| 摘要 |
A system and method are disclosed for converting exhaust gas which comprises NOx, CO, and hydrocarbons, to innocuous products. Exhaust gas is contacted in undiverted flow with a zeolite suitable for adsorption of hydrocarbons, and with a main catalyst suitable for conversion of NOx, CO, and hydrocarbons to innocuous products. Adsorption occurs when the temperature of the zeolite is suitable therefor. Conversion occurs when the temperature of the main catalyst is suitable therefor. The zeolite and main catalyst are connected directly to one another, that is, in-line, without by-pass valving. The zeolite can be Y zeolite, Beta, ZSM-5, and combinations thereof, and has a SiO2 to Al2O3 mole ratio of no greater than about 200, and is ion exchanged with a metal which can be rare earth, chromium, and combinations thereof.
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