Theoretical investigation of double-bond isomerization of 1-hexene to trans-2-hexene on H-ZSM-5 zeolite

Effect of ketene additive and Si/Al ratio on the reaction of methanol over HZSM‐5 catalysts

“…analyzed the influence of the acidity of HZSM‐5 catalyst on the catalytic transformation of various short‐chain olefins. The isomerization and dimerization reactions of olefins, assembly of cyclic hydrocarbons from small building blocks of olefins, cyclization and aromatization of linear alkenes, hydrogenation reaction of olefins to alkanes, and methylation of aromatics over HZSM‐5 catalyst were the subjects of these investigations. The C–C bond formation mechanisms through the ketene intermediate which so calls the CO‐catalyzed mechanism predicts that CO molecule associates with protonated methanol, dimethyl ether, or surface methoxy to form ketene at the first step.…”

Zeolite-catalyzed Isomerization of 1-Hexene to trans-2-Hexene: An ONIOM Study

“…This scenario is different from the bifunctional nature of the zeolite active sites which combines the roles of both the Brønsted acidic hydroxyl group and the neighboring basic oxygen. 34 The structural parameters of the C 6 H 13 fragment in TS1 are very close to the classical form of the 2-hexyl secondary carbenium ion,…”

“…Moreover, Kazansky 8 proposed that the doublebond isomerization of the olefin involves the formation of a surface alkoxy group by proton addition from the zeolite to the double bond of the olefin and the following decomposition of this alkoxy intermediate. In our previous work, 34 in an attempt to ascertain the reaction pathway for the double-bond isomerization of 1-hexene to trans-2-hexene on H-ZSM-5 zeolite, we also pointed out that the reaction proceeds by a bifunctional (acid-base) mechanism of active centers with the formation of covalent alkoxy intermediates.…”

“…This value is comparable to that we reported previously upon the bifunctional mechanism (30.92 kcal/mol). 34 In addition, the calculated apparent activation energy is 12.65 kcal/mol, which is the energy difference between the TS1 and separated reactants (isolated 1-hexene and the 54T cluster). This value is in good agreement with the average experimental activation energy value of 13.38 kcal/mol reported by Clark and Subramaniam 57 and close to the calculated activation energy values (10.80 kcal/mol reported by Bhan et al 33 and 10.47 kcal/mol reported by us, 34 respectively) for the bifunctional mechanism.…”