Topology-Dependent Iso-Propanol Dehydration Pathway Over Zeolites.

The zeolite-catalyzed dehydration of low-carbon alcohols is a crucial step in the conversion of biomass-derived compounds. Compared to methanol and ethanol, the propanol dehydration mechanism remains poorly understood. The core challenge lies in the high reactivity and short lifetime of its intermediates, beyond the time-resolution of conventional spectroscopic techniques. In this work, we proposed an ammonia co-adsorption strategy to concurrently decelerate the reaction rate and capture the active intermediates during zeolite-catalyzed iso-propanol dehydration process. In combination with one-/two-dimensional solid-state NMR and theoretical simulations, we successfully resolved the long-standing controversy on the origin and evolution of the highly reactive iso-propyl alkoxy or carbocation intermediates. It is found that the formation sequence of these active species and propene is closely associated with the zeolite topological architectures, exhibiting a hitherto unreported topology-dependence. These findings provide a reliable strategy for elucidating the detailed mechanism of the extremely quick alcohol dehydration reaction and offer new mechanistic insights into the zeolite-catalyzed alcohol chemistry.