EXHAUST GAS PURIFYING DEVICE AND METHOD, EXHAUST GAS PURIFYING CATALYST AND PRODUCTION METHOD FOR EXHAUST GAS PURIFYING CATALYST

摘要

A catalyst (25) for reducing an NOx concentration in an exhaust gas is disposed in the exhaust passage (22) of an engine (1). The catalyst (25) comprises a catalyst layer (25b) formed on a carrier (25a). Catalyst components include, carried on a support material, an NOx absorbing material that absorbs NOx when an exhaust gas oxygen concentration is high, and releases NOx when the oxygen concentration is low, and a precious metal that reduce NOx, the NOx absorbing material comprising Ba, K, Sr and Mg. When an excessive sulfur component is absorbed in the NOx absorbing material, an exhaust gas oxygen concentration is lowered and the temperature of the NOx absorbing material is raised to thereby recover the catalyst from an S-poisoning.