S. Velu et al., Selective production of hydrogen by partial oxidation of methanol over catalysts derived from CuZnAl-layered double hydroxides, CATAL LETT, 62(2-4), 1999, pp. 159-167
Hydrogen production by partial oxidation of methanol (POM) reaction (CH3OH
+ (1/2)O-2 reversible arrow 2H(2) + CO2) was investigated over a series of
CuZnAl ternary oxide catalysts derived from CuZnAl hydroxycarbonate precurs
ors containing hydrotalcite-like layered double hydroxide as a major phase.
These catalysts exhibited a good catalytic activity and high H-2 selectivi
ty. A methanol conversion of about 40-60% was obtained at 200(degrees)C wit
h high selectivity of H-2 and CO2. The undesirable by-product, CO was virtu
ally not produced over most of the catalysts at this temperature. The catal
ytic activity was found to decrease with increasing (Cu+Zn)/Al atomic ratio
in the precursor and, was correlated with Cu metal surface areas, Cu dispe
rsion and Cu particle sizes, which were calculated by both XRD and TPR-N2O
passivation methods. The catalyst with higher Cu surface areas and Cu dispe
rsion displayed a higher catalytic activity. Lifetime experiments showed th
at these catalysts were stable over a period of 24 h of continuous operatio
n. Catalyst precursors containing hydroxycarbonates other than LDH as a maj
or phase offered considerable amount of dimethyl ether as a by-product.