Performance of Ba-doped Ir/WO3-SiO2 Catalyst for Selective Catalytic Reduction of NOx with CO in Diesel Exhaust

摘要

Ba-doped Ir/WO3-SiO2 catalyst has high activity and good durability for the selective catalytic reduction of NO with CO in the presence of O2 (CO-SCR). The performance of this catalyst was investigated for real diesel exhaust. In addition, the possibility of a combined catalytic system using CO-SCR and NH3-SCR was evaluated. Ba/Ir/ WO3-SiO2 catalyst provided more than 45% conversion with 3000 ppm CO at 280°C under SV (space velocity) <6000 h~(-1) even with high oxygen concentrations. The activity of a combined catalyst system using Cu-BEA for NH3-SCR and Ba/Ir/WO3-SiO2 for CO-SCR was evaluated. The combined catalyst provided about 60% NO_x conversion when only NH3 was added. NO_x conversion was further increased with the addition of 3000 ppm CO. Thus, the efficiency of the combined system was confirmed. Improvement of activity under high space velocity and prevention of catalyst deactivation by smoke are the key targets for the development of practical systems.