| 摘要 |
PROBLEM TO BE SOLVED: To efficiently reduce, nitrogen oxide contained in exhaust gas. SOLUTION: A casing 3 having a first catalyst wherein platinum is supported on an alumina carrier housed therein, a casing 4 having a second catalyst wherein rhodium is supported on a ceria carrier housed therein and a casing 6 having a third catalyst wherein platinum, parallium or a combination of them is supported on an alumina carrier housed therein are successively arranged in an exhaust pipeline 2 from the upstream side in the flow direction of exhaust gas. A heating means 5 for heating the second catalyst is arranged in close vicinity to the second catalyst. A hydrocarbon type gas source 7 for supplying hydrocarbon type gas into the exhaust pipeline 2 communicates with the interior of the exhaust pipeline 2 on the upstream side of the first catalyst and at the intermediate part between the first and second catalysts and the supply amt. of the hydrocarbon type gas from the hydrocarbon type gas source 7 to the exhaust pipeline 2 is controlled by a flow rate control unit 8. |
