Abstract: The differences between the hierarchical zeolite ZSM-5 and the conventional zeolite ZSM-5 were studied, and its application effect in propylene additives was investigated. The research results showed that the hierarchical zeolite MZSM-5 had more secondary pores and high mesoporosity, which was beneficial to the diffusion and cracking of macromolecules. Compared with MP-0 which used the conventional zeolite ZSM-5 as active component, MP-1 with hierarchical zeolite MZSM-5 was used as active component, the yield of LPG was higher, the yield of diesel oil and slurry oil were lower, and propylene yields and propylene content in LPG were higher under the same conversion. The addition of MP-1 additive could convert some olefins and isoparaffins of gasoline into propylene, and some diesel into gasoline components, thus slowing down the decline of gasoline yield and improving propylene selectivity. The results of industrial application showed that the yield of LPG and the volume fraction of propylene in LPG increased by 1.38 percentage points and 1.48 percentage points,respectively,when the additive proportion was only 2% of the system storage. Compared with that when no additive was added, product distribution had improved significantly.

Key words: catalytic cracking, hierarchical ZSM-5, liquefied petroleum gas, propylene, additive