Hydrocarbon cracking with catalyst contg. ZSM zeolite - involves recycling gasoline and heavy cycle oil to increase propylene prodn.

摘要

Cracking of hydrocarbon feeds is effected in an FCC unit using a catalyst comprising 20-95 wt.% of a matrix material (I), 1-60 wt.% of a large-pore zeolite (II) and 0.05-40 wt.% of a ZSM-5, ZSM-11, ZSM-22 or ZSM-23 zeolite (III) with a pore size of 0.5-0.6 nm. Catalyst is injected into the bottom of the FCC riser and fresh feed is injected at a point (B) above the bottom. After sepg. the catalyst, the riser effluent is fractionated to obtain LPG, gasoline, light cycle oil (LCO) and heavy cycle oil (HCO) fractions. Gasoline is recycled and injected into the riser at a point (C) above the bottom but below B. HCO is recycled and injected at a point (A) above B. ADVANTAGE - The process gives high propylene yields without excessively increasing prodn. of 4C hydrocarbons.