Exhaust gas purification comprises use of nitrogen oxide adsorption/discharge agent supported by oxidizing particle filter, where exhaust gas air/fuel ratio is raised to recover agent from sulfur poisoning

摘要

When the adsorption/discharge agent is poisoned by sulfur, the air/fuel ratio of the exhaust gas through the filter (22) is raised to a first, rich level if the quantity of particles in the filter is below a set value and to a second, richer value if the quantity of particles is above this value The adsorption/discharge agent captures the nitrogen oxide (NOx) when there is excess oxygen in the environment and discharges it when the ambient oxygen concentration drops. The order to recover from sulfur poisoning is sent with a set air/fuel ratio and the quantity of particles in the filter is detected on the basis of a change of temperature of the filter during the recovery. A noble metal catalyst is deposited on the particle filter, together with an agent of active oxygen release. This captures and holds oxygen when there is excess oxygen in the environment and releases it when the concentration of ambient oxygen drops, or when the particles adhering to the filter are oxidized. This agent of active oxygen release is an alkali metal, an alkali earth metal, a rare earth metal, a transition metal or an element of the carbon group. The alkali and alkali earth metals have a higher tendency to ionize than calcium.