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Alloy Catalyst

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Hexing Li – 1st expert on this subject based on the ideXlab platform

  • highly active co b amorphous Alloy Catalyst with uniform nanoparticles prepared in oil in water microemulsion
    Journal of Catalysis, 2008
    Co-Authors: Hui Li, Ming-hua Qiao, Hexing Li

    Abstract:

    Abstract Uniform Co–B nanoparticles were synthesized for the first time by chemical reduction of cobalt ion with borohydride in an oil-in-water microemulsion system comprising cyclohexane, polyethylene glycol, and water. The particle size was controlled by modulating the cyclohexane content. With the characterization of X-ray diffraction, selective area electronic diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, the resulting Co–B nanoparticles were identified to be amorphous Alloys ranging in size from 6 to 20 nm. During liquid-phase cinnamaldehyde hydrogenation, the as-synthesized Co–B Catalyst was extremely active and more selective than the regular Co–B prepared in aqueous solution. Furthermore, this Catalyst also was found to be more durable during the hydrogenation process.

  • ultrasound assisted preparation of a highly active and selective co b amorphous Alloy Catalyst in uniform spherical nanoparticles
    Journal of Catalysis, 2007
    Co-Authors: Hexing Li, Hui Li, Jing Zhang, Ming-hua Qiao

    Abstract:

    Abstract Uniform spherical Co-B amorphous Alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)2+6 with BH−4 in aqueous solution, and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B Catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH−4. The higher activity can be attributed to both the higher dispersion of Co active sites ( S Co ) and the higher intrinsic activity ( R S ). The higher selectivity can be attributed to both the uniform Co-B amorphous Alloy particles and the strong electronic interaction between Co and B, which enhances the competitive adsorption of C O group against C C group in the CMA molecule. Meanwhile, the stronger adsorption for hydrogen on Co active sites was more favorable for C O hydrogenation in comparison with the C C hydrogenation.

  • liquid phase acetonitrile hydrogenation to ethylamine over a highly active and selective ni co b amorphous Alloy Catalyst
    Applied Catalysis A-general, 2004
    Co-Authors: Hexing Li, Yuedong Wu, Jing Zhang, Ming-hua Qiao

    Abstract:

    Abstract The ultrafine Ni–Co–B amorphous Alloys with Co/(Co + Ni) molar ratio ( χ Co ) varying from 0 to 1 was prepared by chemical reduction of mixed Ni 2+ and Co 2+ ions with BH 4 − in aqueous solution. During liquid phase acetonitrile hydrogenation to ethylamine, the specific activity ( R m ) and the intrinsic activity (TON) of the Ni–Co–B Catalyst first increased and then decreased with the increase of χ Co from 0 to 1. The maximum activity was obtained at χ Co = 0.5; the value of the activity was nearly twice as that of the Ni–B or the Co–B Catalyst. Treatment of the Ni–Co–B Catalyst at 873 K resulted in an abrupt decrease in the activity due both to a decrease in active surface area and, especially, to the crystallization and the decomposition of the Ni–Co–B amorphous Alloy. The selectivity to ethylamine increased rapidly with χ Co and then remained constant at χ Co ≥ 0.5. The maximum yield of ethylamine could reach 93%, showing a good potential for industrial applications. According to kinetic studies and results of various characterization methods, such as ICP, XRD, EXAFS, XPS, SAED, TEM, DSC, TPD, and hydrogen chemisorption, the correlation of the catalytic performance to both the structural and the electronic characteristics was discussed briefly. The activation of the C N and/or C N bonds, the promotion on the hydrogen adsorption, and the inhibition on the ethylamine adsorption were the decisive factors responsible for the excellent activity and selectivity of the Ni–Co–B Catalyst.

Keiichi Tomishige – 2nd expert on this subject based on the ideXlab platform

  • total hydrogenation of furfural and 5 hydroxymethylfurfural over supported pd ir Alloy Catalyst
    ACS Catalysis, 2014
    Co-Authors: Yoshinao Nakagawa, Kana Takada, Masazumi Tamura, Keiichi Tomishige

    Abstract:

    Hydrogenation of aqueous furfural was conducted with SiO2-suported palladium-based bimetallic Catalysts. The combination of palladium and iridium gave the best performance for the total hydrogenation to tetrahydrofurfuryl alcohol. Higher H2 pressure and lower reaction temperature were advantageous to suppress side reactions. The synergy between Pd and Ir in the hydrogenation catalysis is most remarkable for substituted furans as substrates. Furfural was first converted into furfuryl alcohol, which was further converted to tetrahydrofurfuryl alcohol. A small amount of tetrahydrofurfural was formed in the first step (∼20% selectivity), and the subsequent hydrogenation of tetrahydrofurfural was much slower. The combined yield of tetrahydrofurfuryl alcohol and tetrahydrofurfural reached 98%. The yield of tetrahydrofurfuryl alcohol reached 94% with larger amount of Catalyst. Total hydrogenation of 5-hydroxymethylfurfural was also possible using Pd–Ir/SiO2 Catalyst. The performance of Pd–Ir/SiO2 Catalyst was sl…

  • performance and characterization of rhenium modified rh ir Alloy Catalyst for one pot conversion of furfural into 1 5 pentanediol
    Catalysis Science & Technology, 2014
    Co-Authors: Yasushi Amada, Yoshinao Nakagawa, Masazumi Tamura, Keiichi Tomishige

    Abstract:

    One-pot selective conversion of highly concentrated furfural to 1,5-pentanediol (1,5-PeD) was carried out over Rh-added Ir–ReOx/SiO2 Catalysts through two-step reaction temperatures. Over the optimized Catalyst, Rh(0.66 wt%)–Ir–ReOx/SiO2, the maximum yield of 1,5-PeD was 71.1% from highly concentrated furfural (50 wt%) and 78.2% from diluted furfural (10 wt%). These values were higher than those obtained with Ir–ReOx/SiO2 or Pd–Ir–ReOx/SiO2 Catalysts. Rh–Ir–ReOx/SiO2 showed much higher activity in the hydrogenation of furfural to tetrahydrofurfuryl alcohol intermediate in the low temperature step than Ir–ReOx/SiO2, although the hydrogenation activity was lower than that of Pd–Ir–ReOx/SiO2. A long reaction time in the low temperature step is necessary to obtain a good 1,5-PeD yield over Rh–Ir–ReOx/SiO2 in two-step reaction of furfural. The hydrogenolysis activity of Rh–Ir–ReOx/SiO2 for tetrahydrofurfuryl alcohol to 1,5-PeD in the high temperature step was higher than that of Pd–Ir–ReOx/SiO2 and was comparable to that of Ir–ReOx/SiO2. The characterization results of TPR, XRD, XANES, EXAFS, STEM-EDX and FT-IR of adsorbed CO indicated that Rh–Ir–ReOx/SiO2 Catalysts showed the structure of Ir–Rh Alloy particles partially covered with ReOx species. The hydrogenation activity of Rh–Ir–ReOx/SiO2 for the furan ring was higher than those of the mixture of Rh–Ir/SiO2 and Ir–ReOx/SiO2 or the mixture of Rh–ReOx/SiO2 and Ir–ReOx/SiO2. Both Ir–Rh Alloy formation and ReOx modification of Alloy particles are essential for the high hydrogenation activity.

  • performance structure and mechanism of pd ag Alloy Catalyst for selective oxidation of glycerol to dihydroxyacetone
    Journal of Catalysis, 2013
    Co-Authors: Shota Hirasawa, Yoshinao Nakagawa, Hideo Watanabe, Tokushi Kizuka, Keiichi Tomishige

    Abstract:

    The mechanism of the oxidation of glycerol to dihydroxyacetone over Pd–Ag Catalysts was discussed. Characterization results suggest that the metal composition of the surface of the crystalline Pd–Ag Alloy particles is almost the same as the bulk composition. The synergetic effects of Pd and Ag appear on the oxidation of the secondary OH group of vic-diols. The reaction order with respect to glycerol concentration over Pd–Ag/C was zero, suggesting the strong interaction between glycerol and the Catalyst surface. The reaction order with respect to O2 pressure was 0.4, suggesting that the rate-determining step is the reaction involving oxygen species. These reaction trends and characterization results support the mechanism where the terminal OH group of glycerol is adsorbed on the Ag site and the neighboring secondary OH group (CH–OH) is attacked by the oxygen species dissociatively adsorbed on the Pd site.

Ming-hua Qiao – 3rd expert on this subject based on the ideXlab platform

  • highly active co b amorphous Alloy Catalyst with uniform nanoparticles prepared in oil in water microemulsion
    Journal of Catalysis, 2008
    Co-Authors: Hui Li, Ming-hua Qiao, Hexing Li

    Abstract:

    Abstract Uniform Co–B nanoparticles were synthesized for the first time by chemical reduction of cobalt ion with borohydride in an oil-in-water microemulsion system comprising cyclohexane, polyethylene glycol, and water. The particle size was controlled by modulating the cyclohexane content. With the characterization of X-ray diffraction, selective area electronic diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, the resulting Co–B nanoparticles were identified to be amorphous Alloys ranging in size from 6 to 20 nm. During liquid-phase cinnamaldehyde hydrogenation, the as-synthesized Co–B Catalyst was extremely active and more selective than the regular Co–B prepared in aqueous solution. Furthermore, this Catalyst also was found to be more durable during the hydrogenation process.

  • ultrasound assisted preparation of a highly active and selective co b amorphous Alloy Catalyst in uniform spherical nanoparticles
    Journal of Catalysis, 2007
    Co-Authors: Hexing Li, Hui Li, Jing Zhang, Ming-hua Qiao

    Abstract:

    Abstract Uniform spherical Co-B amorphous Alloy nanoparticles were prepared by ultrasound-assisted reduction of Co(NH3)2+6 with BH−4 in aqueous solution, and the particle size was adjusted by changing either the ultrasound power or the ultrasonication time. During liquid-phase cinnamaldehyde (CMA) hydrogenation, the as-prepared Co-B Catalyst exhibited much higher activity and better selectivity to cinnamyl alcohol (CMO) than the regular Co-B obtained by direct reduction of Co2+ with BH−4. The higher activity can be attributed to both the higher dispersion of Co active sites ( S Co ) and the higher intrinsic activity ( R S ). The higher selectivity can be attributed to both the uniform Co-B amorphous Alloy particles and the strong electronic interaction between Co and B, which enhances the competitive adsorption of C O group against C C group in the CMA molecule. Meanwhile, the stronger adsorption for hydrogen on Co active sites was more favorable for C O hydrogenation in comparison with the C C hydrogenation.

  • liquid phase acetonitrile hydrogenation to ethylamine over a highly active and selective ni co b amorphous Alloy Catalyst
    Applied Catalysis A-general, 2004
    Co-Authors: Hexing Li, Yuedong Wu, Jing Zhang, Ming-hua Qiao

    Abstract:

    Abstract The ultrafine Ni–Co–B amorphous Alloys with Co/(Co + Ni) molar ratio ( χ Co ) varying from 0 to 1 was prepared by chemical reduction of mixed Ni 2+ and Co 2+ ions with BH 4 − in aqueous solution. During liquid phase acetonitrile hydrogenation to ethylamine, the specific activity ( R m ) and the intrinsic activity (TON) of the Ni–Co–B Catalyst first increased and then decreased with the increase of χ Co from 0 to 1. The maximum activity was obtained at χ Co = 0.5; the value of the activity was nearly twice as that of the Ni–B or the Co–B Catalyst. Treatment of the Ni–Co–B Catalyst at 873 K resulted in an abrupt decrease in the activity due both to a decrease in active surface area and, especially, to the crystallization and the decomposition of the Ni–Co–B amorphous Alloy. The selectivity to ethylamine increased rapidly with χ Co and then remained constant at χ Co ≥ 0.5. The maximum yield of ethylamine could reach 93%, showing a good potential for industrial applications. According to kinetic studies and results of various characterization methods, such as ICP, XRD, EXAFS, XPS, SAED, TEM, DSC, TPD, and hydrogen chemisorption, the correlation of the catalytic performance to both the structural and the electronic characteristics was discussed briefly. The activation of the C N and/or C N bonds, the promotion on the hydrogen adsorption, and the inhibition on the ethylamine adsorption were the decisive factors responsible for the excellent activity and selectivity of the Ni–Co–B Catalyst.