COKE AND DEACTIVATION .1. STOICHIOMETRY OF COKE FORMATION IN THE CATALYTIC REACTIONS OF N-HEXENE ON USHY

Mechanistic studies of the reactions of n-hexene on USHY zeolite at 305° and 500°C show the presence of alkyl cyclopentenes as primary products of reaction. The presence of such species, which are potential intermediates in the dehydrogenation process of the surface species, indicates that the reaction process which produces mononuclear and polynuclear aromatic species found in "coke" and in trace amounts in the desorbed phase, begins with a cyclization reaction of a saturated carbenium ion, followed by sequential dehydrogenation of the cyclic surface species. Detailed stoichiometry of the initial reaction mechanism reveals that the initial material detected as coke contains a range of molecular sizes. Small-chain species dominate the spectrum, accounting for over 80 mol% of the initial coke. This results in an average initial coke molecule of C5.1H9.4. © 1990.