2016 Volume 59 Issue 6 Pages 293-298
Several supported transition metal oxides (X/Y, X＝WO3, Nb2O5, Y＝Al2O3, TiO2, SiO2) were investigated as solid acid catalysts for hydrolysis of dimethyl ether (DME). Among the transition metal oxide catalysts tested, Nb2O5/Al2O3 showed the highest catalytic activity in the temperature range appropriate for DME steam reforming. Using several types of Nb2O5/Al2O3 samples, the effects of Nb2O5 loading amounts and calcination temperature on the catalytic activity were studied to enhance the hydrolysis activity. XRD patterns showed AlNbO4 phase appeared when the calcination temperature was over 800 °C. The BET surface area decreased for the increase in the calcination temperature. For Nb2O5/Al2O3, the acid amount increased consistently with the Nb2O5 loading amounts up to 25 wt%, and it became almost constant for the further increase in the Nb2O5 loadings. 25 wt% Nb2O5/Al2O3 catalyst calcined at 500 °C exhibited the highest catalytic activity for DME hydrolysis, and consequently steam reforming of DME was carried out over the Nb2O5/Al2O3 mixed with Cu/ZnO/Al2O3. It was found that an optimal ratio of Cu/ZnO/Al2O3 to Nb2O5/Al2O3 was 1, which resulted in higher catalytic activity for steam reforming of DME than a mixture of Cu/ZnO/Al2O3 and γ-Al2O3.
