The influence of metals and acidic oxide species on the steam reforming of dimethyl ether (DME)

A comparative study of various Cu-based catalysts was performed on the steam reforming reaction of dimethyl ether (DME). Ru/Al 2O 3 showed very high CH 4 production, irrespective of the presence of acidic sites, due to the high intrinsic methanation activity of Ru metal. In contrast, Cu-based catalysts did not produce CH 4 as a by-product when mixed with acidic oxides such as Al 2O 3. CuMn-spinel + Al 2O 3 was superior to commercial CuZnAl + Al 2O 3, exhibiting higher DME conversion at a lower temperature. Replacing Al 2O 3 with a zeolite led to a further increase in activity. The higher performance of the CuMn-spinel catalyst can be attributed to its high methanol steam reforming activity. Thus, the activity and selectivity of this process strongly depend on the identity of the metals and acidic oxide species employed. ▪ The performance of catalysts from the platinum group and Cu-based catalysts were compared in the dimethyl ether (DME) steam reforming reaction. Without acidic oxides, Cu-based catalysts formed undesired CH 4 via a direct decomposition of DME into methoxy (–OCH 3) and methyl (–CH 3) groups, followed by the hydrogenation of the methyl group to CH 4. However, in the presence of acidic oxides such as Al 2O 3, practically no CH 4 was produced. Therefore we speculate that the MeOH formed on the acidic sites moves onto Cu and is adsorbed as a methoxy group without the co-formation of a methyl group, preventing the formation of CH 4 and leading to an even higher yield of H 2. Pt/Al 2O 3 and Ru/Al 2O 3 showed a relatively high DME conversion, although the undesired production of CH 4 was quite high, irrespective of the presence of acidic sites. A high CH 4 selectivity can be explained in terms of a high methanation activity. The catalyst formed from CuMn 2O 4 spinel oxide mixed with Al 2O 3 showed higher activity and greater durability than commercial CuZnAl catalysts mixed with Al 2O 3. By replacing Al 2O 3 with H-ZSM5, the CuMn 2O 4 spinel oxide showed a further increase in activity resulting in up to 100% conversion even under 300 °C. We attribute this very high activity at relatively low temperature to both the high DME hydration activity of H-ZSM5 and the high MeOH steam reforming activity of CuMn 2O 4 spinel oxide.