Catalyst system for converting emissions of a lean-burn engine
First Claim
1. A method of treating the emission from a fossil-fueled engine, using lean-burn combustion, the emission having an oxygen content of 1.5-10% O2, the method comprising:
- (a) injecting a hydrocarbon reductant selected from the group consisting of straight chain, branched chain, or aromatic hydrocarbons or oxygenated compounds, said hydrocarbon reductant being injected into the catalyst stream entering a first stage nitric oxide reduction catalyst comprised of highly acidic gamma alumina;
(b) exposing the injected stream to the nitric oxide reduction catalyst; and
(c) exposing the effluent from the reducing catalyst to an oxidation catalyst.
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Abstract
A catalyst system for attaining high conversions of NO, HC, and CO in a fuel-lean emission flow (i.e., containing SO2, H2 O, H2, and considerable excess oxygen), the system comprising: (a) a first stage reducing catalyst for treating the nitric oxide emissions, the catalyst containing highly acidic gamma alumina (i.e., with a pHpzc of less than 3); (b) means for injecting gaseous or liquid reductants into the emission stream prior to entering said first stage catalyst, said first stage catalyst temperature being selected to be in the range of 550°-650° C.; and (c) an oxidation catalyst effective for treating the effluent from the first stage catalyst.
Another aspect of this invention is a method of treating the exhaust gas from a fuel-lean emission flow from a fossil-fueled internal combustion engine having a redox ratio of 0.02-0.09, the method comprising: (a) injecting a gaseous or liquid HC or oxygenated HC reductant into the emission stream at a location where the stream is within the temperature range of 550°-650° C.; (b) immediately exposing the injected stream to a first stage catalyst containing acidic gamma alumina with a Phpzc of less than 3; and (c) exposing the effluent from the first stage catalyst to an oxidation catalyst that is effective in ensuring that the NO, HC, and CO in the emissions are each converted to at least 80%.
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8 Claims
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1. A method of treating the emission from a fossil-fueled engine, using lean-burn combustion, the emission having an oxygen content of 1.5-10% O2, the method comprising:
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(a) injecting a hydrocarbon reductant selected from the group consisting of straight chain, branched chain, or aromatic hydrocarbons or oxygenated compounds, said hydrocarbon reductant being injected into the catalyst stream entering a first stage nitric oxide reduction catalyst comprised of highly acidic gamma alumina; (b) exposing the injected stream to the nitric oxide reduction catalyst; and (c) exposing the effluent from the reducing catalyst to an oxidation catalyst. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification