A Theoretical Investigation Into Ethanol To Propylene Catalyzed By Zeolite

Propene is one of the commonly used raw materials in chemical production.At present,the demand for propene derivatives in the market is growing,and the relationship between supply and demand of propene is gradually unbalanced.Due to technical limitations,the ability to increase propylene production through petroleum cracking and catalytic cracking is limited.Common methods such as methanol to propene,olefin disproportionation and propane dehydrogenation have limited production capacity,while high energy and cost.Therefore,it is necessary to explore new ways to increase propene production.Ethanol to propene?ETP?is a promising industrial technique.A two-layer ONIOM study has been carried out to investigate the mechanism of ethanol to propene catalyzed by H-Beta,H-FAU,H-MCM-22,and H-ZSM-5.We got the structure and energy data of each intermediate and transition state of these reactions.The activation barriers of transition states and potential energy surface?PES?are also calculated.By comparing the catalytic processes over the four zeolites,the main results are as follows:1.The ETP reaction in the C₇⁺pathway is easier to ocurr on the H-Beta and H-ZSM-5zeolites.The energy of the rate-determining step in the C₇⁺pathway on the H-ZSM-5 zeolite(TS-C7-5,108.36 kJ?mol^-1)is lower than that on H-Beta(TS-C7-5,157.33 kJ?mol^-1),indicating that the C₇⁺pathway of ethanol to propene is easier to occur on H-ZSM-5 zeolite.The energy of rate-determining step in the C₈⁺pathway(TS-C7-6,158.20 kJ?mol^-1)on H-ZSM-5 zeolite is lower than that on other zeolites,showing that the C₈⁺pathway of ethanol to propene is easier on H-ZSM-5 zeolite.2.The energies of the rate-determining step?TS-C8-6?in the C₈⁺pathway are higher than those in the C₇⁺pathway?TS-C7-5?on four zeolites.Furthermore,the C₈⁺pathway involves more transition states.3.In summary,the H-ZSM-5 zeolite has the lowest reaction energy,so H-ZSM-5 zeolite can be used as the optimized zeolite for catalyzing the reaction of ethanol to propene;in addition,the rate determination step of the C₇⁺pathway is higher than the C₈⁺pathway.The energy is lower and the reaction process is simpler,so the ethanol to propene reaction is more likely to proceed on the H-ZSM-5 zeolite according to the C₇⁺route.