XPS, XAES, and TG/DTA characterization of deposited carbon in methane dehydroaromatization over Ga-Mo/ZSM-5 catalyst

The catalytic dehydroaromatization of methane over 3.0%Mo/HZSM-5 and 0.1%Ga-3%Mo/HZSM-5 catalysts were reported. The nature of deposited carbon was characterized by means of XPS, XAES, TG/DTG, HRTEM, and DTA techniques. In XAES study, the type of deposited carbon was characterized based on the fine structures of dN/dE spectra. The results confirm that the sp2/sp3 bonding ratio of coke species increases with on-stream time, suggesting that the deposition of heavier aromatic-type carbon is the main reason for catalyst deactivation. The addition of gallium to 3.0%Mo/HZSM-5 enhances the adsorption of COx species as well as the formation of alkene (such as ethylene). Therefore, the Ga-modified 3%Mo/HZSM-5 catalyst is more active and stable than the unmodified one.