Surface properties of cobalt intermetallic compounds and their application to catalytic reactions.

用纯金属熔融法制备了Co-Ge、Co-Al和Co-Sn3种金属间化合物(IMC)，然后在空气中粉碎制得粉末催化剂。在873K下氢气还原后的X射线光电子能谱显示表面原子完全还原为零价态。在CO吸附的TPD谱中，Co-Ge IMC与纯Co金属的脱附峰不同。对H_2-D_2平衡的催化活性为：Co COGE&GT；煤炭&GT；CoGe_2&GT；CoSnGe。乙炔在这些IMC上加氢生成乙烷，而Co IMC几乎完全生成乙烯。这些IMC对乙烯加氢的活性远低于对乙炔加氢的活性，因此对乙炔的部分加氢具有独特的选择性。在Co-Ge IMC上，乙炔或乙烯的存在会大大延缓H_2-D_2的平衡，而与Ge或Sn形成IMC会降低铂或镍对氢分解的催化活性。1，3-丁二烯在铂-锗和镍-锡IMC上加氢得到了高选择性的丁烯异构体，而丁烷很容易在纯的铂或镍上生成。这些结果表明，高活性的过渡元素和相对不活跃的典型元素之间形成了IMC，从而使催化剂具有较高的部分加氢选择性。

Co-Ge, Co-Al and Co-Sn intermetallic compounds (IMC) were prepared by melting the mixture of pure metals and then they were crushed in air to obtain powder catalysts. XRD patterns showed the formation of aimed IMC.XPS spectra taken after H_2 reduction at 873 K revealed the complete reduction of surface atoms into zero valence state. In TPD spectra of adsorbed CO,Co-Ge IMC gave different desorption peak from pure Co metal. Catalytic activity for H_2-D_2 equilibration was found to be Co CoGe>CoAl>CoGe_2>CoSn Ge.Hydrogenation of acetylene was carried out on these IMC.Co metal hydrogenated acetylene into ethane, while Co IMC gave almost exclusively ethylene. Activity of these IMC for ethylene hydrogenation was much lower than that for acetylene hydrogenation, resulting in the unique selectivity for the partial hydrogenation of acetylene. H_2-D_2 equilibration was greatly retarded by the presence of acetylene or ethylene on Co-Ge IMC.The catalytic activity of Pt or Ni for hydrogen dissociation was decreased by forming IMC with Ge or Sn, respectively. Hydrogenation of 1,3-butadiene on Pt-Ge and Ni-Sn IMC gave butene isomers with high selectivity, while butane was readily produced on pure Pt or Ni. These results indicate that the formation of IMC between highly active transition element and relatively inactive typical element leads to the catalyst having high selectivity for the partial hydrogenation.