Highly dispersed copper catalysts for CO preferential oxidation in hydrogen-rich atmosphere

CeO2 and ZnO with finely rod shape were used as carriers to support copper. High-resolution transmission electron microscopy demonstrated that copper species were existed mostly in bilayer clusters containing underlying Cu+ and upper Cu0 on CeO2, but in big particles of 5-10 nm consisting of only Cu0 on ZnO. The amounts of underlying Cu+ in bilayers and oxygen vacancies (Ov) at copper-ceria interface reached maximum when copper loading was about 10 wt%. In CO preferential oxidation reaction, the 10-Cu/CeO2 catalyst showed the highest activity suggesting that CO adsorbed on Cu+ in bilayer clusters reacted rapidly with O2 absorbed on adjacent Ov. The near synergistic effect not only reduced the CO reaction temperature but also enhanced the CO conversion. The Cu/ZnO catalyst had weak CO adsorption and long distance of Cu0 and Ov, thus it showed much low activity. By filling the 10-Cu/CeO2 catalysts in a two-stage reactor, 1 % CO in the methanol steam reforming gas could be removed to 2 ppm after two successive CO oxidation processes, which provided a new solution for H2 purification.