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Catalysis Today    [6 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0920-5861
     Published by Elsevier Homepage  [2556 journals]   [SJR: 1.283]   [H-I: 129]
  • Lignin extraction from Mediterranean agro-wastes: Impact of pretreatment
           conditions on lignin chemical structure and thermal degradation behavior
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): P. Manara , A. Zabaniotou , C. Vanderghem , A. Richel
      Three different types of Mediterranean, agro-industrial wastes (olive kernels, grape pomace/seeds, peach kernels), were subjected to two pretreatment processes, a chemical/organosolv and a physicochemical one. The organosolv process included lignocellulosic biomass treatment with formic acid/acetic acid/water (30/50/20, v/v%), for 3h at 107°C, while the physicochemical method was conducted by immersing the biomass in a water/ethanol (8/92, v/v%), H2SO4 0.32M, solvent and further exposing the slurry to microwave irradiation (maximum 250W) for 1/2h at 150°C. Both processes were evaluated regarding the achieved delignification and the purity of the extracted lignins. The effect of the pretreatment processes onto the structure and thermal decomposition behavior of the extracted lignins was investigated via FT-IR and TGA analysis, respectively. The objective of the research work was to investigate potential valorization routes for these biomass agro-residues in the context of a biorefinery, focusing on lignin extraction. The pretreatment results showed that the obtained lignins, derived from both procedures, were of high purity (>82wt%). Under the organosolv procedure, peach kernel delignification showed the maximum value (∼16wt%), while under microwave pretreatment, olive kernel delignification showed the maximum value (∼35wt%). Grape pomace/seeds appeared to be the most resistant in both treatments.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Hydroprocessing of rapeseed pyrolysis bio-oil over NiMo/Al2O3 catalyst
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Katarzyna Pstrowska , Jerzy Walendziewski , Rafał Łużny , Marek Stolarski
      Raw rapeseed bio-oil, bio-oil fraction boiling at the temperature over 120°C and bio-oil blend with non-desulfurized light gas oil fraction were submitted to hydrorefining studies. In this experiment use of NiMo/Al2O3 as the selected catalyst for pyrolysis oil hydrorefining was tested at mild process parameter sets: temperature (260–350°C), LHSV (0.5–2.0h−1) and 3MPa hydrogen pressure. The influence of hydrorefining kinetic parameters on the physicochemical properties as well as chemical composition of the obtained products was evaluated. It was found that raw rapeseed bio-oil is a difficult raw material for a one-step upgrading with the applied process parameters. Obtained oxygen, nitrogen and sulphur removal was 70.8, 21.1 and 33.3wt.%, respectively. Removal of low boiling bio-oil fraction and lowering of LHSV up to 0.5h−1 strongly improved hydroprocessing efficiency. The HDO, HDN and HDS process efficiency value of 77.3, 38.4 and 27.7wt.% was obtained respectively. At relatively high LHSV level (2.0h−1), mild temperature (320°C), and 3MPa hydrogen pressure, a satisfactory level of the blend hydrorefining was achieved. Hydrorefining products of bio-oil and light gas oil fraction blend fulfilled majority of fuel oil commercial requirements.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Catalytic hydrodeoxygenation (HDO) of phenol over supported molybdenum
           carbide, nitride, phosphide and oxide catalysts
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Sara Boullosa-Eiras , Rune Lødeng , Håkon Bergem , Michael Stöcker , Lenka Hannevold , Edd A. Blekkan
      The performance of titania-supported molybdenum carbide, nitride, phosphide and oxide catalysts was compared for catalytic hydrodeoxygenation (HDO) of phenol. Phenol was selected as a stable model component for lignin degradation products in fast pyrolysis bio-oil. The synthesis and formation path of the materials was evaluated by the use of complementary characterization techniques (XRD, TPR and TGA–MS). All the catalysts showed promising catalytic performance during testing in a fixed-bed reactor set-up at a temperature of 350°C and total pressure of 25bar, and the highest activity was achieved with 15wt% Mo2C/TiO2. A high selectivity towards benzene was observed with all catalysts. MoP supported on TiO2 showed the strongest tendency to aromatic ring hydrogenation and also a significant selectivity (10% level) towards methylcyclopentane, indicating contributions of acidic surface chemistry. Thus, Mo based materials are active and promising materials for establishing selectivity control in HDO of bio-oils.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Continuous catalytic hydrothermal gasification of algal biomass and case
           study on toxicity of aluminum as a step toward effluents recycling
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Mariluz Bagnoud-Velásquez , Martin Brandenberger , Frédéric Vogel , Christian Ludwig
      A novel process named SunCHem has been proposed to produce methane via catalytic hydrothermal gasification of microalgae [1–3]. The process is innovative because it is designed as a closed-cycle system with respect to water, nutrients and some of the CO2, which are recycled and reused for the growth of microalgae. However, this recycled hydrothermal input is a matter of concern because upon continuous operation, it may become enriched in potential toxicants for algae. This study concerns the investigation of (1) the continuous catalytic hydrothermal gasification of the microalgae Phaeodactylum tricornutum, and (2) the influence of aluminum on microalgae growth, as traces of this metal are expected in the hydrothermal effluent. Experiments with the algae P. tricornutum, demonstrated the technical feasibility of pumping algae slurry (6.5wt.%) through the continuous pilot plant with simultaneous gasification for several hours. The carbon gasification efficiency, CGas/CFeed, was ca. 31% at steady state. The catalyst was rapidly deactivated during the continuous gasification experiment, due to sulfur poisoning and coking. Concerning the study on the effect of soluble Al on freshwater microalgae, it was demonstrated that at alkaline conditions, the Al hydroxides had a negative effect on algae growth even at concentrations as low as 0.025mgL−1.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Sugars and sugar derivatives in ionic liquid media obtained from
           lignocellulosic biomass: Comparison of capillary electrophoresis and
           chromatographic analysis
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): S. Hyvärinen , J.P. Mikkola , D. Yu. Murzin , M. Vaher , M. Kaljurand , M. Koel
      Processing of woody lignocellulosic biomass, under heating in combination with ionic liquids (ILs) was studied in order to obtain simple (fermentable) sugars. Due to the new environmental challenges, finding greener ways to produce platform chemicals and/or bio-fuels has become a popular research area. Various industrial, pilot or laboratory scale technologies for the depolymerization or fractionation of lignocellulosic polysaccharides to monomers are known. One of the new, interesting, methods is to utilize ILs in biomass pre-treatment procedures with an aim to bypass other pre-treatment methods. Furthermore, in order even to initiate studies whether ILs can contribute to catalytic depolymerization, there has to be a robust way to analyze the IL-treated lignocellulosics. This is a major issue since woody samples that contain any salts such as ILs can indeed be quite challenging from the analytic point of view. The applied capillary electrophoresis was found to be an excellent analytical method providing substantial improvements compared to the earlier used chromatographic methods. In this work it was demonstrated that application of ILs, at elevated temperatures, contributes to hydrolysis and depolymerization of lignocellulose. The effect is time and temperature dependent: in harsh conditions sugars degrade but too low processing temperatures or short treatment times result in no meaningful effect. The formation of the degradation products of the monosaccharides is a good indicator of the harshness of the applied chemical conditions. Evidently, furfural and 5-(hydroxymethyl)furfural formed in rather short treatment times.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Task-specific ionic liquid for the depolymerisation of starch-based
           industrial waste into high reducing sugars
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Audrey Hernoux-Villière , Jean-Marc Lévêque , Johanna Kärkkäinen , Nicolas Papaiconomou , Marja Lajunen , Ulla Lassi
      Development of a simple route for the catalytic conversion of starch-based industrial waste (potato peels) and potato starch into reducing sugars was investigated in two ionic liquids for comparison – 1-allyl-3-methylimidazolium chloride [AMIM]Cl and 1-(4-sulfobutyl)-3-methylimidazolium chloride [SBMIM]Cl. Over a two hour period, a 20wt% solution containing up to 43% and 98% of reducing sugars at low temperature in aqueous [SBMIM]Cl was achieved for the starch-based waste and the potato starch, respectively. In addition, the use of microwave and low frequency ultrasound to perform the depolymerisation of the raw starch-based material was explored and compared with conventional heating processes.
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      PubDate: 2014-01-20T00:06:00Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223




      PubDate: 2014-01-20T00:06:00Z
       
  • Contents list
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223




      PubDate: 2014-01-20T00:06:00Z
       
  • Sustainable production of fuels/energy, materials and chemicals from
           biomass (UBIOCHEM-III)
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223




      PubDate: 2014-01-20T00:06:00Z
       
  • Acid catalysed alcoholysis of wheat straw: Towards second generation
           furan-derivatives
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): R.J.H. Grisel , J.C. van der Waal , E. de Jong , W.J.J. Huijgen
      The acid-catalysed alcoholysis of wheat straw has been studied in 95% methanol and 94% ethanol (w/w) in the presence of various amounts of H2SO4 and compared to the alcoholysis of wheat straw-derived organosolv pulp and commercially available celluloses. Substrate liquefaction and the product distribution were found to depend mainly on the temperature and the amount of H2SO4 added compared to the acid neutralisation capacity (ANC) of the substrate. The process was optimised for the one-step conversion of wheat straw into methyl glucosides, defined as the sum of α and β anomers. The maximum total methyl glucosides yield from wheat straw was 56mol-% based on initial glucan after 120min methanolysis at 175°C and 40mM H2SO4. Concurrently, furfural was formed at 40mol-% yield based on initial xylan. The solid residue consisted of mainly acid insoluble (pseudo)lignin, humins and minerals. Switching to ethanol resulted in a shift from glycosides to furfural, 5-(alkoxymethyl)-2-furfural and levulinates. Addition of MgCl2, as well as substituting H2SO4 by HCl led to poorer biomass liquefaction and lower glucosides yield presumably due to consumption of protons under the typical reaction conditions. Alcoholysis of delignified, cellulose-enriched pulp obtained via organosolv fractionation resulted in higher glucosides yields and more concentrated product streams, as higher glucan loadings are possible and undesired side-reactions are minimised. Furthermore, organosolv fractionation prior to alcoholysis allows for the separation and valorisation of the lignin fraction. The glucosides can be separated, e.g. by means of chromatography, and may be converted into furan building blocks, for example for the production of plastic precursors, such as 2,5-furandicarboxylic acid.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Preparation and characterization of Pt-modified Co-based catalysts through
           the microemulsion technique: Preliminary results on the
           Fischer–Tropsch synthesis
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): V. Montes , M. Boutonnet , S. Järås , M. Lualdi , A. Marinas , J.M. Marinas , F.J. Urbano , M. Mora
      The influence of the addition of small amounts of platinum (0.1–0.25% wt) to cobalt-based systems on Fischer–Tropsch synthesis was investigated. The solids were synthesized through microemulsion technique using TiO2 as the support. The best catalytic performance was achieved using Synperonic 13/6.5 as the surfactant. In all cases, the presence of platinum led to an increase in CO conversion which could be ascribed to the promotion of cobalt reducibility as evidenced by XPS. Moreover, the simultaneous reduction of cobalt and platinum precursors during synthetic procedure (ME1) was preferable to the consecutive one (ME2) probably as a result of a better Co–Pt interaction in the former case, as evidenced by TPR. TPR, Raman and XPS data also suggested that not only the presence of Co0 but also the appearance of Co–TiO2 interactions favor the catalytic performance and that in general those interactions are stronger for ME1 solids.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Effect of support composition on the activity of Pt and PtMo catalysts in
           the conversion of n-hexadecane
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Karolina Jaroszewska , Aleksandra Masalska , Dominika Marek , Jolanta R. Grzechowiak , Agnieszka Zemska
      The SiO2Al2O3 material and mesoporous molecular sieves of AlSBA-15 type described in this work were applied as the supports for the Pt and PtMo catalysts. Catalysts were synthesized by one step impregnation, i.e. Pt catalysts with 1wt.% of Pt as well as by two step impregnation, i.e. PtMo catalysts with 4–8wt.% of Mo followed by 1wt.% of Pt. The activity of the catalysts was investigated in n-C16 conversion (5MPa; 320–370°C; WSHV, 3.5h−1; H2:CH, 350:1Nm3/m3) and in n-C7 conversion (0.1MPa; 350–370°C; WHSV, 1h−1; H2:CH, 10:1mol/mol). The results have shown that at comparable reaction temperatures, i.e. 340–360°C the catalysts containing AlSBA-15 are more active than the catalysts supported on SiO2Al2O3. Among the PtMo/AlSBA-15 catalysts, the catalyst containing 8wt.% of Mo provides the highest selectivity towards i-C16 and the highest iso/n proportion within C10–C15 fraction together with the maintenance of a high conversion. SEM examinations of PtMo catalysts have shown that type of support influences Mo distribution; agglomerates of Mo phases are observed on the AlSBA-15 containing catalysts. It was postulated that the weaker Mo–support interactions and higher acidity in AlSBA-15 supported catalysts resulted in a more active and selective catalyst for hydroconversion of n-hexadecane.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Effect of metal loading on activity, selectivity and deactivation behavior
           of Pd/silica–alumina catalysts in the hydroconversion of
           n-hexadecane
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Francesco Regali , Leonarda Francesca Liotta , Anna Maria Venezia , Vicente Montes , Magali Boutonnet , Sven Järås
      Bifunctional catalysts consisting of palladium on amorphous silica–alumina with different metal loadings (0wt% to 1.2wt%) were compared in the hydrocracking/hydroisomerization of n-hexadecane. The reaction conditions were: pressure=30bar; temperature=310°C; hydrogen-to-hexadecane feed molar ratio=10. Metal loading was found to have a remarkable influence on the initial deactivation rate, which could be related to the formation of carbonaceous deposits. The dependence of activity on the metal–acid site ratio was the typical one for bifunctional hydrocracking where, after reaching a threshold value, the catalytic activity does not appreciably increase with increasing metal loading. On the Pd-containing catalysts, the methane space-time-yield showed a strong dependence on conversion, but no clear relationship with metal surface area, indicating that the formation of methane might not proceed by purely metal-catalyzed hydrogenolysis.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Aqueous phase reforming of xylitol over Pt-Re bimetallic catalyst: Effect
           of the Re addition
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Alexey V. Kirilin , Anton V. Tokarev , Haresh Manyar , Chris Hardacre , Tapio Salmi , J.-P. Mikkola , Dmitry Yu. Murzin
      The aqueous phase reforming (APR) of xylitol was studied in a continuous fixed bed reactor over three catalysts: Pt/Al2O3, Pt/TiO2 and Pt-Re/TiO2. The data obtained in the case of the monometallic Pt catalysts was compared to the bimetallic Pt-Re sample. The effect of Re addition on the catalyst stability, activity, product formation and selectivity toward hydrogen and alkanes was studied. The bimetallic catalyst demonstrated a higher selectivity to alkanes compared to the monometallic samples. The monometallic catalyst was more selective toward hydrogen formation. A plausible reaction scheme explaining differences in selectivity toward hydrogen and alkanes was proposed and discussed.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Combined fermentation for increasing efficiency of bioethanol production
           from Fusarium sp. contaminated barley biomass
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Grazina Juodeikiene , Darius Cernauskas , Daiva Vidmantiene , Loreta Basinskiene , Elena Bartkiene , Bronius Bakutis , Violeta Baliukoniene
      The work is aimed at increasing the efficiency of the processing of Fusarium sp. contaminated barley (Hordeum vulgare) grains to bioethanol. The commercial xylanase (Ecopulp TX-200A) in combination with amylolytic enzymes (Stargen™ 002) was used as a biocatalyst to improve the enzymatic degradation of polysaccharides in terms of ethanol yield. Furthermore, bacteriocins producing lactic acid bacteria (Lactobacillus sakei, Pediococcus acidilactici and Pediococcus pentosaceus) were used as biotool for decontamination of barley grains before fermentation. Different strains of yeasts (Kluyveromyces marxianus, Kluyveromyces marxianus var. bulgaricus and Saccharomyces cerevisiae) were applied for alcoholic fermentation. The highest ethanol yield, 86% of the theoretical based on the reducing sugar content, was obtained using the xylanase amount of 3450XUkg−1 grain in combination with biotools such as (i) the treatment of barley biomass with 20% LAB suspension and (ii) 10gL−1 K. marxianus var bulgaricus yeast. In all cases this biotreatment had a positive effect on the residue of the alcohol fermentation (dried distillers grains with solubles (DDGS)) as feed raw material: Decreased the deoxynivalenol (DON) content up to 45%. So, by selecting biocatalyst for non-starch polysaccharide conversion and LABs with antimicrobial effects in combination with yeast, the efficiency of the processing of Fusarium contaminated barley can be significantly increased: The biomass could be used for bioethanol production and DDGS—for feed. The results obtained in this study provide new possibilities for more effective and rational use of cereal resources for technical uses as well as for feed production.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Transesterification of short chain esters using sulfonic
           acid-functionalized hybrid silicas: Effect of silica morphology
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Maria Luisa Testa , Valeria La Parola , Anna Maria Venezia
      Sulfonic acid-functionalized hybrid silicas with different structure (amorphous, HMS, SBA-15) were synthesized by different methodologies, with a variable amount of organic moieties (propylSO3H). The obtained catalysts, characterized by X-Ray photoelectron spectroscopy, low angle X-Ray diffraction, N2 adsorption and acid capacity measurements, were tested in the transesterification reaction of short chain esters (from hexanoic to lauric ethyl ester). The optimized reaction was carried out under mild condition in the presence of 15% mol of the corresponding organic acid in order to reproduce a typical low-grade oil. A correlation between the catalytic activity of the materials and their acid capacities was found. The propyl-sulfonic SBA-15 catalyst presented the best performance in terms of activity and structural stability with no leaching of the sulfonic groups.
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      PubDate: 2014-01-20T00:06:00Z
       
  • The hydrolytic hydrogenation of cellulose to sorbitol over M (Ru, Ir, Pd,
           Rh)-BEA-zeolite catalysts
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Alina Negoi , Kostas Triantafyllidis , Vasile I. Parvulescu , Simona M. Coman
      Supported Ir, Pd, Rh and Ru catalysts were examined for the conversion of glucose and cellulose in water in the presence of hydrogen. The catalysts were prepared by incipient wetness impregnation of a BEA zeolite (SiO2/Al2O3 =21.6, Ssp =739m2/g) with acetylacetonate metal precursors. Among these catalysts, Ru-BEA was found to be the most active for the conversion of cellulose, while Ir-BEA was found to be the most selective for the formation of sorbitol. Thus, the highest yield to sorbitol was found in the presence of 3wt%Ru/BEA catalyst irrespective of the raw material nature (glucose or cellulose). It corresponded to a value of 22% for the conversion of the commercial cellulose, and of 72.8% for the conversion of glucose. The Ru-BEA catalyst was followed by the 3wt%Ir-BEA that led to a yield of 55.3% for glucose and 22% for cellulose but to a much higher selectivity, i.e. over 99.9% for glucose and 89.2% for cellulose. While the high selectivity of Ir to sorbitol was correlated with the d-band width of the metal, the high activity of Ru for the cellulose conversion was assigned to the generation of H+ and [Ru(H2O)5OH]2+ as Brønsted acids by Ru species in water. Finally, the addition of pure nanoscopic hydroxylated SnF4 to the 3wt%Ir-BEA catalyst led to a conversion of cellulose of almost 99% after only 3h with a selectivity to sorbitol of 72.5%.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Synthesis of different ZnO-supported metal systems through microemulsion
           technique and application to catalytic transformation of glycerol to
           acetol and 1,2-propanediol
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): V. Montes , M. Checa , A. Marinas , M. Boutonnet , J.M. Marinas , F.J. Urbano , S. Järas , C. Pinel
      Different systems consisting of diverse metals (Au, Pt, Pd, Rh) supported on ZnO (5% by weight) were synthesized through the microemulsion technique (ME) and tested for glycerol hydrogenolysis, the main products being hydroxyacetone (acetol) and 1,2-propanediol (1,2-PDO). The solids synthesized using sodium borohydride as the reducing agent (B series) had smaller particle sizes as compared to the use of hydrazine (H series) which, in turn, resulted in a better catalytic performance. This synthetic method allowed us to obtain similar metal particle sizes (2–4nm) for Pt, Pd and Rh solids in B series, whereas average gold metal particle was higher (>8nm) which probably accounts for Au-containing systems being inactive under our experimental conditions. Reactivity order followed the sequence Rh>Pt>Pd. A comparison of the systems synthesized in the present paper through ME technique with those obtained in a previous work through the deposition–precipitation process revealed a higher activity and selectivity to acetol for the former solids which could be related to the presence of surfactant. Moreover, results suggested that metal sites could participate not only in hydrogenation of acetol to 1,2-propanediol but also in the previous dehydration step of glycerol to acetol.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Aldol condensation of furfural and acetone over MgAl layered double
           hydroxides and mixed oxides
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Lukáš Hora , Vendula Kelbichová , Oleg Kikhtyanin , Oleg Bortnovskiy , David Kubička
      Liquid phase aldol condensation of furfural and acetone catalyzed by solid base catalysts (MgAl hydrotalcites and MgAl mixed oxides) has been investigated as a method to valorize short chain ketones obtainable from biomass pyrolysis for the production of higher-molecular-weight products usable as fuel components. The Mg/Al molar ratios of the investigated catalysts was varied in the range from 2 to 4 and their catalytic activity was tested at different reaction temperatures (20–100°C) using several activation methods. MgAl hydrotalcites were used either after calcination as mixed oxides or after subsequent contact with liquid water or steam as rehydrated materials. Both furfural-acetone condensation products, i.e. C8 and C13, were the desired products of aldol condensation reaction. Higher reaction temperature facilitated the dehydration step and enhanced the catalyst selectivity to both dehydrated products (C8 and C13). The best results were achieved with calcined catalyst sample having Mg/Al molar ratio equal to 3 at 100°C (>95% furfural conversion and >90% selectivity to the desired products). The selectivity to the main by-product, diacetone alcohol, did not exceed 5% in any experiment. The ex situ rehydration of the calcined samples resulted in catalysts with a significantly lower activity, except the catalyst with Mg/Al molar ratio equal to 2. On the other hand, in situ rehydration caused catalyst activity improvement only in the case of the sample with Mg/Al molar ratio 3.
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      PubDate: 2014-01-20T00:06:00Z
       
  • The role of catalysis in the synthesis of polyurethane foams based on
           renewable raw materials
    • Abstract: Publication date: 15 March 2014
      Source:Catalysis Today, Volume 223
      Author(s): Sylwia Dworakowska , Dariusz Bogdał , Federica Zaccheria , Nicoletta Ravasio
      In the last years growing attention is paid to environmental concerns with a special attention to bio- and renewable resources as feedstock for the chemical industry as well as to heterogeneous catalytic processes as tools for the elimination of wastes. This paper describes the results obtained in the application of vegetable oils stabilized through a selective hydrogenation process for the preparation of polyols and therefore in the synthesis of flexible polyurethane foams which are the most common and widely used among polyurethane materials. The influence of a different catalytic system on gelling and blowing reactions was studied and then properties of obtained foams were compared. It was found that the selection of catalytic system during preparation of polyurethane foams substantially influenced the properties of the final materials.
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      PubDate: 2014-01-20T00:06:00Z
       
  • Current situation of emerging technologies for upgrading of heavy oils
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Luis C. Castañeda , José A.D. Muñoz , Jorge Ancheyta
      With the increased production of heavy and extra-heavy crude oils, and the need to add them into the regular diet to refineries, there has been much interest for developing new technologies for upgrading those heavy materials. Traditional commercially available carbon rejection and hydrogen addition routes are still applicable for this purpose, however they have shown some limitations when the oil is heavier, which directly impact in the economy of the technology. Various emerging technologies have been reported in the literature, mainly in patents, which have been developed and tested at different scale and with a wide variety of heavy petroleum. The most important emerging technologies for upgrading of heavy crude oils are reviewed and discussed. Particular emphasis is put in a comparison with the available information. It is recognized that all the technologies have great opportunity to be applied commercially depending on the support that they receive by the petroleum companies.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Simulation of an industrial fixed-bed reactor with cocurrent downflow for
           hydrogenation of PYGAS
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Mixef Rojas , Susana Zeppieri
      A fixed-bed Reactor with cocurrent downflow operating in downward bubble flow regime for hydrogenation of pyrolysis gasoline (PYGAS) has been simulated. In order to model the reactor, suitable thermodynamic, hydrodynamic and reaction models were solved simultaneously. A set of ten hydrogenation reaction kinetics was considered, taking into account a cut of hydrocarbons C5–C11. It was demonstrated the importance of how the choice of a specific thermodynamic model may, or not, improve the results obtained, and how this may affect the prediction of the system. The use of Soave–Redlich–Kwong equation of state with the mixing rule of Panagiotopoulo-Reid modified by SimSci is the recommendation made to represent the vapor-liquid-equilibrium, reporting 3.4% AARD (average absolute relative deviation) in the hydrogen solubility in PYGAS. The model predicts the steady state conditions and it is validated by comparing the results with actual plant data under the following operating conditions: T inlet =366K, P inlet =5.03MPa, and (<0.001) molar of styrene in the reactor effluent. From simulation results, it is compared the predictions of the model with actual plant data, finding a good agreement between both, and showing AARD of 0.8% in the temperature profile and 9% in the composition of reactor effluent between ours results and the plant data.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Modeling on scale-up of an ebullated-bed reactor for the hydroprocessing
           of vacuum residuum
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Zhen-Min Cheng , Zi-Bin Huang , Tao Yang , Jian-Kun Liu , Hai-Long Ge , Li-Jing Jiang , Xiang-Chen Fang
      An ebullated reactor for heavy vacuum residuum (VR) hydroprocessing under a high hydrogen pressure of 15MPa and a high temperature of 425°C was simulated using a two-bubble class model. To account for the influence of the strong back-mixing of the liquid phase and the non-uniform distribution of the catalyst on the performance of the reactor, axial dispersions for the two phases are incorporated into the plug flow model. Based on the bench-scale experiments conducted in a reactor of 0.036m ID and 2.0m in height, scaling up of the reactor to an annual processing capacity of 1.0milliont of VR was proposed. To determine the optimal reactor dimension, a reactor of 3m ID and 36.86m in height and one with 4.5m ID and 16.38m in height are compared. It shows although the two reactors give very similar conversions as a CSTR reactor, the 3m ID reactor shows a higher gas–liquid mass transfer coefficient and a larger slurry circulation velocity than the 4.5m ID one, which suggests the 3m ID reactor is a better choice in the scale up.


      PubDate: 2013-12-07T00:04:32Z
       
  • Modeling the deactivation by metal deposition of heavy oil hydrotreating
           catalyst
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Ignacio Elizalde , Jorge Ancheyta
      Modeling the deactivation of heavy oil hydrotreating catalyst was carried out by using a pore plugging model. Experimental data were obtained at constant temperature of 385°C, pressure of 9.8MPa, LHSV of 0.25h and 5000scf H2/bbl oil. Kinetics was derived from experimental data collected at short times-on-stream (TOS) whereas data affected by pore plugging by metal deposition was obtained between 200 and 2200h TOS. The model employed was capable of predicting with confidence the profiles of diminution of metal removal (nickel and vanadium) at short and long values of time-on-stream.


      PubDate: 2013-12-07T00:04:32Z
       
  • Hydroxylated sol–gel Al2O3 as photocatalyst for the degradation of
           phenolic compounds in presence of UV light
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): F. Tzompantzi , Y. Piña , A. Mantilla , O. Aguilar-Martínez , F. Galindo-Hernández , Xim Bokhimi , A. Barrera
      Al2O3 was synthesized by the sol–gel method, dried at 100°C and annealed at 400, 500, 600 and 700°C, respectively. These materials were characterized and evaluated to be used as photocatalysts for the degradation of phenol in aqueous phase. Although Al2O3 is a well-known insulator, in the present study we show the feasibility of using Al2O3 synthesized by the sol–gel method as a catalyst for the photomineralization of hazardous organic molecules. The photocatalytic activity of these materials was higher than that of Degussa P-25 TiO2, and other commercial aluminas tested, particularly in the case of the sample of Al2O3 calcined at 400°C. The results of Nuclear Magnetic Resonance of solids (27AlMAS NMR) indicate that Al changes its coordination number during the calcination process. Rietveld refinement of the X-ray diffraction patterns denotes a notable hydroxylation in the Al2O3 structure, which was not removed by thermal treatments. Complementary spectroscopic studies (UV–Vis and FTIR) as well as the characterization of the textural properties are reported. It is proposed that UV irradiation of the hydroxylated Al2O3 induces an effective separation of the electron–hole pairs and hence, promotes the photodegradation of phenolic compounds.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Simulating vacuum residue hydroconversion by means of Monte-Carlo
           techniques
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Luís Pereira de Oliveira , Jan J. Verstraete , Max Kolb
      The present work focuses on the development of a novel methodology for the kinetic modeling of heavy oil conversion processes. The methodology models both the feedstock composition and the process reactions at a molecular level. The composition modeling consists of generating a set of molecules whose properties are close to those of the process feedstock analyses. This synthetic mixture of molecules is generated by a two-step molecular reconstruction algorithm. In its first step, an equimolar set of molecules is built by assembling structural blocks in a stochastic manner. In the second step, the mole fractions of the molecules are adjusted by maximizing an information entropy criterion. Once the composition of the feedstock is represented, the conversion process is simulated by applying, event by event, its main reactions to the set of molecules by means of a kinetic Monte Carlo (kMC) method. The methodology has been applied to hydroconversion of Ural vacuum residue and both the feed and the predicted effluents were favorably compared to the experimental yield pattern.


      PubDate: 2013-12-07T00:04:32Z
       
  • Unsteady-state kinetic simulation of naphtha reforming and coke combustion
           processes in the fixed and moving catalyst beds
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Andrey N. Zagoruiko , Alexander S. Belyi , Mikhail D. Smolikov , Alexander S. Noskov
      The work is dedicated to the construction of kinetics models for the naphtha reforming process and the adjacent process of catalyst regeneration by coke combustion. The proposed kinetic model for the reforming process is based on the use of common rate equations for the groups of similar reactions with account of difference in reaction rates for individual homologs within these groups by simple correlations with thermodynamic properties (first of all – with the values of Gibbs free energy) of individual reactions and by other simplification methods. Such approach gives the way to construct the kinetics models optimal from the point of view of compromise between accuracy and simplicity. The proposed naphtha reforming model is characterized with the high level of kinetic scheme detailization (62 individual and group reactants and 146 individual reactions), at the same it is rather simple and provides the accurate description of the experimental data using only 22 kinetic parameters. This model is thermodynamically consistent and provides accurate description of experimental data in a wide range of process parameters. Account of catalyst deactivation by coke deposition in the model gives the way to simulate transient reforming process performance both in fixed and moving catalyst beds. Kinetics of coke combustion for catalysts with moderate coke content (up to 3% mass) may described by simple kinetic equation with apparent reaction rate orders closed to unit for relative coke content and to 1/2 for oxygen. Demonstration simulations of naphtha reforming and coke combustion processes are presented.
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      PubDate: 2013-12-07T00:04:32Z
       
  • On the application of petroleum feedstock modeling techniques for
           developing molecule-based models of hydrocarbon conversion processes
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Anton Alvarez , Luis Carlos Castañeda , Jorge Ancheyta
      The design of hydrocarbon conversion processes currently demands more realistic modeling tools, with the capability of predicting product distribution at the molecular level. This requires a detailed molecular characterization, which generally is not available for complex feeds. The implementation of modeling techniques to simulate the molecular composition of petroleum feedstocks from routine analyses represents an alternative route towards molecule-based kinetic modeling. Nevertheless, generating a useful molecular representation depends heavily on the scope of the input analyses. This study aimed at verifying the requirements to construct a molecular representation that suits a detailed kinetic model, in terms of input data and model formulation. Two straight-run naphtha samples were selected as basis, in order to compare the simulated composition against gas chromatography data, and afterwards the analysis was extended to a light cycle oil. It was confirmed that it is possible to generate a synthetic mixture that behaves like the actual petroleum fraction in terms of bulk properties and even carbon number distributions. The comparison against gas chromatography data on the other hand, revealed that there are significant differences at the molecular level primarily due to the inability to predict all possible structural combinations of alkyl groups, which increases exponentially with the carbon number. For practical reasons then, it is proposed to work with a reduced set of chemically relevant species, built from a main core structure (e.g. an arrangement of aromatic or naphthenic rings) and a reduced set of alkyl branch configurations, rather than considering a vast number of structural combinations.


      PubDate: 2013-12-07T00:04:32Z
       
  • Composition of stacked bed for VGO hydrocracking with maximum diesel yield
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): P.P. Dik , O.V. Klimov , G.I. Koryakina , K.A. Leonova , V.Yu. Pereyma , S.V. Budukva , E.Yu. Gerasimov , A.S. Noskov
      Hydrocracking catalysts prepared by co-impregnation of three different supports with solutions containing Ni, Mo and citric acid were studied. Pure γ-Al2O3, 30% of zeolite Y/γ-Al2O3 and 70% of amorphous aluminosilicate ASA (Si/Al=0.9)/γ-Al2O3 were used as supports. All the catalysts were shown to contain the particles of Ni-Mo-S phase with similar morphology after liquid phase sulfidation by DMDS. The active component is uniformly distributed on γ-Al2O3 and ASA surface in NiMo/Al2O3 and NiMo/ASA-Al2O3 catalysts. The main amount of Ni and Mo is localized on γ-Al2O3 surface in NiMo/Y-Al2O3 catalyst while the main part of zeolite Y surface is free of supported metals. Testing of stacked beds, which comprise different prepared catalysts, in hydrocracking of vacuum gasoil showed that the NiMo/Al2O3 catalyst had the maximum selectivity to diesel fuel, but its activity was insufficient. Diesel fuel yield did not exceed 50wt.% for the stacked beds comprising NiMo/Y-Al2O3 independent on the process temperature. NiMo/ASA-Al2O3 had an optimal ratio of activity to selectivity for the production of diesel fuel and provided the diesel fuel yield by over 60wt.% at 400°C.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Supported on alumina Co-Mo hydrotreating catalysts: Dependence of
           catalytic and strength characteristics on the initial AlOOH particle
           morphology
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): O.V. Klimov , K.A. Leonova , G.I. Koryakina , E.Yu. Gerasimov , I.P. Prosvirin , S.V. Cherepanova , S.V. Budukva , V.Yu. Pereyma , P.P. Dik , O.A. Parakhin , A.S. Noskov
      The influence of different initial AlOOH boehmites on the mechanical strength, textural characteristics, and activity of diesel fuel hydrotreating catalysts has been studied. The morphology of the initial AlOOH particles was shown to have no significant influence on the composition and structure of the Co-Mo-S phase, although it does fully define the mechanical strength and textural characteristics of the catalysts. An optimal combination of high mechanical strength and catalytic activity, which depends on a texture of the catalyst, is attained using initial boehmite with a needle-shaped particle morphology and a particle size of 150nm×8nm×8nm.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Estimation of effective diffusion coefficient and its effect on
           effectiveness factor for HDS catalytic process: A multi-scale approach
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Mario E. Cordero , Reyna Natividad , Luis G. Zárate , J.A. Hernandez-Servin , Jesús Salas
      Effectiveness factors have great relevance in multiphase reactors modeling since they are the conventional way of incorporating the effects of intra-particle resistance reaction rate. This work determines the description level effect of catalytic pellet microstructure on mass and energy effective transport coefficients prediction, isothermal and no isothermal. For such a purpose some results about on evaluation of the effective diffusivity and conductivity with the methodology of volume averaging were applied. The obtained results along with a Langmuir–Hinshelwood/Hougen–Watson kinetic expression were applied to establish the concentration and temperature fields in a catalytic particle. The evaluation of concentration field and effectiveness factors were developed using two different models: pseudo- homogeneous mass and energy transport model for a catalytic particle with reaction in all domain, and heterogeneous mass and energy transport model with fluid-catalytic surface interphase reaction for a realistic porous structure model. The results show the differences in concentration and temperature profiles between both models and consequently in effectiveness factors. This could be ascribed to the form of evaluation of effective transport coefficients used in the pseudo-homogeneous model, and presumably to the simple shape of the unit cells used for the solution of the closure problem for the average transport equations with homogeneous reaction.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Electronic properties of unsupported trimetallic catalysts
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): A. Olivas , J. Antúnez-García , S. Fuentes , D.H. Galván
      It is well known that the catalytic activity that presents a particular sulfide depend upon the transition metal that it possesses and of its location in the periodic table. In order to gain insight into the origin of these trends in activity, on terms of extended Hückel method, were carried out calculations for trimetallic unsupported M–Mo–W–S (M=Ni, Co, Fe or Cu) sulfide catalysts. The results of these calculations were used to identify electronic properties, such as band structure, density of states and average net charge, which showed that exists a direct correlation with the catalytic activity of the transition metal sulfides. In addition, was observed that the promotion of (Mo–W)S2 precursors with M to form trimetallic M–Mo–W–S catalysts after sulfidation, increases the availability of electrons over the Fermi level, increasing the metallic character of the catalysts.
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      PubDate: 2013-12-07T00:04:32Z
       
  • New inverted cyclone reactor for flash hydropyrolysis
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): R. Galiasso , Y. González , M. Lucena
      Flash hydropyrolysis (that is, pyrolysis in a hydrogen atmosphere) is a term usually used to describe processes with reaction times of only several seconds or less. Flash hydropyrolysis is usually carried from atmospheric to 20MPa pressure. The majority of the available techniques for carrying out these processes have been developed in coal pyrolysis studies and recently extended to the pyrolysis of biomass. The use of inverted cyclone type reactor developed in the 80s by Summer, Briens and Bergougnoud, among others, provides the advantage of a short residence time and high efficiency in the separation of the solid, as well as that the feed does not need to be preheated to the high temperature required by the reactions. This paper presents the simulation model for the reactor with optimal geometry for pyrolysis of naphtha and biomass. Kinetics and fluid dynamics are discussed for both examples and then the effect of operating variables on yield and quality were simulated. The main characteristic of this type of reactor are discussed for the two examples. The results indicate that in both cases (naphta and pyrolysis) can design a suitable reactor autothermal (it does not require heating wall).


      PubDate: 2013-12-07T00:04:32Z
       
  • Catalyst deactivation pattern along a residue hydrotreating bench-scale
           reactor
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Pablo Torres-Mancera , Patricia Rayo , Jorge Ancheyta , Gustavo Marroquín , Guillermo Centeno , Fernando Alonso
      An atmospheric residue (312°C+) was hydrotreated in a bench-scale reactor. After shutdown, spent catalysts of the first bed of the hydrotreating reactor were sampled. A portion of the samples was regenerated. Both spent and regenerated catalysts were characterized by nitrogen physisorption and SEM-EDX. The type of coke deposited on spent catalysts was analyzed by DRIFT. The remaining catalytic activity was evaluated by thiophene HDS and cumene HDC. The profile of metals and coke depositions through the catalytic bed in fresh-basis was determined. The results showed that vanadium and nickel depositions decrease and carbon increases from top to bottom of the bed. It was found that both hard and soft coke amounts increases towards the bed outlet. A tendency of metals to deposit in pores of midsize and coke to fill big pores was observed. Around 25% of the fresh catalyst activity in thiophene HDS and cumene HDC remains in spent catalysts. These results match the values in the remaining of pore volume. Additionally, an enhancement of cumene HDC activity through the regeneration of spent catalysts was noticed.


      PubDate: 2013-12-07T00:04:32Z
       
  • Vacuum gas oil hydrocracking performance of bifunctional Mo/Y zeolite
           catalysts in a semi-batch reactor
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Reynald Henry , Melaz Tayakout-Fayolle , Pavel Afanasiev , Chantal Lorentz , Gregory Lapisardi , Gerhard Pirngruber
      A new approach has been developed to characterize bifunctional catalysts in a complex matrix of hydrotreated vacuum gas oil using a batch reactor test. Triphasic reactions were carried out in a reactor equipped with a stationary basket, hydrogen injection and products sampling systems. Bifunctional catalysts containing different relative amounts of alumina-supported NiMo sulfide and zeolite were tested at 400°C under 120 bars over different reaction times. The repeatability of the test conditions was validated and the lack of mass transfer limitations at phase interfaces was confirmed. Gas and liquid samples were analyzed by one and two-dimensional gas chromatography (GC×GC) respectively to obtain quantitative distributions of linear and branched paraffins, naphthenes and aromatics. The details of the products distribution provided by chromatography were explained using mechanisms of bifunctional catalysis. It has been established that the limiting step defining the total conversion is the scission of the hydrocarbon chains on acid sites of the zeolite. The increase of the molybdenum to zeolite ratio provided an improvement of middle distillate selectivity.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Carbon and metal deposition during the hydroprocessing of Maya crude oil
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Mohan S. Rana , J. Ancheyta , Sangram K. Sahoo , P. Rayo
      During the heavy oil hydroprocessing, a decrease in catalytic activity with time-on-stream (TOS), is due to the metal and carbon deposition on the catalysts. In this investigation, spent catalysts were obtained from the Maya heavy crude hydrotreating unit, as the processing conditions were close to the industrial practice. The catalysts were unloaded after considerable activity decrease, considering the initial activity as base activity. The spent catalysts were characterized by pore size distribution, SEM-EDS, TEM and 13C solid state NMR. Results indicate that catalysts were deactivated mainly due to the deposition of metal and carbon. The sources of deactivation were identified along with the location of foreign species by analyzing the deposited species on the spent catalysts. The nature of the coke and its compositions were derived from 13C CP/MAS and CP/MAS with dipolar dephasing NMR experiments. The wide range of analysis of spent catalysts specify that the catalyst pores were plugged during the heavy oil processing. The deactivation of catalysts were not only due to the carbon deposition but also due to the deposited metal sulfide (V x S y , Ni x S y ) over the existing (CoMoS) active sites. It appear from the results that considerable amount of deactivation is irreversible and non-regeneratable (i.e., metal deposition). Hence catalyst deactivation during heavy oil hydrotreating (HDT) is a function of metal and carbon deposition during time-on-stream. The metal deposition on spent catalysts, e.g. vanadium is on the surface, while Ni distributed deeper into the pore of the catalysts. The removal of Ni and V showed different behavior, which was attributed to an oxygen atom presence to vanadium and its influence on the vanadium porphyrin structure.


      PubDate: 2013-12-07T00:04:32Z
       
  • Dehydrocyclization of n-heptane over Pt catalysts supported on Al- and
           Si-promoted TiO2
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Gustavo Pérez López , Román Ramírez López , Tomás Viveros
      The effect of content of Si- and Al-promoted TiO2 catalysts in the dehydrocyclization of n-heptane was studied. The sol–gel method was used to prepare pure TiO2 and mixed oxides with 1%, 3% and 10% of Al2O3 and SiO2. The structure and surface characterization (XRD, N2 sorption, H2 chemisorption, NH3 uptake) revealed that the promoted cations were dispersed in the TiO2 lattice, modifying structural and surface properties of catalysts. Dehydrocyclization activity and toluene yields were useful test reaction to detect the effect of content of cations in both acidic and catalytic properties of promoted catalysts. Increase in the TOF was observed as a function of cation content, hand in hand with the increase of overall reaction rate and supported Pt dispersion. The effects in both catalytic activity and deactivation resistance could be explained by the metal-support contact theory, which relates the atomic coordination of promoters with changes in catalytic activity and chemisorption properties of Pt supported on TiO2.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Enhanced photoactivity for the phenol mineralization on ZnAlLa mixed
           oxides prepared from calcined LDHs
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): F. Tzompantzi , G. Mendoza-Damián , J.L. Rico , A. Mantilla
      ZnAlLa layered double hydroxides (La/Zn molar ratio of 0.005, 0.01 and 0.03) were synthesized by the co-precipitation method and calcined at 500°C. XRD patterns showed lamellar type materials in fresh solids (dried) and a diminishing basal parameter denoting the incorporation of La in the ZnAl LDH structure. At low content of La, XRD does not show the formation of La2O3, which become detectable only in the sample with high La content. After calcination, the formation of zincite was detected in the LDH, indicating the destruction of the lamellar structure. The Eg band of the sample with low content of La, calculated from the UV–Vis spectra, showed a shift to low energy, while for the samples with high content of La the Eg shift is displaced to high absorption energy. Evaluation of the photoactivity in the degradation of phenol using a low intensity UV–Vis lamp (254nm and 4400μW/cm2), showed the maximum values in phenol mineralization 88–66% with the ZnAlLa samples, in comparison to that obtained with the ZnAl oxide (48%). These results show that ZnAlLa mixed oxides prepared from the thermal treatment of ZnAlLa LDH are promising materials for an effective phenol mineralization.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Characterization study of NiMo/SiO2-Al2O3 spent hydroprocessing catalysts
           for heavy oils
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): C. Leyva , J. Ancheyta , L. Mariey , A. Travert , F. Maugé
      NiMo/SiO2-Al2O3 spent catalysts were obtained after the hydroprocessing of Maya crude oil in a fixed-bed up-flow reactor. The textural properties, metal content, carbon deposition and sulfide phase of spent catalysts were studied and compared with those of fresh catalysts. Scanning electron microscopy was used to study the deposit of nickel and vanadium, and the total metal content was determined by atomic absorption. The sulfide phase was analyzed with the use of infrared spectroscopy technique. Moreover, the catalytic activity of spent catalysts was evaluated with cumene hydrocracking and compared with the catalytic activities of fresh catalysts. The characterization results show that the silica-alumina NiMo catalysts are more sensitive to metal deposition than carbon deposition because of their porous structure which provokes pore mouth plugging and the decrease of the NiMoS active sulfide phase. The results show that optimizing the catalyst resistance to deactivation requires a trade-off between the support acidity and macro-mesoporosity.


      PubDate: 2013-12-07T00:04:32Z
       
  • Effect of the amount of citric acid used in the preparation of NiMo/SBA-15
           catalysts on their performance in HDS of dibenzothiophene-type compounds
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Miguel Ángel Calderón-Magdaleno , Juan Arturo Mendoza-Nieto , Tatiana E. Klimova
      In the present work, NiMo catalysts supported on SBA-15 were prepared with the addition of different amounts of citric acid (CA) in the impregnation solutions. The aim of this study was to inquire into the effect of the amount of citric acid on the activity and selectivity of the NiMo/SBA-15 catalysts in deep hydrodesulfurization (HDS). Catalysts were prepared by coimpregnation of Ni and Mo species from acidic aqueous solutions containing citric acid without further adjusting the solution's pH. The amount of citric acid used in the catalyst preparation was varied from CA:Mo molar ratio 0.5 to 2.0. In addition, a reference NiMo/SBA-15 catalyst was prepared without citric acid. After the impregnation, catalysts were dried (100°C, 6h) and calcined (500°C, 4h). The prepared catalysts were characterized by nitrogen physisorption, small-angle and powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), high resolution transmission electron microscopy (HRTEM) and tested in simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a batch reactor at 300°C for 8h. XRD, DRS and TPR characterizations showed that Ni and Mo oxide species were well dispersed in all catalysts prepared with CA. In contrast, a NiMoO4 crystalline phase was detected by XRD in the reference NiMo/SBA-15 catalyst prepared without citric acid. Addition of citric acid to the impregnation solutions used for the catalyst preparation also resulted in an increase in the degree of sulfidation and in the dispersion of catalytically active MoS2 phase (elemental analysis, HRTEM). In accordance with this, HDS activity of the NiMo catalysts prepared with the addition of citric acid resulted to be significantly higher than that of the reference NiMo/SBA-15 sample for both sulfur-containing compounds tested (DBT and 4,6-DMDBT). It was found that the optimum amount of citric acid, which allows achieving the highest catalytic activity, corresponds to CA:Mo molar ratio equal to 1. Further increase in the amount of citric acid resulted in a slight decrease in the HDS activity. Regarding selectivity, addition of small amounts of CA, in general, resulted in an increase of the hydrogenation ability of the NiMo/SBA-15 catalysts. However, some differences in the selectivity of the catalysts were observed with different amounts of citric acid used.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Simultaneous estimation of kinetics and catalysts activity during cracking
           of 1,3,5-tri-isopropyl benzene on FCC catalyst
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Gladys Jiménez-García , Hugo de Lasa , Rafael Maya-Yescas
      Catalytic cracking reactions, performed on commercial catalysts, are difficult to follow because of the simultaneous deactivation of the catalyst as consequence of coke deposition on catalyst surfaces during cracking of hydrocarbon molecules. In this work, a model for catalyst deactivation in terms of fouling because of blockage of micropores of the catalyst is used to estimate activity independently of reaction rates; later cracking kinetic rates of a model compound are estimated. It was found that the expected low energy of coke deposition reactions dominate the process, however these reactions are not easy to estimate a priori because of the definition of coke as a lumped entity. A comprehensive model of a CREC-Riser simulator Reactor is developed in order to consider mass balances for each specific operating condition. Three temperatures and two contact times are used to evaluate frequency factors and activation energies of the reactions that take place during the catalytic cracking of 1,3,5-tri-isopropyl benzene in two cases, with catalyst coming from an industrial unit and with catalyst pre-coked in laboratory. A methodology to separate activity and apparent kinetics in this kind of reactions is proposed.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Stabilized Ni-based catalysts for bio-oil hydrotreatment: Reactivity
           studies using guaiacol
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): M.V. Bykova , D.Yu. Ermakov , S.A. Khromova , A.A. Smirnov , M.Yu. Lebedev , V.А. Yakovlev
      The development of catalysts possessing high activity and high stability in the catalytic hydrotreatment of pyrolysis oils (bio-oil) is of great interest. NiCu bimetallic catalytic systems are very attractive for use in hydrotreatment process due to their low price and high activity in hydrogenation, hydrodeoxygenation and hydrocracking reactions. In the present work P-/Mo-containing agents were used to modify bimetallic catalytic system NiCu/SiO2–ZrO2 to improve its mechanical strength and stability in acidic medium. The modified catalysts were tested in hydrodeoxygenation (HDO) of guaiacol—a well-known model compound of bio-oil. HDO process has been carried out in an autoclave at 320°С, 17MPa initial hydrogen pressure, reaction time 1h. It was shown that phosphorus and molybdenum addition to the catalysts composition results in the decrease of guaiacol conversion and deoxygenation degree. The yield of undesirable gaseous reaction products (mainly methane) and coking of the catalyst were lower for the modified catalysts in contrast to the initial NiCu/SiO2–ZrO2 system. The catalysts treatment in glacial acetic acid at 118°C showed that modification by P and Mo gives a significant improvement of catalysts stability in acidic medium (mass loss decreases from 53 wt.% to 1 wt.%). Also a significant improvement of bulk crushing strength has been observed for PMo-modified samples (from 0.5MPa to 1.2MPa).
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      PubDate: 2013-12-07T00:04:32Z
       
  • Deep hydrotreating diesel fractions for low-sulfur fuel production using
           gas-phase and trickle bed reactors systems operating in parallel
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Roberto Galiasso Tailleur
      A new hydrotreating process scheme for upgrading cracked feedstock was developed to produce diesel fraction low in sulfur and aromatics from a combination of heavy straight-run gas oil and heavy-cycle oil feeds. The process uses a high-temperature, high-pressure stripper (HPHTS) to separate the feed into a gas phase, which is hydrotreated with a WNiPd/Al2O, catalyst, and in a liquid phase which is hydrotreated with a WNiPd/TiO2Al2O3 catalyst. Heavy diesel and product were fractionated, and then naphtha, jet fuel, diesel and 350°C+ cuts separated in three sub-fractions that were analyzed by GC–FID, GC–AED, GC–MS, and 1H NMR and 13C NMR techniques. In some cases sub-fractions are separated in sub-sub-fractions by elution on a particular column for detail analyses of species. The catalysts were characterized to determine their physical properties, bulk, and on-surface composition before and after deactivation reactions. The activity and selectivity of these catalysts, fresh and deactivated, were tested with synthetic feed and with heavy diesel at different operating conditions. Two long-term tests have been performed at different temperatures with the new catalysts. The experimental data was used to adjust the kinetic and deactivation constant of a model previously developed. The effect of recycle is also evaluated in pilot plant studies. A simulation program was used to compare the performance during a cycle length of the new hydrotreating system with that of the commercial process, which uses a MoNi/Al2O3 catalyst to obtain diesel with 10ppm of sulfur. Differences in catalysts, operating conditions of the reactors, and the main reactions occurring during the hydrotreating are discussed.
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      PubDate: 2013-12-07T00:04:32Z
       
  • Wastewater treatment of methyl methacrylate (MMA) by Fenton's reagent and
           adsorption
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Perla Tatiana Almazán-Sánchez , Ivonne Linares-Hernández , Verónica Martínez-Miranda , Violeta Lugo-Lugo , R.M. Guadalupe Fonseca-Montes de Oca
      Oxidation-adsorption treatments were applied to improve the biodegradability of wastewater from the manufacture of acrylic resins with methyl methacrylate (MMA). MMA wastewater has an extremely complex composition, with a chemical oxygen demand (COD) concentration of 651.25-g O2/L, total organic carbon (TOC) concentration of 227.86g/L, N-NH3 concentration of 48.80g/L, and 352,500-PtCo units. In this study, the effects of operating parameters that include the Fenton reagent dosage, the initial pH, and the reaction time of the treatment efficiencies of the Fenton oxidation process were observed. The improvement in the biodegradability was attributed to the removal of ammonium and organic pollutants from the wastewater, which was confirmed using infrared spectroscopy. After this process, adsorption of organic matter from wastewater was also studied; kinetic and equilibrium adsorption studies were performed to evaluate the effect of the contact time and pH. Pseudo-second-order kinetics represented the experimental data well, and Langmuir and Freundlich isotherm models were tested to represent the data. The maximum adsorption capacity obtained was q m =1.15g/g for TOC and 11.65g/g for COD at optimum conditions. The removal efficiencies of the Fenton adsorption treatment were 96% of color, 58% of TOC, and 60% COD.
      Graphical abstract image

      PubDate: 2013-12-07T00:04:32Z
       
  • Study of acid–base properties of supported heteropoly acids in the
           reactions of secondary alcohols dehydration
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): J.G. Hernández-Cortez , Ma. Manríquez , L. Lartundo-Rojas , E. López-Salinas
      The dehydration of secondary alcohols (propan-2-ol and 4-methylpentan-2-ol) was catalyzed by heteropolyacids (HPAs) supported on different solids. Catalysts prepared with 20wt.% of HPAs were calcined at 400°C and characterized by X-ray diffraction, Raman spectroscopy, XPS and N2 adsorption measurements. Stability of the Keggin structure of supported HPAs and changes in textural properties of catalysts were analyzed. The catalytic conversion of alcohols to olefins and ethers has been studied over the catalysts prepared. All catalysts presented activity in the reactions, but only molybdophosphoric acid supported on ZrO2 (MoP-Z) showed selectivity in the formation of acetone and methyl isobutyl-ketone (MIBK). Catalysts with tungstosilicic acid (WSi) and Tungstophosphoric acid (WP) were active in the formation to DIPE. The acid–base properties of the catalysts play a key role in route of the reaction mechanism.


      PubDate: 2013-12-07T00:04:32Z
       
  • Optimization of biodiesel production from sunflower oil by
           transesterification using Na2O/NaX and methanol
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Sandra Luz Martínez , Rubi Romero , Reyna Natividad , Javier González
      In this work, response surface methodology was used to optimize the conditions for the transesterification of sunflower oil with methanol, using Na2O supported on NaX faujasite zeolite as catalyst. By experimental design a quadratic polynomial equation was obtained for biodiesel yield. Multiple regression analysis and verification experiments confirmed the validity of the predicted model. The studied variables were reaction temperature (40, 50 and 60°C), catalysts weight base oil (5, 7.5 and 10wt%), Na content (5.5, 7.5, 10 and 11.5wt%) and methanol:sunflower oil molar ratio (4:1, 5:1 and 6:1). Results from the optimization study showed that reaction temperature and molar ratio methanol:oil can be optimized. Catalyst characterization was carried out by scanning electron microscopy, atomic absorption, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption and basicity determination by Hammett method. Biodiesel with highest methyl esters content (99.3%) was obtained with the catalyst with 10% Na content, at 60°C, 6:1 methanol:sunflower oil molar ratio and 10wt% catalyst concentration. The produced biodiesel was found to fulfill the specifications of the European Norm UNE-EN 14214 regarding viscosity, flash point and acid value.
      Graphical abstract image

      PubDate: 2013-12-07T00:04:32Z
       
  • Contents list
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222




      PubDate: 2013-12-07T00:04:32Z
       
  • International Symposium on Advances in Hydroprocessing of Oil Fractions
           (ISAHOF 2013)
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Jorge Ancheyta , Carolina Leyva , Gilbert F. Froment



      PubDate: 2013-12-07T00:04:32Z
       
  • Biodiesel production with nanotubular sodium titanate as a catalyst
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222
      Author(s): Patricia Hernández-Hipólito , Montserrat García-Castillejos , Elena Martínez-Klimova , Nohemí Juárez-Flores , Antonio Gómez-Cortés , Tatiana E. Klimova
      Sodium titanate nanotubes (STNT) with a chemical formula Na2Ti3O7·nH2O were synthesized and tested as a heterogeneous catalyst in the transesterification of soybean oil with methanol. The catalyst was characterized by N2 physisorption, powder XRD, scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM) and CO2 temperature-programmed desorption (CO2-TPD). It was found that the prepared catalyst had nanotubular structure, high sodium content (10.3wt.%) and attractive textural characteristics (surface area around 200m2/g and total pore volume of 0.61cm3/g). The influence of the catalyst's loading, methanol to oil molar ratio, reaction time and temperature on the biodiesel yield was investigated. High biodiesel yields (97–100%) were obtained with the STNT catalyst at 8h reaction time at methanol reflux temperature with 1–2wt.% of the catalyst and 40:1 methanol:oil molar ratio. Increase in the reaction temperature to 100–120°C had a positive effect on the biodiesel yield. In this case, 99–100% yields were obtained with a lower catalyst loading (∼1wt.%) and methanol to oil molar ratio (20:1). In addition, it was found that the STNT catalyst does not require high temperature thermal pre-treatment (activation) before the transesterification reaction. The reuse of the same catalyst in the transesterification reaction three times showed a decrease of about 10% in the catalytic activity.
      Graphical abstract image

      PubDate: 2013-12-07T00:04:32Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: March 2014
      Source:Catalysis Today, Volumes 220–222




      PubDate: 2013-12-07T00:04:32Z
       
 
 
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