Selective production of hydrogen for fuel cells via oxidative steam reforming of methanol over CuZnAl(Zr)-oxide catalysts

Fuel cell powered vehicles using hydrogen (Hz) as a fuel are currently bein g developed in an effort to mitigate the emissions of green house gases suc h as CO2, NOx, and hydrocarbons. The H-2 fuel is extracted from methanol on board a vehicle by steam reforming of methanol (SRM) reaction. A considerab le amount of CO is produced as a by-product, which is a poison to the Pt an ode of the fuel cell. Very recently, we have demonstrated that a combined S RM and partial oxidation of methanol (POM), which we labeled as "oxidative steam reforming of methanol (OSRM)" reaction is more efficient for the sele ctive production of II? relatively at a lower temperature of around 230 deg reesC over CuZnAl(Zr)-oxide catalysts derived from hydroxycarbonate precurs ors containing hydrotalcite (HT)-like layered double hydroxides (LDHs)/auri chalcite phases. There are several operating parameters such as catalyst co mposition, reaction temperature, O-2/CH3OH and H2O/CH3OH molar ratios and m ethanol injection rate that are need to be optimized in order to produce Hz suitable for fuelling a fuel cell. In the present study, we have investiga ted the effect of these variable parameters on the catalytic performance ov er a series of CuZnAl-and CuZnAlZr-oxide catalysts. Our study indicated tha t among the CuZn-based catalysts, those containing Zr were the most active. The optimum O-2/CH3OH and H2O/CH3OH molar ratios should be in the ranges 0 .20-0.30 and 1.3-1.6, respectively, in order to achieve a better catalytic performance. Studies of the effect of methanol contact time on the catalyti c performance over a Zr-containing catalyst revealed that the OSRM reaction proceeds through the formation of formaldehyde intermediate. CO was produc ed as a secondary product by the decomposition of formaldehyde and it is su bsequently transformed into CO2 and ii by the water-gas shirt (WGS) reactio n. (C) 2001 Elsevier Science B.V. All rights reserved.