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Journal Cover Catalysis Today
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0920-5861
     Published by Elsevier Homepage  [2575 journals]   [SJR: 1.283]   [H-I: 129]
  • Synthesis of C2+ hydrocarbons by CO2 hydrogenation over the composite
           catalyst of Cu–Zn–Al oxide and HB zeolite using two-stage
           reactor system under low pressure
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Masahiro Fujiwara , Hiroaki Sakurai , Kumi Shiokawa , Yasuo Iizuka
      The combination of methanol synthesis and methanol-to-gasoline (MTG) reaction is a beneficial process to produce particular C2+ hydrocarbons from CO2 and H2, because MTG reaction can produce C2+ hydrocarbons selectively without the formation of methane. However, the composite catalysts consisting of methanol synthesis catalyst and zeolite previously reported have produced C2+ hydrocarbons in poor yields especially under low pressure conditions. This paper reports the high yield production of C2+ hydrocarbons by CO2 hydrogenation using a two-stage reaction system consisting of a Cu–Zn–Al oxide catalyst in the first reactor and a composite catalyst of the Cu–Zn–Al oxide and HB (zeolite beta) in the second reactor. The key points of this system are reversed water-gas-shift (RWGS) reaction in the first reactor and the following H2O removal before the second reactor. The gas mixture supplied to the second reactor containing much amount of CO and little H2O enhanced the methanol synthesis and suppressed the methanol decomposition to CO over the Cu–Zn–Al oxide catalyst in the composite catalyst, promoting the MTG reaction to produce C2+ hydrocarbons over HB zeolite. The highest yield of C2+ hydrocarbons reached to approximately 15C-mol% under 0.98MPa.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Enhanced catalytic performance in dehydration of sorbitol to isosorbide
           over a superhydrophobic mesoporous acid catalyst
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Jian Zhang , Liang Wang , Fujian Liu , Xiangju Meng , Jianxin Mao , Feng-Shou Xiao
      A superhydrophobic mesoporous polymer-based acid catalyst (P-SO3H) was synthesized from solvothermal co-polymerization. The N2 sorption isotherms indicate the rich porosity of P-SO3H, confirmed by the TEM image. The IR spectra indicate the presence of sulfonic acid groups. Interestingly, P-SO3H gives contact angle of water droplet on the sample surface at 154°, suggesting its superhydrophobicity. More importantly, P-SO3H is highly efficient catalyst for dehydration of sorbitol to isosorbide, giving sorbitol conversion higher than 99.0% and isosorbide yield at 87.9%. In addition, P-SO3H exhibits excellent recyclability. After recycles for 5 times, the isosorbide yield is still 77.7%. In contrast, conventional acid catalyst of Amberlyst-15 shows the yield at only 15.4% after recycles for 3 times. The unique catalytic properties are reasonably related to the superhydrophobicity and porosity of P-SO3H. The sample large porosity offers a high degree of the exposed acidic sites to the reactants, and the sample superhydrophobicity would keep the water formed in the dehydration away from the catalyst, promoting the reaction equilibrium. As a result, the catalytic performance in dehydration of sorbitol to isosorbide over the superhydrophobic P-SO3H catalyst is significantly enhanced, compared with conventional acid catalyst of Amberlyst-15.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Contents list
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B




      PubDate: 2014-12-09T08:34:52Z
       
  • In memory of Professor Yasutake Teraoka
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Hong He



      PubDate: 2014-12-09T08:34:52Z
       
  • Selective catalytic conversion of bio-ethanol to propene: A review of
           catalysts and reaction pathways
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Masakazu Iwamoto
      The conversion of ethanol to propene were examined on Ni ion-loaded silica MCM-41(Ni-M41), Sc-modified In2O3 (Sc/In2O3), and a solid solution of Y2O3-CeO2. The propene production activity was in the order, Sc/In2O3 >Y2O3-CeO2 >Ni-M41, while their stability during the reaction was Y2O3-CeO2 ∼Sc/In2O3 >Ni-M41. The propene yield and durability of Sc/In2O3 were greatly improved by addition of water and hydrogen in the reactant stream. The reaction mechanism was greatly dependent on the catalyst employed. On Ni-M41, the metathesis reaction of ethene and butenes, produced through dimerization of ethene, was a key step for the propene formation. On the remaining two oxide catalysts, the major pathways were the common: ethanol→acetaldehyde→acetone→propene. The detailed reaction pathways, however, were different from each other. On Sc/In2O3, acetaldehyde was oxidized to acetic acid with water or a surface hydroxyl group and the resulting acetic acid was converted to acetone and carbon dioxide through ketonization. On the other hand, on Y2O3-CeO2, acetaldehyde was converted to ethyl acetate, and then it decomposed to form acetic acid and ethene. Acetic acid was converted to acetone and carbon dioxide in the same manner as that on Sc/In2O3. The by-production of much amounts of ethene was characteristic on Y2O3-CeO2. On the Sc/In2O3 oxide, a hydrogen molecule was active for the hydrogenation of acetone to 2-propanol. In contrast, on the Y2O3-CeO2 oxide, hydrogenation of acetone did not proceed with hydrogen but did with the co-fed ethanol, that is, by the Meerwein–Ponndorf–Verley reduction.
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      PubDate: 2014-12-09T08:34:52Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B




      PubDate: 2014-12-09T08:34:52Z
       
  • Selective hydroxylation of cyclohexene over Fe-bipyridine complexes
           encapsulated into Y-type zeolite under environment-friendly conditions
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Syuhei Yamaguchi , Tomohiro Fukura , Keiko Takiguchi , Chiharu Fujita , Maiko Nishibori , Yasutake Teraoka , Hidenori Yahiro
      Fe-bipyridine complexes encapsulated into Na-Y ([Fe(bpy)3]2+@Y) were prepared and their catalytic activities for oxidation of cyclohexene with hydrogen peroxide in CH3CN and H2O solvents were investigated. The prepared [Fe(bpy)3]2+@Y was characterized by several methods and it was found that slightly distorted or compressed [Fe(bpy)3]2+ ions were formed within supercages of Y-type zeolite. [Fe(bpy)3]2+@Y catalyst exhibited both higher activity and higher selectivity to 2-cyclohexen-1-ol in water solvent than another Fe catalysts. In addition, the selective hydroxylation of cyclohexene to 2-cyclohexen-1-ol with molecular oxygen was successfully achieved for [Fe(bpy)3]2+@Y catalyst.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Structure and SO3 decomposition activity of nCuO–V2O5/SiO2 (n=0, 1,
           2, 3 and 5) catalysts for solar thermochemical water splitting cycles
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Takahiro Kawada , Satoshi Hinokuma , Masato Machida
      SiO2-supported nCuO–V2O5 catalysts with different ratios (n =0, 1, 2, 3 and 5) were prepared to study their catalytic activity for SO3 decomposition, which is a key reaction necessary for solar thermochemical H2 production. Although four binary compounds, CuV2O6, Cu2V2O7, Cu3V2O8 and Cu5V2O10, were formed on three-dimensional (3-D) mesoporous SiO2 depending on the ratio (n), the thermal ageing caused their incongruent melting and precipitation of Cu2V2O7. The highly corrosive molten vanadate phase resulted in mesopore-to-macropore conversion of SiO2, which was accompanied by significant decrease of BET surface area and pore volume. Nevertheless, the structural conversion yielded copper vanadate with a high surface coverage of SiO2 cavity walls enabling efficient catalytic SO3 decomposition at moderated reaction temperatures (∼600°C). Among nCuO–V2O5/SiO2 catalysts, the highest catalytic activity was achieved for n =1, which corresponds to the phase with the lowest melting point (630°C) of the present system.
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      PubDate: 2014-12-09T08:34:52Z
       
  • On the performance and mechanisms of toluene removal by
           FeOx/SBA-15-assisted non-thermal plasma at atmospheric pressure and room
           temperature
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Meijuan Lu , Rong Huang , Junliang Wu , Mingli Fu , Limin Chen , Daiqi Ye
      FeO x /SBA-15 catalysts were prepared via impregnation and utilized for toluene removal in dielectric barrier discharge (DBD) plasma at atmospheric pressure and room temperature. Toluene removal was investigated in the environment of various mixed N2/O2 plasmas, showing that toluene removal efficiency and CO x selectivity were greatly increased by FeO x /SBA-15 and that the organic intermediates were greatly reduced by catalysts. In pure N2 plasma, the bulk oxygen in the catalyst was involved in the toluene oxidation, and the 3%FeO x /SBA-15 catalyst showed the optimal toluene oxidation activity. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and O2 temperature-programmed desorption (O2-TPD), showing that toluene oxidation was closely related to the highly dispersed nature of iron on the SBA-15 surface, the reduction temperature of Fe2+ and the oxygen adsorption ability of the catalyst. The pathways of toluene decomposition in the combination of FeO x /SBA-15 with a non-thermal plasma (NTP) system were proposed based on the identified intermediates.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Structural analysis of manganese oxides supported on SiO2 for benzene
           oxidation with ozone
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Hisahiro Einaga , Shintaro Yamamoto , Nanako Maeda , Yasutake Teraoka
      Catalytic oxidation of benzene with ozone was carried out over SiO2-supported manganese oxides (Mn/SiO2) prepared by impregnation methods using two kinds of manganese precursors, manganese nitrate and acetate. The structure of manganese oxides were characterized by X-ray diffraction and X-ray absorption measurements and effects of the manganese oxide structures on their catalytic properties were investigated. EXAFS studies revealed that by using manganese nitrate precursor in catalyst preparation, aggregated manganese oxides Mn2O3 were formed, whereas highly dispersed manganese oxides were formed when manganese acetate precursor was used. In both cases, the structures were not strongly affected by the manganese loading levels. The average oxidation state estimated form the absorption edge in the XANES region was also almost unchanged by changing the manganese loading for both catalysts. The catalytic activities of Mn/SiO2 for benzene oxidation with ozone at 343K were much higher for the catalysts prepared from manganese acetate precursors than those prepared from manganese nitrate precursor at any given manganese loading levels, indicating that highly dispersed manganese oxides on SiO2 exhibited much higher activities for the reaction than the aggregated manganese oxides on SiO2. The product distribution and the efficiency for ozone utilization were not so much affected by the manganese oxide structures.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Ordered mesoporous and bulk Co3O4 supported Pd catalysts for catalytic
           oxidation of o-xylene
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Yafei Wang , Changbin Zhang , Yunbo Yu , Renliang Yue , Hong He
      Ordered mesoporous Co3O4 (3D) and the bulk counterpart Co3O4 (B) were prepared by a nanocasting route and precipitation method, respectively. Pd was next loaded on both of them by an impregnation method. All catalysts were tested for the total oxidation of o-xylene in the temperature range of 150–300°C. Mesoporous Co3O4 (3D) exhibited better activity than Co3O4 (B), and Pd addition further improved the catalytic activity of both the mesoporous and bulk Co3O4. The BET and TEM results indicated that the mesoporous catalysts had uniform channel dimensions and the mesostructure was little affected by Pd addition. The TPR and XPS data indicated that Pd was much more exposed on the surface of Co3O4 (3D) than that of Co3O4 (B). TPD results showed that Pd/Co3O4 (3DL) could activate the oxygen species more easily than Pd/Co3O4 (BL). Therefore, Pd/Co3O4 (3DL) presented the best activity among the four catalysts and achieved 90% conversion of 150ppm o-xylene at 249°C at a space velocity of 60,000mLg−1 h−1.
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      PubDate: 2014-12-09T08:34:52Z
       
  • An experimental and DFT study of the adsorption and oxidation of NH3 on a
           CeO2 catalyst modified by Fe, Mn, La and Y
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Yue Peng , Weiwei Yu , Wenkang Su , Xu Huang , Junhua Li
      Four metals (Fe, Mn, La and Y) doped onto CeO2 were prepared by coprecipitation, and the corresponding slab models were constructed by DFT calculations to investigate the influences of dopants on the adsorption and oxidation of NH3 molecules. A higher reducibility, a larger quantity of labile surface oxygen and a greater extent of surface distortion were responsible for the higher NH3 activation of the Fe–Ce and Mn–Ce than the La–Ce and Y–Ce samples. Moreover, Fe–Ce and Mn–Ce provided more NH3 adsorption sites on the Lewis acid sites than La–Ce and Y–Ce, and the Mn dopant also generated a tightly bonded interaction with NH4 + on the Brønsted acid sites. The Mulliken charges of NH3 were also in agreement with the results above and indicated that the lone pair electrons of nitrogen can transfer to Fe or Mn cations, whereas this process is less favorable for the La or Y cations. The improvement of both the reducibility and acidity by Fe and Mn doping led to higher NH3 oxidation, whereas the enhancement was not considerable for La–Ce and Y–Ce.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Effect of preparation method of Co-promoted Pd/alumina for methane
           combustion
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Atsushi Satsuma , Takumi Tojo , Kohei Okuda , Yuta Yamamoto , Shigeo Arai , Junya Oyama
      Effect of preparation method of Co-promoted Pd/alumina for methane combustion was investigated. The addition of Co was carried out by two methods: co-impregnation of an aqueous solution of palladium nitrate and cobalt nitrate mixture, and sequential impregnation of an aqueous solution of cobalt nitrate to Pd/alumina. At the loading amount of 1–3wt%, the co-impregnated catalysts showed the higher activity than un-promoted Pd/alumina, while the sequentially impregnated catalysts showed the lower activity. XPS and IR spectra of adsorbed CO indicated that the oxidation state of Pd was not much affected by the preparation methods. Good dispersion of Co on the co-impregnated catalyst was demonstrated by HAADF-STEM images, while less interaction between Co and Pd was suggested on the sequentially impregnated catalysts. The profiles of temperature programmed reduction by methane indicated that the better dispersion of Co on Pd resulted in the better reducibility of Pd species, which is attributed to the higher methane oxidation activity of co-impregnated catalysts.
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      PubDate: 2014-12-09T08:34:52Z
       
  • The experiment and modeling of supported Wacker-type catalyst for CO
           oxidation at high relative humidity
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Li Wang , Wei Wang , Yanhui Zhang , Yanglong Guo , Guanzhong Lu , Yun Guo
      The difficulty of maintaining steady reaction is generated when water presents on supported Wacker-type catalyst in CO oxidation. Water can be adsorbed and condensed on catalyst surface, which facilitated Cu species transporting from the surface into the inner part of support. This weakened the contact between Pd and Cu species and caused their existence in low valence. The temperature difference between the co-reduction peak of Pd and Cu species and the individual Cu species in H2-TPR profile was found to have a linear relationship with the extent of deactivation. A mathematic model was developed and the effects of flow rate, CO concentration, temperature and relative humidity were also analyzed. The mathematic model well described the performance of CO oxidation at high relative humidity. Combined with the characteristic and modeling results, it was known that irreversible deactivation played a key role at lower temperature/higher relative humidity; while reversible deactivation was responsible for the instability at higher temperature/lower relative humidity.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Pd–Ce0.33Zr0.67O2–Al2O3 catalyst for propane oxidation:
           Interactions between the precious metal and support under the hydrothermal
           ageing
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Min Li , Xiaodong Wu , Jie Wan , Shuang Liu , Rui Ran , Duan Weng
      To investigate the influencing of the Ce0.33Zr0.67O2 and Al2O3 supports on the catalytic activity of Pd catalysts for propane oxidation, and possible Pd migration/interaction on different supports during the hydrothermal ageing, four samples were prepared by mixing one supported catalyst and another support powders either before or after the ageing treatment in a steam-containing air at 1050°C for 5h. It is unlikely for the occurrence of migration of Pd from one support to another during the thermal treatment as evidenced by the SEM and EDS results. IR spectra after CO introduction and H2-TPR results indicate the enlargement of the interface between Pd and another support during the thermal ageing, which may result in different Pd-support interaction. TPHD and XPS results further attribute the nature of this interaction to an electron transfer effect. The propane light-off temperature of co-aged Pd/Ce0.33Zr0.67O2 and Al2O3 is 45°C lower than the mixture of aged Pd/Ce0.33Zr0.67O2 and Al2O3, indicating the Pd–alumina interface is found to be more effective for the catalytic oxidation of propane.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Three way catalytic activity of thermally degenerated Pt/Al2O3 and
           Pt/CeO2–ZrO2 modified Al2O3 model catalysts
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Masakuni Ozawa , Takahiro Okouchi , Masaaki Haneda
      The effect of ceria and ceria–zirconia modification to alumina on the three-way catalytic (TWC) performance of alumina supported Pt catalyst was investigated. Sintering of Pt was induced by thermal treatment at 1000°C and suggested the inhibition effect of sintering by doping Ce on Al2O3 support. TWC activity for three catalysts follows the sequence of Pt/Ce0.8Zr0.2O2/Al2O3 >Pt/CeO2/Al2O3 ≫Pt/Al2O3. Low temperature CO conversion increased clearly upon the addition of CeO2 and CeO2–ZrO2 into Pt/alumina, indicating that the OSC promotes CO oxidation activity and NO is reduced by C3H6 in light-off process. TWC performance with 0.5Hz dynamic condition at 620°C indicated better conversions with the same sequence corresponding to OSC of each catalyst. In model transient experiment, CO conversion in rich phase with the sequence of Pt/Ce0.8Zr0.2O2/Al2O3 >Pt/CeO2/Al2O3 ≫Pt/Al2O3 indicated that the OSC of CeO2 and Ce0.8Zr0.2O2 solid solution on alumina was a major cause for improvement of CO conversion in total dynamic operation even after thermally aged Pt catalysts. Regarding NO x conversion in model transient experiment, the NO x (NO+NO2) low concentration versus time is delayed (with more NO x removal activity) in the cyclic rich to stoichiometric condition for catalysts with OSC component of CeO2 and Ce0.8Zr0.2O2. The oxidized and recovered state of Pt on ceria zirconia should be related to NO removal reaction. Under rich-lean cycle condition, total oxidation and reduction of catalyst affect both transient CO and NO conversions over Pt, so that oxygen storage/release functions of OSC catalyst are effective to total buffering to A/F fluctuation.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Direct NO decomposition over C-type cubic Y2O3–Pr6O11–Eu2O3
           solid solutions
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Toshiyuki Masui , Shunji Uejima , Soichiro Tsujimoto , Ryosuke Nagai , Nobuhito Imanaka
      C-type cubic Y2O3–Pr6O11–Eu2O3 solid solutions were synthesized by a co-precipitation method and their catalytic activities for direct NO decomposition were investigated. Among the catalysts synthesized, the (Y0.78Pr0.15Eu0.07)2O3±δ catalyst exhibited high NO decomposition activity; NO conversion to N2 was as high as 84% at 900°C in the absence of O2 (NO/He atmosphere). This catalyst also sustained a high level of NO conversion even in the presence of O2 or CO2, compared with those of the conventional perovskite-type catalyst for direct NO decomposition.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Theoretical investigation of novel two-step decomposition of nitric oxide
           over Fe(II) ion-exchanged zeolites using DFT calculations
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Koutarou Kawakami , Masaru Ogura
      A new method for the direct catalytic decomposition of nitric oxide (NO) is proposed in order to overcome several well-known problems toward its practical use. In this novel methodology, NO is first selectively adsorbed on Fe(II) ion-exchanged zeolites (LTA, MFI, and FAU) in the presence of excess oxygen; the concentrated NO in the zeolite microchannels is then decomposed by low-energy irradiation. The NO molecule is selectively adsorbed on Fe(II)–zeolites under the excess oxygen conditions, and that NO bond cleavage is more likely to occur for NO on Fe(II) than in the gas phase, because Fe(II) supplies an electron into an orbital of the NO molecule. A dinitrosyl species formed on Fe(II) sites in zeolites is decomposed via a N2O intermediate with lower activation energy. Achieving a closer distance between the two nitrogen atoms of two NO molecules by concentrating them on Fe(II) in zeolitic microcages is key to accelerate the decomposition with greatly reduced energy requirements. Based on these results, a catalytic redox cycle of Fe(II) in zeolites for NO decomposition is proposed, where the largest activation energy (the rate-determining step) is for the reaction 2NO→N2O+O (ca. 160kJ/mol), which is higher than that of NO decomposition on Cu-ZSM-5 (ca. 135kJ/mol). It is proposed that imitating the molecular mechanism of fungal nitric oxide reductase (P450nor) by utilizing an adjacent proton on Fe(II) ion-exchanged proton-form zeolite, the required energy for 2NO→N2O+O decreases further (ca. 40kJ/mol), allowing for successful reaction initiation with low-energy irradiation such as microwaves.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Catalytic performance of supported Ag nano-particles prepared by liquid
           phase chemical reduction for soot oxidation
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Masaaki Haneda , Atsuya Towata
      The effect of size and morphology of Ag catalysts supported on ZrO2 on the soot oxidation activity was investigated. Spherically shaped Ag nano-particles with the size of ca. 16nm, prepared by liquid-phase chemical reduction, supported on ZrO2 (Ag/ZrO2(NP)) exhibited outstanding performance for soot oxidation with gaseous O2 in tight and loose contact modes, compared with hemispherically shaped Ag particles prepared by impregnation (Ag/ZrO2(IMP)). The exceptional performance of Ag/ZrO2(NP) for soot oxidation in loose contact mode was explained by relatively good catalyst-soot contact state and effective migration of active oxygen species from the catalyst to soot. In addition to morphological effect, Ag nano-particles supported on ZrO2 were found to be stabilized in the surface valence state of Ag+, and then oxygen species participating in soot oxidation can be effectively activated on Ag+ sites. We concluded that the presence of Ag+ sites on the surface of Ag nano-particles is responsible for high soot oxidation activity.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Simulation of continuously regenerating trap with catalyzed DPF
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Kazuhiro Yamamoto , Tatsuya Sakai
      For reduction of particulate matter (PM) including soot in diesel exhaust gas, a diesel particulate filter (DPF) has been developed. However, it would be plugged with PM to cause an increase of filter backpressure. If the backpressure is too high, the fuel consumption rate unexpectedly increases and the engine output may decrease. Then, the filter must be regenerated by oxidizing PM. The system where PM is trapped and oxidized simultaneously is called a continuously regenerating DPF. A catalyst such as platinum is used for the reduction of PM oxidation temperature. Since platinum is a precious and rare metal, the amount of catalyst must be suppressed. In this study, we simulated the continuously regenerating trap system with catalyzed DPF by a lattice Boltzmann method (LBM). For the soot oxidation rate with catalysts, reaction parameters such as activation energy were evaluated by an engine test bench. In the simulation, five cases with different catalyst-coating were considered. Based on the filter backpressure, the coating area for the reduction of catalysts was discussed.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Photocatalytic and photoelectrocatalytic degradation of small biological
           compounds at TiO2 photoanode: A case study of nucleotide bases
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Guiying Li , Xiaolu Liu , Taicheng An , Hai Yang , Shanqing Zhang , Huijun Zhao
      Photocatalytic (PC) and photoelectrocatalytic (PEC) degradation of small biological compounds such as nucleotide bases were carried out because of the nucleotide bases are the building blocks of large biomolecules, nucleic acids. These small biological compounds, four different nucleotide bases, can be photocatalytically and photoelectrocatalytically degradable, and the degradation efficiencies of PEC method were found to be higher than those of PC method for all compounds investigated. Also, we tried to propose the photocatalytical and photoelectrocatalytic degradation mechanisms of nucleotide bases, but the performance was unsuccessful. However, organic nitrogen in the original compounds was found to be oxidized to either NH3/NH4 + or NO3 − or both, depending on the chemical structures of the nucleotide bases and the degradation methods used. Based on both the experimental results and the theoretically calculated frontier electron densities (FED) values of 2FEDHOMO 2 and FEDHOMO 2 +FEDLUMO 2, the conclusion can be demonstrated as the reaction mechanisms/pathways of PEC processes differed remarkably from that of PC processes.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Rational removal of stabilizer-ligands from platinum nanoparticles
           supported on photocatalysts by self-photocatalysis degradation
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Zhi Jiang , Wenfeng Shangguan
      The emergence of precise synthesis supported catalysts based on colloidal method is of fundamental interest for catalysis community. Stabilizer-ligands are necessary to be removed after synthesis process to get “clean” catalyst. Here we reported that a procedure, self-photodegradation in vacuum, could effectively remove the ligands on the surface of photocatalyst oxide without affecting the morphology and electron state of particle and support, while calcination method was identified to influence both of them. We showed how that would result in quite a different performance in photocatalysis hydrogen evolution from aqueous methanol solution. These results thus outlined a rational and green strategy for “collaborating” with photocatalysis process to build up designed supported catalyst architectures.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Enhancement of Pd-catalyzed Suzuki–Miyaura coupling reaction
           assisted by localized surface plasmon resonance of Au nanorods
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Meicheng Wen , Shuhei Takakura , Kojirou Fuku , Kohsuke Mori , Hiromi Yamashita
      Localized surface plasmon resonance (LSPR) induced by Au nanorods was employed to enhance the catalytic activity of Pd-driven Suzuki–Miyaura coupling reaction under light irradiation at ambient temperatures. The optical properties of the obtained Pd–Au/SiO2 samples were investigated by UV–vis spectroscopy, which exhibit intense absorption bands in the low energy region, and the ratio between Pd NPs and Au nanorods has a significant impact on turning the optical property and catalytic performance of Pd–Au alloy. The optimized weight ratio of Pd–Au hybrid catalyst for Suzuki–Miyaura coupling reaction under light irradiation was found to be 1:0.5. The enhanced activity can be attributed to the cooperative promoting effects between Au nanorods and Pd nanoparticles in effective conversion of solar energy for generation of energetic electrons to activate the palladium and increasing temperature in the reaction solution.
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      PubDate: 2014-12-09T08:34:52Z
       
  • Corrigendum to: CO-insertion mechanism based kinetic model of the
           Fischer–Tropsch synthesis reaction over Re-promoted Co catalyst
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part B
      Author(s): Branislav Todic , Wenping Ma , Gary Jacobs , Burtron H. Davis , Dragomir B. Bukur



      PubDate: 2014-12-09T08:34:52Z
       
  • Hydrocarbon fuel synthesis from sorbitol over bifunctional catalysts:
           Association of tungstated titania with platinum, palladium or iridium
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Léa Vilcocq , Amandine Cabiac , Catherine Especel , Sylvie Lacombe , Daniel Duprez
      To selectively transform sorbitol into hydrocarbons in aqueous phase, new bifunctional catalytic systems are designed by associating a hydrogenating metallic catalyst (M/ZrO2, M=Pt, Ir or Pd) and a dehydrating acidic catalyst (TiO2–WO x ) in a mechanical mixture. Zirconium oxide was chosen as support because it has virtually no dehydration activity and gives a good stability to the metal in water. This stability is evaluated through several characterizations before and after contact with the aqueous reaction medium. It is proposed that stability in water is driven by two parameters. The support stability is a key parameter for the overall catalyst stability, and the metal–support interaction determines the sintering extent. The nature of the metal has also an important influence on the activity and selectivity of the bifunctional M/ZrO2 +TiO2–WO x system for sorbitol transformation. Pd and Ir are slightly active and mainly transform sorbitol into isosorbide, whereas Pt is selective for long-chain alkane production. The mass ratio between metallic and acidic catalysts in the mechanical mixture also modifies the yield structure, with a Pt/ZrO2:TiO2–WO x 20:80 ratio for optimal liquid hydrocarbons production.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Role of ruthenium on the catalytic properties of CeZr and CeZrCo mixed
           oxides for glycerol steam reforming reaction toward H2 production
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): L.M. Martínez T , M. Araque , M.A. Centeno , A.C. Roger
      The effect of ruthenium on the physico-chemical properties of CeZr and CeZrCo mixed oxides for H2 production by glycerol steam reforming reaction has been studied. The combination of in situ Raman spectroscopy under both reductive and oxidative conditions, H2/O2 pulses and XRD, Raman, BET analysis, H2-TPR and TPD-TPO analyses contributed to the determination of the structural and textural properties, redox behavior, re-oxidation capacity and resistance to carbon deposition of the synthesized catalysts. The results show that the catalytic activity is improved by the (positive) cooperative and complementary effect between cobalt and ruthenium that favors the selectivity toward the steam reforming, selective to H2, with respect to the unselective thermal decomposition of glycerol. Ruthenium stabilizes the cobalt cations inserted in the fluorite structure preventing its rejection as Co3O4; and provides the necessary hydrogen to reduce Ce4+. The combination cobalt–ruthenium modifies positively the redox properties of the catalysts, increases the re-oxidation capacity (OSC) and promotes the gasification of the carbon deposits. Under the reaction conditions, the decrease in glycerol conversion came along with a change of selectivity. The formation of H2 and CO2 were strongly decreased, while the formation of CO, C2H4 and condensable products (mainly hydroxyacetone) increase. The differences in the catalytic stability and activity of the catalysts are related to the capability of the catalysts to activate H2O under the reaction conditions, favoring the steam reforming reaction over the thermal decomposition.
      Graphical abstract image

      PubDate: 2014-12-06T08:31:50Z
       
  • Hydrogen production by reforming of acetic acid using La–Ni type
           perovskites partially substituted with Sm and Pr
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): K.A. Resende , C.N. Ávila-Neto , R.C. Rabelo-Neto , F.B. Noronha , C.E. Hori
      The condensation of gases from the pyrolysis of biomass leads to a liquid compound called bio-oil. This oil can be divided into two fractions: one aqueous and another non-aqueous. The aqueous fraction does not have a high market value and it is usually discarded. However, this mixture has considerable amounts of organic compounds, which can be potential renewable sources of hydrogen. Steam reforming has been the most studied reaction to produce hydrogen from the aqueous fraction of bio-oil. Due to the diversity of organic compounds found in this aqueous fraction, model compounds have usually been used to study this mixture. Among the compounds used to represent the aqueous fraction of bio-oil, acetic acid is the most popular. Nickel-based catalysts are traditionally used for reforming reactions. An alternative to combine high Ni content employed in catalysts, this kind of process with desirable values of dispersion is to use perovskite-type precursors (LaNiO3). Therefore, the objective of this study was to investigate the production of hydrogen from the aqueous fraction of bio-oil. More specifically, in this work, LaNiO3, LaPrNiO3 and LaSmNiO3 were tested as precursors for catalysts in the reaction of steam and oxidative reforming of acetic acid. During the reaction, the catalysts showed the formation of the same products: H2, CO, CH4, CO2, C3H6O, but with different selectivities. All samples presented good selectivity for hydrogen formation, and the presence of Pr and Sm just slightly affected the catalytic performance. Due to the large accumulations of coke observed during the reaction of steam reforming, a small amount of O2 was added to the mixture. The presence of this oxidant improved catalytic activity without reducing the amount of hydrogen produced. Furthermore, it helped to reduce the deposits of coke, maintaining the catalytic activity during 24h of reaction.
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      PubDate: 2014-12-06T08:31:50Z
       
  • The effects of stepped sites and ruthenium adatom decoration on methanol
           dehydrogenation over platinum-based catalyst surfaces
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): B.Y. Liu , J.M. Jin , X. Lin , C. Hardacre , P. Hu , C.A. Ma , W.F. Lin
      A density functional theory study of methanol dehydrogenation over stepped Pt(211) surfaces without and with Ru modification was carried out to understand fuel catalytic reactions on Pt-based catalysts. Two main pathways of the CH3OH dehydrogenation were examined: the O–H pathway which was initiated by O–H bond scission to form the methoxy (CH3O) intermediate followed by sequential cleavage of C–H bonds to CO, and the C–H pathway which was initiated by C–H bond scission to form the hydroxymethyl (CH2OH) followed by two C–H bond cleavages to COH and then CO. Possible crossover reactions between the O–H and C–H pathways were also computed. Compared to flat Pt(111), stepped Pt(211) increases the adsorption energies of intermediates, making no significant contribution to decreasing the reaction barriers of most elementary steps involved, except in the first hydrogen scission. However, on the Ru-modified surface, a significant reduction was found in reaction barriers for the first step of the C–H bond scission and a number of further dehydrogenation steps crossing over to the O–H pathway, with the most facile paths identified. Our data reveals the complexity of methanol catalytic reaction processes at the atomic level and contributes to a fundamental understanding of fuel reactions on Pt-based catalysts.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Ni- and PtNi-catalysts supported on Al2O3 for acetone steam reforming:
           Effect of the modification of support with Ce, La and Mg
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): R.M. Navarro , R. Guil-Lopez , A.A. Ismail , S.A. Al-Sayari , J.L.G. Fierro
      Hydrogen production from acetone steam reforming was studied using bimetallic PtNi catalysts supported on modified alumina. La-, Ce- and Mg-oxides were used as support modifiers in order to neutralize acidity and/or to improve water adsorption and OH− surface mobility of Al2O3 support. Characterization of the sample showed that metal-support interactions and the size of metallic Ni at surface differ depending on the oxide added to the alumina support. Reforming activity on Ni and Pt–Ni supported on X-modified-Al2O3 catalysts (X=La, Ce, or Mg) showed that both metal and support, play an essential role in the catalytic behavior on the steam reforming of acetone. The sequence of gasification capacity over monometallic samples (Ni/LaAl>Ni/MgAl>Ni/CeAl) points out that acidity of supports participates in the acetone reforming mechanism over these catalysts. Addition of Pt to monometallic Ni catalysts only has a beneficial effect on the reforming capacity of the Ni/LaAl sample. Improvement in the reforming capacity of the PtNi/LaAl catalyst is believed to be a consequence of the promoting effect of Pt that leads to an increase in the stability of metallic Ni particles on catalyst surface together with the ability of Pt to enhance the mobility of the H-atoms formed in the reaction could help the gasification of carbon precursors formed during the reforming of acetone.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Comparative study on steam and oxidative steam reforming of ethanol over
           2KCo/ZrO2 catalyst
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Magdalena Greluk , Piotr Rybak , Grzegorz Słowik , Marek Rotko , Andrzej Machocki
      The steam rreforming and oxidative steam reforming of ethanol were studied over 2KCo/ZrO2 catalyst which was prepared by support impregnation with cobalt nitrate-citric acid solution. The catalyst was characterized by N2 adsorption, H2 chemisorption, X-ray fluorescence, Raman spectroscopy, temperature-programmed reduction, temperature-programmed oxidation. The results indicate that the optimum EtOH/O2 molar ratio of 1/0.9 corresponds to the oxygen amount which prevents coke formation on the catalyst, when a constant molar ratio of H2O/EtOH=9/1. However, the presence of oxygen causes oxidation of metallic particles which leads to oxidized cobalt active phases that behave poorly in the reformation reactions. Thus, compared to the SRE, both activity and selectivity to desired products over the 2KCo/ZrO2 catalyst in the OSRE process is definitely lower and the higher temperature for complete conversion of ethanol is required.
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      PubDate: 2014-12-06T08:31:50Z
       
  • The study of the performance of PtNi/CeO2–nanocube catalysts for low
           temperature steam reforming of ethanol
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Tamara Siqueira Moraes , Raimundo Crisostomo Rabelo Neto , Mauro Celso Ribeiro , Lisiane Veiga Mattos , Marios Kourtelesis , Spyros Ladas , Xenophon Verykios , Fábio Bellot Noronha
      Promotion of Ni/CeO2-nanocube with small amounts of Pt was shown to significantly enhance catalyst stability for steam reforming of ethanol. The main reaction pathway appeared to be essentially ethanol decomposition toward carbon oxides (CO/CO2), H2 and CH4. Further investigation of the stabilizing effect brought about by the presence of the noble metal by different techniques (XPS, TPSR, ethanol TPD, in-situ XAFS) revealed that Pt segregation toward the surface of the Ni particles minimized the formation of nickel carbide phase and consequently decreased catalyst deactivation. Pt addition promotes the hydrogenation of highly active carbon species adsorbed at the surface at a higher rate than carbon diffusion into bulk nickel. These findings points to an alternative way for minimizing the problem of carbon buildup on Ni-based catalysts for steam reforming of ethanol.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Cobalt boride catalysts for small-scale energy application
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): V.I. Simagina , A.M. Ozerova , O.V. Komova , G.V. Odegova , D.G. Kellerman , R.V. Fursenko , E.S. Odintsov , O.V. Netskina
      The objects of investigation were cobalt boride catalysts for a one-step production of hydrogen from NaBH4. Cobalt oxides prepared by calcination of cobalt salts at 500°C were used as precursors of the catalyst active phase. It was shown that the nature of the cobalt oxide precursor has a substantial influence on the rate of formation of active component in the reaction medium of sodium borohydride and, hence, on its activity in NaBH4 hydrolysis. The length of the activation period and catalytic activity do not correlate with the dispersion and the specific surface area of the synthesized Co3O4 samples but depend on their inhomogeneity and the defect structure of the oxide due to the distribution of cobalt ions in the crystal lattice. The more defects are present in of Co3O4 the faster the rate of its reduction and, hence, the higher its catalytic activity in NaBH4 hydrolysis. On the basis of active oxide prepared from cobalt chloride, solid state NaBH4 pellets have been prepared. For the first time, NaBH4 pellets were used as a source of H2 source for a thermo-electrical energy conversion device based on combustion technologies.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Catalyst development for the dehydrogenation of MCH in a microstructured
           membrane reactor—For heat storage by a Liquid Organic Reaction Cycle
           
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): H. Kreuder , C. Müller , J. Meier , U. Gerhards , R. Dittmeyer , P. Pfeifer
      Liquid organic hydrides can act as energy storage from renewable sources in a cycle of hydrogenation and dehydrogenation. In this work, a feasibility study for heat storage by methylcyclohexane dehydrogenation as a system component in a Liquid Organic Reaction Cycle (LORC) is presented. The endothermic dehydrogenation of methylcyclohexane was investigated in a microstructured reactor, in order to supply reaction heat efficiently. The integration of a membrane into the microstructured reactor for in-situ pure hydrogen removal is intended in further studies. In order to obtain an efficient microstructured membrane reactor, basic catalyst studies were performed. For this purpose different catalysts were prepared and applied to the microstructured reactor. A catalyst containing Pt as active metal and Al2O3 as porous support was selected as the most active catalyst and it was further characterized by BET, H2 chemisorption, SEM, EPMA and ICP-OES. The different catalysts deactivated rapidly by coke formation at the entrance of the microstructured reactor. Carbon black was analyzed on the catalyst surface by Raman spectroscopy. The addition of H2 or a higher pressure level in the reaction zone delayed the deactivation rate considerably. Therefore, the utilization of a microstructured membrane reactor is beneficial; it provides conditions to reduce coke formation like a higher reaction pressure and continuous H2 partial pressure in the catalyst zone if sweep gas is absent on the permeate side of the membrane.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Start-up behavior of a LaMnO3 partially coated monolithic combustor at
           high pressure
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Valeria Di Sarli , Paola S. Barbato , Almerinda Di Benedetto , Gianluca Landi
      In this work, a CFD model was used to investigate the transient behavior of a perovskite-based monolith during catalytic combustion of methane at high pressure. Two configurations were studied, the configuration of a fully coated monolith and that of a partially coated monolith (with only the external channels coated by the catalyst). Simulations were run at different heat transfer coefficients and wall thermal conductivities. The performance of the partially coated monolith was compared to that of the fully coated monolith. Numerical results have shown that, when setting high thermal conductivity and/or high heat transfer coefficient, the partially coated monolith, which provides complete fuel conversion with much lower catalyst load, can operate at low temperature and low ignition time and with reduced cold-start CH4 emissions.
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      PubDate: 2014-12-06T08:31:50Z
       
  • CO2 hydrogenation to methanol over CuZnGa catalysts prepared using
           microwave-assisted methods
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Weijie Cai , Pilar Ramirez de la Piscina , Jamil Toyir , Narcis Homs
      A series of CuZnGa catalysts was synthesized by microwave-assisted method and their performance for CO2 hydrogenation to methanol was measured under a range of reaction conditions (temperatures between 250°C and 270°C and pressure up to 4.5MPa). The influence of the preparation method on the physicochemical properties of catalysts was studied by N2 adsorption, XRD, TPR, XPS, N2O titration and CO2 adsorption followed by temperature programmed desorption and calorimetry. The results indicate that the one-pot microwave-assisted precipitation method used in the preparation of the (CuZnGa)MW catalyst, promoted copper and Ga2O3 dispersion. Moreover, the mean basic site strength of (CuZnGa)MW was higher than that of the other catalysts prepared. All of these factors were found to affect its catalytic performance greatly in terms of CO2 conversion and methanol selectivity. (CuZnGa)MW was highly stable and produced 4.87mol methanol kgcat −1 h−1 at 250°C with a selectivity of approximately 50% (P =4.5MPa, GHSV=3000h−1, CO2/H2 =1/3). The strong interaction between copper and support prevented metallic copper sintering, affording high stability of catalyst. The promoting effect was related to an intimate association between highly dispersed copper species and strong basic ZnO species in the presence of small particles of Ga2O3.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Chemical energy storage in gaseous hydrocarbons via iron
           Fischer–Tropsch synthesis from H2/CO2—Kinetics, selectivity
           and process considerations
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): M. Iglesias G. , C. de Vries , M. Claeys , G. Schaub
      The potential of a new practical application of Fischer–Tropsch synthesis is investigated, the production of C2–4 components to increase the heating value of substitute natural gas (SNG), starting from CO2 and H2, produced from renewable electricity. This process route offers the possibility to convert electrical energy into chemical energy. The resulting chemical energy carrier can be stored in the natural gas grid, easy to distribute. An iron-based catalyst promoted with potassium (100g Fe/2g K) is studied over a wide range of operation conditions to investigate its suitability to produce C2–C4 components from H2/CO2 mixtures. The achieved hydrocarbon distribution (α =0.2–0.3) allows for the production of Substitute Natural Gas components (68 C% C1, 30 C% C2–C4, C5+ approx. 2 C%). The catalyst stability is good, at least for 50 days. The hydrocarbon selectivity remains almost constant during the experiment, methane becoming slightly more predominant over time. Catalyst activity seems to be strongly influenced by the (H2O/H2)out ratio (possibly due to oxidation), which correlates with CO2 conversion. At high values of (H2O/H2)out, the activity of the catalyst seems to change and cannot be described using the same reaction rate kinetics determined for lower (H2O/H2)out values. The maximal CO2 conversion achieved is 44% (p =2Mpa, (H2/CO2)in =8). Experimental results show that higher conversions could not be achieved neither with an increase in temperature nor in modified residence time. The H2/CO2 inlet ratio is the most promising parameter to reach high CO2 conversions without a high oxidation potential in the product gas. Interesting catalytic effects have been identified, however experimental results will be supported by additional work in order to get a better understanding of the CO2 hydrogenation under Fischer–Tropsch conditions with iron catalysts.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Nature and reactivity of the surface species observed over a supported
           cobalt catalyst under CO/H2 mixtures
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Anaëlle Paredes-Nunez , Davide Lorito , Nolven Guilhaume , Claude Mirodatos , Yves Schuurman , Frederic C. Meunier
      The nature and reactivity of the surface species present at the surface of a Co-supported sample were investigated by in situ and operando DRIFTS. The operando DRIFTS data collected over a 15% Co/Siralox® showed that the state of the surface was typically carbon-poor under our operating conditions, i.e. the nature of the surface was metallic rather than carbidic. A significant modification of the cobalt surface was observed with time on stream. An accumulation of waxes was also noted at the catalyst surface, despite the fact that the reaction was performed at ambient pressure. Chemical transient experiments carried out by removing CO from the feed indicated that the various types of CO(ads) present (e.g. linear and bridged) displayed an apparent uniform reactivity. In contrast, two types of formates reactivity were observed, while the IR spectra of these formate species were undistinguishable. The faster reacting formates, possibly adsorbed at the interface of Co and the support or directly on an oxidic phase of cobalt, could potentially be an intermediate in the formation of the methanol side-product observed under our reaction conditions.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Effect of rhodium on the water–gas shift performance of Fe2O3/ZrO2
           and CeO2/ZrO2: Influence of rhodium precursor
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Abrar A. Hakeem , Jaikishen Rajendran , Freek Kapteijn , Michiel Makkee
      Iron oxide and ceria are known to have redox properties and their performance as a water–gas shift (WGS) catalyst is investigated at low H2O/CO ratio (∼2) in the temperature range of 623–773K at 21bar with space velocities relevant for industrial applications. The WGS activity of supported iron oxide is higher than that of supported ceria. The addition of rhodium to supported iron oxide (Rh/Fe2O3/ZrO2) enhances the WGS activity while for supported ceria (Rh/CeO2/ZrO2) rhodium enhances the methanation activity at high pressure (21bar) WGS conditions. The improved hydrogen production by enhancement of the WGS activity over Rh/CeO2/ZrO2 due to rhodium is undone by the consumption of hydrogen in the methane production. Methane is produced over Rh/Fe2O3/ZrO2 and Rh/CeO2/ZrO2 catalysts due to the presence of rhodium. Rhodium nitrate as precursor results in a better WGS activity performance over Rh/Fe2O3/ZrO2 and a better methanation activity is obtained over Rh/CeO2/ZrO2 in comparison with the use of rhodium chloride precursor. The presence of residual chlorine suppresses the promotional WGS activity due to rhodium as well as the methanation activity. In both ex-nitrate and ex-chloride catalysts the smaller rhodium particles are highly active for methane formation.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Low-temperature water–gas shift on Pt/Ce0.5La0.5O2−δ:
           Effect of support synthesis method
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Klito C. Petallidou , Soghomon Boghosian , Angelos M. Efstathiou
      A series of 0.5wt% Pt/Ce0.5La0.5O2− δ (Ce:La=1:1) catalysts, the supports of which were prepared by different methods, namely: (i) sol–gel using citrate or oxalate as complexing agent, (ii) pechini, and (iii) urea co-precipitation, were investigated for the first time towards the water–gas shift (WGS) reaction in the 250–350°C range and 1atm total pressure. Towards a better understanding of the effect of support synthesis method on the intrinsic kinetic rate of WGS expressed per gram of catalyst (μmolCOg−1 s−1) or per length of the perimeter of Pt-support interface (μmolCOcm−1 s−1), a suite of various characterisation methods such as: in situ Raman, temperature-programmed techniques (TPD-H2, TPD-NH3, TPD-CO2), powder XRD, and oxygen storage capacity (OSC) measurements were applied. The intrinsic kinetic rate of WGS (μmolCOg−1 s−1) was correlated with the concentration of the active “carbon-containing” (C-pool) and “hydrogen-containing” (H-pool) reaction intermediates formed within a reactive zone (Δx, Å) around each Pt nanoparticle (1.2–1.5nm), parameters that were estimated via SSITKA and non steady-state transient isotopic and titration with water operando experiments. The urea co-precipitation method (U) resulted in the formation of a Ce1− x La x O2− δ solid solution with different composition (Ce:La atom ratio) than that formed by the other synthesis methods, which may be the main reason for Pt/Ce0.5La0.5O2− δ (U) to exhibit the highest by far CO conversion and kinetic rate towards the WGS compared to the other supported Pt catalysts. The same method (U) resulted in the formation of La2O3 as opposed to the other methods. However, this was not considered as the main reason for explaining the higher activity of Pt supported on Ce0.5La0.5O2− δ (U) compared to the other carriers. The Ce0.5La0.5O2− δ (U) was also found to possess the highest surface acidity and basicity compared to the other supports but lower OSC (μmolg−1) (by more than 30% in the 250–550°C range) than Ce0.5La0.5O2− δ prepared by the citrate sol–gel method, in harmony with the lower content of O vacancies in Ce0.5La0.5O2− δ (U) as evidenced by Raman studies. Transient DRIFTS formate (HCOO–) decomposition kinetic experiments towards CO2 and H2 formation have illustrated the importance of the presence of Pt and support composition.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Co-catalytic enhancement of H2 production by SiO2 nanoparticles
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Panagiota Stathi , Yiannis Deligiannakis , Maria Louloudi
      SiO2 nanoparticles, of varying size 9–55nm, show significant co-catalytic activity for H2-production from HCOOH by the homogenous FeII/P(CH2CH2PPh 2)3 catalyst. Particle size and specific surface area are shown to play key-role in this phenomenon. Larger nanoparticles have better co-catalytic effect. Arrhenius analysis reveals that the significant co-catalytic effect can is attributed to a lowering of the activation energy of the rate-limiting step by ΔE a =16–36kJ/mol. This phenomenon is attributed to a thermodynamic promotion of HCOOH deprotonation by the SiO2 nanoparticles, accelerating in this way coordination of HCOO− on the FeII atom of active catalyst, during catalysis. The surface Si–O–Si bridges are shown to be responsible for the promotion of this HCOOH deprotonation, while surface-adsorbed H2O retards the co-catalytic efficiency.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Thermocatalytic decomposition of propane for pure hydrogen production and
           subsequent carbon gasification: Activity and long-term stability of
           Ni/Al2O3 based catalysts
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Stefan Neuberg , Helmut Pennemann , Ole Wiborg , Martin Wichert , Ralf Zapf , Athanassios Ziogas , Gunther Kolb
      Ni/Al2O3 catalysts with nickel loadings from 10 to 40wt.% prepared by wet impregnation have been tested for the thermocatalytic decomposition of propane in the temperature range from 700 to 1100°C in a fixed bed reactor. Full conversion of propane was observed in all cases. The hydrogen yield was found to increase at higher reaction temperature, at lower temperatures significant quantities of CH4 were observed in the product gas. The Ni loading determined stability of the catalyst. After performing the catalytic decomposition reaction for a certain time, the carbon formed on the catalyst surface was removed by combustion with air. During this regeneration process carbon monoxide was always the main product. Repeated cycles of decomposition and regeneration were carried out. By using an automated control device, it was possible to ensure a continuous operation of the reactor for 65h. For this period, stable H2 yield was observed with a catalyst containing 40wt.% Ni supported by Al2O3. Fresh and spent catalysts were analyzed by BET, X-ray fluorescence (XRF), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Carbon formed by the decomposition reaction was analyzed by thermogravimetric analysis (TGA) and SEM.
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      PubDate: 2014-12-06T08:31:50Z
       
  • H2 production by sorption enhanced steam reforming of biomass-derived
           bio-oil in a fluidized bed reactor: An assessment of the effect of
           operation variables using response surface methodology
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): María V. Gil , Javier Fermoso , Fernando Rubiera , De Chen
      High-purity H2 was produced by the sorption enhanced steam reforming (SESR) of acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, in a fluidized bed reactor. A Pd/Ni–Co hydrotalcite-like material (HT) and dolomite were used as reforming catalyst and CO2 sorbent, respectively. The hydrogen yield and purity were optimized by response surface methodology (RSM) and the combined effect of the reaction temperature (T), steam-to-carbon molar ratio in the feed (steam/C) and weight hourly space velocity (WHSV) upon the sorption enhanced steam reforming process was analyzed. T was studied between 475 and 675°C, steam/C ratio between 1.5 and a 4.5mol/mol and WHSV between 0.893 and 2.679h−1. H2 yield, H2 selectivity and H2 purity, as well as the CH4, CO and CO2 concentrations in the effluent gas, were assessed. The operating temperature proved to be the variable that had the greatest effect on the response variables studied, followed by the WHSV and the steam/C ratio. The results show that the H2 yield, H2 selectivity and H2 purity increased, while the CH4, CO and CO2 concentrations decreased, concurrently with the temperature up to around 575–625°C. Higher values of the steam/C ratio and lower WHSV values favored the H2 yield, H2 selectivity and H2 purity, and reduced the CH4 concentration. It was found that the SESR of acetic acid at atmospheric pressure and 560°C, with a steam/C ratio of 4.50 and a WHSV of 0.893h–1 gave the highest H2 yield of 92.00%, with H2 purity of 99.53% and H2 selectivity of 99.92%, while the CH4, CO and CO2 concentrations remained low throughout (0.04%, 0.06% and 0.4%, respectively). The results also suggested that a slow CO2 capture rate led to a poor level of hydrogen production when the SESR process was carried out at low temperatures, although this can be improved by increasing the sorbent/catalyst ratio in the fluidized bed.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Biogas reforming using renewable wind energy and induction heating
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): María Natividad Pérez-Camacho , Jehad Abu-Dahrieh , David Rooney , Kening Sun
      While the benefits of renewable energy are well known and used to influence government policy there are a number of problems which arise from having significant quantities of renewable energies on an electricity grid. The most notable problem stems from their intermittent nature which is often out of phase with the demands of the end users. This requires the development of either efficient energy storage systems, e.g. battery technology, compressed air storage etc. or through the creation of demand side management units which can utilise power quickly for manufacturing operations. Herein a system performing the conversion of synthetic biogas to synthesis gas using wind power and an induction heating system is shown. This approach demonstrates the feasibility of such techniques for stabilising the electricity grid while also providing a robust means of energy storage. This exemplar is also applicable to the production of hydrogen from the steam reforming of natural gas.
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      PubDate: 2014-12-06T08:31:50Z
       
  • Methane steam reforming at low temperature: Effect of light alkanes’
           presence on coke formation
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Sofia D. Angeli , Fotis G. Pilitsis , Angeliki A. Lemonidou
      Steam reforming of natural gas for the production of hydrogen at low operation temperature offers significant financial and environmental advantages. However, the presence of higher hydrocarbons as minor components of natural gas can significantly affect the formation of coke and thus the effectiveness of the catalyst. In this study, the effect of the presence of C2–C3 alkanes in the feedstock on the carbon accumulation during low temperature steam reforming of methane is investigated over Ni and Rh catalysts supported on lanthanum doped ceria–zirconia mixed oxide. Both catalysts showed high resistance to coke formation and especially in the case of Rh/La/CeO2–ZrO2, the carbon accumulation detected was low even after 10h on stream in steam reforming of all mixtures of hydrocarbons tested. The presence of higher alkanes in methane increased the amount of carbon on Ni(10)CeZrLa compared to pure methane as well as the nature of the carbonaceous species. Increase in the C-number of the additive alkane had almost no influence on the total amount of carbon formed (C/H feed ratio=constant) but favored the formation of filamentous carbon.
      Graphical abstract image

      PubDate: 2014-12-06T08:31:50Z
       
  • Ni0.05Mn0.95O catalysts for the dry reforming of methane
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Patrick Littlewood , Xiao Xie , Michael Bernicke , Arne Thomas , Reinhard Schomäcker
      The behaviour of nickel manganese catalysts Ni0.05Mn0.95O for the dry (carbon dioxide) reforming of methane was investigated from 500 to 800°C. Prepared catalysts showed ex-solution nickel nanoparticles on the manganese surface, which sintered during reaction, deactivating the catalyst. By pre-sintering the catalyst at 750°C in an inert atmosphere, deactivation from sintering and carbon deposition was avoided at temperatures below 800°C. The resistance of the sintered catalyst against carbon deposition was assumed to be caused by SMSI effects. After dispersing the Ni0.05Mn0.95O catalyst on silica, the catalyst exhibits a leap in activity at 600°C followed by slow deactivation, attributed to a spontaneous phase change to Ni/Mn2SiO4.
      Graphical abstract image

      PubDate: 2014-12-06T08:31:50Z
       
  • Redox dynamics of Ni catalysts in CO2 reforming of methane
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Katharina Mette , Stefanie Kühl , Andrey Tarasov , Hendrik Düdder , Kevin Kähler , Martin Muhler , Robert Schlögl , Malte Behrens
      The influence of redox dynamics of a Ni/MgAl oxide catalyst for dry reforming of methane (DRM) at high temperature was studied to correlate structural stability with catalytic activity and coking propensity. Structural aging of the catalyst was simulated by repeated temperature-programmed reduction/oxidation (TPR/TPO) cycles. Despite a very high Ni loading of 55.4wt.%, small Ni nanoparticles of 11nm were obtained from a hydrotalcite-like precursor with a homogeneous distribution. Redox cycling gradually changed the interaction of the active Ni phase with the oxide support resulting in a crystalline Ni/MgAl2O4-type catalyst. After cycling the average particle size increased from 11 to 21nm – while still a large fraction of small particles was present – bringing about a decrease in Ni surface area of 72%. Interestingly, the redox dynamics and its strong structural and chemical consequences were found to have only a moderate influence on the activity in DRM at 900°C, but lead to a stable attenuation of carbon formation due to a lower fraction of graphitic carbon after DRM in a fixed-bed reactor. Supplementary DRM experiments in a thermobalance revealed that coke formation as a continuous process until a carbon limit is reached and confirmed a higher coking rate for the cycled catalyst.
      Graphical abstract image

      PubDate: 2014-12-06T08:31:50Z
       
  • Contents list
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A




      PubDate: 2014-12-06T08:31:50Z
       
  • Preface
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Daniel Duprez , Fábio Bellot Noronha , Angelos M. Efstathiou , Narcis Homs , Claude Mirodatos



      PubDate: 2014-12-06T08:31:50Z
       
  • Recent developments in heterogeneous catalysis for the sustainable
           production of biodiesel
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A
      Author(s): Adam F. Lee , Karen Wilson
      The quest for energy security and widespread acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change from combusting fossil derived carbon sources, is driving academic and commercial research into new routes to sustainable fuels to meet the demands of a rapidly rising global population. Biodiesel is one of the most readily implemented and low cost, alternative source of transportation fuels to meet future societal demands. However, current practises to produce biodiesel via transesterification employing homogeneous acids and bases result in costly fuel purification processes and undesired pollution. Life-cycle calculations on biodiesel synthesis from soybean feedstock show that the single most energy intensive step is the catalytic conversion of TAGs into biodiesel, accounting for 87% of the total primary energy input, which largely arises from the quench and separation steps. The development of solid acid and base catalysts that respectively remove undesired free fatty acid (FFA) impurities, and transform naturally occurring triglycerides found within plant oils into clean biodiesel would be desirable to improve process efficiency. However, the microporous nature of many conventional catalysts limits their ability to convert bulky and viscous feeds typical of plant or algal oils. Here we describe how improved catalyst performance, and overall process efficiency can result from a combination of new synthetic materials based upon templated solid acids and bases with hierarchical structures, tailored surface properties and use of intensified process allowing continuous operation.
      Graphical abstract image

      PubDate: 2014-12-06T08:31:50Z
       
  • IFC - Editorial Board
    • Abstract: Publication date: 15 March 2015
      Source:Catalysis Today, Volume 242, Part A




      PubDate: 2014-12-06T08:31:50Z
       
 
 
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