Improvement of SOx Durability and Heat Resistance for Lean NOx Catalyst

Sulfur oxides endurance and heat resistance of the conventional catalyst were improved from the studies using synthetic model gas and vehicle test. The NOx purification performance was improved for lean NOx catalyst deteriorated due to SOx poising. However, the trapped SOx could be removed with CO in rich gas at 600°C. Moreover, the SOx removal could be promoted with a SOx release material (γ1). On the other hand, heat resistance of the catalyst has been improved by using new mixed metal oxides (C) as a NO₂ adsorbent. The improved catalyst which contained γ1 and C showed superior heat resistance at 800°C and SOx durability compared to the conventional lean NOx catalyst in the model gas test. Also, in the vehicle test, the emission values of NOx, HC, and CO were 50% or less than J-ULEV regulation standards. These results show that the improved catalyst has a good purification performance of exhaust gas from a lean burn vehicle.