Transition-Metal Catalysts for Methane Dehydroaromatization (Mo, Re, Fe): Activity, Stability, Active Sites, and Carbon Deposits

The most studied catalysts for methane dehydroaromatization (MDA)?Mo/ZSM-5?are not commercialized yet due to the rapid deactivation and insufficient activity. Catalytic systems based on Fe Re are potential alternatives Mo-containing zeolites. Here, we compare catalytic performance of these as a function metal type its loading in ZSM-5 zeolite. results show that activity decreases order Re/ZSM-5 > Mo/ZSM-5 Fe/ZSM-5, while catalyst stability opposite order: Fe/ZSM-5 Re/ZSM-5. active species working were determined by operando X-ray absorption near-edge structure spectroscopy combined with mass spectrometry. We found Re0 Fe2+ likely CH4 aromatics respective catalysts. Combining pulse reaction technique thermogravimetry analysis–mass spectrometry experiments, demonstrate length induction period strongly correlates catalyst. longer indicates slow growth hydrocarbon pool intermediates inside zeolite pores thus explains poor performance. Finally, both formation can be improved increasing loading, pressure, space velocity.