Steam Reforming of Dimethyl Ether over Coupled Catalysts of CuO-ZnO-Al2O3-ZrO2 and Solid-acid Catalyst

Steam reforming (SR) of dimethyl ether (DME) was investigated for the production of hydrogen for fuel cells. The activity of a series of solid acids for DME hydrolysis was investigated. The solid acid catalysts were ZSM-5 [Si/Al = 25, 38 and 50: denoted Z(Si/Al)] and acidic alumina (gamma-Al2O3) with an acid strength order that was Z(25)>Z(38)>Z(50)>gamma-Al2O3. Stronger acidity gave higher DME hydrolysis conversion. Physical mixtures containing a CuO-ZnO-Al2O3-ZrO2 catalyst and solid acid catalyst to couple DME hydrolysis and methanol SR were used to examine the acidity effects on DME SR. DME SR activity strongly depended on the activity for DME hydrolysis. Z(25) was the best solid acid catalyst for DME SR and gave a DME conversion>90% [T=240 degrees C, n(H2O)/n(DME) = 3.5, space velocity = 1179 ml.(g cat)(-1).h(-1), and P = 0.1MPa]. The influences of the reaction temperature, space velocity and feed molar ratio were studied. Hydrogen production significantly depended on temperature and space velocity. A bifunctional catalyst of CuO-ZnO-Al2O3-ZrO2 catalyst and ZSM-5 gave a high H-2 production rate and CO2 selectivity.