Selective Adsorption of NOxfrom Hot Combustion Gases by Ce-Doped CuO/TiO2

Abstract

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 °C were obtained with a 5% CuO/TiO2 sorbent, and the NOx desorbed rapidly at 450 °C. Doping with 2% Ce on 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 °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 °C). SO2 irreversibly adsorbed (likely to sulfate the surface of TiO2) and decreased the NOx capacity by approxim...