The present invention provides process for preparing an alkylate comprising contacting in a reactor a hydrocarbon mixture comprising at least an isoparaffin and an olefin with an acidic ionic liquid catalyst under alkylation conditions to obtain an alkylate, which process further comprises: -withdrawing an alkylate-comprising reactor effluent from the reactor, wherein the reactor effluent comprises an ionic liquid phase and a hydrocarbon phase; -separating at least part the reactor effluent into a hydrocarbon phase effluent and a multiple-phase effluent in a centrifugal separation unit; -fractionating at least part of said hydrocarbon phase effluent into at least a stream comprising alkylate and a stream comprising isoparaffin.