Exhaust gas purification device for an engine

Power plants – Internal combustion engine with treatment or handling of... – Material from exhaust structure fed to engine intake

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Details

60285, 60289, F01N 320, F02M 2506, F02N 300

Patent

active

054488877

ABSTRACT:
An exhaust gas purification device of the present invention includes a three-way reducing and oxidizing catalyst disposed on an exhaust passage of an engine, and an NO.sub.x absorbent which absorbs NO.sub.x in the exhaust gas when the air-fuel ratio of the exhaust gas is lean and releases absorbed NO.sub.x when the air-fuel ratio of the exhaust gas is rich; the engine in the present invention is controlled in most of its operating region in such a manner that the operating air-fuel ratio of the engine oscillates between a rich air-fuel ratio and a lean air-fuel ratio about a center value of a stoichiometric air-fuel ratio; when the operating air-fuel ratio of the engine becomes lean, the ability of the three-way catalyst for reducing NO.sub.x in the exhaust gas becomes low, and a part of NO.sub.x in the exhaust gas passes through the three-way catalyst, and, since the air-fuel ratio of the exhaust gas is lean, this NO.sub.x is absorbed in the NO.sub.x absorbent located downstream of the three-way catalyst; when the operating air-fuel ratio of the engine becomes rich, the ability of the three-way catalyst for oxidizing HC and CO in the exhaust gas becomes low, and a part of HC and CO in the exhaust gas passes through the three-day catalyst; since the air-fuel ratio of the exhaust gas is rich, absorbed NO.sub.x is released from the NO.sub.x absorbent and this NO.sub.x is reduced as HC and CO passes through the three-way catalyst; therefore, the pollutants such as HC, CO, NO.sub.x are almost completely removed.

REFERENCES:
patent: 5201802 (1993-04-01), Hirota
patent: 5209061 (1993-05-01), Takeshima
patent: 5271223 (1993-12-01), Hoshi
patent: 5331809 (1994-07-01), Takeshima et al.
NO Removal by Absorption into BA.sub.O -CuO Binary Oxides (J. Chem Soc. Chem Commun, pp. 1165-1166).
Formation and Decomposition of BaCuO.sub.2.5 Prepared from a Mixture of Nitrates (Journal of solid state chemistry pp. 176-179).
NO Removal by Absorption into Ba-Cu-O Binary Oxides (Catalyst vol. 33 No. 2 pp. 87-89).

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