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Jose A Rodriguez - One of the best experts on this subject based on the ideXlab platform.
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The Carburization of Transition Metal Molybdates (M_xMoO_4, M = Cu, Ni or Co) and the Generation of Highly Active Metal/Carbide Catalysts for CO_2 Hydrogenation
Catalysis Letters, 2015Co-Authors: Pedro J Ramirez, Joaquin L Brito, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo_2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu_3(MoO_4)_2(OH)_2, α-NiMoO_4 and CoMoO_4· n H_2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo_2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu^2+, Ni^2+ and Co^2+ cations inside each molybdate. The synthesized Cu/Mo_2C, Ni/Mo_2C and Co/Mo_2C catalysts were highly active for the hydrogenation of CO_2. The metal/Mo_2C systems exhibited large variations in the selectivity towards methanol, methane and C_nH_2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo_2C displayed a high selectivity for CO and methanol production. Ni/Mo_2C and Co/Mo_2C were the most active catalysts for the activation and full decomposition of CO_2, showing high selectivity for the production of methane (Ni case) and C_nH_2n+2 (n > 2) hydrocarbons (Co case). Graphical Abstract
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the carburization of transition metal Molybdates mxmoo4 m cu ni or co and the generation of highly active metal carbide catalysts for co2 hydrogenation
Catalysis Letters, 2015Co-Authors: Joaquin L Brito, Pedro J Ramirez, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu3(MoO4)2(OH)2, α-NiMoO4 and CoMoO4·nH2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu2+, Ni2+ and Co2+ cations inside each molybdate. The synthesized Cu/Mo2C, Ni/Mo2C and Co/Mo2C catalysts were highly active for the hydrogenation of CO2. The metal/Mo2C systems exhibited large variations in the selectivity towards methanol, methane and CnH2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo2C displayed a high selectivity for CO and methanol production. Ni/Mo2C and Co/Mo2C were the most active catalysts for the activation and full decomposition of CO2, showing high selectivity for the production of methane (Ni case) and CnH2n+2 (n > 2) hydrocarbons (Co case).
Pedro J Ramirez - One of the best experts on this subject based on the ideXlab platform.
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The Carburization of Transition Metal Molybdates (M_xMoO_4, M = Cu, Ni or Co) and the Generation of Highly Active Metal/Carbide Catalysts for CO_2 Hydrogenation
Catalysis Letters, 2015Co-Authors: Pedro J Ramirez, Joaquin L Brito, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo_2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu_3(MoO_4)_2(OH)_2, α-NiMoO_4 and CoMoO_4· n H_2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo_2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu^2+, Ni^2+ and Co^2+ cations inside each molybdate. The synthesized Cu/Mo_2C, Ni/Mo_2C and Co/Mo_2C catalysts were highly active for the hydrogenation of CO_2. The metal/Mo_2C systems exhibited large variations in the selectivity towards methanol, methane and C_nH_2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo_2C displayed a high selectivity for CO and methanol production. Ni/Mo_2C and Co/Mo_2C were the most active catalysts for the activation and full decomposition of CO_2, showing high selectivity for the production of methane (Ni case) and C_nH_2n+2 (n > 2) hydrocarbons (Co case). Graphical Abstract
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the carburization of transition metal Molybdates mxmoo4 m cu ni or co and the generation of highly active metal carbide catalysts for co2 hydrogenation
Catalysis Letters, 2015Co-Authors: Joaquin L Brito, Pedro J Ramirez, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu3(MoO4)2(OH)2, α-NiMoO4 and CoMoO4·nH2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu2+, Ni2+ and Co2+ cations inside each molybdate. The synthesized Cu/Mo2C, Ni/Mo2C and Co/Mo2C catalysts were highly active for the hydrogenation of CO2. The metal/Mo2C systems exhibited large variations in the selectivity towards methanol, methane and CnH2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo2C displayed a high selectivity for CO and methanol production. Ni/Mo2C and Co/Mo2C were the most active catalysts for the activation and full decomposition of CO2, showing high selectivity for the production of methane (Ni case) and CnH2n+2 (n > 2) hydrocarbons (Co case).
Joaquin L Brito - One of the best experts on this subject based on the ideXlab platform.
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The Carburization of Transition Metal Molybdates (M_xMoO_4, M = Cu, Ni or Co) and the Generation of Highly Active Metal/Carbide Catalysts for CO_2 Hydrogenation
Catalysis Letters, 2015Co-Authors: Pedro J Ramirez, Joaquin L Brito, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo_2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu_3(MoO_4)_2(OH)_2, α-NiMoO_4 and CoMoO_4· n H_2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo_2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu^2+, Ni^2+ and Co^2+ cations inside each molybdate. The synthesized Cu/Mo_2C, Ni/Mo_2C and Co/Mo_2C catalysts were highly active for the hydrogenation of CO_2. The metal/Mo_2C systems exhibited large variations in the selectivity towards methanol, methane and C_nH_2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo_2C displayed a high selectivity for CO and methanol production. Ni/Mo_2C and Co/Mo_2C were the most active catalysts for the activation and full decomposition of CO_2, showing high selectivity for the production of methane (Ni case) and C_nH_2n+2 (n > 2) hydrocarbons (Co case). Graphical Abstract
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the carburization of transition metal Molybdates mxmoo4 m cu ni or co and the generation of highly active metal carbide catalysts for co2 hydrogenation
Catalysis Letters, 2015Co-Authors: Joaquin L Brito, Pedro J Ramirez, Dario Stacchiola, Jose A RodriguezAbstract:A new approach has been tested for the preparation of metal/Mo2C catalysts using mixed-metal oxide Molybdates as precursors. Synchrotron-based in situ time-resolved X-ray diffraction was used to study the reduction and carburization processes of Cu3(MoO4)2(OH)2, α-NiMoO4 and CoMoO4·nH2O by thermal treatment under mixtures of hydrogen and methane. In all cases, the final product was β-Mo2C and a metal phase (Cu, Ni, or Co), but the transition sequence varied with the different metals, and it could be related to the reduction potential of the Cu2+, Ni2+ and Co2+ cations inside each molybdate. The synthesized Cu/Mo2C, Ni/Mo2C and Co/Mo2C catalysts were highly active for the hydrogenation of CO2. The metal/Mo2C systems exhibited large variations in the selectivity towards methanol, methane and CnH2n+2 (n > 2) hydrocarbons depending on the nature of the supported metal and its ability to cleave C–O bonds. Cu/Mo2C displayed a high selectivity for CO and methanol production. Ni/Mo2C and Co/Mo2C were the most active catalysts for the activation and full decomposition of CO2, showing high selectivity for the production of methane (Ni case) and CnH2n+2 (n > 2) hydrocarbons (Co case).
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effect of phase composition of the oxidic precursor on the hds activity of the sulfided Molybdates of fe ii co ii and ni ii
Journal of Catalysis, 1997Co-Authors: Joaquin L Brito, Liliana A BarbosaAbstract:The catalytic HDS activities of unsupported sulfided Molybdates of Fe(II), Co(II), and Ni(II) have been examined measuring the conversion of thiophene at 400°C under atmospheric pressure. The oxidic precursors employed included the hydratesAMoO4·H2O and the α- and β-AMoO4polymorphs (A=Fe, Co, or Ni). The previous finding that sulfided β-NiMoO4is a better HDS catalyst than α-NiMoO4is now generalized to the other two molybdate systems, suggesting that the tetrahedral environment of Mo in the β-isomorphs provides a more activeA–Mo–S phase than the octahedral one in the α-Molybdates. The reduced (nonpresulfided) molybdate samples showed lower HDS activities than those sulfided in pure H2S. Prereduction followed by sulfiding seems to be an optimum procedure for the highest HDS activity of the nickel Molybdates and also of β-FeMoO4. It was found that NiMoO4·H2O renders a more active sulfided catalyst than the β-phase synthesized by calcination at 760°C, and this seems to be related to thein situgeneration of β-NiMoO4with higher surface area during the activation of the hydrate at 400°C. The hydrated phase of cobalt behaved similarly, but that of iron, on the contrary, was a poorer catalytic precursor than β-FeMoO4. It is suggested that decomposition of the hydrated compound in the case of Fe could generate a more crystalline material upon sulfiding due to the possibility of changes in the oxidation state of the metals (i.e., Fe2+ ⇄ Fe3+, Mo6+ ⇄ Mo5+) during thermal transformations in presence of evolved water.
Evgeny V Alekseev - One of the best experts on this subject based on the ideXlab platform.
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high temperature phase transitions spectroscopic properties and dimensionality reduction in rubidium thorium molybdate family
Inorganic Chemistry, 2014Co-Authors: Bin Xiao, Evgeny V Suleimanov, Thorsten M Gesing, Philip Kegler, Giuseppe Modolo, Dirk Bosbach, Hartmut Schlenz, Evgeny V AlekseevAbstract:Four new rubidium thorium Molybdates have been synthesized by high-temperature solid-state reactions. The crystal structures of Rb8Th(MoO4)6 ,R b 2Th(MoO4)3, Rb4Th(MoO4)4, and Rb4Th5(MoO4)12 were determined using single-crystal X-ray diffraction. All these compounds construct from MoO4 tetrahedra and ThO8 square antiprisms. The studied compounds adopt the whole range of possible structure dimensionalities from zero-dimensional (0D) to three-dimensional (3D): finite clusters, chains, sheets, and frameworks. Rb8Th(MoO4)6 crystallizes in 0D containing clusters of (Th(MoO4)6) 8− . The crystal structure of Rb2Th(MoO4)3 is based upon one-dimensional chains with configuration units of (Th(MoO4)3) 2− . Two-dimensional sheets occur in compound Rb4Th(MoO4)4, and a 3D framework with channels formed by thorium and molybdate polyhedra has been observed in Rb4Th5(MoO4)12. The Raman and IR spectroscopic properties of these compounds are reported. Temperature-depended phase transition effects were observed in Rb2Th(MoO4)3 and Rb4Th(MoO4)4 using thermogravimetry-differential scanning calorimetry analysis and high-temperature powder diffraction methods.
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dimensional reduction in alkali metal uranyl Molybdates synthesis and structure of cs2 uo2 o moo4
Zeitschrift für anorganische und allgemeine Chemie, 2007Co-Authors: Evgeny V Alekseev, Sergey V Krivovichev, Thomas Armbruster, Wulf Depmeier, Evgeny V Suleimanov, Evgeny V Chuprunov, Alexei V GolubevAbstract:A new uranyl molybdate, Cs-2[(UO2)O(MoO4)] (1), has been prepared by high-temperature solid-state reactions. The structure has been solved by direct methods and refined to R-1 = 0.0284 for vertical bar F-0 vertical bar >= 4 sigma(F) The compound 1 is orthorhombic, Pca2(1), a = 12.018(2), b = 12.438(2), c = 17.917(3) angstrom, V = 2678.2(7) angstrom(3), Z = 12. The structure of 1 is based upon one-dimensional chains consisting of corner-sharing UO6 and MoO4 polyhedra. The UO6 square bipyramids share cis equatorial vertices to form zigzag chains that are further stabilized by bidendate MoO4 tetrahedra. The chains have composition [(UO2)O(MoO4)](2-) and are oriented parallel to the c axis. In the structure, adjacent chains form pseudo-2D-layers parallel to (010). The Cs+ cations are in between the pseudolayers. The composition -structure relationships in alkali metal uranyl Molybdates can be rationalized from the viewpoint of dimensional reduction using the following assumptions: (1) representation of the A(x)U(n)Mo(m)O(y) formula (n <= m) as a sum of UMoO6 (= UO2MoO4), A(2)O, and A(2)MoO(4) (A = alkali metal): A(x)U(n)Mo(m)O(y) = kA(2)O + nUMoO(6) + (m-n)A(2)MoO(4), where x = 2(k + m - n) and y = k + 2n + 4m; (2) analysis of the dimensionality of uranyl molybdate structural units and its changes upon incorporation of ionic reagents A(2)O and A(2)MoO(4) into a parent framework Of UO2MoO4 that consists of 3-D array of U and Mo based polyhedra. The relationships between different compositions and structures may be visualized using the UO2MoO4-A(2)O-A(2)MoO(4) compositional diagram. The observed trends of decreasing dimensionality of the uranyl molybdate units allow to specify on this diagram fields of dimensionality.
Wang Xinping - One of the best experts on this subject based on the ideXlab platform.
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Oxidative Dehydrogenation of n-Butane over Metal Molybdates
Chinese Journal of Catalysis, 2004Co-Authors: Wang XinpingAbstract:Molybdates of the first-row transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) and Mg have been prepared by the citrate method and their catalytic performance for the n-butane oxidative dehydrogenation has been studied. The properties of these catalysts strongly depend on the cations of the metal Molybdates. Among the catalysts, CoMoO 4 is the most active catalyst with higher selectivity being comparable to that of ZrP 2O 7 and Mg 3V 2O 8 reported in literature. Although the MgMoO 4 catalyst is more selective for the n-butane oxidative dehydrogenation under the identical reaction conditions, it is less active than CoMoO 4. Over the Cr 2(MoO 4) 3 catalyst, the combustion reaction takes place predominantly and almost no C 4 olefins are obtained in the products. The other metal Molybdates show poor catalytic activity and selectivity. The results of XRD, NH 3-TPD and H 2-TPR indicate that each catalyst prepared by the citrate method is composed of pure molybdate crystal phase. The redox properties of the catalysts play a key role in the n-butane oxidative dehydrogenation and no relationship between the catalytic performance and the acid amount on the catalyst surface is observed. According to the product distribution, the reaction network for the oxidative dehydrogenation of n-butane over the CoMoO 4 catalyst at 558 ℃ is proposed. Under the reaction conditions, three competitive parallel reactions take place, producing butene (75%), carbon dioxide (15%) and butadiene (10%), respectively. At high n-butane conversion, carbon dioxide results mainly from re-oxidation of C 4 olefins, while CO is entirely produced from the deep oxidation of C 4 olefins.
