We provide a process for regenerating a spent acidic ionic liquid, comprising contacting the spent acidic ionic liquid with hydrogen and without an addition of a hydrogenation catalyst; wherein a conjunct polymer content is decreased in the spent acidic ionic liquid to produce regenerated acidic ionic liquid. We also provide a process for making an alkylate gasoline blending component, comprising: a) alkylating a mixture of isoparaffins and olefins using an acidic ionic liquid and an alkyl halide or a hydrogen halide, wherein a conjunct polymer accumulates in a spent acidic ionic liquid; and b) feeding the spent acidic ionic liquid and a hydrogen, and without an addition of a hydrogenation catalyst, to a regeneration reactor operated under selected hydrogenation conditions to produce a regenerated acidic ionic liquid that is used for the alkylating, wherein the conjunct polymer in the regenerated acidic ionic liquid is decreased by at least 50 wt %.