Selective adsorption of NOx from hot combustion gases by Ce-doped CuO/TiO2

CuO/TiO2 has been shown to be a superior sorbent for selective, reversible adsorption of NO from hot combustion gases. High NOx adsorption capacities at 200 and 300 degrees(C) were obtained with a 5% CuO/TiO2 sorbent, and the NOx desorbed rapidly at 450 degrees C. Doping with 2% Ce an the CuO/TiO2 sorbent further increased both uptake rates (50% increase in initial rate) and NOx capacity (by 30%). in a direct comparison with the most promising known sorbent, MnO/ZrO2 (1:1 molar ratio), reported by Eguchi et al. (J. Catal. 1996, 158, 420), the Ce-CuO/TiO2 sorbent showed both higher uptake rates (by 100% in initial rate) and higher NOx capacity (by 15%). The effects of CO2, H2O, and SO2 on NOx sorption on the Ce-CuO/TiO2 sorbent were studied at 200 degrees C. CO2 slightly decreased the initial uptake rate but increased the NOx capacity. H2O coadsorbed with NOx on different sites, both reversibly (i.e. desorbed at 450 degrees C). SO2 irreversibly adsorbed (likely to sulfate the surface of TiO2) and decreased the NOx capacity by approximately 20%. The BET surface area of the TiO2 support was 50 m(2)/g. Further studies with TiO2 of higher surface areas are in progress.