Sulfur Tolerance of Selective Partial Oxidation of NO to NO2 in a Plasma

Several catalytic aftertreatment technologies rely on the conversion of NO to NO₂ to achieve efficient reduction of NO_x and particulates in diesel exhaust. These technologies include the use of selective catalytic reduction of NO_x with hydrocarbons, NO_x adsorption, and continuously regenerated particulate trapping. These technologies require low sulfur fuel because the catalyst component that is active in converting NO to NO₂ is also active in converting SO₂ to SO₃. The SO₃ leads to increase in particulates and/or poison active sites on the catalyst. A non-thermal plasma can be used for the selective partial oxidation of NO to NO₂ in the gas-phase under diesel engine exhaust conditions. This paper discusses how a non-thermal plasma can efficiently oxidize NO to NO₂ without oxidizing SO₂ to SO₃.