Catalytic Gasoline Particulate Filter

Abstract

A washcoat slurry is disclosed that includes 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 1 to 50 μm, an inorganic oxide support, an organic pore former, and a solvent. A method for producing a catalyzed gasoline particulate filter for exhaust gas treatment includes coating a wall-flow filter substrate with the washcoat slurry.

Description

[Technical Field]

[0001] The present invention relates to a method for providing a catalyzed wall-flow filter suitable for use in emissions treatment systems, particularly for positively ignited internal combustion engines such as spark-ignited gasoline engines. The present invention provides a method for manufacturing a gasoline particulate filter having improved filtration efficiency and reduced back pressure. [Background technology]

[0002] A gasoline particulate filter (GPF) is an emissions aftertreatment technology for reducing particulate emissions from gasoline direct injection (GDI) engines.

[0003] Most early GPF applications involved uncoated GPFs positioned downstream of a three-way catalyst (TWC). As the technology matured, GPFs have also been coated with three-way catalysts. See, for example, U.S. Patent No. 10,625,243 (B2), U.S. Patent No. 2020 / 0353410 (A1), U.S. Patent No. 2019 / 0168162 (A1), and U.S. Patent No. 2009 / 0193796 (A1). However, this combination of a catalytic coating on the filter body introduces additional problems, such as excessive backpressure.

[0004] U.S. Patent Application Publication No. 2009 / 0044521(A1) discloses an exhaust gas catalyst including a support and a plurality of layers formed thereon, at least one of the plurality of layers including voids therein, and at least one of the plurality of layers including a catalytic component.

[0005] U.S. Patent Application Publication No. 2017 / 0304810(A1) discloses a method for coating a substrate with a foam, the method including: (a) introducing foam into a substrate having a plurality of channels through open ends of the channels at a first end of the substrate; and (b) optionally (i) applying a vacuum to the open ends of the channels at a second end of the substrate and / or (ii) applying pressure to the open ends of the channels at the first end of the substrate, wherein the foam comprises a particulate material and the foam is particle stabilized.

[0006] US Patent Application Publication No. 2022 / 0280930(A1) discloses a method for producing 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-forming agent, the polymeric pore-forming agent being composed of water-insoluble swellable particles having a water content of 40% to 99.5% by weight, coating the carrier substrate with the coating suspension, and drying and calcining the coated carrier substrate.

[0007] US Patent Application Publication No. 2022 / 0410129(A1) discloses a catalytic washcoat composition comprising a slurry containing at least one platinum group metal and / or at least one non-platinum group metal supported on at least one support, and at least one pore former having a particle size in the range of 100 nm to 5.0 μm, wherein the pore former is selected from carbon nanotubes, carbon nanofibers, activated carbon, resins, cellulose powder, and polymer spheres. U.S. Patent Application Publication No. 2022 / 0410129(A1) also teaches a catalytic article for capturing particulate matter comprising a calcined porous washcoat deposited on a substrate, the calcined porous washcoat comprising at least one platinum group metal and / or at least one non-platinum group metal supported on at least one support, the calcined porous washcoat comprising pores, 50% to 100% of the pores having a pore size in the range of 100 nm to 5.0 μm, and the size of the particulate matter in the range of 1.0 nm to 100 μm.

[0008] The present invention aims to provide a catalytic GPF with improved particulate matter filtering efficiency and improved TWC activity of exhaust gas. Summary of the Invention

[0009] One aspect of the present disclosure is directed to a washcoat slurry, the 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 to 50 μm; (iii) an inorganic oxide support; (iv) an organic pore former; and (v) a solvent.

[0010] Another aspect of the present disclosure is directed to a method of manufacturing a catalyzed gasoline particulate filter (GPF) for treating exhaust gases, 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 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, the wall-flow filter substrate having porous walls, first and second faces defining a longitudinal direction therebetween, and a first and second plurality of channels extending longitudinally, wherein the first plurality of channels are open at the first face and closed at the second face, and the second plurality of channels are open at the second face and closed at the first face; (iii) firing the washcoated substrate to form a gasoline particulate filter.

[0011] Another aspect of the present disclosure is a catalyzed gasoline particulate filter (GPF) for exhaust gases from a gasoline engine, the catalyzed GPF comprising: a wall-flow filter substrate having a porous wall, a first surface and a second surface defining a longitudinal direction therebetween, and a first plurality of channels and a second plurality of channels extending longitudinally, the first plurality of channels being open at the first surface and closed at the second surface, and the second plurality of channels being open at the second surface and closed at the first surface; 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 the second PGM composition, the second OSC material, and the second inorganic carrier; a first TWC coating is formed by firing a first washcoat including a first organic functional material; a second TWC coating is formed by firing a second washcoat including a second organic functional material; a first TWC coating is applied from the first surface; a second TWC coating is applied from the second surface; The first surface is the inlet surface of the catalyzed GPF and the second surface is the outlet surface of the catalyzed GPF.

[0012] Another aspect of the present disclosure is an emissions treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the system including the catalytic GPF disclosed herein. The exhaust system may include additional components, such as a TWC catalyst including a TWC composition, applied to a honeycomb flow-through substrate and positioned either upstream or downstream of the catalytic GPF according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present disclosure will now be further described. In the following sections, different aspects / embodiments of the present disclosure are defined in more detail. Each aspect / embodiment so defined may be combined with any other aspect / embodiment or aspects / embodiments, unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0014] One aspect of the present disclosure is directed to a washcoat slurry, the 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 to 50 μm; (iii) an inorganic oxide support; (iv) an organic pore former; and (v) a solvent.

[0015] The washcoat slurry contains PGMs selected from the group consisting of Pt, Pd, Rh, and mixtures thereof. Preferably, the washcoat slurry contains Pt and Rh, or Pd and Rh. For example, the washcoat slurry may contain Pt and Rh. Alternatively, the washcoat slurry may contain Pd and Rh. The amount of all PGMs in the washcoat slurry may be 0.005 to 10 wt %, preferably 0.001 to 5 wt %, and more preferably 0.05 to 3.0 wt %, based on the total weight of the washcoat slurry.

[0016] The washcoat slurry includes an oxygen storage capacity (OSC) material. "Oxygen storage capacity" refers to the ability of a material used as an oxygen storage capacity material in a catalyst to store oxygen under lean conditions and release oxygen under rich conditions.

[0017] The OSC material can be ceria or a mixed oxide including 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. The term "mixed oxide," as used herein, generally refers to a mixture of oxides in a single phase, as conventionally known in the art.

[0018] The OSC material has a D90 in the range of 1 to 50 μm.

[0019] The particle size distribution of solid particles can be characterized by the D10, D50, and D90 measurements. In each case, the numbers indicate the percentage amount of particles smaller than the stated value. In other words, a D90 of 1 μm means that 90% of the particles are smaller than 1 μm in diameter. Knowing the D10 and D90 values ​​allows one to define the range of particles in the particle distribution. Characterizing the particle size of a sample with D10 and D90 values ​​generally defines the width of the particle size distribution. The closer these values ​​are, the narrower the particle size distribution.

[0020] The particle size measurements required 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 are obtained by D V 50 and D V The particle size distribution is determined by applying the mathematical Mie theory model (also referred to as D(v,0.50) and D(v,0.90)). Laser diffraction systems work by determining the diameter of particles based on a spherical approximation. For particle size measurement by laser diffraction particle size analysis, diluted samples were prepared in surfactant-free distilled water by sonication at 35 watts for 30 seconds.

[0021] The OSC material preferably has a D90 in the range of 2 to 40 μm, more preferably in the range of 3 to 35 μm, and most preferably in the range of 5 to 30 μm.

[0022] The OSC material preferably has a D50 in the range of 0.1 to 30 μm, more preferably in the range of 5 to 10 μm, and most preferably in the range of 1 to 5 μm.

[0023] The washcoat slurry includes an inorganic oxide support. The inorganic oxide support may 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 temperatures associated with the exhaust of a gasoline engine. The inorganic oxide support may 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.

[0024] The inorganic oxide support preferably has a D90 of 5 to 100 μm, more preferably 10 to 90 μm, and most preferably 15 to 80 μm.

[0025] The inorganic oxide support preferably has a D50 of 0.1 to 20 μm, more preferably 0.5 to 10 μm, and most preferably 1 to 5 μm.

[0026] The OSC material and inorganic oxide support in the washcoat slurry may have a weight ratio of 10:1 to 1:10, preferably 5:1 to 1:5, and more preferably 3:1 to 1:3.

[0027] The washcoat slurry contains a solvent. Water and organic solvents (methanol, ethanol, propanol, etc.) or mixtures thereof can be used. Preferably, water is used as the solvent.

[0028] The washcoat slurry may further include a barium component.

[0029] The washcoat slurry includes an organic pore former, which may be selected from the group consisting of cellulose powder, cellulose fibers, polyethylene, starch, graphite, carbon, polypropylene, polyaramid, polytetrafluoroethylene, polystyrene, polymethacrylic-methacrylate, and mixtures thereof. Commercially available organic pore formers include Arbocel®, Vivapur®, Mipelon™ PM-200, Propyltex®, Orgasol®, and Remyrise®.

[0030] The organic pore former may have a D50 in the range of 1 to 30 μm, preferably 2 to 25 μm, more preferably 3 to 20 μm, even more preferably 4 to 18 μm, and most preferably 6 to 12 μm.

[0031] In some embodiments, the organic pore former is a cellulose powder. Preferably, the cellulose powder has a D50 in the range of 6 to 12 μm.

[0032] The washcoat slurry may contain an organic pore former in an amount of 5-40% by weight, preferably 8-35% by weight, more preferably 10-30% by weight based on the crucible solids in the washcoat slurry.

[0033] Another aspect of the present disclosure is directed to a method for producing a catalytic GPF for treating exhaust gases, 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 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, the wall-flow filter substrate having porous walls, first and second faces defining a longitudinal direction therebetween, and a first and second plurality of channels extending longitudinally, wherein the first plurality of channels are open at the first face and closed at the second face, and the second plurality of channels are open at the second face and closed at the first face; (iii) calcining the washcoated substrate to form a catalyzed gasoline particulate filter.

[0034] Washcoat slurries are generally prepared by mixing one or more PGM compounds (e.g., palladium nitrate, platinum nitrate, rhodium nitrate, or other salts of PGM), an oxygen storage capacity (OSC) material, an inorganic oxide support, an organic pore former, and a solvent (e.g., water).

[0035] The method includes coating a wall-flow filter substrate with a washcoat slurry to form a washcoated substrate.

[0036] The wall-flow filter substrate can be a ceramic, such as silicon carbide, cordierite, aluminum nitride, silicon nitride, aluminum titanate, alumina, mullite, pollucite, or a composite material comprising segments of any two or more of these, with cordierite, magnesium aluminosilicate, and silicon carbide being particularly preferred.

[0037] Wall-flow filter substrates suitable for use in the present invention typically have an average pore size of 8 to 45 μm, e.g., 8 to 25 μm, or 10 to 20 μm. Pore size is well known to those skilled in the art, and suitable measurement techniques are known to those skilled in the art. Wall-flow filter substrates may have a porosity of 40 to 75%, e.g., 45 to 70%. Average pore size may be determined using mercury porosimetry and X-ray tomography according to conventional methods.

[0038] Techniques for coating a wall-flow filter substrate with a washcoat slurry to form a washcoated substrate are known in the art. One suitable coating procedure is described in WO 1999047260. The washcoat slurry can be coated onto the wall-flow filter substrate from the inlet face, the outlet face, or both the inlet and outlet faces.

[0039] In some embodiments, a first washcoat slurry is coated from the inlet face of the wall-flow filter substrate to form a first TWC coating in the inlet channels, and a second washcoat slurry is coated from the outlet face of the wall-flow filter substrate to form a second TWC coating in the outlet channels. The first washcoat slurry and the second washcoat slurry can have the same composition. The first TWC coating and the second TWC coating can have the same composition. The "washcoat slurry" described in this disclosure applies to both the "first washcoat slurry" and the "second washcoat slurry."

[0040] After one or both of the first and second TWC coatings have been applied to the wall-flow filter substrate, it may be preferable to dry and / or bake the wall-flow filter substrate containing one coating before applying another coating. A drying step at a lower temperature (e.g., 100-200°C) may be performed before baking. Baking is routine in the art and may be performed under conventional conditions.

[0041] Another aspect of the present disclosure is a catalyzed gasoline particulate filter (GPF) for exhaust gases from a gasoline engine, the catalyzed GPF comprising: a wall-flow filter substrate having a porous wall, a first surface and a second surface defining a longitudinal direction therebetween, and a first plurality of channels and a second plurality of channels extending longitudinally, the first plurality of channels being open at the first surface and closed at the second surface, and the second plurality of channels being open at the second surface and closed at the first surface; 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 the second PGM composition, the second OSC material, and the second inorganic carrier; a first TWC coating is formed by firing a first washcoat including a first organic functional material; a second TWC coating is formed by firing a second washcoat including a second organic functional material; a first TWC coating is applied from the first surface; a second TWC coating is applied from the second surface; The first surface is the inlet surface of the catalyzed GPF and the second surface is the outlet surface of the catalyzed GPF.

[0042] The first TWC coating may cover 10% to 90% of the length of the first plurality of channels. The second TWC coating may cover 10% to 90% of the length of the second plurality of channels. Preferably, the combined length of the first and second TWC coatings is about 100% to 110% of the length of the channels.

[0043] 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.

[0044] Preferably, the first TWC coating and the second TWC coating are predominantly "on-wall."

[0045] The loading of the first TWC coating is 0.2 to 2.5 g / in 3 , preferably 1.0 to 2.0 g / in 3 The loading of the first TWC coating is defined as the weight of the first TWC coating relative to the total volume of the wall-flow filter after firing.

[0046] The loading of the second TWC coating is 0.2 to 2.5 g / in 3 , preferably 1.0 to 2.0 g / in 3 The range may be:

[0047] The first TWC coating is 1-40g / ft 3 within the range of 15 to 30 g / ft 3 within the range of 20 to 25 g / ft 3 The total PGM loading may be in the range of

[0048] The second TWC coating is 1 to 40 g / ft 3 within the range of 15 to 30 g / ft3 within the range of 20 to 25 g / ft 3 The total PGM loading may be in the range of

[0049] Another aspect of the present disclosure is an emissions treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the system including the catalytic GPF disclosed herein. The exhaust system may include additional components, such as a TWC catalyst including a TWC composition, applied to a honeycomb flow-through substrate and positioned either upstream or downstream of the catalytic GPF according to the present invention.

[0050] Preferably, the exhaust system includes a TWC catalyst and a catalyzed GPF disclosed herein, the TWC catalyst being upstream of the catalyzed GPF.

[0051] Comparative Example 1: GPF-1 A washcoat slurry ("Slurry A") was prepared by mixing rhodium nitrate, palladium nitrate, CeZr mixed oxide with a ZrO to CeO weight ratio of approximately 2:1 and a D of 7 μm, La-stabilized alumina component with a D of 13 μm, barium hydroxide, and water. The solids content was approximately 21%.

[0052] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry A from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-1) had a coating density of 1.6 g / in. 3 Washcoat loading of 30g / ft 3 and the Pd:Rh weight ratio was 5:1.

[0053] Example 2: GPF-2 A washcoat slurry ("Slurry B") was prepared by mixing rhodium nitrate, palladium nitrate, CeZr mixed oxide having a ZrO2 to CeO2 weight ratio of about 2:1 and a D90 of 7 μm, La-stabilized alumina component having a D90 of 13 μm, barium hydroxide, cellulose powder (having a D50 of about 8 μm and a D90 of less than 100 μm), and water. The amount of cellulose powder was 25% based on the total weight of the CeZr mixed oxide and La-stabilized alumina. The solids content of the washcoat slurry was about 26%.

[0054] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry B from the inlet and outlet faces. The inlet and outlet washcoat lengths were approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-2) had a 1.6 g / in 3 Washcoat loading of 30g / ft 3 and the Pd:Rh weight ratio was 5:1.

[0055] Comparative Example 3: GPF-3 A washcoat slurry ("Slurry C") was prepared by mixing rhodium nitrate, platinum nitrate, CeZr mixed oxide with a ZrO to CeO weight ratio of approximately 2:1 and a D90 of 7 μm, La-stabilized alumina component with a D90 of 13 μm, citric acid, and water. The solids content was approximately 26%.

[0056] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry C from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-3) had a coating density of 1.6 g / in. 3 Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0057] Comparative Example 4: GPF-4 Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry C from the inlet and outlet faces. The length of the inlet washcoat was approximately 80-85% of the substrate length. The length of the outlet washcoat was approximately 20-25% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-4) had a coating density of 1.6 g / in. 3 Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0058] Example 5: GPF-5 A washcoat slurry ("Slurry D") was prepared by mixing rhodium nitrate, platinum nitrate, CeZr mixed oxide having a ZrO2 to CeO2 weight ratio of about 2:1 and a D90 of 7 μm, La-stabilized alumina component having a D90 of 13 μm, citric acid, cellulose powder (having a D50 of about 8 μm and a D90 of less than 100 μm), and water. The amount of cellulose powder was 12.5% ​​based on the total weight of the CeZr mixed oxide and La-stabilized alumina. The solids content was about 29%.

[0059] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry D from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-5) had a coating density of 1.6 g / in. 3 Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0060] Compared to GPF-3 (prepared without pore-forming agent), the coating layer of GPF-5 is more uniform in thickness.

[0061] Example 6: GPF-6 Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry D from the inlet and outlet faces. The length of the inlet washcoat was approximately 80-85% of the substrate length. The length of the outlet washcoat was approximately 20-25% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-6) had a coating density of 1.6 g / in. 3 Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0062] Example 7: GPF-7 A washcoat slurry ("Slurry E") was prepared by mixing rhodium nitrate, platinum nitrate, CeZr mixed oxide having a ZrO2 to CeO2 weight ratio of about 2:1 and a D90 of 7 μm, La-stabilized alumina component having a D90 of 13 μm, citric acid, cellulose powder (having a D50 of about 8 μm and a D90 of less than 100 μm), and water. The amount of cellulose powder was 25% based on the total weight of the CeZr mixed oxide and La-stabilized alumina. The solids content was about 33%.

[0063] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry D from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-7) had a coating density of 1.6 g / in. 3Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0064] Example 8: GPF-8 Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry E from the inlet and outlet faces. The length of the inlet washcoat was approximately 80-85% of the substrate length. The length of the outlet washcoat was approximately 20-25% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-8) had a 1.6 g / in 3 Washcoat loading of 30g / ft 3 and the Pt:Rh weight ratio was 5:1.

[0065] Comparative Example 9: GPF-9 A washcoat slurry ("Slurry F") was prepared by mixing rhodium nitrate, palladium nitrate, CeZr mixed oxide with a ZrO to CeO weight ratio of approximately 3:2 and a D90 of 13 μm, La-stabilized alumina component with a D90 of 20 μm, barium hydroxide, and water. The solids content was approximately 17%.

[0066] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry F from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-9) had a 0.8 g / in 3 Washcoat loading of 15g / ft 3 and the Pd:Rh weight ratio was 4:1.

[0067] Example 10: GPF-10 A washcoat slurry ("Slurry G") was prepared by mixing rhodium nitrate, palladium nitrate, CeZr mixed oxide having a ZrO to CeO weight ratio of about 3:2 and a D90 of 13 μm, La-stabilized alumina component having a D90 of 20 μm, barium hydroxide, cellulose powder (having a D50 of about 8 μm and a D90 of less than 100 μm), and water. The amount of cellulose powder was 30% based on the total weight of the CeZr mixed oxide and La-stabilized alumina. The solids content was about 21%.

[0068] Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry G from the inlet and outlet faces. The inlet and outlet washcoat lengths were both approximately 50-55% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-10) had a coating density of 0.8 g / in. 3 Washcoat loading of 15g / ft 3 and the Pd:Rh weight ratio was 4:1.

[0069] Example 11: GPF-11 Using the coating process described in WO 1999 / 47260, a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) was coated with Slurry G from the inlet and outlet faces. The length of the inlet washcoat was approximately 80-85% of the substrate length, and the length of the outlet washcoat was approximately 20-25% of the substrate length. After each coating was applied, the coated filter substrate was dried at 100°C. The coated filter substrate was calcined at 500°C for 1 hour. After calcination, the coated filter (GPF-10) had a coating density of 0.8 g / in. 3 Washcoat loading of 15g / ft 3 and the Pd:Rh weight ratio was 4:1.

[0070] Example 12: Performance Test GPF-1 through GPF-8 were oven-aged at 1050°C under lean conditions for 4 hours. GPF-9, GPF-10, and GPF-11 were aged for 45 hours in a closed-couple position after the TWC catalyst, using a single-bricklean spike engine aging cycle with a catalyst inlet temperature setpoint of 950°C. Each filter was installed in an underfloor position on a JLR 2.0L AJ20 P4 engine. Each filter was evaluated over a minimum of three aggressive RDE cycles with cold starts to measure the reduction in gas emissions relative to a reference catalyst. Backpressure differentials and conversion efficiencies for gaseous HC, CO, and NOx emissions were determined using sensors installed upstream and downstream of the filter and upstream and downstream of the direct-coupled TWC.

[0071] Table 1 shows the filtration efficiency and particle number PN / km test results from the JLR RDE drive cycle test for GPF-1 and GPF-2 hydrothermally aged at 1050°C.

[0072] [Table 1]

[0073] 600m measured for GPF-3 to GPF-8 3 The cold flow backpressure (CFBP) at 75 s / h, filtration efficiency at 75 s, and NOx conversion are shown in Table 2.

[0074] [Table 2]

[0075] 600m measured for GPF-9 to GPF-11 3 The cold flow backpressure (CFBP) at 75 s / h and the filtration efficiency at 75 s are shown in Table 3.

[0076] [Table 3]

Claims

1. 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 to 50 μm; c) an inorganic oxide support; d) an organic pore former; and e) a solvent.

2. 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, polyaramid, polytetrafluoroethylene, polystyrene, polymethacrylic-methacrylate, and mixtures thereof.

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

4. 1. A method of manufacturing a gasoline particulate filter (GPF) for treating exhaust gases, 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 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; (iii) firing the washcoated substrate to form a gasoline particulate filter.

5. The method of claim 4, wherein the OSC material has a D90 in the range of 3 to 30 μm.

6. 5. The method of claim 4, wherein the inorganic oxide support has a D90 of 15 to 80 μm.

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

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

9. The method of claim 4 , wherein the organic pore former is a cellulose powder.

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

11. 5. 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 length of the second plurality of channels.

12. 1. A catalyzed gasoline particulate filter (GPF) for exhaust gases from a gasoline engine, said catalyzed GPF comprising: a wall-flow filter substrate having a porous wall, a first surface and a second surface defining a longitudinal direction therebetween, and a first plurality of channels and a second plurality of channels extending in the longitudinal direction, the first plurality of channels being open at the first surface and closed at the second surface, and the second plurality of channels being open at the second surface and closed at the first surface; 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 carrier; the first TWC coating is formed by firing a first washcoat including a first organic functional material; the second TWC coating is formed by firing a second washcoat including a second organic functional material; the first TWC coating is coated from the first surface; the second TWC coating is coated from the second surface; A catalyzed gasoline particulate filter, wherein the first surface is an inlet surface of the catalyzed gasoline particulate filter and the second surface is an outlet surface of the catalyzed gasoline particulate filter.

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

14. 13. The GPF of claim 12, 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 length 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 50-55% of the length of the channel.

16. 13. An emissions treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the emissions treatment system including the catalyzed gasoline particulate filter (GPF) of claim 12.

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