Process for the production of alkylate gasoline from FCC light aliphatics

A process for upgrading hydrocarbon feedstock comprising the steps of:

• (a) contacting a C.sub.4 -rich aliphatic stream containing isoparaffins and linear olefins with an isomerization catalyst comprising a zeolite sorbing 30 to 55 mg n-hexane at 90.degree. C., 83 torr, and 15 to 40 mg 3-methylpentane at 90.degree. C., 90 torr, per g dry zeolite in the hydrogen form in a first reaction stage to selectively isomerize linear butenes to isobutene;
• (b) contacting the effluent from said first reaction stage containing isobutane, linear butenes, and isobutene with a solid acid alkylation catalyst selected from the group consisting of MCM-36 and MCM-49, as described herein and zeolites having a Constraint Index of less than or equal to about 2 in a second reaction stage, under conditions which selectively convert said isobutane and isobutene to isoparaffinic alkylate gasoline;
• (c) fractioning said second reaction stage effluent containing isoparaffinic alkylate gasoline, unreacted isobutane and unreacted linear butenes to obtain isoparaffinic alkylate gasoline and an overhead comprising unreacted isobutane and linear butenes;
• and
• (d) recycling said overhead to step (a) or (b).