Catalytic Wall-Flow Filter

Abstract

A catalyzed wall-flow filter for exhaust gas from a gasoline engine is disclosed. The catalyzed wall-flow filter includes a wall-flow filter substrate having a porous wall, a first face and a second face defining a longitudinal direction therebetween, and a first and a second plurality of longitudinally extending channels. The first plurality of channels is open at the first face and closed at the second face, and the second plurality of channels is open at the second face and closed at the first face. The filter includes a first TWC coating including a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support; and a second TWC coating including a second PGM composition, a second OSC material, and a second inorganic support.

Description

[Technical Field]

[0001] The present invention relates to a catalytic wall-flow filter suitable for use in automotive emission control systems for vehicles, particularly for externally ignited internal combustion engines such as gasoline spark-ignition engines, which is effective in reducing HC, CO, NOx, and particulate matter emissions. [Background technology]

[0002] Gasoline particulate filters (GPFs) are an emissions aftertreatment technology developed to control particulate emissions from gasoline direct injection (GDI) engines.

[0003] The number of GDI vehicles is increasing, driven by CO2 and / or fuel economy requirements. In 2016, an estimated 60% of new gasoline-powered vehicles in Europe were GDI. The proportion of GDI vehicles is also growing rapidly in North America, where within nine years of their first significant use in the market, GDI penetration rose to 48.5% of new light-duty vehicle sales in the United States. Emissions from the growing GDI fleet are a public health concern and a potentially major source of ambient particulate pollution in populated urban areas.

[0004] 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. This catalyst-coated GPF configuration is sometimes referred to as a four-way catalyst. 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, the combination of a TWC coating on the filter body introduces additional issues, such as excessive backpressure, and there are requirements for minimal CO, NOx, and HC conversion characteristics. Additionally, cost is a consideration, as the best possible balance between performance and cost must be provided.

[0005] Three-way catalysts are intended to catalyze three simultaneous reactions: (i) the oxidation of carbon monoxide to carbon dioxide, (ii) the oxidation of unburned hydrocarbons to carbon dioxide and water, and (iii) the reduction of nitrogen oxides to nitrogen and oxygen. These three reactions occur most efficiently when the TWC receives exhaust gases from an engine operating at or near the stoichiometric point. As is well known in the art, the amount of carbon monoxide, unburned hydrocarbons, and nitrogen oxides emitted when gasoline fuel is burned in an externally ignited (e.g., spark-ignited) internal combustion engine is primarily affected by the air-fuel ratio in the combustion can. Exhaust gases with a stoichiometrically balanced composition contain oxidizing gases (NO x and O2) and reducing gases (HC and CO) are substantially matched. The air-fuel ratio that produces this stoichiometrically balanced exhaust gas composition is typically 14.7:1.

[0006] The active components in a typical TWC include one or both of platinum and palladium in combination with rhodium supported on a high surface area oxide, and an oxygen storage capacity (OSC) material.

[0007] Theoretically, in a stoichiometrically balanced exhaust gas composition, O2, NO xIt should be possible to completely convert CO, CO, and HC to CO, H2O, and N2 (and residual O2), which is the role of the TWC. Ideally, therefore, the engine should be operated in such a way that the air-fuel ratio of the combustion mixture produces a stoichiometrically balanced exhaust gas composition.

[0008] A way to define the compositional balance between oxidizing and reducing gases in the exhaust gas is the lambda (λ) value of the exhaust gas, which can be defined according to the following formula: Lambda (λ) = (actual engine air-fuel ratio) / (stoichiometric air-fuel ratio) A lambda value of 1 represents a stoichiometrically balanced (or stoichiometric) exhaust gas composition, a lambda value greater than 1 represents an excess of O2 and NOx and the composition is described as "lean," and a lambda value less than 1 represents an excess of HC and CO and the composition is described as "rich." It is also common in the art to refer to air-fuel ratios at which an engine operates as "stoichiometric," "lean," or "rich," depending on the exhaust gas composition that the air-fuel ratio produces.

[0009] NO with TWC xIt should be understood that the reduction of CO to N2 is less efficient when the exhaust gas composition is lean or stoichiometric. Similarly, the TWC is less able to oxidize CO and HC when the exhaust gas composition is rich. Therefore, the challenge is to maintain the composition of the exhaust gas entering the TWC as close to stoichiometric as possible. Naturally, ensuring that the air-fuel ratio is stoichiometric when the engine is in steady state is relatively easy. However, when the engine is used to propel a vehicle, the amount of fuel required varies transiently depending on the load demand placed on the engine by the driver. This makes controlling the air-fuel ratio to produce stoichiometric exhaust gas for three-way conversion particularly difficult. In practice, the air-fuel ratio is controlled by an engine control unit that receives information about the exhaust gas composition from an exhaust gas oxygen (EGO) (or lambda) sensor—a so-called closed-loop feedback system. Such systems are characterized by an oscillation (or perturbation) of the air-fuel ratio between a slightly rich stoichiometric (or control set) point and a slightly lean one due to the time lag associated with adjusting the air-fuel ratio. This perturbation is characterized by the amplitude and frequency (Hz) of the air-fuel ratio swing.

[0010] When the exhaust gas composition is slightly richer than the set point, a small amount of oxygen is needed to consume unreacted CO and HC, i.e., to make the reaction more stoichiometric. Conversely, when the exhaust gas is slightly lean, excess oxygen needs to be consumed. This has been achieved by the development of OSC materials that release or absorb oxygen during perturbation. Commonly used OSC materials in modern TWCs are cerium oxide or mixed oxides containing cerium, such as CeZr mixed oxide.

[0011] There is a need to develop technologies that can effectively convert CO, NOx, and HC in the exhaust gas from gasoline engines and reduce particulate matter. Summary of the Invention

[0012] One aspect of the present disclosure is a catalyzed wall-flow filter for exhaust gases from a gasoline engine, comprising: a wall-flow filter substrate having a porous wall, a first face and a second face defining a longitudinal direction therebetween, and a first and second plurality of channels extending longitudinally, the first plurality of channels being open at the first face and closed at the second face, and the second plurality of channels being 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 the second PGM composition, the second OSC material, and the second inorganic carrier; the first PGM composition comprises rhodium in an amount of 50 to 95 wt.%, based on the total weight of the first PGM composition; the second PGM composition comprises palladium in an amount of 90 to 99 wt.%, based on the total weight of the second PGM composition; a first TWC coating is applied from the first surface; a second TWC coating is applied from the second surface; The catalytic wall-flow filter is directed to a catalytic wall-flow filter, wherein the first surface is an inlet surface of the catalytic wall-flow filter and the second surface is an outlet surface of the catalytic wall-flow filter.

[0013] 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 a catalytic wall-flow filter as disclosed herein. Preferably, the exhaust system includes a TWC catalyst and a catalytic wall-flow monolith filter, the TWC catalyst being upstream of the catalytic wall-flow monolith filter.

[0014] According to a further aspect, the present invention provides a method for treating combustion exhaust gases from an externally ignited internal combustion engine, including oxides of nitrogen, carbon monoxide, hydrocarbons, and particulate matter, comprising contacting the exhaust gases with a catalytic wall-flow filter disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] One aspect of the present disclosure is a catalyzed wall-flow filter for exhaust gases from a gasoline engine, comprising: a wall-flow filter substrate having a porous wall, a first face and a second face defining a longitudinal direction therebetween, and a first and second plurality of channels extending longitudinally, the first plurality of channels being open at the first face and closed at the second face, and the second plurality of channels being 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 the second PGM composition, the second OSC material, and the second inorganic carrier; the first PGM composition comprises rhodium in an amount of 50 to 95 wt.%, based on the total weight of the first PGM composition; the second PGM composition comprises palladium in an amount of 90 to 99 wt.%, based on the total weight of the second PGM composition; a first TWC coating is applied from the first surface; a second TWC coating is applied from the second surface; The invention is directed to a catalytic wall-flow filter, wherein a first surface is an inlet surface of the filter and a second surface is an outlet surface of the filter.

[0017] 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.

[0018] 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.

[0019] The catalytic wall-flow filter includes a first TWC coating in a first plurality of channels, the first TWC coating including a first PGM composition, a first oxygen storage capacity (OSC) material, and a first inorganic support.

[0020] "PGM" as used herein refers to "platinum group metals." The term "platinum group metals" generally refers to metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt.

[0021] The first PGM composition preferably comprises Rh and Pd. The first PGM composition may further comprise Pt.

[0022] The first PGM composition comprises Rh in an amount of 50-95 wt.%, preferably 60-90 wt.%, more preferably 65-85 wt.%, and even more preferably 70-80 wt.%, based on the total weight of the first PGM composition.

[0023] The second PGM composition comprises palladium in an amount of 90-99 wt%, preferably 91-98 wt%, more preferably 92-97 wt%, and even more preferably 93-96 wt%, based on the total weight of the second PGM composition. The second PGM composition preferably comprises Rh and Pd. The second PGM component may further comprise Pt.

[0024] "Oxygen storage capacity" refers to the ability of a material used as an oxygen storage material in a catalyst composition to store oxygen under lean conditions and release oxygen under rich conditions.

[0025] The first and second OSC materials may be the same or different. Each of the first and second OSC materials may be ceria or a mixed oxide including ceria. Preferably, each of the first and second OSC materials 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.

[0026] The amount of OSC material in the first TWC coating or the second TWC coating, respectively, can be 5 to 90 wt %, preferably 10 to 80 wt %, based on the total weight of the coating.

[0027] In some embodiments, the first OSC material and the second OSC material each independently comprise an OSC derived from a CeZr mixed oxide sol having a D90 of less than 1.3 microns. The CeZr mixed oxide sol comprises CeZr mixed oxide (CeZr mixed oxide particles or CeZr mixed oxide nanoparticles) dispersed in an aqueous medium.

[0028] Particle size distributions can be characterized by 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 100 microns means that 90% of the particles are smaller than 100 microns in diameter. Knowing the D10 and D90 allows one to define the range of particles in a 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.

[0029] The particle size measurements required to obtain the D10, D50, and D90 values ​​of the CeZr mixed oxide sol and / or particulate inorganic oxide 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 the 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.

[0030] In some embodiments, the D90 of the CeZr mixed oxide sol may be less than 1.2 microns, or less than 1.1 microns, or less than 1.0 microns, or less than 900 nm, or less than 800 nm, or less than 700 nm, or less than 600 nm, or less than 500 nm, or less than 400 nm, or less than 300 nm.

[0031] In some other embodiments, the D90 of the CeZr mixed oxide sol may be 1.2 microns to 1.3 microns, or 1.1 microns to 1.2 microns, or 1.0 microns to 1.1 microns, or 900 nm to 1.0 microns, or 800 nm to 900 nm, or 700 nm to 800 nm, or 600 nm to 700 nm, or 500 nm to 600 nm, or 400 nm to 500 nm, or 300 nm to 400 nm, or 200 nm to 300 nm, or 100 nm to 200 nm.

[0032] The CeZr mixed oxide sol may have a D50 of 100 nm to 700 nm, preferably 200 nm to 600 nm, and more preferably 300 nm to 400 nm.

[0033] Particle size can also be characterized by obtaining the Z-average particle size of a sample. The Z-average is the intensity-weighted average hydrodynamic size of an ensemble collection of particles measured by dynamic light scattering (DLS). The Z-average is derived from cumulant analysis of the measured correlation curve, where a single particle size is assumed and a single exponential fit is applied to the autocorrelation function. The particle size measurements required to obtain the Z-average particle size of CeZr mixed oxide sols can be obtained by dynamic light scattering particle size analysis using a Malvern Zetasizer Nano. All tests are performed in dilute aqueous media, and the harmonic mean hydrodynamic diameter of a sphere of equivalent diffusivity is determined by cumulant analysis of the time dependence of light scattered by randomly moving particles according to the Stokes-Einstein equation.

[0034] The Z-average particle size of the CeZr mixed oxide sol is preferably 150 nm to 350 nm, more preferably 230 to 310 nm.

[0035] The first inorganic oxide support and the second inorganic oxide support may each 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 first inorganic oxide support and the second inorganic oxide support may each be selected from the group consisting of alumina, silica, titania, and mixed or composite oxides thereof. More preferably, the inorganic oxide support is alumina.

[0036] The inorganic oxide support, such as alumina, may be doped with a dopant. The dopant may be selected from the group consisting of La, Sr, Si, Ba, Y, Pr, Nd, Ce, and mixtures thereof. Preferably, the dopant is La, Ba, or Ce. Most preferably, the dopant is La. The dopant content in the inorganic oxide support may be 1 to 30% by weight, preferably 2 to 25% by weight, and more preferably 3 to 20% by weight.

[0037] The D50 of the first or second inorganic material may be in the range of 0.1 to 100 μm, preferably in the range of 0.1 to 50 μm.

[0038] In some embodiments, the first inorganic oxide support is alumina doped with La in an amount of 2 to 25 wt %, more preferably 3 to 20 wt %.

[0039] In some embodiments, the second inorganic oxide support is alumina doped with La in an amount of 2 to 25 wt %, more preferably 3 to 20 wt %.

[0040] The OSC material and the inorganic oxide support in the first TWC coating or the second TWC coating can have a weight ratio of 10:1 to 1:10, preferably 5:1 to 1:5, and more preferably 3:1 to 1:3.

[0041] In some embodiments, the loading of the second TWC coating includes a barium component.

[0042] The first and second TWC coatings are typically applied to the wall-flow filter substrate using a washcoat slurry. One suitable coating procedure is described in WO 1999047260. The first TWC coating is applied from the first side (inlet side). The second TWC coating is applied from the second side (outlet side). Preferably, the second TWC coating is applied from the second side (outlet side) before the first TWC coating is applied from the first side (inlet side) of the wall-flow filter substrate.

[0043] 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.

[0044] The first TWC coating preferably covers 50% to 90%, more preferably 60 to 80%, of the length of the first plurality of channels.

[0045] The second TWC coating preferably covers 30% to 70%, more preferably 40 to 60%, of the length of the second plurality of channels.

[0046] The first TWC coating and the second TWC coating may each be an in-wall coating, an on-wall coating, or a combination of an in-wall coating and an on-wall coating.

[0047] The loading of the first TWC coating is 0.4-0.7 g / in 3 , preferably 0.45 to 0.65 g / in 3The 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.

[0048] The loading of the second TWC coating is 0.4-0.7 g / in 3 , preferably 0.45 to 0.65 g / in 3 The range may be:

[0049] The first TWC coating is 2-12g / ft 3 range, preferably 3 to 10 g / ft 3 range, more preferably 4 to 8 g / ft 3 The total PGM loading may range from 0.1 to 1.0.

[0050] The second TWC coating is 10-40g / ft 3 range, preferably 15 to 30 g / ft 3 in the range of 20 to 25 g / ft 3 The total PGM loading may range from 0.1 to 1.0.

[0051] 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 a catalytic wall-flow filter as 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 wall-flow filter according to the present invention.

[0052] Preferably, the exhaust system includes a TWC catalyst and a catalyzed wall-flow filter as disclosed herein, the TWC catalyst being upstream of the catalyzed wall-flow filter.

[0053] The catalyzed wall-flow filter is effective in reducing hydrocarbon, CO, NOx, and particulate matter emissions.

[0054] According to a further aspect, the present invention provides a method for treating combustion exhaust gases from an externally ignited internal combustion engine, including oxides of nitrogen, carbon monoxide, hydrocarbons, and particulate matter, comprising contacting the exhaust gases with a catalytic wall-flow filter disclosed herein.

[0055] Example 1: GPF-1 A TWC washcoat slurry ("Slurry A") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide sol with a ZrO to CeO weight ratio of approximately 2:1 and a D of less than 1 μm, a La-stabilized alumina component with a D of 5 μm, barium hydroxide, and water. The solids content was approximately 25%.

[0056] Slurry A was coated onto the outlet face of a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, 15 micron average pore size, 65% porosity) using the coating process described in WO 1999 / 47260. The outlet washcoat was approximately 55% of the substrate length and was applied at a rate of 0.6 g / in. 3 The exit washcoat had a total PGM loading of 24 g / ft 3 The Pd:Rh weight ratio was 47:1.

[0057] Another TWC washcoat slurry ("Slurry B") was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide sol having a ZrO to CeO weight ratio of approximately 2:1 and a D of less than 1 μm, a La-stabilized alumina component having a D of 5 μm, and water. The solids content was approximately 25%.

[0058] The wall-flow filter substrate described above, with the outlet channels already coated, was coated from the inlet face with Slurry B. The inlet washcoat was approximately 70% of the substrate length and was applied at a rate of 0.6 g / in 3The inlet washcoat had a total PGM loading of 6 g / ft (after calcination). 3 The Pd:Rh weight ratio was 1:3.

[0059] The coated filter substrate was dried at 100°C and calcined at 500°C for 1 hour. The total PGM loading of GPF-1, including the inlet and outlet coatings, was 30 g / ft 3 The Pd:Rh weight ratio was 5:1.

[0060] Comparative Example 2: GPF-2 The TWC washcoat slurry was prepared by mixing rhodium nitrate, palladium nitrate, a CeZr mixed oxide sol with a ZrO2 to CeO2 weight ratio of approximately 2:1 and a D90 of less than 1 μm, a La-stabilized alumina component with a D90 of 5 μm, barium hydroxide, and water. The solids content was 24%. The coating was applied from each end of a cordierite wall-flow filter substrate (5.2 x 4 inches, 300 / 8, average pore size average 15 microns, porosity 65%) using the coating process described in WO 1999 / 47260. The coating length from each side was approximately 58% of the total substrate length. The amount of washcoat slurry applied to the inlet and outlet channels was the same. The coated filter substrate was dried at 100°C and calcined at 500°C for 1 hour. The coated catalyst filter had a washcoat loading of 1.2 g / in. 3 CeZr mixed oxide and 0.4g / in 3 1.6g / in including La-stabilized alumina component 3 The PGM loading of GPF-2 was 30 g / ft 3 The Pd:Rh weight ratio was 5:1.

[0061] Example 3: Performance testing Each of GPF-1 and GPF-2 was engine-aged for 120 hours using an engine bench aging cycle with the bed temperature controlled at 1050°C in a direct-coupled position after the TWC catalyst. Each filter was installed in an underfloor position in a 2018 MY 2.0L passenger car equipped with a direct-injection gasoline 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 the 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 the direct-coupled TWC. The results, presented below in Table 1, demonstrate that GPF-1 reduced NOx emission levels compared to GPF-2.

[0062] Additionally, SCAT reactor aging was performed on the cores (1 x 4") of GPF-1 and GPF-2 at 1000°C using a four-mode aging cycle. SCAT reactor performance evaluation of the aged cores showed significant differences in NOx light-off, as shown in Table 1.

[0063] [Table 1]

Claims

1. 1. A catalytic wall-flow filter for exhaust gases from a gasoline engine, 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 and 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 PGM composition comprises rhodium in an amount of 50 to 95 wt. %, based on the total weight of the first PGM composition; the second PGM composition comprises palladium in an amount of 90 to 99 wt. %, based on the total weight of the second PGM composition; the first TWC coating is coated from the first surface; the second TWC coating is coated from the second surface; A catalytic wall-flow filter, wherein the first surface is an inlet surface of the catalytic wall-flow filter and the second surface is an outlet surface of the catalytic wall-flow filter.

2. The catalyzed wall-flow filter of claim 1 , wherein the first PGM composition comprises Rh and Pd.

3. 10. The catalyzed wall-flow filter of claim 1, wherein the first PGM composition comprises Rh in an amount of 70 to 80 wt. %, based on the total weight of the first PGM composition.

4. The catalyzed wall-flow filter of claim 1 , wherein the second PGM composition comprises Rh and Pd.

5. 10. The catalyzed wall-flow filter of claim 1, wherein the second PGM composition comprises palladium in an amount of 93 to 96 wt. %, based on the total weight of the second PGM composition.

6. 10. The catalyzed wall-flow filter of claim 1, wherein each of the first OSC material and the second OSC material independently comprises an OSC derived from a CeZr mixed oxide sol having a D90 of less than 1.3 microns.

7. 10. The catalytic wall-flow filter of claim 1, wherein the first inorganic oxide support is alumina doped with La in an amount of 3 to 20 wt. %.

8. 2. The catalytic wall-flow filter of claim 1, wherein the second inorganic oxide support is alumina doped with La in an amount of 3 to 20 wt. %.

9. The catalyzed wall-flow filter of claim 1 , wherein the first TWC coating covers 60-80% of the length of the first plurality of channels.

10. The catalyzed wall-flow filter of claim 1 , wherein the second TWC coating covers 40-60% of the length of the second plurality of channels.

11. The loading of the first TWC coating is 0.45 to 0.65 g / in ３ 10. The catalyzed wall-flow filter of claim 1, wherein the pore size is in the range of

12. the first TWC coating having a coating strength of 4 to 8 g / ft ３ 10. The catalyzed wall-flow filter of claim 1 having a total PGM loading in the range of:

13. The loading of the second TWC coating is 0.45 to 0.65 g / in ３ 10. The catalyzed wall-flow filter of claim 1, wherein the pore size is in the range of

14. The second TWC coating has a coating thickness of 20 to 25 g / ft ３ 10. The catalyzed wall-flow filter of claim 1 having a total PGM loading in the range of:

15. 10. An emissions treatment system for treating a combustion exhaust gas stream from a gasoline direct injection engine, the system comprising the catalyzed wall-flow filter of claim 1.

16. 16. The emissions treatment system of claim 15, further comprising a TWC catalyst comprising a TWC composition applied to the honeycomb flow-through substrate.

17. 17. The emissions treatment system of claim 16, wherein the TWC catalyst is located upstream of the catalytic wall-flow filter.

18. 10. A method for treating combustion exhaust gases from an externally ignited internal combustion engine, including oxides of nitrogen, carbon monoxide, hydrocarbons, and particulate matter, comprising contacting the exhaust gases with the catalytic wall-flow filter of claim 1.

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