| abstract |
(57) [Summary] To improve the NOx purification performance of a NOx trap catalyst 5. SOLUTION: A NOx trap catalyst 5 includes a support material obtained by mixing alumina particles and Pr 6 O 11 particles with a noble metal (Pt, Rh) and a NOx trap material (Ba, K, M). g, Sr), and the catalyst 5 is provided in the exhaust passage 3 of the engine 1, and the exhaust gas of the engine when the operation at the air-fuel ratio lean and the operation at the air-fuel ratio rich are alternately repeated. Is brought into contact with the catalyst 5. |