The Role of Gallium in the Catalytic Activity of Zeolite -ZSM-5 for Methanol Conversion

Article abstract of DOI:10.1021/j100181a051

The transformation of methanol over a series of aluminum-free -ZSM-5 zeolite catalysts with Ga(/(Ga + Si) ratios of 0.015, 0.019, 0.032, 0.039, and 0.054 (corresponding to Si/Ga ratios of 65.7, 51.6, 30.3, 24.6, and 17.5, respectively) has been studied in the 150-450 deg C temperature range.There is strong dependence of selectivity and activity on the concentration of Ga for the formation of dimethyl ether at 150-300 deg C and for the conversion of alkanes into aromatics at 300-450 deg C.The curves describing the yield of dimethyl ether and aromatics rise steadily with the content of Ga, but the curve of the dependence for the yield of olefins is bell-shaped.Framework gallium in Al-free -ZSM-5 does generate Broensted acidity, and the sequence of steps in the reaction of MeOH is the same over -ZSM-5 and -ZSM-5.The role of gallium in the transformation of olefins into aromatics is discussed.