Systems and apparatus for ionic liquid catalyzed hydrocarbon conversion, such as alkylation, using vaporization to remove reaction heat from an ionic liquid reactor and to provide mixing therein, wherein hydrocarbon vapors are withdrawn from the ionic liquid reactor and the withdrawn hydrocarbon vapor is recovered by a hydrocarbon vapor recovery unit in fluid communication with the ionic liquid reactor for recycling condensed hydrocarbons to the ionic liquid reactor. Processes for ionic liquid catalyzed alkylation are also disclosed.