Abstract: Novel acid systems are disclosed which are characterized as being capable of stabilizing high concentrations of tertiary cations, e.g., t-butyl cation, and further characterized as capable of forming carbonium ion salts containing both dimeric and monomeric anions. The ions undergo hydride and halide exchange with other alkanes and halides. The hydride transfer reaction renders them useful in isomerization and alkylation reactions.

Abstract: A hydrocarbon feed is isomerized in liquid phase in the presence of a metal halide catalyst, a hydrogen halide solvent and hydrogen at a temperature ranging from at least 50.degree.C and not greater than the critical temperature of the mixture of the hydrocarbon feed and the hydrogen halide. The partial pressure of the hydrocarbon feed-hydrogen halide mixture is maintained to be at least equal to the critical pressure of the hydrocarbon feed and not greater than the critical pressure of the mixture of the hydrocarbon feed and the hydrogen halide. The molar ratio of the hydrogen halide to the hydrocarbon feed is at least 1:1 and the molar ratio of hydrogen halide to metal halide catalyst ranges from about 10:1 to about 40:1. The preferred catalyst is aluminum chloride or aluminum bromide. The preferred solvent is hydrogen chloride or hydrogen bromide.