Selective catalytic reduction catalyst system
AssigneeBASF SE
InventorWeiyong Tang
Life of this patent
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Abstract
Described are SCR catalyst systems comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition promoting higher N2 formation and lower N2O formation than the second SCR catalyst composition, and the second SCR catalyst composition having a different composition than the first SCR catalyst composition, the second SCR catalyst composition promoting lower N2 formation and higher N2O formation than the first SCR catalyst composition. The SCR catalyst systems are useful in methods and systems to catalyze the reduction of nitrogen oxides in the presence of a reductant.
Claims20
A selective catalytic reduction (SCR) catalyst system comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition promoting higher N2 formation and lower N2O formation than the second SCR catalyst composition, and the second SCR catalyst composition having a different composition than the first SCR catalyst composition, the second SCR catalyst composition promoting lower N2 formation and higher N2O formation than the first SCR catalyst composition,
- wherein the first SCR catalyst composition is in the form of a first washcoat;
- wherein the second SCR catalyst composition is in the form of a second washcoat;
- wherein the first washcoat and the second washcoat are coated on one or more substrates in a laterally zoned configuration such that the first SCR catalyst composition is located laterally upstream of the second SCR catalyst composition according to a flow direction of an engine exhaust gas stream from an engine towards a tailpipe;
- wherein the first SCR catalyst composition comprises a mixed oxide comprising vanadia/titania;
- and
- wherein the second SCR catalyst composition comprises a metal-exchanged zeolite, excluding Cu-exchanged or Fe-exchanged ZSM-5 or Beta zeolites;
- wherein the SCR catalyst system provides an improved NOx conversion efficiency as compared to a SCR catalyst system comprising the first SCR catalyst composition and substantially free of the second SCR catalyst composition;
- and
- wherein the SCR catalyst system provides a lower N2O formation as compared to a SCR catalyst system comprising the second SCR catalyst composition and substantially free of the first SCR catalyst composition.
A selective catalytic reduction (SCR) catalyst system comprising a first SCR catalyst composition comprising vanadia/titania disposed on a substrate and a second SCR catalyst composition comprising a metal-exchanged 8-ring small pore molecular sieve disposed on a substrate,
- wherein the first SCR catalyst composition is in the form of a first washcoat;
- wherein the second SCR catalyst composition is in the form of a second washcoat;
- wherein the first washcoat and the second washcoat are coated on one or more substrates in a laterally zoned configuration such that the first SCR catalyst composition is located laterally upstream of the second SCR catalyst composition according to a flow direction of an engine exhaust gas stream from an engine towards a tailpipe;
- wherein the metal-exchanged 8-ring small pore molecular sieve is a metal-exchanged zeolite, excluding Cu-exchanged or Fe-exchanged ZSM-5 or Beta zeolites;
- wherein the SCR catalyst system provides an improved NOx conversion efficiency as compared to a SCR catalyst system comprising the first SCR catalyst composition and substantially free of the second SCR catalyst composition;
- and
- wherein the SCR catalyst system provides a lower N2O formation as compared to a SCR catalyst system comprising the second SCR catalyst composition and substantially free of the first SCR catalyst composition.
Dependencies are inferred from the claim text.