Lewis–Brønsted Acid Pairs in Ga/H-ZSM‑5 To Catalyze Dehydrogenation of Light Alkanes

• Published in: Journal of the American Chemical Society Vol. 140; no. 14; pp. 4849 - 4859
• Main Authors: Schreiber, Moritz W, Plaisance, Craig P, Baumgärtl, Martin, Reuter, Karsten, Jentys, Andreas, Bermejo-Deval, Ricardo, Lercher, Johannes A
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 11-04-2018
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b12901

The active sites for propane dehydrogenation in Ga/H-ZSM-5 with moderate concentrations of tetrahedral aluminum in the lattice were identified to be Lewis–Brønsted acid pairs. With increasing availability, Ga+ and Brønsted acid site concentrations changed inversely, as protons of Brønsted acid sites were exchanged with Ga+. At a Ga/Al ratio of 1/2, the rate of propane dehydrogenation was 2 orders of magnitude higher than with the parent H-ZSM-5, highlighting the extraordinary activity of the Lewis–Brønsted acid pairs. Density functional theory calculations relate the high activity to a bifunctional mechanism that proceeds via heterolytic activation of the propane C–H bond followed by a monomolecular elimination of H2 and desorption of propene.