US 5,746,052 A · Exhaust gas purification device for an engine

Abstract

In the present invention, the exhaust gas from the engine is divided into a first and a second branch exhaust passages after it passes through a three-way reducing and oxidizing catalyst, and the two branch exhaust passages merge into an exhaust gas outlet passage. In the first branch exhaust passage, an oxidizing catalyst is disposed, and in the exhaust gas outlet passage, a denitrating and oxidizing catalyst is disposed. NO.sub.x in the exhaust gas from the engine is all converted to N.sub.2 and NH.sub.3 by the three-way reducing and oxidizing catalyst and a part of the NH.sub.3 generated by the three-way catalyst flows into the first branch exhaust passage and is converted to NO.sub.x again by the oxidizing catalyst. The amount of NO.sub.x produced by the oxidizing catalyst and the amount of NO.sub.x flowing through the second branch exhaust passage is determined by the flow distribution ratio of the first and the second branch exhaust passages. In this invention, the flow ratio is determined in such a manner that the amount of the NO.sub.x produced by the oxidizing catalyst and the amount of the NH.sub.3 passing through the second branch exhaust passage are stoichiometric to produce N.sub.2 and H.sub.2 O. Therefore, when these exhaust gases flow into the denitrating and oxidizing catalyst after they mix with each other in the exhaust gas outlet passage, all the NO.sub.x and the NH.sub.3 are converted to N.sub.2 and H.sub.2 O by the denitrating and oxidizing catalyst without producing any surplus NO.sub.x or NH.sub.3.

Claims27

Dependent claims

An exhaust gas purification device for an internal combustion engine comprising:

a ratio determining means disposed in an exhaust gas passage of an internal combustion engine for converting substantially all of NO.sub.x in the exhaust gas into N.sub.2, NH.sub.3 and NO.sub.x, wherein an amount of NH.sub.3 and an amount of NO.sub.x generated by the conversion are adjusted so that the amount of NH.sub.3 and the amount of NO.sub.x are stoichiometrical, and wherein the NO.sub.x generated by the conversion is essentially NO.sub.2 and a molar ratio of the amount of NO.sub.2 generated to the amount of NH.sub.3 generated is 3:4;
and
purification means disposed in the exhaust gas passage downstream of the ratio determining means for causing the NH.sub.3 generated to react with NO.sub.x generated to produce N.sub.2 and H.sub.2 O components.

Dependencies are inferred from the claim text.

Exhaust gas purification device for an engine

Life of this patent

Exhaust gas purification device for an engine

Life of this patent

Abstract

Claims27