A comparative study of N2O conversion to N-2 over Co/AC and Cu/AC catalysts

Catalytic conversion of N2O to N-2 over Cu- and Co-impregnated activated ca rbon catalysts (Cu/AC and Co/AC) was investigated. Catalytic activity measu rements were carried out in a fixed-bed flow reactor at atmospheric pressur e. The catalysts were characterized by N-2 adsorption, X-ray diffraction (X RD) and thermogravimetric analysis (TGA). This study aimed to provide insig hts into the following aspects: the metal dispersion, changes in pore struc ture, influence of catalyst loading on reaction, and reaction mechanism. In creasing loading of Co or Cu led to decreasing dispersion, but 20 wt % load ing was an upper limit for optimal activities in both cases, with too high loading causing sintering of metal. Co exhibited a relatively better disper sion than Cu. Impregnation of metal led to a large decrease in surface area and pore volume, especially for 30 wt % of loading. 20 wt % of loading has proved to be the optimum for both Cu and Co, which shows the highest activ ity. Both N2O-Co/AC and -Cu/AC reactions are based upon a redox mechanism, but the former is limited by the oxygen transfer from catalysts to carbon, while N2O chemisorption on the surface of Cu catalyst controls the latter. The removal of oxygen from cobalt promotes the activity of Co/AC, but it is beneficial for Cu/AC to keep plenty of oxygen to maintain the intermediate oxidation of copper-Cu1+. The different nature of the two catalysts and th eir catalytic reaction mechanisms are closely related to their different el ectronegativities.