Catalyst for the oxidation of NO, the oxidation of a hydrocarbon, the oxidation of NH.SUB.3 .and the selective catalytic reduction of NOx

Abstract

The present invention relates to a catalyst for the oxidation of NO, for the oxidation of ammonia, for the oxidation of HC and for the selective catalytic reduction of NOx, comprising a flow through substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough; a first coating comprising one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron; a second coating comprising a first platinum group metal component supported on a non-zeolitic first oxidic material and further comprising one or more of a vanadium oxide and a zeolitic material comprising one or more of copper and iron; optionally a third coating comprising a second platinum group metal component supported on a second oxidic material; wherein the third coating is disposed on the surface of the internal walls and under the second coating over z % of the axial length of the substrate from the outlet end to the inlet end, with z being in the range of from 0 to 100; wherein the second coating extends over y % of the axial length of the substrate from the inlet end to the outlet end and is disposed either on the surface of the internal walls, or on the surface of the internal walls and the third coating, or on the third coating, with y being in the range of from 95 to 100; wherein the first coating extends over x % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the second coating, with x being in the range of from 20 to y.

Claims

1. A catalyst, comprising (i) a flow through substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough; (ii) a first coating comprising one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; (iii) a second coating comprising a physical mixture of a first platinum group metal component supported on a non-zeolite first oxide-containing material, one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; and (iv) a third coating comprising a second platinum group metal component supported on a second oxide-containing material; wherein the third coating is disposed on the surface of the internal walls and under the second coating over z % of the axial length of the substrate from the outlet end to the inlet end, with z being in the range of from 20 to 100; wherein the second coating extends over y % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the surface of the internal walls and the third coating, or on the third coating, with y being in the range of from 95 to 100; and wherein the first coating extends over x % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the second coating, with x being in the range of from 20 to y.

2. The catalyst of claim 1, wherein y ranges from 95 to 100.

3. The catalyst of claim 1, wherein z ranges from 0 to 65.

4. The catalyst of claim 1, wherein the zeolite material comprised in the first coating has a framework type chosen from AEI, GME, CHA, MFI, BEA, FAU, MOR, a mixture of two or more thereof, and a mixed type of two or more thereof.

5. The catalyst of claim 1, wherein the zeolite material comprised in the first coating comprises copper.

6. The catalyst of claim 1, wherein the first platinum group metal component comprised in the second coating is one or more of platinum, palladium and rhodium.

7. The catalyst of claim 1, wherein the zeolite material comprised in the second coating has a framework type chosen from AEI, GME, CHA, MFI, BEA, FAU, MOR, a mixture of two or more thereof, and a mixed type of two or more thereof.

8. The catalyst of claim 1, wherein the zeolite material comprised in the second coating comprises copper.

9. The catalyst of claim 1, wherein in the catalyst, the second coating and the third coating together have a platinum group metal component loading, calculated as elemental platinum group metal, ranging from 0.035 to 1.41 g/l (1 to 40 g/ft.sup.3).

10. The catalyst of claim 1, wherein the second coating comprises (A) an upstream coating comprising a platinum group metal component supported on a non-zeolite oxide-containing material and further comprises one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; and (B) a downstream coating comprising a platinum group metal component supported on a non-zeolite oxide-containing material and further comprises one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; wherein the upstream coating extends over y.sub.1% of the axial length of the substrate from the inlet end to the outlet end and is disposed on the surface of the internal walls and the third coating, or on the third coating; wherein the outlet coating extends over y2% of the axial length of the substrate from the outlet end to the inlet end and is disposed on the surface of the internal walls and the third coating, or on the third coating; wherein y.sub.1 ranges from 45 to 55 and y.sub.2 ranges from 45 to 55; wherein the upstream coating comprises the platinum group metal component at a first loading (I.sub.1) and the outlet coating comprises the platinum group metal component at a loading (I.sub.2), wherein the ratio of (I.sub.1):(I.sub.2) ranges from 0.2:1 to 0.75:1; wherein the first platinum group metal component comprises the platinum group metal component of the upstream coating and the platinum group metal component of the outlet coating; and wherein the non-zeolite first oxide-containing material comprises the non-zeolite oxidic material of the upstream coating and the non-zeolite oxide-containing material of the outlet coating.

11. The catalyst of claim 10, wherein the platinum group metal component comprised in the upstream coating of the second coating is one or more of platinum, palladium, and rhodium; wherein the non-zeolite oxide-containing material supporting the platinum group metal component comprised in the upstream coating.

12. The catalyst of claim 10, wherein the zeolite material comprised in the upstream coating of the second coating has a framework type chosen from AEI, GME, CHA, MFI, BEA, FAU, MOR, a mixture of two or more thereof, and a mixed type of two or more thereof.

13. The catalyst of claim 10, wherein the zeolite material comprised in the upstream coating of the second coating comprises copper.

14. The catalyst of claim 10, wherein the platinum group metal component comprised in the outlet coating of the second coating is one or more of platinum, palladium and rhodium.

15. The catalyst of claim 10, wherein the zeolite material comprised in the outlet coating of the second coating has a framework type chosen from AEI, GME, CHA, MFI, BEA, FAU, MOR, a mixture of two or more thereof, and a mixed type of two or more thereof.

16. The catalyst of claim 10, wherein the zeolite material comprised in the outlet coating of the second coating comprises copper.

17. The catalyst of claim 1, wherein the catalyst comprises the flow-through substrate, the first coating, the second coating and the third coating, wherein z ranges from 20 to 65; or wherein z ranges from 80 to 100.

18. The catalyst of claim 17, wherein the second platinum group metal component comprised in the third coating is one or more of platinum, palladium and rhodium.

19. A method for preparing the catalyst claim 1, the method comprising: (a) providing an uncoated flow-through substrate, the substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough; (b) providing a slurry comprising a second platinum group metal component and a second oxide-containing material, disposing said slurry on the surface of the internal walls of the substrate, over z % of the substrate axial length from the outlet end to the inlet end, wherein z ranges from 20 to 100, calcining the slurry disposed on the substrate, obtaining a third coating disposed on the substrate; (c) providing one or more slurries comprising a first platinum group metal component, a non-zeolite first oxide-containing material and water and one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron, and a solvent, disposing said one or more slurries on the surface of the internal walls and the third coating, or on the third coating, over y % of the substrate axial length, wherein y ranges from 95 to 100, calcining the one or more slurries disposed on the substrate, obtaining a second coating disposed on the substrate; and (d) providing a slurry comprising one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron, and a solvent, disposing said slurry over x % of the substrate axial length on the second coating from the inlet end to the outlet end, wherein x ranges from 20 to y, calcining the slurry disposed on the substrate, obtaining the catalyst for the oxidation of NO, for the oxidation of ammonia, for the oxidation of HC and for the selective catalytic reduction of NOx.

20. An exhaust gas treatment system comprising: an upstream end for introducing exhaust gas stream into said exhaust gas treatment system, wherein said exhaust gas treatment system comprises the catalyst according to claim 1 and one or more of a diesel oxidation catalyst, a selective catalytic reduction catalyst, and a particulate filter.

21. A catalyst for oxidation of NO, for oxidation of ammonia, for oxidation of HC and for selective catalytic reduction of NOx, the catalyst comprising (i) a flow through substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough; (ii) a first coating comprising one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; (iii) a second coating comprising a physical mixture of a first platinum group metal component supported on a non-zeolite first oxide-containing material and further comprising one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; and (iv) a third coating comprising a second platinum group metal component supported on a second oxide-containing material; wherein the third coating is disposed on the surface of the internal walls and under the second coating over z % of the axial length of the substrate from the outlet end to the inlet end, wherein z ranges from 10 to 80; wherein the second coating extends over y % of the axial length of the substrate from the outlet end to the inlet end and is disposed on the third coating and the surface of the internal walls, or on the third coating, wherein y ranges from 10 to 80; and wherein the first coating extends over x % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the surface of the internal walls and on the second coating, wherein x ranges from 95 to 100.

22. A catalyst, comprising (i) a flow through substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough; (ii) a first coating comprising one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; (iii) a second coating comprising a physical mixture of a first platinum group metal component supported on a non-zeolite first oxide-containing oxidic material and one or more of a vanadium oxide and a zeolite material comprising one or more of copper and iron; and (iv) optionally a third coating comprising a second platinum group metal component supported on a second oxidic material; wherein, when present, the optional third coating is disposed on the surface of the internal walls and under the second coating over z % of the axial length of the substrate from the outlet end to the inlet end, with z being in the range of from 0 to 100; wherein the second coating extends over y % of the axial length of the substrate from the inlet end to the outlet end and is disposed either on the surface of the internal walls, or, optionally, on the surface of the internal walls and the optional third coating, or, optionally, on the optional third coating, with y being in the range of from 95 to 100; and wherein the first coating extends over x % of the axial length of the substrate from the inlet end to the outlet end and is disposed on the second coating, with x being in the range of from 20 to y.

Description

EXAMPLES

Reference Example 1: Determination of the Dv90 Values

(1) The particle size distributions were determined by a static light scattering method using Sympatec HELOS equipment, wherein the optical concentration of the sample was in the range of from 5 to 10%.

Reference Example 2: Preparation of a Cu-CHA Zeolite

(2) The zeolitic material having the framework structure type CHA comprising Cu and used in the examples herein was prepared according to the teaching of U.S. Pat. No. 8,293,199 B2. Particular reference is made to Inventive Example 2 of U.S. Pat. No. 8,293,199 B2, column 15, lines 26 to 52.

Reference Example 3: Measurement of the BET Specific Surface Area

(3) The BET specific surface area was determined according to DIN 66131 or DIN ISO 9277 using liquid nitrogen.

Reference Example 4: General Coating Method

(4) In order to coat the flow-through substrate with one or more coatings, the flow-through substrate was suitably immersed vertically in a portion of a given slurry for a specific length of the substrate which was equal to the targeted length of the coating to be applied and vacuum was applied. In this manner, the slurry contacted the walls of the substrate. The sample was left in the slurry for a specific period of time, usually for 1-10 seconds. The substrate was then removed from the slurry, and excess slurry was removed from the substrate by allowing it to drain from the substrate, then by blowing with compressed air (against the direction of slurry penetration).

Reference Example 5: Preparation of a Cu-SCR Catalyst

(5) An aqueous zirconyl-acetate solution was diluted in water (such that upon calcination this would lead to 3 weight % of ZrO.sub.2 in water based on the original weight of the solution). The amount of zirconyl-acetate was calculated such that the loading of zirconia in the catalyst after calcination, calculated as ZrO.sub.2, was 6.10 g/l (0.1 g/in.sup.3). To this, a Cu-CHA zeolite prepared according to Reference Example 2 herein except that the zeolite was spray-dried, were added. The amount of Cu-CHA was calculated such that the loading of Cu-CHA in the catalyst after calcination was 170.87 g/l (2.8 g/in.sup.3). The resulting slurry was then milled until the resulting Dv90 determined as described in Reference Example 1 herein was 10 micrometers.

(6) The final slurry was then disposed over the full length of an uncoated honeycomb cordierite monolith substrate (diameter: 26.67 cm (10.5 inches)×length: 15.24 cm (6 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness). Afterwards, the coated substrate was dried at 120° C. for 10 minutes and at 160° C. for 30 minutes and was then calcined at 450° C. for 30 minutes. The washcoat loading after calcination was 189.17 g/l (3.1 g/in.sup.3).

Comparative Example 1: Preparation of a Catalyst not According to the Present Invention

(7) A mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into alumina (Al.sub.2O.sub.3 (about 80 weight-%) doped with about 20 weight-% of ZrO.sub.2, having a BET specific area of about 200 m.sup.2/g, a Dv90 of 125 micrometers and a total pore volume of 0.325 ml/g), corresponding to a final zirconia-alumina loading in the catalyst of 15.26 g/l (0.25 g/in.sup.3), under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the oxidic support. The final solid content after incipient wetness was of approximately 78 weight-%. The resulting mixture after incipient wetness impregnation was pre-calcined at 590° C. for 4 hours to remove any moisture and to fix the platinum onto the metal oxide support material giving a dry platinum content of 0.28 g/l (8 g/ft.sup.3). Subsequently, the pre-calcined Pt impregnated alumina was made into a slurry. Firstly, tartaric acid (5 times the volume of the platinum solution used above) was added to water as was monoethanolamine (MEA) in a ratio of 1/10 of the volume of the platinum solution used above. Secondly, the Pt impregnated alumina was added to the solution and mixed thereby forming a Pt-containing slurry with a solid content of 40% by weight. The resulting slurry was milled until the resulting Dv90 determined as in Reference Example 1 was 10 micrometers.

(8) Separately, a zirconyl-acetate mixture with a solid content of 30 weight-%, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 7.93 g/l (0.13 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (3.25 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 32) prepared according to Reference Example 2 and corresponding to a final Cu-CHA loading in the catalyst of 158.66 g/l (2.6 g/in.sup.3), was added and mixed, forming a Cu-CHA slurry. The resulting slurry had a solid content of 38 weight-%. The particles in the resulting slurry had a Dv90 determined as in Reference Example 1 of 10 micrometers. The Pt-containing slurry was added to the Cu-CHA slurry and stirred, forming the final slurry. The final slurry was then disposed over the full length of an uncoated honeycomb cordierite monolith substrate using the coating method described in Reference Example 4 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness). Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes (to remove between 85 and 95% of moisture) and was then calcined at 590° C. for 30 minutes. The washcoat loading after calcination was 182.13 g/l (2.98 g/in.sup.3+8 g/ft.sup.3).

Example 1: Preparation of a Tetra-Functional Catalyst According to the Present Invention Second Coating (Bottom Coating)

(9) A mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into titania (TiO.sub.2 (90 weight-%) and 10 weight-% of SiO.sub.2, having a BET specific surface are of 200 m.sup.2/g and a Dv90 of 20 micrometers), corresponding to a final silica-titania loading in the catalyst of 15.26 g/l (0.25 g/in.sup.3), under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the silica-titania support. The final solid content after incipient wetness was of approximately 70 weight-%. Subsequently, the Pt impregnated titania was made into a slurry. Firstly, tartaric acid (5 times the volume of the platinum solution used above) was added to water as was monoethanolamine (MEA) in a ratio of 1/10 of the volume of the platinum solution used above. Secondly, the Pt impregnated titania was added to the solution and mixed thereby forming a Pt-containing slurry with a solid content of 40% by weight. The resulting slurry was milled until the resulting Dv90 determined as in Reference Example 1 was 10 micrometers.

(10) Separately, a zirconyl-acetate mixture with a solid content of 30 weight-%, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 6.1 g/l (0.1 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (5.1 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 19) was added and mixed (final CHA loading in the catalyst of 2.15 g/in.sup.3). The particles in the resulting slurry had a Dv90 determined as in Reference Example 1 of 10 micrometers. The resulting slurry had a solid content of 38% by weight. The Pt-containing slurry was added to the Cu-CHA slurry and stirred, creating the final slurry. The final slurry was then disposed over the full length of an uncoated honeycomb cordierite monolith substrate using the coating method described in Reference Example 5 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness) to form a second coating. Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes (to remove between 85 and 95% of moisture) and was calcined at 590° C. for 30 minutes. The washcoat loading of the second coating after calcination was 152.84 g/l (2.5 g/in.sup.3+8 g/ft.sup.3), including a final platinum loading of 0.28 g/l.

(11) First Coating (Top Coating)

(12) A zirconyl-acetate mixture with a solid content of 30 weight-%, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 6.1 g/l (0.1 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (5.1 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 19) corresponding to a final Cu-CHA loading in the catalyst of 57.97 g/l (0.95 g/in.sup.3), was added and mixed. The resulting slurry had a solid content of 38.5 weight-%. The resulting slurry was then disposed over the full length of the second coating using the coating method described in Reference Example 4. Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes (to remove between 85 and 95% of moisture) and was calcined at 450° C. for 30 minutes. The washcoat loading of the first coating after calcination 64.07 g/l (1.05 g/in.sup.3).

Example 2: Preparation of a Tetra-Functional Catalyst According to the Present Invention

(13) Second Coating (Bottom Coating)

(14) Inlet Coat

(15) A mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into alumina (Al.sub.2O.sub.3 (about 80 weight-%) doped with about 20 weight-% of ZrO.sub.2, having a BET specific area of about 200 m.sup.2/g, a Dv90 of 125 micrometers and a total pore volume of 0.425 ml/g), corresponding to a final zirconia-alumina loading in the catalyst of 15.26 g/l (0.25 g/in.sup.3), under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the alumina support. The final solid content after incipient wetness was approximately 78 weight-%. The resulting mixture was added to a solution of water with tartaric acid (5 times the volume of the platinum solution used above) and monoethanolamine in a ratio of 1/10 of the volume of the platinum solution used above, such that the final solid content of the resulting slurry after addition of Pt-impregnated support was 40 weight-%. Afterwards, the resulting slurry was milled until the Dv90 was 10 micrometers.

(16) Separately, a zirconyl-acetate mixture with a solid content of 30% by weight, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 6.1 g/l (0.1 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (5.1 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 19) was added and mixed (final CHA loading in the catalyst of 131.20 g/l (2.15 g/in.sup.3)). The resulting slurry had a solid content of 38 weight-%. The particles in the resulting slurry had a Dv90 determined as in Reference Example 1 of 10 micrometers. To this Cu-CHA slurry, the Pt-containing slurry was added forming a final slurry which was stirred. The final slurry was then disposed from the inlet side of an uncoated honeycomb cordierite monolith substrate toward the outlet side over less than half of the length of the substrate using the coating method described in Reference Example 4 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness). Afterwards, the coated substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes to remove between 85 and 95% of moisture and was calcined at 590° C. for 30 minutes. The washcoat loading of the inlet coating after calcination was 152.74 g/l (2.5 g/in.sup.3+5 g/ft.sup.3), including a final platinum loading in the inlet coating of 0.18 g/l.

(17) Outlet Coat

(18) A mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into alumina (Al.sub.2O.sub.3 (about 80 weight-%) doped with about 20 weight-% of ZrO.sub.2, having a BET specific area of about 200 m.sup.2/g, a Dv90 of 125 micrometers and a total pore volume of 0.425 ml/g), corresponding to a final zirconia-alumina loading in the catalyst of 15.26 g/l (0.25 g/in.sup.3) under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the alumina support. The final solid content after incipient wetness was approximately 78 weight-%. The resulting mixture was added to a solution of water with tartaric acid (5 times the amount of platinum solution used above and monoethanolamine in a ratio of 1/10 of the amount of platinum solution used above, such that the final solid content of the resulting slurry after addition of Pt-impregnated support was 40 weight-%. Afterwards, the resulting slurry was milled until the Dv90 was 10 micrometers.

(19) Separately, a zirconyl-acetate mixture with a solid content of 30% by weight, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 6.1 g/l (0.1 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (5.1 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 19) was added and mixed (a final CHA loading in the catalyst of 131.20 g/l (2.15 g/in.sup.3)). The resulting slurry had a solid content of 38 weight-%. The particles in the resulting slurry had a Dv90 determined as in Reference Example 1 of 10 micrometers. To this Cu-CHA slurry, the Pt-containing slurry was added forming a final slurry which was stirred. The final slurry was then disposed from the outlet side of the honeycomb cordierite monolith substrate toward the inlet side over less than half of the length of the substrate such that there was a gap of 5 to 8 mm between the inlet coating and the outlet coating using the coating method described in Reference Example 4 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness). Afterwards, the coated substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes to remove between 85 and 95% of moisture and was calcined at 590° C. for 30 minutes. The washcoat loading of the outlet coating after calcination was 152.95 g/l (2.5 g/in.sup.3+11 g/ft.sup.3), including a final platinum loading in the outlet coating of 0.39 g/l. The total platinum loading in the catalyst was of 0.28 g/l (8 g/ft.sup.3).

(20) First Coating (Top Coating)

(21) The slurry of the first coating was prepared as the slurry of the first coating in Example 1. The resulting slurry was disposed over the second coating (inlet coating and outlet coating) over the full length of the substrate using the coating method described in Reference Example 4. Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes (to remove between 85 and 95% of moisture) and was calcined at 450° C. 30 minutes. The washcoat loading of the first coating after calcination was 64.07 g/l (1.05 g/in.sup.3).

Example 3.1: Preparation of a Tetra-Functional Catalyst According to the Present Invention

(22) Third Coating (Outlet Bottom Coating)

(23) An mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into titania (TiO.sub.2 (90 weight-%) and 10 weight-% of SiO.sub.2, having a BET specific surface are of 200 m.sup.2/g and a Dv90 of 20 micrometers), corresponding to a final silica-titania loading in the catalyst of 30.51 g/l (0.5 g/in.sup.3), under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the titania support. The final solid content after incipient wetness was approximately 70 weight-%. The resulting mixture was added to a solution of water with tartaric acid (5 times the volume of the platinum solution used above) and monoethanolamine in a ratio of 1/10 of the volume of the platinum solution used above, such that the final solid content of the resulting slurry after addition of Pt-impregnated titania was 40 weight-%. Afterwards, the resulting slurry was milled until the Dv90 was 10 micrometers. The resulting slurry was then disposed from the outlet side of an uncoated honeycomb cordierite monolith substrate toward the inlet side over half of the length of the substrate using the coating method described in Reference Example 4 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness) to form the third coating. Afterwards, the coated substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes to remove between 85 and 95% of moisture and was calcined at 590° C. for 30 minutes. The washcoat loading of the third coating in the catalyst after calcination was 30.86 g/l (0.50 g/in.sup.3+10 g/ft.sup.3), including a final platinum loading in the third coating of 0.35 g/l.

(24) Second Coating (Middle Coating)

(25) An mixture of a platinum precursor, a platinum complexed with monoethanolamine (MEA) with a solid content of 17 weight-%, and water was added dropwise into titania (TiO.sub.2 (90 weight-%) and 10 weight-% of SiO.sub.2, having a BET specific surface are of 200 m.sup.2/g and a Dv90 of 20 micrometers), corresponding to a final silica-titania loading in the catalyst of 15.26 g/l (0.25 g/in.sup.3) under constant stirring thereby performing an incipient wetness impregnation. The amount of liquids added was suitably calculated to fill the pore volume of the oxidic support. The final solid content after incipient wetness was approximately 70 weight-%. Subsequently, the pre-calcined Pt impregnated titania was made into a slurry. Firstly, tartaric acid (5 times the volume of the platinum solution used above) was added to water as was monoethanolamine (MEA) in a ratio of 1/10 of the volume of the platinum solution used above. Secondly, the Pt impregnated titania was added to the solution and mixed thereby forming a Pt-containing slurry with a solid content of 40% by weight. The resulting slurry was milled until the resulting Dv90 determined as in Reference Example 1 was 10 micrometers.

(26) Separately, a zirconyl-acetate mixture with a solid content of 30% by weight, such that the final zirconia loading (calculated as ZrO.sub.2) in the catalyst was 6.1 g/l (0.1 g/in.sup.3), was added to water to create a mixture with a solid content of approximately 3 weight-%. To this, Cu-CHA zeolite (5.1 weight-% of Cu calculated as CuO and a SiO.sub.2:Al.sub.2O.sub.3 molar ratio of 19) was added and mixed (final CHA loading in the catalyst of 131.20 g/l (2.15 g/in.sup.3)). The resulting slurry had a solid content of 38% by weight. The particles in the resulting slurry had a Dv90 determined as in Reference Example 1 of 10 micrometers. To this Cu-CHA slurry, the Pt-containing slurry was added and stirred, creating the final slurry. The final slurry was then disposed over the full length of the honeycomb cordierite monolith substrate from the inlet side of the substrate towards the outlet side and covering the third coating using the coating method described in Reference Example 4 (diameter: 26.67 cm (10.5 inches)×length: 7.62 cm (3 inches) cylindrically shaped substrate with 400/(2.54).sup.2 cells per square centimeter and 0.1 millimeter (4 mil) wall thickness). Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes to remove between 85 and 95% of moisture and was calcined at 590° C. for 30 minutes. The washcoat loading of the second coating after calcination was 152.67 g/l (2.5 g/in.sup.3+3 g/ft.sup.3), including a final platinum loading of 0.11 g/l. The total platinum loading in the catalyst was of 0.28 g/l (8 g/ft.sup.3).

(27) First Coating (Top Coating)

(28) The slurry of the first coating was prepared as in Example 1. The resulting slurry was then disposed over the full length of the first coating using the coating method described in Reference Example 4. Afterwards, the substrate was dried at 120° C. for 15 minutes, then at 160° C. for 30 minutes (to remove between 85 and 95% of moisture) and was calcined at 450° C. for 30 minutes. The washcoat loading of the first coating after calcination was 64.07 g/l (1.05 g/in.sup.3).

Example 3.2: Preparation of a Tetra-Functional Catalyst According to the Present Invention

(29) Third Coating (Outlet Bottom Coating)

(30) The slurry of the third coating was prepared and coated as in Example 3.1 except that the final platinum loading was 0.46 g/l (13 g/ft.sup.3).

(31) Second Coating (Middle Coating)

(32) The slurry of the second coating was prepared and coated as in Example 3.1 except that the final platinum loading was 0.05 g/l (1.5 g/ft.sup.3). The total platinum loading in the catalyst was of 0.28 g/l (8 g/ft.sup.3).

(33) First Coating (Top Coating)

(34) The slurry of the first coating was prepared and coated as in Example 3.1.

Example 4: Use of the Catalysts of Examples 1 to 3.1 and Comparative Example 1—NH.SUB.3 .Oxidation/N.SUB.2.O Make

(35) For testing the fresh catalysts of Examples 1 to 3.1 and of Comparative Example 1, the NH3 oxidation and the N.sub.2O make were measured at different temperatures at the entrance of the catalysts, namely at 250, 300 and 350° C. (space velocity: 100 000 hr.sup.−1, 515 ppm of NH.sub.3, 7% H.sub.2O, 7% CO.sub.2 and 8% O.sub.2). The results are displayed in Table 1 below.

(36) TABLE-US-00001 TABLE 1 Results of the tested fresh catalysts Comparative Example 1 Example 2 Example 3.1 Example 1 NH.sub.3 N.sub.2O NH.sub.3 N.sub.2O NH.sub.3 N.sub.2O NH.sub.3 N.sub.2O T ox. make ox. make ox. make ox. make (° C.) (%) (ppm) (%) (ppm) (%) (ppm) (%) (ppm) 250 76 21 45 12 65 19 78 28 300 97 19 96 21 94 14 100 53 350 98 11 97 10 97 7 100 33

(37) As may be taken from Table 1, the catalysts of Examples 1 to 3.1 exhibit great ammonia oxidations of 94 to 98% at 300 and 350° C. but slightly lower than with the catalyst of Comparative Example 1. However, they produce less nitrous oxide (2.5 to 4.7 times less) compared to the nitrous oxide produced with the catalyst of Comparative Example 1. Therefore, the catalysts according to the present invention permits to obtain a great balance between the ammonia conversion and the nitrous oxide make under fresh conditions at high temperatures. This example demonstrates that the particular composition of the catalysts according to the present invention permits to obtain great ammonia oxidation while permitting to greatly reduce the nitrous oxide formation.

Example 5: Use of the Catalysts of Examples 1 to 3.1 and Comparative Example 1—DeNOx/N.SUB.2.O Make

(38) For testing the fresh catalysts of Examples 1 to 3.1 and of Comparative Example 1, the NOx conversion and the N.sub.2O make were measured at different temperatures at the entrance of the catalysts, namely at 175, 200, 225, 250 and 400° C. (space velocity: 60 000 hr.sup.−1, 515 ppm of NO, NH.sub.3 to NOx ratio of 1.1, 5% H.sub.2O, 5% CO.sub.2 and 10% O.sub.2). The results are displayed in Table 2 below.

(39) TABLE-US-00002 TABLE 2 Results of the tested fresh catalysts Comparative Example 1 Example 2 Example 3.1 Example 1 N.sub.2O N.sub.2O N.sub.2O N.sub.2O T DeNOx make DeNOx make DeNOx make DeNOx make (° C.) (%) (ppm) (%) (ppm) (%) (ppm) (%) (ppm) 175 64 10 59 8 61 7 45 15 200 89 25 86 20 85 17 81 64 225 96 71 97 45 96 50 95 181 250 94 71 95 52 93 64 81 202 400 92 7 91 6 87 7 48 24

(40) As may be taken from Table 2, the catalysts of Examples 1 to 3.1 exhibits improved NOx conversion over a large temperature range, namely from 175 to 400° C. compared to the NOx conversion obtained with the catalyst of Comparative Example 1 comprising a single coating comprising a mixture of Pt/alumina and Cu-SCR. Further, the catalysts of the inventive examples also permits to reduce the nitrous oxide make. In particular, the catalyst of Example 1 exhibits a NOx conversion of 96% at 225° C. and a N.sub.2O make of 71 ppm, the catalyst of Example 2 exhibits a NOx conversion of 97% at 225° C. and a N.sub.2O make of 45 ppm and the catalyst of Example 3.1 exhibits a NOx conversion of 96% and a N.sub.2O make of 50 ppm.

(41) In contrast thereto, the catalyst of Comparative Example 1 at the same temperature exhibits a NOx conversion of 95% and a N.sub.2O make of 181 ppm (2.5 to 4 times more than with an inventive catalyst).

(42) Thus, this example demonstrates that the catalyst of the present invention permit, in addition to obtain a great balance between the ammonia conversion and the nitrous oxide make under fresh conditions at high temperatures (see Example 4), to obtain improved NOx conversion while permitting to significantly decreasing the nitrous make over a wide temperature range.

Example 6: Use of the Catalysts of Example 1 and 3.1 and of Comparative Example 1—NO.SUB.2./NOx

(43) The NO.sub.2/NOx ratio was measured in the absence of ammonia obtained with the catalysts of Comparative Example 1 and Examples 1 and 3.1 at temperatures of from 200 to 450° C. (space velocity: 100 k/h). The results are depicted in FIG. 2. As may be taken from FIG. 2, the NO oxidation is almost unchanged when using the catalyst of Example 1 and the catalyst of Comparative Example 1.

Example 7: Use of the Catalysts of Examples 1 to 3.1 and Comparative Example 1—NH.SUB.3 .Oxidation/N.SUB.2.O Make

(44) For testing the catalysts of Examples 1 and 3.1 and of Comparative Example 1 were aged at 550° C. for 100 hours. The NH.sub.3 oxidation and the N.sub.2O make were measured at different temperatures at the entrance of the aged catalysts, namely at 300 and 350° C. (space velocity: 100 000 hr.sup.−1, 515 ppm of NH.sub.3, 7% H.sub.2O, 7% CO.sub.2 and 8% O.sub.2). The results are displayed in Table 3 below.

(45) TABLE-US-00003 TABLE 3 Results of the tested aged catalysts Comparative Example 1 Example 3.1 Example 1 NH.sub.3 N.sub.2O NH.sub.3 N.sub.2O NH.sub.3 N.sub.2O T ox. make ox. make ox. make (° C.) (%) (ppm) (%) (ppm) (%) (ppm) 300 97 21 95 13 98 28 350 99 12 97 7 99 16

(46) As may be taken from Table 3, the catalysts of Examples 1 and 3.1 permits to obtain a great balance between the ammonia oxidation and the nitrous oxide make. In particular, the catalyst of Example 1 exhibits a NH.sub.3 oxidation of 99% at 350° C. and a N.sub.2O make of 12 ppm and the catalyst of Example 3.1 exhibits a NH.sub.3 oxidation of 97% at 350° C. and a N.sub.2O make of only 7 ppm.

(47) In contrast thereto, the catalyst of Comparative Example 1 exhibits a comparably NH.sub.3 oxidation of 99% at the same temperature and a higher N.sub.2O make of 16 ppm.

(48) Thus, this example demonstrates that even under aged conditions, the catalysts according to the present invention permits to obtain a great balance between the ammonia conversion and the nitrous oxide make, in particular at high temperatures. This also shows that the catalysts of the present invention are thermally stable.

Example 8: Use of the Catalysts of Example 3.1 and Comparative Example 1—DeNOx/N.SUB.2.O Make

(49) For testing the catalysts of Example 3.1 and of Comparative Example 1 were aged at 550° C. for 100 hours. The NOx conversion and the N.sub.2O make were measured at different temperatures at the entrance of the aged catalysts, namely at 200, 225, 250 and 400° C. (space velocity: 60 000 hr.sup.−1, 515 ppm of NO, NH.sub.3 to NOx ratio of 1.1, 5% H.sub.2O, 5% CO.sub.2 and 10% O.sub.2). The results are displayed in Table 4 below.

(50) TABLE-US-00004 TABLE 4 Results of the tested aged catalysts Comparative Example 3.1 Example 1 N.sub.2O N.sub.2O DeNOx make DeNOx make T° C. (%) (ppm) (%) (ppm) 200 88 23 85 30 225 96 53 95 76 250 93 49 89 75 400 86 9 71 12

(51) As may be taken from Table 4, the catalyst of Example 3.1 exhibits improved NOx conversion and reduced N.sub.2O make over a wide temperature range of 200 to 400° C. compared to the catalyst of Comparative Example 1. Thus, this example demonstrates that the catalysts of the present invention permits to obtain a great balance between the DeNOx and the nitrous oxide even under aged conditions. This also shows that the catalysts of the present invention are thermally stable.

Example 9: Preparation of a Catalyst According to the Present Invention

(52) The catalyst of Example 9 was prepared as the catalyst of Example 1 except that the first coating was disposed over half of the length of the first coating from the inlet end towards the outlet end and the washcoat loading of the first coating after calcination was of 91.53 g/l (1.5 g/in.sup.3), including a final Cu-CHA loading of 1.43 g/in.sup.3 and a final zirconia loading of 0.07 g/in.sup.3.

Example 10: Preparation of a Catalyst According to the Present Invention

(53) The catalyst of Example 10 was prepared as the catalyst of Example 3.1 except that the first coating was disposed over half of the length of the first coating from the inlet end towards the outlet end and the washcoat loading of the first coating after calcination was of 91.54 g/l (1.5 g/in.sup.3), including a final Cu-CHA loading of 1.43 g/in.sup.3 and a final zirconia loading of 0.07 g/in.sup.3.

Example 11: Use of the Catalysts of Example 1, 3.1, 9 and 10 and of Comparative Example 1—NH.SUB.3 .Oxidation/N.SUB.2.O Make

(54) For testing the fresh catalysts of Examples 1, 3.1, 9 and 10 and of Comparative Example 1, the NH.sub.3 oxidation and the N.sub.2O make were measured at different temperatures at the entrance of the catalysts, namely at 250, 300 and 350° C. (space velocity: 100 000 hr.sup.−1, 515 ppm of NH.sub.3, 7% H.sub.2O, 7% CO.sub.2 and 8% O.sub.2). The results are displayed in FIGS. 3 and 4.

(55) As may be taken from FIGS. 3 and 4, the catalysts of Examples 1, 3.1, 9 and 10 exhibit great ammonia oxidations of 94 to 98% at 300 and 350° C. but slightly lower than those obtained with the catalyst of Comparative Example 1. However, they produce less nitrous oxide compared to the nitrous oxide produced with the catalyst of Comparative Example 1. Therefore, the catalysts according to the present invention permits to obtain a great balance between the ammonia conversion and the nitrous oxide make under fresh conditions at high temperatures. This example demonstrates that the particular composition of the catalysts according to the present invention permits to obtain great ammonia oxidation while permitting to greatly reduce the nitrous oxide formation.

Example 12: Use of the Catalysts of Example 1, 3.1, 9 and 10 and of Comparative Example 1—DeNOx/N.SUB.2.O Make

(56) For testing the fresh catalysts of Examples 1, 3.1, 9 and 10 and of Comparative Example 1, the NOx conversion and the N.sub.2O make were measured at different temperatures at the entrance of the catalysts, namely at 175, 200, 225, 250 and 400° C. (space velocity: 60 000 hr.sup.−1, 515 ppm of NO, NH.sub.3 to NOx ratio of 1.1, 5% H.sub.2O, 5% CO.sub.2 and 10% O.sub.2). The results are displayed in FIGS. 5 and 6.

(57) As may be taken from FIGS. 5 and 6, the catalysts of Examples 3.1, 9 and 10 exhibit improved NOx conversion over a large temperature range, namely from 175 to 400° C. compared to the NOx conversion obtained with the catalyst of Comparative Example 1 comprising a single coating comprising a mixture of Pt/alumina and Cu-SCR. Further, the catalysts of the inventive examples also permits to reduce the nitrous oxide make. In particular, the catalyst of Example 1 exhibits a NOx conversion of 96% at 225° C. and a N.sub.2O make of 71 ppm, the catalyst of Example 9 (with a second coating disposed only over half of the substrate length on the inlet side) exhibits a NOx conversion of 94% at 225° C. and a N.sub.2O make of 43 ppm, the catalyst of Example 3.1 exhibits a NOx conversion of 96% and a N.sub.2O make of 50 ppm and the catalyst of Example 10 (with a second coating disposed only over half of the substrate length on the inlet side) exhibits a NOx conversion of 96% and a N.sub.2O make of 22 ppm. In contrast thereto, the catalyst of Comparative Example 1 at the same temperature exhibits a NOx conversion of 95% and a N.sub.2O make of 181 ppm. Thus, this example demonstrates that the catalysts of the present invention permit to obtain improved NOx conversion while permitting to significantly decreasing the nitrous make over a wide temperature range. Further, this example shows that the second coating of the catalysts of the present invention when covering only half of the first coating permits to reduce even more the nitrous oxide formation.

Example 13: Preparation of an Exhaust Gas Treatment System According to the Present Invention

(58) An exhaust gas treatment system according to the present invention was prepared by combining the catalyst of Reference Example 5 (“Cu-SCR catalyst”) and the catalyst of Example 3.1 (“Multi-Functional Catalyst (MFC)”), wherein the catalyst of Example 3.1 was located downstream of the catalyst of Reference Example 5.

Example 14: Testing of the Exhaust Gas Treatment System of Example 13—DeNOx/N.SUB.2.O Make

(59) The testing was done on a 13L Euro VI engine under transient WHTC conditions, with average temperatures of around 250° C. (SCR.sub.in) (exhaust mass between 200 and 2000 kg/hr, Ammonia to NOx ratio of 0 to 1, H.sub.2O between 1 and 10% CO.sub.2 between 1 and 10% and O.sub.2 between 6 and 20%) and E.O. NOx levels of around 10 g NOx/kWh. The DeNOx and the amount of N.sub.2O were measured at the outlet end of the MFC at different ANRs (Ammonia to NOx Ratios). The results were displayed in Table 1 below.

(60) TABLE-US-00005 TABLE 1 DeNOx NO.sub.2/NOx N.sub.2O make (MFCout) (gr/gr) (gr cumulated) ANR = 0 — 17% — ANR = 0.75 75% 16% 0.95 ANR = 0.85 84% 13% 1.36 ANR = 0.9 87% 10% 2.0 ANR = 1 91%  7% 3.94

(61) The upstream Cu-SCR increases DeNOx activity in the exhaust gas treatment system as it increases the amount of SCR material in the system. Thus, a DeNOx of 75 to 91% was observed at the outlet end of the MFC of the present invention while presenting low N.sub.2O make.

BRIEF DESCRIPTION OF THE FIGURES

(62) FIG. 1a: (top part of FIG. 1) shows a schematic depiction of a multifunctional catalyst according to the present invention. The multifunctional catalyst 1 according to the present invention is depicted on FIG. 1a, said catalyst comprises a flow-through substrate 2 comprising an inlet end 3, an outlet end 4, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough (not shown). Further, catalyst 1 comprises a second coating 5 which is disposed over the full length of the substrate 2 on the surface of the internal walls of the substrate and a first coating 6 which is disposed on the second coating 5 over the full length of the substrate 2. Alternatively, the first coating 6 can be disposed on the second coating over about half of the length of the substrate 2 from the inlet end to the outlet end of the substrate 2. This alternative is not represented on FIG. 1a.

(63) FIG. 1b: (middle part of FIG. 1) shows a depiction of a multifunctional catalyst according to the present invention. The multifunctional catalyst 11 according to the present invention is depicted on FIG. 1b, said catalyst comprises a flow-through substrate 2 comprising an inlet end 3, an outlet end 4, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough (not shown). The catalyst 11 comprises a second coating comprising an inlet coating 15 a extending from the inlet end to the outlet end of the substrate 2 over half of the length of the substrate 2 and an outlet coating 15 b extending from the outlet end to the inlet end of the substrate 2 over the other half of the length of the substrate 2. Said second coating (15 a+15 b) is disposed on the surface of the internal walls of the substrate 2. Further, the catalyst 11 comprises a first coating 16 which is disposed on the second coating 5 over the full length of the substrate 2.

(64) FIG. 1c: (bottom part of FIG. 1) shows a depiction of a multifunctional catalyst according to the present invention. The multifunctional catalyst 21 according to the present invention is depicted on FIG. 1c, said catalyst comprises a flow-through substrate 2 comprising an inlet end 3, an outlet end 4, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the flow through substrate extending therethrough (not shown). The catalyst 21 comprises a third coating 27 disposed on the surface of the internal walls of the substrate 2 and over about half of the length of the substrate 2 from the outlet end to the inlet end. Further, the catalyst 21 comprises a second coating 25 disposed on the surface of the internal walls of the substrate 2 and on the third coating, said coating extends over the full length of the substrate 2. Finally, the catalyst 21 further comprises a first coating 26 disposed on the second coating over the full length of the substrate 2. Alternatively, the first coating 26 can be disposed on the second coating over about half of the length of the substrate 2 from the inlet end to the outlet end of the substrate 2. This alternative is not represented on FIG. 1c.

(65) FIG. 2: shows the NO.sub.2/NOx ratio in the absence of ammonia obtained with the catalysts of Comparative Example 1 and Examples 1 and 3 at temperatures of from 200 to 450° C.

(66) FIG. 3: shows the NH.sub.3 oxidation in percentage obtained when using the fresh catalysts of Examples 1, 3.1, 9 and 10 and Comparative Example 1 at different temperatures, namely 250, 300 and 350° C. Conditions: space velocity: 100 000 hr.sup.−1, 515 ppm of NH.sub.3, 7% H.sub.2O, 7% CO.sub.2 and 8% O.sub.2.

(67) FIG. 4: shows the N.sub.2O make in ppm obtained when using the fresh catalysts of Examples 1, 3.1, 9 and 10 and Comparative Example 1 at different temperatures, namely 250, 300 and 350° C. Conditions: space velocity: 100 000 hr.sup.−1, 515 ppm of NH.sub.3, 7% H.sub.2O, 7% CO.sub.2 and 8% O.sub.2.

(68) FIG. 5: shows the NOx conversion in percentage obtained when using the fresh catalysts of Examples 1, 3.1, 9 and 10 and Comparative Example 1 at different temperatures, namely 175, 200, 225, 250 and 400° C. Conditions: space velocity: 60 000 hr.sup.−1, 515 ppm of NO, NH.sub.3 to NOx ratio of 1.1, 5% H.sub.2O, 5% CO.sub.2 and 10% O.sub.2.

(69) FIG. 6: shows the N.sub.2O make in ppm obtained when using the fresh catalysts of Examples 1, 3.1, 9 and 10 and Comparative Example 1 at different temperatures, namely 175, 200, 225, 250 and 400° C. Conditions: space velocity: 60 000 hr.sup.−1, 515 ppm of NO, NH.sub.3 to NOx ratio of 1.1, 5% H.sub.2O, 5% CO.sub.2 and 10% O.sub.2.

(70) FIG. 7: shows a schematic depiction of a catalyst according to the present invention. In particular, the catalyst 100 comprises a substrate 101, such as a flow-through substrate, a coating 102, the third coating of the present invention according to II., a coating 103, the second coating of the present invention according to II., and a coating 104, the first coating of the present invention according to II. The compositions of these coating is as defined in the foregoing.

CITED LITERATURE

(71) US 2015/0037233 A WO 2015/189680 A US 2016/0367973 A US 2016/0367974 A