Abstract: ACE (Advanced Catalyst Evaluation) was employed to investigate the factors impacting the selectivities of propylene and butene in the process of catalytic cracking of heavy oil. The results showed that with the increase of temperature, there were maximum values for the selectivities of propylene and butene. But the corresponding reaction temperature for maximum butene selectivity was lower than that of propylene; with the increase of cat-to-oil ratio, selectivities of both propylene and butene decreased. However, the selectivity for butene dropped more than that of propylene; the increase of ZSM-5 zeolite was in favor of propylene, while selectivity of butene decreased. Moreover, modification ways of ZSM-5 had an impact on the selectivities of the both light olefins; with the increase of the molecular sieve cell constant of Y zeolite, the selectivities of the two olefins were decreased and the selectivity of butene decreased more than that of propylene.

Key words: FCC, propylene, butene, selectivity