Exhaust gas purification apparatus for an internal combustion engine
AssigneeToyota Jidosha Kabushiki Kaisha
InventorsKenji Katoh, Satoshi Iguchi, Tetsuro Kihara
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Abstract
An exhaust gas purification system includes a transition metal/zeolite first catalyst, a three-way second catalyst, and a noble metal-type third catalyst arranged in that order in the direction of exhaust gas flow in an exhaust conduit of an internal combustion engine capable of fuel combustion at lean air-fuel ratios. NOx which has not been purified by the transition metal/zeolite first catalyst is oxidized by the three-way second catalyst into NO.sub.2, which the noble metal-type third catalyst can easily decompose into N.sub.2 and O.sub.2.
Claims10
An exhaust gas purification apparatus for an internal combustion engine comprising:
- an internal combustion engine capable of fuel combustion at lean air-fuel ratios;
- an exhaust conduit, an upstream end of which is connected to the internal combustion engine, wherein exhaust gas from the internal combustion engine enters the exhaust conduit at the upstream end and travels through the exhaust conduit to a downstream end thereof;
- an NO.sub.x reducing transition metal/zeolite first catalyst installed in the exhaust conduit and including a transition metal deposited on a zeolite carrier;
- a three-way second catalyst installed downstream of the transition metal/zeolite catalyst in the exhaust conduit, wherein the three-way second catalyst is capable of oxidizing NO into NO.sub.2 ;
- and
- an NO.sub.2 reducing noble metal-type third catalyst installed downstream of the three-way catalyst in the exhaust conduit and including a noble metal deposited on a carrier.
Dependencies are inferred from the claim text.