The critical role of the active [GaH] site in -heptane dehydrocyclization over Ga/H-ZSM-5 zeolite

• Published in: Catalysis science & technology 2024-09, Vol.14 (18), p.545-5463
• Main Authors: He, Guangyuan, Mei, Donghai
• Format: Article
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d4cy00648h

The Ga/H-ZSM-5 zeolite has long been acknowledged as an effective catalyst for the aromatization of light alkanes. In the present work, a three-coordinated carbenium ion is identified as a crucial intermediate in the formation of the [GaH] 2+ active site. In particular, the involvement of the carbenium ion as a bridge facilitates the kinetic unhindered creation and restoration of the [GaH] 2+ active site. Using density functional theory calculations, comprehensive reaction pathways for n -heptane, encompassing its conversion to toluene via the C1-C6 ring closure, were explored for both H-ZSM-5 and Ga/H-ZSM-5 zeolites. Compared to the BAS, the [GaH] 2+ active site significantly lowers the activation barrier for the C-H bond cleavage. Furthermore, Bader charge and crystal orbital Hamilton population analysis confirmed that the [GaH] 2+ active site facilitates the activation of the C-H bond of n -heptane while impeding C-C bond cleavage in the aromatization process. The Ga/H-ZSM-5 zeolite has long been acknowledged as an effective catalyst for the aromatization of light alkanes.