for Journals by Title or ISSN
for Articles by Keywords
help

Publisher: Elsevier   (Total: 2563 journals)

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

  First | 19 20 21 22 23 24 25 26     

The end of the list has been reached. Please navigate to previous pages.

  First | 19 20 21 22 23 24 25 26     

Journal Cover Catalysis Today
   [8 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0920-5861
     Published by Elsevier Homepage  [2563 journals]   [SJR: 1.283]   [H-I: 129]
  • Facile fabrication of a highly active shell–core LaNi(Mg,
           Al)O3@Mg–Al catalyst for ethanol steam reforming
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Guangming Zeng , Jingjing Shao , Ruixue Gu , Yongdan Li
      An idea of combining perovskite and hydrotalcite (HT)-derived oxides is explored and a shell–core perovskite@HT-derived oxide catalyst, i.e. LaNi(Mg, Al)@Mg–Al, is fabricated through the reconstruction of a HT-derived Mg–Al mixed oxide. Experimental results show that the reconstruction of the HT-like structure proceeds rapidly in a Ni2+–La3+ mixed nitrate solution, forming large flake-like sheets on the outer layer of the dipping particle. After calcination at temperatures ≥700°C, perovskite phase with clear boundary is formed as the uniform shell layer of the catalyst. Further investigation confirms that the shell–core catalysts possess excellent activity and stability in ethanol steam reforming reaction.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Ceramic hollow fibres catalytic enhanced reactors for glycerol steam
           reforming
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): E. Gallegos-Suárez , F.R. García-García , I.D. González-Jiménez , I. Rodríguez-Ramos , A. Guerreo-Ruiz , K. Li
      In this study, NiO/MgO/CeO2 catalysts with Ni content from 5% to 30% were synthetized by sol–gel method and tested in a fixed-bed reactor (FBR) in the glycerol steam reforming (GSR) reaction. The catalysts were characterized by N2 adsorption isotherms at −196°C (S BET), X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The 20% NiO/MgO/CeO2 catalyst, which showed the highest catalytic activity in GSR reaction, was selected to be deposited in the finger-like region of the asymmetric Al2O3 hollow fibre and the sponge-like region of the symmetric Al2O3 hollow fibre in the development of the asymmetric hollow fibre reactor (AHFR) and symmetric hollow fibre reactor (SHFR), respectively. The impregnated ceramic substrates were characterized by scanning electron microscopy (SEM), EDX and TEM. The performances of the AHFR and SHFR were compared with that in a conventional FBR during the GSR reaction. Both AHFR and SHFR were operating at “dead-end” configuration at a temperature range from 250°C to 550°C, atmospheric pressure and in a reactant mixture of steam and glycerol (16:1 molar ratio). At 550°C the glycerol conversion in the AHFR and SHFR was 70% and 46%, respectively, which are 5 and 2 times higher than that obtained in the FBR. The different performances of the AHFR and SHFR could be explained due to the unlike catalyst particle size deposited in the asymmetric and symmetric substrates, 8nm and 3nm, respectively.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Gasification characteristics of carbon species derived from model
           reforming compound over Ni/Ce–Zr–O catalysts
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Xiaoyin Chen , Edwin Yik , Jonathon Butler , Johannes W. Schwank
      This work addresses a thermogravimetric method for the steam gasification of carbon deposited over ceria–zirconia supported nickel (10% Ni/CZO) catalysts. The carbon deposits, which were obtained from the decomposition of isooctane over 10% Ni/CZO catalyst at 500, 650, and 725°C, respectively, were used as the model species. Gasification temperature and characteristics of different carbon species have been investigated, and the resulting gaseous products were measured by FT-IR spectroscopy and mass spectroscopy. The carbon species formed at different decomposition temperatures indicated distinctly different ability for gasification. Combined with features of TPO profiles and SEM images, our experiments suggest that the coating carbon, which covers the surface of Ni/CZO catalyst, can be removed by gasification at low temperatures around 600°C. However, the gasification degree of filamentous carbon species depends on its formation temperature. For filamentous carbon obtained from isooctane decomposition at 500°C the gasification starts at 690°C, while filamentous carbon species obtained from isooctane decomposition at temperatures ≥650°C undergo complete gasification at this temperature.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Conversion of methanol to aromatics in fluidized bed reactor
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Tong Wang , Xiaoping Tang , Xiaofan Huang , Weizhong Qian , Yu Cui , Xinyu Hui , Wei Yang , Fei Wei
      Conversion of methanol to aromatics (MTA) was conducted over a fresh or a spent Zn/ZSM-5 catalyst in single stage fluidized bed (SSFB) and two stage fluidized bed (TSFB). Sampling at different stages of TSFB and operation in the temperature range of 250, 275, 300, 325, 350, 380 and 475°C revealed the consecutive reaction mode from methanol to DME, C1–C4 hydrocarbons, C5+ nonaromatics to aromatics finally. High weight ratio of para-xylene (PX) in xylene in wide temperature range suggested that PX was the primary product of MTA, and other xylenes are produced by the iosmerization of PX. Other aromatics such as benzene, toluene and trimethylbenzene are finally produced by the dealkylation, alkylation or disproportionation of xylene. The adoption of TSFB reactor was effective to increase the yield of aromatics, compared to that using SSFB, due to the inhibition of backmixing of gases. Combination of TSFB and highly active catalyst with strong acids was effective to get high yield of aromatics under high space velocity of methanol.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Preface
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Yanhui Yang , John S. Dennis , Mark Saeys , Yong Wang



      PubDate: 2014-06-14T14:31:46Z
       
  • Hierarchical SAPO-34/18 zeolite with low acid site density for converting
           methanol to olefins
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Yuxin Li , Yanghuan Huang , Juhua Guo , Mingye Zhang , Dezheng Wang , Fei Wei , Yao Wang
      The catalytic performance of a zeolite is largely determined by its framework topology, particle morphology and acidity. A hierarchical SAPO-34/18 zeolite with a low Si/Al ratio of 0.11–0.12 and well-ordered macropores was synthesized with the conventional hydrothermal method by just decreasing the Si content in the gel mixture, that is, the development of its hierarchical structure did not need the use of an extra template or post-processing demetallation. The hierarchical structure reduced the diffusion distance inside the zeolitic phase because the void space made it equivalent to being comprised of small zeolitic crystallites, which gave a catalytic performance akin to that of nanosized zeolite particles. Reactivity studies that used a thermogravimetry–GC combination that simultaneously measured coke in the zeolite in addition to the gaseous products from the methanol-to-olefins (MTO) process showed that the hierarchical structure and low acid site density resulted in a longer lifetime, lower selectivities to coke and propane and higher selectivities to propene and butene, that is, a better catalyst for the MTO process.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233




      PubDate: 2014-06-14T14:31:46Z
       
  • Contents list
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233




      PubDate: 2014-06-14T14:31:46Z
       
  • Carbon covered alumina prepared by the pyrolysis of sucrose: A promising
           support material for the supported Pt–Sn bimetallic dehydrogenation
           catalysts
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Sha Luo , Songbo He , XianRu Li , Chenglin Sun , K. Seshan
      Sucrose was pyrolyzed on gamma alumina surface to prepare carbon covered alumina (CCA) material. Alumina and CCA supported Pt–Sn catalysts were prepared by the complex impregnation method under vacuum. Dehydrogenation of n-octadecane was performed to study the effect of carbon addition, Pt loading and Sn/Pt weight ratio on the catalytic dehydrogenation activity, selectivity and catalyst stability. BET, mercury porosimetry, XRD, CO-chemisorption, TPR and TG-DTA were used for the carrier and the corresponding catalyst characterization. The results showed that more carbon addition, Pt loading and higher Sn/Pt ratio are propitious to the mono-olefin selectivity and catalyst stability. Pt–Sn was easily formed on the Pt–Sn/CCA catalysts, especially when the Pt loading and Sn/Pt ratio were very high. To keep optimal dehydrogenation conversion, taking consideration to good selectivity and stability, the carbon content, Pt and Sn loading of Pt–Sn/CCA catalysts should be 8.37wt.%, 0.5wt.% and 3wt.%, respectively.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Poly-(styrene sulphonic acid): An acid catalyst from polystyrene waste for
           reactions of interest in biomass valorization
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): N. Alonso-Fagúndez , V. Laserna , A.C. Alba-Rubio , M. Mengibar , A. Heras , R. Mariscal , M. López Granados
      This article reports on the use of poly-(styrene sulphonic acid) (PSSA) prepared by sulphonation of polystryrene waste as catalyst in reactions demanding acid sites. Two different waste derived catalysts (waste to catalyst, WTC) were studied: soluble PSSA (WTC-PSSA) and solid SiO2-PSSA nanocomposite (WTC-SiO2-PSSA). The catalytic properties of these waste derived acid catalysts have been explored in three different reactions of interest in biomass valorization: biodiesel synthesis, xylose dehydration to furfural and furfural oxidation to maleic and succinic acids. The results show that both soluble and nanocomposite WTC catalysts present promising catalytic properties. The WTC-PSSA requires ultrafiltration for reutilization whereas the WTC-SiO2-PSSA can be separated from the reaction mixtures by more usual techniques (centrifugation or conventional filtration). Further research is required for improving the hydrothermal stability of WTC-SiO2-PSSA in order to substantially reduce the leaching of polymer that takes place during the catalytic runs.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • HPW/MCM-41 catalyzed isomerization and dimerization of pure pinene and
           crude turpentine
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Genkuo Nie , Ji-Jun Zou , Ren Feng , Xiangwen Zhang , Li Wang
      Turpentine is biomass derived from metabolites of plants and often utilized via isomerization or dimerization of pure pinene that are separated from crude turpentine. This work is aimed to demonstrate the possibility of using crude turpentine to replace pure pinene in the acid catalyzed reactions. Firstly, H3PW12O40 (HPW) was loaded on MCM-41 using wet impregnation to enhance the dispersion of acid sites. Characterizations show that HPW is well dispersed and the acid concentration depends on the HPW amount. Then the isomerization and dimerization of α-pinene, β-pinene and crude turpentine were investigated in detail. Regardless the kind of reactant used, the product distribution is very similar in each type of reaction. Controlled experiment shows the dimerization involves a quick isomerization and thus the dimers are formed from the isomeric compounds. Moreover, components besides pinene, like oxygen-containing compounds, in crude turpentine also take part in the reactions. The reaction network is proposed based on experiment and theoretical computation. HPW/MCM-41 shows higher activity than bulk HPW, and 80% HPW/MCM-41 is the best, which leads to equal conversion (or yield) in the isomerization (or dimerization) for all the three reactants. This work shows that crude turpentine can be used to produce chemicals that are formed from pure pinene.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Copper–iron supported bimodal pore catalyst and its application for
           higher alcohols synthesis
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Mingyue Ding , Junling Tu , Jianguo Liu , Noritatsu Tsubaki , Tiejun Wang , Longlong Ma
      A Cu–Fe supported bimodal pore catalyst prepared by incipient-wetness impregnation exhibited two kinds of nano-pores. Increasing amount of copper and iron species decreased BET surface area and the size of both the small pores and large pores, while promoted the aggregation of bi-metal particles inside the large pores. Higher bimetal species content in the bimodal derived catalyst facilitated the reduction of metal oxides and the formation of metallic Cu and iron carbides during higher alcohols synthesis (HAS) reaction. The increasing of active bimetal sites and spatial effect of pore structures enhanced probably the synergistic effect of Cu–Fe, promoting the catalytic activity for HAS. Furthermore, the bimodal derived catalyst with higher Cu and Fe species loading resulted in a larger metallic particle size and lower surface area, which facilitated the product distribution of alcohols shifting towards C2 +OH.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Mixed salts of silver and ammonium derivatives of molybdovanadophosphoric
           acid to improve the catalytic performance in the oxidation of starch
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Xiaoli Chen , Hang Wang , Jian Xu , Mingxin Huo , Zijiang Jiang , Xiaohong Wang
      Mixed salts of silver and ammonium derivatives Ag x (NH4)5−x PMo10V2O40 (x =0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0) were designed and synthesized through ion exchange along with precipitation. Different molar ratio of Ag+ to NH4 + resulted in different surface areas, which could give different oxidative catalytic activity in oxidation of starch. Among all molybdovanadophosphoric salts, Ag3.5(NH4)1.5PMo10V2O40 was found to be the most active catalyst in starch oxidation with the highest degree of substitution (DS=0.62mol/100g). And Ag3.5(NH4)1.5PMo10V2O40 could be reused several times without significant loss of its catalytic activity.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Sulfonated carbon nanotubes as catalysts for the conversion of levulinic
           acid into ethyl levulinate
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Bianca L. Oliveira , Victor Teixeira da Silva
      Multiwall carbon nanotubes were sulfonated at different temperatures (150, 180, 210, 230, 250 and 280°C) and used as catalysts in the esterification of levulinic acid with ethanol. The materials sulfonated between 150 and 230°C presented almost the same acidity (measured by ammonia chemisorption), which was higher than that obtained for samples sulfonated at 250 and 280°C. Raman spectroscopy revealed that the treatment with sulfuric acid did not lead to the destruction of the carbon nanotubes structure, even for the higher temperature treatment. The activity results have shown that the nanotubes sulfonated below 250°C presented a specific activity higher than those sulfonated at 250 and 280°C. The association of these results with those obtained by temperature-programmed desorption of ammonia indicate that the activity in the esterification reaction is related to the number of acidic sites that desorb ammonia in temperatures around 220°C. Temperature-programmed desorption experiments suggest that there is a strong adsorption of the levulinic acid on the active sites therefore not allowing the reuse of the materials.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • A modified biphasic system for the dehydration of d-xylose into furfural
           using SO42−/TiO2-ZrO2/La3+ as a solid catalyst
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Huiling Li , Aojie Deng , Junli Ren , Changyu Liu , Wenju Wang , Feng Peng , Runcang Sun
      One of the most promising strategies for furfural production is to extract continually the target product from the aqueous solution utilizing organic solvents. With the aim to develop an ecologically viable catalytic pathway for furfural production without the addition of mineral acids, we presented a modified biphasic system using a solid acid (SO4 2−/TiO2-ZrO2/La3+) as catalyst for producing furfural from xylose. Different kinds of aprotic organic solvents (DMSO, DMF and DMI) in water phase and 2-butanol in organic phase (MIBK) were investigated as reaction media. Furfural yield and xylose conversion efficiency were dependent on the amounts of aprotic organic solvents and 2-butanol, the solid/liquid ratio, and the volume ratio of the organic phase and the aqueous phase as well as the reaction temperature and time. As a result, DMI showed the best performance on improving furfural yield during the furfural production. 3563.3μmol of furfural/g of xylose with 97.9% xylose conversion efficiency was obtained after 12h at 180°C when the volume ratios of water to DMI and MIBK to 2-butanol were 8:2 and 7:3, respectively.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • A stable and effective Ru/polyethersulfone catalyst for levulinic acid
           hydrogenation to γ-valerolactone in aqueous solution
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Yirong Yao , Zhiqiang Wang , Sheng Zhao , Danhong Wang , Zhijie Wu , Minghui Zhang
      A cross-linked sulfonated polyethersulfone supported Ru nanoparticle catalyst was prepared for highly hydrogenation of levulinic acid (LA) into γ-valerolactone (GVL) at mild conditions (3.0MPa H2 and 70°C) in aqueous solution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations show the formation of highly dispersed small (∼3nm) Ru clusters on the surface of polyethersulfone. Infrared spectroscopy (IR) and acid-base titration indicate the presence of sulfonic groups without the influence of the deposition of Ru species. Polyethersulfone consisted of cross-linked electron -withdrawing group SO2 , maintained its intrinsic thermal stability during the hydrogenating reaction process, and its swelling property promoted the adsorption of LA in aqueous solution. The synchronization of sulfonic groups as active sites for esterification process and metal sites for hydrogenation promoted the hydrogenation reactivity.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Comparison of gas-phase dehydration of propane polyols over solid
           acid–base catalysts
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Li-Zhi Tao , Song-Hai Chai , Hao-Peng Wang , Bo Yan , Yu Liang , Bo-Qing Xu
      Gas-phase dehydration of aqueous propane polyols including glycerol, 1,2- and 1,3-propanediols was investigated over various solid catalysts with a wide range of acid–base properties. Fairly high selectivity (40–75mol%) for propanal formation from 1,2-propanediol, and acrolein from glycerol was obtained over the catalysts with high fractional acidity in the range of −8.2< H 0 ≤−3.0, in which Brønsted acidity appeared advantageous over Lewis acidity. The dehydration of 1,3-propanediol produced quite scattered products and a clear relationship between its product selectivity and the catalyst acidity could not be established. Mechanistic implications of these observations are discussed, which point to that the dehydration reactions of both 1,2-propanediol and glycerol are initiated by activation of the hydroxyl group bonded with the central carbon atoms.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Acetalization of furfural with zeolites under benign reaction conditions
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Juan Miguel Rubio-Caballero , Shunmugavel Saravanamurugan , Pedro Maireles-Torres , Anders Riisager
      Acetalization is a viable method to protect carbonyl functionalities in organic compounds and offers a potential synthetic strategy for synthesizing derived chemicals. In this work, several families of commercial zeolites have been employed as solid acid catalysts in the acetalization of furfural to form furfural diethyl acetal at room temperature using ethanol as a renewable solvent. Among the tested catalysts, H-USY (6) provided the highest catalytic activity (79% acetal yield), excellent selectivity and reusability in five consecutive reaction runs. Process parameters such as, e.g. reaction time, catalyst loading and applicability of different lower alcohols were evaluated and optimized.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Effects of the precipitation agents and rare earth additives on the
           structure and catalytic performance in glycerol hydrogenolysis of Cu/SiO2
           catalysts prepared by precipitation-gel method
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Zhiwei Huang , Hailong Liu , Fang Cui , Jianliang Zuo , Jing Chen , Chungu Xia
      The effects of the precipitation agents (NaOH, Na2CO3, NH4OH and NH4HCO3) and rare earth additives (La, Ce, Y, Pr and Sm) were studied on the structure and catalytic performance in glycerol hydrogenolysis of the Cu/SiO2 catalysts prepared by precipitation-gel method. The physical–chemical properties of the catalysts were characterized by means of FTIR, H2-TPR, N2O chemisorption, XRD, XPS, BET and TEM. The results showed that precipitation agents had obvious effects on the phase structure, reduction property and catalytic performances (activity, selectivity and stability) of the catalysts. The Cu/SiO2 catalyst precipitated with NaOH presented the highest activity and stability than those with other precipitants, most likely due to its more even dispersion of Cu particles, higher resistant to sintering during glycerol reaction. The incorporation of rare earth additives to Cu/SiO2 catalyst could promote the structural stability and inhibit the sintering and leaching of the catalysts, especially noticeable for Y and La, and thus contribute to the long-term stability of the catalysts. Clearly, this study provides directions for the design of more efficient and stable Cu catalysts toward the industrial application of glycerol hydrogenolysis.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Sustainable production of acrolein: Catalytic gas-phase dehydration of
           glycerol over dispersed tungsten oxides on alumina, zirconia and silica
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Song-Hai Chai , Bo Yan , Li-Zhi Tao , Yu Liang , Bo-Qing Xu
      Tungsten oxides dispersed on Al2O3, ZrO2, and SiO2 supports were investigated for catalytic dehydration of glycerol (GL) to form acrolein (AC) in the gas phase at 315°C with aqueous GL (GL concentration: 36.2wt% or 10mol%, molar GL/H2O=1/9) as the feed (GHSVGL=400h−1). The WO3/Al2O3 and WO3/ZrO2 catalysts are found much more effective than WO3/SiO2 in catalyzing the reaction in terms of the selectivity (ca. 70mol% vs. 60mol%) and yield (49–58% vs. 11–32%) for AC production. Optimization of the WO3 loading (5–40wt%) and calcination temperature (550–900°C) of the WO3/Al2O3 and WO3/ZrO2 catalysts identifies that the calcination at 800°C of a 30wt% WO3/Al2O3 sample would generate the most efficient catalyst that offers an AC yield as high as 61% AC for longer than 10h (AC selectivity: 69mol%). Correlating the catalytic performance with the density of W atoms at the surfaces of WO3/Al2O3 and WO3/ZrO2 samples discloses that those catalysts having the intermediate numbers for the surface density of W atoms (3.5–7.6Wnm−2 or 0.5–1.0 monolayer), either on Al2O3 or on ZrO2, would offer the highest AC selectivity (69–72mol%). The catalytic results obtained in the temperature range of 280–400°C uncover 315°C as the optimum reaction temperature; significant derivation from this temperature would lead to faster catalyst deactivation and lower AC selectivity.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Size effects of Pt-Re bimetallic catalysts for glycerol hydrogenolysis
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Chenghao Deng , Xuezhi Duan , Jinghong Zhou , De Chen , Xinggui Zhou , Weikang Yuan
      A series of Pt-Re/CNTs catalysts with different particle sizes have been synthesized and applied in glycerol hydrogenolysis to elucidate the size effects. The trend of turnover frequency (TOF) for these different sized Pt-Re/CNTs catalysts follows a volcanic curve, in which the TOF for Pt-Re/CNTs catalyst with particle size of 1.9nm is ca. 7.5 times higher than that of 4.9nm. X-ray photoelectron spectroscopy analysis revealed that the surface Pt/Re ratio decreased with the decrease of particle size. The enrichment of surface rhenium species on smaller particles probably led to the increase in the surface acidity, which could be one reason for the enhanced activity over smaller sized Pt-Re/CNTs catalysts. However, too small sized Pt-Re/CNTs catalyst (e.g., 1.5nm) suffered from severe coking, resulting in the lower activity. Moreover, the hydrogenolysis of different substrates (glycerol, 1,2-propanediol and 1,3-propanediol) over different sized Pt-Re/CNTs catalysts was also investigated. It was revealed that the reactivity declined in the following order: glycerol>1,3-propanediol>1,2-propanediol, and the cleavage of secondary C–O bond was favored over larger sized Pt-Re/CNTs catalyst. Based on these results, a possible reaction pathway depending on Pt-Re particle size was proposed.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Synergetic effect between Cu0 and Cu+ in the Cu-Cr catalysts for
           hydrogenolysis of glycerol
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Zihui Xiao , Xinkui Wang , Jinghai Xiu , Yuemin Wang , Christopher T. Williams , Changhai Liang
      Active species of Cu-Cr catalysts, prepared by an epoxide-assisted sol–gel route, were investigated for the hydrogenolysis of glycerol to 1,2-propanediol. Structural characterization of the catalysts was performed by means of N2 physisorption, X-ray diffraction, H2-temperature programmed reduction, high-resolution X-ray photoelectron spectroscopy, NH3-temperature programmed desorption, and N2O titration. On the basis of the characterizations, the copper species on the calcined Cu-Cr catalysts and the reduced Cu-Cr catalysts were assigned. Combined with reaction results, it was found that there was not similar trend in copper metal surface area and glycerol conversion, indicating that a two-site (Cu0 and Cu+) mechanism existed in the hydrogenolysis of glycerol over Cu-Cr catalysts. Besides, the maximum conversion of glycerol was obtained when the surface Cu0/Cu+ ratio increased from 3.1 to 6.6, whereas decreased with increasing sequentially to 15.7, demonstrating that the appropriate surface Cu0/Cu+ ratio was required for optimum hydrogenation activity. Thus, the synergetic effect between the Cu0 and Cu+ was considered to be responsible for the high catalytic activity in the hydrogenolysis of glycerol, and that CuCr2O4 played a critical role in the glycerol hydrogenolysis reaction since it could function as a “hydrogen delivery bridge”.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Co-hydroprocessing of a mixture: Vegetable
           oil/n-hexadecane/4,6-dimethyldibenzothiophene for the production of
           sustainable hydrocarbons. A kinetic modeling
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Pavel Rizo-Acosta , Maria T. Linares-Vallejo , Jose A. Muñoz-Arroyo
      Co-hydroprocessing of a mixture of nonedible Jatropha oil, n-hexadecane and 4,6-dimethyldibenzothiphene (4,6-DMDBT) over NiMo/Al2O3 commercial catalyst was studied in the temperature range 613–633K, 8MPa and LHSV of 0.7–2.5h−1 in a continuous mixed flow Robinson–Mahoney Reactor. The main carboxylic acids from the feedstock undergo decarbonylation reaction, whereas the hydrodesulfurization of 4,6-DMDBT was carried out. Hydrocracking of n-C16 and the n-paraffins from the carboxylic acids was also observed. A negligible amount of cyclic hydrocarbons was produced. A high conversion level of carboxylic acids to n-paraffins was observed (81.04–99.60%). Based on the experimental results and the LHHW theory a kinetic model for the decarbonylation reaction was developed. The kinetic model parameters were obtained from the minimization of an objective function given in terms of the reaction rates and the result values are within confidence interval.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Bioethanol conversion into hydrocarbons on HZSM-5 and HMCM-22 zeolites:
           Use of in situ DRIFTS to elucidate the role of the acidity and of the pore
           structure over the coke formation and product distribution
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Zilacleide S.B. Sousa , Deborah V. Cesar , Crisitane A. Henriques , Victor Teixeira da Silva
      In the last years there has been an increasing interest for the use of ethanol not only as biofuel but also as raw material for the production of petrochemicals. In the present work the conversion of ethanol into hydrocarbons was investigated over zeolites with different acidic properties and porous structure (HZSM-5 and HMCM-22). The samples used were active for ethanol conversion and both their acidic properties and porous structure played an important role on product selectivity. HZSM-5 zeolite was the most promising catalyst for propene formation. Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were also employed to investigate the carbon species deposited on the zeolites and the adsorbed species formed during the reaction, respectively. DRIFTS results show that coke formation was severely inhibited by the pore structure of HZSM-5 justifying the high stability of this zeolite.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Continuous production of biodiesel from low grade feedstock in presence of
           Zr-SBA-15: Catalyst performance and resistance against deactivation
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Jose Iglesias , Juan A. Melero , L. Fernando Bautista , Gabriel Morales , Rebeca Sánchez-Vázquez
      Zirconium-containing SBA-15 materials have been used in the production of fatty acid methyl esters from low grade oleaginous feedstock. Its resistance against deactivation has been assessed by means of studying the effect of conventional impurities present in lipid wastes over the catalytic performance of this material. Alkaline metal cations like potassium could interact with Brønsted acid sites, causing their neutralization by ion exchange and a limited, but not complete, deactivation of the material. Additionally, organic unsaponifiable compounds like retinoids or phospholipids – being studied in this work as retinol and lecithin, respectively – strongly interact with the catalyst surface, leading to a strong deactivation of the material, though reversible, since they are fully regenerated by calcination in air. Catalytic assays in continuous mode in a fixed bed reactor suggest a higher resistance of Zr-SBA-15/bentonite pellets against catalyst deactivation. Bentonite clay, which has been used as binding agent for the preparation of the particulate catalyst, seems to be responsible for this behavior, acting as poison scavenger and preventing the access of the impurities to the catalytic acid sites and consequently their deactivation.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Can surface energy measurements predict the impact of catalyst
           hydrophobicity upon fatty acid esterification over sulfonic acid
           functionalised periodic mesoporous organosilicas'
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Cyril Pirez , Adam F. Lee , Christopher Jones , Karen Wilson
      Sulfonic acid functionalised periodic mesoporous organosilicas (PrSO3H-PMOs) with tunable hydrophobicity were synthesised via a surfactant-templating route, and characterised by porosimetry, TEM, XRD, XPS, inverse gas chromatography (IGC) and ammonia pulse chemisorption. IGC reveals that incorporation of ethyl or benzyl moieties into a mesoporous SBA-15 silica framework significantly increases the non-specific dispersive surface energy of adsorption for alkane adsorption, while decreasing the free energy of adsorption of methanol, reflecting increased surface hydrophobicity. The non-specific dispersive surface energy of adsorption of PMO-SO3H materials is strongly correlated with their activity towards palmitic acid esterification with methanol, demonstrating the power of IGC as an analytical tool for identifying promising solid acid catalysts for the esterification of free fatty acids. A new parameter − Δ G NP − P C , defined as the per carbon difference in Gibbs free energy of adsorption between alkane and polar probe molecules, provides a simple predictor of surface hydrophobicity and corresponding catalyst activity in fatty acid esterification.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • The application of Zr incorporated Zn-Al dehydrated hydrotalcites as solid
           base in transesterification
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Qianhe Liu , Congxin Wang , Wei Qu , Bingchun Wang , Zhijian Tian , Huaijun Ma , Renshun Xu
      Zr incorporated Zn-Al dehydrated hydrotalcites solid bases were obtained by calcining Zr-Zn-Al hydrotalcites at 140°C and 200°C. These solid bases were characterized by X-ray diffraction, N2 adsorption/desorption, UV–vis diffuse reflectance spectra, temperature programmed desorption of CO2 and infrared spectroscopy of CO2 adsorption. The results show that the Zr incorporated Zn-Al dehydrated hydrotalcites have larger pore diameter and stronger base-strength than the un-incorporated one. The sample with the Zr/Zn/Al ratio of 0.25/2.56/1 has the largest pore diameter, which is 10.6nm. The basic sites of these solid bases are OH groups and the sample treated at 200°C has more basic sites than which treated at 140°C. These solid bases were evaluated as catalysts in the transesterification reaction for the biodiesel (FAME) production. The sample (with Zr/Zn/Al of 0.25/2.56/1) treated at 200°C gives the FAME yield of 91.71% at 140°C, 1.7MPa and 1.0h−1. It shows no deactivation in the reaction of about 300h.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • High quality diesel-range alkanes production via a single-step
           hydrotreatment of vegetable oil over Ni/zeolite catalyst
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Congxin Wang , Qianhe Liu , Jie Song , Wei Li , Peng Li , Renshun Xu , Huaijun Ma , Zhijian Tian
      A single-step hydrotreatment of vegetable oil to produce high quality diesel-ranged alkanes over Ni/zeolite catalyst is devised. The Ni/zeolite catalysts prepared by incipient wetness impregnation method using SAPO-11, ZSM-5, ZSM-22, ZSM-23 and Beta zeolites as supports are evaluated in this single-step hydrotreatment process. The effects of the support and the metal loading amount are studied from the catalytic performance and characterization results obtained by techniques such as XRD, Physisorption, NH3-TPD and Pyridine-IR. Over the 8wt%Ni/SAPO-11 catalyst, 100% conversion of soybean oil is obtained at 370°C, 4MPa and 1h−1, with an organic liquid yield of 74.8% which is nearly 90% of the maximum theoretical liquid yield. In the organic products, the alkane selectivity is 100%, and more than 85% isomerization selectivity is achieved. In order to learn the detailed scheme of the single-step hydrotreatment process, the intermediates have been analyzed from which reaction pathways are proposed and discussed.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Aqueous-phase hydrodeoxygenation of lignin monomer eugenol: Influence of
           Si/Al ratio of HZSM-5 on catalytic performances
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Cong Zhang , Jing Xing , Liang Song , Hongchuan Xin , Sen Lin , Lishu Xing , Xuebing Li
      Aqueous phase catalytic upgrading of phenolic monomers to hydrocarbons have been explored using Pd/C combined with HZSM-5 zeolite catalysts in the presence of H2. 2-Methoxyl-4-allylphenol (eugenol), which consists of methyl ether bond, hydroxyl group, aromatic ring and propyl olefin bond, was chosen as a classic lignin model compound. This research focuses on the relationship between the acidity of zeolites and the deoxygenation activities basis on the hydrodeoxygenation (HDO) of eugenol. The results indicated that the decrease of Si/Al ratio resulted in the increase of the acidity of the zeolites, which significantly influenced their catalytic performance for product distributions. Over the HZSM-5 (Si/Al=12.5) catalyst, the 2-methoxyl-4-propylphenol conversion of 86.5% and the hydrocarbon selectivity of 73.4% were obtained with the HDO of eugenol under 513K and 5MPa hydrogen pressure. Owing to the lower selectivity of hydrocarbon with HZSM-5 (Si/Al=50) as acidic catalyst, the pore treatment was used to enlarge the outer surface of zeolite. After modified by alkali-treatment, much more acid active sites were provided for feasible accessibility of oxygenated reactants. The selectivity of hydrocarbons was improved by the alkaline treatment of HZSM-5 zeolite with 0.3molL−1 sodium hydroxide solution.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Selective hydrodeoxygenation of lignin-related 4-propylphenol into
           n-propylbenzene in water by Pt-Re/ZrO2 catalysts
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Hidetoshi Ohta , Bo Feng , Hirokazu Kobayashi , Kenji Hara , Atsushi Fukuoka
      Bimetallic Pt-Re/ZrO2 catalysts were developed for the selective hydrodeoxygenation of 4-propylphenol as a lignin model to n-propylbenzene in water. The addition of Re to Pt/ZrO2 improved the catalyst stability and product selectivity. Reaction temperature greatly affected not only reaction efficiency but also product distribution. n-Propylbenzene was obtained in up to 73% yield with ca. 80% selectivity. After the reaction, the catalyst was deactivated possibly due to water-induced wrapping of Pt nanoparticles in ZrO2. The reaction may involve the hydrogenation of 4-propylphenol to 4-propylcyclohexanol, followed by the dehydration to give 4-propylcyclohexene and the subsequent dehydrogenation to n-propylbenzene.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Transfer hydrogenation of phenol on supported Pd catalysts using formic
           acid as an alternative hydrogen source
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Damin Zhang , Feiyang Ye , Teng Xue , Yejun Guan , Yi Meng Wang
      Palladium nanoparticles with size smaller than 10nm were loaded on several supports including activated carbon (AC), MIL-101, TiO2, Al2O3, and TiO2-activated carbon composites (TiO2-AC). These catalysts showed high activity in liquid phase hydrogenation of phenol. Their catalytic performances in transfer hydrogenation of phenol with formic acid under mild conditions (T =50°C and P <5bar) were also tested for the purpose of in situ upgrading of bio-oil. The activity followed the trend of Pd/AC>Pd/TiO2-AC>Pd/MIL-101>Pd/TiO2 >Pd/Al2O3. When 400μL of formic acid was introduced into 10mL of 0.25M aqueous phenol solution, phenol can be fully hydrogenated on 200mg of Pd/AC catalyst at 50°C within 4h, with 80% selectivity to cyclohexanone. The high activity of Pd/AC catalyst in hydrogen transfer makes it possible for in situ upgrading of bio-oil under mild conditions by converting unstable components (such as HCOOH and phenol) to stable ones (mainly cyclohexanone) which can then be potentially introduced into current refinery. In addition, the effect of formic acid on the hydrogenation activity of supported Pd catalysts was also reported. Presence of formic acid significantly decreased the hydrogenation activity of Pd supported on MIL-101 and oxides (TiO2 and Al2O3), probably due to the competitive adsorption of molecular formic acid with phenol on a single Pd site.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Catalytic hydrodeoxygenation of anisole as lignin model compound over
           supported nickel catalysts
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Shaohua Jin , Zihui Xiao , Chuang Li , Xiao Chen , Lei Wang , Jiacheng Xing , Wenzhen Li , Changhai Liang
      Catalytic hydrodeoxygenation (HDO) of anisole, a methoxy-rich lignin model compound, has been investigated over a series of Ni-containing (10wt% loading) catalysts with activated carbon, SBA-15, SiO2, and γ-Al2O3 supports, in order to understand their ability for removal of OCH3 from anisole. This catalytic reaction had been carried out in an autoclave at 180–220°C and 0.5–3.0MPa H2 pressure. Nickel-catalyzed aromatic ring-hydrogenation compared with the subsequent demethylation and deoxygenation is the fastest step in HDO of anisole under the present reaction conditions. Among these catalysts, the aromatic ring-saturated cyclohexyl methyl ether is mainly obtained over Ni/AC, while the Ni/SiO2 displayed the highest activity in HDO of anisole (selectivity to deoxygenated products >95%). Differences in HDO efficiency among the catalysts are attributed not only to variations in the dispersion of the active phase, but also to the acid sites which may contribute to the cleavage of CO bonds. It has also been shown that the activity toward oxygen-removal strongly depended on reaction temperature and the conversion of anisole favors the production of oxygen-free aromatics by the direct demethoxylation pathway at the relatively low H2 pressure.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Mesoporous Nb2O5 as solid acid catalyst for dehydration of d-xylose into
           furfural
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): C. García-Sancho , J.M. Rubio-Caballero , J.M. Mérida-Robles , R. Moreno-Tost , J. Santamaría-González , P. Maireles-Torres
      The acid-catalyzed dehydration of d-xylose to furfural has been investigated in a biphasic water–toluene system, using a mesoporous Nb2O5 catalyst prepared by a neutral templating route. The catalytic behavior was compared with a commercial Nb2O5. Materials were characterized by XRD, XPS, TEM, NH3-TPD, Raman spectroscopy and N2 sorption. The d-xylose conversion and furfural yield over the mesoporous niobia were found to increase with reaction temperature and time, in such a way that at 170°C and 90min, a d-xylose conversion and a furfural yield were higher than 90% and 50%, respectively. However, the commercial crystalline niobia displayed a low activity. The stability of the mesoporous catalyst has been demonstrated by XRD and N2 sorption, and corroborated by the absence of significant niobium leaching in solution.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Reaction network analysis and continuous production of isosorbide
           tert-butyl ethers
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Rebecca Pfützenreuter , Marta Helmin , Stefan Palkovits , Regina Palkovits , Marcus Rose
      Isosorbide is considered a versatile biogenic platform compound for the production of chemicals. The functionalization of its two hydroxyl groups is challenging since they exhibit a different configuration and thus, different reactivity as well as sterical accessibility. We investigated the formation of the respective tert-butyl ethers by an addition reaction of isosorbide to isobutene heterogeneously catalyzed by acidic ion exchange resins. An efficient liquid phase process under ambient conditions in a batch reactor has been developed. The reaction network was unravelled by detailed investigation of the reaction kinetics. Additionally, the feasibility of continuous processing was successfully demonstrated on the lab-scale applying a continuously stirred-tank reactor.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Selective hydrogenative cleavage of C–C bonds in sorbitol using
           Ni–Re/C catalyst under nitrogen atmosphere
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Junjie Zhang , Fang Lu , Weiqiang Yu , Jiazhi Chen , Shuai Chen , Jin Gao , Jie Xu
      The use of high pressure fossil derived hydrogen limits the commercial prospects of transforming sorbitol to glycols. Ni–Re/C catalyst which was developed in this study demonstrated high selectivity toward hydrogenative cleavage of C2–C3 and C3–C4 bonds of sorbitol to produce glycols under 1MPa nitrogen. Acetol which is proposed as important intermediate to explain the reaction mechanism was first detected in the sorbitol conversion reactions. Detailed investigations showed that the presence of Re could prevent the sintering of Ni particles during the reduction process and make the catalyst efficiently generate hydrogen on the active sites to selectively cleave C–C bonds in sorbitol under nitrogen atmosphere.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Exploring the reaction conditions for Ru/C catalyzed selective
           hydrogenolysis of xylitol alkaline aqueous solutions to glycols in a
           trickle-bed reactor
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Florian Auneau , Maeva Berchu , Guillaume Aubert , Catherine Pinel , Michèle Besson , Daniela Todaro , Marco Bernardi , Tiziano Ponsetti , Renzo Di Felice
      The hydrogenolysis of an alkaline aqueous solution of xylitol to mainly ethylene- and propylene-glycols was studied over a Ru/C catalyst in a high pressure fixed-bed reactor run in the trickle-bed mode with co-current downflow of liquid feed and hydrogen. The effects of reaction parameters including H2 pressure (40–80bar), temperature (190–200°C) and pH values (NaOH/xylitol molar ratio in the range 0.1–0.2, pH 9–12) and residence time have been explored to increase the selectivity of this reaction to the desired ethyleneglycol product. The activity and final products distribution were much influenced by the hydrogen pressure. An optimum to afford a high conversion and a high selectivity to ethyleneglycol at different space times was found at 60bar. The effects observed are in agreement with the reaction pathways previously proposed and the relative reaction rates of the dehydrogenation/hydrogenation and base-catalyzed reactions of the intermediates are affected by the hydrogen pressure and the concentration of the alkaline promoter.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Synthesis of diesel range alkanes with 2-methylfuran and mesityl oxide
           from lignocellulose
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Shanshan Li , Ning Li , Guangyi Li , Aiqin Wang , Yu Cong , Xiaodong Wang , Tao Zhang
      For the first time, the alkylation of 2-methylfuran with mesityl oxide was carried out over a series of solid acid catalysts. Among the investigated candidates, Nafion-212 resin exhibited the highest catalytic efficiency and good stability, which can be rationalized by the higher acid strength of this catalyst. The hydrodeoxygenation (HDO) of the alkylation products of 2-methylfuran with mesityl oxide was also studied. Ni–Mo2C/SiO2 and Ni–W2C/SiO2 were firstly used for the HDO of biomass derived oxygenates and demonstrated excellent catalytic performance for the conversion of the alkylation products to alkanes. Compared with Ni–W2C/SiO2, Ni–Mo2C/SiO2 exhibited higher selectivity to diesel range alkanes. Over the Ni–Mo2C/SiO2 catalyst, high carbon yield of diesel range alkanes (77%) could be achieved by the HDO of the alkylation products of 2-methylfuran and mesityl oxide at 573K and 6.0MPa H2. This value is evidently higher than those obtained over noble metal catalysts and Ni–W x C/AC under the same reaction conditions.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Reaction media dominated product selectivity in the isomerization of
           glucose by chromium trichloride: From aqueous to non-aqueous systems
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Songyan Jia , Kairui Liu , Zhanwei Xu , Peifang Yan , Wenjuan Xu , Xiumei Liu , Z. Conrad Zhang
      While chromium trichloride hydrate (CrCl3·6H2O) effectively catalyzed the isomerization of glucose into fructose in aqueous solution, a general product selectivity behavior was observed independent of reaction variables such as reaction time, temperature, catalyst loading, halide ion, and initial glucose concentration. By studying the mixed solution of dimethylsulfoxide (DMSO) and water at varied DMSO/H2O ratios, it was found that deviation from the general water-phase fructose yield curve, with concomitant 5-hydroxymethylfurfral (HMF) formation, occurred when the fructose concentration in available water became sufficiently high in DMSO rich solvent mix. Therefore, tuning the solvent system was the most effective approach to change the product distribution from CrCl3·6H2O catalyzed glucose conversion. The apparent activation energy of glucose conversion in the studied system was estimated to be 58.6kJmol−1. Special attention was also given to gain some mechanistic insights by control experiments with simple model compounds and additives, 13C NMR and UV–vis spectroscopic analyses.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Selective hydrogenolysis of biomass-derived xylitol to ethylene glycol and
           propylene glycol on Ni/C and basic oxide-promoted Ni/C catalysts
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Jiying Sun , Haichao Liu
      The selective hydrogenolysis of xylitol to ethylene glycol and propylene glycol was examined on Ni/C catalysts in the presence of solid bases, e.g. Ca(OH)2 and CeO2, physically mixed with or co-supported with Ni on C. Compared with Ru/C, the Ni/C catalysts were more selective to the two target glycols under identical conditions, apparently as a result of their lower hydrogenation activity and consequently favored the CC cleavage of xylose intermediate by the base catalyst over its competitive hydrogenation on the Ni particles. Noticeably, the presence of the solid bases rendered the Ni particles resistant to leaching and sintering, and thus stable in the xylitol hydrogenolysis. Supporting the solid bases, especially CeO2 and CaO, with the Ni particles on C led not only to a reduction in the amount of solid bases required, but also efficient formation of the two glycols with negligible lactic acid. For instance, on Ni-CaO/C (at a CaO/Ni molar ratio of 0.66), the combined selectivity to ethylene glycol and propylene glycol, together with glycerol, reached 69.5% at nearly 100% xylitol conversion at 473K, 4.0MPa H2. These features of the basic oxide-promoted Ni catalysts show their promising advantages over the noble Ru catalysts, upon optimization of their compositions and structures, and the reaction parameters, for the efficient hydrogenolysis of xylitol and other lignocellulose-derived polyols to produce the two target glycols.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Hydrothermally stable regenerable catalytic supports for aqueous-phase
           conversion of biomass
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Jinzhao Duan , Yong Tae Kim , Hui Lou , George W. Huber
      The hydrothermal stability of TiO2- and ZrO2-based materials was studied by exposing the samples to liquid water at 523K for 60h in a batch reactor. No phase transformation or loss in BET surface area was observed for TiO2-based materials that had initial BET surface area of less than 52m2/g. In contrast, the BET surface area decreased and the primary crystallite size increased for all ZrO2-based materials tested. The BET surface area decreased and the primary crystallite size increased for high BET surface area TiO2 (156m2/g) and ZrO2 (246m2/g). Silica-containing TiO2 only lost 30% of its high BET surface area (from 128 to 90m2/g). In contrast a material composed of silica–phosphate–ZrO2 lost 56–72% of its BET surface area. Using the crystalline TiO2 as a support, we prepared and tested a Pt–ReO x /TiO2 catalyst for hydrodeoxygenation of sorbitol. Pt–ReO x /TiO2 was almost 2 times more active on a total Pt basis than Pt–ReO x /C catalyst. Between 0.1 and 0.9wt% of coke formed on the catalyst surface after reaction depending on the reaction conditions. The coke could be removed and the catalyst activity completely regenerated by an oxidation-reduction treatment. The catalyst showed only minimal change in BET surface area, TiO2 phase and TiO2 crystallite size after more than 163h of time on stream. The CO chemisorption of Pt–ReO x /TiO2 increased after reaction which was probably due to migration of ReO x species away from the Pt during the reaction.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Biomass into chemicals: One-pot production of furan-based diols from
           carbohydrates via tandem reactions
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Haile Cai , Changzhi Li , Aiqin Wang , Tao Zhang
      In this work, the direct production of furan-based diols from carbohydrates and their upstream raw materials via one-pot tandem reactions in ionic liquid/water system is presented. In this novel reaction system, ionic liquid serves as an advantageous solvent for polysaccharide (cellulose, inulin, sucrose) hydrolysis and hexose dehydration reactions, and heterogeneous Pd, Pt, Ir, Ni, Ru-based catalysts catalyze HMF hydrogenation reaction under relatively mild condition (50°C, 6MPa H2) to afford moderate to high yield (34.0–89.3%) of furan-based diols, namely, 2,5-dihydroxymethylfuran (DHMF) and 2,5-dihydroxymethyltetrahydrofuran (DHMTF). Our results show that the metal species strongly affects the selectivity of the products, while the nature of the support influences the activity of the catalysts significantly. By selecting the proper metal species and the support, controllable production of DHMF or DHMTF was realized. Based on the intermediates identified and the conversion results, the proposed reaction pathway, including possible side reactions were presented. Taken together, our catalytic system featured with simple process, mild condition, high yield of diols and adjustable product selectivity. The direct conversion of the carbohydrates and the upstream materials drives our technology nearer to real application for cost-efficient production of chemicals from biomass.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Heterogeneous acid-catalysts for the production of furan-derived compounds
           (furfural and hydroxymethylfurfural) from renewable carbohydrates: A
           review
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): I. Agirrezabal-Telleria , I. Gandarias , P.L. Arias
      The production of value-added chemicals from renewable sources, such as biomass-derived carbohydrates, is an emerging field. The amount of publications in the field of pentose and hexose conversion to furfural and hydroxymethylfurfural has considerably increased in the recent years. Most of these studies focus on using heterogeneous acid-catalysts to selectively convert these carbohydrates into the desired products at optimized yields. This review aims to summarize the most significant studies reporting the conversion of C5 and C6 carbohydrates using different structured materials. The final goal is to provide with a general overview of the broad spectrum of heterogeneous catalysts studies and the correlation between their physicochemical properties, with a special attention on the pore structure, and the catalytic activity under different reaction conditions, such as solvents or temperature. In the case of furfural, as it is already a commercial product, a short overview of the manufacturing process and the current improvements will also be given. The future studies reporting the carbohydrate dehydration reactions to furfural and HMF could take advantage of this study to select the physicochemical properties of the catalysts required to achieve their specific goals.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Catalytic transformations of cellulose and cellulose-derived carbohydrates
           into organic acids
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Weiping Deng , Qinghong Zhang , Ye Wang
      The efficient utilization of lignocellulosic biomass for the production of chemicals and fuels is of high significance from the viewpoint of establishing sustainable society. The selective transformation of cellulose, the main component of lignocellulosic biomass, into platform chemicals, which can be easily converted to various chemicals or fuels in the subsequent step, under mild conditions is a promising route. Organic acids such as levulinic acid, lactic acid, gluconic acid, and formic acid are important platform chemicals, and the conversion of carbohydrates into organic acids has attracted much attention in recent years. The present short review article highlights recent research progress in the development of new routes for the production of organic acids from cellulose or cellulose-derived carbohydrates. In particular, we will demonstrate that the bifunctional catalysts coupling the acid sites for the activation of the glycosidic bonds via hydrolysis and the metal nanoparticles for the oxidation of glucose intermediate show promising performances for the conversion of cellulose into gluconic acid in water in the presence of O2. The multifunctional catalysts or catalytic systems combining the abilities of isomerization and dehydration–rehydration or retro-aldol fragmentation can provide levulinic acid or lactic acid from cellulose under anaerobic conditions. The reaction mechanism in each case will also be discussed to gain insights into how the CC or CO bonds in cellulose or glucose are activated and cleaved and the roles of catalysts in these steps.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Mechanocatalytic depolymerization of cellulose and raw biomass and
           downstream processing of the products
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): F. Schüth , R. Rinaldi , N. Meine , M. Käldström , J. Hilgert , M.D. Kaufman Rechulski
      The utilization of lignocelluloses (e.g. wood, grass, crops residues and several others) shows great potential as part of the solution for decreasing the dependence of modern societies on fossil resources. In spite of this, the catalytic conversion of these renewable carbon resources via chemical and biotechnological processes is hindered by their complex polymeric nature. For this reason, chemical or enzymatic processes for hydrolysis of cellulose suffer from low efficacy due to harsh reaction conditions and high byproduct formation in case of the chemical methods, or high costs and long reaction times for the enzymatic methods. There is thus an urgent need for processes able to convert the whole plant biomass, which allow the formation of fermentable sugars and technical sulfur-free lignins. Recently, we demonstrated the combination of acid-catalysis with mechanical forces to be an efficient approach to fully overcome the recalcitrance of lignocellulose. As a result, the solvent-free depolymerization of lignocellulose (in solid-state) forms ‘water-soluble lignocellulose’ in quantitative yield. In this article, we present an overview of the mechanocatalytic depolymerization of lignocellulose and downstream processing of the ‘water-soluble’ lignocellulose’ to sugar alcohols and furfurals. The water-soluble products appear to be the ideal platform at the beginning of advanced value chains of biorefining, starting with ‘real’ lignocellulosic substrates.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • Some important catalytic challenges in the bioethanol integrated
           biorefinery
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Eduardo Falabella Sousa-Aguiar , Lucia Gorenstin Appel , Priscila Costa Zonetti , Adriano do Couto Fraga , Alex Azevedo Bicudo , Isabel Fonseca
      The concept of integrated biorefinery is presented and discussed. Integrated biorefineries demand the use of innovation, or rather, new chemical routes must be introduced in order to add value to intermediates and residues. The concept of integrated biorefinery is then applied to an ethanol producing facility and a flow sheet of the main catalytic routes to promote modifications of residues is proposed. CO2 and bagasse are considered the most promising residues to undergo catalytic transformations. Hydrogenation of CO2 to produce syngas/methanol is an interesting alternative to add value to this molecule. Nickel supported on a mixed oxide NiCeZr is presented as an excellent catalyst to produce syngas out of CO2. Furthermore, the potential use of two main components of bagasse, lignin and hemicellulose, is discussed, lignin being deployed as a feedstock to produce activated carbons and acidic sulfonated carbons, Acid sulfonated carbons are shown to be excellent catalysts for hydrolysis/dehydration of biomass derivatives such as polysaccharides and polyols. Moreover, activated carbons may also play an important role as outstanding supports for metal-supported catalysts, which may be used in the hydrogenation of sugars.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234




      PubDate: 2014-06-14T14:31:46Z
       
  • Contents list
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234




      PubDate: 2014-06-14T14:31:46Z
       
  • Preface
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Tao Zhang , Avelino Corma , Ferdi Schüth



      PubDate: 2014-06-14T14:31:46Z
       
  • Evolving scenarios for biorefineries and the impact on catalysis
    • Abstract: Publication date: 1 October 2014
      Source:Catalysis Today, Volume 234
      Author(s): Paola Lanzafame , Gabriele Centi , Siglinda Perathoner
      The model of future biorefineries is changing driven from many motivations, particularly the need of improving sustainability and integration with the chemical production. This conceptual review discusses this change, with focus on the case of integrated chemical biorefineries, and how the new scenarios for a sustainable chemical production require to develop new related models of biorefineries. Two cases are discussed in detail: (i) olefin biorefineries and (ii) biorefineries for sustainable chemical production. In addition, some elements for an integrated solar biorefinery approach are also given. The status of catalysis research to enable the development of these biorefinery models was discussed, together with an analysis of the industrial developments in the field and some elements of assessment of the different routes. The aim was to provide fundamentals to understand how this area is evolving, and thus identify where research effort has to be focused. It was also commented how the simple economic analysis, with boundary limits to plant gate, although important, is not enough to properly identify the future scenarios.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
  • The effect of ZnO addition on Co/C catalyst for vapor and aqueous phase
           reforming of ethanol
    • Abstract: Publication date: 15 September 2014
      Source:Catalysis Today, Volume 233
      Author(s): Stephen D. Davidson , Junming Sun , Yongchun Hong , Ayman M. Karim , Abhaya K. Datye , Yong Wang
      The effect of ZnO addition on the oxidation behavior of Co along with catalytic performance in vapor and aqueous phase reforming of ethanol were investigated on Co supported on carbon black (XC-72R). Carbon was selected to minimize the support interactions. Effect of ZnO addition during both vapor and aqueous phase reforming were compared at 250°C. ZnO addition inhibited the reduction of cobalt oxides by H2 and created surface sites for H2O activation. During vapor phase reforming at 450°C the redox of cobalt, driven by steam oxidation and H2 reduction, trended to an equilibrium of Co0/Co2+. ZnO showed no significant effect on cobalt oxidation, inferred from the minor changes of C1 product yield. Surface sites created by ZnO addition enhanced water activation and oxidation of surface carbon species, increasing CO2 selectivity. At 250°C cobalt reduction was minimal, in situ XANES demonstrated that ZnO addition significantly facilitated oxidation of Co0 under vapor phase reforming conditions, demonstrated by lower C1 product yield. Sites introduced by ZnO addition improved the COx selectivity at 250°C. Both Co/C and Co-ZnO/C rapidly oxidized under aqueous phase reaction conditions at 250°C, showing negligible activity in aqueous phase reforming. This work suggests that ZnO affects the activation of H2O for Co catalysts in ethanol reforming.
      Graphical abstract image

      PubDate: 2014-06-14T14:31:46Z
       
 
 
JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2014