| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a urea SCR (selective catalytic reduction) system preventing ammonia slip, enlarging a range of application temperature and solving a conventional problem. <P>SOLUTION: In the urea SCR system, a front stage oxidation catalyst part 3 for enhancing oxidation activity of NO in an exhaust gas from an upstream side of an exhaust passage 2 of an internal combustion engine 1, or the like, an SCR catalyst part 4 for reducing NOx in the exhaust gas by ammonia, and a rear stage oxidation catalyst part 5 for removing ammonia are successively arranged, and a urea water liquid 6 is added between the front stage oxidation catalyst part 3 and the SCR catalyst part 4. The SCR catalyst part is arranged in series by combining a low temperature catalyst carrier A of an adsorbent having weak acid strength and a high temperature catalyst carrier B of an adsorbent having strong acid strength. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
