Octane improvement of gasoline in catalytic cracking without decreasing total liquid yield

摘要

Modified ZSM-5 type zeolite catalyst is prepared by controlled aging in a moving bed catalytic cracking unit. The modified catalyst exhibits significant olefin isomerization activity and reduced paraffin cracking activity. Hydrocarbons are cracked to products boiling in the motor fuel range, e.g., gasoline, by using the modified catalyst mixture comprising a ZSM-5 type zeolite and a conventional cracking catalyst. The ZSM-5 type zeolite is treated with partial pressure steam under conditions which increase the gasoline octane number of the product fuel without decreasing gasoline plus distillate yield. A process for changing a catalytic cracking unit's inventory from a conventional catalyst to a modified ZSM-5 type containing catalyst is also disclosed.