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.