FOUR-WAY CONVERSION CATALYST FOR THE TREATMENT OF AN EXHAUST GAS STREAM

Abstract

The present invention relates to a four-way conversion catalyst for the treatment of an exhaust gas stream of a gasoline engine, the catalyst comprising a porous wall-flow filter substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by porous internal walls of the porous wallflow filter substrate, wherein the plurality of passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, wherein the interface between the passages and the porous internal walls is defined by the surface of the internal walls; wherein the porous internal walls comprise pores which comprise an oxidic component comprising a first refractory metal oxide, said first refractory metal oxide comprising aluminum, said oxidic component having a platinum group metal content in the range of from 0 to 0.001 weight-% based on the total weight of the oxidic component; wherein the catalyst further comprises a first three-way conversion catalytic coating, at least weight-% thereof being comprised in the pores of the internal walls, said first three-way conversion catalytic coating comprising an oxygen storage compound and a platinum group metal supported on a second refractory metal oxide.

Claims

1-17. (canceled)

18. A four-way conversion catalyst for the treatment of an exhaust gas stream of a gasoline engine, the catalyst comprising: a porous wall-flow filter substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by porous internal walls of the porous wall-flow filter substrate, wherein the plurality of passages comprise inlet passages with an open inlet end and a closed outlet end, and outlet passages with a closed inlet end and an open outlet end, wherein an interface between the passages and the porous internal walls is defined by a surface of the internal walls; wherein the porous internal walls comprise pores, the pores comprise an oxidic component comprising a first refractory metal oxide, the first refractory metal oxide comprising alu-minum, the oxidic component having a platinum group metal content ranging from 0 weight-% to 0.001 weight-%, based on a total weight of the oxidic component; and wherein the catalyst further comprises a first three-way conversion catalytic coating, at least 10 weight-% thereof comprised in the pores of the internal walls, the first three-way conversion catalytic coating comprising an oxygen storage compound and a platinum group metal supported on a second refractory metal oxide.

19. The four-way conversion catalyst of claim 18, wherein from 98 weight-% to 100 weight-% of the first refractory metal consists of aluminum and oxygen.

20. The four-way conversion catalyst of claim 18, wherein the oxidic component further comprises an oxide comprising one or more of Mg, Ca, Sr, and Ba and the oxidic component further comprises an oxide comprising one or more of La, Y, Nd, Ti and Zr, or the oxidic component further comprises an oxide comprising one or more of Mg, Ca, Sr, and Ba or the oxidic component further comprises an oxide comprising one or more of La, Y, Nd, Ti and Zr.

21. The four-way conversion catalyst of claim 18, wherein from 98 weight-% to 100 weight-% of the oxidic component consist of the first refractory metal oxide.

22. The four-way conversion catalyst of claim 18, wherein the catalyst comprises the oxidic component at a loading ranging from 7 g/l to 75 g/l.

23. The four-way conversion catalyst of claim 18, wherein the first three-way conversion catalytic coating comprises one or more platinum group metals.

24. The four-way conversion catalyst of claim 18, wherein the oxygen storage compound comprises a mixed oxide comprising cerium, zirconium, yttrium, neodymium and lanthanum, or a mixed oxide comprising cerium, zirconium, yttrium, and lanthanum.

25. The four-way conversion catalyst of claim 18, wherein the first three-way conversion catalytic coating comprises a platinum group metal supported on the oxygen storage component.

26. The four-way conversion catalyst of claim 18, wherein the second refractory metal oxide comprises aluminum.

27. The four-way conversion catalyst of claim 18, wherein from 30 weight-% to 100 weight-% of the first three-way conversion catalytic coating is comprised in the pores of the internal walls.

28. The four-way conversion catalyst of claim 18, wherein the catalyst comprises the first three-way conversion catalytic coating at a loading ranging from 30 g/l to 250 g/l.

29. The four-way conversion catalyst of claim 18, wherein the pores comprising the oxidic component extend over x % of the substrate axial length from the inlet end toward the outlet end of the inlet passages or from the outlet end toward the inlet end of the outlet passages; with x ranging from 95 to 100.

30. The four-way conversion catalyst of claim 29, wherein the first three-way conversion catalytic coating extends over y % of the substrate axial length from the inlet end toward the outlet end of the inlet passages, with y ranging from 20 to x.

31. The four-way conversion catalyst of claim 29, wherein the first three-way conversion catalytic coating extends over y % of the substrate axial length from the inlet end toward the outlet end of the inlet passages, with y ranging from 20 to 70.

32. The four-way conversion catalyst of claim 29, wherein the catalyst further comprises a second three-way conversion catalytic coating, at least 10 weight-% thereof comprised in the pores of the internal walls, the second three-way conversion catalytic coating comprising an oxygen storage compound and a platinum group metal supported on a refractory metal oxide, and wherein the second three-way conversion catalytic coating extends over z % of the substrate axial length from the outlet end toward the inlet end of the outlet passages, with z ranging from 20 to x.

33. A process for preparing the four-way conversion catalyst according to claim 18, comprising: (i) providing a porous wall-flow filter substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by porous internal walls of the porous wall-flow filter substrate, wherein the plurality of passages comprise inlet passages with an open inlet end and a closed outlet end, and outlet passages with a closed inlet end and an open outlet end, wherein the interface between the passages and the porous internal walls is defined by the surface of the internal walls, wherein the internal walls have an average pore size in the range of from 10 micrometers to 30 micrometers, and wherein the average porosity of the internal walls ranges from 25% to 75%; (ii) providing a slurry comprising particles of a source of the oxidic component, the particles having a Dv90 value ranging from 0.005 micrometers to 20 micrometers; coating the porous internal walls of the porous wall-flow filter substrate provided in (i) with the particles of the slurry; calcining the obtained coated filter substrate, obtaining the filter substrate comprising the oxidic component; and (iii) providing a slurry comprising particles of a source of the first three-way conversion catalytic coating, the particles having a Dv90 value ranging from 2 micrometers to 25 micrometers; coating the porous internal walls of the porous wall-flow filter substrate obtained in (ii) with the particles of the slurry; calcining the obtained coated filter substrate, obtaining the filter substrate comprising the oxidic component and the first three-way conversion catalytic coating.

34. An exhaust gas treatment system downstream of and in fluid communication with a gasoline engine, the system comprising a four-way conversion catalyst according to claim 18.

Description

EXAMPLES

Reference Example 1: Measurement of the Porosity of the Porous Oxidic Compound

[0396] The porosity of the porous oxidic compound, e.g. aluminum oxide or cerium-zirconium mixed oxide, was determined by physisorption of N.sub.2 and analyzing the physisorption isotherms via BJH (Barett, Joyner, Halenda) analysis according to DIN 66134.

Reference Example 2: Measurement of the BET Specific Surface Area of Alumina

[0397] The BET specific surface area of the alumina was determined according to DIN 66131 or DIN-ISO 9277 using liquid nitrogen.

Reference Example 3: Measurement of the Average Porosity and the Average Pore Size of the Porous Wall-Flow Substrate

[0398] The average porosity of the porous wall-flow substrate was determined by mercury intrusion using mercury porosimetry according to DIN 66133 and ISO 15901-1.

Reference Example 4: Determination of the Volume-Based Particle Size Distributions

[0399] The particle size distributions were determined by a static light scattering method using Sympatec HELOS (3200) & QUIXEL equipment, wherein the optical concentration of the sample was in the range of from 6 to 10%.

Reference Example 5: Determination of the Viscosity of a Washcoat Slurry

[0400] The slurry dynamic viscosities were measured with a HAAKE Rheostress 6000 manufactured by Thermo Fisher Scientific. Values reported reported here are measured at a shear rate of 300 1/s. The viscosity was measured at 20° C.

Reference Example 6: General Coating Method

[0401] In order to coat a porous wall-flow substrate with a three-way conversion coating according to the present invention, the wall-flow substrate was immersed vertically in a portion of the washcoat for a specific length of the substrate which was equal to the targeted length of the coating to be applied. In this manner, the washcoat contacted the porous walls of the substrate. The sample was left in the washcoat for a specific period of time, usually for 1-10 seconds. The substrate was then removed from the washcoat, 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 washcoat penetration). The coated substrate was then calcined for 3 h at 450° C.

Comparative Example 1: FWC Catalyst not According to the Invention (75 g/l)

[0402] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 1.242 g/in.sup.3 (75 g/l) on a cordierite substrate sized 4.66*5 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 20 micrometers according to the following method: [0403] (1) 1371 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 136.8 g of a 9.06 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 949 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2136 g deionized water containing 8 g n-octanol, 124 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 139 g 21.5 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 4.8 micrometers. [0404] (2) 3756 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La, and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 227.5 g of a 18.53 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1155 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 5006 g of deionized water containing 8 g n-octanol, 290 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 208 g 21.5 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 4.43 micrometers. [0405] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the slurry was adjusted with nitric acid to 3.8. The final slurry had a viscosity of 15.2 mPa.Math.s, measured as described in Reference Example 5. [0406] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 hereinabove over 100% of the axial length of the substrate from the inlet end.

Example 1: FWC Catalyst (75 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 18.89 Micrometers)

[0407] A porous wall-flow substrate as described in Comparative Example 1 was coated with an oxidic component with a loading of 0.501 g/in.sup.3 (30 g/l) prior to the application of the TWC catalytic coating as described in Comparative Example 1. The catalyst was prepared according to the following method: [0408] (1) 2664 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to an aqueous solution containing 12819 g deionized water, 29 g n-octanol, 170 g acetic acid, 433 g of 21.5 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4), 218 g of 59.88 weight-% barium acetate and 667 g of 78.4 weight-% boehmite. The pH of the aqueous phase of the resulting slurry was adjusted with acetic acid to 3.5. The particles of the slurry were then milled so that the Dv90 value of the containing particles was 18.89 micrometers. The solid content of the slurry was 19.04 weight-%. [0409] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0410] (3) The TWC slurry prepared as described in Comparative Example 1 was applied to the coated porous wall-flow filter obtained in (2) as described in Reference Example 6 over 100% of the axial length of the substrate from the inlet end obtaining a TWC loading in the catalyst of 75 g/l.

Example 2: FWC Catalyst (75 g/l TWC Catalytic Coating+15 g/l Oxidic Component—Dv90 of 18.89 Micrometers)

[0411] A porous wall-flow substrate as described in Comparative Example 1 was coated with an oxidic component with a loading 0.25 g/in.sup.3 (15 g/l) prior to the application of TWC catalytic coating as described in Comparative Example 1. The catalyst was prepared according to the following method: [0412] (1) The oxidic component was prepared as described in Example 1 (1). [0413] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0414] (3) The TWC slurry prepared as described in Comparative Example 1 was applied to the coated porous wall-flow filter obtained in (2) as described in Reference Example 6 over 100% of the axial length of the substrate from the inlet end obtaining a TWC loading in the catalyst of 75 g/l.

Example 3: FWC Catalyst (75 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 2.97 Micrometers)

[0415] A porous wall-flow substrate as described in Comparative Example 1 was coated with an oxidic component with a loading of 0.501 g/in.sup.3 (30 g/l) prior to the application of the TWC catalytic coating as described in Comparative Example 1. The catalyst was prepared according to the following method: [0416] (1) 4700 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to an aqueous solution containing 22622 g deionized water, 50 g n-octanol, 300 g acetic acid, 764 g of 30.2 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4), 386 g of 59.88 weight-% barium acetate and 1177 g of 78.4 weight-% boehmite. The pH of the aqueous phase of the resulting slurry was adjusted with acetic acid to 3.7. The particles of the slurry were then milled so that the Dv90 value of the containing particles was 2.97 micrometers. The solid content of the slurry was 18.12 weight-%. [0417] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0418] (3) The TWC slurry prepared as described in Comparative Example 1 was applied to the coated porous wall-flow filter obtained in (2) as described in Reference Example 6 over 100% of the axial length of the substrate from the inlet end obtaining a TWC loading in the catalyst of 75 g/l.

Example 4: Cold Flow Backpressure Evaluation

[0419] The backpressure of the catalysts obtained in Comparative Example 1 and Examples 1 to 3 was measured on a Super Flow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 700 m.sup.3/h was reported in Table 1.

TABLE-US-00001 TABLE 1 Cold Flow Back Pressure Data Back pressure/mbar Comparative Example 1 65.59 Example 1 90.30 Example 2 68.91 Example 3 80.53

[0420] From Table 1, a clear impact of the presence of the oxidic compound in addition to the TWC catalytic coating can be seen, namely a higher amount as well as larger particle size increase backpressure relative to Comparative Example 1.

Example 5

[0421] The catalysts of Comparative Example 1 and Examples 1 to 3 were canned and measured under World Light Duty Test Cycle (WLTC) in close-coupled (CC) position on a dynamic engine bench equipped with a 2.0 l direct-injection turbo engine. Emissions of particulate number according to the Particle Measurement Program (PMP) protocol were measured for full systems and compared to the engine raw emission for calculation of the filtration efficiency. The results are shown in Table 2.

TABLE-US-00002 TABLE 2 WLTC Emission Results on engine bench Particulate Number Filtration Efficiency based (#/km) on engine raw emission Comparative 7.9514E+10 56% Example 1 Example 1 6.5256E+10 64% Example 2  6.765E+10 62% Example 3 6.3616E+10 64% Engine raw 1.7906E+11 - Not applicable - emission

[0422] Example 1, Example 2 and Example 3 show improved filtration efficiency compared to Comparative Example 1.

Example 6

[0423] The canned catalysts from Example 5 were 100 h fuel-cut aged in close-coupled position with 950° C. inlet temperature. The performance of the aged catalysts was measured under New European Drive Cycle (NEDC) in close-coupled (CC) position on 2.0 l engine bench. Emission results measured after the respective catalysts are shown in Table 3.

TABLE-US-00003 TABLE 3 HC, CO and NOx emissions HC [g/km] CO [g/km] NOx [g/km] Comparative 0.373 2.219 0.502 Example 1 Example 1 0.228 1.698 0.396 Example 2 0.276 1.940 0.421 Example 3 0.215 1.590 0.405

[0424] Example 1, Example 2 and Example 3 show improved gaseous conversion performance compared to Comparative Example 1.

Example 7

[0425] The aged catalysts from Comparative Example 1 and Example 3 as obtained in Example 6 were decanned. The samples were investigated for element distribution with electron microprobe analyses (EMPA). Results for Silicon mapping are shown in FIGS. 1 and 2. The results of Example 3 are displayed in FIG. 1 and the results of Comparative Example 1 are displayed in FIG. 2.

[0426] In FIG. 1, the arrow a) shows the catalytic washcoat (TWC) and the arrow b) shows the silicon present in the alumina-based oxidic component, which as may be taken from the figure acts as an undercoat. However according to FIG. 1, there is no silicon in the catalytic washcoat of the catalyst of Example 3. On the contrary, as can be seen in FIG. 2, the arrow c) shows silicon present in the catalytic washcoat of Comparative Example 1. Thus, this example demonstrates that the silicon migration into the catalytic washcoat is hindered by using the catalysts of the invention, namely comprising a specific oxidic component in addition to the catalytic coating(s).

Comparative Example 2: FWC Catalyst not According to the Invention (100 g/l)

[0427] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 1.651 g/in.sup.3 (100 g/l) on a cordierite substrate sized 4.66*5 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 20 micrometers according to the following method: [0428] (1) 1880 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 158.2 g of a 7.98 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 1286 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2887 g deionized water containing 11 g n-octanol, 169 g 58.4 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 192 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.40 micrometers. [0429] (2) 5090 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La, and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 249.4 g of a 17.20 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1603 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 6767 g of deionized water containing 11 g n-octanol, 395 g 58.4 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 289 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.79 micrometers. [0430] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.8. The final slurry had a viscosity of 24 mPa.Math.s, measured as described in Reference Example 5. [0431] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. then by immersing 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 8: Cold Flow Backpressure Evaluation

[0432] The backpressure of the particulate filter obtained as described in Comparative Examples 1 and 2 and Examples 1 and 3 was measured on a SuperFlow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 700 m.sup.3/h is reported in Table 4.

TABLE-US-00004 TABLE 4 Cold Flow Back Pressure Data Back pressure/mbar Comparative Example 1 65.59 Comparative Example 2 73.68 Example 1 90.30 Example 3 80.53

[0433] While having comparable washcoat loadings, the backpressure obtained Examples 1 and 3 is higher than with Comparative Example 2. This indicates that a portion of washcoat is located on the walls of the inlet passages of the substrate.

Example 9

[0434] The catalysts form Comparative Examples 1 and 2 and Example 1 and 3 were canned. Further, said catalysts were 200 h fuel-cut aged in close-coupled position with 880° C. bed temperature. The performance of the aged catalysts was measured under New European Drive Cycle (NEDC) in close-coupled (CC) position on 2.0 l engine bench. Emission results measured after the respective catalysts are shown in Table 5.

TABLE-US-00005 TABLE 5 HC, CO and NOx emissions Sample HC [g/km] CO [g/km] NOx [g/km] Comparative 0.323 1.988 0.485 Example 1 Comparative 0.262 1.582 0.407 Example 2 Example 1 0.270 1.694 0.366 Example 3 0.290 1.719 0.377

[0435] The catalyst of Comparative Example 1, having a TWC loading of 75 g/l, exhibits higher emissions of HC, CO and NOx compared to the catalysts of Examples 1 and 3, which also have the same TWC catalytic loading. This demonstrates that the oxidic component permits to improve the performance of the catalyst. Further, Table 5 shows that the catalyst of Comparative Example 2, having a TWC loading of 100 g/l, exhibits lower emissions of HC, CO and NOx compared to the catalyst of Comparative Example 1, showing that by increasing the TWC catalyst loading, the emissions of HC, CO and NOx may be reduced. However, the catalyst of Comparative Example 2 also shows lower performance with respect to the NOx emissions compared to the catalysts of Example 1 and Example 3 which have a lower TWC loading.

Comparative Example 3: FWC Catalyst not According to the Invention (in-Wall Coating—150 g/l)

[0436] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 2.494 g/in.sup.3 (150 g/l) on a cordierite substrate sized 4.66*4.65 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers according to the following method: [0437] (1) 2461 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 142.5 g of a 8.60 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 1581 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 3821 g deionized water containing 14 g n-octanol, 223 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 251 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.54 micrometers. [0438] (2) 6673 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 671.6 g of a 18.74 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1383 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 9063 g of deionized water containing 14 g n-octanol, 521 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 376 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.60 micrometers. [0439] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.7. The final slurry had a viscosity of 22.3 mPa.Math.s, measured as described in Reference Example 5. [0440] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. and then by immersing 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 10: FWC Catalyst (120 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 3.38 Micrometers)

[0441] A porous wall-flow substrate, a cordierite substrate sized 4.66*4.65 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 2.002 g/in.sup.3 (120 g/l) according to the following method: [0442] (1) 3734 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to a aqueous solution containing 24460 g deionized water, 38 g n-octanol, 225 g acetic acid, 583 g of 29.7 weight-% zirconium acetate, 291 g of 59.56 weight-% barium acetate and 876 g of 79.00 weight-% boehmite. The pH of the aqueous phase of the resulting slurry was adjusted with acetic acid to 3.5. The particles of the slurry were then milled so that the Dv90 value of the containing particles was 3.38 micrometers. The solid content of the slurry was of 15.12 weight-%. [0443] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0444] (3) 1532 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 110.9 g of a 8.60 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 850 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form the respective metal oxides. The calcined material was added to 2382 g deionized water containing 9 g n-octanol, 139 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 156 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.02 micrometers. [0445] (4) 4221 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 522.8 g of a 18.74 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1125 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form the respective metal oxides. The calcined material was added to 5671 g of deionized water containing 9 g n-octanol, 325 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 234 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.94 micrometers. [0446] (5) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the slurry was adjusted with acetic acid to 3.7. The final slurry had a viscosity of 18.5 mPa.Math.s, measured as described in Reference Example 5. [0447] (6) The coated porous wall-flow substrate obtained from (2) was coated with the slurry (TWC catalytic coating) obtained from (5) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. and then was coating with the slurry obtained from (5) (2.sup.nd TWC catalytic coating) by immersing of 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 11: FWC Catalyst (90 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 3.38 Micrometers)

[0448] A porous wall-flow substrate, a cordierite substrate sized 4.66*4.65 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic with a loading of 1.511 g/in.sup.3 (90 g/l) according to the following method: [0449] (1) The oxidic component was prepared and disposed on the substrate as described in Example 10, (1) and (2). [0450] (2) 1447 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 139.7 g of a 8.60 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 776 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form the respective metal oxides. The calcined material was added to 2255 g deionized water containing 9 g n-octanol, 131 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 147 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 4.79 micrometers. [0451] (3) 3986 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 658.3 g of a 18.74 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 957 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 5397 g of deionized water containing 9 g n-octanol, 307 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 221 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 4.72 micrometers. [0452] (4) The materials obtained from (2) and (3) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.9. The final slurry had a viscosity of 15.8 mPa.Math.s, measured as described in Reference Example 5. [0453] (5) The porous wall-flow substrate obtained after (1) was coated with the slurry obtained from (4) as described in Reference Example 6 hereinabove over 100% of the axial length of the substrate from the inlet end.

Example 12: FWC Catalyst (75 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 3.38 Micrometers)

[0454] A porous wall-flow substrate, a cordierite substrate sized 4.66*4.65 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coating with a loading of 1.265 g/in.sup.3 (75 g/l) according to the following method: [0455] (1) The oxidic component was prepared and disposed on the substrate as described in Example 10, (1) and (2). [0456] (2) 1344 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 155.7 g of a 8.60 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 701 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2098 g deionized water containing 8 g n-octanol, 122 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 137 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 4.83 micrometers. [0457] (3) 3703 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 733.8 g of a 18.74 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 810 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form the respective metal oxides. The calcined material was added to 5045 g of deionized water containing 8 g n-octanol, 285 g 58.5 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 205 g 21.4 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 4.91 micrometers. [0458] (4) The materials obtained from (2) and (3) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.6. The final slurry had a viscosity of 15.8 mPa.Math.s, measured as described in Reference Example 5. [0459] (5) The coated porous wall-flow substrate obtained from (1) was coated with the washcoat obtained from (4) as described in Reference Example 6 hereinabove over 100% of the axial length of the substrate from the inlet end.

Example 13: Cold Flow Backpressure Evaluation

[0460] The backpressure of the particulate filters obtained as described in Comparative Example 1 and 2 and Examples 1 and 3 was measured on a SuperFlow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 700 m.sup.3/h is reported in Table 6.

TABLE-US-00006 TABLE 6 Cold Flow Back Pressure Data Back pressure/mbar Comparative Example 3 85.48 Example 10 101.08 Example 11 103.14 Example 12 98.12

[0461] The higher backpressures obtained with Examples 10 to 12, having the same or inferior total loading, compared to Comparative Example 3 indicate a partial application of washcoat on the walls of the substrate.

Example 14

[0462] The catalysts from Comparative Example 3 and Examples 9 to 11 were canned. Further, they were 200 h fuel-cut aged in close-coupled position with 960° C. bed temperature. The aged catalysts were measured under Federal Test Procedure (FTP75) in close-coupled (CC) position on 2.0 l engine bench. Emission results measured after the respective catalysts are shown in Table 7.

TABLE-US-00007 TABLE 7 HC, CO and NOx emissions Sample HC [g/km] CO [g/km] NOx [g/km] Comparative 0.212 2.017 0.435 Example 3 Example 10 0.168 1.392 0.295 Example 11 0.169 1.505 0.282 Example 12 0.176 1.740 0.327

[0463] The catalysts of Examples 10 to 12 show improved gaseous conversion performance compared to the catalyst of Comparative Example 3. This example shows that even under aged conditions the catalysts according to the present invention permit to obtain reduced HC, CO and NOx emissions which demonstrate that the catalysts of the present invention have an improved thermal stability.

Comparative Example 4: FWC Catalyst not According to the Invention (in-Wall Coating—150 g/l)

[0464] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 2.501 g/in.sup.3 (150 g/l) on a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers according to the following method: [0465] (1) 2807 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 288.7 g of a 8.98 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 1592 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 4459 g deionized water containing 17 g n-octanol, 260 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 297 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.86 micrometer. [0466] (2) 7809 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of micrometer were impregnated with 862.3 g of a 19.23 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 2149 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 10564 g of deionized water containing 17 g n-octanol, 606 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 445 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 4.77 micrometers. [0467] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.7. The final slurry had a viscosity of 20.9 mPa.Math.s, measured as described in Reference Example 5. [0468] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. then by immersing 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 15: FWC Catalyst (120 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 3.18 Micrometers)

[0469] A porous wall-flow substrate, a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 2.009 g/in.sup.3 (120 g/l) according to the following method: [0470] (1) 5291 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to an aqueous solution containing 36706 g deionized water, 57 g n-octanol, 338 g acetic acid, 861 g of 29.7 weight-% zirconium acetate, 434 g of 59.88 weight-% barium acetate and 1315 g of 79.00 weight-% boehmite. The pH of the resulting slurry was adjusted with acetic acid to 3.6. The slurry was then milled so that the Dv90 value of the containing particles was 3.18 micrometers. The solid content of the slurry was of 14.47 weight-%. [0471] (2) The porous wall-flow substrate was coated with a slurry obtained from (1) as described in Reference Example 6. [0472] (3) 2196 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 282.3 g of a 8.98 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 1134 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 3497 g deionized water containing 13 g n-octanol, 203 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 232 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.23 micrometers. [0473] (4) 6109 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (45 weight-% calculated as ZrO.sub.2), and further comprising Nd, La and Y (15 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 31 micrometers were impregnated with 843.3 g of a 18.74 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1573 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 8309 g of deionized water containing 13 g n-octanol, 474 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 348 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.56 micrometers. [0474] (5) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.4. The final slurry had a viscosity of 15.3 mPa.Math.s, measured as described in Reference Example 5. [0475] (6) The coated porous wall-flow substrate was coated with the slurry obtained from (5) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. (TWC catalytic coating) and then by immersing 50% of the axial length of the substrate in the slurry obtained from (5) from the outlet side plus 3 mm (2.sup.nd TWC catalytic coating) followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 16: FWC Catalyst (150 g/l TWC Catalytic Coating+15 g/l Oxidic Component)

[0476] A porous wall-flow substrate, a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 15 g/l prior to the application of the TWC catalytic coatings with a loading of 2.501 g/in.sup.3 (150 g/l) according to the following method: [0477] (1) 6670 g of a highly dispersed boehmite phase aluminium oxide hydroxide (Dv50<0.5 micrometer) 79.00 weight-% was added to an aqueous solution containing 16296 g deionized water, 6 g acetic acid and 132 g n-octanol. The resulting mixture was milled to homogenize the slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.2. Particle size measurement by light scattering was not applicable to this slurry. The solid content of the slurry was of 19.29 weight-%. [0478] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end to the outlet end. [0479] (3) 2005 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 206.2 g of a 8.98 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 1219 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 3185 g deionized water containing 12 g n-octanol, 185 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 212 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.14 micrometers. [0480] (4) 5525 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 616.0 g of a 19.23 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1477 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 7546 g of deionized water containing 12 g n-octanol, 433 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 318 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.51 micrometers. [0481] (5) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.2. The final slurry had a viscosity of 17.0 mPa.Math.s, measured as described in Reference Example 5. [0482] (6) The coated porous wall-flow substrate obtained from (2) was coated with the slurry obtained from (5) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm (TWC catalytic coating) followed by drying and calcining for 3 h at 450° C. then by immersing 50% of the axial length of the substrate in the slurry obtained from (5) from the outlet side plus 3 mm (2.sup.nd TWC catalytic coating) followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 17: Cold Flow Backpressure Evaluation

[0483] The backpressure of the catalysts obtained as described in Comparative Example 4 and Examples 15 and 16 was measured on a SuperFlow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 500 m.sup.3/h is reported in Table 8.

TABLE-US-00008 TABLE 8 Cold Flow Back Pressure Data Back pressure/mbar Comparative Example 4 51.6 Example 15 104.4 Example 16 53.8

[0484] The higher backpressure obtained with Example 15 compared to Comparative Example 4 indicates a partial application of washcoat on the walls of the substrate.

Example 18

[0485] The catalysts of Comparative Example 4 and Examples 15 and 16 were canned and measured under World Light Duty Test Cycle (WLTC) in close-coupled (CC) position on a dynamic engine bench equipped with a 2.0 l direct-injection turbo engine. Emissions of particulate number according to the PMP protocol were measured for full systems and compared to the engine raw emission for calculation of the filtration efficiency. Results are shown in Table 9.

TABLE-US-00009 TABLE 9 WLTC Emission Results on engine bench Particulate Number Filtration Efficiency based (#/km) on engine raw emission Comparative 8.3951E+10 58% Example 4 Example 15 5.2249E+10 74% Example 16 8.1555E+10 59% Engine raw 1.9993E+11 - not applicable - emission

[0486] The catalyst of Example 15 shows improved filtration efficiency compared to Comparative Example 4. The higher filtration efficiency obtained with Example 15 indicates the partial application of washcoat on the walls of the substrate.

Example 19

[0487] The canned catalysts form Comparative Example 4 and Examples 15 and 16 were 100 h fuel-cut aged in close-coupled position with 950° C. inlet temperature. The aged catalysts were measured under World Harmonized Light Duty Test Cycle (WLTC) in close-coupled (CC) position on 2.0 l engine bench. Emission results measured after the respective catalysts are shown in Table 10.

TABLE-US-00010 TABLE 10 HC, CO and NOx emmissions Sample HC [g/km] CO [g/km] NOx [g/km] Comparative 0.86 1.307 0.193 Example 4 Example 15 0.66 0.966 0.134 Example 16 0.065 1.008 0.094

[0488] The catalysts of Examples 15 and 16 show improved gaseous conversion performance compared to the catalyst of Comparative Example 4. This example shows that even under aged conditions the catalysts according to the present invention permit to obtain reduced HC, CO and NOx emissions. This demonstrates that the catalysts of the present invention have an improved thermal stability.

Comparative Example 5: FWC Catalyst not According to the Invention (150 g/l)

[0489] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 2.494 g/in.sup.3 (150 g/l) on a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 63% and average pore size of 20 micrometers according to the following method: [0490] (1) 1629 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 174.2 g of a 8.50 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 968 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2548 g deionized water containing 10 g n-octanol, 148 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 170 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.51 micrometers. [0491] (2) 4419 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 513.0 g of a 18.48 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1168 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 6036 g of deionized water containing 10 g n-octanol, 346 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 255 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.98 micrometers. [0492] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the slurry was adjusted with nitric acid to 3.2. The final slurry had a viscosity of 18.5 mPa.Math.s, measured as described in Reference Example 5. [0493] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. then by immersing 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 20: FWC Catalyst (120 g/l TWC Catalytic Coating+30 g/l Oxidic Component)

[0494] A porous wall-flow substrate, a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 63% and average pore size of 20 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 2.009 g/in.sup.3 (120 g/l) according to the following method: [0495] (1) 6367 g of a highly dispersed boehmite phase aluminium oxide hydroxide (Dv50<0.5 micrometer) 79.40 weight-% was added to an aqueous solution containing 13553 g deionized water and 150 g n-octanol. The resulting mixture was milled to homogenize and obtain a slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.8. Particle size measurement by light scattering was not applicable to this solution. The solid content of the slurry was of 23.88 weight-%. (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0496] (3) 3546 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 474.2 g of a 8.50 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 2072 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 5562 g deionized water containing 21 g n-octanol, 323 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 370 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.62 micrometers. [0497] (4) 9625 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 1396.6 g of a 18.48 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 2365 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 13217 g of deionized water containing 21 g n-octanol, 754 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 555 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.32 micrometers. [0498] (5) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.6. The final slurry had a viscosity of 26.3 mPa.Math.s, measured as described in Reference Example 5. [0499] (6) The coated porous wall-flow substrate obtained from (2) was coated with the slurry obtained from (5) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. (TWC catalytic coating) and then by immersing 50% of the axial length of the substrate in the slurry obtained from (5) from the outlet side plus 3 mm (2.sup.nd TWC catalytic coating) followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 21: FWC Catalyst (120 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 4.51 Micrometers)

[0500] A porous wall-flow substrate, a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 63% and average pore size of 20 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 2.009 g/in.sup.3 (150 g/l) according to the following method: [0501] (1) 4516 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to an aqueous solution containing 10527 g deionized water, 40 g n-octanol, 288 g acetic acid, 608 g of 30.34 weight-% zirconium acetate, 309 g of 59.84 weight-% barium acetate. The pH of the aqueous phase of the resulting slurry was adjusted with nitric acid to 3.4. The slurry was then milled so that the Dv90 value of the containing particles was 4.51 micrometers. The solid content of the slurry was of 19.65 weight-%. (2) The slurry obtained from (1) was coated as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0502] (3) The porous wall-flow substrate obtained from (2) was coated with the TWC slurry obtained from Example 20 (3)-(5) as described in Example 20, (6).

Example 22: FWC Catalyst (120 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 4.83 Micrometers)

[0503] A porous wall-flow substrate, a cordierite substrate sized 4.66*6 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 63% and average pore size of 20 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 2.009 g/in.sup.3 (150 g/l) according to the following method: [0504] (1) 4765 g of a high surface area gamma alumina (BET specific surface area=80 m.sup.2/g; total pore volume=0.42 ml/g) was added to an aqueous solution containing 10905 g deionized water, 42 g n-octanol, 114 g acetic acid, 634 g of 30.34 weight-% zirconium acetate, 321 g of 59.84 weight-% barium acetate. The pH of the aqueous phase of the resulting slurry was adjusted with nitric acid to 3.8. The slurry was then milled so that the Dv90 value of the containing particles was 4.83 micrometers. The solid content of the slurry was of 19.20 weight-%. (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet side. [0505] (3) The porous wall-flow substrate obtained from (2) was coated with the TWC slurry obtained from Example 20 (3)-(5) as described in Example 20, (6).

Example 23: Cold Flow Backpressure Evaluation

[0506] The backpressure of the catalysts obtained as described in Comparative Example 5 and Example 20 to 22 was measured on a SuperFlow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 600 m.sup.3/h is reported in Table 11.

TABLE-US-00011 TABLE 11 Cold Flow Back Pressure Data Back pressure/mbar Comparative Example 5 76.8 Example 20 84.5 Example 21 101.6 Example 22 95.9

[0507] The higher filtration efficiency obtained with Examples 20 to 22 compared to Comparative Example 5 indicates the partial application of washcoat on the walls of the substrate.

Example 24

[0508] Canned catalysts form Comparative Example 5 and Examples 20 to 22 were 100 h fuel-cut aged in close-coupled position with 950° C. inlet temperature. Aged Cans were measured under world light duty test cycle (WLTC) in close-coupled (CC) position on 2.0 l engine bench. Emission results measured after the respective catalysts are shown in Table 12.

TABLE-US-00012 TABLE 12 HC, CO and NOx emissions Sample HC [g/km] CO [g/km] NOx [g/km] Comparative 0.106 0.676 0.127 Example 5 Example 20 0.097 0.687 0.121 Example 21 0.103 0.631 0.094 Example 22 0.094 0.635 0.109

[0509] The catalysts of Examples 20 to 22 show improved gaseous conversion performance compared to the catalyst of Comparative Example 5. This example shows that even under aged conditions the catalysts according to the present invention permit to obtain reduced HC, CO and NOx emissions. This demonstrates that the catalysts of the present invention have an improved thermal stability.

Example 25

[0510] The catalysts of Comparative Example 5 and Examples 20 to 22 were canned and measured under World Light Duty Test Cycle (WLTC) in close-coupled (CC) position on a dynamic engine bench equipped with a 2.0 l direct-injection turbo engine. Emissions of particulate number according to the PMP protocol were measured for full systems and compared to the engine raw emission for calculation of the filtration efficiency. Results are shown in Table 13.

TABLE-US-00013 TABLE 13 WLTC Emission Results on engine bench Particulate Number Filtration Efficiency based (#/km) on engine raw emission Comparative 1.24813E+11   65.9% Example 5 Example 20 9.88E+10 73.1% Example 21 8.24E+10 77.5% Engine raw 3.67E+11 - not applicable - emission

[0511] The catalysts of Examples 20 and 21 shows improved filtration efficiency compared to the catalyst of Comparative Example 5.

Comparative Example 6: FWC Catalyst not According to the Invention (100 g/l)

[0512] A porous wall-flow substrate having a three-way conversion (TWC) catalyst permeating the substrate wall was prepared at a washcoat loading of 1.639 g/in.sup.3 (100 g/l) on a cordierite substrate sized 4.66*4 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers according to the following method: [0513] (1) 1598 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 243.6 g of a 7.27 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 891 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2543 g deionized water containing 10 g n-octanol, 148 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 169 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 5.76 micrometers. [0514] (2) 4433 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) was impregnated with 639 g of a 17.99 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 1123 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 6042 g of deionized water containing 10 g n-octanol, 345 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 254 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.27 micrometers. [0515] (3) The materials obtained from (1) and (2) were combined to form the final TWC slurry. The pH of the slurry was adjusted with nitric acid to 3.2. The final slurry had a viscosity of 28.6 mPa.Math.s, measured as described in Reference Example 5. [0516] (4) The porous wall-flow substrate was coated with the washcoat obtained from (3) as described in Reference Example 6 by immersing 50% of the axial length of the substrate from the inlet side plus 3 mm followed by drying and calcining for 3 h at 450° C. then by immersing 50% of the axial length of the substrate from the outlet side plus 3 mm followed by drying. The coated substrate was then calcined for 3 h at 450° C.

Example 26: FWC Catalyst (70 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 4.85 Micrometers)

[0517] A porous wall-flow substrate, a cordierite substrate sized 4.66*4 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coating with a loading of 1.148 g/in.sup.3 (70 g/l) according to the following method: [0518] (1) 4233 g of a high surface area gamma alumina (BET specific surface area=149 m.sup.2/g; total pore volume=0.535 ml/g) was added to an aqueous solution containing 9867 g deionized water, 38 g n-octanol, 289 g of 59.93 weight-% barium acetate. The pH of the aqueous phase of the resulting slurry was adjusted with nitric acid to 3.3. The slurry was then milled so that the Dv90 value of the containing particles was 4.85 micrometers. The solid content of the slurry was of 28.89 weight-%. [0519] (2) The porous wall-flow substrate was coated with the slurry obtained from (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0520] (3) 1287 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 280.2 g of a 7.27 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 669 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2058 g deionized water containing 8 g n-octanol, 119 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 136 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 4.98 micrometers. [0521] (4) 3558 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 735.8 g of a 17.99 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 733 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 4920 g of deionized water containing 8 g n-octanol, 278 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 204 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 5.25 micrometers. [0522] (5) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.5. The final slurry had a viscosity of 10.3 mPa.Math.s, measured as described in Reference Example 5. [0523] (6) The coated porous wall-flow substrate obtained from (2) was coated with the slurry obtained from (5) as described in Reference Example 6 by immersing 100% of the axial length of the substrate from the inlet followed by drying and calcining for 3 h at 450° C. (TWC catalytic coating). The coated substrate was then calcined for 3 h at 450° C.

Example 27: FWC Catalyst (70 g/l TWC Catalytic Coating+30 g/l Oxidic Component—Dv90 of 4.85 Micrometers)

[0524] A porous wall-flow substrate, a cordierite substrate sized 4.66*4 inches with 300 CPSI (cells per square inch), 8 mill wall thickness, average porosity of 65% and average pore size of 17 micrometers, was coated with an oxidic component with a loading of 30 g/l prior to the application of the TWC catalytic coatings with a loading of 1.148 g/in.sup.3 (70 g/l) according to the following method: [0525] (1) The porous wall-flow substrate was coated with the slurry obtained from Example 26 (1) as described in Reference Example 6 over 100% of the substrate axial length from the inlet end. [0526] (2) 1287 g of a high surface area gamma alumina (BET specific surface area=144 m.sup.2/g; total pore volume=0.843 ml/g; mean pore radius=109 Angstrom) were impregnated with 280.2 g of a 7.27 weight-% aqueous solution of rhodium nitrate (Rh(NO.sub.3).sub.3) with addition of 669 g deionized water. The Rh-impregnated alumina was calcined in air at a temperature of 590° C. for 3 h to form respective metal oxides. The calcined material was added to 2058 g deionized water containing 8 g n-octanol, 119 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 136 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using a continuous milling apparatus so that the Dv90 value of the particles was 13.15 micrometers. [0527] (3) 3558 g of an oxygen storage compound (OSC), a mixed oxide comprising Ce (40 weight-% calculated as CeO.sub.2) and Zr (50 weight-% calculated as ZrO.sub.2), and further comprising La, and Y (10 weight-% in total, each calculated as X.sub.2O.sub.3) and having a Dv90 value of 12.7 micrometers were impregnated with 735.8 g of a 17.99 weight-% aqueous solution of palladium nitrate (Pd(NO.sub.3).sub.2)) together with addition of 733 g of deionized water. The Pd-impregnated OSC was calcined at a temperature of 590° C. to form respective metal oxides. The calcined material was added to 4920 g of deionized water containing 8 g n-octanol, 278 g 58.6 weight-% of barium nitrate (Ba(NO.sub.3).sub.2) and 204 g 21.0 weight-% zirconium nitrate (Zr(NO.sub.3).sub.4). The resulting mixture was milled using the apparatus described above so that the Dv90 value of the particles was 13.13 micrometers. [0528] (4) The materials obtained from (3) and (4) were combined to form the final TWC slurry. The pH of the aqueous phase of the slurry was adjusted with nitric acid to 3.7. The final slurry had a viscosity of 8.82 mPa.Math.s, measured as described in Reference Example 5. [0529] (5) The coated porous wall-flow substrate obtained from (2) was coated with the slurry obtained from (5) as described in Reference Example 6 by immersing 100% of the axial length of the substrate from the inlet followed by drying and calcining for 3 h at 450° C. (TWC catalytic coating). The coated substrate was then calcined for 3 h at 450° C.

Example 28

[0530] The catalysts of Comparative Example 6 and Examples 26 and 27 were canned and measured under World Light Duty Test Cycle (WLTC) in close-coupled (CC) position on a dynamic engine bench equipped with a 2.0 l direct-injection turbo engine. Emissions of particulate number according to the PMP protocol were measured for full systems and compared to the engine raw emission for calculation of the filtration efficiency. Results are shown in Table 14.

TABLE-US-00014 TABLE 14 WLTC Emission Results on engine bench Particulate Number Filtration Efficiency based (#/km) on engine raw emission Comparative 1.81E11 50.7 Example 6 Example 26 1.80E11 51.0 Example 27 1.01E11 72.4 Engine raw 3.67E11 - not applicable - emission

[0531] The catalyst of Example 27 shows improved filtration efficiency compared to the catalyst of Comparative Example 6. This indicates the partial application of washcoat on the walls of the inlet passages of the substrate.

Example 29: Cold Flow Backpressure Evaluation

[0532] The backpressure of the catalysts obtained as described in Comparative Example 6 and Examples 26 and 27 was measured on a SuperFlow Cold Flow bench SF-1020 Superbench at ambient conditions. The backpressure data recorded at a volume flow of 500 m.sup.3/h is reported in Table 15.

TABLE-US-00015 TABLE 15 Cold Flow Back Pressure Data at 500 m.sup.3/h Back pressure/mbar Comparative Example 6 43 Example 26 49 Example 27 113

[0533] The higher backpressure obtained from Example 27 compared to Comparative Example 6 indicates the partial application of washcoat on the walls of the substrate. The backpressure obtained with Example 26 is similar to those obtained with Comparative Example 6, this indicates predominantly in wall coating.

Example 30

[0534] A fresh catalyst from Example 21 was investigated by scanning electron microscopy (SEM). The results of Example 30 are displayed in FIG. 3. In FIG. 3, the arrows a) and b) show the catalytic washcoat (TWC) and the arrow c) shows shows the oxidic component in the pores. It is clearly seen that the washcoat is predominantely located on top of the filter walls whereas the oxidic component is distributed within the filter walls.

BRIEF DESCRIPTION OF THE FIGURES

[0535] FIG. 1 shows the electron microprobe analyses (EMPA) of the four-way conversion catalyst of Example 3.

[0536] FIG. 2 shows the electron microprobe analyses (EMPA) of the four-way conversion catalyst of Comparative Example 1.

[0537] FIG. 3 shows the scanning electron microscopy (SEM) of the four-way conversion catalyst of Example 21.

CITED LITERATURE

[0538] U.S. Pat. No. 8,815,189B2 [0539] WO2018/024546A1 [0540] WO2018/024547A1