Effect of Type of Matrix on Formation of Aromatics by Cracking and Dehydrocyclization of <i>n</i>-Pentane Using ZnZSM-5 Metal Oxide Hierarchical Composite Catalysts

Mechanisms and Kinetics of the Dehydrogenation of C6–C8 Cycloalkanes, Cycloalkenes, and Cyclodienes to Aromatics in H-MFI Zeolite Framework

“…These studies were extended to C 7 and C 8 diene precursors, and it was found that the activation barriers for 1,6-cyclization routes trend opposite with degree of methylation C 6 > C 7 > C 8 , suggesting that cyclization pathways may also form methylated hydrocarbon rings such as methylcyclohexene and dimethylcyclohexene. Experimental investigations have shown that trienes can also lead to the formation of cyclic hydrocarbons (e.g., cyclohexadiene) and that cyclization is exothermic and irreversible. ,− Diels–Alder reactions, similarly, could lead to the formation of cyclic species from reactions of dienes and alkenes, although these have only been studied on non-acidic zeolites as the reaction is typically not associated with Brønsted acid sites. − Alternatively, dehydrative reactions of dienes with formaldehyde can result in the formation of cyclopentadiene (C 5 H 6 ) via 1,3-butadien-1-ol as an intermediate. C 5 H 6 has been identified during MTO , and has been proposed to be a precursor to deactivation either by interacting with aromatics or by undergoing alkylation, isomerization, and hydride transfers that yield deactivating species, ,, potentially via C 6 intermediates.…”