Origin, evolution, and structure-activity relationship of crucial species toward non-oxidative propane...

Metal-exchanged zeolites are cost-effective and environmentally friendly catalysts for non-oxidative propane dehydrogenation (PDH), offering high activity, selectivity, and stability. These characteristics make them promising alternatives to conventional Pt-based or toxic Cr2O3 catalysts. In this study, we demonstrated that experimentally quasi in situ characterized species, such as metal hydrides, influence the formation of propene and hydrogen, exemplified by the CHA zeolite catalyst. Density functional theory (DFT) calculations confirmed that the metal hydride-mediated pathway is more feasible compared to the previously proposed heterolytic "alkyl" pathway. Overall, both the heterolytic "alkyl" pathway and metal hydride-mediated pathway consistently demonstrate that the Ga-CHA zeolite exhibits higher reactivity than the In-CHA zeolite. Moreover, the structure-activity relationship for the PDH process depends on a simple structural descriptor: the radius of the internal tangent circle formed by the triangle [GaH2]+ species within 80 types of zeolite datasets. Notably, the AFV zeolite within the International Zeolite Association shows excellent catalytic performance, surpassing that of the CHA zeolite. Our work provides new insights into the PDH reaction mechanism in metal-exchanged zeolites and offers an efficient approach for screening and guiding the synthesis of novel catalysts.