Emission control
AssigneeJohnson Matthey Public Limited Company
InventorsMartyn Vincent Twigg, Anthony John Joseph Wilkins, Nigel Simon Will
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Abstract
An emission control system especially for light duty diesel engines has a first catalyst, 2, positioned upstream of a second catalyst, 3. The first catalyst converts NO to NO2 and the second catalyst oxidises HC, CO and VOF. The tendency of the second catalyst to collect soot particles is reduced by combustion of the soot particles by NO2 from the first catalyst.
Claims19
An emission control system for internal combustion engines which emit carbonaceous soot particles, which system comprising a first catalyst effective to oxidize NOx to NO2 and a second catalyst effective to oxidize hydrocarbons, carbon monoxide and volatile organic fractions, each catalyst being supported on a honeycomb flow-through monolith, whereby soot particles trapped on or within said second catalyst are combusted in the NO2 containing gas from said first catalyst, and wherein the first catalyst is supported on a flexible metal monolith of up to 31 cells/cm2, whereby soot particle collection on the first catalyst support is minimized.
In a process for the purification of exhaust gases from a light duty internal combustion engine which emits carbonaceous soot particles by passing said gases over a honeycomb flow-through monolith and an oxidation catalyst effective at least to oxidize HC, CO and VOF, the improvement comprising first passing said gases over a first catalyst effective to oxidize NOx to NO2 and subsequently passing the gas enriched with NO2 over said honeycomb flow-through monolith and oxidation catalyst in order to enhance catalytic oxidation of soot particles trapped on or within said oxidation catalyst.
An emission control system for an internal combustion engine which emits carbonaceous soot particles, which system comprising a first catalyst effective to oxidize NOx to NO2 and a second catalyst effective to oxidize hydrocarbons, carbon monoxide and volatile organic fractions, each catalyst being supported on a honeycomb flow-through monolith, the cell density and dimensions of said respective monoliths being selected to provide a greater space velocity over said first catalyst than over said second catalyst whereby soot particle collection on the first catalyst support is minimized and whereby soot particles trapped on or within said second catalyst are combusted in the NO2 containing gas from said first catalyst.
Dependencies are inferred from the claim text.