Conversion of Methanol to Hydrocarbons over Ga2O3/H-ZSM-5 and Ga2O3/WO3 Catalysts

The conversion of methanol over physical mixtures of Ga2O3 and H-ZSM-5 or WO3/γ-Al2O3 is reported. The addition of Ga2O3 to H-ZSM-5 markedly increases the selectivity to aromatic hydrocarbon at the expense of C2–C4 alkenes, without affecting the overall conversion. This effect is obtained at temperatures ≥400°C, and the maximum effect is observed at 1 : 1 mixtures of Ga2O3 and H-ZSM-5. Experiments using separate beds of Ga2O3 and H-ZSM-5 with different configurations do not reveal any significant effect. In addition, upon removal of Ga2O3 from the Ga2O3/H-ZSM-5 physical mixture the normal catalytic performance of the zeolite is observed. Ga2O3 is also shown to significantly enhance the catalytic activity of a WO3/γ-Al2O3 catalyst when it is incorporated as a physical mixture. The results are explained in terms of a new active site that is formed at the point of contact between Ga2O3 and H-ZSM-5 or WO3/γ-Al2O3 particles. In the case of H-ZSM-5/β-Ga2O3, this site catalyzes the formation of aromatic products from C2–C5 alkenes, whereas for WO3/γAl2O3:β-Ga2O3 the new site catalyzes the formation of methane.