How does the balance of metal and acid functions on the benchmark Mo/ZSM-5 catalyst drive the Methane dehydroaromatization reaction?

Among all the proposed catalytic systems (new supports, synthesis post-treatment, change of transition metal, multi-metallic catalysts, etc.) for the methane dehydroaromatization, the initial Mo/ZSM-5 has remained one of the best suitable catalysts, despite its lack of deep understanding. The catalyst evolves throughout four successive stages: calcination, activation, induction, and deactivation. By studying the balance influence between the acid and metal functions throughout its lifetime, the molybdenum and carbon species could be localized, quantified, and identified as well as their roles. An optimal compromise was then established where the catalyst is composed of 4 wt% Mo with the highest possible acidity. Below these targets, the catalysts with minimal Mo content and low Brønsted acidity display poor catalytic performances, whereas zeolite amorphization occurs during the early stages of the reaction independently of the zeolite acidity once the Mo loading exceeds the optimal value.