ISOMERIZATION OF 1-CYCLOHEXYLOCTANE ON PT H-ZSM-22 BIFUNCTIONAL ZEOLITE CATALYST/

1-Cyclohexyloctane is isomerized in the vapor phase on Pt/H-ZSM-22 zeo lite catalyst in the presence of hydrogen. Most of the reaction produc ts are identified and analyzed using high-resolution GC and GC/MS. The reaction pathways of 1-cyclohexyloctane are interpreted in terms of a lkylcarbenium/alkylcarbonium ion chemistry. The main isomerization pat hways are branching of the ring, elongation and shortening of alkyl su bstituents on the ring, and ring contractions and expansions. A less i mportant pathway is chain branching, occurring selectively at C-atom p ositions distant from the ring. In the reaction product fraction of he ptyl, methylcyclohexanes, preferential formation of the 1-heptyl-t-4-m ethylcyclohexane is observed. The formation of l-heptyl, Il-methylcycl ohexane is completely suppressed. The peculiar selectivity patterns ar e explained by a mechanism in which the molecules react in micropore m ouths at the external surface of the ZSM-22 zeolite crystals. (C) 1998 Academic Press.