Mo LIII-edge XANES Study of Catalytically Active Mo Species on Silica–Alumina Supports for Methane Dehydroaromatization

Abstract

Abstract L-edge XANES spectroscopy is applied to characterize the active Mo species for methane dehydroaromatization over MoO3/SiO2–Al2O3 and MoO3/H–MFI. For highly active MoO3(7.5 wt %)/H–MFI in Si/Al2 = 90, dispersed molybdenum(II) carbide species are formed with oxy-carbide species after the reaction. Partially reduced species (Mo4+) are formed on amorphous SiO2–Al2O3 support, as well as MoO3/H–MFI in high Si/Al2 ratio. In contrast, formation of deeply reduced ions such as metallic ones on H–MFI with low Si/Al2 ratio also gives low activity. It is suggested that stable molybdenum(II) carbide can be formed dispersively on H–MFI (Si/Al2 = 90) even in coexistence of oxo-species.