Reducing NOx emissions with a staged catalyst
AssigneeGeneral Motors Corporation
InventorJong-Hwan Lee
Life of this patent
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Abstract
The conversion of NOx to nitrogen in the exhaust of a lean burn engine using a hydrocarbon assisted-selective catalytic reduction system is benefited by a two-stage oxidation catalyst-reduction catalyst SCR reactor. The character and quantity of the oxidation catalyst is managed to just activate the hydrocarbon reductant at low temperatures (but not fully burn it at high temperatures) to increase its NOx reduction efficiency as the exhaust then contacts the larger reduction catalyst stage of the two-stage reactor.
Claims12
A method of converting NOx content of the exhaust gas of a lean-burn engine to nitrogen where the exhaust comprises NO and NO2, the method comprising:
- passing the exhaust through a catalytic reactor comprising an upstream stage of an oxidation catalyst for the hydrocarbon content of the exhaust and an adjacent, but separate, downstream stage of a reduction catalyst for NOx and the reaction product of the first reactor stage, the space velocity of the exhaust gas with respect to said upstream stage being sufficiently high so as to activate the hydrocarbon content of the exhaust without consuming it by combustion.
Dependencies are inferred from the claim text.