The effect of adding aromatic compounds and varying the AlCl3 molar fraction on the catalytic performance of chloroaluminate ionic liquids in isobutane/2-butene alkylation was investigated. Al-27 NMR results and comparison with alkylation catalyzed by solid AlCl3 reveal that the activity of the ionic liquids presumably comes from traces of AlCl3 or Al2O6. The addition of benzene increases the selectivity of C-8 as well as the TMP:DMH ratio in the alkylate. The performance of the modified catalyst is optimized at high isobutane to 2-butene ratios and low temperatures. The used catalyst can be regenerated by replenishment of the aromatic additives. (C) 2007 Elsevier Inc. All rights reserved.