Cu-based spinel-type oxides were investigated for steam reforming of dimethyl ether (I)ME). Addition of gamma-Al2O3 to Cu catalysts improved DME conversion since hydrolysis of DME was promoted over acid-sites on gamma-Al2O3. Higher catalytic activity was shown over the composite of gamma-Al2O3 and Cu-Mn, or Cu-Fe, or Cu-Cr oxide than that of gamma-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 H-2 reduction following methanol steam reforming. In the system of gamma-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 stearn/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 T 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 degrees C for 100 h. (c) 2004 Elsevier B.V. All rights reserved.