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

采用熔融法制备了Co-Ge、Co-Al和Co-Sn金属间化合物（IMC），然后在空气中粉碎得到粉末状催化剂。X射线衍射（XRD）分析表明，在873 K下H_2还原后，样品表面原子被还原为零价态。在吸附CO的TPD谱中，Co-Ge IMC出现了与纯Co不同的脱附峰。H_2-D_2平衡催化活性为CoCoGe>CoAl>CoGe_2>CoSn Ge，乙炔加氢反应中，Co金属使乙炔加氢生成乙烷，而CoIMC几乎只生成乙烯。这些IMC的乙烯加氢活性远低于乙炔加氢活性，导致其对乙炔部分加氢具有独特的选择性。乙炔或乙烯的存在大大阻碍了H_2-D_2平衡，而Pt或Ni分别与Ge或Sn形成IMC后，对氢解离的催化活性降低。在Pt-Ge和Ni-Sn IMC上，1，3-丁二烯的加氢选择性高，生成丁烯异构体，而在纯Pt或Ni上，丁烷容易生成。这些结果表明，高活性的过渡元素和相对惰性的典型元素之间形成的IMC导致催化剂具有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.