NOx decreasing apparatus for an internal combustion engine
AssigneesToyota Jidosha Kabushiki Kaisha, Kabushiki Kaisha Toyota Chuo Kenkyusho
InventorsYujiro Oshima, Hideaki Muraki, Koji Yokota, Kiyoshi Nakanishi
Life of this patent
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Abstract
A lean NOx reduction catalyst capable of reducing NOx through reaction of H.sub.2 with NOx at low temperatures below 350.degree. C. is installed in a downstream portion of an exhaust pipe of an internal combustion engine in or near a muffler. Such an NOx reduction catalyst comprises, for example, Pt/zeolite catalyst. An H.sub.2 generator is installed so as to supply the H.sub.2 to an inlet side of the NOx reduction catalyst. The H.sub.2 generator may include a reforming catalyst for reforming methanol, LPG, or natural gas to generate H.sub.2. The generated H.sub.2 flows to the NOx reduction catalyst where it reacts with NOx to purify the exhaust gas.
Claims27
An NO.sub.x decreasing apparatus for an internal combustion engine comprising:
- an internal combustion engine capable of fuel combustion at lean air-fuel ratios, the engine having an exhaust conduit, an upstream end of which is connected to the engine, and an exhaust muffler installed in the exhaust conduit;
- an NO.sub.x reduction catalyst installed at a downstream, low temperature location in the exhaust conduit, the NO.sub.x reduction catalyst being a zeolite catalyst capable of causing H.sub.2 to selectively react NO.sub.x at temperatures lower than 300.degree. C. under a predetermined engine running condition, wherein the predetermined engine running condition includes an excess oxygen condition, to thereby decompose the NO.sub.x into N.sub.2 and H.sub.2 O;
- an H.sub.2 generator for generating H.sub.2, the H.sub.2 generator including an inner core constructed of a tube inserted in the exhaust conduit, an electro-magnetic valve for injecting one of methanol and hydrocarbons into one end of the tube, and a reforming catalyst housed in the inner core;
- and
- means for supplying the generated H.sub.2 to an inlet side of the NO.sub.x reduction catalyst, wherein the means for supplying the generated H.sub.2 comprises a mixer for mixing H.sub.2 with exhaust gas from the engine, wherein the mixer is located in the exhaust conduit at an inlet side of the NO.sub.x reduction catalyst.
Dependencies are inferred from the claim text.