The formation of coke and minor products in 2-methylpentane cracking on USHY has been examined at 673, 723, and 773 K. The results show that the coke precursors are various dehydrogenated carbocations on catalyst surface. Despite the increase of coke yield with reaction time, the selectivity and H/C atomic ratio of coke decrease with rising temperature. Echoing to the formation of coke, minor products including acyclic paraffins, acyclic olefins, methylcyclopentane, diolefins, cyclic olefins, and aromatics are formed by various side-reactions of carbenium ions, such as dehydrogenation, elimination, disproportionation, cyclization, and aromatization. Undergoing of such pathological reaction processes gradually lead to catalyst deactivation. (c) 2008 American Institute of Chemical Engineers.