Density functional theory was used to identify the active site and mechanism responsible for an experimentally observed two-order-of-magnitude increase in propane dehydrogenation activity upon modifying H-ZSM-5 with Ga with a Ga/Al ratio of 0.5. It was found that a unique active site consisting of adjacent Brønsted and Lewis acid sites catalyzes heterolytic C-H bond activation by a bifunctional mechanism. The active species is [GaH]2+, which acts as a strong Lewis acid for stabilizing the resulting propyl anion, while a framework oxygen serves as a basic site for accepting the proton from the C-H bond. This leads to an extremely low intrinsic C-H activation barrier of 55 kJ/mol, significantly lower than in mechanisms proceeding through a Brønsted or Lewis acid site alone. The low activation barrier is attributed to the significant positive charge of +1.01 on Ga in the [GaH]2+ state. Following C-H activation, the proton combines with the Ga-bound hydride to liberate H2, after which the propyl anion is eliminated as propene. The proposed bifunctional Lewis/Brønsted acid mechanism is consistent with a sharp maximum in the experimental turnover frequency at a Ga+:H+ ratio of 1:1.

Lewis−Brønsted acid pairs in Ga/H-ZSM5 to catalyze dehydrogenation of light alkanes

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

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