker pilot plant operation for Base Oil production
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Nilesh Chandak, Abraham George, Adel Al Hamadi, Mikael Berthod
      This paper describes the hydrocracker pilot plant operations to produce Un-Converted Oil (UCO) selective for Base Oil production while achieving the middle distillate quality. This test was carried out to optimize feed and product quality for the commercial Base Oil unit to produce high viscosity index (VI) lube oil. The main objective of this experiment was to assess the performance of the hydro-cracking (HC) catalyst at different conversion levels between 50wt% and 70wt% and evaluate the quality of the Base Oil (BO) that would be produced in the commercial unit. For the test, fixed bed reactor was packed with commercial HC catalyst with pre-treatment hydro-treating (HT) catalyst upstream. The process parameters and product yields were studied by varying the HC reactor temperature. Then, hydrocracker products i.e. total liquid product (TLP) were collected and distilled into distillates and UCO. Special emphasis was given to the UCO quality with respect to the conversion so that it can produce desired Base Oil grades of Group-II (Gr II) and Group-III (Gr III). The experimental results have shown that it is possible to produce the Base Oil on specifications even at lower conversion up to 50wt%. Details of hydrocracker pilot plant design, catalyst, operations and study results are discussed.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Effect of pore size distribution (PSD) of Ni-Mo/Al2O3 catalysts on the
           Saudi Arabia vacuum residuum hydrodemetallization (HDM)
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Tingting Liu, Linqing Ju, Yasong Zhou, Qiang Wei, Sijia Ding, Wenwu Zhou, Xiujuan Luo, Shujiao Jiang, Xiujuan Tao
      To study the effect of pore size distribution (PSD) of Ni-Mo/Al2O3 catalysts on the hydrodemetallization (HDM) activity, catalysts with different PSD were prepared using activated carbon and ammonium bicarbonate as pore-expanding agents and the HDM reaction was carried out in a high pressure trickle-bed reactor and Saudi Arabia vacuum residuum as the feedstock. The catalysts showed good activity of removing metal nickel (Ni) and vanadium (V) when they contain 10–20nm pores, but the catalysts with both 10–20 and >100nm pores have higher activity of removing metal V. The effect of PSD on the removal of different metal compounds were also studied by analyzing different metal compounds distribution in its hydrotreated products. Both Ni and V compounds of small molecular size in the methanol extract and middle molecular size in the dimethylformatmide (DMF) extracts can be easily removed on the catalysts. However, most of the large molecular V and Ni compounds in the toluene extracts were the most resistant to be removed in the vacuum residuum hydrodemetallization. Large molecular V compounds in the toluene extracts can be hydrodemetallized effectively on the catalysts with macropore size (>100nm) distribution. While catalysts with mesopore size distribution (10–20nm) shows a higher HDNi activity for the large molecular Ni compounds in the toluene extracts. Catalyst with both 10–20 and >100nm pore size distribution would be more appropriate for the Saudi Arabia vacuum residuum HDV and HDNi.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Application of Monte Carlo techniques to LCO gas oil hydrotreating:
           Molecular reconstruction and kinetic modelling
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Maria Lopez Abelairas, Luis P. de Oliveira, Jan J. Verstraete
      The increasing environmental constraints on oil products leads to the need for developing accurate models in order to predict the detailed performances of refining processes. In the current study, a stochastic two-step procedure using Monte Carlo techniques is applied to and validated on the hydrotreating of Light Cycle Oil (LCO) gas oils. In the first step, a mixture of molecules representative of the LCO gas oils is generated using a molecular reconstruction method termed SR-REM. Subsequently, the Stochastic Simulation Algorithm (SSA) is applied to simulate the evolution of the mixture composition during hydrotreating. The results show that an accurate representation of eleven different LCO gas oils was obtained by the application of the molecular reconstruction method. The hydrotreating simulations of three LCO gas oils at different operating conditions showed a good agreement with the experimental data obtained at laboratory scale. The current stochastic procedure is demonstrated to be a valid tool for the reconstruction of the composition of LCO gas oils and the simulation of the hydrotreating process.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Hydrocracking of the crude oil from thermal pyrolysis of municipal wastes
           over bi-functional Mo–Ni catalyst
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Junhui Li, Hui Xia, Qian Wu, Zhonghua Hu, Zhixian Hao, Zhirong Zhu
      Bi-functional Mo–Ni/SiO2–Al2O3 catalyst was prepared by loading bimetal Ni–Mo over large porous and acidic SiO2–Al2O3 substrate via impregnation–precipitation–calcination–sulfurization procedure. Highly dispersed NiO clusters were loaded with urea as a precipitator. The catalytic performance for the hydrocracking of the crude oil from thermally pyrolysis of municipal solid wastes was investigated in a fixed bed reactor. It is found that SiO2–Al2O3 composites with the mid-acidity and large pores were more suitable as the substrate than Al2O3 and Al2O3–Y(Y zeolite). Mo–Ni/SiO2–Al2O3 catalyst with 8wt% Mo and 14wt% Ni showed the higher reactivity and higher yield of fuel oil. Moreover, its hydrocracking reactivity could be further improved by partial sulfurization of Ni and Mo. Besides, the bi-functional Mo–Ni/SiO2–Al2O3 showed a good stability, and the deactivated catalyst could be easily regenerated by on-line combustion. Under the optimized conditions of 10MPa, WHSV 0.3h−1 and 698K, the conversion of pyrolysis oil was up to 86% with 66% yield of fuel oil, greatly better than a commercial hydrocracking catalyst. The overall hydrocracking refinement converts most of the olefin, acid, ketones and poly-aromatic presented in the pyrolysis oil into alkanes, alcohols, and alkyl-aromatics, with a significant decrease of N and S contents as well as viscosity.
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      PubDate: 2016-05-15T09:02:08Z
       
  • The enhancement on the waste management of spent hydrotreating catalysts
           for residue oil by a hydrothermal–hydrocyclone process
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Jian-Ping Li, Xue-Jing Yang, Liang Ma, Qiang Yang, Yan-Hong Zhang, Zhi-Shan Bai, Xiang-Chen Fang, Li-Quan Li, Yue Gao, Hua-Lin Wang
      Nowadays, the disposal of spent catalysts caused growing concerns on the environmental status, human health and industrial safety. The non-regenerable catalysts were either sent to metal reclaimers or disposed of in commercial landfills. The de-oiling and the following mechanical (hydraulic) separation are essential operations, which will minimize the amount of the spent catalysts as well as control the toxic substances deposited on the used catalysts. In the present study, a hydrothermal–hydrocyclone process was proposed to enhance the management of the waste catalyst for residue oil hydro-treating. Under the optimal conditions, the removal efficiencies of the contaminated hydrocarbons for the artificial and real system were 93.5% and 70.3%, respectively. The enhancement of de-oil was originated from the self-rotation behavior of the catalyst particles. The rotation speed was estimated to be ∼6870rad/min by using the high-speed digital imaging and the numeric calculation. The application of hydrocyclone and the design process can also be used for the treatment of other solid wastes including contaminated soil, oily sludge and so forth. Moreover, it indicated that on the basis of the throughout understanding on the flow characteristics, the traditional operational equipment could be well manipulated in the treatment of environmental pollution.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Direct production of high octane gasoline and ULSD blend stocks by LCO
           hydrocracking
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): Chong Peng, Xinlu Huang, Xuezhi Duan, Zhenmin Cheng, Ronghui Zeng, Rong Guo, Xiangchen Fang
      Hydrocracking of light cycle oil (LCO) is of great scientific and industrial importance to obtain high quality of gasoline and diesel. In this work, a novel LCO hydrocracking technology (FD2G) was proposed, and three kinds of hydroprocessing catalysts (i.e., FC-14, FC-24 and FC-26) were tested under different pilot-scale operational conditions and/or types. All the three catalysts are found to be active for direct production of high octane gasoline and ultra low sulfur diesel (ULSD) blend stocks, and the FC-24 catalyst is the most active and selective toward production of high octane gasoline. The quality of gasoline and diesel products is highly sensitive to pressure and operation type. Furthermore, the FC-24 catalyst was also tested in a large-scale industrial plant. It is found that the yield of gasoline blend stock reaches 30–50wt%, the octane number of gasoline is 91–94 and the sulfur content is less than 10μg/g; the cetane number of diesel blend stock increases 10–14 units in comparison to the feed stock, and the sulfur content is less than 10μg/g.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Hydroprocessing of hydrocracker bottom on Pd containing bifunctional
           catalysts
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): P.P. Dik, O.V. Klimov, I.G. Danilova, K.A. Leonova, V.Yu. Pereyma, S.V. Budukva, D.D. Uvarkina, M.O. Kazakov, A.S. Noskov
      Bifunctional catalysts Pd/ASA-Al2O3, Pd/Y-ASA-Al2O3, Pd/Beta-ASA-Al2O3, Pd/ZSM-23-ASA-Al2O3 were prepared. Catalysts were characterized by FTIR of adsorbed CO, nitrogen adsorption and CO chemisorption. Average sizes of palladium particles in the catalysts were found to be 1.2–2.9nm. Zeolite-based catalysts contained stronger Brønsted acidic sites than amorphous silica-alumina (ASA) based catalyst Pd/ASA-Al2O3. Catalysts were tested in hydroconversion of hydrocracker bottom (HCB). Hydrocracking activities of Pd/Y-ASA-Al2O3 and Pd/Beta-ASA-Al2O3 catalysts were found to be significantly higher than that of Pd/ASA-Al2O3 and Pd/ZSM-23-ASA-Al2O3 catalysts. Conversion of 80% of HCB was achieved for catalysts with zeolites beta and Y at 250°C. It was found that selectivity to middle distillates increases in following order: Pd/ZSM-23-ASA-Al2O3 <Pd/Beta-ASA-Al2O3 <Pd/Y-ASA-Al2O3 <Pd/ASA-Al2O3. The highest yield of middle distillates was achieved for Pd/ASA-Al2O3 catalyst at 370°C. Ratio of hydroisomerization to hydrocracking activity was found to increase in the following order of catalysts: Pd/Y-ASA-Al2O3 ≤Pd/ASA-Al2O3 <Pd/Beta-ASA-Al2O3 <Pd/ZSM-23-ASA-Al2O3. Middle distillate with pour and cloud points of −61.5 and −62.5°C, respectively, was obtained at 240°C with 31.3wt.% yield using Pd/Beta-ASA-Al2O3 catalyst.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Catalysts based on amorphous aluminosilicates for selective hydrotreating
           of FCC gasoline to produce Euro-5 gasoline with minimum octane number loss
           
    • Abstract: Publication date: 1 August 2016
      Source:Catalysis Today, Volume 271
      Author(s): K.A. Nadeina, O.V. Klimov, V.Yu. Pereima, G.I. Koryakina, I.G. Danilova, I.P. Prosvirin, E.Yu. Gerasimov, A.M. Yegizariyan, A.S. Noskov
      The method for preparation of Co–Mo catalysts for one-stage hydrotreating of full FCC gasoline fraction is proposed. The main characteristic of the catalysts is the use of the supports based on amorphous aluminosilicate. Catalysts were characterized with nitrogen adsorption-desorption, HRTEM and XPS methods. It was shown that all catalysts containing aluminosilicates have similar textural characteristics and contain Co-Mo-S phase with similar morphology. The IR CO data indicate that sulfided catalysts contain different acid sites with the predominance of weak Lewis acid sites and Brønsted acid sites with the strength of 1190 kJ/mol. Catalysts were tested in hydrotreating of model fuel and full FCC gasoline fraction. It was shown that presence of amorphous aluminosilicates in catalysts results in the increase of catalytic activity in reactions of olefin isomerisation. Significant contribution of olefin isomerization reactions results in the prevention of octane number loss while high activity hydrodesulfurisation maintains.
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      PubDate: 2016-05-15T09:02:08Z
       
  • Catalyst synthesis by continuous coprecipitation under micro-fluidic
           conditions: Application to the preparation of catalysts for methanol
           synthesis from CO2/H2
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Laetitia Angelo, Maria Girleanu, Ovidiu Ersen, Christophe Serra, Ksenia Parkhomenko, Anne-Cécile Roger
      A new method of synthesis based on micro-fluidic continuous coprecipitation has been used to prepare CuO-ZnO-ZrO2 catalyst. The catalytic behavior was then investigated for CO2 hydrogenation into methanol and compared with a CuO-ZnO-ZrO2 catalyst prepared by classical coprecipitation and with the same amount of Cu0 (30%). The novel synthesis method allows a better repeatability and homogeneity of the catalyst which leads to the best methanol productivity of 486gMeOH kgcata −1 h−1 at 280°C under 50bar and a GHSV of 10,000h−1.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Direct dimethyl ether synthesis from synthesis gas: The influence of
           methanol dehydration on methanol synthesis reaction
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Farbod Dadgar, Rune Myrstad, Peter Pfeifer, Anders Holmen, Hilde J. Venvik
      Direct dimethyl ether (DME) synthesis from synthesis gas is studied with regard to potential effects of methanol dehydration on methanol formation and copper-based catalyst performance. For this, the influence of the operating conditions (space velocity, temperature, pressure, time-on-stream and syngas composition) on activity, selectivity and stability of the catalyst was studied and compared for methanol synthesis and direct DME synthesis. The advantage of the direct over the two-step DME synthesis is apparent at conditions where syngas conversion to methanol is thermodynamically limited. However, under the applied operating conditions, results suggest that combining methanol synthesis and dehydration has a negative effect on the methanol formation kinetics. The origin of the observed phenomena is investigated by varying dehydration catalyst and by introducing dehydration products (DME and water) into the methanol synthesis feed. Choice of the solid acid catalyst does not seem to affect methanol formation, and DME is also found to be practically inert over the methanol synthesis catalysts. Water injection, on the other hand, led to a significant decrease in the methanol synthesis rate. Thus, formation of an additional amount of water through methanol dehydration might be an explanation for the lower methanol formation rate in the direct DME synthesis.
      Graphical abstract image Highlights

      PubDate: 2016-05-03T10:33:27Z
       
  • Dry reforming of methane with carbon dioxide over NiO–MgO–ZrO2
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): J. Titus, T. Roussière, G. Wasserschaff, S. Schunk, A. Milanov, E. Schwab, G. Wagner, O. Oeckler, R. Gläser
      NiO–MgO–ZrO2 catalysts were synthesized via a melt impregnation technique on a zirconia support with equimolar amounts of Ni and Mg in the range of 2–35mol%. The catalysts were characterized by TPDA, TPR, PXRD, TEM and EDX. The catalysts are basic in nature and contain both tetragonal and monoclinic zirconia. After impregnation, Ni and Mg are homogeneously distributed over the zirconia support in oxidic form. After reduction of the composite system, metallic Ni is highly dispersed on the support together with a solid solution of NiO–MgO present. The prepared NiO–MgO–ZrO2 catalysts show a high activity in the dry reforming of methane at 1123K and atmospheric pressure. At high Ni and Mg contents, the catalysts are subject to severe coking leading to pronounced deactivation. From TEM investigations, a coking mechanism is proposed including the growth of filamentous carbon followed by formation of graphitic carbon, partly encapsulating metallic Ni particles. An optimum stability can be achieved in a small compositional corridor with Ni and Mg contents of 8–20mol%. In this composition range, the presence of MgO leads to a suppression of carbon formation, especially when compared to Ni supported on Mg-free zirconia. According to their activity and stability depending on the Ni- and Mg-contents, the catalysts were assigned to three categories: (I) low activity and high stability, (II) high activity and some stability and (III) high activity, but low stability.
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      PubDate: 2016-05-03T10:33:27Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270




      PubDate: 2016-05-03T10:33:27Z
       
  • Degradation of β-O-4 model lignin species by vanadium Schiff-base
           catalysts: Influence of catalyst structure and reaction conditions on
           activity and selectivity
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Heather J. Parker, Christopher J. Chuck, Timothy Woodman, Matthew D. Jones
      In the pursuit of value-added products from the degradation of the abundant aromatic biopolymer lignin, homogeneous catalysis has the potential to provide a mild, selective route to monomeric phenols. Homogeneous vanadium catalysts have previously been shown to effectively cleave dimeric β-O-4 model lignin compounds, with selectivity for CC or CO cleavage, or benzylic oxidation, depending on the ligand structure and oxidation state of the metal. In this study, a systematic kinetic investigation was undertaken in order to gain further understanding of the role of ligand structure and reaction conditions on the activity of vanadium Schiff-base catalysts towards a non-phenolic β-O-4 model lignin dimer, and the selectivity of these species towards CO bond cleavage. Catalytic activity was found to be increased by the addition of bulky, alkyl substituents at the 3′-position of the phenolate ring, whereas electron-withdrawing substituents were found to dramatically reduce activity irrespective of their size. Selective depolymerization of a phenolic β-O-4 dimer was also achieved.
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      PubDate: 2016-05-03T10:33:27Z
       
  • One-pot synthesis and recovery of fatty acid methyl esters (FAMEs) from
           microalgae biomass
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Daniel R. Nelson, Sridhar Viamajala
      We report a scalable method for recovery of cellular lipids and subsequent conversion to products. When in situ transesterification was performed at high solid loadings (>20%(w/w)) by reacting microalgal biomass in acidified methanol (containing 5%(v/v) H2SO4), the released FAMEs were produced at sufficiently high concentrations such that their solubility limit in the reaction medium was exceeded. As a result, the FAMEs spontaneously formed a separate phase lighter than methanol that could be directly recovered without solvent extraction. Further, FAME production rates were easily predicted, even in concentrated biomass slurries, by models derived from fundamental reaction kinetics. Our results also suggest that un-reacted methanol and catalyst, when recovered, could be reused in subsequent reactions. Thus, this “one-pot” process represents a viable method for production of biodiesel from algal biomass since this approach (1) eliminates costs associated with co-solvent (e.g., hexane) use, recovery and storage, (2) is easily scalable by virtue of the reaction not being constrained by mass transport limitations, and (3) facilitates processing of concentrated biomass slurries that would reduce reactor volumes and minimize reactor and handling costs.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Fe2O3–TiO2 core–shell nanorod arrays for visible light
           photocatalytic applications
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Kun Yao, Pradip Basnet, Henry Sessions, George K. Larsen, Simona E. Hunyadi Murph, Yiping Zhao
      By using the glancing angle deposition technique and post-deposition annealing, Fe2O3–TiO2 core–shell nanorod arrays with specific crystalline states can be designed and fabricated. The Fe2O3–TiO2 core–shell samples annealed at temperatures greater than 450°C formed α-Fe2O3 and anatase TiO2, and showed higher catalytic efficiency for the degradation of methylene blue (MB) under visible light illumination when compared with pure anatase TiO2 or α-Fe2O3 nanorod arrays. Solar conversion of carbon dioxide and water vapor in the presence of Fe2O3–TiO2 core–shell nanorod arrays was also investigated. Carbon monoxide, hydrogen, methane, and methanol along with other hydrocarbons were produced after only several hours’ exposure under ambient sunlight. It was determined that the core–shell structure showed greater efficiency for solar CO2 conversion than the pure TiO2 nanorod arrays.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Kinetics of Fischer-Tropsch synthesis on supported cobalt: Effect of
           temperature on CO and H2 partial pressure dependencies
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Kamyar Keyvanloo, Steven J. Lanham, William C. Hecker
      Kinetic data were measured for Fischer-Tropsch Synthesis (FTS) on a cobalt catalyst supported on silica-modified alumina at various partial pressures of CO and H2 and at four different temperatures (210, 220, 230, and 240°C). The data were sufficient to determine power law rate expressions at each of the four temperatures which indicate that the dependence of rate on PH2 increases with increasing temperature while the rate coefficient for PCO decreases with temperature going from positive order (+0.3) at 210°C to negative order (−0.6) at 240°C. Several mechanisms were explored and Langmuir–Hinshelwood (LH) rate models derived in an attempt to explain the data trends. Traditional FT rate expressions have a denominator term, KCO*PCO which, since the denominator is squared in LH expressions, can allow for an overall negative order PCO dependence. However, since KCO is the equilibrium constant for the adsorption of CO, its value decreases with increasing temperature which causes the overall PCO dependence to become more positive with increasing temperature instead of more negative. In this work we propose a mechanism based on parallel hydrogen-assisted mechanistic pathways that leads to a LH model with the denominator term, k’CO*PCO where k’CO is effectively an activated rate constant instead of an equilibrium constant and therefore increases with increasing temperature instead of decreasing. This model, which fits the data extremely well, also explains the presence of atomic carbon on the surface of the catalyst.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Sono-assisted alkaline pretreatment of sugarcane bagasse for cellulosic
           ethanol production
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Giselli Torres da Silva, Luana Marcele Chiarello, Esther Miranda Lima, Luiz Pereira Ramos
      The sono-assisted alkaline pretreatment of sugarcane bagasse was optimized using a central composite design in which the glucose recovery after enzymatic hydrolysis was used as the response function. Cellic® CTec3 (Novozymes) and Thermossac® Dry (Lallemand) were used for enzymatic hydrolysis and fermentation, respectively. The best performance was achieved at 70°C with 140W of sonication power using 0.125g of NaOHg−1 of dry biomass, yielding a total glucose recovery of 95.8wt% in relation to the total glucan content of the original material. The fermentation efficiency of the best substrate hydrolysate was 91.4%, whereas lower values of 87.1 and 80.0% were obtained for steam-exploded and sono-assisted alkali-washed steam-exploded cane bagasse, respectively. In addition, when the glucan recovery of each pretreatment method was taken into account, the total C6 cellulosic ethanol production from the sono-assisted alkali-washed cane bagasse was 20.4 and 40.6% higher than that of the other two pretreatment technologies, respectively.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Pt on Fecralloy catalyses methane partial oxidation to syngas at high
           pressure
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Cristian Neagoe, Daria C. Boffito, Zhenni Ma, Cristian Trevisanut, Gregory S. Patience
      μ-Gas-to-Liquids technology (μ-GTL) can potentially reduce natural gas that is flared throughout the world. Integrating syngas production (at high pressure) together with Fischer–Tropsch in the same vessel addresses both investment costs and operating costs challenges related to μ-GTL. Pt on a Fecralloy woven metal support effectively oxidizes methane in the presence of O2/Ar mixtures. Both CO and H2 selectivity are higher over the Fecralloy compared to either a commercial Pt-gauze or a Pt/Rh gauze at 900°C and 20bar. The catalyst activity is stable over 1h but the 80–300nm Pt particles agglomerate and form popcorn shape particles that are as large as 1150nm.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Power-law kinetics of methanol synthesis from carbon dioxide and hydrogen
           on copper–zinc oxide catalysts with alumina or zirconia supports
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Kilian Kobl, Sébastien Thomas, Yvan Zimmermann, Ksenia Parkhomenko, Anne-Cécile Roger
      Kinetics of methanol synthesis from carbon dioxide and hydrogen were studied on two catalysts, a copper–zinc oxide–alumina catalyst (CuZA) and a copper–zinc oxide–zirconia (CuZZ) catalyst. Although both catalysts show similar turnover frequencies for the methanol synthesis reaction, CuZZ is more selective for methanol synthesis because the reverse water gas shift reaction occurs more slowly on this catalyst. The results of the catalytic tests were modeled with power-law equations which highlight the strong positive impact of hydrogen partial pressure on methanol synthesis activity and selectivity. The comparison of the experimental results with thermodynamic equilibrium allows separating thermodynamic and kinetic driving forces.
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      PubDate: 2016-05-03T10:33:27Z
       
  • New trends in the development of heterogeneous catalysts for
           electrochemical CO2 reduction
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Bijandra Kumar, Joseph P. Brian, Veerendra Atla, Sudesh Kumari, Kari A. Bertram, Robert T. White, Joshua M. Spurgeon
      The electrochemical conversion of CO2 into energy-rich fuels and chemicals has gained significant interest as a potential strategy for simultaneously mitigating increasing global CO2 concentration and effectively storing intermittent renewable energy from sources such as solar and wind. This process recycles CO2, permitting a carbon-neutral, closed-loop of fuel combustion and waste CO2 reduction to help prevent a rising concentration of this greenhouse gas in the atmosphere. At the same time, intermittent electricity generation can be stored in an energy-dense, portable form in chemical bonds. However, the stability of CO2 makes its conversion kinetically challenging, generally requiring a large overpotential, and thus the efficiency of electrochemical CO2 reduction is strongly dependent on the activity and selectivity of the cathodic electrocatalyst. In this review, we discuss the current state-of-the-art of unconventional heterogeneous catalysts with a focus on activity and product selectivity, even if the CO2 reduction reaction mechanism remains uncertain. Various emerging approaches to enhance the yield of specific products and the overall rate of reaction will also be addressed. Finally, prospects for the development of next-generation catalysts will be discussed.
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      PubDate: 2016-05-03T10:33:27Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269




      PubDate: 2016-05-03T10:33:27Z
       
  • Contents list
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269




      PubDate: 2016-05-03T10:33:27Z
       
  • Preface
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Hongfei Lin, Elizabeth J. Biddinger, Calvin Mukarakate, Mark Nimlos, Haichao Liu



      PubDate: 2016-05-03T10:33:27Z
       
  • A coupled low temperature oxidative and ionic liquid pretreatment of
           lignocellulosic biomass
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Samira Vasheghani Farahani, Yong-Wah Kim, Constance A. Schall
      An integrated pretreatment strategy consisting of a room temperature alkaline oxidation step coupled with ionic liquid (IL) incubation enables effective lignocellulosic biomass pretreatment at low temperatures (50°C). The IL, 1-ethyl-3-methyl-imidazolium acetate (EMIM-Ac), was used in pretreatment of a lignocellulosic hardwood feedstock, poplar. Glucose and xylose yields for 24h enzyme hydrolysis of pretreated poplar were measured to assess the efficacy of this pretreatment strategy. The proposed strategy resulted in high hydrolysis yields at a low enzyme loading of 9.5 filter paper units per gram of glucan. The low IL incubation temperatures were found to reduce undesired cellulose acetylation reactions.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Lewis acid-catalyzed depolymerization of soda lignin in supercritical
           ethanol/water mixtures
    • Abstract: Publication date: 1 July 2016
      Source:Catalysis Today, Volume 269
      Author(s): Burcu Güvenatam, Erik H.J. Heeres, Evgeny A. Pidko, Emiel J.M. Hensen
      The depolymerization of lignin model compounds and soda lignin by super Lewis acidic metal triflates has been investigated in a mixture of ethanol and water at 400°C. The strong Lewis acids convert representative model compounds for the structure-forming linkages in lignin, namely α–O–4, 5–O–4 (C–O–C ether bridge), and α–1 (methylene bridge). Only the 5–5′ C–C linkage in biphenyl was unaffected under the given reaction conditions. Full conversion of soda lignin was achieved without char formation. Lignin was converted into a wide range of aliphatic and aromatic hydrocarbons. Ethanol was involved in the alkylation of the lignin depolymerization products. These alkylation reactions increased the product yield by inhibiting repolymerization of the products. The resulting organic phase consisted of aliphatic hydrocarbons (paraffins and olefins), aromatic hydrocarbons (extensively alkylated non-oxygenated mono-aromatics, mainly alkylbenzenes as well as mono-aromatic oxygenates, mainly phenolics), condensation products (mainly naphthalenes) and saturated oxygenates (ketones and carboxylic acids). Although complete product analysis was not possible, the data suggest that the dominant fraction of lignin was converted into monomeric units with a small fraction with molecular weights up to 650g/mol.
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      PubDate: 2016-05-03T10:33:27Z
       
  • Deactivation study of CuCo catalyst for higher alcohol synthesis via
           syngas
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Yanzhang Yang, Xingzhen Qi, Xinxing Wang, Dong Lv, Fei Yu, Liangshu Zhong, Hui Wang, Yuhan Sun
      Changes in catalytic performance and catalyst structural evolution during the deactivation of the CuCo/TiO2 model catalyst for higher alcohol synthesis via syngas were investigated. The catalytic activity decreases continuously with time-on-stream, although there is no obvious change in total alcohol selectivity. Meanwhile, the products shift gradually to low carbon number, and the chain growth probabilities of both alcohols and hydrocarbons decrease with reaction time. Using ethane hydrogenolysis as the probe reaction, the catalytic activity also declines with time-on-stream, indicating the decrease in the number of surface metallic cobalt ensembles. To elucidate the structural evolution of the catalyst, the calcined, reduced, and used catalysts were analyzed by various techniques. The bulk crystalline phase of the calcined catalyst is CuCo composite oxide, with small CuO nanoparticles spreading on the catalyst surface. After reduction, the oxides are transformed into CuCo alloy and Cu nanoparticles. For the used sample, severe sintering occurs and CoxC forms on the catalyst surface, both of which reduce the number of surface Co atoms and leads to catalytic deactivation.
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      PubDate: 2016-05-03T10:33:27Z
       
  • On the role of the stability of functional groups in multi-walled carbon
           nanotubes applied as support in iron-based high-temperature
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Ly May Chew, Wei Xia, Hendrik Düdder, Philipp Weide, Holger Ruland, Martin Muhler
      The role of the stability of surface functional groups in oxygen- and nitrogen-functionalized multi-walled carbon nanotubes (CNTs) applied as support for iron catalysts in high-temperature Fischer–Tropsch synthesis was studied in a fixed-bed U-tube reactor at 340°C and 25bar with a H2:CO ratio of 1. Iron oxide nanoparticles supported on untreated oxygen-functionalized CNTs (OCNTs) and nitrogen-functionalized CNTs (NCNTs) as well as thermally treated OCNTs were synthesized by the dry impregnation method using ammonium ferric citrate as iron precursor. The properties of all catalysts were examined using X-ray diffraction, temperature-programmed reduction in H2, X-ray photoelectron spectroscopy and temperature-programmed oxidation in O2. The activity loss for iron nanoparticles supported on untreated OCNTs was found to originate from severe sintering and carbon encapsulation of the iron carbide nanoparticles under reaction conditions. Conversely, the sintering of the iron carbide nanoparticles on thermally treated OCNTs and untreated NCNTs during reaction was far less pronounced. The presence of more stable surface functional groups in both thermally treated OCNTs and untreated NCNTs is assumed to be responsible for the less severe sintering of the iron carbide nanoparticles during reaction. As a result, no activity loss for iron nanoparticles supported on thermally treated OCNTs and untreated NCNTs was observed, which even became gradually more active under reaction conditions.
      Graphical abstract image

      PubDate: 2016-05-03T10:33:27Z
       
  • Continuous selective oxidation of methane to methanol over Cu- and
           Fe-modified ZSM-5 catalysts in a flow reactor
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Jun Xu, Robert D. Armstrong, Greg Shaw, Nicholas F. Dummer, Simon J. Freakley, Stuart H. Taylor, Graham J. Hutchings
      The selective oxidation of methane to methanol is a key challenge in catalysis. Iron and copper modified ZSM-5 catalysts are shown to be effective for this reaction using H2O2 as the oxidant under continuous flow operation. Co-impregnation of ZSM-5 with Fe and Cu by chemical vapour impregnation yielded catalysts that showed high selectivity to methanol (>92% selectivity, 0.5% conversion), as the only product in the liquid phase. The catalysts investigated did not deactivate during continuous reaction, and methanol selectivity remained high. The effect of reaction pressure, temperature, hydrogen peroxide concentration and catalyst mass were investigated. An increase in any of these led to increased methane conversion, with high methanol selectivity (≥73%) maintained throughout. Catalysts were characterised using DR-FTIR, DR-UV-Vis and 27Al MAS-NMR spectroscopy.
      Graphical abstract image

      PubDate: 2016-05-03T10:33:27Z
       
  • Contents list
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270




      PubDate: 2016-05-03T10:33:27Z
       
  • Preface
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Nitin Kumar, Sivakumar Vasireddy, Devendra Pakhare



      PubDate: 2016-05-03T10:33:27Z
       
  • Fischer-Tropsch synthesis: Effect of solvent on the H2–D2 isotopic
           exchange rate over an activated nickel catalyst
    • Abstract: Publication date: 15 July 2016
      Source:Catalysis Today, Volume 270
      Author(s): Venkat Ramana Rao Pendyala, Wilson D. Shafer, Gary Jacobs, Burtron H. Davis
      The effect of solvent on the hydrogen-deuterium isotopic homomolecular exchange rate over a 26.4% Ni/Al2O3 catalyst was investigated using a plug flow reactor at room temperature (23°C) and at atmospheric pressure. In this study, two different molecular weight solvents were tested: n-pentane ( M W ¯ (average molecular weight)=72), and n-hexadecane ( M W ¯ =226). At dry (without addition of solvent) and n-pentane solvent addition conditions, similar amounts of H2 and D2 are consumed and the concentration of the HD produced is two times the consumption of H2 or D2. Thus, these conditions exhibited around 100% exchange with the formation of H2:HD:D2 having a 1:2:1 ratio. With n-hexadecane solvent, the initial exchange rate was approximately 45%, but the exchange rate decreased with time and reached a steady state rate after 60min on-stream. The lower exchange rate of the n-hexadecane solvent might be due to the limited mobility of reactant molecules in the liquid-filled pores of the catalyst. The exchange rate of the catalyst is decreased with increasing molecular weight and density of the solvent. An isotopic partitioning preference was not observed for the nickel catalyst under various co-fed solvents, and similar findings were observed in our previous work (Catalysis Letters 143 (2013) 1368–1373).
      Graphical abstract image

      PubDate: 2016-05-03T10:33:27Z
       
 
 
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