SiO2负载钴系催化剂的环己烯环氧化性能

采用沉积沉淀法制备不同负载量的SiO₂（硅胶）负载钴氧化物催化剂，采用X射线衍射（XRD）、X射线光电子能谱（XPS）、透射电镜（TEM）、N₂吸脱附等手段对催化剂进行表征，结果表明钴系氧化物为Co₃O₄，并且钴氧化物均匀地负载在SiO₂（硅胶）载体上，其活性组分的粒子大小集中分布在2～10nm。将制备的催化剂应用于环己烯环氧化反应，以环己烯、分子氧为原料，异丁醛为催化助剂，N,N-二甲基甲酰胺（DMF）为反应溶剂，在高压釜中进行。同时将SiO₂负载钴氧化物催化剂与不同载体上制备的钴系催化剂进行比较，发现催化剂用量0.20g、环己烯2.00g、异丁醛3.50g、反应温度50℃、反应时间5h、氧气压力4MPa时，环己烯的转化率和环氧环己烷的选择性分别可达到66.56%和71.03%。

Epoxidation of cyclohexene over SiO2 supported cobalt catalyst

SiO₂ （silica gel) supported cobalt oxide catalysts with different loadings were prepared by sedimentation precipitation method. The catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), N₂ adsorption and desorption. The results showed that the cobalt-based oxide was Co₃O₄, and the cobalt oxide was uniformly distributed on the SiO₂ support. The particle size of most active component was between 2－10nm. The prepared catalyst is then used for the epoxidation of cyclohexene with cyclohexene and molecular oxygen as raw materials, isobutyraldehyde as catalytic auxiliary, and N,N-dimethylformamide (DMF) as reaction solvent . The reaction was carried out in an autoclave and the performance of the Co₃O₄/SiO₂ catalyst was compared with that of the cobalt catalysts supported on two different supports(ZrO₂ or Al₂O₃). The conversion of cyclohexene and the selectivity reached 66.56% and 71.03% under the experimental conditions of 0.20g 3% Co₃O₄/SiO₂, cyclohexene 2g, 50℃ and 4MPa.