Reaction characteristics of dimethyl ether (DME) steam reforming catalysts for hydrogen production

The purpose of this study was to develop new catalysts for dimethyl ether (DME) steam reforming (SR) in the absence of a carrier gas for hydrogen fuel cell vehicles and to find the optimal reaction conditions for said process. The steam reforming catalysts were prepared by impregnation of Cu, the active material, with Ce and Ni additives using mordenite (MOR) and alumina as supports. The prepared catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and inductively coupled plasma - optical emission spectrometer (ICP-OES). The catalysts were prepared in honeycomb and pellet form. The hydrogen yield with the pellet Cu10MOR10/γ-Al2O3 catalyst was 80% at 400 °C, higher than that obtained with the honeycomb catalyst under the same experimental conditions (50%). The ratio of H2O/DME, one of the most important parameters among the experimental conditions, afforded the best hydrogen yield at a value of 6, higher than the theoretical ratio of 3. Space velocity (SV) values in the range of 340-510 h−1 afforded hydrogen yields of ∼80%. The hydrogen yield was similar at temperatures in the range of 300-550 °C although, at 400-450 °C, higher DME conversions and lower CH4 production were observed. The addition of Ni to the catalyst resulted in the inhibition of the deposition of hydrocarbons, and the Ce additive was found to increase the DME conversion. Finally, it was found that the best catalyst for DME steam reforming was Cu10Ce4MOR10/γ-Al2O3. The optimum reaction conditions for H2 production were determined as SV = 340 h−1, H2O/DME ratio = 6, the pellet-type catalyst, and a catalytic reaction temperature range of 400-450 °C.