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Journal Cover Catalysis Today
  [SJR: 1.348]   [H-I: 164]   [8 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0920-5861
   Published by Elsevier Homepage  [3089 journals]
  • IFC - Editors; Editorial Board & scope
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301


      PubDate: 2017-12-13T08:24:14Z
       
  • Contents list
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301


      PubDate: 2017-12-13T08:24:14Z
       
  • Editoral special issue CarboCat-VII
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Bastian J.M. Etzold, Dominique Begin


      PubDate: 2017-12-13T08:24:14Z
       
  • Mesoporous carbon doped with N,S heteroatoms prepared by one-pot
           auto-assembly of molecular precursor for electrocatalytic hydrogen
           peroxide synthesis
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Laura Roldán, Lai Truong-Phuoc, Alejandro Ansón-Casaos, Cuong Pham-Huu, Enrique García-Bordejé
      A bottom-up approach based on hydrothermal carbonization of organic molecules has been used to prepare carbon materials doped with either nitrogen or sulfur or both. To generate mesopores, ZnCl2 has been used as removable structure-directing agent. The final mean mesopore size depended on the type of dopant element. The doped materials exhibited remarkable activity as electrocatalyst in oxygen reduction reaction with nearly complete selectivity to H2O2 synthesis. Two pyrolysis temperatures (973K and 1173K) were used that yield materials with different electric conductivity, dopant content and porosity but comparable electrocatalytic performance. N-doped catalyst with an intermediate nitrogen content (4wt%) and around 80% of pore volume in the mesopore range provided the best performance among the catalysts tested.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Evaluation of ORR active sites in nitrogen-doped carbon nanofibers by KOH
           post treatment
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Navaneethan Muthuswamy, Marthe E.M. Buan, John C. Walmsley, Magnus Rønning
      Oxygen reduction on N-doped carbon nanomaterials is believed to take place at either N-centered active sites (C-Nx) or Fe-centered active sites (Fe-Nx). In this work the origin of the oxygen reduction on nitrogen-doped carbon nanofibers (N-CNFs) is investigated by removing nitrogen and iron from the N-CNF surface using high temperature KOH treatment. The activities for the oxygen reduction reaction (ORR) in 0.5M H2SO4 are correlated with the XPS results and discussed with respect to the contribution from C-Nx and Fe-Nx active sites. Increasing the time and temperature of the KOH treatment decreased the iron and nitrogen content at the N-CNF surface. The contribution from Fe-Nx active sites was found to be minor compared to the C-Nx active sites as the KOH-treated N-CNFs with no iron in the surface still showed considerable ORR activity. Furthermore, the activity was maintained when the fraction of pyridinic-N was greatly reduced compared to quaternary-N. Finally, even when no iron or nitrogen could be detected by XPS, 50% of the initial oxygen reduction activity of the N-CNFs persisted. It is therefore suggested that there are active sites not originating from iron or nitrogen atoms, but rather from a distinct carbon environment.
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      PubDate: 2017-12-13T08:24:14Z
       
  • CoMn-LDH@carbon nanotube composites: Bifunctional electrocatalysts for
           oxygen reactions
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Marta F.P. Duarte, Inês M. Rocha, José L. Figueiredo, Cristina Freire, M. Fernando R. Pereira
      In the present work, a set of five Layered Double Hydroxides, LDH, containing Co and Mn derived electrocatalysts was prepared for the oxygen electrode, evaluating their performances in ORR and OER. A LDH with a Co/Mn ratio of 4, CoMn4, was the reference electrocatalyst of the set, presenting the typical hydrotalcite structure with a trace of MnCo2O4, with a surface area of 76m2 g−1. HNO3 oxidized carbon nanotubes (CNT_HNO3) and CNT_HNO3 with a low content of carboxylic acids (CNT_ HNO3tt350), were incorporated into the CoMn4 synthesis, obtaining CoMn4@CNT_HNO3 and CoMn4@CNT_HNO3tt350 with surface areas of 111 and 167m2 g−1, respectively. According to X-ray diffraction (XRD), the oxide phase of CoMn4@CNT_HNO3 is composed by a mixture of LDH with MnCo2O4, while the low%COOH on the carbon surface promoted the synthesis of LDHs as the only oxide structure at CoMn4@CNT_HNO3tt350. Moreover, after a thermal treatment of the latter electrocatalyst, the LDHs were totally converted into MnCo2O4. All electrocatalysts showed to have activity over both oxygen reactions when the KOH solution was saturated with O2. A detailed ORR study showed that the LDH structures mixed with CoMn oxides, present at CoMn4@CNT_HNO3, play a relevant role in ORR, exhibiting an onset potential, EORR , of −0.274V. On the other hand, CoMn4@CNT_HNO3tt350 led to a four-electron mechanism for ORR, similar to the Pt/C standard. The best OER potential (0.636V) was also obtained for CoMn4@CNT_HNO3tt350. Regarding the oxygen electrode bifunctionality, a good balance between ORR and OER was observed for the CoMn4@CNT_HNO3tt350_N2 composite.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Template growth of nitrogen-doped mesoporous graphene on metal oxides and
           its use as a metal-free bifunctional electrocatalyst for oxygen reduction
           and evolution reactions
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Hao-Fan Wang, Cheng Tang, Qiang Zhang
      Metal-free electrocatalyst is an emerging energy material to replace precious metal for effective oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in a working electrochemical energy conversion device. Developing an effective bifunctional catalyst with abundant highly active sites and full exposure to reactants is strongly considered. Herein a nitrogen-doped mesoporous graphene framework (NMGF) was proposed with intrinsic N/O heteroatoms and abundant topological defects for metal-free ORR/OER. The NMGF was fabricated by direct chemical vapor deposition on MgO template. The as-obtained NMGF exhibited high porosity with a large specific surface area of 1440m2 g−1 as well as a high electrical conductivity of 57.0Scm−1. This unique structure is demonstrated to possess several advantages, including plentiful active centers due to defects and heteroatoms, improved utilization efficiency by very high electrochemically active surface area and hydrophilic surface, facilitated ion diffusion through interconnected pores and smooth electron transportation in the highly conductive 3D framework, thereby leading to superior ORR and OER bifunctional activity. The ORR half-wave potential was 0.714V, and the potential to reach 10.0mAcm−2 OER current density was 1.664V with the potential gap of 0.95V. This bifunctional performance was better than routine precious metal-based catalysts (e.g. Pt/C and IrO2) for oxygen redox reaction.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Few-layer sp2 carbon supported on Al2O3 as hybrid structure for
           ethylbenzene oxidative dehydrogenation
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Jia Wang, Jiangyong Diao, Jiayun Zhang, Yajie Zhang, Hongyang Liu, Dang Sheng Su
      Hybrid materials consisting of few-layer sp2 carbon supported on Al2O3 can potentially display comparable performance with nanodiamonds for the oxidative dehydrogenation of ethylbenzene. The hybrid structure could be easily prepared by fast coking method using ethanol as a precursor and ɣ-Al2O3 with high specific surface areas as a template. In this case, ɣ-Al2O3 plays the role of 3D support for depositing few-layer graphene-like structure. The hybrid structure exhibiting similar structure with nanodiamonds calcined at high temperature is further used as a metal-free catalyst for the oxidative dehydrogenation of ethylbenzene to styrene. The yield rate of styrene normalized by the specific area on Al2O3@C is 0.044mmolm−2 h−1 (TOF=4.13h−1) which is two times of that on nanodiamonds (0.020mmolm−2 h−1, TOF=3.27h−1). Considering the low cost process and good catalytic performance, the hybrid nanostructure may be a promising candidate to be applied in the oxidative dehydrogenation of ethylbenzene.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Structure-performance relationship of nanodiamonds @ nitrogen-doped
           mesoporous carbon in the direct dehydrogenation of ethylbenzene
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Yuefeng Liu, Housseinou Ba, Jingjie Luo, Kuang-Hsu Wu, Jean-Mario Nhut, Dang Sheng Su, Cuong Pham-Huu
      Nanocarbon materials have been reported as an alternative robust metal-free catalyst in the field of the catalytic dehydrogenation with improved catalytic performance as well as stability. In this study, the hybrid metal-free catalyst consisting of dispersed nanodiamonds within a nitrogen-doped mesoporous carbon (ND@NMC) phase was investigated. Such material with high effective surface area and porosity was prepared under different thermal treatment temperatures and further evaluated for the direct dehydrogenation (DDH) of ethylbenzene (EB) to styrene (ST). The characterization techniques such as N2 adsorption-desorption, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and Raman spectroscopic analysis were used to investigate the surface properties and structures of the as-prepared ND@NMC composites. The ND@NMC-700 catalyst annealed at 700°C presented a ST specific reaction rate and a relative areal activity of 5.8mmolST gcatalyst −1 h−1 and 0.28μmolST m−2 h−1 with a ST selectivity of 99.6%, which is the highest DDH activity among the investigated nanocarbons including ND, carbon nanotubes, NMC and ND@MC (ND covered by mesoporous carbon) catalysts. The superior dehydrogenation performance could be attributed to the high dispersion of the metal-free nanodiamond centers within the NMC layer which provided a well surface contact with the reactant. It can also be confirmed that the rational contents of ketone (CO) functional groups, as well as the opened porous network in ND@NMC-700 catalyst resulted to the superior DDH activity and styrene selectivity. Moreover, the presented nitrogen groups are beneficial for construction of surface defects and porosity as well as the improvement of styrene selectivity.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Carbon nitride modified nanocarbon materials as efficient non-metallic
           catalysts for alkane dehydrogenation
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Lei Shi, Wei Qi, Wei Liu, Pengqiang Yan, Fan Li, Jianmin Sun, Dangsheng Su
      Carbon nitride modified carbon nanotubes (CN-OCNT) was prepared through simple electrostatic-dispersion and carbonization process using melamine and oxidized CNTs (oCNTs) as precursors. The stable electrostatic interactions between melamine and oCNTs enable a homogeneous dispersion of the precursor melamine on oCNTs surface. Carbon nitride (CNx) layers formed in-situ and dispersed evenly on oCNTs surface after thermal treatment. The modification with CNx layers increased the surface area and basicity of nanocarbon materials. And the electron rich CNx layers effectively increased the nucleophilicity, and thus promoted the CH bond activation ability of nanocarbon catalysts. CNx modified nanocarbon exhibited an obviously higher intrinsic activity than unmodified ones.
      Graphical abstract image

      PubDate: 2017-12-13T08:24:14Z
       
  • Bifunctional gold catalysts: Relationship between preparation method and
           catalytic performance in tandem cellobiose valorization
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): K. Morawa Eblagon, M.F.R. Pereira, J.L. Figueiredo
      Au was supported on carbon xerogel (CX) using various techniques and tested in tandem oxidation of cellobiose to gluconic acid (combining hydrolysis and oxidation steps in one-pot) in order to establish the relationship between the physicochemical properties of these materials and their performance as bifunctional catalysts. Notably higher selectivity to gluconic acid was obtained by catalysts with larger Au particle size showing moderate TOF. The performance of Au/CX catalysts was also affected by changes in surface chemistry of CX, introduced during deposition of Au. A direct link between the catalyst modifications and the reaction pathway was established by applying a simple reaction model to compare the rate constants of the intermediate processes. The experimental and modelled results revealed that reduction with citric acid was the most suitable method of preparation of the bifunctional catalyst. This catalyst was almost inactive in conversion of glucose and gluconic acid to side products, resulting in a 4 times higher yield of the desired product as compared to its counterpart prepared by sol-immobilization method (SI). On the other hand, the presence of PVA stabilizer on the surface of the SI catalyst resulted in the preferential oxidation of alcohol over aldehyde group in glucose, leading to poor selectivity of the cascade process. The reaction kinetics was examined and the apparent activation energy of the one-pot oxidation of cellobiose to gluconic acid was determined.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Cooperative action of heteropolyacids and carbon supported Ru catalysts
           for the conversion of cellulose
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): María Almohalla, Inmaculada Rodríguez-Ramos, Lucília S. Ribeiro, José J.M. Órfão, Manuel Fernando R. Pereira, Antonio Guerrero-Ruiz
      Acid hydrolysis and hydrogenation/hydrogenolysis reactions can be combined for catalytic conversion of cellulose into renewable biorefinery feedstocks by using heterogeneous bifunctional catalysts. In the present study a cooperative effect of heteropolyacids (HPA) and Ru nanoparticles supported on two carbon materials is demonstrated. The process can be suitable for the one-pot tandem reaction, yielding the conversion of cellulose into alkanediols (mainly propylene glycol and ethylene glycol). From a mechanistic point of view the differences in the distribution of polyol products, obtained from the cellulose reaction over monometallic Ru catalysts or over bifunctional Ru-HPAs materials, seem to be strongly determined by the competitive reactions of the sucrose (glucose+fructose) intermediate. HPA not only promote, as solid acids, the efficient hydrolysis of cellulose to glucose, but also catalyze the selective cleavage of the CC bonds in glucose and fructose, leading to the formation of ethylene glycol and propylene glycol. These reactions are in competition with the sugar hydrogenation to the corresponding C6 polyols (e.g. sorbitol), which takes place on the single Ru surface sites. The strong dependence of the product distribution on both catalytic functions is clarified by the kinetic analysis of the three competitive reactions of glucose, including its hydrogenation, isomerization and CC bond cleavage. Finally, considering the applicability of this reaction, it should be raised that the ball-milling pretreatment of cellulose is compulsory. In fact, during this ball-milling the crystallinity and particle size of cellulose are reduced, which results in a much higher conversion of cellulose. Herein, mixed ball-milling of cellulose and solid catalysts together was presented, which remarkably accelerates the cellulose conversion into valuable products.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Gold catalyst recycling study in base-free glucose oxidation reaction
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): C. Megías-Sayago, L.F. Bobadilla, S. Ivanova, A. Penkova, M.A. Centeno, J.A. Odriozola
      This work is devoted to the study of viability of immobilized gold colloids on carbon as catalysts for the base-free glucose oxidation reaction with a special emphasis made on catalysts’ recycling, operational life and possible routes for deactivation/reactivation under batch conditions. The observed catalytic behavior is related to all possible manners of deactivation, like gold metal state changes (particle size agglomeration or leaching), support modifications or active sites blocking by intermediates. In an attempt to recover the initial catalytic activity, the samples are subjected to different treatments such as H2O and NaOH washings and calcination. The failure of the regeneration procedures to recover the initial activity and after detailed catalyst’ characterization allows us to find out the main cause of deactivation.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Aqueous-phase reforming of alcohols with three carbon atoms on
           carbon-supported Pt
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Lidia I. Godina, Anton V. Tokarev, Irina L. Simakova, Päivi Mäki-Arvela, Ewelina Kortesmäki, Jan Gläsel, Leif Kronberg, Bastian Etzold, Dmitry Yu. Murzin
      Aqueous-phase reforming of propanol-1, propane-1,2-diol and glycerol was performed at 498K and 29.7bar in a continuous reactor with platinum supported on a polymer-derived carbon, as a catalyst. The number of hydroxyl groups of the reactant influenced the product distribution. An unexpectedly long stabilization period − more than 150h of time-on-stream − was found to be an important feature of the catalyst.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Metal-organic framework-derived carbons: Preparation from ZIF-8 and
           application in the adsorptive removal of sulfamethoxazole from water
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Imteaz Ahmed, Biswa Nath Bhadra, Hye Jin Lee, Sung Hwa Jhung
      In this study, we prepared highly porous carbonaceous materials from a metal-organic framework (MOF), ZIF-8, by pyrolysis. Pyrolysis temperature had a significant effect on the porosity of MOF-derived carbons (MDCs); the MDCs obtained at 1000°C (MDC-1000) exhibited the highest surface area and pore volume. The MDC-1000 showed almost twice the porosity of the original ZIF-8 used to prepare it. The obtained MDC was applied to the adsorptive removal of a pharmaceutical product [sulfamethoxazole (SMX)] from water, and the adsorption amount on MDC was 20 times higher than that on the original ZIF-8. Moreover, a very high adsorption for SMX was exhibited by the prepared MDC, in fact, the best ever reported for any adsorbent. Plausible adsorption mechanisms, such as H-bonding, could be suggested based on the effect of the solution pH on the status and adsorbed quantity of SMX and the zeta potential of MDC. Moreover, MDC-1000 and SMX acted as the H-donor and H-acceptor, respectively, in the mechanism (H-bonding) for adsorption. MDC can be a potential adsorbent for the removal of SMX because of its high adsorption capacity and ready recyclability.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Adsorption of dye with carbon media supported on polyurethane open cell
           foam
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Louis Lefebvre, Géraldine Agusti, Alissa Bouzeggane, David Edouard
      The use of a combined polydopamine polyurethane open cell foam (OCPUF@PDA − recently introduced in open literature) with carbon media, is for the first time used for the dye (methylene blue) adsorption in an aqueous solution. The carbon media used in this work is activated charcoal and/or carbon nanotubes that are supported on the foam’s surface. These new tools obtained (OCPUF@PDA@AC and OCPUF@PDA@CNT) are evaluated and compared to OCPUF@PDA and to the non-supported carbon media. The adsorption efficiency (245mgMB/gcarbon for OCPUF@PDA@AC versus 10mgMB/gPDA for OCPUF@PDA) and easy-to-use of these new tools, open real perspective in wastewater treatment.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Effect of surface, structural and textural properties of graphenic
           materials over cooperative and synergetic adsorptions of two
           chloroaromatic compounds from aqueous solution
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): A. Esteban-Arranz, D. Compte-Tordesillas, V. Muñoz-Andrés, M. Pérez-Cadenas, A. Guerrero-Ruiz
      Graphenic materials have been recently applied for adsorption processes due to their high efficiency and their easy capability of surface modification. In the present study two different graphene oxides, two reduced graphene oxides under inert atmosphere and one reduced graphene oxide under ammonia atmosphere were used as adsorbents for removing two chloroaromatic compounds from water: 2,4-dichlorophenol and 2,4-dichlorophenoxyacetic acid. Hydrogen bonds and ππ interactions have been detected by Attenuated Total Reflectance infrared spectroscopy in the solids with adsorbed species. Besides, two direct relationships between their adsorption capacities and graphenic surface, textural and structural properties were found. In order to obtain real adsorption information, some experiments with the presence of both pollutants at the same time were performed. From these mixture experiments, when graphene oxide was used as adsorbent some cooperative effects between pollutants were detected. Based on XRD results and an innovative comparison between different infrared techniques, the importance of interlayer spaces during adsorption was demonstrated. Otherwise, synergetic interactions between pollutants were revealed as the main adsorption forces when reduced graphene oxides were used, being their aromatic structures a decisive factor in their final adsorption capacity.
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      PubDate: 2017-12-13T08:24:14Z
       
  • CO2 adsorption over modified AC samples: A new methodology for determining
           selectivity
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Burcu Acar, Melek Selcen Başar, B. Merve Eropak, Burcu Selen Caglayan, A. Erhan Aksoylu
      Activated carbon (AC) based adsorbents having high and stable CO2 adsorption capacity with enhanced CO2 selectivity in presence of CH4 were developed. Alkali modified AC samples were prepared, their CO2 adsorption capacities were measured, a new methodology for selective adsorption capacity determination under multicomponent gas mixture flow was developed, and the results were analyzed to determine the preparation procedure yielding optimum adsorbent design. Two groups of adsorbents were prepared by K2CO3 impregnation on air and HNO3 oxidized forms of a commercial AC followed by calcination at various temperatures. The resulting adsorbents were named according to calcination temperatures as ACxK-calT. The highest CO2 adsorption capacity was measured on AC3K-300 sample as 110mg/g adsorbent at 1000mbar CO2 and 25°C. CO2 adsorption was confirmed reversible, whereas CH4 adsorption was found partially irreversible. The highest mass based CO2:CH4 selectivity, ca. 3.7, was achieved over AC2K-200 at 25°C for the 50%CO2-50%CH4 mixture. AC2K-200 was further tested at higher total pressures, for 0–5000mbar pressure range, at 25°C. CO2 adsorption capacity was measured as 197mg/g adsorbent at 5000mbar CO2. Among Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models, D-R was found to be the most successful one explaining CO2 adsorption behavior of AC samples.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Influence of the nitrogen-doped carbon nanofibers on the catalytic
           properties of supported metal and oxide nanoparticles
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Olga Yu. Podyacheva, Alexander S. Lisitsyn, Lidiya S. Kibis, Andrei I. Stadnichenko, Andrei I. Boronin, Elena M. Slavinskaya, Olga A. Stonkus, Svetlana A. Yashnik, Zinfer R. Ismagilov
      Catalysts containing platinum (1 and 10wt.%) or cobalt oxide (10, 50 and 90wt.%) and nitrogen doped carbon nanofibers (N-СNFs) were synthesized. X-ray photoelectron spectroscopy, CO chemisorption and temperature-programmed reduction methods were used to reveal that pyridine-like nitrogen of N-СNFs is involved in the anchoring of metal or oxide particles on the carbon surface and determines their size, electronic state and redox ability, thus changing the catalytic performance of the catalysts in the oxidation of carbon monoxide. Various models of particle stabilization on the surface of N-CNFs were proposed: (1) stabilization of nanoparticles with the retention of their metallic state by the pyridine-like site; (2) stabilization of electron deficient nanoparticles by a pair of pyridine-like nitrogen sites and (3) stabilization of electron deficient nanoparticles by the pyridine-like site near the carbon vacancy.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Immobilization of carbon nanofibers (CNFs) on a stainless steel filter as
           a catalyst support layer
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): J.M. Roemers-van Beek, J.G. van Ommen, L. Lefferts
      A layer of carbon nanofiber (CNF) agglomerates is used to produce a catalyst support layer that can be immobilized on a stainless steel filter and that can be removed when desired. For immobilization a filtration procedure is developed that produces a stable CNF layer at relatively low shear force flows (<0.18m/s). Under these conditions the device can be used as a chemical reactor. Increasing the shear force flow rate enables removal of the CNF layer. The interaction between the CNF agglomerates within the immobilized layer is stronger than the attachment of the entire layer to the surface of the stainless steel filter. The weaker interaction between the layer of CNF agglomerates and the filter surface therefore determines the stability of the layer. High surface roughness of the filter on micro-scale as well as deep penetration of CNF agglomerates in the pore mouths of the stainless steel filter both enhance stability of the CNF layer.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Promoter effect of alkalis on CuO/CeO2/carbon nanotubes systems for the
           PROx reaction
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): A.B. Dongil, B. Bachiller-Baeza, E. Castillejos, N. Escalona, A. Guerrero-Ruiz, I. Rodríguez-Ramos
      The effect of alkali promotion (Li, Na, K and Cs) on the CO preferential oxidation (CO PROX) reaction has been studied over Cu-CeO2 catalyst supported on carbon nanotubes (CNT). The catalysts were prepared with 2.5wt.% Cu and 20wt.% CeO2 loadings, and alkali/Cu atomic ratios of 0.68. The catalytic performance and the characterization by powder X-ray diffraction (XRD), TEM-STEM, H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) has been presented. TEM and XRD analyses showed that the addition of alkali reduces the size of ceria crystallites. It was found that in general the incorporation of alkali favored the conversion of CO at low temperatures, being more pronounced for the K-doped catalyst. The characterization showed that the addition of K favored the Cu-CeO2 interaction, the activity of the catalyst was enhanced and the opposite was observed for Cs-doped sample. The characterization results reveal that the observed increase in the Cu+ species proportion and in lattice oxygen are related to the better catalytic performance.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Comparative study of 1,2-dichlorethane decomposition over Ni-based
           catalysts with formation of filamentous carbon
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Yurii I. Bauman, Ilya V. Mishakov, Denis V. Korneev, Yury V. Shubin, Aleksey A. Vedyagin, Roman A. Buyanov
      Catalytic chemical vapor deposition of 1,2-dichlorethane over Ni-based catalysts into carbon nanostructured materials was studied. The catalysts were prepared by mechanochemical activation and by metal dusting of bulk nickel-containing alloy precursors. Model Ni-M alloys, where M is Co, Cu, and Fe, were obtained by coprecipitation technique. Loading of M in the samples was varied in a range of 1–5at.%. Pure nickel was used a reference. The kinetics of carbon deposition was investigated using flow reactor equipped with McBain balances. The samples of carbon product were characterized by nitrogen adsorption, scanning and transmission electron microscopies. The hydrogen addition into reaction mixture was shown to have opposite effect on both catalytic behavior and carbon yield depending on catalyst’s nature. Segmented structure of carbon filaments formed specifies its developed surface area. Both bulk chlorination of nickel particles and its blockage by dense carbon deposits in the case of mechanochemically prepared samples were suggested to be responsible for rapid deactivation of the catalyst.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Water-soluble single source precursors for homo- and hetero-metallic
           nanoparticle catalysts supported on nanocarbons
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Nathalie Mager, Pierre Libioulle, Samuel Carlier, Sophie Hermans
      Homo- and hetero-metallic catalysts were prepared in water from a single metal source and in a single step, and were tested in cinnamaldehyde selective hydrogenation. Two new water-soluble clusters, namely [Ru5C(CO)14(TPPTS)1] and [Ru5PtC(CO)15(TPPTS)1], were synthesized by the addition of phosphine TPPTS to starting homo- and hetero-metallic clusters soluble in organic solvents. They were then impregnated onto nanocarbons (CNF and CNT) in water at different pH values. Cluster deposition occurred via two adsorption modes and was the most successful when attractive electrostatic interactions took place. Thermal activation of these samples led to heterogeneous catalysts with a small mean particle size between 2 and 4nm. The home-made catalysts showed increased conversions and selectivities (up to 73%) towards the thermodynamically unfavored product cinnamyl alcohol compared to a commercial catalyst. The selectivity was in general higher with CNF support, with less oxygenated function and with bigger particles. The selectivity increased slightly with the addition of platinum to ruthenium but the activity was enhanced tremendously (up to 57% at t=30min).
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      PubDate: 2017-12-13T08:24:14Z
       
  • New doping process mode to synthesize in situ N-MWNTs in novel coaxial
           nanostructure
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): O. Guellati, F. Antoni, M. Guerioune, D. Bégin
      Nitrogen-doped MWNT “N-MWNT” have gained an increasing interest because particularly of their electronic properties allowing their use in specific applications such as catalysis, sensors, nano-electronics and energy storage. In this investigation, novel coaxial structures consisting of concentric shells of pure carbon MWNT cores with external nitrogen-doped carbon walls (N-MWNT) were produced using a catalytic CVD process, with ethane and ammonia as carbon and nitrogen sources over Fe–Al2O3 support. In order to optimize the growth conditions of such N-MWNT nanostructures, we investigate the influence of different key parameters, i.e., ammonia injection moment in two doping process modes “Instantaneously doping and Mid-doping”, growth temperature (750 and 850°C) and the presence of H2 as reducer gas in the reaction environment. A strong correlation between ammonia injection duration (60, 90 and 120min) and nitrogen content (from 0.4at.% to 2.2at.%) incorporated in the nanotube products was observed and different coordination between C and/or O atoms have been described by XPS. These functionalized MWNTs were characterized using HR-TEM, FESEM, XPS, BET, TG analyses and Raman spectroscopy in order to determine their structural characteristics (graphitization and crystallinity) in quantitative and qualitative ways.
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      PubDate: 2017-12-13T08:24:14Z
       
  • The impact of synthesis method of CNT supported CeZrO2 and Ni-CeZrO2 on
           catalytic activity in WGS reaction
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Agata Łamacz, Krzysztof Matus, Barbara Liszka, Joaquin Silvestre-Albero, Mama Lafjah, Thierry Dintzer, Izabela Janowska
      Carbon nanotube (CNT) supported catalysts containing ceria-zirconia mixed oxide (CeZrO2) and nickel were synthesized and tested in water gas shift (WGS) reaction. Physicochemical characterization including N2 adsorption, X-ray diffraction (XRD), scanning and transmission microscopy (SEM/TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and temperature programmed reduction with H2 (H2-TPR), as well as catalytic tests of WGS reaction showed that the synthesis method had significant impact on composition, morphology, structural properties and catalytic performance of obtained hybrid materials. The catalysts obtained by co-precipitation of metal oxides (NiO and/or CeZrO2) on CNT walls demonstrated better dispersion of active phase and smaller particle size than catalyst obtained by depositing of powder CeZrO2 or Ni-CeZrO2. Moreover, the catalyst obtained by co-precipitation revealed better performance in WGS reaction; however, some CH4 formation was noticed over Ni-CeZrO2/CNT system. The role of CeZrO2 in catalysts performance in WGS as well as the importance of good metal-oxide contact were confirmed.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Coexistence of sulfonic and pyridinic sites on H2SO4 treated N-doped
           carbon nanotubes
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Anas Benyounes, Fatiha Ouanji, Stéphane Louisia, Mahfoud Ziyad, Philippe Serp, Mohamed Kacimi
      Three types of purified nitrogen doped CNTs were tested for isopropyl alcohol conversion under nitrogen or air atmosphere, and compared to undoped CNTs. The N-doped CNTs differ from their nitrogen content, from the presence or not of undoped section in their structure, and from their sulfur content. The isopropyl alcohol conversion leads to the formation of acetone as the sole product on catalysts presenting no nitrogen or low nitrogen and sulfur content, pointing to the presence of basic sites. At higher nitrogen and sulfur content, N-doped catalysts lead to the formation of acetone and propene, highlighting the presence of both basic and acidic sites on such material. XPS characterizations allow us to propose that the basic sites consist in pyridinic surface groups, and the acidic sites in sulfonic surface groups formed during the purification of these materials with sulfuric acid.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Introducing sulphur surface groups in microporous carbons: A mechanistic
           study on carbide derived carbons
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Johannes Landwehr, Hendryk Steldinger, Bastian J.M. Etzold
      The mechanisms of introducing sulphur surface groups in porous carbons was deduced from the model carbon material carbide derived carbon (CDC) based on titanium carbide. The electrophilic substitution reaction at the aromatic ring system was identified as the predominant mechanism, even in highly amorphous carbons. The finding was deduced from TG–MS and XPS analysis. Upon varying the aromaticity and the amount of oxygen surface groups of the porous carbons, no change in mechanism was observed. This neglects an effect of spatial hindrance of the electrophilic substitution reaction within micropores. The introduced sulphur groups were found to be highly acidic sulphonic acid groups, which enable the functionalized carbons to be used as solid acid catalysts. The performance evaluation of the functionalized carbons catalyst in the esterification reaction of levulinic acid with ethanol supported the mechanistic findings. The activity correlated with the amount of sulphuric acid groups. The maximum amount of 0.86mmolm−2 and, thus, the highest activity was determined for the most graphitic porous carbon material.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Polydopamine films and particles with catalytic activity
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Vincent Ball
      Coatings obtained from the oxidation of catecholamines, most often dopamine, allow not only to coat the surface of all classes of known materials (metals, oxides, polymers, liquid/liquid and liquid/air interfaces) with a conformal and robust film but also to easily post-functionalize such coatings with metal nanoparticles and enzymes using the intrinsic redox and quinone functionalities of the coating. Hence polydopamine (PDA) based coatings offer huge perspectives for the immobilization of catalysts. This review provides a summary of the first successful research efforts in this domain and provides some first proofs of concept that PDA may act as a catalyst by itself for aldolations, formation of carbonates from CO2 and epoxides and for hydrolysis reactions without addition of further enzymes or metal nanoparticles.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Catalytic performance of ordered mesoporous carbons modified with
           lanthanides in dry methane reforming
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Joanna Goscianska, Robert Pietrzak, Juan Matos
      The catalytic activity of Ce- and La-based catalysts supported on mesoporous carbons was studied in dry methane reforming reaction (DMR). Mesoporous carbons were prepared by hard template method using ordered silica (SBA-15 and KIT-6) as templates and sucrose as carbon precursor. After sucrose pyrolysis samples were washed with 5wt% hydrofluoric acid at room temperature to remove the silica template. Catalysts and supports were characterized by small- and high-angle X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), acid-basic surface oxygen functional groups and N2 adsorption-desorption isotherms. Catalytic tests were performed at 1:1 molar ratio of methane and carbon dioxide at continuous flow in a bed-fix stainless-steel reactor under atmospheric pressure and 650°C. Catalysts were pretreated in situ under hydrogen flow from ambient to temperature of reaction. Preliminary results showed that Ce- and La-based catalysts supported on mesoporous carbons exhibit higher activity and a better stability in comparison of analogous catalysts supported on SBA-15 and KIT-16.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Influence of surfactants on the physicochemical properties and catalytic
           behaviour of Mo-doped carbon xerogels
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): F.J. Maldonado-Hódar, H. Jirglová, S. Morales-Torres, A.F. Pérez-Cadenas
      A series of Mo-doped carbon xerogels were obtained by surfactant-assisted sol-gel polymerization of resorcinol-formaldehyde at neutral pH. The morphology, porous texture, acid-base character and metal phase and dispersion, of these novel nanostructured materials were studied by several and complementary techniques, while their catalytic performance was assessed in the isopropanol decomposition and n-hexane aromatization. The formation of different carbon nanostructures (nanospheres or nanofibers) was induced by fitting the surfactant ratios, being always obtained highly dispersed molybdenum nanoparticles on these nanostructures. Nevertheless, the nature of the Mo-phases varied from oxides to carbides depending on surfactant ratios. The incorporation of cationic surfactant molecules to the chemical structure of the gels favours the interaction with anionic precursors, like MoO4 2−, which avoids sintering and promotes the carbidization of the metallic phase (63% of the total metal loading being achieved) during carbonization. The combination of Mo-phases (oxide and carbide) together the carbon support moderates the catalyst acidity, which induces a high selectivity to benzene (around 75%) in hexane aromatization processes.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Synthesis of Pd-Al/biomorphic carbon catalysts using cellulose as carbon
           precursor
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): F. Cazaña, A. Galetti, C. Meyer, V. Sebastián, M.A. Centeno, E. Romeo, A. Monzón
      This work presents the results obtained with novel Pd and Pd-Al catalysts supported on carbon, which have been prepared using a biomorphic mineralization technique. The catalyst synthesis procedure includes a stage of thermal decomposition under reductive atmosphere of cellulose previously impregnated with the metallic precursors. We have studied the influence of the temperature and time of decomposition, and of the Al precursor addition, on the textural and catalytic properties. The characterisation results indicate that the preparation method used leads to the formation of carbonaceous supports with a high microporosity (up to 97% micropore volume) and values of the BET surface up to 470m2/g while maintaining the original external structure. The use of low temperatures (ca. 600°C) during the decomposition step allows the preparation of highly dispersed catalysts with narrow Pd particle size distributions. However, the thermal decomposition at elevated temperatures (ca. 800°C) increases the Pd particle size due to the sintering of the metallic phase. This phenomenon is augmented with the decomposition time and is not affected by the presence of Al. Consequently, the catalytic activity of these materials in cyclohexene hydrogenation is strongly affected by the operational conditions used during the thermal decomposition step. Unexpectedly, the more sintered catalysts, i.e. those prepared at 800°C, show the highest activity. According to the characterization results, this fact can be explained considering that the smaller Pd particles obtained after preparation at e.g. 600°C are quite inactive because they are confined in the internal structure of the micropores of the support and/or embedded inside the carbon matrix. In contrast, after decomposition at 800°C, the larger Pd particles formed are placed at the external surface of the catalyst, being accessible to the reactants. In addition, for the specific conditions under which the Pd is accessible, the presence of Al favours the cyclohexene conversion due to the enhancement of the adsorption on the Pd surface as a consequence of a charge transfer phenomenon. These results can serve as a guideline for the preparation of these catalysts based on raw lignocellulosic materials in order to maximize their catalytic performance.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Carbons from second generation biomass as sustainable supports for
           catalytic systems
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Laura Prati, Davide Bergna, Alberto Villa, Paolo Spontoni, Claudia L. Bianchi, Tao Hu, Henrik Romar, Ulla Lassi
      In this study activated carbons were produced from the wood of three different wood species (pine, birch, spruce). The resulting activated carbons were characterized in bulk for ash content, carbon content (elemental analyses), specific surface area, and pore size distribution, and at the surface by measuring the autogenerated pH and studying their structure by XPS. All the samples presented high surface areas and appeared to be mesoporous materials (mesopores >80%). The carbons were then used as support for AuPt nanoparticles and tested in the liquid phase oxidation of glycerol (GLY) and in the hydrogenation of levulinic acid (LA), two important chemicals from cellulose-based biomass. The catalytic results showed that the catalyst activity depends on the structural features of carbons: in GLY oxidation the most active catalyst presents the lowest content of carboxylic acid (Birch derived carbon) whereas in LA hydrogenation an higher content of aliphatic structure seems to enhance the stability and therefore the activity of the catalyst (Spruce catalyst). The structure of the carbons does not affect greatly the selectivity of both selected model reactions.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Reaction and deactivation of propylene over SAPO-34 at low temperature
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Zhao Jia, Dali Cai, Yu Cui, Weizhong Qian, Fei Wei
      We report the low temperature conversion of propylene with SAPO-34 zeolite as the catalyst, as a branched route in process of methanol to propylene (MTP). The maximum conversion of propylene occurred at 300°C, corresponding to the activation of propylene over low temperature acid sites of zeolite. With rate constant calculation and coke analysis at low temperature, we confirmed that adamantane is easily produced from propylene and it does not contribute to the increased conversion of reactants, but results in the cage blockage of zeolite. By detailed coke analysis and product distribution analysis, we proposed cyclic olefins, not aromatics, played the important role in hydrocarbon pool. In this regard, low temperature shows negative effect on MTP process considering the quick conversion of propylene to other olefins and the formation of adamantane, ignore of the increased ratio of propylene to ethylene ratio. The result provided new insight on the reaction mechanism of MTO/MTP system.
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      PubDate: 2017-12-13T08:24:14Z
       
  • When the nature of surface functionalities on modified carbon dominates
           the dispersion of palladium hydrogenation catalysts
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): E. Castillejos, A.M. García-Minguillán, B. Bachiller-Baeza, I. Rodríguez-Ramos, A. Guerrero-Ruiz
      Commercial carbon nanofibers with different graphitic structure and commercial multiwall carbon nanotubes (CNT) were chemically modified in order to introduce specific alkyl ligands on their surface. Palladium catalysts have been prepared using these modified supports and subsequently tested in the partial hydrogenation of 1,3-butadiene under conditions of excess hydrogen. Herein, we used thermogravimetry (TG), temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and nitrogen adsorption at 77K techniques in order to characterize both supports and catalysts. We focus on testing the effects of support surface functionalities either on morphology of supported palladium (Pd) nanoparticles (NPs) or on their catalytic performances. High selectivity to butenes was obtained with the catalysts prepared over supports containing alkyl chains, while over-hydrogenation to butane took place over oxygen-containing functional groups. Nicely the catalysts with modified supports minimize the secondary hydrogenation of butenes even at high conversions. Therefore, Pd NPs on modified nano-carbon catalysts may open up more opportunities to optimize the activity and the selectivity for partial hydrogenation reactions.
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      PubDate: 2017-12-13T08:24:14Z
       
  • The effect of preparation conditions of Pd/C catalyst on its activity and
           selectivity in the aqueous-phase hydrogenation of 2,4,6-trinitrobenzoic
           acid
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Olga B. Belskaya, Roman M. Mironenko, Valentin P. Talsi, Vladimir A. Rodionov, Tatyana I. Gulyaeva, Sergey V. Sysolyatin, Vladimir A. Likholobov
      The effect of the nature of alkaline agent and pH value of hydrolysis of Pd(II) chloride complex into palladium polynuclear hydroxo complexes, as precursor of active component in Pd/C catalyst, on the dispersion of palladium particles supported on carbon material Sibunit was revealed. It was shown that an increase in the particle size of supported palladium enhances the specific catalytic activity in hydrogenation of 2,4,6-trinitrobenzoic acid and changes the direction of the transformation (increases the fraction of non-aromatic intermediate, cyclohexane-1,3,5-trione trioxime, in the products). The results obtained are essential for optimizing the particle size of supported palladium in selective hydrogenation of polyfunctional organic compounds.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Selective and efficient dimerization of isobutene over H3PO4/activated
           carbon catalysts
    • Abstract: Publication date: 1 March 2018
      Source:Catalysis Today, Volume 301
      Author(s): Anna Malaika, Paulina Rechnia-Gorący, Monika Kot, Mieczysław Kozłowski
      Dimerization of isobutene to branched C8 olefins (precursors of high octane gasoline additives) was performed over eco-friendly activated carbon catalysts impregnated with phosphoric acid, under continuous gas phase operating conditions. A series of catalysts differing in phosphoric acid loading were prepared by incipient wetness impregnation and tested in the reaction carried out at various temperatures (100–260°C), with the use of an isobutene/isobutane mixture at a molar ratio of 4:1 as a feedstock. The conversion and selectivity patterns obtained for a selected sample evolved visibly with the reaction temperature and the best results were obtained at 180°C. The effect of phosphoric acid loading on the catalytic activity of the samples at this temperature was investigated and discussed. For the sake of comparison also other acidic activated carbons and the commercially available catalyst Amberlyst 15 were tested. The high H3PO4-loaded materials exhibited excellent catalytic performance in the process (high isobutene conversion, good selectivity to C8 products and high catalyst stability) which was assigned to a combination of acidic and textural properties of the materials obtained.
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      PubDate: 2017-12-13T08:24:14Z
       
  • IFC - Editors; Editorial Board &amp; scope
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300


      PubDate: 2017-12-13T08:24:14Z
       
  • Contents list
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300


      PubDate: 2017-12-13T08:24:14Z
       
  • Improved photocatalytic ozone abatement over transition metal-grafted
           titanium dioxide
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Julia Patzsch, Jonathan Z. Bloh
      Photocatalysis can be an effective means to combat air pollution. Up to now, mainly direct NOx abatement has been studied, but ozone abatement could also contribute significantly to improved air quality. The ozone decomposition rates of different commercial titanium dioxide based photocatalysts grafted with copper, manganese or iron ions were studied both under UVA illumination and under dark conditions. Copper and manganese grafting were effective in significantly increasing the ozone decomposition rate of the photocatalysts. The procedure worked best when using low surface area pigmentary anatase rather than nanoparticulate photocatalysts. Manganese grafting also increased the ozone abatement under dark conditions, likely due to small MnOx clusters acting as catalysts. Iron grafting appears to be the most universal method of improving the photocatalytic ozone removal rate, as it worked for all four different photocatalysts studied. Extremely low iron grafting ratios of 0.002at.% were sufficient to dramatically improve the performance.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Anatase and rutile in evonik aeroxide P25: Heterojunctioned or individual
           nanoparticles'
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Xiongzhen Jiang, Maykel Manawan, Ting Feng, Ruifeng Qian, Ting Zhao, Guanda Zhou, Fantai Kong, Qing Wang, Songyuan Dai, Jia Hong Pan
      Evonik Aeroxide P25 (formerly Degussa P25) is a flame-made multiphasic TiO2 nanoparticles containing anatase and rutile, as well as a small amount of amorphous TiO2. The past decades have witnessed the wide applications of P25 as a benchmark material for studying photocatalytic mechanism, materials and process. However, controversy remains regarding the microstructure of anatase and rutile: do they interwoven forming heterojunction structure or exist individually? To clarify it, we selected a medium alkaline, LiOH to erode bare P25 under a mild hydrothermal condition. Since rutile presents much higher resistances towards dissolution by LiOH than anatase, it is reasonable to find during hydrothermal reaction that the ratio of anatase to rutile (A/R) gradually decrease if they exist individually. Reversely, the A/R value gradually increases at the beginning of the hydrothermal reaction, implying that rutile shows high activity towards dissolution and phase transformation to lithium titanate. As calculated, around 15% rutile nanoparticles more likely exist on the surface of anatase with the formation of a heterojunction structure, although isolated nanoparticles with sole rutile phase coexist. In addition to XRD analysis, TEM measurement shows that the Moiré fringes frequently present, which further manifests that some anatase particles are covered with rutile clusters or thin overlayers.
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      PubDate: 2017-12-13T08:24:14Z
       
  • The influence of low irradiance and electrolytes on the mineralization
           efficiency of organic pollutants using the Vis-active photocatalytic
           tandem CuInS2/TiO2/SnO2
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Anca Duta, Luminita Andronic, Alexandru Enesca
      Many photocatalyitc laboratory experiments are developed at low (and different) irradiance values, making the results difficult to benchmark. This study analyzes the influence of the low irradiance, photon flux and the UV share on the photodegradation kinetics and efficiency of methylene blue (MB) using a hetero-structured thin film photocatalyst. The results show that the photon flux influences the process kinetic after an induction period and it was found that increasing irradiance has positive effect on the photo-catalytic efficiency, if UV does not exceed 25%, when photo-corrosion becomes significant. In the experimental conditions, the efficiency is also moderately influenced by the photon flux vales. Electrolytes are usually part of industrial or residential wastewaters, with multiple consequences among which accelerated photo-corrosion but also increased local charge transfer (thus decreased recombination) on the photocatalytic surface. The addition of two common electrolytes that are not hydrolysing (NaCl and CaCl2) into the dye solution was correlated with the chemical stability of the CIS/TiO2/SnO2 hetero-structure and the removal/mineralization efficiencies. The highest photodegradation efficiency (99%) was reached when 3.5% NaCl was used. The photocorossion increase up to 24.03% after 24h when the photocatalyst is immersed in 3.5% NaCl electrolyte at 23W/m2 UV/vis irradiance and 120μmol/(m2 s) photon flux.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Novel synthesis approaches for WO3‐TiO2/MWCNT composite photocatalysts-
           problematic issues of photoactivity enhancement factors
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Enikő Bárdos, Gábor Kovács, Tamás Gyulavári, Krisztián Németh, Egon Kecsenovity, Péter Berki, Lucian Baia, Zsolt Pap, Klára Hernádi
      The “build-up” methodology, the importance of the order of the semiconductor layers in WO3‐TiO2/MWCNT composite materials was studied in terms of the applied synthesis pathway, morpho-structural parameters (mean crystallite size, crystal phase composition, morphology) and photocatalytic efficiency (using oxalic acid as model pollutant). The appearance of TiWOx phase in the composites contributed to the enhancement of the photocatalytic efficiencies, as different synthesis approaches led to different crystal phase compositions. Although, it was proven that a beneficial phase’s presence can be hindered if an excess of MWCNT or WO3 was applied. As the ratio of the mentioned materials was reduced, active composites were obtained, but the previously noticed TiWOx disappeared. Therefore, it was proven, that in the case of WO3-TiO2/MWCNT nanocomposite system several photocatalytic activity enhancement factors can be introduced, but not simultaneously (the disappearance of TiWOx at low MWCNT and WO3 contents and the appearance of highly crystalline anatase).
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      PubDate: 2017-12-13T08:24:14Z
       
  • TiO2-MgO mixed oxide nanomaterials for solar energy conversion
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Balaranjan Selvaratnam, Ranjit T. Koodali
      Mixed oxide materials have been intensely investigated in catalysis. In recent years, photoactive species have been deposited on high surface area supports and investigated for a variety of applications that include Dye Sensitized Solar Cells (DSSC), photocatalytic and photoelectrochemical splitting of water, and photocatalytic degradation of organics. Basic materials like MgO are attractive as supports for the above mentioned applications, since they can be synthesized conveniently with relatively large surface areas and porosities. The wide band gap (>7eV) and hence the insulating nature of MgO also lends itself to interesting uses in several applications involving solar energy conversion. The presence of low amounts of MgO has been found to be beneficial for DSSC, photo-electrochemical splitting of water, and photocatalytic degradation of dye molecules and will be discussed in-depth in this review.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Synthesis of ultrasound assisted nanostuctured photocatalyst (NiO
           supported over CeO2) and its application for photocatalytic as well as
           sonocatalytic dye degradation
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Sonam V. Sancheti, Chetana Saini, Rohini Ambati, Parag R. Gogate
      The present work focuses on the improved synthesis of bimetallic catalyst, NiO impregnated CeO2, based on the use of ultrasound assisted approach with comparison with the conventional approach. Morphological characteristics of the catalyst have been established using TEM and BET analysis. In addition XRD and FTIR analysis was also performed to establish the crystallite size and the active functional groups that decide the catalytic activity respectively. It has been established that the catalyst synthesized in the presence of ultrasound showed better catalytic properties than the catalyst obtained using the conventional approach with the specific surface area increasing from 31.41m2/g to 94.63m2/g due to cavitational effects. TEM analysis also established the appearance of sharp edged and non-agglomerated nanoparticles in the ultrasound assisted synthesis whereas in the case of conventional approach, agglomerates and higher particle/crystallite size was observed. The catalyst was subsequently used for the catalytic degradation of Brilliant Green dye using UV irradiation and ultrasonic irradiation. The catalytic activity of the catalyst obtained using ultrasound assisted approach was observed to be better than the catalyst obtained using conventional approach. UV induced extent of degradation using the catalyst synthesized in the presence of ultrasound was found to be 82% whereas using conventionally synthesized catalyst, much lower extent of degradation as 40% was obtained. TOC analysis was also performed which confirmed correspondence with the extent of degradation and better results for the ultrasonically obtained catalyst. Overall the ultrasound assisted approach has been demonstrated to be an effective approach for obtaining better quality NiO impregnated CeO2 catalyst with proven efficacy for decolourization using photocatalysis (higher activity) as well as sonocatalysis.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Interparticle double charge transfer mechanism of heterojunction
           α-Fe2O3/Cu2O mixed oxide catalysts and its visible light photocatalytic
           activity
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Sandeep Kumar Lakhera, Aakash Watts, Hafeez Yusuf Hafeez, Bernaurdshaw Neppolian
      α-Fe2O3/Cu2O mixed oxide photocatalysts were prepared by one step facile hydrothermal method. During the synthesis, the growth of phase pure and highly crystalline polyhedral Cu2O crystals occurred and simultaneously a heterojunction formed between α-Fe2O3 and Cu2O particles. The optical band gap of bare Cu2O was found to be 1.8eV which was less than the reported values and incorporation of 5wt% α-Fe2O3 further reduced the band gap of Cu2O to 1.75eV, indicating an enhanced absorption of visible light by the binary photocatalysts. More importantly, the loading of α-Fe2O3 on Cu2O augmented the charge carriers separation and transfer at the interface, which was evident by the reduced photoluminescence intensity of α-Fe2O3/Cu2O photocatalysts. The influence of different loading amounts of iron oxide (1–10wt%) on Cu2O was evaluated. Among them, 5wt% α-Fe2O3 loaded Cu2O showed the enhanced photodegradation activity due to the formation of an effective p-n heterojunction and exhibited nearly 30% and 95% increase in the photodegradation rate of methyl orange (MO) compare to bare Cu2O and α-Fe2O3, respectively. The photo generated superoxide radicals were found to be the main reactive species responsible for the degradation of MO. The excellent photodegradation activity of α-Fe2O3/Cu2O photocatalyst is mainly attributed to the enhanced visible light absorption, efficient charge carriers separation and transfer. Based on the experimental results, a double charge transfer mechanism was proposed for the separation and transfer of photogenerated charge carriers in the photocatalysts.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Ag and CuO impregnated on Fe doped ZnO for bacterial inactivation under
           visible light
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Rimzhim Gupta, Neerugatti KrishnaRao Eswar, Jayant M. Modak, Giridhar Madras
      Interfacial coupling of semiconductor with metal has been demonstrated for inactivation of E. coli. Fe doped ZnO was synthesized by sol–gel method that resulted in enhanced absorbance in visible region. Various concentrations of Cu were impregnated on Fe doped ZnO that eventually turned into copper oxide and the photocatalytic activity of this material was compared with noble metal (Ag) impregnated on Fe doped ZnO. The obtained materials were characterized by various techniques. The crystal structures were determined by XRD and XPS was used to identify the oxidation states of the elements present in the photocatalyst. The morphologies and microstructures were determined by SEM. The optical absorbance of the photocatalysts was characterized by diffused reflectance spectra. Photocatalytic experiments were conducted for inactivation of E. coli using various catalysts. The rate constants obtained for 3wt.% Cu impregnated Fe doped ZnO was higher than 1wt.% Ag impregnated Fe doped ZnO. The higher photoactivity of these materials compared to pristine ZnO can be attributed to decreased recombination of the excitons in the synthesized photocatalysts that was validated by photoluminescence. This study indicates the possible employment of copper as a viable substitute for silver for anti-bacterial applications.
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      PubDate: 2017-12-13T08:24:14Z
       
  • Insights into the photoactivity of iron modified bismuth titanate (Fe_BTO)
           nanoparticles
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Vijay Khanal, William Ragsdale, Satyajit Gupta, Vaidyanathan Ravi Subramanian
      The photoactivity of a bandgap engineered composite oxide nanostructure − BECON − comprising of Bi, Ti, and O as the building blocks and Fe as an earth-abundant additive (Fe-BTO) has been examined in the presence of UV–vis illumination of water-methanol system. The performance of the Fe-BTO was investigated by examining the effects of Fe-BTO loading, light intensity, methanol concentration, and Fe-BTO stability upon repeated use. Among the parameters evaluated, the photoactivity using 150mg of catalyst was determined most effective with a methanol concentration of 20M. In additional insights, all of the time resolved experiments indicated the existence of a methanol concentration dependent 2-zone activity region: zone 1- slow photoactivity and zone 2- accelerated photoactivity. The presence of the 2-zone region is attributed to the intermediates formed during the methanol oxidation. The formation of the intermediate formic acid, which is thermodynamically favored, is identified as one of the key stages in the reaction. Further, repeated use of the Fe-BTO leads to over a 70% loss in the photoactivity. This may be attributed to (i) the formation of surface-functional groups and/or (ii) intrinsic change in the Fe-BTO upon irradiation.
      Graphical abstract image

      PubDate: 2017-12-13T08:24:14Z
       
  • A green approach for degradation of organic pollutants using rare earth
           metal doped bismuth oxide
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): Waseem Raza, D. Bahnemann, M. Muneer
      Much effort has done for the development of novel semiconductor photocatalyst with enhanced visible light photocatalytic activity. Bismuth based oxide have attracted significant attention in the field of photocatalysis due to its narrow band gap hence, harvest more visible light. Therefore, a strategy for the design of efficient heterogeneous semiconductor photocatalyst is propose. In this connection, we have synthesized the modified bismuth trioxide using sol gel method with excellent photocatalytic activity for degradation of three different organic dyes. The fabricated samples were characterized by using standard analytical techniques, such as XRD, SEM, TEM, BET, PL and UV–vis/DRS spectroscopy. All doped-Bi2O3 photocatalysts exhibit higher photodegradation of dyes as compared to pure Bi2O3 under visible light illumination, while the highest efficiency was found at 3.0% La doped Bi2O3 and 1.2gL−1 dose. The enhanced photocatalytic activity of modified Bi2O3 photocatalyst can be ascribed predominantly due to their improved visible light absorption property and efficient charge separation. The photodegradation of dyes follow pseudo first-order kinetic in the presence of synthesized materials. Furthermore, the fabricated rod can be reused with little loss in photocatalytic efficiency. The results of scavengers study suggest that holes, hydroxyl and superoxide radicals play a significant role for photodegradation of dyes. The modified bismuth based oxide approach will open new avenues for the development of efficient photocatalyst for environmental remediation and energy conversion.
      Graphical abstract image

      PubDate: 2017-12-13T08:24:14Z
       
  • Mechanism of formation, structural characteristics and photocatalytic
           activities of hierarchical-structured bismuth-tungstate particles
    • Abstract: Publication date: 1 February 2018
      Source:Catalysis Today, Volume 300
      Author(s): H. Hori, M. Takase, M. Takashima, F. Amano, T. Shibayama, B. Ohtani
      The mechanism of the formation of flake ball-shaped (FB) bismuth-tungstate (BWO) particles was studied with samples prepared by hydrothermal reactions under standard conditions (tungsten/bismuth ratio of 0.55 in feed; 433K; 20h) and other modified conditions, and the structural characteristics of the samples were analyzed by powder X-ray diffraction (composition and crystal structure), field emission-type scanning electron microscopy (FE-SEM) (morphology), focused ion-beam etching followed by FE-SEM (inner void structure), ultrahigh-voltage transmission electron microscopy (inner void structure) and low-voltage scanning electron microscopy with energy-dispersive X-ray spectroscopic analysis (morphology and elemental distribution). Based on the results, a novel two-step mechanism of (1) formation of aqueous bismuth-oxyhydroxide droplets covered by tungstic acid (BOx@HWO) with fluidity and (2) reaction of inner bismuth and outer tungsten components at the BOx@HWO surface to yield BWO flakes is proposed as a one of the most plausible pathways that are consistent with the hollow structure of FB BWO and observations of the products prepared with shorter hydrothermal reaction. Photocatalytic activities of FB BWO samples in relation to their structure were studied.
      Graphical abstract image

      PubDate: 2017-12-13T08:24:14Z
       
 
 
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