Process for producing high octane gasoline and particularly lead-free gasoline

A process for producing a blended high octane gasoline, which comprises the steps of:

• (a) oligomerizing an olefinic C.sub.3 hydrocarbon cut comprising propylene, and recovering an oligomerizate boiling in the gasoline range;
• (b) hydroisomerizing an olefinic C.sub.4 hydrocarbon cut comprising isobutene, isobutane, 1-butene and 2-butene under 1-butene isomerizing conditions, and recovering an isomerized C.sub.4 cut having an increased proportion of 2-butene and a decreased proportion of 1-butene relative to said olefinic C.sub.4 hydrocarbon cut;
• (c) fractionating the isomerized C.sub.4 cut from step (b) and separately recovering a first fraction having an increased proportion of isobutene and isobutane relative to said isomerized C.sub.4 cut, and a second fraction having an increased proportion of 2-butene relative to said isomerized C.sub.4 cut;
• (d) hydrogenating said first fraction from step (c) under isobutene hydrogenating conditions, and recovering an effluent having an increased proportion of isobutane relative to said first fraction;
• (e) admixing the effluent from step (d) and said second fraction from step (c), subjecting the resultant mixture to hydrocarbon alkylation conditions, and recovering an alkylate boiling in the gasoline range;
• and
• (f) blending at least a portion of the oligomerizate from step (a) with at least a portion of the alkylate from step (e) to produce a blended high octane gasoline.