| 摘要 |
PURPOSE:To efficiently purify NOx by arranging the crystalline silicate loaded with copper in the fore stage of an exhaust gas passage, arranging a three- component catalyst in series in the rearstage, and excessively adding fuel in a moment in a special case. CONSTITUTION:An exhaust emission control device is installed in the exhaust gas passage of a lean burn engine 1. A crystalline silicate catalyst loaded with copper is arranged in the forestage of the exhaust gas passage, and a three- component catalyst is arranged in the rearstage. The three-component catalyst consists of alumina carrier loaded with Pt and Rh. A throttle 5 and an air cleaner 6 are arranged on the suction side of the lean burn engine 1. An oxygen concentration sensor 2 is arranged on an exhaust side. When the exhaust gas composition changes from a lean state to a stoichio state, fuel is added excessively in a moment. Accordingly, NOx can be purified efficiently in any gas state. |
