中孔分子筛HMS负载钴催化剂在费-托合成中的应用——载体HMS的孔径对钴基催化剂性能的影响

Application of Mesoporous HMS Molecular Sieve-Supported Cobalt Catalyst to Fischer-Tropsch Synthesis

用不同链长度的十二胺 ,十四胺 ,十六胺和十八胺等伯胺为模板剂合成了具有不同孔径大小的HMS中孔分子筛 .XRD和低温氮吸附测定表明 ,HMS具有典型的中孔分子筛特征 ,且其孔径大小随HMS合成中所用模板剂链长度的增加而增加 .以HMS为载体 ,采用孔体积浸渍法制备了负载量为 7 5 %的钴催化剂 ,在接近工业试验条件下 (n(H2 ) /n(CO) =2 1,GHSV =5 0 0h-1,p =2 0MPa ,θ =2 2 7℃ )考察了载体孔径大小对费 托合成反应性能的影响 .结果表明 ,与常规的SiO2 载体相比 ,HMS负载钴催化剂具有更高的催化活性和C5+ 选择性 ;而且 ,CO转化率 ,C5+ 选择性及产物中的蜡油比均随着HMS载体孔径的增大而升高 .以 7 5 %Co/HMS 18为催化剂 ,CO转化率为 78 0 % ,C5+ 选择性为 80 8% ,蜡油比为 11

Mesoporous HMS molecular sieve samples with different pore size were synthesized by using dodecylamine, tetradecylamine, cetylamine and octodecylamine as template agents. The results of XRD and N-2 adsorption at -196 degreesC indicated that all the HMS samples possess typical mesoporous channel, and also, their pore size increases with increasing the chain length of template agents. The HMS-supported cobalt catalyst samples with 7.5% loading were prepared by pore volume impregnation of the calcined HMS with an aqueous solution of Co-(NO3)(2).6H(2)O. The effect of pore size on catalytic performance of the catalyst in F-T synthesis was investigated in the conditions of industrial practice (n(H-2)/n(CO) = 2.1, GHSV = 500 h(1), p = 2.0 MPa, theta = 227 degreesC). Higher CO conversion, C5+ selectivity, and m (wax)/m (oil) were obtained when cobalt was supported on HMS than on SiO2. The uniform mesopore characteristics of HMS and the higher dispersion of Co on HMS favor to enhance CO conversion and C5+ selectivity. Also, CO conversion, C5+ selectivity, Find m(wax)/m (oil) increase with the increase of HMS pore size. Among the supports, HMS-18 with pore size of 3.69 nm showed highest selectivity for C5+ hydrocarbons and highest yield of wax.