晶化时间对ZSM-5分子筛物化性质及催化性能的影响

Effect of Crystallization Time on Physicochemical and Catalytic Properties of ZSM-5 Zeolite

考察了ZSM 5分子筛在晶化过程中的变化规律及其在苯与乙烯气相烷基化制乙苯反应中的催化性能 .结果表明 ,当晶化时间为 70h时 ,分子筛晶体开始出现 ;晶化 90h时无定形物相基本消失 .晶化时间从 90h再延长至15 0h ,ZSM 5分子筛晶粒的大小、形貌和体相硅铝比都基本不变 ,但分子筛表面的硅铝比逐渐降低 .以晶化时间为 90h的ZSM 5分子筛原粉为活性组元制备的催化剂 。

The effect of crystallization time on physicochemical properties of ZSM-5 zeolite and its catalytic performance in vapor-phase alkylation of benzene and ethylene were investigated. It was found that the first ZSM-5 crystal formed after 70 h and the amorphous phase almost disappeared after 90 h. When the crystallization time was varied from 90 to 150 h, the crystal shape, the average diameter and the SiO2/Al2O3 molar ratio in bulk of ZSM-5 zeolite remained unchanged. However, the SiO2/Al2O3 molar ratio at the external surface of the zeolite decreased with the crystallization time. The catalyst crystallized for 90 h showed the best catalytic performance in the vapor-phase alkylation of benzene and ethylene to ethylbenzene.