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

Fuel cell powered vehicles using hydrogen (H2) as a fuel are currently being developed in an effort to mitigate the emissions of green house gases such as CO2, NOx, and hydrocarbons. The H2 fuel is extracted from methanol onboard a vehicle by steam reforming of methanol (SRM) reaction. A considerable amount of CO is produced as a by-product, which is a poison to the Pt anode of the fuel cell. Very recently, we have demonstrated that a combined SRM and partial oxidation of methanol (POM), which we labeled as “oxidative steam reforming of methanol (OSRM)” reaction is more efficient for the selective production of H2 relatively at a lower temperature of around 230°C over CuZnAl(Zr)-oxide catalysts derived from hydroxycarbonate precursors containing hydrotalcite (HT)-like layered double hydroxides (LDHs)/aurichalcite phases. There are several operating parameters such as catalyst composition, reaction temperature, O2/CH3OH and H2O/CH3OH molar ratios and methanol injection rate that are need to be optimized in order to produce H2 suitable for fuelling a fuel cell. In the present study, we have investigated the effect of these variable parameters on the catalytic performance over a series of CuZnAl- and CuZnAlZr-oxide catalysts. Our study indicated that among the CuZn-based catalysts, those containing Zr were the most active. The optimum O2/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 catalytic performance over a Zr-containing catalyst revealed that the OSRM reaction proceeds through the formation of formaldehyde intermediate. CO was produced as a secondary product by the decomposition of formaldehyde and it is subsequently transformed into CO2 and H2 by the water-gas shift (WGS) reaction.