for Journals by Title or ISSN
for Articles by Keywords
help

Publisher: Elsevier   (Total: 3039 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  

The end of the list has been reached or no journals were found for your choice.
Journal Cover Catalysis Today
  [SJR: 1.348]   [H-I: 164]   [5 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [3039 journals]
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283


      PubDate: 2017-01-06T12:32:07Z
       
  • Contents list
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283


      PubDate: 2017-01-06T12:32:07Z
       
  • Operando V
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283


      PubDate: 2017-01-06T12:32:07Z
       
  • Catalysis under microscope: Unraveling the mechanism of catalyst de- and
           re-activation in the continuous dimethyl carbonate synthesis from CO2 and
           methanol in the presence of a dehydrating agent
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Dragos Stoian, Atul Bansode, Francesc Medina, Atsushi Urakawa
      The high efficiency of 2-cyanopyridine (2-CP) as dehydrating agent in the direct dimethyl carbonate (DMC) synthesis from CO2 and methanol over CeO2 catalysts has been recently demonstrated with excellent DMC yields (>90%) in both batch and continuous operations. The catalytic reaction is expected to involve a complex three-phase boundary due to the high boiling points of 2-CP and also 2-picolinamide (2-PA) formed by hydration of 2-CP. The catalyst is also known to deactivate noticeably in the time-scale of days during the continuous operation. The aim of this work is to gain visual information of the catalyst under operando conditions by means of an optically transparent, fused quartz reactor to understand the behavior of catalyst deactivation and to learn about the phase behavior of the reaction mixture. The catalytic tests using the fused quartz reactor could reproduce the results observed in a common stainless steel reactor, and the effects of reaction temperature and pressure (up to 30bar) were examined in detail to show that there is an optimum condition (30bar, 120°C) to achieve the best catalytic performance. The visual inspection was further combined with IR and Raman spectroscopic studies to identify the origin of the catalyst deactivation and establish an efficient catalyst reactivation protocol. Interestingly, not coke but 2-PA surface adsorption was found responsible for the catalyst deactivation. The operando visual inspection evidenced that the surface of the CeO2 catalyst particles is constantly wet and also coated with some crystallites (likely of 2-PA) during the reaction, whereas the bulk of the CeO2 particle is still accessible for the reactants and thus available for the reaction.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Twenty years of operando IR, X-ray absorption, and Raman spectroscopy:
           Direct methanol and hydrogen fuel cells
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Neili Loupe, Jonathan Doan, Eugene S. Smotkin
      Mixed metal catalysts in polymer electrolyte fuel cell membrane electrode assemblies were characterized by operando infrared, X-ray absorption and Raman spectroscopy. Windowed direct methanol and hydrogen-air fuel cell assemblies allow for spectral acquisition with controlled potential, temperature and flowing reactant streams to the graphite flow fields. Johnson Matthey Pt and PtRu (1:1), in-house prepared PtRu (1:1 and 3:1), PtRuOs (65:25:10), PtNi (1:1), and a melamine-synthesized FeNC catalyst were studied. The near invariant core structure of phase segregated alloy catalysts over practical fuel cell potentials enable a simultaneous fit of metal component EXAFS to quantitatively characterize core structures: JM PtRu is a face centered cubic lattice with 50% of the Ru in an amorphous phase. Stark tuning of COads as a reaction intermediate and as a surface structure probe elucidates potential dependent co-adsorption of Nafion functional groups on Pt. Operando Raman spectroscopic tracking of membrane hydration at a fuel cathode is facilitated by symmetry-based group mode assignments of Nafion IR bands. Fully hydrated Nafion sulfonate groups have C3V local symmetry. Dehydrated sulfonic acid groups have C1 local symmetry. C3V and C1 IR bands coexist at intermediate states of membrane hydration.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • A decade+ of operando spectroscopy studies
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Anisha Chakrabarti, Michael E. Ford, Daniel Gregory, Rongrong Hu, Christopher J. Keturakis, Soe Lwin, Yadan Tang, Zhou Yang, Minghui Zhu, Miguel A. Bañares, Israel E. Wachs
      Because of the ability to directly probe the catalyst under reaction conditions, operando studies have significantly improved the catalysis literature. The number of operando publications continues to increase. Historical and current operando spectroscopy studies concerning all catalyst types and applications are extensively reviewed.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • An operando FT-IR study of the NOx SCR over Co-HFER and Fe-HFER using
           acetylene as a reducing agent
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Ingrit Castellanos, Olivier Marie
      The selective catalytic reduction by hydrocarbons (HC-SCR) has shown relevant efficiencies in reducing the NOX from the automobiles waste gases, thus emerging as a suitable alternative to urea as a reducing agent. Previous studies by Wang et al. showed that acetylene (C2H2) has a high activity at low temperatures and a satisfactory intracrystalline diffusion over zeolites. The present work investigates C2H2 as a reducing agent under NO, NO2 conditions and a mixture of NO and NO2. Ferrierite zeolites loaded with iron and cobalt ions were evaluated as catalysts by InfraRed (IR) operando and in-situ techniques. This latter technique allowed a clear identification of the vibration bands of the species formed on the surface in reaction conditions. Two different sites for the localization of cations in the Ferrierite were identified from the NO experiment, with only one common to both cations. Regarding C2H2, its interaction with both Lewis and Brønsted sites could be identified. Thanks to the IR operando methodology, it was possible to identify hydrocyanic acid as a relevant intermediate species for the SCR of NOX by C2H2 over Co-HFER. Moreover, the NO oxidation to NO2 was found to be a determining step for the SCR reaction when using the Co loaded catalyst.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Discrimination of active species in liquid-phase hydrogenation on
           supported noble metal catalyst: An operando spectroscopic study on the
           asymmetric hydrogenation of ketopantolactone on Pt/Al2O3 and Pt/C modified
           by cinchonidine
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Laura Rodríguez-García, Konrad Hungerbühler, Alfons Baiker, Fabian Meemken
      An often encountered problem in in situ or operando spectroscopic studies on supported metal catalysts is the discrimination between adsorbates on the support and on the active metal. Here, we show that comparative studies involving differently supported catalysts can help discriminate between species adsorbed on the active metal and the support. The adsorption of the chiral modifier cinchonidine (CD) on Pt/Al2O3 and Pt/C catalysts was investigated by means of operando attenuated total reflection infrared (ATR-IR) spectroscopy. The choice of the support material was found to be crucial, as the strong signal contributions from adsorbates on alumina significantly hampered the spectroscopic analysis of the Pt/Al2O3 catalyst. Instead, the use of a corresponding carbon supported Pt catalyst facilitated the discrimination of adsorbates on the noble metal, due to the virtual absence of adsorbed modifier species on the carbon support. Under reaction conditions of the asymmetric hydrogenation of ketopantolactone, Pt nanoparticles were predominantly covered by CD species anchored via a tilted quinoline ring with respect to the metal surface. Our operando ATR-IR spectroscopic study indicates a strong correlation between the intensity of the signal associated to tilted CD species and the obtained enantioselectivity.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • The promoting effect of Ce in the CO2 methanation performances on NiUSY
           zeolite: A FTIR In Situ/Operando study
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): A. Westermann, B. Azambre, M.C. Bacariza, I. Graça, M.F. Ribeiro, J.M. Lopes, C. Henriques
      The behavior of 5%wt.Ni-impregnated and 5%wt.Ni-15%wt.Ce-impregnated zeolites (of USY type) were investigated by in situ/operando IR spectroscopy, both for CO2 adsorption and under methanation conditions (H2:CO2/4:1) reaction. In situ FTIR and CO2-TPD experiments highlighted that CO2 adsorption is rather poor over NiUSY zeolite, whereas CO2 uptake over CeNiUSY leads to the formation of a large amount of adsorbed carbonates on the CeO2 surface. Mechanistic pathways involved in CO2 methanation over CeNiUSY catalyst are discussed in accordance with infrared spectroscopic data. Under methanation conditions, hydrogen is dissociated on Ni° particles and reacts with hydrogen and bidentate carbonates, leading first to the formation of monodentate formates, and then to methane, by further hydrogenation. No adsorbed carbonyls onto Ni° were detected while a large amount of formates was highlighted from 150°C. The formate decomposition appears to be a kinetic relevant step to the observed kinetics of the CO2 hydrogenation reaction.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • The effect of oxidative and reductive treatments of titania-supported
           metal catalysts on the pairwise hydrogen addition to unsaturated
           hydrocarbons
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Oleg G. Salnikov, Dudari B. Burueva, Evgeniy Yu. Gerasimov, Andrey V. Bukhtiyarov, Alexander K. Khudorozhkov, Igor P. Prosvirin, Larisa M. Kovtunova, Danila A. Barskiy, Valerii I. Bukhtiyarov, Kirill V. Kovtunov, Igor V. Koptyug
      Heterogeneous hydrogenation of unsaturated compounds with parahydrogen is a highly promising technique for boosting the sensitivity of magnetic resonance spectroscopy and imaging by hyperpolarizing reaction products in gaseous and liquid phases, and potentially reaction intermediates as well. This demands an efficient heterogeneous catalyst providing both the high selectivity toward pairwise hydrogen addition (i.e., ability to incorporate both H atoms of H2 molecule in the same product molecule) as well as sufficient overall hydrogenation activity. In this work, we studied the influence of oxidative and reductive treatments of the supported metal catalysts on the NMR signal enhancements provided by parahydrogen-induced polarization (PHIP) effects in hydrogenation of propene, propyne, 1,3-butadiene and 1-butyne. The 5wt% titania-supported Pt, Pd, Rh and Ir catalysts used here were characterized by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Generally, the preliminarily reduced catalysts were found to be more efficient than the oxidized ones. For instance, while the reduced Ir/TiO2 catalyst provided the intense PHIP NMR signals, its oxidized counterpart showed almost no activity in hydrogenation. For the oxidized Pd/TiO2 catalyst, HRTEM revealed the formation of titania pedestals under large (ca. 5–7nm) PdO nanoparticles. At the same time, the small (ca. 1nm) partially reduced Pdδ+ particles were observed on the facets of TiO2 support. These changes in catalyst structure led to a significant decrease in pairwise hydrogen addition selectivity.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Exploring structure and reactivity of Cu sites in functionalized UiO-67
           MOFs
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Luca Braglia, Elisa Borfecchia, Lorenza Maddalena, Sigurd Øien, Kirill A. Lomachenko, Aram L. Bugaev, Silvia Bordiga, Alexander V. Soldatov, Karl Petter Lillerud, Carlo Lamberti
      The exceptional thermal stability of the UiO-67/68-family MOFs makes them ideal candidates to explore post-synthetic functionalization routes aiming to the heterogenization of homogeneous catalysts. We previously demonstrated that a small fraction of the linkers in the UiO-67 MOF can be replaced by bipyridine-dicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the grafting of Pt(II) and Pt(IV) ions in the MOF framework [Chem. Mater., 27 (2015) 1042]. Herein, we investigate a novel Cu-functionalized UiO-67 MOF obtained by a simple synthesis method, consisting in contacting the bpydc-containing UiO-67-bpy MOF with a CuCl2 dihydrate precursor. By combining in situ and operando XAS and FTIR spectroscopies, we assessed the successful incorporation of well-defined Cu complexes in the UiO-67 framework and explored local coordination geometry, redox properties and reactivity of the dominant Cu species formed in different conditions relevant to potential future applications in catalysis. EXAFS fits and XANES simulations, based on DFT-optimized geometries, yielded detailed structural and electronic information on the major Cu-species formed. Data analysis revealed three-coordinated Cu(I) complexes with the bpydc linker of the Cu-UiO-67 MOFs and a Cl− ligand, formed after thermal treatment at 523K in inert gas flow able to efficiently and reversibly form Cu(I)-mono-carbonyl adducts with CO adsorbate.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • In situ XANES study of Cobalt in Co-Ce-Al catalyst applied to Steam
           Reforming of Ethanol reaction
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Arthur E.Pastore de Lima, Daniela C. de Oliveira
      The effect of ceria in cobalt-ceria-alumina catalyst was studied using in situ X-ray near edge spectroscopy (XANES) at Co K-edge and Ce LIII-edge. The introduction of ceria in this catalyst resulted in a significant removal of Co from CoAl2O4 spinel phase to Co and CoO phases. The Co K-edge revealed the symmetry changes in Co according to the temperature and atmosphere in reduction process. We also showed the stability of Co sites as well the oxidation state of ceria in operando steam reforming of ethanol (SRE) reaction. After reduction of Ce4+ to Ce3+, no significant changes were observed by XANES. Gas Chromatography (GC) analysis showed a high ethanol conversion at 500°C, high hydrogen yield and low formation of undesired products as methane and ethylene. The results showed a Co/Ce/Al2O3 catalyst as promising material to be applied in hydrogen production in SRE reaction.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Structure/activity relationships applied to the hydrogenation of
           α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over
           alumina-supported palladium catalysts
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Clément G.A. Morisse, Alastair R. McInroy, Craig Anderson, Christopher J. Mitchell, Stewart F. Parker, David Lennon
      The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4±0.1nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3 catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3 catalyst. The inability of the PdCl2/Al2O3 catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst’s preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • In situ formation of hydrides and carbides in palladium catalyst: When
           XANES is better than EXAFS and XRD
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Aram L. Bugaev, Alexander A. Guda, Andrea Lazzarini, Kirill A. Lomachenko, Elena Groppo, Riccardo Pellegrini, Andrea Piovano, Hermann Emerich, Alexander V. Soldatov, Lusegen A. Bugaev, Vladimir P. Dmitriev, Jeroen A. van Bokhoven, Carlo Lamberti
      In a number of hydrogenation reactions, palladium nanoparticles may undergo a transition to the hydride or the carbide phase, which affects the catalytic properties. In the current work, we determine the structural evolution of an industrial Pd/C catalyst in the presence of hydrogen and acetylene by means of in situ X-ray absorption spectroscopy and X-ray powder diffraction. We observe reversible hydride phase formation and irreversible formation of the carbide phase. The near-edge structure of the absorption spectra (XANES) plays the key role in distinguishing between hydride and carbide phases. We show that the presence of hydrogen and carbon atoms have a direct effect on the near-edge region which is reproduced by theoretical simulations performed in the Monte-Carlo approach.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • ATR-FTIR spectrokinetic analysis of the CO adsorption and oxidation at
           water/platinum interface
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Alejo Aguirre, Claudio L.A. Berli, Sebastián E. Collins
      Attenuated total reflection infrared (ATR-IR) spectroscopy is a powerful tool to investigate reaction pathways in liquid(reactive)/solid(catalyst) systems. Catalysts are commonly deposited on an internal reflection elements (IRE) as layers of powders or as films (e.g. metal film), and they are exposed to the liquid phase reactants. To obtain quantitative information of intrinsic reaction rates, the chemical engineering aspects of an ATR flow-through cell must be evaluated. Particularly, mass transport in the ATR cell has to be characterized. We present here an analysis of the mass transfer from the flowing solution to the surface of the ATR crystal, where the catalyst is deposited. Criteria to determine kinetic parameters under chemical control were developed on the base of non-dimensional Péclet (Pe) and Sherwood (Sh) numbers, and Thiele modulus (φcl ). A Pt thin film deposited on a ZnSe IRE by vapor deposition and a layer of Pt/Al2O3 porous catalyst were used to study the adsorption of carbon monoxide and oxidation of preadsorbed carbon monoxide on aqueous phase. Experimental data of the evolution of the linearly adsorbed CO (2048cm−1) were fitted using a microkinetic model to obtain reaction constants. Results reported here serve as a practical guide to quickly determine the operational limits of an ATR cell with a porous layer of catalyst deposited onto the IRE.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Surface composition changes of CuNi-ZrO2 during methane decomposition: An
           operando NAP-XPS and density functional study
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Astrid Wolfbeisser, Gábor Kovács, Sergey M. Kozlov, Karin Föttinger, Johannes Bernardi, Bernhard Klötzer, Konstantin M. Neyman, Günther Rupprechter
      Bimetallic CuNi nanoparticles of various nominal compositions (1:3, 1:1, 3:1) supported on ZrO2 were employed for operando spectroscopy and theoretical studies of stable surface compositions under reaction conditions of catalytic methane decomposition up to 500°C. The addition of Cu was intended to increase the coke resistance of the catalyst. After synthesis and (in situ) reduction the CuNi nanoparticles were characterized by HR-TEM/EDX, XRD, FTIR (using CO as probe molecule) and NAP-XPS, all indicating a Cu rich surface, even when the overall nanoparticle composition was rich in Ni. Density functional (DF) theory modelling, applying a recently developed computational protocol based on the construction of topological energy expressions, confirmed that in any studied composition Cu segregation on surface positions is an energetically favourable process, with Cu preferentially occupying corner and edge sites. Ni is present on terraces only when not enough Cu atoms are available to occupy all surface sites. When the catalysts were applied for methane decomposition they were inactive at low temperature but became active above 425°C. Synchrotron-based operando NAP-XPS indicated segregation of Ni on the nanoparticle surface when reactivity set in for CuNi-ZrO2. Under these conditions C 1s core level spectra revealed the presence of various carbonaceous species at the surface. DF calculations indicated that both the increase in temperature and especially the adsorption of CHx groups (x=0-3) induce the segregation of Ni atoms on the surface, with CH3 providing the lowest and C the highest driving force. Combined operando and theoretical studies clearly indicate that, independent of the initial surface composition after synthesis and reduction, the CuNi-ZrO2 catalyst adopts a specific Ni rich surface under reaction conditions. Based on these findings we provide an explanation why Cu rich bimetallic systems show improved coke resistance.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Formation and growth of palladium nanoparticles inside porous
           poly(4-vinyl-pyridine) monitored by operando techniques: The role of
           different reducing agents
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Andrea Lazzarini, Elena Groppo, Giovanni Agostini, Elisa Borfecchia, Francesco Giannici, Giuseppe Portale, Alessandro Longo, Riccardo Pellegrini, Carlo Lamberti
      In this work we followed the formation of palladium nanoparticles, starting from palladium (II) acetate precursor, inside a poly(4-vinylpyridine-co-divinylbenzene) polymer in presence of different reducing agents. The formation and growth of palladium nanoparticles in presence of H2 was followed as a function of temperature by simultaneous XANES-SAXS techniques, coupled with DRIFT spectroscopy in operando conditions. It was found that the pyridyl functional groups in the polymer plays a fundamental role in the stabilization of the palladium (II) acetate precursor, as well as in the stabilization of the palladium nanoparticles. The effect of a thermal treatment in alcohol (ethanol and 2-propanol) was preliminarily investigated by means of DRIFT spectroscopy in operando conditions. We found that alcohols act as reducing agents for Pd(OAc)2. The obtained palladium nanoparticles were preliminarily characterized by means of IR spectroscopy using CO as probe molecule.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • In situ Raman spectroscopy evidence of an accessible phase potentially
           involved in the enhanced activity of La-deficient lanthanum orthoferrite
           in 3-way catalysis (TWC)
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Dimitri Blanck, Anke Schön, Anne-Sophie Mamede, Christophe Dujardin, Jean-Philippe Dacquin, Pascal Granger, Jean-François Paul, Elise Berrier
      We report here on an in situ Raman investigation of stoichiometric and La-deficient LaFeO3 solids along model treatments related to three-way catalysis. Whereas the Raman signature of the stoichiometric compound is only slightly modified by the sequence we have applied, the reversible formation of a new phase based on Fe 2 III O 3 in the La-deficient solid was evidenced. This new phase was found to be stabilized under the same experimental conditions which also favor the volumetric expansion of the LFO unit cell. Eventually, this new iron oxide phase was found to be reduced under CO/He mixture and subsequently regenerated under NO.
      Graphical abstract image Highlights

      PubDate: 2017-01-06T12:32:07Z
       
  • Quantitative infrared spectroscopic studies and 2D COS analysis of xylenes
           isomerization over hierarchical zeolites
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Karolina A. Tarach, Kinga Gołąbek, ​Minkee Choi, Kinga Góra-Marek
      The microporous and hierarchical ZSM-5 zeolites were studied with respect to their interaction with o-, m- and p-xylene molecules as well as the catalytic activity in xylenes isomerization process followed by 2D COS analysis of IR spectra. The aspects of mechanism of xylene isomerization reaction have been discussed in the light of the results of 2D COS analysis of IR spectra and catalytic performance of studied zeolites. The ZSM-5 zeolites were characterized by different Si/Al ratio and by various types of generated mesoporosity. This selection assured ability to follow properly the changes in the catalytic performance related not only to acidic properties but also to porosity of the samples. It was shown that the microporous character of zeolites was crucial for high selectivity to the most desired product i.e. p-xylene. In the case of hierarchical zeolites it was confirmed that the formation of by-products as mesitylene and toluene occurred during ortho-xylene isomerization. Furthermore, for hierarchical zeolites the high amount of silanols groups prompted to the coke formation on highly developed external surface.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Surface modifications of cobalt Fischer Tropsch catalyst followed by
           operando DRIFT and chemometrics
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Laurent Lemaitre, Adrien Berliet, Sylvie Maury, Mickael Rivallan
      Operando DRIFT analysis of the surface species observed on Fischer Tropsch catalysts at work has been performed under H2/CO syngas at 503K. Decomposition of the evolution in the IR operando spectra has been done by chemometric analysis in order to depict the modifications occurring on the surface of the nanoparticles as a function of time on stream. Results obtained on three catalysts with different reducibility determined from temperature programmed reduction experiments are confronted in order to correlate the spectral observations to the cobalt surface atoms speciation. Attribution of the IR components in the 2100–1750cm−1 range is confirmed on the basis of the chemometric decomposition. The component falling in the 2068–2064cm−1 range is assigned to CO sorbed onto Co° surface atoms of partially H2-reduced nanoparticles. This component is found to progressively decrease as a function of catalyst time on stream which indicates a progressive reduction of the nanoparticles under syngas at 503K.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • Modelling a reactor cell for operando IR studies: From qualitative to
           fully quantitative kinetic investigations
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Sébastien Thomas, Olivier Marie, Philippe Bazin, Luca Lietti, Carlo Giorgio Visconti, Michele Corbetta, Flavio Manenti, Marco Daturi
      Operando infrared spectroscopy is often used qualitatively to elucidate reaction mechanisms thanks to the observation of the catalyst under actual operating conditions. Besides, in principle such technique can also provide quantitative information that can be used to describe detailed chemical kinetics (spectrokinetic approach). However, the collected kinetic information are relevant only if the gas fluid dynamics inside the reactor cell is well known and can be precisely described. In fact, to perform a reliable kinetic analysis, it is essential to correctly model the flow in the reactor cell and to couple this model with the mass balances. To demonstrate the importance of this aspect, in this work the SSITKA (Steady State Isotopic Transient Kinetic Analysis) approach was exploited within an operando FTIR reactor to study the methanol adsorption onto ceria, herein selected as model probe reaction. A conventional round sample holder with round catalyst wafer and a novel square sample holder with square catalyst pellet have been used. Although the conventional round sample holder shows a satisfactory behaviour, the modified sample holder leads to a virtually perfect plug-flow reactor, which will simplify data computing, provide a better fit of the experimental data and more accurate estimates of the kinetic parameters.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • ATR-IR spectroscopic cell for in situ studies at solid-liquid interface at
           elevated temperatures and pressures
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Kamila Koichumanova, Aura Visan, Bert Geerdink, Rob G.H. Lammertink, Barbara L. Mojet, K. Seshan, Leon Lefferts
      An in situ ATR-IR spectroscopic cell suitable for studies at solid-liquid interface is described including the design and experimental details in continuous flow mode at elevated temperatures (230°C) and pressures (30bar). The design parameters considered include the cell geometry, the procedure to immobilize the catalyst on a cylindrical internal reflection element (IRE), as well as shape and material of choice for the IRE, optics configuration and temperature/pressure control. The hydrodynamics and concentration profiles in the cell were assessed via numerical simulations using incompressible Navier-Stokes equation and convection-diffusion model showing significant deviation from ideal plug flow. Experimental response times at ambient and elevated temperatures derived from ATR-IR spectra agree well with the simulations, demonstrating that the hydrodynamics of the reactor is accurately described. Homogeneous Pt/ZrO2 and AlO(OH) layers were obtained by spray-coating which are stable for at least 12h during testing in 2mL/min water flow. Preliminary spectra collected during aqueous phase reforming of hydroxyacetone demonstrated that the cell can be operated at 230°C and 30bar with simultaneous detection of IR-active species both in the liquid as well as adsorbed on the surface of the catalyst.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • A micropacked-bed multi-reactor system with in situ raman analysis for
           catalyst evaluation
    • Abstract: Publication date: 1 April 2017
      Source:Catalysis Today, Volume 283
      Author(s): Enhong Cao, Gemma Brett, Peter J. Miedziak, John M. Douthwaite, Simon Barrass, Paul F. McMillan, Graham J. Hutchings, Asterios Gavriilidis
      A micropacked-bed multi-reactor platform with integrated portable Raman spectrometer is presented for fast evaluation of catalyst activity and stability for gas/liquid/solid reactions. The silicon-glass microreactor was designed and fabricated so that pockets containing the liquid reaction mixture were created after each packed bed, into which the laser could be directed for Raman spectral acquisition. Using the oxidation of benzyl alcohol as a model reaction, the Raman spectrum was found to be affected both by temperature and by the composition of the multiphase reaction mixture which was related to the reaction conversion. These effects were accounted for by calibrating the Raman spectra at the reaction temperature using mixtures produced by the reactors that were analysed independently by gas chromatography. Fourteen catalysts containing different combinations of Au, Pd and Pt supported on TiO2 prepared by sol-immobilisation (SI) and standard impregnation (SImp) techniques were tested. The results showed that the activity of the catalysts prepared by SI was overall higher than those prepared by SImp, while the activity sequence followed the same pattern: Pd>AuPd>AuPdPt>PdPt>(Au, Pt, AuPt). The Pd and AuPd catalysts from both SI and SImp were stable in 5-h testing, however, for the PdPt and AuPdPt catalysts prepared by SI deactivation was observed.
      Graphical abstract image

      PubDate: 2017-01-06T12:32:07Z
       
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2


      PubDate: 2016-12-07T04:57:13Z
       
  • Contents list
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2


      PubDate: 2016-12-07T04:57:13Z
       
  • Special issue on selected contributions of the 8th International Symposium
           on “Advanced Catalytic Materials”, Cancun, Mexico, August 17–20,
           2015
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): José Manuel Domínguez, Manuel Ramos Murillo, Jorge Ramírez Solís


      PubDate: 2016-12-07T04:57:13Z
       
  • Predicting the structural and electronic properties of transition metal
           monoxides from bulk to surface morphology
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Jin-Jia Liu, Yu Meng, Pengju Ren, Bao Zhaorigetu, Wenping Guo, Dong-Bo Cao, Yong-Wang Li, Haijun Jiao, Zizhong Liu, Meilin Jia, Yong Yang, Aiju Xu, Xiao-Dong Wen
      We systematically investigate the structural, electronic and magnetic properties, bonding analysis, as well as surface morphology of transition metal monoxides (FeO, CoO and NiO) utilizing density functional theory (DFT) with various functionals across from GGA to GGA+U and hybrid functional. Our results reveal that the screened hybrid functional (HSE) could give a reasonable description on structural and electronic properties of these strongly correlated systems when compared to experiments. Local approximation GGA functional fails to yield the accuracy band gaps. GGA+U approximation are rational when given a reasonable U, but the U which reproduce a reasonable band gap often yield a significant error in describing other properties such as lattice constant or magnetic moment. The computed Crystal Orbital Overlap Population (COOP) indicates that cubic FeO and CoO are metastable phase, while the distortion occurs to enhance stability. Based on the reliable functional, the surface morphology of FeO, CoO and NiO are predicted using Wulff construction approach.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • AuCu alloy nanoparticles supported on SiO2: Impact of redox pretreatments
           in the catalyst performance in CO oxidation
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Priscila Destro, Sergio Marras, Liberato Manna, Massimo Colombo, Daniela Zanchet
      The use of colloidal metallic nanoparticles (NPs) in catalysis is an interesting strategy to address complex and fundamental aspects in this field. This synthesis methodology allows an accurate adjustment of size and shape of the metal phase, which can reveal the complex interplay of several factors that usually determine the overall catalytic activity. In the case of bimetallic NPs, another parameter can be finely tuned, namely the composition. The full potential of colloidal NPs in catalysis is indeed extremely exciting; however, crucial aspects related to the removal of the organic protective agents, in order to expose the catalytic sites, as well as the potential drawbacks of remaining synthesis residues on the surface of the NPs have still to be deeply understood. In this work, we evaluated the effect of pretreatments on the activation of AuCu alloy NPs supported on SiO2 applied to catalytic oxidation of CO, showing their significant impact in the final performance and stability of the catalyst.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Hydrogenation of tetralin in presence of nitrogen using a noble-bimetallic
           couple over a Ti-modified SBA-15
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Verónica A. Vallés, Brenda C. Ledesma, Gina A. Pecchi, Oscar A. Anunziata, Andrea R. Beltramone
      Monometallic Pt- and bimetallic Pt-Ir-modified Ti-SBA-15 were used in the hydrogenation of tetralin to decalin in the presence of 150ppm of N as quinoline and indole at 250°C and 15atm of pressure of hydrogen, using a Parr reactor. The catalyst was synthesized using sol-gel method and Ti was added during the synthesis using Tetraethyl Orthotitanate. Pt/Ir was added by wetness impregnation. The catalysts prepared were extensively characterized by X-ray diffraction (XRD), N2 adsorption isotherms, UV–vis-DRS, Raman spectroscopy, XPS, TEM-EDS and TPR. UV–vis-DRS and Raman spectroscopy confirmed that Ti was incorporated in tetrahedral coordination in the framework of the SBA-15. The analysis showed that the mesoporous structure was maintained after metal incorporation and Ti incorporation helps to reduce significantly the size of the metals clusters and improves its dispersion considerably. Pt-Ir/Ti-SBA-15 was the most active catalyst. The experimental data were quantitatively represented by a modified Langmuir-Hinshelwood type rate equation. The preliminary results show these materials as a promising catalyst for HDT reactions.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Vanadium and titanium oxide supported on mesoporous CMK-3 as new catalysts
           for oxidative desulfurization
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Lorena Rivoira, Juliana Juárez, Horacio Falcón, Marcos Gómez Costa, Oscar Anunziata, Andrea Beltramone
      Vanadium supported-CMK-3 catalysts with vanadium loading of 1–7wt.% were studied in the oxidative desulfurization (ODS) of dibenzothiophene as a model sulfur compound. The activity was compared with titanium supported-CMK-3. Structural and textural characterization of the catalysts was performed by means of N2 adsorption, XRD, UV–vis–DRS, Raman spectroscopy, XPS, TEM and TPR. The dispersion and the nature of the vanadium species depend on the V loading, so does the catalyst activity. Vanadium supported-CMK-3 with 7wt.% of vanadium loading was the most active catalyst for ODS of DBT using hydrogen peroxide (H2O2) as oxidant and acetonitrile as solvent. 100% of DBT elimination was attained at short time in mild conditions. Carbon ordered mesoporous CMK-3 with high surface area and high pore volume promotes a very good anchorage of metallic oxides in the carbons framework reaching high active sites distribution and more stable nanoclusters. The reusability of the catalyst indicates that V-CMK-3 is a potential catalyst for the ODS of dibenzothiophene.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • MoOx-VOx based catalysts for the oxidative desulfurization of refractory
           
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Marco A. Alvarez-Amparán, Luis Cedeño-Caero
      The oxidative desulfurization (ODS) process has emerged as a new technology to achieve ultra-low sulfur levels in diesel fuels. This work presents the performance of MoOx-VOx based catalysts in the ODS process and an evaluation of the interaction between MoOx and VOx in these bimetallic catalysts, using Al2O3 as catalytic support, and hydrogen peroxide and tertbutil-hidroperoxide as oxidant agents. The catalysts were characterized by scanning electron microscopy (SEM-EDX), nitrogen physisorption, X-ray diffraction (XRD) and temperature programed reduction (TPR). The catalytic activity of MoOx-VOx/Al2O3 was higher than the monometallic catalysts: MoOx/Al2O3 and VOx/Al2O3. The characterization results suggested that in MoOx-VOx catalysts the molybdenum species interact strongly with the support and that the vanadium species were distributed mainly as isolated-vanadium species, due to the interaction between VOx and MoOx.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Titania nanotubes decorated with anatase nanocrystals as support for
           active and stable gold catalysts for CO oxidation
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Alberto Sandoval, Rodolfo Zanella, Tatiana E. Klimova
      Gold nanoparticles supported on titania nanostructured materials were prepared, characterized and tested in CO oxidation. Two nanostructured supports were used: titania nanotubes (TNT) synthesized by the Kasuga method and titania nanotubes decorated with TiO2 anatase nanocrystals prepared by post-synthetic treatment of TNT with 0.05M HNO3 solution at 70°C for 48h (TNT-T). Gold catalysts with 4wt.% of Au nominal loading were prepared by deposition-precipitation with urea. A reference Au catalyst supported on TiO2 Degussa P-25 was also prepared. Supports and catalysts were characterized by N2 physisorption, XRD, UV–vis and Raman spectroscopy, TPR, SEM-EDX and HRTEM. HRTEM characterization showed that gold nanoparticles with an average size between 2 and 7nm were obtained in all catalysts making them suitable for CO oxidation. Catalytic tests showed differences in activity and stability among the prepared catalysts. The Au/TNT catalyst presented poor activity for CO oxidation, meanwhile the Au/TNT-T catalyst showed higher activity than the Au/TiO2 Degussa P-25, especially at a low temperature interval (−10 to 100°C). Stability tests performed for Au/TNT-T and Au/TiO2 Degussa P-25 catalysts at 25°C revealed higher stability of the Au/TNT-T catalyst, attributed to low sintering of gold nanoparticles.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Pretreatment impact on the morphology and the catalytic performance of
           hybrid heterodimers nanoparticles applied to CO oxidation
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Luelc Souza da Costa, Daniela Zanchet
      In this work, we applied seeded growth colloidal method to produce Au-FexOy dumbbells nanoparticles (DBNPs). The colloidal DBNPs were characterized and deposited on SiO2 to evaluate the effect of Au-FexOy interface on the catalytic activity in CO oxidation (CO+1/2O2 →CO2). In particular, we addressed the impact of redox pretreatments in the catalytic activity. Catalytic data showed that the catalyst was not very active after the first oxygen activation but after a reduction step there was a substantial increase in the catalyst activity. A detail characterization showed that DBNPs suffered great morphological and structural changes with the formation of core/shell Au-FexOy structures, in which the FexOy shells were irregular and presented lower crystallinity. The results suggest that the increase in catalytic activity was related to the formation of a more extended Au-FexOy interface after the pretreatments, thereby increasing the amount of active sites.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Modified gelcasting of microwave assisted synthesized sulfur-doped anatase
           for photocatalytic degradation of organic compounds
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): A. Cortéz-Lorenzo, L. Escamilla-Perea, K. Esquivel-Escalante, R. Velázquez-Castillo
      Sulfur-doped anatase nanoparticles were synthesized using titanium isopropoxide and thiourea, reactions were done through a microwave assisted hydrothermal method to control the morphology, crystallinity and the dimensions. Pure anatase was also obtained as a reference material for photocatalytic characterization. All synthesis reactions were carried out at 215°C, using a potency of 600W during 60min. Crystalline phases were identified by XRD and by HRTEM the crystal structure was studied, and the dimensions of nanocrystal were determined. The images recorded were analyzed with a Digital Micrograph software. Subsequently, the synthesized anatase was used in order to obtain ceramics with controlled porosity through the modified gelcasting process. This process was performed in order to reduce the photocatalyst loss when organic compound degradation reactions were carried out. The anatase was mixed with polymers, dispersants and solvents to produce a reticulated gel which made the anatase easy to be molded and consequently, ceramic plates were formed. The ceramic porosity was observed with a SEM and their photocatalytic activities were evaluated by photodegradation reactions of methyl red dye in water solution. All these reactions lasted 3h and samples were collected at different times during the reaction. Color removal was evaluated with UV–vis measurements following the color disappearing at 434nm wavelength. Significant differences in photocatalytic properties were observed between doped and pure anatase despite the low concentration of sulfur (0.1% weight.)
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Catalytic activity of palladium nanocubes/multiwalled carbon nanotubes
           structures for methyl orange dye removal
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): O. Arciniega Cano, C.A. Rodríguez González, J.F. Hernández Paz, P. Amezaga Madrid, P.E. García Casillas, A.L. Martínez Hernández, C.A. Martínez Pérez
      In this work, the synthesis and catalytic activity measurements of a nanostructured material formed by palladium (Pd) nanocubes supported on multiwalled carbon nanotubes (MWCNTs) for removing methyl orange as a model of organic contaminant from aqueous solution are presented. The nanocubes were synthesized by a reduction process of H2PdCl4 and a non-covalent method that involves a surfactant functionalization of the carbon nanotubes was used to produce the nanostructured material. Characterization was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis. Results showed well dispersed Pd nanocubes, in the range of 15–25nm, bonded onto the carbon nanotubes. The catalytic experiments exhibited 81.9% methyl orange removal after 8min and 99% after 60min using 1mg of the nanostructured material per every 20mg/L of the dye.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Effect of the calcination temperatures of the Fe-based catalysts supported
           on polystyrene mesoporous carbon for FTS Synthesis
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Marcia G.A. Cruz, Fabiano A.N. Fernandes, Alcemira C. Oliveira, Josue M. Filho, Alcineia C. Oliveira, Adriana F. Campos, E. Padron-Hernandez, Enrique Rodríguez-Castellón
      The porous Fe-based catalysts supported on polystyrene mesoporous carbon were studied in the Fischer-Tropsch Synthesis. The solids were pretreated at different calcination temperatures and their characterizations were examined by X-ray diffraction (XRD), Raman spectroscopy, Scanning and Transmission electron microcopies (SEM and TEM), textural properties, elemental composition by X-ray dispersive spectroscopy (EDS), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). It was shown that the preexistent carbides phases, obtained upon using elevated temperatures of calcinations procedure, were not completely reoxidized during the reaction, while the formation of carbides through the polymeric carbon reaction with magnetite and/or metallic iron resulted in highly active catalyst for FTS.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • Partial oxidation of methanol over copper supported on nanoshaped ceria
           for hydrogen production
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 2
      Author(s): Daniel G. Araiza, Antonio Gómez-Cortés, Gabriela Díaz
      Copper (5wt.%) supported on ceria nanopolyhedra, nanorods and nanocubes was studied as catalyst for hydrogen production from partial oxidation of methanol (POM). Supports were prepared by hydrothermal approach and addition of copper was achieved by wet impregnation. Catalysts were characterized by EDS, XRD, TEM, HRTEM, N2 adsorption, H2-TPR, N2O Chemisorption, CH3OH-TPD, Raman and DRIFT spectroscopies. POM reaction was studied at O2/CH3OH molar ratio of 0.3 as a function of temperature in the range 160–280°C and as a function of time on stream for 24h at 265°C. As a result of the support morphology the following features were observed: (i) variety of copper species on the surface of the nanoshaped ceria; (ii) different capability and stability of carbonate formation; (iii) desorption of products from CH3OH-TPD at different temperatures; (iv) activity, selectivity and stability variations in the POM reaction related to oxidation state of the copper phase. At constant temperature, polyhedra and rod-like catalysts show similar performance, but the former one produces lower amounts of CO.
      Graphical abstract image

      PubDate: 2016-12-07T04:57:13Z
       
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1


      PubDate: 2016-11-30T04:47:36Z
       
  • Contents list
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1


      PubDate: 2016-11-30T04:47:36Z
       
  • Catalysis for water purification
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Kwang-Ho Choo, Hyunwoong Park, Wonyong Choi


      PubDate: 2016-11-30T04:47:36Z
       
  • Well-organized, mesoporous nanocrystalline TiO2 on alumina membranes with
           hierarchical architecture: Antifouling and photocatalytic activities
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Rizwan Ahmad, Jin Kyu Kim, Jong Hak Kim, Jeonghwan Kim
      We report the development of improved antifouling and photocatalytic membranes based on an organized mesoporous TiO2 (om-TiO2) layer on a porous alumina (Al2O3) support. The om-TiO2 layer was templated by an amphiphilic graft copolymer, i.e., poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), and was 50–70nm in pore size with high porosity and good pore interconnectivity. The precoating of poly(vinyl pyrrolidone) (PVP) on a porous alumina support was the key to providing a flat platform and improving the adhesion properties of alumina with TiO2, which allowed for the formation of om-TiO2 membranes. Fouling of photocatalytic om-TiO2 on the alumina membrane was also investigated using a laboratory-scale photocatalytic dead-end filtration reactor using a model dye compound. The fouling rate was observed to be much slower for the om-TiO2 membrane compared to the bare alumina support under UV illumination during 6h of membrane operation. The PVP precoating on the alumina support improved the permeation quality of the om-TiO2 membrane. The improved removal of the organic dye compound was thought to result from the enhanced adsorption capability of organic compounds and subsequent photocatalytic reactions on the om-TiO2 layer. However, UV illumination performed for longer than 6h gradually increased the fouling rate due to the deposition of the organic dye compound on the membrane surface, and prohibited the accessibility of the UV light to the TiO2 layer.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Synthesis of multiwall carbon nanotubes/TiO2 nanotube composites with
           enhanced photocatalytic decomposition efficiency
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Thillai Sivakumar Natarajan, Joon Yeob Lee, Hari C. Bajaj, Wan-Kuen Jo, Rajesh J. Tayade
      Multiwall carbon nanotubes (MWCNT)-loaded TiO2 nanotube (TNT) composites were synthesized by hydrothermal method. Scanning electron microscopy and transmission electron microscopy revealed the tubular morphology of the prepared TNT and MWCNT/TNT composites, which was further confirmed by the increase in their surface area. The MWCNT/TNT photocatalysts show high photocatalytic decomposition efficiency (PDE) for the degradation of rhodamine 6G (RhB-6G) dye, with excellent stability and reusability. Among the MWCNT/TNT composites, 10% loading of MWCNT results in a significantly higher PDE (89%) as compared with that of bare TNT (78%), Degussa P-25 TiO2 (P25, 60%), and TiO2 nanoparticles (56%). The enhanced PDE of MWCNT/TNT composites is due to the ability of the MWCNTs to promote the electron transfer process and reduce the electron-hole pair recombination rate, as also confirmed by photoluminescence measurements. Moreover, chemical oxygen demand (COD) and total organic carbon (TOC) analyses were performed to verify the RhB-6G dye degradation. Tubular morphology, enriched adsorption, synergic effect, and efficient separation of photogenerated electron-hole pairs account for the enhanced PDE of MWCNT/TNT composites in the decomposition of RhB-6G dye under the current experimental conditions.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Is surface fluorination of TiO2 effective for water purification? The
           degradation vs. mineralization of phenolic pollutants
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Jungho Ryu, Wooyul Kim, Jaesung Kim, Jinjung Ju, Jungwon Kim
      The photocatalytic activity of surface fluorinated TiO2 (F-TiO2) for both the degradation and mineralization of bisphenol A (BPA) was compared with that of pure TiO2. The degradation rate of BPA (i.e., the conversion rate of BPA to intermediates) was enhanced, but the mineralization rate (i.e., the conversion rate of BPA to CO2) was reduced by surface fluorination. These behaviors are different from the general trend in photocatalysis, in which the photocatalyst with a higher activity for the degradation also shows a higher activity for the mineralization. The surface fluorination of TiO2 enhanced the production of the hydroxyl radical (OH), which is primarily responsible for the degradation of BPA, by altering the OH generation pathway. However, the lower mineralization on F-TiO2, which produced more OH, implies that the role of OH in the photocatalytic mineralization process is minor. The production of superoxide/hydroperoxyl radical (O2 −/HO2 ), which is suggested as an essential oxidant for the mineralization of phenolic pollutants, by F-TiO2 was lower than that exhibited by pure TiO2. The reduced photocurrent (I ph) generation and the enhanced H2O2 production on F-TiO2 indicate that fluorides on the TiO2 surface reduce the interfacial electron transfer rate (i.e., the production of O2 −/HO2 ) and enhance the reduction of O2 −/HO2 to H2O2. The degradation rate increased, but the mineralization efficiency decreased with increasing the surface coverage of fluorides, which depends on the pH and fluoride concentration in the solution. The reduced mineralization efficiency of other phenolic pollutants (4-chlorophenol, phenol, methylene blue, rhodamine B, and acid orange 7) was also observed on F-TiO2. This result indicates that the negative effect of surface fluorination on the mineralization of phenolic pollutants is pervasive and is not restricted to BPA.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Anodization of bismuth doped TiO2 nanotubes composite for photocatalytic
           degradation of phenol in visible light
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Imran Ali, Seu-Run Kim, Sung-Pil Kim, Jong-Oh Kim
      Bismuth doped TiO2 photocatalyst was synthesized in a one-step electrochemical anodization method. Bismuth nitrate Bi(NO3)3 was used as a bismuth source. The obtained samples were characterized by FE-SEM, XRD, EDX and XPS. The optimum synthesis conditions for bismuth doping were 1.0M bismuth nitrate in an ethylene glycol electrolyte with anodization at 40V for 2h. Compared with undoped TiO2 nanotubes, bismuth doped TiO2 photocatalyst showed a higher photocatalytic activity by a factor of 4.0 for phenol degradation under visible light irradiation. The optimum phenol degradation using a photoelectrocatalytic method was observed at a 0.5V external bias, and this degradation rate was 5.2 times faster than that observed for undoped TiO2 nanotubes. The doped bismuth TiO2 nanotubes are favorable for the separation of photo-induced electrons and holes, reducing the recombination of charges, and promoting the formation of hydroxyl radicals and superoxides that degrade phenol.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Stabilization of Pickering emulsion with surface-modified titanium dioxide
           for enhanced photocatalytic degradation of Direct Red 80
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Mohsin Nawaz, Waheed Miran, Jiseon Jang, Dae Sung Lee
      Surface modification of titanium dioxide (TiO2) was carried out with salicylic acid (SA) to generate an efficient Pickering emulsion (PE)-based photocatalytic system. The PE was stabilized with 0.5 and 1.0mgmL−1 of TiO2 and SA-TiO2 by using cyclohexane and a synthetic aqueous Direct Red 80 (DR 80) solution (0.4:1) as the oil and water phases, respectively. The photocatalytic activity of solution-dispersed TiO2 was compared with that of the PE-based photocatalytic system for DR 80 degradation. In almost all PE-based photocatalytic systems, 100% color removal of DR 80 was observed within 15–60min, compared to 76% and 100% color removal, achieved after 120min, using 0.5 and 1.0mgmL−1 solution-dispersed TiO2, respectively. The estimated reaction rates of the PE-based photocatalytic system, as calculated using the Langmuir–Hinshelwood kinetics model, were almost double to those obtained for solution-dispersed TiO2. However, the addition of a free oil phase adversely affected the photocatalytic activity, and the lowest DR 80 degradation percentage was observed using 0.5 or 1.0mgmL−1 TiO2. The results demonstrated that a functional PE was successfully stabilized with SA-TiO2, and enhanced photocatalytic degradation of the azo dye was achieved in an effective and novel way.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Decomposition of acetaminophen (Ace) using TiO2/UVA/LED system
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Pei Xiong, Jiangyong Hu
      For photocatalytic degradation of organic pharmaceutical pollutants in wastewater, an important limitation is low photonic efficiency. To solve this problem, using periodic illumination is a good option. However, due to the nature of widely applied traditional mercury lamp, which cannot be turned on and off efficiently, the study of periodic illumination was limited. In this research, ultraviolet-A/light emitting diode (UVA/LED) lamp was introduced and a TiO2/UVA/LED photocatalytic system was setup for acetaminophen (Ace) degradation study. The background study was conducted, which included the effects of H2O2, humic acid and bicarbonate ion concentrations. Different periodic pulse frequencies were applied, results in this study shows that smallest duty cycle (0.2) and shortest cycle time (20ms) gave the highest photonic efficiency for photocatalytic degradation of Ace in the studied range. The effect of additional H2O2 was also studied. H2O2 added into the heterogeneous reaction system enhanced both decomposition rate and photonic efficiency under both continuous illumination mode and periodic illumination mode. The enhancement effect of H2O2, however, was found more obvious for controlled periodic illumination, especially for small duty cycles and short cycle times. In addition, by the addition of H2O2, the mineralization of Ace was accelerated probably due to the increase of hydroxyl radical concentration.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Electrocatalytic activities of Sb-SnO2 and Bi-TiO2 anodes for water
           treatment: Effects of electrocatalyst composition and electrolyte
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Yong Yoon Ahn, So Young Yang, Chimyung Choi, Wonyong Choi, Soonhyun Kim, Hyunwoong Park
      This study compares the electrocatalytic behavior and performance of metal-doped oxide anodes in widely employed electrolytes (i.e., Na2SO4, NaClO4, and NaCl). Sb-doped SnO2 (Sb-SnO2), Bi-doped SnO2 (Bi-SnO2), or Bi-doped TiO2 (Bi-TiO2) are coated onto a Ta-doped IrO2 (Ta-IrO2) electrode using identical fabrication procedures involving coating and annealing cycles. The resultant electrodes display porous morphologies with interparticle connections. Crystalline phases of Sb-associated oxides are not evident in Sb-SnO2, whereas distinct Bi2O3 phases are observed in Bi-SnO2 and Bi-TiO2 because the radius of Bi3+ is larger than those of the base metals. Sb-SnO2 exhibits the highest electrocatalytic activity for the decomposition of phenol irrespective of the type of electrolyte, whereas the activity of Bi-SnO2 is always poor. The activity of Bi-TiO2 is poor in sulfate and perchlorate electrolytes; in contrast, it is remarkably enhanced and comparable to that of Sb-SnO2 in chloride electrolyte. Such chloride-specific activity of Bi-TiO2 is attributed to the effective generation of reactive chlorine species, whereas the generation of OH radicals is limited. On the other hand, Sb-SnO2 effectively catalyzes the generation of OH radicals, leading to mediated generation of reactive chlorine species. The decomposition of phenol is further examined in terms of reaction intermediates and CO2 production using Sb-SnO2 and Bi-TiO2 anodes in sulfate and chloride electrolytes. The electrocatalyst and electrolyte-dependent mechanism is discussed.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Electron shuttling catalytic effect of mellitic acid in zero-valent iron
           induced oxidative degradation
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Seung-Hee Kang, Alok D. Bokare, Yiseul Park, Chi Hun Choi, Wonyong Choi
      The enhanced oxidation capacity of zero-valent iron (ZVI) using mellitic acid (MA) as an electron shuttle catalyst was investigated using 4-chlorophenol (4-CP) as a model pollutant. In the presence of MA, enhanced electron transfer from ZVI surface to molecular oxygen resulted in higher production of hydrogen peroxide (H2O2), which subsequently increased the effective concentration of hydroxyl radical (HO) generated through the Fenton-type reaction. The possible role of MA as an efficient electron shuttle was supported by cyclic voltammetric estimation of MA reduction potential (E0 =−0.184VNHE) and corroborated with photocurrent measurements in the ZVI suspension. Control experiments using Fe(II) ions instead of ZVI demonstrated that the presence of MA in the Fe(II)/H2O2 homogeneous system had no significant effect on the 4-CP oxidation efficiency. This indicates that the formation of a Fe(II)-MA complex does not contribute to the 4-CP oxidation pathway. The primary role of MA in the ZVI/O2 system seems to mediate the electron transfer from the ZVI surface to dioxygen. It implies that organic species containing multiple carboxylic ligands (species like MA or its structural analogues) may function as an electron shuttle in the ZVI/O2 catalytic system.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Manganese oxide nanorods as a robust Fenton-like catalyst at neutral pH:
           Crystal phase-dependent behavior
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Eun-Ju Kim, Dasom Oh, Chung-Seop Lee, Jianyu Gong, Jungwon Kim, Yoon-Seok Chang
      Manganese oxide nanorods with different crystal phases (α-, β-, γ-, and δ-MnO2) were prepared via a mild hydrothermal method, and examined as heterogeneous catalysts for the decomposition of H2O2 into active radicals and concomitant degradation of methylene blue (MB) dye at neutral pH. The catalytic activity of MnO2 nanorods was highly dependent upon their crystal structures, following the order of γ-MnO2 > β-MnO2 > α-MnO2 > δ-MnO2. Complete degradation of MB was achieved with γ-MnO2 in a short duration of 20min. Furthermore, γ-MnO2 exhibited much higher activity compared to iron-containing nanoparticles (Fe° and Fe3O4) and several reported catalysts in the literature. The observed trend in catalyst performance was discussed in terms of surface area, degree of crystallinity, and exposed facets. It was found that γ-MnO2 showed considerable activity over a broad range of pH and temperature as well as desired reusability for four consecutive cycles. Quenching studies indicated that hydroxyl radicals (OH) played a major role in the degradation of MB. These results provide important insight into the design of more efficient manganese oxide catalysts for wastewater treatment.
      Graphical abstract image

      PubDate: 2016-11-30T04:47:36Z
       
  • Evaluation of the O3/graphene-based materials catalytic process: pH effect
           and iopromide removal
    • Abstract: Publication date: 15 March 2017
      Source:Catalysis Today, Volume 282, Part 1
      Author(s): Y. Yoon, H. Oh, Y.-T. Ahn, M. Kwon, Y. Jung, W.K. Park, T.-M. Hwang, W.S. Yang, J.-W. Kang
      Graphene-based materials, including graphene oxide (GO), reduced-graphene oxide (rGO), and non-oxidative graphene (nOG) were evaluated for catalytic ozonation in water solutions. Among the graphene-based materials evaluated for catalytic ozonation, it was confirmed that rGO was unsuitable to apply to the ozone (O3)/graphene-based materials catalytic process because the high electron mobility of rGO prevented the transformation of O3 into hydroxyl radicals (OH). On the other hand, GO, which had sufficient oxygenated functional groups on the surface, decomposed and generated the most amount of O3 and OH, respectively. Although O3/nOG process produced a lower amount of OH than O3/GO process, nOG was more effective than GO for the transformation yields of O3 into OH. Furthermore, nOG could generate OH not only in the bulk phase, but also on the surface of nOG during catalytic ozonation. However, iopromide (IPM) was effectively removed during O3/GO process due to the more OH generated in the bulk phase than O3/nOG process.

      PubDate: 2016-11-30T04:47:36Z
       
 
 
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
 
Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs
Your IP address: 54.197.136.128
 
About JournalTOCs
API
Help
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016