| 摘要 |
PURPOSE:To purify even the concd. exhaust gas of a lean-burn engine contg. excess oxygen and NOx by selectively reducing the NOx. CONSTITUTION:An exhaust gas contg. a reducing component including hydrocarbons, an excess of oxygen over the stoichiometric amt. necessary to completely oxidize the reducing component and NOx is brought into contact with a catalyst capable of selectively reducing the NOx to nitrogen and purified. In this case, the hydrocarbon concn. in the exhaust gas is controlled before contact of the exhaust gas with the catalyst so that the concn. ratio (molar ratio) of hydrocarbons to oxygen is kept at 0.05 to 0.2. |
