| 摘要 |
PROBLEM TO BE SOLVED: To improve durability of a repeatedly used a device which reduces and purifies NOx in exhaust gas while bringing a lean air-fuel ratio of exhaust gas and a rich air-fuel ratio of exhaust gas into alternate contact with an NOx purifying catalyst, by using a catalyst showing an absorption spectrum in a caught condition of NO2. SOLUTION: This internal combustion engine is operated such that an exhaust gas atmosphere is alternately subjected to an oxidized atmosphere and a reduced atmosphere, and NOx in exhaust gas is purified by an NOx purifying catalyst 18. In such an exhaust gas emission control method, a catalyst for showing the absorption spectrum of a captured condition of NO2 is used, when an NOx catching condition is measured by an infrared absorption spectrum (FT-IR). The NOx is captured on an NOx catching material surface as NO2, without taking NOx in the NOx catching material as a nitric acid compound. As a catalyst for use, a noble metal and a material having an NOx capturing material including alkali metal or alkali earth metal are preferable. |
