Activity and Structure of Mo-HZSM5 Catalysts for Non-Oxidative Methane Dehydroaromatization

Non-oxidative dehydroaromatization (DHA) of methane over Mo/HZSM-5 catalysts offers an attractive route for the production of valuable aromatic compounds such as benzene, toluene, and xylene (BTX).  However, there are numerous technical challenges that need to be overcome for developing highly efficient systems.  Under typical operating conditions, catalyst deactivation is mainly attributed to coking of the zeolite.  Furthermore, there is a long-standing debate in the scientific literature regarding the transformation of MoO₃ to active Mo_xC_y species in these catalysts and deactivation mechanisms.  Thus, a better understanding of structure-activity relationships will lead to rational design of DHA catalysts, which in turn will facilitate advances in methane utilization technologies.

We have synthesized and investigated Mo-based catalysts supported on HZSM-5 containing different promoters and varying degrees of acidity.  Results from ex situ and in situ surface and bulk characterization techniques have shed light on the factors that control the activity, selectivity, and stability of these catalysts.  Correlations between the catalytic performance and Mo_xC_y species associated with the Brönsted acid sites of HZSM-5 will be discussed.