Enhanced methane dehydroaromatization in the presence of CO2 over Fe- and Mg-modified Mo/ZSM-5

A series of metal-modified (i.e., Fe or Mg) Mo/ZSM-5 were prepared by the impregnation method and subsequently tested in the aromatization of CH4-CO2 mixtures in a continuous flow fluidized-bed quartz reactor. Mg modification improved both the catalytic activity (9.7 vs. 12.3% conversion) and the selectivity to benzene (65.7 vs. 68.4%) while inhibiting carbon deposition (13.9 vs 10.1% carbon deposited, as determined by thermogravimetry, TG) during the dehydroaromatization of methane in the presence of CO2. SEM confirmed that the carbon species deposited over Mo/HZSM-5 and Fe-Mo/HZSM-5 catalysts were mainly carbon nanotubes. In contrast, carbon nanotubes were not detected over Mg-Mo/HZSM-5. The TG profiles and the XPS spectra revealed that the introduction of Mg likely favored the generation of Mo2C species which are considered active sites for methane dehydroaromatization. The present work provides a strategy for greatly improving the catalytic performance in the methane dehydroaromatization in the presence of CO2. (C) 2017 Published by Elsevier B.V.