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

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