Combination alkylation-etherification process

A combination energy efficient process for producing high quality and gasoline blending components which comprises the steps of

• (a) contacting a mixture of methanol and an olefinic C.sub.4 cut comprising isobutene, isobutane and at least one normal butene under isobutene etherification conditions to produce methyl tertiarybutyl ether (MTBE) and unreacted C.sub.4 olefinic hydrocarbons,
• (b) passing the reaction effluent from step (a) to a fractionation zone operated under conditions to recover an overhead stream comprising normal butenes and some methanol, and a bottom stream comprising MTBE and methanol,
• (c) contacting at least a portion of said overhead stream in step (b) with isoparaffin and an acid alkylation catalyst under alkylation conditions in a alkylation zone to produce a hydrocarbon fraction comprising alkylate, normal butane, isobutane, and propane and lighter materials,
• (d) passing the hydrocarbon reaction effluent from alkylation in step (c) to a fractionation zone operated under conditions sufficient to recover an overhead stream comprising propane and lighter hydrocarbons, a first intermediate vaporous stream comprising isobutane, a second intermediate vaporous stream comprising normal butane, and a bottom stream comprising substantially liquid alkylate product,
• (e) passing said bottom stream in step (d) directly without substantial cooling to indirect heat exchange through boiling zone in a lower portion of said fractionation zone in step (b) as a source of reboiler heat for said fractionation zone, and
• (f) passing said intermediate vaporous stream comprising isobutane in step (d) through an intermediate heat exchange zone positioned in said fractionation zone in step (b) to condense said isobutane and release heat as an additional source of heat for said fractionation zone.