Abstract
Zeolite-catalyzed dehydration of ethanol offers promising perspectives for the sustainable production of ethene. Complex parallel-consecutive pathways are proposed to be involved in the reaction network of ethanol dehydration on zeolites, where the initial step of ethanol dehydration is still unclear particularly for the favorable production of ethene at lower temperature. Here we report the observation of a triethyloxonium ion (TEO) in the dehydration of ethanol on zeolite H-ZSM-5 by using ex situ and in situ solid-state NMR spectroscopy. TEO is identified as a stable surface species on the working catalyst, which shows high reactivity during reaction. Ethylation of the zeolite by TEO occurs at lower temperature, leading to the formation of surface ethoxy species and then ethene. The TEO-ethoxide pathway is found to be energetically preferable for the dehydration of ethanol to ethene in the initial stage, which is also supported by theoretical calculations.
Highlights
Zeolite-catalyzed dehydration of ethanol offers promising perspectives for the sustainable production of ethene
The dehydration of ethanol to ethene over H-ZSM-5 has been investigated by combined experiments and density functional theory (DFT) calculations
It was reported that trimethyloxonium can be generated on H-ZSM-5 zeolite
Summary
Zeolite-catalyzed dehydration of ethanol offers promising perspectives for the sustainable production of ethene. Complex parallel-consecutive pathways are proposed to be involved in the reaction network of ethanol dehydration on zeolites, where the initial step of ethanol dehydration is still unclear for the favorable production of ethene at lower temperature. Ethylation of the zeolite by TEO occurs at lower temperature, leading to the formation of surface ethoxy species and ethene. The detailed knowledge of the reaction mechanism of ethene formation in ethanol dehydration is important for understanding ethanol dehydration as a model reaction of alcohol conversion and for the development of improved catalysts for light olefins production. Solid-state NMR and infrared spectroscopic studies[16,20,21] confirmed the formation of surface-bound ethoxy species as a stable intermediate in ethanol dehydration of on H-ZSM-5 and HY zeolites. Ethene and hydrocarbons are formed by the subsequent decomposition of the surface ethoxy species.
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