Catalyzed Particulate Filter

Abstract

The present invention relates to catalyzed particulate filters, particularly for use in the emission treatment systems of internal combustion engines. Provided are catalyzed particulate filters, methods of making catalyzed particulate filters, and methods of using catalyzed particulate filters to control emissions in exhaust gases from internal combustion engines.

Description

[Technical Field]

[0001] The present invention relates to catalyzed particulate filters, particularly for use in the emission treatment systems of internal combustion engines. Provided are catalyzed particulate filters, methods of making catalyzed particulate filters, and methods for controlling emissions in exhaust gases from internal combustion engines using catalyzed particulate filters. [Background technology]

[0002] Although the majority of the exhaust gases from most internal combustion engines contain relatively harmless nitrogen (N), water vapor (H2O), and carbon dioxide (CO2), exhaust gases also contain smaller amounts of harmful and / or toxic substances, such as carbon monoxide (CO) from incomplete combustion, hydrocarbons (HC) from unburned fuel, and oxides of nitrogen (NOx) from excessive combustion temperatures.

[0003] Certain internal combustion engines, such as lean burn engines, diesel engines, natural gas engines, power plants, incinerators, or gasoline engines, tend to produce exhaust gases with significant amounts of particulate matter (PM).

[0004] Emissions of pollutants such as unburned hydrocarbons, carbon monoxide, and nitrogen oxides continue to be regulated. Accordingly, catalysts containing platinum group metals (PGMs) are placed in the exhaust line of internal combustion engines. These catalysts promote the oxidation of unburned hydrocarbons and carbon monoxide by oxygen in the exhaust gas stream, and the reduction of nitrogen oxides to nitrogen. The catalyst is formed by uniformly coating a PGM-containing slurry onto a substrate. Another technique involves zone-coating the platinum group metal onto the substrate. Summary of the Invention [Problem to be solved by the invention]

[0005] On December 23, 2016, the Ministry of Environmental Protection (MEP) of the People's Republic of China published the final China 6 Limits and Measurement Methods for Emissions from Light Vehicles (GB18352.6-2016; hereafter referred to as China 6b). This is significantly more stringent than the China 5 emission standards. China 6b, in particular, incorporates particulate matter (PM) limits and adopts on-board diagnostic (OBD) requirements. Furthermore, it mandates that vehicles be tested under the World Harmonized Light-Duty Vehicle Test Cycle (WLTC). The WLTC includes many rapid accelerations and extended high-speed requirements, which require high power output and can lead to "open loop" conditions (i.e., fuel puddle must be fully depressed) for extended periods (e.g., more than 5 seconds) under rich (lambda < 1) or deep rich (lambda < 0.8) conditions. While the standards are becoming more stringent, improved particulate filters are desirable, providing further conversion of pollutants such as NOx, HC, and CO. [Means for solving the problem]

[0006] FIELD OF THE INVENTION The present invention relates to catalyzed particulate filters, and more particularly to catalyzed particulate filters for use in the emission treatment systems of internal combustion engines.

[0007] An embodiment includes a catalyzed particulate filter for treating exhaust gases from an internal combustion engine, comprising a particulate filter and a zoned catalyst layer.

[0008] Another embodiment includes a system for treating exhaust gases from an internal combustion engine including a catalyzed particulate filter and one or more of a selective catalytic reduction (SCR) catalyst, a three-way conversion (TWC) catalyst, a diesel oxidation catalyst (DOC), an ammonia oxidation (AMOx) catalyst, a NOx trap, a NOx absorption catalyst, and a hydrocarbon trap catalyst.

[0009] Other aspects include a method for making a catalyzed particulate filter and a method for treating exhaust gases from an internal combustion engine. [Brief explanation of the drawings]

[0010] [Figure 1] Figures 1(a) and (b) show examples of wall-flow filters. [Figure 2] 2(a), (b), (c), (d), (e), (f) and (g) show the PGM distribution layouts of Examples 1 to 7. [Figure 3] 3(a) and (b) show the PGM distribution layouts of Examples 9 and 10. [Figure 4] 4(a) and (b) show the PGM distribution layouts of Examples 12 and 13. [Figure 5] FIG. 5 shows a plot of gas emission results for catalyzed particulate filters according to embodiments of the present invention (Examples 2-7) and a prior art particulate filter (Example 1) tested on the WLTC cycle. [Figure 6] FIG. 6 shows a plot of gas emission results for a catalyzed particulate filter according to an embodiment of the present invention (Example 10) and a prior art particulate filter (Example 9) tested on the WLTC cycle. [Figure 7] FIG. 7 shows a plot of gas emission results for a catalyzed particulate filter according to an embodiment of the present invention (Example 13) and a prior art particulate filter (Example 12) tested on the WLTC cycle. DETAILED DESCRIPTION OF THE INVENTION

[0011] Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0012] The following definitions are provided for terms used in this disclosure.

[0013] Throughout this specification, including the claims, the terms "including one" or "comprising" should be understood to be synonymous with the term "including at least one," unless otherwise specified, and the terms "between" or "from" should be understood to be inclusive of the limit.

[0014] The terms "a", "an" and "the" are used to refer to one or to more than one (ie, to at least one) of the grammatical object of the article.

[0015] The term "and / or" includes the meanings "and", "or" and all other possible combinations of the elements connected to this term.

[0016] All percentages and ratios are by weight unless otherwise specified.

[0017] Thus, according to one aspect of the present invention, there is provided a catalyzed particulate filter for treating exhaust gases from an internal combustion engine, the filter comprising: (1) a particulate filter comprising a porous substrate having an overall substrate length (L), an inlet surface, an outlet surface, an inlet axial end, and an outlet axial end; (2) A catalyst layer comprising a support material and at least one platinum group metal (PGM) selected from platinum, palladium, and rhodium, coated on the inlet side, outlet side, or both sides of the particulate filter. Including, wherein the catalyst layer includes a first zone, a second zone, and a third zone; the first zone begins at the inlet axial end and has a first length (L1) extending over 10-45% of the total substrate length (L); the third zone begins at the outlet axial end and has a third length (L3) extending over 10-45% of the total substrate length (L); the second zone begins at the axial end of the first zone and ends at the axial beginning of the third zone; and The first zone has a higher PGM content than the second zone, and the third zone has a higher PGM content than the second zone, measured as mass of platinum group metal per zone volume.

[0018] In the following, various aspects of the present invention are defined in more detail. Each aspect thus defined may be used in combination with any other aspect or aspects, unless expressly stated to the contrary. 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. Particulate filters are typically formed from a porous substrate. The porous substrate may comprise a ceramic material, such as cordierite, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, and / or aluminum titanate, typically cordierite or silicon carbide. The porous substrate may be of the type typically used in emission treatment systems for internal combustion engines.

[0019] The internal combustion engine may be a lean burn engine, a diesel engine, a natural gas engine, a power plant, an incinerator, or a gasoline engine.

[0020] The porous substrate may exhibit a conventional honeycomb structure. The filter may take the form of a conventional "through-flow filter." Alternatively, it may take the form of a conventional "wall-flow filter" (WFF). Such filters are known in the art.

[0021] The particulate filter is preferably a wall-flow filter. An example of a wall-flow filter is provided with reference to Figures 1(a) and 1(b). A wall-flow filter works by forcing the exhaust gas flow (13) (containing particulate matter) through a wall made of a porous material.

[0022] Wall-flow filters typically have first and second axial ends defining a longitudinal axis therebetween. In use, one of the first and second axial ends serves as an inlet axial end for exhaust gas (13), and the other serves as an outlet axial end for treated exhaust gas (14). Conventional wall-flow filters have first and second longitudinally extending channels. The first plurality of channels (11) is open at the inlet axial end (01) and closed at the outlet axial end (02). The second plurality of channels (12) is open at the outlet axial end (02) and closed at the inlet axial end (01). The channels are preferably parallel to one another, with a consistent wall thickness between the channels. As a result, gas entering one of the channels at the inlet axial end must diffuse through the channel wall (15) from the inlet side (21) to the outlet side (22) as it exits the monolith into the other channels. The channels are closed by introducing a sealant material into the open ends of the channels. Preferably, the number of channels in the first plurality is equal to the number of channels in the second plurality, with each channel evenly distributed throughout the monolith. Preferably, the wall-flow filter has 100 to 500 channels per square inch, preferably 200 to 400 channels per square inch, in a plane perpendicular to the longitudinal direction. For example, at the inlet axial end (01), the density of open and closed channels is 200 to 400 channels per square inch. The channels can have rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal cross sections.

[0023] In one or more embodiments, the inlet side (21) of the porous wall of the filter, the outlet side (22) of the porous wall of the filter, or both sides (21 and 22) may be coated with a catalyst layer. The loading is characterized as "on-wall" loading or "in-wall" loading. The former is characterized by forming the catalyst layer on the surface of the porous wall (15). The latter is characterized by extending a portion of the catalyst layer through the entire thickness of the porous wall (15).

[0024] In one or more embodiments, the average pore size of the particulate filter is 8 to 24 μm, preferably 10 to 20 μm.

[0025] In one or more embodiments, the PGM is present in a catalytically effective amount to convert NOx, CO, and hydrocarbons in the exhaust gas to N2, CO2, and HO, and to cause oxidation of particulate matter trapped in the particulate filter.

[0026] In one or more embodiments, the particulate filter has a particle density of 0 to 30 g / ft, calculated as metals. 3 of rhodium, 0-100g / ft 3 of platinum, and 0 to 100 g / ft 3 Contains palladium.

[0027] In one or more embodiments, the catalyst layer has a metal content of 2 to 125 g / ft 3 containing PGMs with total precious metal loadings in the range of

[0028] In some embodiments, the first zone comprises palladium and rhodium, the second zone comprises palladium, and the third zone comprises palladium and rhodium.

[0029] In another embodiment, the first zone comprises platinum and rhodium, the second zone comprises platinum, and the third zone comprises platinum and rhodium.

[0030] In another embodiment, the first zone comprises platinum and palladium, the second zone comprises platinum, and the third zone comprises platinum and palladium.

[0031] In another embodiment, the first zone comprises platinum and palladium, the second zone comprises palladium, and the third zone comprises platinum and palladium.

[0032] In another embodiment, the first zone comprises palladium and rhodium, the second zone comprises rhodium, and the third zone comprises palladium and rhodium.

[0033] In another embodiment, the first zone comprises platinum and rhodium, the second zone comprises rhodium, and the third zone comprises platinum and rhodium.

[0034] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises platinum, and the third zone comprises platinum, palladium, and rhodium.

[0035] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises palladium, and the third zone comprises platinum, palladium, and rhodium.

[0036] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises rhodium, and the third zone comprises platinum, palladium, and rhodium.

[0037] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises platinum and palladium, and the third zone comprises platinum, palladium, and rhodium.

[0038] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises palladium and rhodium, and the third zone comprises platinum, palladium, and rhodium.

[0039] In another embodiment, the first zone comprises platinum, palladium, and rhodium, the second zone comprises platinum and rhodium, and the third zone comprises platinum, palladium, and rhodium.

[0040] In one or more embodiments, the catalyst layer comprises from about 50% to about 99.9%, from about 60% to about 99.8%, or from about 70% to about 99.6% by weight of the hydrothermally stable support material, based on the calcined weight of the catalyst layer.

[0041] In one or more preferred embodiments, the catalyst layer comprises, for example, about 5 to about 90 wt. % alumina, preferably about 10 to about 75 wt. % alumina, based on the calcined weight of the catalyst layer.

[0042] In one or more preferred embodiments, the catalyst layer comprises, for example, about 5 to about 70 wt. % zirconia, preferably about 10 to about 40 wt. % zirconia, based on the calcined weight of the catalyst layer.

[0043] In one or more preferred embodiments, the catalyst layer comprises, for example, about 5 to about 60 wt % ceria, preferably about 10 to about 30 wt % ceria, based on the calcined weight of the catalyst layer.

[0044] In a preferred embodiment, the particle size distribution of the hydrothermally stable support material in the catalyst layer of the present invention is in the range of 500 nm to 50 μm. The specific surface area of ​​the hydrothermally stable support material in its virgin state is in the range of 30 to 200 m. 2 / g, and 10-150 m after calcination at 1000°C for 4 h in air. 2 / g.

[0045] Typically, the catalyst layers of the present invention are loaded onto the filter at loadings ranging from at least about 5 g / L, about 10 g / L, about 15 g / L, about 20 g / L, about 25 g / L, or about 30 g / L to about 150 g / L, about 175 g / L, about 200 g / L, about 225 g / L, about 250 g / L, about 275 g / L, about 300 g / L, or about 325 g / L. It is understood that the lower and upper limits disclosed above combine to form catalyst layer loading ranges expressly contemplated by the present invention. In certain exemplary embodiments, catalyst layer loadings range from 10 to 170 g / L.

[0046] In one or more embodiments, the first length (L1) extends over 15-45% of the total substrate length (L). The third length (L3) extends over 15-45% of the total substrate length (L). In particular embodiments, the first length (L1) extends over 20-45% of the total substrate length (L). In more particular embodiments, the first length (L1) extends over 25-40% of the total substrate length (L). The third length (L3) extends over 25-40% of the total substrate length (L).

[0047] In one or more embodiments, the particulate filter is canned. In other embodiments, the filter is not canned. By "canned," it is meant that the particulate filter is incorporated into a housing for incorporation into an exhaust treatment system.

[0048] By "uncanned" it is meant that the particulate filter has not yet been installed in a housing and is still coated with a catalyst layer for installation in an emissions treatment system. In a typical canning process, the particulate filter is sleeved onto a support mat, typically formed of ceramic or alumina fibers, and then installed in a metal housing. Methods for installing particulate filters in metal housings include, for example, "clamshell," "stuffing," and "tourniquet" techniques. Such techniques are known in the art.

[0049] According to another aspect of the present invention, there is provided a system for treating exhaust gases from an internal combustion engine including a catalyzed particulate filter and one or more of a selective catalytic reduction (SCR) catalyst, a three-way conversion (TWC) catalyst, a diesel oxidation catalyst (DOC), an ammonia oxidation (AMOx) catalyst, a NOx trap, a NOx absorption catalyst, and a hydrocarbon trap catalyst.

[0050] As used herein, the terms "selective catalytic reduction" and "SCR" refer to a catalytic process that uses a nitrogen-based reductant to reduce oxides of nitrogen to dinitrogen (N). The SCR catalyst includes at least one material selected from MOR; USY; ZSM-5; ZSM-20; beta-zeolite; CHA; LEV; AEI; AFX; FER; SAPO; ALPO; vanadium; vanadium oxide; titanium oxide; tungsten oxide; molybdenum oxide; cerium oxide; zirconium oxide; niobium oxide; iron; iron oxide; manganese oxide; copper; molybdenum; tungsten; and mixtures thereof. The support structure for the active component of the SCR catalyst includes any suitable zeolite, zeotype, or non-zeolitic compound. Alternatively, the SCR catalyst may include a metal, metal oxide, or mixed oxide as the active component. Transition metal loaded zeolites (eg, copper-chabazite, or Cu-CHA, and copper-levin, or Cu-LEV, and Fe-Beta) and zeotypes (eg, copper-SAPO, or Cu-SAPO) are preferred.

[0051] As used herein, the terms "three-way conversion" and "TWC" refer to catalytic processes capable of substantially removing HC, CO, and NOx from the exhaust gas of a gasoline engine. Typically, TWC catalysts primarily comprise a platinum group metal (PGM), an oxygen storage component (OSC), and a refractory metal oxide support.

[0052] As used herein, the terms "platinum group metal" and "PGM" refer to one or more chemical elements defined in the Periodic Table of the Elements, including platinum, palladium, rhodium, osmium, iridium, and ruthenium, and mixtures thereof.

[0053] In some embodiments, the platinum group metal component of the TWC catalyst is selected from platinum, palladium, rhodium, or mixtures thereof. In specific embodiments, the platinum group metal component of the TWC catalyst comprises palladium.

[0054] In some embodiments, the TWC catalyst does not include an additional platinum group metal (i.e., the TWC includes only one platinum group metal). In other embodiments, the TWC catalyst includes an additional platinum group metal. In one or more embodiments, the additional platinum group metal, if present, is selected from platinum, rhodium, and mixtures thereof. In specific embodiments, the additional platinum group metal component includes rhodium. In one or more specific embodiments, the TWC catalyst includes a mixture of palladium and rhodium. In other embodiments, the TWC catalyst includes a mixture of platinum, palladium, and rhodium.

[0055] As used herein, the terms "oxygen storage component" and "OSC" refer to an entity having multiple valence states and capable of actively reacting with a reducing agent, such as CO or hydrogen, under reducing conditions and then reacting with an oxidizing agent, such as oxygen or nitrogen oxides, under oxidizing conditions. Examples of oxygen storage components include rare earth oxides, particularly ceria, lanthana, praseodymia, neodymia, niobia, europia, samaria, ytterbia, yttria, zirconia, and mixtures thereof, in addition to ceria. Rare earth oxides may be in bulk (e.g., particulate) form. The oxygen storage component may include ceria in a form that exhibits oxygen storage properties. The lattice oxygen of ceria can react with carbon monoxide, hydrogen, or hydrocarbons under rich air-fuel (A / F) conditions. In one or more embodiments, the oxygen storage component for a TWC catalyst comprises a ceria-zirconia composite or a rare earth-stabilized ceria-zirconia.

[0056] As used herein, the terms "refractory metal oxide support" and "support" refer to an underlying high surface area material upon which additional chemical compounds or elements are supported. The support particles have pores greater than 20 A and a broad pore distribution. As defined herein, such supports, e.g., metal oxide supports, exclude molecular sieves, specifically zeolites. In certain embodiments, high surface area refractory metal oxide supports can be utilized, such as alumina support materials, also known as "gamma alumina" or "activated alumina," which typically have a surface area of ​​60 square meters per gram ("m2 / g), often exceeding about 200m 2 / g or less, or even higher. Such activated aluminas are typically mixtures of gamma and delta phases of alumina, but also contain substantial amounts of eta, kappa, and theta alumina phases. Refractory metal oxides other than activated alumina can be used as supports for at least a portion of the catalytic components in a given catalyst. For example, bulk ceria, zirconia, alpha alumina, silica, titania, and other materials are known for such use.

[0057] In some embodiments, the refractory metal oxide support for the TWC catalyst comprises an activating, stabilizing, or both compound independently selected from the group consisting of alumina, zirconia, alumina-zirconia, lanthana-alumina, lanthana-zirconia-alumina, alumina-chromia, ceria, alumina-ceria, and combinations thereof.

[0058] As used herein, the terms "diesel oxidation catalyst" and "DOC" refer to diesel oxidation catalysts known in the art. Diesel oxidation catalysts are designed to oxidize CO to CO and gas-phase HC and the organic fraction (soluble organic fraction) of diesel particulates to CO and HO. Typical diesel oxidation catalysts include platinum and optionally palladium on high surface area inorganic oxide supports such as alumina, silica-alumina, titania, silica-titania, and zeolites. As used herein, the terms include DECs (Diesel Exotherm Catalysts) that generate exotherms.

[0059] As used herein, the terms "ammonia oxidation catalyst" and "AMOx" refer to a catalyst comprising at least one supported precious metal component, such as one or more platinum group metals (PGMs), which is effective for removing ammonia from an exhaust gas stream. In specific embodiments, the precious metal comprises platinum, palladium, rhodium, ruthenium, iridium, silver, or gold. In specific embodiments, the precious metal component comprises a physical mixture, or a chemical or atomically doped combination, of the precious metals.

[0060] The precious metal component is typically deposited on a high surface area refractory metal oxide support. Examples of suitable high surface area refractory metal oxides include alumina, silica, titania, ceria, and zirconia, magnesia, barium oxide, manganese oxide, tungsten oxide, and rare earth metal oxides, base metal oxides, and physical mixtures, chemical combinations, and / or atomically doped combinations thereof.

[0061] As used herein, the terms "NOx adsorber catalyst" and "NOx trap (also referred to as lean NOx trap, or LNT)" refer to catalysts for adsorbing and reducing nitrogen oxide (NO and NO) emissions from lean-burn internal combustion engines. Typical NOx traps contain alkaline earth metal oxides, such as oxides of Mg, Ca, Sr, and Ba; alkali metal oxides, such as oxides of Li, Na, K, Rb, and Cs; and rare earth metal oxides, such as oxides of Ce, La, Pr, and Nd, in combination with a precious metal catalyst, such as platinum, dispersed on an alumina support, for purifying the exhaust gases of internal combustion engines. Barriers are typically preferred for storing NOx because they form nitrates during lean engine operation and release the nitrates relatively easily under rich conditions.

[0062] As used herein, the term "hydrocarbon trap" refers to a catalyst that captures hydrocarbons during low-temperature operation and releases them for oxidation during higher-temperature operation. The hydrocarbon trap may be provided by one or more hydrocarbon (HC) storage components for adsorbing various hydrocarbons (HCs). Typically, hydrocarbon storage materials that have minimal interaction with precious metals can be used, such as microporous materials such as zeolites or zeolite-like materials. Preferably, the hydrocarbon storage material is a zeolite. Beta zeolite is particularly preferred because of its large pore openings, which allow it to effectively capture diesel-derived hydrocarbon molecules. In addition to beta zeolite, other zeolites, such as faujasite, chabazite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM-5 zeolite, and offretite, can be used to improve HC storage during cold-start operation.

[0063] According to another aspect of the present invention, there is provided a method for manufacturing a catalyzed particulate filter, the method comprising the steps of: 1) forming an aqueous slurry comprising a first PGM and a support material, optionally using one or more precursors of that PGM; 2) milling the aqueous slurry and coating it onto a particulate filter; 3) calcining the first PGM coated particulate filter; 4) impregnating the inlet and outlet axial ends of the particulate filter with the second PGM by immersing them in a solution containing the second PGM; 5) Calcining the particulate filter coated with the first PGM and soaking it in a second PGM. Includes:

[0064] In step 1), the precursor of the first PGM may be in the form of a chloride, nitrate, acetate, ammonia or amine complex hydroxide solution, or in the form of a highly dispersed colloidal metal dispersion.

[0065] In step 4), the second PGM may be in the form of a chloride, nitrate, acetate, ammonia or amine complex hydroxide solution, or in the form of a highly dispersed colloidal metal dispersion.

[0066] The calcination temperatures in steps 3) and 5) can be independently set to 250° C. to 1000° C., preferably 300° C. to 700° C., and more preferably 450° C. to 650° C. The calcination period can be set to 10 minutes to 10 hours, preferably 0.5 hours to 8 hours, and more preferably 1 hour to 4 hours.

[0067] Another aspect includes a method for treating exhaust gases from an internal combustion engine, comprising providing a particulate filter and passing exhaust gases from the engine through the particulate filter. Typically, the exhaust gases contain unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter. [Example]

[0068] The present invention is further illustrated by the following examples, which are provided to illustrate the present invention and are not to be construed as limiting thereof. Unless otherwise specified, all parts and percentages are by weight, and unless otherwise specified, all weight percentages are expressed on a dry basis, meaning excluding water content. In each example, the filter substrate was made of cordierite.

[0069] Example 1 - Comparative Example Example 1 has a PGM loading of 25g / ft 3 The particulate filter had a Pd / Rh catalyst layer with a Pd / Rh ratio of 3 / 2. Example 1 was prepared using a single coating from the inlet side of a wall-flow filter substrate. The wall-flow filter substrate had dimensions of 118.4 mm (D) x 127 mm (L), a volume of 1.40 L, a cell density of 300 cells per square inch, a wall thickness of approximately 200 μm, a porosity of 65% by mercury intrusion measurement, and an average pore size of 18 μm.

[0070] The Pd / Rh catalyst layer coated on the substrate contained a prior art three-way catalyst (TWC) composite. The PGM distribution layout is shown in Figure 2(a). The catalyst layer was prepared as follows:

[0071] Palladium in the form of a palladium nitrate solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. Rhodium in the form of a rhodium nitrate solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of barium hydroxide and zirconium nitrate solutions to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto the inlet side of a wall-flow filter substrate using deposition methods known in the art, covering the entire length of the substrate. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Pd / Rh catalyst layer had 24.8 wt. % alumina, 68.5 wt. % ceria-zirconia composite, 0.47 wt. % palladium, 0.23 wt. % rhodium, 4.6 wt. % barium oxide, and 1.4 wt. % zirconia oxide. The total catalyst layer loading was 1.24 g / in 3 It was.

[0072] Example 2 Example 2 is a Pd coating on the substrate from the inlet side to cover the entire length of the substrate, with a Pd loading of 15 g / ft 3 and a first Pd catalyst layer with a local Rh loading of 33.3 g / ft, coated on the substrate from the inlet side and covering 30% of the substrate length. 3 The PGM distribution layout is shown in Figure 2(b).

[0073] The wall-flow filter substrate had dimensions of 118.4 mm (D) x 127 mm (L), a volume of 1.40 L, a cell density of 300 cells per square inch, a wall thickness of approximately 200 μm, a porosity of 65% by mercury intrusion measurement, and an average pore size of 18 μm.

[0074] The first Pd catalyst layer was prepared as follows.

[0075] Palladium in the form of a palladium nitrate solution was impregnated into refractory alumina and a stabilized ceria-zirconia composite (approximately 40% ceria by weight) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of barium hydroxide and zirconium nitrate solutions to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto a wall-flow filter substrate, starting from the inlet side, using deposition methods known in the art, to cover 100% of the substrate's overall length. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Pd catalyst layer had a composition of 24.8% by weight alumina, 68.5% by weight ceria-zirconia composite, 0.70% by weight palladium, 4.6% by weight barium oxide, and 1.4% by weight zirconia oxide. The total catalyst layer loading was 1.24 g / in at 100% of the total substrate volume. 3 It was.

[0076] A second Rh catalyst component was prepared as follows.

[0077] 10g / ft in total 3 of rhodium in the form of a rhodium nitrate solution was deposited on the filter, covering 30% of the substrate length from the inlet axial end of the filter. In this case, the substrate already contained a first Pd catalyst layer. In a subsequent step, the filter was dried at 150°C and then calcined in air at 550°C for approximately 1 hour.

[0078] Example 3 Example 3 was prepared in the same manner as Example 2, except that the second Rh catalyst component was deposited from the outlet axial end to cover 30% of the substrate length from the outlet side. The PGM distribution layout is shown in Figure 2(c).

[0079] Example 4 Example 4 is a Pd coating on the substrate from the inlet side to cover the entire length of the substrate, with a Pd loading of 15 g / ft 3 and a first Pd catalyst layer with a local Rh loading of 50 g / ft coated on the substrate from both the inlet and outlet sides, covering 10% of the substrate's total length on each side. 3 The PGM distribution layout is shown in Figure 2(d).

[0080] Example 4 was prepared in a manner similar to Example 2, except that the second Rh catalyst component was deposited from both the inlet and outlet axial ends, covering 10% of the substrate length from each side.

[0081] Example 5 Example 5 was prepared in a similar manner to Example 4, except that the second Rh catalyst component covered 15% of the substrate length from both the inlet and outlet axial ends. The PGM distribution layout is shown in Figure 2(e).

[0082] Example 6 Example 6 was prepared in a similar manner to Example 4, except that the second Rh catalyst component covered 30% of the substrate length from both the inlet and outlet axial ends. The PGM distribution layout is shown in Figure 2(f).

[0083] Example 7 Example 7 was prepared in a similar manner to Example 4, except that the second Rh catalyst component covered 45% of the substrate length from both the inlet and outlet axial ends. The PGM distribution layout is shown in Figure 2(g).

[0084] The total catalyst layer loading and total precious metal loading for Examples 1 to 7 were the same despite the different PGM distribution layouts, as shown in Table 1.

[0085] [Table 1]

[0086] Example 8 - Catalyst Testing All catalysts prepared in Examples 1-7 were aged using an exothermic aging protocol using an engine configured to operate with a typical inlet temperature of ~875°C and a typical catalyst bed temperature of ~925°C, not exceeding ~980°C. The gas feed composition exiting the engine alternated between rich and lean to simulate typical operating conditions in vehicle durability testing. All catalyzed filters were aged under the same conditions for 150 hours.

[0087] Emissions performance was tested using a 2.0L turbocharged engine in CC-only emission control system configuration operating under WLTC test protocols. Each catalyzed filter was tested at least three times to ensure high experimental repeatability and data consistency.

[0088] The optimal use of solution absorption of a platinum group metal (in this case rhodium) in a filter catalyst is shown in Figure 5. The best performing catalysts of the present invention, Examples 5-7, achieved ~20% less THC, ~20% less CO, and ~25% less NO in WLTC tests compared to Reference Example 1 at the same platinum group metal loading without changing the washcoat support formulation. x This improvement is due to the carefully designed rhodium enrichment zone, where absorption of the PGM solution was carried out at both the inlet and outlet axial ends with an optimal zone length. Examples 2 and 3, in which rhodium was enriched at only one end of the filter section, and Example 4, in which rhodium was enriched at both ends of the filter section but with a very short rhodium zone length, did not demonstrate gas-phase conversion activity comparable to Examples 5-7.

[0089] Example 9 - Comparative Example Example 9 has a PGM loading of 15 g / ft 3 The particulate filter had a Pd / Rh catalyst layer (Pd / Rh=2 / 1). Example 9 was prepared using a single coating from the inlet side of a wall-flow filter substrate. The wall-flow filter substrate had dimensions of 118.4 mm (D) x 127 mm (L), a volume of 1.40 L, a cell density of 300 cells per square inch, a wall thickness of approximately 200 μm, a porosity of 65% by mercury intrusion measurement, and an average pore size of 18 μm.

[0090] The Pd / Rh catalyst layer coated on the substrate contained a prior art three-way conversion (TWC) catalyst composite. The PGM distribution layout is shown in Figure 3(a). The catalyst layer was prepared as follows:

[0091] Palladium in the form of a palladium nitrate solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. Rhodium in the form of a rhodium nitrate solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of barium hydroxide and zirconium nitrate solutions to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto the inlet side of a wall-flow filter substrate using deposition methods known in the art, covering the entire length of the substrate. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Pd / Rh catalyst layer had 24.8 wt. % alumina, 68.5 wt. % ceria-zirconia composite, 0.47 wt. % palladium, 0.23 wt. % rhodium, 4.6 wt. % barium oxide, and 1.4 wt. % zirconia oxide. The total catalyst layer loading was 1.24 g / in 3 It was.

[0092] Example 10 Example 10 is a substrate coated from the inlet side to cover the entire substrate length, with a Rh loading of 5 g / ft 3 and a first Rh catalyst layer having a local Pd loading of 33.3 g / ft coated on the substrate from both the inlet and outlet shaft ends, each covering 30% of the substrate's total length. 3 The PGM distribution layout is shown in Figure 3(b).

[0093] The first Rh catalyst component was prepared as follows.

[0094] Rhodium in the form of a rhodium nitrate solution was impregnated into refractory alumina and a stabilized ceria-zirconia composite (approximately 40% ceria by weight) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of barium hydroxide and zirconium nitrate solutions to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto a wall-flow filter substrate, starting from the inlet side, using deposition methods known in the art, to cover 100% of the substrate's overall length. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Rh catalyst layer had a composition of 24.9% by weight alumina, 68.9% by weight ceria-zirconia composite, 0.23% by weight rhodium, 4.6% by weight barium oxide, and 1.4% by weight zirconia oxide. The total catalyst layer loading was 1.23 g / in at 100% of the total substrate volume. 3 It was.

[0095] A second Pd catalyst component was prepared as follows.

[0096] 10g / ft in total 3was deposited in the form of a palladium nitrate solution onto a filter substrate already containing a first Rh catalyst layer, covering 30% of the substrate length from both the inlet and outlet axial ends. The filter was subsequently dried at 150°C and then calcined in air at 550°C for approximately 1 hour.

[0097] The total catalyst layer loading and total precious metal loading for Examples 9 and 10 were identical despite the different PGM distribution layouts, as shown in Table 1.

[0098] Example 11 - Catalyst Testing Both catalysts prepared in Examples 9 and 10 were aged using an exothermic aging protocol using an engine set to operate with a typical inlet temperature of ∼875°C and a typical catalyst bed temperature of ∼925°C, not exceeding ∼980°C. The gas feed composition exiting the engine alternated between rich and lean to simulate typical operating conditions in a vehicle durability test. All catalyzed filters were aged under the same conditions for 100 hours.

[0099] Emissions performance was tested using a 1.5L turbocharged engine with a CC-only emissions control system configuration operating under the WLTC test protocol. Each catalytic filter was tested at least three times to ensure high experimental repeatability and data consistency.

[0100] The benefit of palladium solution absorption in the optimized layout is shown in Figure 6. Catalyst Example 10 of the present invention reduced THC and NO emissions by 10-15% in WLTC tests compared to Reference Example 9 at the same washcoat loading and total PGM loading. x improvement was achieved.

[0101] Example 12 - Comparative Example Example 12 has a PGM loading of 25 g / ft 3The particulate filter had a Pd / Rh catalyst layer with a Pd / Rh ratio of 3 / 2. Example 12 was prepared using a single coating from the inlet side of a wall-flow filter substrate. The wall-flow filter substrate had dimensions of 118.4 mm (D) x 127 mm (L), a volume of 1.40 L, a cell density of 300 cells per square inch, a wall thickness of approximately 200 μm, a porosity of 65% by mercury intrusion measurement, and an average pore size of 18 μm.

[0102] The Pt / Rh catalyst layer coated on the substrate contained a prior art three-way conversion (TWC) catalyst composite. The PGM distribution layout is shown in Figure 4(a). The catalyst layer was prepared as follows:

[0103] Platinum in the form of a platinum tetraamine oxide solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. Rhodium in the form of a rhodium nitrate solution was impregnated into a refractory alumina and a stabilized ceria-zirconia composite (approximately 40% by weight ceria) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of a barium hydroxide and zirconium nitrate solution to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto the inlet side of a wall-flow filter substrate using deposition methods known in the art, covering the entire length of the substrate. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Pt / Rh catalyst layer had 24.7 wt. % alumina, 68.2 wt. % ceria-zirconia composite, 0.70 wt. % platinum, 0.47 wt. % rhodium, 4.6 wt. % barium oxide, and 1.4 wt. % zirconia oxide. The total catalyst layer loading was 1.24 g / in 3 It was.

[0104] Example 13 Example 13 is a 10 g / ft Rh loading coated on the substrate from the inlet side to cover the entire length of the substrate. 3 and a first Rh catalyst layer having a local Pt loading of 25 g / ft 2 coated on the substrate from both the inlet and outlet shaft ends, each covering 30% of the substrate's total length. 3 The PGM distribution layout is shown in Figure 4(b).

[0105] The first Rh catalyst component was prepared as follows.

[0106] Rhodium in the form of a rhodium nitrate solution was impregnated into refractory alumina and a stabilized ceria-zirconia composite (approximately 40% ceria by weight) using a planetary mixer to form a wet powder while achieving incipient wetness. The powder was added to water, followed by the addition of barium hydroxide and zirconium nitrate solutions to form an aqueous slurry. The slurry was then milled until 90% of the particles were 5 μm in size. This slurry was then coated onto a wall-flow filter substrate, starting from the inlet side, using deposition methods known in the art, to cover 100% of the substrate's overall length. After coating, the filter substrate and inlet coating were dried at 150°C and then calcined at 550°C for approximately 1 hour. The calcined Rh catalyst layer had a composition of 24.8% by weight alumina, 68.7% by weight ceria-zirconia composite, 0.47% by weight rhodium, 4.6% by weight barium oxide, and 1.4% by weight zirconia oxide. The total catalyst layer loading was 1.23 g / in at 100% of the total substrate volume. 3 It was.

[0107] A second Pt catalyst component was prepared as follows.

[0108] 15g / ft in total 3of platinum in the form of a platinum tetraamine oxide solution was deposited onto a filter substrate already containing a first Rh catalyst layer, covering 30% of the substrate length from both the inlet and outlet axial ends. In a subsequent step, the filter was dried at 150°C and then calcined in air at 550°C for approximately 1 hour.

[0109] The total catalyst layer loading and total precious metal loading for Examples 12 and 13 were identical despite the different PGM distribution layouts, as shown in Table 1.

[0110] Example 14 - Catalyst Testing Both catalysts prepared in Examples 12 and 13 were aged using an exothermic aging protocol using an engine set to operate with a typical inlet temperature of ∼875°C and a typical catalyst bed temperature of ∼925°C, not exceeding ∼980°C. The gas feed composition exiting the engine alternated between rich and lean to simulate typical operating conditions in a vehicle durability test. All catalyzed filters were aged under the same conditions for 150 hours.

[0111] Emissions performance was tested using a 2.0L turbocharged engine in CC-only emission control system configuration operating under WLTC test protocols. Each catalyzed filter was tested at least three times to ensure high experimental repeatability and data consistency.

[0112] The benefit of platinum solution absorption in the optimized layout is shown in Figure 7. Inventive catalyst Example 13 reduced CO emissions by 7% and NO emissions by 20% compared to Reference Example 12 in WLTC testing at the same washcoat loading and total PGM loading. x improvement was achieved.

Claims

1. A catalytic particulate filter for treating exhaust gases from an internal combustion engine, (1) A particulate filter comprising a porous substrate having a total length (L) of the substrate, an inlet surface, an outlet surface, an inlet shaft end, and an outlet shaft end. (2) A catalyst layer comprising a support material and at least one platinum group metal (PGM) selected from platinum, palladium, and rhodium, which is coated on the inlet side, outlet side, or both sides of the particulate filter. Includes, Here, the catalyst layer includes a first zone, a second zone, and a third zone. The first zone begins at the inlet shaft end and has a first length (L1) extending over 10-45% of the total length (L) of the substrate; the third zone begins at the outlet shaft end and has a third length (L3) extending over 10-45% of the total length (L) of the substrate; the second zone begins at the shaft end of the first zone and ends at the shaft start point of the third zone; and The PGM content in the first zone is higher than the PGM content in the second zone, and the PGM content in the third zone is higher than the PGM content in the second zone. This amount was determined as the mass of platinum group metals per zone volume. The first zone, the second zone, and the third zone are as follows: Zone 1 contains palladium and rhodium, Zone 2 contains palladium, and Zone 3 contains palladium and rhodium. Zone 1 contains platinum and rhodium, Zone 2 contains platinum, and Zone 3 contains platinum and rhodium. Zone 1 contains platinum and palladium, Zone 2 contains platinum, and Zone 3 contains platinum and palladium. Zone 1 contains platinum and palladium, Zone 2 contains palladium, and Zone 3 contains platinum and palladium. Zone 1 contains palladium and rhodium, Zone 2 contains rhodium, and Zone 3 contains palladium and rhodium. Zone 1 contains platinum and rhodium, Zone 2 contains rhodium, and Zone 3 contains platinum and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains platinum; and Zone 3 contains platinum, palladium, and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains palladium; and Zone 3 contains platinum, palladium, and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains rhodium; and Zone 3 contains platinum, palladium, and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains platinum and palladium; Zone 3 contains platinum, palladium, and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains palladium and rhodium; Zone 3 contains platinum, palladium, and rhodium. Zone 1 contains platinum, palladium, and rhodium; Zone 2 contains platinum and rhodium; Zone 3 contains platinum, palladium, and rhodium. A catalytic particulate filter that satisfies at least one of the following conditions.

2. The catalytic particulate filter according to claim 1, wherein the particulate filter is a wall-flow filter including a honeycomb structure.

3. The catalytic particulate filter according to claim 1 or 2, wherein the average pore size of the particulate filter is 8 to 24 μm.

4. The aforementioned particulate filter, calculated as metal, has a capacity of 0-30 g / (30.48 cm). ３ Rhodium, 0-100g / (30.48cm) ３ Platinum, and 0-100g / (30.48cm) ３ A catalytic particulate filter according to any one of claims 1 to 3, comprising palladium.

5. The catalytic particulate filter according to any one of claims 1 to 4, wherein the catalyst layer has a loading amount in the range of 10 to 170 g / L.

6. A catalytic particulate filter according to any one of claims 1 to 5, wherein the first length (L1) extends over 15 to 45% of the total length (L) of the substrate, and the third length (L3) extends over 15 to 45% of the total length (L) of the substrate.

7. A system for treating exhaust gas from an internal combustion engine, comprising a catalytic particulate filter according to any one of claims 1 to 6, and one or more of the following: a selective catalytic reduction (SCR) catalyst, a ternary conversion (TWC) catalyst, a diesel oxidation catalyst (DOC), an ammonia oxidation (AMOx) catalyst, a NOx trap, a NOx absorption catalyst, and a hydrocarbon trap catalyst.

8. A method for producing a catalytic particulate filter according to any one of claims 1 to 6, The following steps: 1) A step of forming using an aqueous slurry containing a first PGM and a support material, 2) A step of crushing the aqueous slurry and coating it onto the fine particle filter, 3) A step of burning the particulate filter coated with the first PGM, 4) A step of impregnating the particulate filter with the second PGM by immersing the inlet shaft end and outlet shaft end of the particulate filter in a solution containing the second PGM. 5) A step of calcining the particulate filter that has been coated with the first PGM and immersed in the second PGM. A method that includes this.

9. A method for treating exhaust gases from an internal combustion engine, (1) A catalytic particulate filter according to any one of claims 1 to 6, (2) A method comprising passing the exhaust gas from the engine through the catalytic particulate filter.

10. The method according to claim 9, wherein the exhaust gas comprises unburned hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matter.

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