for Journals by Title or ISSN
for Articles by Keywords

Publisher: Elsevier   (Total: 2585 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     [SJR: 1.283]   [H-I: 129]
   [8 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [2585 journals]
  • A modified expression of the major hydrolase activator in Hypocrea
           jecorina (Trichoderma reesei) changes enzymatic catalysis of biopolymer
    • Abstract: Publication date: 10 June 2011
      Source:Catalysis Today, Volume 167, Issue 1
      Author(s): Marion E. Pucher , Matthias G. Steiger , Robert L. Mach , Astrid R. Mach-Aigner
      Hypocrea jecorina (anamorph Trichoderma reesei) is a saprophytic fungus that produces hydrolases, which are applied in different types of industries and used for the production of biofuel. A recombinant Hypocrea strain, which constantly expresses the main transcription activator of hydrolases (Xylanase regulator 1), was found to grow faster on xylan and its monomeric backbone molecule d-xylose. This strain also showed improved ability of clearing xylan medium on plates. Furthermore, this strain has a changed transcription profile concerning genes encoding for hydrolases and enzymes associated with degradation of (hemi)celluloses. We demonstrated that enzymes of this strain from a xylan cultivation favoured break down of hemicelluloses to the monomer d-xylose compared to the parental strain, while the enzymes of the latter one formed more xylobiose. Applying supernatants from cultivation on carboxymethylcellulose in enzymatic conversion of hemicelluloses, the enzymes of the recombinant strain were clearly producing more of both, d-xylose and xylobiose, compared to the parental strain. Altogether, these results point to a changed hydrolase expression profile, an enhanced capability to form the xylan-monomer d-xylose and the assumption that there is a disordered induction pattern if the Xylanase regulator 1 is de-regulated in Hypocrea.

      PubDate: 2015-01-19T11:56:23Z
  • EPR studies of electron and hole trapping in titania photocatalysts
    • Abstract: Publication date: 17 March 2012
      Source:Catalysis Today, Volume 182, Issue 1
      Author(s): I. Ross Macdonald , Shona Rhydderch , Emily Holt , Neil Grant , John M.D. Storey , Russell F. Howe
      In situ EPR spectroscopy at cryogenic temperatures is used to observe paramagnetic products formed when titania photocatalysts are irradiated with UV–visible light in the presence of reactant molecules. Irradiation in vacuo, in the absence of reactants, produces weak EPR signals of trapped holes (O−) and trapped electrons (Ti3+). When high photon fluxes are used, the intensities of the trapped electron signals are enhanced dramatically when irradiation is stopped. This process is completely reversible on restoring the irradiation, and is attributed to a trapping of EPR invisible conduction band electrons once irradiation is stopped. The trapped electrons are excited back into the conduction band when irradiation is resumed. In the presence of adsorbed organic compounds, products of valence band hole trapping by the organic molecules are detected. Methyl radicals are formed by attack of valence band holes on adsorbed acetic acid. The valence band holes are also able to cleave carbon–silicon bonds, forming methyl radicals from tetramethylsilane. Benzyltrimethylsilane derivatives form both methyl radicals and benzyl radicals through cleavage of all four carbon–silicon bonds. The relevance of these observations to photocatalysed organic reactions in which carbon–carbon bond formation occurs via radical intermediates is discussed.
      Graphical abstract image Highlights ► In situ EPR spectroscopy detects conduction band electrons trapped as Ti3+ in titania photocatalysts. ► Efficiency of electron trapping is different between anatase and rutile. ► Trapped valence band holes are largely EPR silent. ► Radicals produced by hole or electron transfer to adsorbed organic molecules adsorbed on titania relate to reaction mechanisms.

      PubDate: 2015-01-19T11:56:23Z
  • Selective suppression of disproportionation reaction in solvent-less
    • Abstract: Publication date: 30 March 2013
      Source:Catalysis Today, Volume 203
      Author(s): Enhong Cao , Meenakshisundaram Sankar , Ewa Nowicka , Qian He , Moataz Morad , Peter J. Miedziak , Stuart H. Taylor , David W. Knight , Donald Bethell , Christopher J. Kiely , Asterios Gavriilidis , Graham J. Hutchings
      Disproportionation of benzyl alcohol has been identified as the source of toluene formation in the solvent free oxidation of benzyl alcohol using supported gold palladium catalysts. There is a slight increase in the disproportionation reaction, and hence the toluene selectivity, when this reaction is performed in a continuous mode using a micro-packed bed reactor when compared to the same reaction performed in a conventional glass stirred batch reactor. Oxidation and disproportionation reactions respond slightly differently to the changes in reaction parameters, like oxygen concentration and pressure, when a micro packed bed reactor was used instead of a conventional glass stirred reactor. When MgO supported gold–palladium catalysts were used for this reaction, the toluene selectivity reduced substantially at the cost of conversion.
      Graphical abstract image Highlights ► Disproportionation of benzyl alcohol has been identified as the source of toluene formation in the aerobic oxidation of benzyl alcohol in a micro packed bed reactor (MPBR). ► This disproportionation reaction is sensitive to the reaction parameters like temperature and O2 concentration. ► Oxygen is found to promote the disproportionation, although it is not involved in the stoichiometry of the reaction. ► Quantification of oxidation and disproportionation reactions reveals that disproportionation is slightly more favoured in a MPBR than in a conventional glass stirred reactor. ► When MgO is used as the support instead of TiO2, disproportionation is reduced substantially and thus the toluene selectivity.

      PubDate: 2015-01-19T11:56:23Z
  • A critical review of CO2 photoconversion: Catalysts and reactors
    • Abstract: Publication date: 1 April 2014
      Source:Catalysis Today, Volume 224
      Author(s): Kimfung Li , Xiaoqiang An , Kyeong Hyeon Park , Majeda Khraisheh , Junwang Tang
      Photocatalytic conversion of CO2 to either a renewable fuel or valuable chemicals, using solar energy has attracted more and more attention, due to the great potential to provide an alternative clean fuel and solve the problems related to the global warming. This review covers the current progress of photocatalytic conversion of CO2 by photocatalysis over the metal oxides. A brief overview of the fundamental aspects for artificial photosynthesis has been given and the development of novel photocatalysts for CO2 photoreduction has been discussed. Several key factors for high-efficiency CO2 photoreduction and the recent development of photocatalytic reactor design for this artificial photosynthesis have also been highlighted.
      Graphical abstract image

      PubDate: 2015-01-19T11:56:23Z
  • Energy, catalyst and reactor considerations for (near)-industrial plasma
           processing and learning for nitrogen-fixation reactions
    • Abstract: Publication date: 1 August 2013
      Source:Catalysis Today, Volume 211
      Author(s): V. Hessel , A. Anastasopoulou , Q. Wang , G. Kolb , J. Lang
      The MAPSYN project of the European Union (standing for Microwave, Acoustic and Plasma SYNtheses) aims at the utilization of plasma technology for nitrogen fixation reactions on an industrial scale and with industrial plasma reactor technology, developed and utilised commercially [1]. Key motif is enhanced energy efficiency to make an industrial plasma process viable for chemical industry. The corresponding enabling technologies – plasma catalysis, smart reactors (microreactors) and more – go beyond prior approaches. Continuing a first more project-based literature compilation, this overview focus on the two first enabling functions, plasma catalysis and smart reactor technology, which are reviewed for industrial and near-industrial plasma-based applications. It is thereby evident that notable promise is given for the nitrogen fixation as well and indeed this has been demonstrated also for nitrogen fixation; yet, initially and without the holistic system engineering dimension.
      Graphical abstract image

      PubDate: 2015-01-19T11:56:23Z
  • In-situ synthesis of hydrogen peroxide in tandem with selective oxidation
           reactions: A mini-review
    • Abstract: Publication date: Available online 29 April 2014
      Source:Catalysis Today
      Author(s): B. Puértolas , A.K. Hill , T. García , B. Solsona , Laura Torrente-Murciano
      One-pot combination of the in-situ generation of hydrogen peroxide (H2O2) with selective oxidation reactions enhances the environmental and economic attractiveness of the use of H2O2 as green oxidant at industrial scale. This tandem reaction improves not only the safety aspects associated to H2O2 storage and transportation but also reduces the capital and operation costs. This review covers the progress in the field focussing on the areas of catalysis development, mechanistic understanding and engineering approaches (such as membrane reactors) for specific systems involving epoxidation of propylene oxide, hydroxylation of benzene, oxygenate synthesis from methane and Fenton processes, highlighting the main challenges to overcome in the near future.
      Graphical abstract image

      PubDate: 2015-01-19T11:56:23Z
  • Photocatalytic organic synthesis in an NMR tube: CC coupling of
           phenoxyacetic acid and acrylamide
    • Abstract: Publication date: July 2014
      Source:Catalysis Today, Volume 230
      Author(s): Andrew Mills , Christopher O’Rourke
      NMR was used to study the semiconductor photocatalytic (SPC) CC coupling of phenoxyacetic acid (PAA) with acrylamide (ACM) in an NMR tube photoreactor. Using an NMR tube with a sol–gel titania inner coating as a photoreactor, this reaction is relatively clean, forming only 1 product, 4-phenoxybutanamide (4-PB), in yields up to 78%. This SPC reaction is used to assess the activity of the sol–gel titania coating as a function of their annealing temperature, which alters the surface area and phase of the titania, and the general reusability of the TiO2 coated NMR tubes. The optimum temperature range for annealing the sol–gel titania films is between 450°C and 800°C, with the maximum yield and rate attained at 450°C. Despite a decrease in the initial rates of formation of 4-PB above an annealing temperature of 450°C, the final product yields remained similar, giving maximum yields within 60min of irradiation. The reusability study reveals that the activity of the sol–gel titania can quickly deteriorate with repeated use due to the adsorption of yellow/brown coloured, insoluble, most likely organic polymeric, material and its screening effect on the underlying photocatalyst. The titania can, however, be restored to its original activity by a simple heat treatment at 450°C for 30min.
      Graphical abstract image

      PubDate: 2015-01-19T11:56:23Z
  • High-pressure operando STM studies giving insight in CO oxidation and NO
           reduction over Pt(110)
    • Abstract: Publication date: Available online 30 August 2014
      Source:Catalysis Today
      Author(s): M.A. van Spronsen , G.J.C. van Baarle , C.T. Herbschleb , J.W.M. Frenken , I.M.N. Groot
      Two catalytic systems have been studied at high pressures on the Pt(110) surface on an atomic level. The first system was the oxidation of CO by O2 towards CO2. In the framework of the second reaction, namely NO reduction, the effect of room temperature exposure of the surface to NO and H2 was investigated. To study these reaction systems at relevant pressures, the ReactorSTM has been used. This is a unique system which consists of a compact STM in which a flow reactor is integrated. The combined reactor with STM is housed inside a conventional vacuum system to allow for traditional surface science preparation and analysis techniques. The STM images obtained with the ReactorSTM under reaction conditions show the lifting of the (1x2) missing row reconstruction by high-pressure CO exposure. The lifting is followed by the formation of the (1x1) metallic Pt(110) structure for high CO/O2 ratios and a (1x2) lifted-row type surface oxide structure for more O2-rich conditions. The room temperature exposure of Pt(110) to H2 results in the formation of a (1x4) missing-row structure and deeper, nested missing rows. The exposure to high-pressure NO removes these missing-row structures.
      Graphical abstract image Highlights

      PubDate: 2015-01-19T11:56:23Z
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2014