Abstract: Improvements in heat exchanging of distillation steps in sulfuric acid alkylation processes; removing water from the vaporous overhead fraction of a sulfuric acid alkylation process distillation step or deisobutanizer to enable mixing thereof with the vaporous hydrocarbon effluent from the reaction zone which contains sulfur dioxide vapors sulfur trioxide and H.sub.2 SO.sub.4 mist, thus permitting mixing of the vaporous fraction and effluent for compression before use as a compressed heat exchanging medium in the alkylation process; sulfuric acid alkylation with deisobutanizer tower overhead effluent acid wash.