干胶法合成多级孔ZSM-5分子筛及其正辛烷催化裂解反应性能

采用干胶转化法制备多级孔ZSM-5分子筛,利用XRD、N_2吸附-脱附、SEM、TEM和NH_3-TPD等考察添加三嵌段共聚物(P123)、十六烷基三甲基溴化铵(CTAB)、十二烷基硫酸钠(SDS)和聚乙烯吡咯烷酮(PVP)等不同软模板剂合成分子筛样品的物化性质。结果表明,利用P123软模板剂合成的多级孔ZSM-5分子筛具有介孔(2.5 nm)-介孔(9.5 nm)-微孔复合的梯级孔结构,且分子筛酸强度有所增强。多级孔ZSM-5分子筛应用于正辛烷催化裂解反应中,具有较高的催化活性和低碳烯烃收率,其优异的催化性能可能归结于强酸性质和优异扩散传质能力之间的协同作用。

Synthesis of hierarchical ZSM-5 zeolites by dry-gel conversion method and their catalytic performances for cracking of n-octane

Hierarchical ZSM-5 zeolites were prepared by dry-gel conversion method.XRD,N₂ adsorption-desorption,SEM,TEM and NH₃-TPD were used to investigate the physicochemical properties of the samples synthesized by using different soft templating agents such as triblock copolymer(P123),cetyltrimethylammonium bromide(CTAB),dodecyl sulfate(SDS) and polyvinylpyrrolidone(PVP).The results showed that the ZSM-5 zeolites prepared by addition of P123 possessed mesopores(2.5 nm)-mesopores(9.5 nm)-micropores hierarchical structure and strong acid properties.In catalytic cracking of n-octane,the hierarchical ZSM-5 zeolites exhibited high catalytic activity and light olefines yield,which might be attributed to the synergy effect of strong acid sites and enhanced diffusion mass transfer capacity.