Alkylate is produced by catalytically converting oxygenate feedstock, such as methanol, to lower olefins comprising dominantly C.sub.2 -C.sub.4 olefins. Ethene is separated from primary stage effluent by interstage sorption of C.sub.3 + components which may be upgraded. Isoparaffin may be alkylated with C.sub.3 -C.sub.4 olefins in a secondary stage.The improved technique comprises fractionating an olefinic feedstream containing ethene and C.sub.3 + olefinic components by contacting the olefinic feedstream in a sorption zone with a liquid hydrocarbon sorbent to selectively sorb C.sub.3 + components;wherein the sorbent is obtained by condensing C.sub.5 + aliphatic and aromatic hydrocarbon from the primary stage.