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AssigneeToyota Jidosha Kabushiki Kaisha
InventorsYukio Kinugasa, Kouhei Igarashi, Takaaki Itou, Toshifumi Takaoka, Michihiro Ohashi, Koji Yokota
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The method for purifying combustion exhaust gas according to the present invention utilizes a NH.sub.3 decomposing catalyst. The NH.sub.3 decomposing catalyst in the present invention is capable of converting substantially all of the NH.sub.3 in the combustion exhaust gas to N.sub.2 when the air-fuel ratio of the exhaust gas is lean and the temperature of the catalyst is within a predetermined optimum temperature range. Further, when the exhaust gas contains NO.sub.x in addition to NH.sub.3, the NH.sub.3 decomposing catalyst is capable of reducing the NO.sub.x in the optimum temperature range even though the air-fuel ratio of the exhaust gas is lean. In the present invention, the conditions of the exhaust gas containing NO.sub.x are adjusted before it is fed to the NH.sub.3 decomposing catalyst in such a manner that the temperature of the exhaust gas is within the optimum temperature range and the air-fuel ratio of the exhaust gas is lean. Further, NH.sub.3 is added to the exhaust gas before it is fed to the NH.sub.3 decomposing catalyst. Therefore, a lean air-fuel ratio exhaust gas, at a temperature within the optimum temperature range, which contains both the NO.sub.x and NH.sub.3 is fed to the NH.sub.3 decomposing catalyst, and the NO.sub.x, as well as the NH.sub.3, in the exhaust gas is completely resolved by the NH.sub.3 decomposing catalyst.
A process for resolving NH.sub.3 included in a combustion exhaust gas including the steps of:
A process for resolving pollutants in exhaust gas of an internal combustion engine comprising:
A process for resolving NO.sub.x from a combustion exhaust gas using an NH.sub.3 decomposing catalyst which, in an oxidizing atmosphere with NH.sub.3 present, resolves NO.sub.x when the temperature of the catalyst is within a predetermined temperature range, converts NH.sub.3 to NO.sub.x when the temperature of the catalyst is higher than said predetermined temperature range, and allows NH.sub.3 to pass through the catalyst when the temperature of the catalyst is lower than said predetermined temperature range comprising:
Dependencies are inferred from the claim text.