Generating hydrogen-rich fuel-cell feeds from dimethyl ether (DME) using physical mixtures of a commercial Cu/Zn/Al2O3 catalyst and several solid-acid catalysts

Homogeneous physical mixtures containing a commercial Cu/ZnO/Al2O3 catalyst and a solid-acid catalyst were used to examine the acidity effects on dimethyl ether hydrolysis and their subsequent effects on dimethyl ether steam reforming (DME-SR). The acid catalysts used were zeolites Y [Si/Al = 2.5 and 15: denoted Y(Si/Al)], ZSM-5 [Si/Al = 15, 25, 40, and 140: denoted Z(Si/Al)] and other conventional catalyst supports (ZrO2, and gamma-Al2O3). The homogeneous physical mixtures contained equal amounts, by volume, of the solid-acid catalyst and the commercial Cu/ZnO/Al2O3 catalyst (BASF K3-110, denoted as K3). The steam reforming of dimethyl ether was carried out in an isothermal packed-bed reactor at ambient pressure. The most promising physical mixtures for the low-temperature production of hydrogen from DME contained ZSM-5 as the solid-acid catalyst, with hydrogen yields exceeding 90% (T = 275 degrees C, SIC = 1.5, tau = 1.0 s and P = 0.78 atm) and hydrogen selectivities exceeding 94%, comparable to those observed for methanol steam reforming (MeOH-SR) over BASF K3-110, with values equaling 95% and 99%, respectively (T = 225 degrees C, S/ C = 1.0, tau = 1.0 s and P = 0.78 atm). Large production rates of hydrogen were directly related to the type of acid catalyst used. The hydrogen production activity trend as a function of physical mixture was [GRAPHICS] (c) 2006 Elsevier B.V. All rights reserved.