Hydrodealkylation (HDA) of the benzene-toluene-xylene (BTX) fraction of pyrolysis gasoline is an industrial route to produce benzene. Complicated kinetics of aromatic and nonaromatic hydrocarbon reactions has been experimentally investigated at the conditions of this process, employing a polyfunctional Al-Cr-KF catalyst with a high benzene selectivity, model feeds and BTX. The study reports effects of nonaromatic hydrocarbons on high temperature catalytic conversion of toluene. Above 525degreesC the process is found to be thermo-catalytic meaning that reactions take place on the catalyst surface and between catalyst pellets. The "pure" catalytic component of conversion is taken to be the difference between a thermo-catalytic and a thermal (i.e., without catalyst) run at the same conditions. Nonaromatic hydrocarbons substantially boost interpellet toluene HDA which is explained by a mechanism involving very fast decomposition of the nonaromatics into active radicals. The accompanying slight fall in catalytic toluene HDA, on the other hand, is considered to be due to nonaromatics and/or their hydrocracking products impeding toluene diffusion to the catalyst surface-whose active centers they partially occupy. There is evidence that the C6-C8 nonaromatics of BTX influence the toluene conversion in the same manner as n-octane and cyclohexane. Benzene seems to render a small fall in surface conversion of toluene probably by inhibiting its diffusion. It apparently has no significant influence on nonaromatic hydrocracking or thermal toluene HDA. The hydrocracking products of the model feeds and BTX are 97-99 mol% C1-C4 alkanes and 1-3 mol% C2-C4 alkenes irrespective of the run type (i.e., thermal or catalytic). Moreover, given more time the hydrocracking reactions in the voids surpass those on the catalyst surface. Changing hydrogen:BTX molar ratio from 1.5 to 10 raises thermal (respectively "pure" catalytic) contribution significantly (respectively slightly) to conversions of toluene, C8 aromatics, n-octane, cyclohexane, and other C6-C8 nonaromatics.
