Steam reforming of dimethyl ether over composite catalysts of γ-Al2O3 and Cu-based spinel

Abstract

Cu-based spinel-type oxides were investigated for steam reforming of dimethyl ether (DME). Addition of γ-Al2O3 to Cu catalysts improved DME conversion since hydrolysis of DME was promoted over acid-sites on γ-Al2O3. Higher catalytic activity was shown over the composite of γ-Al2O3 and Cu–Mn, or Cu–Fe, or Cu–Cr oxide than that of γ-Al2O3 and Cu/ZnO/Al2O3. Cu–Fe and Cu–Mn catalysts demonstrated high activity for methanol steam reforming, which was ascribed to high performance for DME steam reforming. XPS measurements revealed that mono- and zero-valent copper species co-existed on Cu–Mn, Cu–Fe, and Cu/ZnO/Al2O3 catalysts subjected to in situ H2 reduction following methanol steam reforming.In the system of γ-Al2O3 and Cu–Mn–Fe oxide, Mn/Fe ratio was optimized. Mn/Fe ratio exhibited influence on CO2 and CO selectivity. Mn-rich composite catalysts produced more CO than Fe-rich catalysts. The optimized atomic ratio of Cu/Mn/Fe was 2/1/3. DME conversion was not influenced by steam/DME ratio in the feed gas, while CO formation was suppressed with a rise in steam/DME ratio. Complete DME conversion was attained below 350°C over the optimized composite catalyst. The optimal Al2O3/Cu–Mn–Fe weight ratio was between 1/2 and 1. High catalytic activity and thermal stability of the optimal composite was found by the time-on-steam test at as high as 400°C for 100h.