Catalysis Letters, Vol.108, No.1-2, 25-30, 2006
Methane dehydroaromatization on Mo/HMCM-22 catalysts: effect of SiO2/Al2O3 ratio of HMCM-22 zeolite supports
HMCM-22 zeolite with variable SiO2/Al2O3 ratios has been successfully synthesized and used as support of molybdenum based catalyst in methane dehydroaromatization. Effect of SiO2/Al2O3 ratio on the catalytic performance of Mo/HMCM-22 catalysts was studied, and results show that methane conversion and benzene selectivity increase with the decrease of SiO2/Al2O3 ratio, and reach maximum on Mo/HMCM-22 catalyst with SiO2/Al2O3 ratio of 25. Further increasing SiO2/Al2O3 ratio results a decrease of activity and benzene selectivity. Al-27 MAS NMR spectroscopy and NH3-TPD techniques were applied to characterize the structure-property relationship of the catalyst. The catalytic performance of Mo/HMCM-22 catalysts in methane dehydroaromatization has been correlated with the Bronsted acidity of HMCM-22 zeolite supports, which may promote not only the methane activation on the Mo carbide sites of Mo/HMCM-22 catalysts, but also further oligomerization of the CHx surface species towards aromatics products in the reaction.
Keywords:methane dehydroaromatization;HMCM-22 zeolite;Mo/HMCM-22 catalyst;SiO2/Al2O3 ratio;Bronsted acidity