Exhaust gas purification system for an internal combustion engine
First Claim
1. An exhaust gas purification system for an internal combustion engine comprising:
- an internal combustion engine capable of fuel combustion at lean air-fuel ratios and having an exhaust conduit;
a catalyst installed in the exhaust conduit of the engine and constructed of zeolite, said catalyst carrying at least one metal selected from the group consisting of transition metals and noble metals to reduce nitrogen oxides included in exhaust gas from the engine under oxidizing gas conditions and in the presence of hydrocarbons;
means for determining degradation of the catalyst; and
means for increasing the amount of hydrocarbons supplied to the catalyst when the means for determining degradation of the catalyst determines that the catalyst has been degraded.
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Accused Products
Abstract
An exhaust gas purification system for an internal combustion engine includes an engine capable of fuel combustion at lean air-fuel ratios, a catalyst constructed of zeolite carrying at least one metal selected from the transition metals and noble metals to reduce NOx under oxidizing gas conditions and in the presence of HC. The exhaust gas purification system also includes a device for determining degradation of the catalyst, and a device for increasing the amount of HC or changing a catalyst temperature to a higher side when it is determined that the catalyst has been degraded. The NOx purification rate of the catalyst is maintained high even after the catalyst has been degraded.
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Citations
22 Claims
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1. An exhaust gas purification system for an internal combustion engine comprising:
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an internal combustion engine capable of fuel combustion at lean air-fuel ratios and having an exhaust conduit; a catalyst installed in the exhaust conduit of the engine and constructed of zeolite, said catalyst carrying at least one metal selected from the group consisting of transition metals and noble metals to reduce nitrogen oxides included in exhaust gas from the engine under oxidizing gas conditions and in the presence of hydrocarbons; means for determining degradation of the catalyst; and means for increasing the amount of hydrocarbons supplied to the catalyst when the means for determining degradation of the catalyst determines that the catalyst has been degraded. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An exhaust gas purification system for an internal combustion engine comprising:
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an internal combustion engine capable of fuel combustion at lean air-fuel ratios and having an exhaust conduit; a catalyst installed in the exhaust conduit of the engine and constructed of zeolite, said catalyst carrying at least one metal selected from the group consisting of transition metals and noble metals to reduce nitrogen oxides included in exhaust gas from the engine under oxidizing gas conditions and in the presence of hydrocarbons; means for determining degradation of the catalyst; and means for changing a catalyst temperature to a higher side when the means for determining degradation of the catalyst determines that the catalyst has been degraded. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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Specification