A filter for filtering particulate matter (PM) from exhaust gas emitted from a compression ignition engine, which filter comprising a porous substrate having inlet surfaces and outlet surfaces, wherein the inlet surfaces are separated from the outlet surfaces by a porous structure containing pores o
A filter for filtering particulate matter (PM) from exhaust gas emitted from a compression ignition engine, which filter comprising a porous substrate having inlet surfaces and outlet surfaces, wherein the inlet surfaces are separated from the outlet surfaces by a porous structure containing pores of a first mean pore size, wherein the porous substrate is coated with a wash coat comprising a plurality of solid particles comprising a molecular sieve promoted with at least one metal wherein the porous structure of the wash coated porous substrate contains pores of a second mean pore size, and wherein the second mean pore size is less than the first mean pore size.
대표청구항▼
1. A filter for filtering particulate matter (PM) from exhaust gas emitted from a compression ignition engine, which filter comprising a porous substrate having inlet surfaces and outlet surfaces and substrate pores of a first mean pore size, wherein the porous substrate is coated with a washcoat la
1. A filter for filtering particulate matter (PM) from exhaust gas emitted from a compression ignition engine, which filter comprising a porous substrate having inlet surfaces and outlet surfaces and substrate pores of a first mean pore size, wherein the porous substrate is coated with a washcoat layer comprising a molecular sieve promoted with at least one transition metal wherein the washcoat layer is present as a non-permeating porous coating on said inlet or outlet surfaces and the layer contains pores of a second mean pore size, and wherein the second mean pore size which is less than the first mean pore size, and wherein both the inlet and the outlet surfaces are washcoated and wherein the inlet surfaces washcoat has a mean pore size that is less than the outlet surfaces washcoat. 2. A filter according to claim 1, wherein the first mean pore size is from 8 to 45 μm and the second mean pore size is from 5.0 nm to 5.0 μm. 3. A filter according to claim 1, wherein the washcoat layer loading is >0.50 g/in3. 4. A filter according to claim 3, wherein the washcoat layer loading is >1.00 g/in3. 5. A filter according to claim 1, wherein the washcoat layer is one or more layers substantially covering the substrate pores at the inlet and/or outlet surfaces. 6. A filter according to claim 1 wherein the washcoat layer is disposed to effectively narrow the substrate pores. 7. A filter according to claim 1, wherein the porous substrate is a ceramic wallflow filter. 8. A filter according to claim 1, wherein the washcoat layer comprises a selective catalytic reduction (SCR) catalyst containing a non-zeolitic molecular sieve selected from aluminophosphate (AlPO) molecular sieves, metal substituted aluminophosphate molecular sieves (MeAlPO) zeolites, silico-aluminophosphate (SAPO) molecular sieves and metal substituted silico-aluminophosphate (MeAPSO) molecular sieves. 9. A filter according to claim 1, wherein the washcoat layer comprises a selective catalytic reduction (SCR) catalyst containing a molecular sieve, wherein the molecular sieve is an aluminosilicate zeolite or a metal-substituted aluminosilicate zeolite having a framework structure selected from the group consisting of AEI, ZSM-5, ZSM-20, ERI, LEV, mordenite, BEA, Y, CHA, MCM-22 and EU-I. 10. A filter according to claim 8, wherein the non-zeolitic molecular sieve is SAPO and the SAPO contains a transition metal promoter is selected from the group consisting of Cr, Co, Cu, Fe, Hf, La, Ce, In, V, Mn, Ni, Zn, Ga and the precious metals Ag, Au, Pt, Pd and Rh. 11. A filter according to claim 9, wherein the molecular sieve is aluminosilicate and the aluminosilicate contains a transition metal selected from the group consisting of Cr, Co, Cu, Fe, Hf, La, Ce, In, V, Mn, Ni, Zn, Ga and the precious metals Ag, Au, Pt, Pd and Rh. 12. A filter according to claim 10, wherein the transition metal is selected from the group consisting of Cu, Fe, and Ce. 13. A filter according to claim 11, wherein the transition metal is selected from the group consisting of Ce, Fe and Cu. 14. A method of trapping particulate matter (PM) from exhaust gas emitted from a compression ignition engine by depth filtration, which method comprising contacting exhaust gas containing the PM with a filter comprising a porous substrate having inlet and outlet surfaces and substrate pores of a first mean pore size, wherein the porous substrate is coated with a washcoat layer comprising a molecular sieve promoted with at least one transition metal, wherein the washcoat layer is present as a non-permeating porous coating on said inlet or outlet surfaces and the layer contains pores of a second mean pore size, and wherein the second mean pore size which is less than the first mean pore size, and wherein both the inlet and the outlet surfaces are washcoated and wherein the inlet surfaces washcoat has a mean pore size that is less than the outlet surfaces washcoat. 15. A method of trapping particulate matter (PM) from exhaust gas emitted from a compression ignition engine by depth filtration, which method comprising contacting exhaust gas containing the PM with a filter comprising a porous substrate having inlet and outlet surfaces and substrate pores of a first mean pore size, wherein the porous substrate is coated with a washcoat layer comprising a molecular sieve promoted with at least one transition metal, wherein the washcoat layer is present as a non-permeating porous coating on said inlet or outlet surfaces and the layer contains pores of a second mean pore size, and wherein the second mean pore size which is less than the first mean pore size, and wherein both the inlet and the outlet surfaces are washcoated and wherein the inlet surfaces washcoat has a mean pore size that is less than the outlet surfaces washcoat. 16. The filter according to claim 1, wherein the washcoat layer is on the inlet surfaces. 17. The filter according to claim 16, wherein the washcoat layer is also within the substrate pores of the porous substrate. 18. The filter according to claim 16, further comprising a plurality of washcoat layers, wherein each of the washcoat layers within the plurality is different. 19. The filter according to claim 16, wherein the second mean pore size is less than the first mean pore size and the first mean pore size is less than the mean pore size of the outlet surfaces washcoat. 20. The filter according to claim 16, wherein the washcoat layer and the outlet surfaces washcoat have different formulations. 21. The filter according to claim 16, wherein the outlet surfaces washcoat comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe. 22. The filter according to claim 16, wherein the washcoat layer comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe and the outlet surfaces washcoat comprises a catalyst containing precious metal supported on an alumina-based metal oxide. 23. The filter according to claim 16, wherein the outlet surfaces washcoat comprises a plurality of washcoat layers, wherein each of the washcoat layers within the plurality is different, wherein the outlet surfaces washcoat comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe, and a catalyst containing Pt and/or Pd on an alumina-based metal oxide. 24. The filter according to claim 1, wherein the washcoat layer is on the outlet surfaces. 25. The filter according to claim 24, wherein the washcoat layer is also within the substrate pores of the porous substrate. 26. The filter according to claim 24, further comprising a plurality of washcoat layers, wherein each of the washcoat layers within the plurality is different. 27. The filter according to claim 24, wherein the second mean pore size is less than the first mean pore size and is less than the mean pore size of the inlet surfaces washcoat. 28. The filter according to claim 24, wherein the inlet surfaces washcoat and the washcoat layer have different formulations. 29. The filter according to claim 24, wherein the washcoat layer comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe. 30. The filter according to claim 24, wherein the inlet surfaces washcoat comprises a catalyst containing precious metal supported on an alumina-based metal oxide and said washcoat layer comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe. 31. The filter according to claim 24, wherein the washcoat layer comprises a plurality of washcoat layers, wherein each of the washcoat layers within the plurality is different, and wherein the plurality of washcoat layers comprises a catalyst containing an aluminosilicate or silicoaluminophosphate having a framework structure selected from the group consisting of AEI, ZSM-5, ERI, LEV, mordenite, BEA, or CHA and having a transition metal promoter selected from the group consisting of Cu and Fe, and a catalyst containing Pt and/or Pd on an alumina-based metal oxide.
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