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

Abstract

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.