Coaromatization of methane and propane over Ga supported on HZSM-5 catalysts: The effect of mesoporosity on deactivation behavior

Abstract

Ga supported on mesoporous HZSM-5 (GaOy/meso-HZSM-5) and conventional HZSM-5 (GaOy/micro-HZSM-5) catalysts were compared to investigate the effect of mesoporosity on the deactivation behavior in the coaromatization of methane and propane. The trend of reaction intermediate distribution between the catalysts became gradually different with time-on-stream, implying a distinction in deactivation behavior. These are attributed to the behavior of acid site blockage, because the production of BTX are driven by acid sites. The reaction with (CH4)-C-13 and further analyses revealed that the interaction between coke and Ga species that serve as Lewis acid sites is much stronger in GaOy/micro-HZSM-5 than in GaOy/meso-HZSM-5 post-reaction catalyst. Therefore, large amount of highly condensed coke was deposited in GaOy/micro-HZSM-5 during the reaction, leading to fast catalyst deactivation. Consequently, the structural difference arising from mesoporosity affects physicochemical properties of the catalysts thereby contributing to different deactivation behavior between the catalysts.