| 摘要 |
PROBLEM TO BE SOLVED: To attain high NOX purification efficiency without adjusting exhaust to a rich air-fuel ratio by generating a low temperature oxidation reaction after supplying reductant, while retaining exhaust purification catalyst in a prescribed temperature range, and continuously producing reaction activated substance such that combustion exhaust at a specified air excess ratio is supplied. SOLUTION: A reductant supply device 20 for supplying liquid reductant is provided upstream of exhaust purification catalyst (RAP catalyst) 10 disposed in an exhaust passage 3. The RAP catalyst is obtained by carrying oxidized catalyst components, such as Pt and Pd on the multi-porous zeolite. A combustion state in an engine 1 is adjusted, such that an excess air ratio of the combustion exhaust flowing through the exhaust passage 3 becomes 1.0 or more. The flow rate of the reductant injected from a nozzle 23 is controlled by adjusting an opening degree of a control valve 25 in a control device 30. Furthermore, by allowing the exhaust temperature and excess air ratio to be within the range where a low-temperature oxidation reaction takes place on the catalyst, the reductant is converted into a radical and reacts preferentially with NOX in the exhaust, realizing high purification efficiency. |
