中孔分子筛负载钴催化剂的制备及在费托合成中的催化性能

Preparation of Cobalt Catalysts Supported on Mesoporous Molecular Sieves and Their Catalytic Performance for F-T Synthesis

以HMS ,MCM 41,AlHMS和ZrO2 /HMS等中孔分子筛为载体 ,采用孔体积浸渍法制备了系列负载型钴催化剂 .XRD测定结果表明 ,Co氧化物完全分散于分子筛内表面 ,载体仍保持中孔分子筛的特征 ;低温N2 吸附测定结果表明 ,表面负载金属钴后 ,分子筛的比表面积和孔体积下降 ,孔径减小 ,孔壁增厚 .比较了不同中孔分子筛负载Co催化剂在F T反应中的催化性能 ,以短程六角对称的HMS为载体 ,有利于F T反应中的链增长 ,烃类产物主要为微晶蜡 ;以ZrO2 /HMS为载体可抑制CH4 的生成 ,提高C5+ 的选择性 .

HMS, MCM 41, AlHMS, and ZrO 2/HMS etc mesoporous molecular sieves were used as supports and a sires of supported cobalt catalysts for F T synthesis were prepared by pore volume impregnation using solutions of cobalt and manganese nitrates. After drying and calcination, Co oxide was dispersed completely on the support and the support still retained mesoporous characteristics. However, after cobalt was supported on these mesoporous materials, their BET surface area, pore volume, and pore size decreased, and the pore wall thickness increased. The catalytic performance of the catalysts in the F T synthesis was determined. The catalyst Co/HMS showed the highest catalytic activity and the highest C 5+ selectivity. The best catalytic performance of Co/HMS is due to that the support HMS has shorter hexagonal order, smaller domain size with shorter channel, and larger textural mesoporosity than those of other supports. Higher hydrocarbons (wax) were obtained in the F T synthesis over Co/HMS catalyst. ZrO 2 supported on HMS could prevent from producing CH 4. In a typical F T synthesis, when 15%Co 2%Mn/HMS was used as a catalyst, CO conversion was 92.5%, in the products, w(CH 4) and w(C 5+ ) were 9 2% and 86 3%, respectively, and the wax yield was 36 2% with w(wax)/w(oil)=8 0