Promotional effect of Ru on the dehydrogenation and aromatization of methane in the absence of oxygen over Mo/HZSM-5 catalysts

A reaction rate of methane conversion of 14.54 nmol(-1) m(-2) and the formation rate of aromatics of 2.22 nmol(-1) m(-2) at 973 K for the dehydrogenation and aromatization of methane in the absence of oxygen was attained over Mo-Ru/HZSM-5 catalysts. Ey comparison, over unpromoted Mo/HZSM-5 catalysts, the reaction rate of methane conversion was 10.17 nmol(-1) m(-2) and the formation rate of aromatics was 1.52 nmol(-1) m(-2). The Ru-promoted Mo/HZSM-5 catalysts also show better stability. The catalyst with 2% Mo loading and with Mo/Ru atomic ratio ranging from 3 to 7 shows much better catalytic performance. NH3-TPD shows that the addition of Ru onto 2Mo/HZSM-5 causes a further decrease in the amount of strong acid sites and at the same time, creates new acid sites with moderate acid strengths. TPR and DTA studies illustrate that the existence of Ru with a proper dispersion promotes the reduction of Mo species and the splitting of the C-H bond of methane. (C) 1997 Academic Press.