Catalytic hydrocracking of 9,10-dihydroanthracene on HY zeolite – Activity dependence on acid strength

Abstract

Due to the practical importance of Y zeolites in catalytic hydrocracking of polyaromatic hydrocarbons, the detailed mechanisms of 9,10-dihydroanthracene catalytic hydrocracking on HY zeolite with different Al substitution (1Al, 3Al, 6Al; Si/Al = 47, 15, 7) and 6Al with trinuclear extra-framework Al (EFAl) in the sodalite cage (6Al + EFAl, Si/Al = 4.67) in different acid number and strength have been computed. It is found that the heterolytic activation of H₂ encapsulated within a conjugated Frustrated Lewis Pair (FLP), generated by the transfer of acidic O-H proton to hydrocarbon substrate, is the rate-determining step for the formation of 1-benzyl-2-methylbenzene and its conversion to benzene, toluene, and o-xylene. A correlation between Brønsted acid strength (enthalpy of adsorption of pyridine) and catalytic activity (apparent Gibbs free energy barrier) has been found, e.g., a higher acid strength corresponds to a lower apparent Gibbs free energy barrier and therefore higher catalytic activity. Since the conversion of 1-benzyl-2-methylbenzene has lower apparent Gibbs free energy barrier than its formation, its detection under the reaction condition is difficult or unlikely.