Dimethyl ether steam reforming to produce H2 over Ga-doped ZnO/γ-Al2O3 catalysts

Abstract

Herein, we report the performance of a series of gallium-doped zinc oxide (GDZ) catalysts mechanically mixed with γ-Al₂O₃ (GDZ/γ-Al₂O₃) for the dimethyl ether (DME) steam reforming (SR) to produce H₂. Compared with the ZnO catalyst mechanically mixed with γ-Al₂O₃, the doping of ZnO with gallium can significantly improve the conversion of DME and the yield of hydrogen. The catalyst with a Zn : Ga molar ratio of 9 : 1 has the highest conversion of DME (95.4%) and yield of hydrogen (95.0%) at 450 °C. The carbon dioxide selectivity of GDZ/γ-Al₂O₃ catalysts is higher than 95%, which is much higher than that of the CuZnAlO/γ-Al₂O₃ catalyst. Moreover, the GDZ/γ-Al₂O₃ catalysts have better stability than the CuZnAlO/γ-Al₂O₃ catalyst. Doping of ZnO with gallium generates a large number of oxygen vacancies on the catalyst, which is beneficial to the DME SR reaction. Our results indicate that HCOO– is an intermedium of DME SR over GDZ/γ-Al₂O₃ catalysts, and the transformation from HCOO– to CO₂ is the rate-controlling step. The results of conductivity indicate that the rate-controlling step is an n-type reaction.