分子筛改性Co/SiO_2催化剂对Fischer-Tropsch合成汽油类烃的影响

在中孔SiO2中添加USY,HZSM-5,β分子筛组成双功能载体,并采用初湿浸渍法在载体上浸渍钴盐,制备了一系列分子筛改性的Co/SiO2催化剂,考察了分子筛的类型、HZSM-5分子筛的骨架硅铝比、HZSM-5分子筛在载体中的含量对Fischer-Tropsch合成汽油类烃(C5~12)的影响。实验结果表明,载体中SiO2和分子筛共同作用,提高了催化剂的活性,并使产物分布向汽油类烃偏移,其中,以HZSM-5分子筛改性的Co/SiO2催化剂的催化性能最好。HZSM-5分子筛改性催化剂对催化性能的影响受其骨架硅铝比的影响。当骨架硅铝比n(SiO2)∶n(Al2O3)=38、HZSM-5分子筛在载体中的质量分数为20%时,CO转化率达到80%以上,汽油类烃的选择性高达55%,其中异构烷烃的选择性在10%以上。

Effect of Co/SiO2 Catalyst Modified by Zeolites on Fischer-Tropsch Synthesis of Gasoline-Cut Hydrocarbons

Fischer-Tropsch synthesis of gasoline hydrocarbons(C5-12)was carried out over a series of Co/SiO2 catalysts modified by zeolites. The catalysts were prepared by impregnation using three kinds of zeolites(USY,HZSM-5,β) and mesoporous SiO2 as bi-functional supports. Effects of zeolite type, n(SiO2) ∶n(Al2O3) on HZSM-5 zeolite framework and content of HZSM-5 in bi-functional support on Fischer-Tropsch catalytic synthesis were studied. The co-effect of SiO2 and zeolites enhances catalytic activity and shifts the carbon number distribution of hydrocarbons towards gasoline-cut. HZSM-5 zeolite is more effective than the other two zeolites. The performance of HZSM-5 zeolite modified catalyst is mainly affected by n(SiO2) ∶n(Al2O3) on HZSM-5 zeolite framework. When mass fraction of HZSM-5 zeolite (n(SiO2) ∶n(Al2O3)=38) in bi-supports is 20%, CO conversion is as high as 80% and selectivity to gasoline hydrocarbons is more than 55% with about 10% isoparaffins.