纳米棒插接形貌ZSM-11基多级孔分子筛材料的催化裂解性能研究

STUDIES ON CATALYTIC ACTIVITY OF HIERARCHICAL ZSM-11 WITH INTERGROWTH MORPHOLOGY

以具有纳米棒插接形貌的ZSM-11基多级孔分子筛材料为活性组分制备催化裂解催化剂,采用XRD、SEM、低温N2物理吸附、NH3-TPD以及吡啶-IR方法对所制备的不同硅铝比以及不同晶粒尺寸ZSM-11分子筛进行表征,考察硅铝比及晶粒尺寸对ZSM-11分子筛催化剂裂解活性的影响,并与以ZSM-5分子筛为活性组分的常规裂解催化剂进行对比。结果表明:ZSM-11分子筛具有纯的晶相、纳米棒(晶)插接的形貌特征和微-介复合的多级孔结构;作为裂解催化剂,ZSM-11分子筛比ZSM-5分子筛具有更强的重油转化能力和更高的轻质油收率,液化气收率虽有明显下降,但是却保持着很高的对低碳烯烃(C3=、C4=)的选择性,说明ZSM-11分子筛具有更好的对高附加值产品(低碳烯烃和轻质油)的选择性;硅铝比为50时,分子筛催化剂表现出最优的裂解活性和选择性。此外,当分子筛晶粒尺寸减小后,重油转化能力进一步增强,轻质油收率提高,但是对低碳烯烃的选择性有所下降。

Hierarchical ZSM-11 zeolites with different SiO2/Al2O3 ratio and different crystal size were used as active components of cracking catalysts and compared with commercial cracking catalysts （ZSM-5 as an active component）.These active components were characterized by means of XRD,SEM,N2 adsorption,NH3-TPD and FT-IR.The results indicate that ZSM-11 zeolites possess pure crystal phase with high crystallinity,special intergrowth morphology as well as hierarchical pore structure.When tested in a micro fixed-bed reactor using Fushun vacuum gas oil （VGO） as a feedstock,catalysts based on ZSM-11 exhibit both better conversion ability for heavy oil and higher selectivity to high-value products （C3=＋C4=and light fractions） than ZSM-5 catalyst.Particularly,the ZSM-11 sample with SiO2/Al2O3 ratio of 50 shows the superior performance than the other samples.In addition,as the crystal size decreases to 200 nm,the catalyst presents both enhanced conversion ability and selectivity to light oil but lower selectivity to light olefins.