Isomerisation of n-hexane and mixture of n-hexane and n-pentane was performed in a batch reactor using the pure ionic liquid triethyl amine hydrochloride-aluminium chloride (C2H5)3NHCl/AlCl2), and a mixture of this ionic liquid with a transition metal salt. The reaction was carried out smoothly in liquid phase under atmosphere pressure. The acidity of ionic liquid was modified by the addition of CuCl. The substrate conversion 25 percent and research octane number 89 were observed by using (C2H5)3NHCl/AlCl2) (molar traction of AlCl2 is 0.64) in the present of CuCl at 10°C over a period of 1 hours. The products were separated simply by decantation, and thus the catalyst can be reused. Moreover, the formation of heavy hydrocarbons is minimised.