Reaction regeneration cycle of Mo/HZSM-5 catalyst in methane dehydroaromatization with the addition of oxygen-containing components

Abstract

Reaction regeneration cycle of methane dehydroaromatization (MDA) with oxygen-containing gas components was studied. XRD, BET, Raman, NH3-TPD, O2-TG/DTG, TEM and 27Al-NMR were used to monitor textural structure, Mo species, and acid sites of catalyst before and after regeneration. Addition of oxygen components can extend reaction time per pass but cannot prevent the deactivation of regenerated catalyst. MoO3 species, acidity, and texture properties of Mo/HZSM-5 was identical after first regeneration, which may account for complete recovery of methane conversion and aromatic formation. During regeneration, the inevitable increase in Mo species size disrupts carbon deposition and significantly reduces methane dissociation. The crystallinity and number of strong acid sites of Mo/HZSM-5 catalyst decreased to a stable level before the collapse of zeolite framework without hindering aromatic formation. The recovered large-sized Mo species may accelerate the collapse of zeolite framework, irreversibly destroying Mo/HZSM-5 catalyst.