Selective production of hydrogen by partial oxidation of methanol over catalysts derived from CuZnAl‐layered double hydroxides

Abstract

Hydrogen production by partial oxidation of methanol (POM) reaction (CH3OH + (1/2)O2 ⇌ 2H2 + CO2) was investigated over a series of CuZnAl ternary oxide catalysts derived from CuZnAl hydroxycarbonate precursors containing hydrotalcite‐like layered double hydroxide as a major phase. These catalysts exhibited a good catalytic activity and high H2 selectivity. A methanol conversion of about 40–60% was obtained at 200°C with high selectivity of H2 and CO2. The undesirable by‐product, CO was virtually not produced over most of the catalysts at this temperature. The catalytic activity was found to decrease with increasing (Cu + Zn)/Al atomic ratio in the precursor and, was correlated with Cu metal surface areas, Cu dispersion and Cu particle sizes, which were calculated by both XRD and TPR‐N2O passivation methods. The catalyst with higher Cu surface areas and Cu dispersion displayed a higher catalytic activity. Lifetime experiments showed that these catalysts were stable over a period of 24 h of continuous operation. Catalyst precursors containing hydroxycarbonates other than LDH as a major phase offered considerable amount of dimethyl ether as a by‐product.