Transition metal doped cryptomelane-type manganese oxide for low-temperature catalytic combustion of dimethyl ether

The catalysts of transition metals (Fe, Co, Ni, Cu, Cr) doped cryptomelane-type manganese oxide (M-OMS-2) were prepared and investigated for the catalytic combustion of dimethyl ether (DME). The catalysts were characterized by XRD, FT-IR, BET, TEM, ICP-AES, XPS and H2-TPR techniques. The effects of surface area, the average oxidation state, and the redox properties on catalytic activities were studied. The results showed that 100% CO2 selectivity can be realized over the doped OMS-2 catalysts. The M-OMS-2 catalysts displayed the nanorod morphology with a 13 nm diameter and the length ranging from 50 to 220 nm. The Cu doped OMS-2 catalyst exhibited the best activity, achieving the light-off temperature (the temperature acquired for 10% DME conversion, T10) and full-conversion temperature (the temperature acquired for 90% DME conversion, T90) of 171 and 180 °C, respectively. DME catalytic combustion over M- OMS-2 catalysts was found to follow a Mars–van-Krevelen mechanism with the presence of redox between Mn4+/Mn3+ and Mm+/M(m−1)+ (M = Fe, Co, Ni, Cu, Cr).

► Fe, Co, Ni, Cu, Cr doped OMS-2 catalyst were prepared and applied to the DME catalytic combustion.
► Cu-OMS-2 has the best activity with a T10 of 171 °C and a T90 of 180 °C.
► The activity of M-OMS-2 catalyst were greatly influenced by the type of doped metals.
► The activity is related with surface area, average oxidation state and redox properties.