Effect of W addition on the catalytic properties of Mo/HZSM-5 catalyst in methane non-oxidative dehydroaromatization

Mo/HZSM-5, Mo-W/HZSM-5 and W/HZSM-5 catalysts were prepared via a conventional impregnation method. The catalysts were characterized by means of XRD, BET, Py-FTIR, H₂-TPR, XPS, TEM, NH₃-TPD, TPO, TG and Raman, and were evaluated in methane non-oxidative dehydroaromatization(MDA). Compared with Mo/HZSM-5, the CH₄ conversion, aromatics yield and catalytic stability were improved by W addition for Mo-W/HZSM-5 in MDA reaction. H₂-TPR and XPS results indicated that the octahedral (WO₆)^n- groups existed in Mo-W/HZSM-5 were more easily reduced to W⁴⁺-containing species in MDA reaction in comparison with W/HZSM-5, and W⁴⁺-containing species was correlated with the high MDA activity. At the same time, it is found that graphitic-like coking is the main reason of catalyst deactivation for Mo/HZSM-5, and this coking over Mo-W/HZSM-5 catalyst can be inhibited by W addition during MDA.