Device for purifying exhaust gas, method for purifying exhaust gas, catalyst for purifying exhaust gas, and method for manufacturing exhaust gas purifying catalyst

摘要

A catalyst (25) for lowering NOx concentration in an exhaust gas is disposed in an exhaust gas passage (22) of an engine (1). The catalyst (25) is composed of a catalyst layer (25b) formed on a substrate (25a). A NOx absorber that absorbs NOx when an oxygen concentration in the exhaust gas is high and releases NOx when the oxygen concentration drops, and a precious metal for reducing NOx are supported on a support material as catalyst components, and the NOx absorber includes Ba, K, Sr, and Mg. By lowering the oxygen concentration in the exhaust gas and raising a temperature of the NOx absorber when sulfur component is absorbed excessively in the NOx absorber, it is possible to regenerate the catalyst from the S poisoning.