Catalytic gasoline particulate filter

Abstract

Disclosed is a washcoat slurry comprising: a platinum group metal (PGM) selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; an oxygen storage capacity (OSC) material having a D90 in the range of from 1 [mu] m to 50 [mu] m; an inorganic oxide support; an organic pore-forming agent; and a solvent. A method for manufacturing a catalytic gasoline particulate filter for treating exhaust gases includes coating a wall flow filter substrate with the washcoat slurry.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of providing a catalysed wall-flow filter suitable for use in an exhaust treatment system, in particular an exhaust treatment system for a positive ignition internal combustion engine, such as a gasoline spark-ignition engine. The present invention provides a method for manufacturing a gasoline particulate filter having improved filtration efficiency and reduced back pressure. BACKGROUND

[0002] A gasoline particulate filter (GPF) is an exhaust aftertreatment technology used to reduce particulate emissions from gasoline direct injection (GDI) engines.

[0003] The earliest GPF applications included an uncoated GPF positioned downstream of a three-way catalyst (TWC). As technology matured, GPFs were also coated with a three-way catalyst. See, e.g., US 10,625,243 B2, US 2020 / 0353410 Al, US 2019 / 0168162 Al, US 2009 / 0193796 Al. However, the combination of catalyst coating on the filter body does introduce additional issues, such as inadequate back pressure.

[0004] US 2009 / 0044521 Al discloses an exhaust catalyst comprising a carrier and a plurality of layers formed thereon, wherein at least one of the plurality of layers contains voids therein, and at least one of the plurality of layers comprises a catalyst component.

[0005] US 2017 / 0304810 Al discloses a method of coating a substrate with a foam. The method comprises: (a) introducing a foam into a substrate comprising a plurality of channels through an open end of the channels at a first end of the substrate; and (b) optionally applying (i) a vacuum to the open end of the channels at a second end of the substrate and / or (ii) a pressure to the open end of the channels at the first end of the substrate; wherein the foam comprises a particulate material, and wherein the foam is particulate stable.

[0006] US 2022 / 0280930 Al discloses a method of making a porous coating on a carrier substrate by providing a coating suspension having at least one inorganic coating material and at least one polymeric organic pore former, coating the carrier substrate with the coating suspension, and drying and calcining the coated carrier substrate, the at least one polymeric organic pore former being characterized in that the polymeric pore former consists of water-insoluble, swelling particles having a water content of 40 to 99.5 wt.-%.

[0007] WO 2022 / 0410129 A1 discloses a catalyst washcoat composition comprising a slurry and at least one pore former, the slurry comprising at least one platinum group metal and / or at least one non-platinum group metal supported on at least one support; the at least one pore former having a particle size in the range of 100 nm to 5.0 pm, wherein the pore former is selected from the group consisting of carbon nanotubes, carbon nanofibers, activated carbon, resins, cellulose powder, and polymer spheres. US 2022 0410129 A1 further teaches a catalyst article for capturing particulate matter, the catalyst article comprising a calcined porous washcoat layer deposited on a substrate, wherein the calcined porous washcoat layer comprises at least one platinum group metal and / or at least one non-platinum group metal supported on at least one support, wherein the calcined porous washcoat layer comprises 50% to 100% of pores having a pore diameter in the range of 100 nm to 5.0 pm, wherein the size of the particulate matter is in the range of 1.0 nm to 100 pm.

[0008] It is an object of the present invention to provide a catalytic GPF having improved particulate matter filtration efficiency and improved exhaust TWC activity. SUMMARY

[0009] One aspect of the present disclosure relates to a washcoat slurry comprising: (i) a platinum group metal (PGM) selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; (ii) an oxygen storage capacity (OSC) material having a D90 in the range of 1 pm to 50 pm; (iii) an inorganic oxide support; (iv) an organic pore former; and (v) a solvent.

[0010] Another aspect of the present disclosure relates to a method for manufacturing a catalytic gasoline particulate filter (GPF) for treating exhaust gas, the method comprising:

[0011] (i) forming a washcoat slurry comprising: a) a platinum group metal selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; b) an oxygen storage capacity (OSC) material having a D90 in the range of 1 pm to 50 pm;

[0012] c) an inorganic oxide support; d) an organic pore former; and e) a solvent;

[0013] (ii) coating a wall-flow filter substrate with a washcoat slurry to form a washcoated substrate, the wall-flow filter substrate having a porous wall and having a first face and a second face defining a longitudinal direction therebetween; and a first plurality of channels and a second plurality of channels extending in the longitudinal direction, wherein the first plurality of channels are open at the first face and closed at the second face, and wherein the second plurality of channels are open at the second face and closed at the first face; and

[0014] (iii) calcining the washcoated substrate to form a gasoline particulate filter;

[0015] Another aspect of the present disclosure is a catalyzed gasoline particulate filter (GPF) for exhaust from a gasoline engine, the catalyzed GPF comprising:

[0016] a wall-flow filter substrate having a porous wall and having a first face and a second face defining a longitudinal direction therebetween; and a first plurality of channels and a second plurality of channels extending in the longitudinal direction, wherein the first plurality of channels are open at the first face and closed at the second face, and wherein the second plurality of channels are open at the second face and closed at the first face;

[0017] a first TWC coating in the first plurality of channels, the first TWC coating comprising a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support;

[0018] a second TWC coating in the second plurality of channels, the second TWC coating comprising a second PGM composition, a second OSC material, and a second inorganic support;

[0019] wherein the first TWC coating is formed by calcining a first washcoat layer comprising a first organic pore former;

[0020] wherein the second TWC coating is formed by calcining a second washcoat layer comprising a second organic pore former;

[0021] wherein the first TWC coating is applied from the first side;

[0022] wherein the second TWC coating is applied from the second side;

[0023] Wherein the first face is the inlet face of the catalytic GPF, and the second face is the outlet face of the catalytic GPF.

[0024] Another aspect of the present disclosure is an emission treatment system for treating a flow of combustion exhaust gas from a gasoline direct injection engine, the system comprising a catalytic GPF as disclosed herein. The exhaust system can comprise additional components, such as a TWC catalyst containing a TWC composition applied to a honeycomb flow-through substrate and disposed upstream or downstream of the catalytic GPF according to the present application. DETAILED DESCRIPTION

[0025] The present disclosure will now be further described. In the following passages, different aspects / aspects of the present disclosure are defined in more detail. Each aspect / aspects so defined can be combined with any other aspect / aspects or aspects, unless specifically stated otherwise. In particular, any feature indicated as being preferred or advantageous can be combined with any other feature or features indicated as being preferred or advantageous.

[0026] An aspect of the present disclosure relates to a washcoat slurry comprising a platinum group metal (PGM) selected from the group consisting of Pt, Pd, Rh and mixtures thereof; (ii) an oxygen storage capacity (OSC) material having a D90 in the range of 1 pm to 50 pm; (iii) an inorganic oxide support; (iv) an organic pore former; and (v) a solvent.

[0027] The washcoat slurry comprises a PGM selected from the group consisting of Pt, Pd, Rh and mixtures thereof. Preferably, the washcoat slurry comprises Pt and Rh, or Pd and Rh. For example, the washcoat slurry can comprise Pt and Rh. Alternatively, the washcoat slurry can comprise Pd and Rh. The amount of total PGM in the washcoat slurry can be 0.005 wt% to 10 wt%, preferably 0.001 wt% to 5 wt%, more preferably 0.05 wt% to 3.0 wt%, relative to the total weight of the washcoat slurry.

[0028] The washcoat slurry comprises an oxygen storage capacity (OSC) material. By “oxygen storage capacity” is meant the ability of a material used as an oxygen storage capacity material in a catalyst to store oxygen under lean conditions and release it under rich conditions.

[0029] The OSC material can be ceria or a mixed oxide comprising ceria. Preferably, the OSC material comprises a mixed oxide of cerium and zirconium; a mixed oxide of cerium, zirconium and aluminum; a mixed oxide of cerium, zirconium and neodymium; or a mixed oxide of cerium, zirconium and praseodymium. As used herein, the term “mixed oxide” generally refers to a mixture of oxides in a single phase form, as is generally known in the art.

[0030] The OSC material has a D90 in the range of 1 pm to 50 pm.

[0031] The particle size distribution of solid particles can be characterized by D10, D50, and D90 measurements. In each case, the number indicates the percentage of particles smaller than the stated value. In other words, a D90 of 1 μm means that 90% of the particles have a diameter smaller than 1 μm. By knowing D10 and D90, the range of particles within a particle distribution can be defined. Characterizing a sample's particle size by its D10 and D90 values ​​generally defines the width of the particle size distribution. The closer these values ​​are, the narrower the particle size distribution.

[0032] The particle size measurements necessary to obtain D10, D50, and D90 values ​​for solid particles such as OSC materials, inorganic oxide supports, and / or organic pore formers can be obtained by laser diffraction particle size analysis using a Malvern Mastersizer 3000, which is a volume-based technique (i.e., D50 and D90 may also be referred to as D V 50 and D V 90 (or D(v, 0.50) and D(v, 0.90)) and applying the mathematical Mie theory model to determine the particle size distribution. The laser diffraction system works by determining the diameter of the particles based on a spherical approximation. For particle size measurements by laser diffraction particle size analysis, diluted samples were prepared by sonication at 35 watts for 30 seconds in distilled water without surfactant.

[0033] The OSC material preferably has a D90 in the range of 2 μm to 40 μm, more preferably has a D90 in the range of 3 μm to 35 μm, and most preferably has a D90 in the range of 5 μm to 30 μm.

[0034] The OSC material preferably has a D50 in the range of 0.1 μm to 30 μm, more preferably in the range of 5 μm to 10 μm, and most preferably in the range of 1 μm to 5 μm.

[0035] The washcoat slurry comprises an inorganic oxide support. The inorganic oxide support can be an oxide of an element from Groups 2, 3, 4, 5, 13, and 14. The inorganic oxide support is preferably a refractory oxide that exhibits chemical and physical stability at high temperatures, such as those associated with gasoline engine exhaust. The inorganic oxide support can be selected from the group consisting of alumina, silica, titania, and mixed or composite oxides thereof. More preferably, the inorganic oxide support is alumina. In one embodiment, the inorganic oxide support is gamma-alumina.

[0036] The inorganic oxide support preferably has a D90 of 5 μm to 100 μm, more preferably 10 μm to 90 μm, most preferably 15 μm to 80 μm.

[0037] The inorganic oxide support preferably has a D50 of 0.1 pm to 20 pm, more preferably 0.5 pm to 10 pm, most preferably 1 pm to 5 pm.

[0038] The OSC material and the inorganic oxide support in the washcoat slurry can have a weight ratio of 10:1 to 1 :10, preferably 5:1 to 1 :5, more preferably 3:1 to 1 :3.

[0039] The washcoat slurry comprises a solvent. Water and organic solvents (methanol, ethanol, propanol, etc.) or mixtures thereof can be used. Preferably, water is used as the solvent.

[0040] The washcoat slurry can further comprise a barium component.

[0041] The washcoat slurry comprises an organic pore former. The organic pore former can be selected from the group consisting of cellulose powder, cellulose fibers, polyethylene, starch, graphite, carbon, polypropylene, polyaramid, polytetrafluoroethylene, polystyrene, polymethyl methacrylate-methacrylate and mixtures thereof. Commercially available organic pore formers include Mipelon TM PM-200, Pr and

[0042] The organic pore former can have a D50 of 1 pm to 30 pm, preferably 2 pm to 25 pm, more preferably 3 pm to 20 pm, even more preferably 4 pm to 18 pm, most preferably 6 pm to 12 pm.

[0043] In some embodiments, the organic pore former is cellulose powder. Preferably, the cellulose powder has a D50 in the range of 6 pm to 12 pm.

[0044] The washcoat slurry can comprise the organic pore former in an amount of 5 wt.% to 40 wt.%, preferably 8 wt.% to 35 wt.%, more preferably 10 wt.% to 30 wt.% relative to the crucible solids in the washcoat slurry.

[0045] Another aspect of the present disclosure relates to a method for manufacturing a catalytic GPF for treating exhaust gas, the method comprising:

[0046] (i) forming a washcoat slurry, the washcoat slurry comprising: a) a platinum group metal selected from the group consisting of Pt, Pd, Rh and mixtures thereof; b) an oxygen storage capacity (OSC) material having a D90 in the range of 1 pm to 50 pm;

[0047] 90; c) an inorganic oxide support; d) an organic pore former; and e) a solvent;

[0048] (ii) coating a wall-flow filter substrate with a washcoat slurry to form a washcoated substrate, the wall-flow filter substrate having a porous wall and having a first face and a second face defining a longitudinal direction therebetween; and a first plurality of channels and a second plurality of channels extending in the longitudinal direction, wherein the first plurality of channels are open at the first face and closed at the second face, and wherein the second plurality of channels are open at the second face and closed at the first face; and

[0049] (iii) calcining the washcoated substrate to form a catalyzed gasoline particulate filter;

[0050] Washcoat slurries are typically prepared by mixing one or more PGM compounds (eg, palladium nitrate, platinum nitrate, rhodium nitrate, or other salts of PGMs), an oxygen storage capacity (OSC) material, an inorganic oxide support, an organic pore former, and a solvent (eg, water).

[0051] The method includes coating a wall flow filter substrate with a washcoat slurry to form a washcoated substrate.

[0052] The wall-flow filter substrate may be a ceramic such as silicon carbide, cordierite, aluminum nitride, silicon nitride, aluminum titanate, alumina, mullite, cesium garnet, or a composite material comprising segments of any two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0053] Wall-flow filter substrates suitable for use in the present invention typically have an average pore size of 8 μm to 45 μm (e.g., 8 μm to 25 μm, 10 μm to 20 μm). Pore sizes are well known in the art, and appropriate measurement techniques are known to those skilled in the art. The wall-flow filter substrate may have a porosity of 40% to 75% (e.g., 45% to 70%). The average pore size can be determined using mercury intrusion porosimetry and X-ray tomography according to conventional methods.

[0054] The technology of coating a wall-flow filter substrate with a washcoat slurry to form a washcoated substrate is known in the art. A suitable coating procedure is described in WO1999047260. The washcoat slurry can be applied to the wall-flow filter substrate from the inlet face, from the outlet face, or from both the inlet face and the outlet face.

[0055] In some embodiments, a first washcoat slurry is applied from an inlet face of the wall-flow filter substrate to form a first TWC washcoat in the inlet channels; and a second washcoat slurry is applied from an outlet face of the wall-flow filter substrate to form a second TWC washcoat in the outlet channels. The first washcoat slurry and the second washcoat slurry can have the same composition. The first TWC washcoat and the second TWC washcoat can have the same composition. The “washcoat slurry” described in this disclosure applies to both the “first washcoat slurry” and the “second washcoat slurry”.

[0056] After one or both of the first TWC washcoat and the second TWC washcoat is applied to the wall-flow filter substrate, it can be preferable to dry and / or calcine the wall-flow filter substrate containing one washcoat before applying the other washcoat. The drying step can be performed at a lower temperature, such as 100°C to 200°C, before calcination. Calcination is routine in the art and can be performed under typical conditions.

[0057] Another aspect of the disclosure is a catalytic gasoline particulate filter (GPF) for exhaust gas from a gasoline engine, the catalytic GPF comprising:

[0058] a wall-flow filter substrate having porous walls and having a first face and a second face defining a longitudinal direction therebetween; and a first plurality of channels and a second plurality of channels extending in the longitudinal direction, wherein the first plurality of channels are open at the first face and closed at the second face, and wherein the second plurality of channels are open at the second face and closed at the first face;

[0059] a first TWC washcoat in the first plurality of channels, the first TWC washcoat comprising a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic washcoat;

[0060] a second TWC washcoat in the second plurality of channels, the second TWC washcoat comprising a second PGM composition, a second OSC material, and a second inorganic washcoat;

[0061] wherein the first TWC washcoat is formed by calcination of a first washcoat comprising a first organic pore former;

[0062] wherein the second TWC washcoat is formed by calcination of a second washcoat comprising a second organic pore former;

[0063] wherein the first TWC washcoat is applied from the first face;

[0064] wherein the second TWC washcoat is applied from the second face;

[0065] wherein the first face is an inlet face of the catalytic GPF, and the second face is an outlet face of the catalytic GPF.

[0066] The first TWC coating can cover 10% to 90% of the length of the first plurality of channels. The second TWC coating can cover 10% to 90% of the length of the second plurality of channels. Preferably, the sum of the lengths of the first TWC coating and the second TWC coating is about 100% to 110% of the length of the channels.

[0067] Preferably, the first TWC coating covers 75% to 85% of the length of the first plurality of channels, and the second TWC coating covers 15% to 25% of the length of the second plurality of channels. More preferably, the first TWC coating covers 80% to 85% of the length of the first plurality of channels, and the second TWC coating covers 20% to 25% of the length of the second plurality of channels.

[0068] Preferably, the first TWC coating and the second TWC coating are primarily “on-wall”.

[0069] The first TWC coating loading can be in the range of 0.2 g / in 3 to 2.5 g / in 3 , preferably 1.0 g / in 3 to 2.0 g / in 3 . The first TWC coating loading is defined as the weight of the first TWC coating relative to the total volume of the wall flow filter after calcination.

[0070] The second TWC coating loading can be in the range of 0.2 g / in 3 to 2.5 g / in 3 , preferably 1.0 g / in 3 to 2.0 g / in 3 .

[0071] The first TWC coating can have a total PGM loading in the range of 1 g / ft 3 to 40 g / ft 3 , preferably in the range of 15 g / ft 3 to 30 g / ft 3 , more preferably in the range of 20 g / ft 3 to 25 g / ft 3 .

[0072] The second TWC coating can have a total PGM loading in the range of 1 g / ft 3 to 40 g / ft 3 , preferably in the range of 15 g / ft 3 to 30 g / ft 3 , more preferably in the range of 20 g / ft 3 to 25 g / ft 3 .

[0073] Another aspect of the present disclosure is an emission treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the system including a catalyzed GPF as disclosed herein. The exhaust system may include additional components, such as a TWC catalyst comprising a TWC composition applied to a honeycomb flow-through substrate and disposed upstream or downstream of the catalyzed GPF according to the present invention.

[0074] Preferably, the exhaust system includes a TWC catalyst and a catalyzed GPF as disclosed herein, wherein the TWC catalyst is upstream of the catalyzed GPF.

[0075] Comparative Example 1: GPF-1

[0076] A washcoat slurry ("Slurry-A") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide having a weight ratio of ZrO2 to CeO2 of about 2:1 and a D90 of 7 μm, a La-stabilized alumina component having a D90 of 13 μm, barium hydroxide, and water. The solids content was about 21%.

[0077] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-A from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet and outlet washcoat lengths were each approximately 50% to 55% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-1) had a viscosity of 1.6 g / in 3 of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pd:Rh weight ratio of 5:1.

[0078] Example 2: GPF-2

[0079] A washcoat slurry ("Slurry-B") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide having a ZrO2 to CeO2 weight ratio of approximately 2:1 and a D90 of 7 μm, a La-stabilized alumina component having a D90 of 13 μm, barium hydroxide, and cellulose powder (D50 of approximately 8 μm; D90 <100 μm), and water. The amount of cellulose powder was 25% relative to the combined weight of the CeZr mixed oxide and the La-stabilized alumina. The washcoat slurry had a solids content of approximately 26%.

[0080] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-B from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet and outlet washcoat lengths were approximately 50% to 55% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-2) had a viscosity of 1.6 g / in 3 of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pd:Rh weight ratio of 5:1.

[0081] Comparative Example 3: GPF-3

[0082] A washcoat slurry ("Slurry-C") was prepared by mixing rhodium nitrate, platinum nitrate, a CeZr mixed oxide having a weight ratio of ZrO2 to CeO2 of about 2:1 and a D90 of 7 μm, a La-stabilized alumina component having a D90 of 13 μm, citric acid, and water. The solids content was about 26%.

[0083] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-C from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet and outlet washcoat lengths were each approximately 50% to 55% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-3) had a viscosity of 1.6 g / in 3 of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pt:Rh weight ratio of 5:1.

[0084] Comparative Example 4: GPF-4

[0085] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-C from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet washcoat length was approximately 80% to 85% of the substrate length. The outlet washcoat length was approximately 20% to 25% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-4) had a viscosity of 1.6 g / in 3of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pd:Rh weight ratio of 5:1.

[0086] Example 5: GPF-5

[0087] A washcoat slurry ("Slurry-D") was prepared by mixing rhodium nitrate, platinum nitrate, a CeZr mixed oxide having a ZrO2 to CeO2 weight ratio of approximately 2:1 and a D90 of 7 μm, a La-stabilized alumina component having a D90 of 13 μm, citric acid, and cellulose powder (D50 of approximately 8 μm, D90 <100 μm), along with water. The amount of cellulose powder was 12.5% ​​relative to the combined weight of the CeZr mixed oxide and La-stabilized alumina. The solids content was approximately 29%.

[0088] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-D from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet and outlet washcoat lengths were each approximately 50% to 55% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-5) had a viscosity of 1.6 g / in 3 of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pd:Rh weight ratio of 5:1.

[0089] Compared to GPF-3 (prepared without a pore former), the coating thickness of GPF-5 was more uniform.

[0090] Example 6: GPF-6

[0091] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-D from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet washcoat length was approximately 80% to 85% of the substrate length. The outlet washcoat length was approximately 20% to 25% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-6) had a viscosity of 1.6 g / in 3 of washcoat loading and 30g / ft 3 The total PGM loading was 5:1, with a Pd:Rh weight ratio of 5:1.

[0092] Example 7: GPF-7

[0093] A washcoat slurry ("slurry-D") was prepared by mixing rhodium nitrate, platinum nitrate, CeZr mixed oxide with a weight ratio of Zr02to Ce02of about 2: 1 and a D90 of 7 pm, and a La stabilized alumina component with a D90 of 13 pm, citric acid, and cellulose powder (D50 of about 8 pm, D90 < 100 pm), and water. The amount of cellulose powder was 25% relative to the combined weight of the CeZr mixed oxide and the La stabilized alumina. The solids content was about 33%.

[0094] A cordierite wall flow filter substrate (5.2 x 4 inches, 300 / 8, average pore size 15 microns, porosity 65%) was coated from the inlet face and the outlet face with slurry-D using the coating process described in WO 1999 / 47260. The inlet washcoat length and the outlet washcoat length were both about 50% to 55% of the length of the substrate. After each washcoat was applied, the coated filter substrate was dried at 100°C to 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-7) had a washcoat loading of 1.6 g / in 3 and a total PGM loading of 30 g / ft 3 , with a Pd:Rh weight ratio of 5: 1.

[0095] Example 8: GPF-8

[0096] A cordierite wall flow filter substrate (5.2 x 4 inches, 300 / 8, average pore size 15 microns, porosity 65%) was coated from the inlet face and the outlet face with slurry-D using the coating process described in WO 1999 / 47260. The inlet washcoat length and the outlet washcoat length were both about 50% to 55% of the length of the substrate. After each washcoat was applied, the coated filter substrate was dried at 100°C to 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-7) had a washcoat loading of 1.6 g / in 3 and a total PGM loading of 30 g / ft 3 , with a Pd:Rh weight ratio of 5: 1.

[0097] Comparative Example 9: GPF-9

[0098] A washcoat slurry ("slurry-F") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide having a weight ratio of Zr02to Ce02of about 3:2 and a D90 of 13 μιη, and a La stabilized alumina component having a D90 of 20 μιη, barium hydroxide, and water. The solids content was about 17%.

[0099] A cordierite wall flow filter substrate (5.2 x 4 inches, 300 / 8, average pore size 15 microns, porosity 65%) was coated with slurry-F from the inlet face and the outlet face using the coating process described in WO 1999 / 47260. The inlet washcoat length and the outlet washcoat length were each about 50% to 55% of the length of the substrate. After each washcoat was applied, the coated filter substrate was dried at 100°C to 100°C. The coated filter substrate was calcined at 500°C for 1 hour. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-9) had a washcoat loading of 0.8 g / in 3 and a total PGM loading of 15 g / ft 3 , with a Pd:Rh weight ratio of 4: 1.

[0100] Example 10: GPF-10

[0101] A washcoat slurry ("slurry-G") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide having a weight ratio of Zr02to Ce02of about 3:2 and a D90 of 13 μιη, a La stabilized alumina component having a D90 of 20 μιη, barium hydroxide, cellulose powder (D50 of about 8 μιη; D90 < 100 μιη), and water. The amount of cellulose powder was 30% relative to the combined weight of the CeZr mixed oxide and the La stabilized alumina. The solids content was about 21%.

[0102] A cordierite wall flow filter substrate (5.2 x 4 inches, 300 / 8, average pore size 15 microns, porosity 65%) was coated with slurry-G from the inlet face and the outlet face using the coating process described in WO 1999 / 47260. The inlet washcoat length and the outlet washcoat length were each about 50% to 55% of the length of the substrate. After each washcoat was applied, the coated filter substrate was dried at 100°C to 100°C. The coated filter substrate was calcined at 500°C for 1 hour. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-10) had a washcoat loading of 0.8 g / in 3 and a total PGM loading of 15 g / ft 3 , with a Pd:Rh weight ratio of 4: 1.

[0103] Example 11: GPF-11

[0104] A cordierite wall flow filter substrate (5.2 x 4 in, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry-G from both the inlet and outlet faces using the coating process described in WO 1999 / 47260. The inlet washcoat length was approximately 80% to 85% of the substrate length, and the outlet washcoat length was approximately 20% to 25% of the substrate length. After each coating application, the coated filter substrate was dried at 100° C. to 100° C. The coated filter substrate was calcined at 500° C. for 1 hour. After calcination, the coated filter (GPF-10) had a viscosity of 0.8 g / in 3 of washcoat loading and 15g / ft 3 The total PGM loading was 1:1, with a Pd:Rh weight ratio of 4:1.

[0105] Example 12: Performance Test

[0106] GPF-1 to GPF-8 were oven aged at 1050°C for four hours under lean conditions. GPF-9, GPF-10 and GPF-11 were aged in a close-coupled position behind the TWC catalyst using a single-cylinder lean-burn pulse engine aging cycle at a catalyst inlet temperature set point of 950°C for 45 hours. Each filter was installed in the floorpan position of a JLR 2.0L AJ20 P4 engine. Each filter was evaluated in at least three RDE-aggressive cycles with cold starts, measuring the reduction in gaseous emissions relative to the reference catalyst. Backpressure differential and conversion efficiency of gaseous HC, CO and NOx emissions were determined using sensors installed upstream and downstream of the filter and upstream and downstream of the close-coupled TWC.

[0107] Table 1 shows the filtration efficiency and particulate matter number PN / km test results from the JLR RDE drive cycle test of GPF-1 and GPF-2 hydrothermally aged at 1050°C.

[0108] Table 1

[0109]

[0110] Table 2 shows the measured values ​​of GPF-3 to GPF-8 at 600 m. 3 / h cold flow back pressure (CFBP), filtration efficiency at 75s and NOx conversion rate.

[0111] Table 2

[0112]

[0113] Table 3 shows the measured values ​​of GPF-9 to GPF-11 at 600 m. 3Cold flow back pressure (CFBP) at 1 h and filtration efficiency at 75 s.

[0114] Table 3

[0115]

Claims

1. A washcoat slurry comprising: a) a platinum group metal selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; b) an oxygen storage capacity (OSC) material having a D90 in the range of 1 μm to 50 μm; c) an inorganic oxide support; d) an organic pore former; and e) a solvent.

2. The washcoat slurry of claim 1, wherein the organic pore former is selected from the group consisting of cellulose powder, cellulose fiber, polyethylene, starch, graphite, carbon, polypropylene, polyaramide, polytetrafluoroethylene, polystyrene, polymethacrylic acid-methacrylate, and mixtures thereof.

3. The washcoat slurry of claim 1, wherein the organic pore former is cellulose powder.

4. A method for manufacturing a gasoline particulate filter (GPF) for treating exhaust gas, the method comprising: (i) forming a washcoat slurry comprising: a) a platinum group metal selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; b) an oxygen storage capacity (OSC) material having a D90 in the range of 1 μm to 50 μm; c) an inorganic oxide support; d) an organic pore former; and e) a solvent; (ii) coating a wall-flow filter substrate with the washcoat slurry to form a washcoated substrate; as well as (iii) calcining the washcoated substrate to form a gasoline particulate filter. The method of claim 4 , wherein the OSC material has a D90 in the range of 3 μm to 30 μm. The method according to claim 4 , wherein the inorganic oxide support has a D90 of 15 μm to 80 μm.

7. The method of claim 4, wherein the organic pore former is selected from the group consisting of cellulose powder, cellulose fiber, polyethylene, starch, graphite, carbon, polypropylene, polyaramide, polytetrafluoroethylene, polystyrene, polymethacrylic acid-methacrylate, and mixtures thereof.

8. The method of claim 4, wherein the organic pore former has a D50 in the range of 6 μm to 12 μm.

9. The method according to claim 4, wherein the organic pore former is cellulose powder.

10. The method of claim 4, wherein the washcoat slurry comprises the organic pore former in an amount of 10% to 30% by weight relative to crucible solids in the washcoat slurry.

11. The method of claim 4, wherein the first TWC coating covers 80% to 85% of the length of the first plurality of channels, and the second TWC coating covers 20% to 25% of the second plurality of channels.

12. A catalyzed gasoline particulate filter (GPF) for exhaust from a gasoline engine, the catalyzed GPF comprising: a wall-flow filter substrate having a porous wall and having a first side and a second side defining a longitudinal direction therebetween; as well as a first plurality of channels and a second plurality of channels extending in the longitudinal direction, wherein the first plurality of channels are open at the first face and closed at the second face, and wherein the second plurality of channels are open at the second face and closed at the first face; a first TWC coating in the first plurality of channels, the first TWC coating comprising a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support; a second TWC coating in the second plurality of channels, the second TWC coating comprising a second PGM composition, a second OSC material, and a second inorganic support; wherein the first TWC coating is formed by calcining a first washcoat layer comprising a first organic pore former; wherein the second TWC coating is formed by calcining a second washcoat layer comprising a second organic pore former; wherein the first TWC coating is applied from the first side; wherein the second TWC coating is applied from the second side; The first face is an inlet face of the catalytic GPF, and the second face is an outlet face of the catalytic GPF.

13. The GPF of claim 12, wherein the washcoat slurry comprises the organic pore former in an amount of 10 wt% to 30 wt% relative to the crucible solids in the washcoat slurry.

14. The GPF of claim 12, wherein the first TWC coating covers 80% to 85% of the length of the first plurality of channels; and wherein the second TWC coating covers 20% to 25% of the second plurality of channels.

15. The GPF of claim 12, wherein the first TWC coating and the second TWC coating each cover approximately 50% to 55% of the length of the channel.

16. An emissions treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the system comprising the gasoline particulate filter (GPF) according to claim 12.

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