The conventional model of the Brønsted acid active site of an aluminosilicate zeolite is an extra framework proton present near an aluminum framework site as required to maintain electroneutrality when replacing Si<sup>4+ </sup>with Al<sup>3+</sup>. For H-ZSM-5, it is established that this proton has a strong affinity to zeolite framework such that in the presence of a single adsorbed molecule of methanol or water, it remains bound to the framework and only forms a hydrogen bond with the adsorbed molecule. This strong affinity raises the question of whether, in this form, this proton is active in catalyzing reactions such as methanol dehydration to dimethyl ether. Here we present evidence to show that this proton, when still strongly associated with the negatively charged framework, is much less active than a proton solvated by two methanol molecules, or by one water molecule in the presence of methanol molecules. The implication of this finding on the reaction mechanism of methanol dehydration is discussed.

New look at the Brønsted acid sites of H-ZSM-5 for methanol dehydration

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.