Dimethyl Ether Steam Reforming over Cu–Zn–Pd/CeO2–ZrO2 Catalytic Monoliths. The Role of Cu Species on Catalyst Stability

Abstract

Dimethyl ether (DME) steam reforming was tested over catalytic monoliths coated with CeO2, ZrO2, or Ce0.5Zr0.5O2 and loaded with Cu, Zn, or CuZn and promoted with Pd. The best initial catalytic performance in terms of activity and yield toward the reforming products, H2 and CO2, was exhibited by CuPd/ZrO2, but it suffered strong deactivation. CuZn/ZrO2 showed less activity but a high selectivity and stability. In situ XPS and in situ IR studies showed a relationship between stability and surface copper species. A reactive formate intermediate as well as surface Cu0–Cu+ species prevailed over CuZn/ZrO2 under reaction conditions, whereas a less reactive methoxy species, oxidized copper and carbonaceous residues prevailed over CuPd/ZrO2.