Alkylation of isobutane and butene was carried out in a continuous unit using triethylamine hydrochloride-aluminium(III)chloride ionic liquid as catalyst. The effects of additives of HCl and metal chlorides on the properties of ionic liquids for alkylation were investigated. Improvement of production distribution with high yields of C-8 and selectivity of TMP under a mild reaction condition has been observed after addition of CuCl. (C) 2004 Elsevier B.V. All rights reserved.