Method for manufacturing catalytic filters

Abstract

A method for manufacturing a catalytic filter for an exhaust gas treatment system comprises: i) providing a porous filter body; ii) providing a wash coat comprising (a) one or more platinum group metals (PGMs), (b) a support material, and (c) a surfactant; iii) coating the filter body with the wash coat to form a coated filter body; and iv) firing the coated filter body to form a catalytic filter, wherein the surfactant is a nonionic, silicon-free organic surfactant.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a catalytic filter suitable for use in exhaust gas treatment systems, such as those for automobiles. In particular, this method addresses problems arising from treatments sometimes added to filter substrates, improving the filtration performance and operating life of the filter substrate without compromising the benefits of those treatments. [Background technology]

[0002] The provision of filter components is well known in exhaust gas treatment systems. These take the form of so-called wall-flow filters. Wall-flow filters consist of a porous material substrate having multiple longitudinally extending channels within it. Typically, half of these channels are blocked at the inlet end and the other half at the outlet end. As a result, exhaust gas passing through the open inlet channel is forced to pass through the porous wall and enter the outlet channel, exiting the filter. Consequently, soot and other particulate matter can accumulate on the filter wall. The simplest diesel particulate filters (DPFs) are simply formed from porous material, but more modern advances have led to the provision of catalytic coatings on the filter body. These can help regenerate the filter by catalyzing the combustion of soot, or they can be present to have other catalytic benefits to components in the exhaust gas. Other well-known types of filters include catalytic soot filters (CSFs), gasoline particulate filters (GPFs), and selective catalytic reduction filters (SCRFs). All of these are well-known in the art and have characteristic formulations and components.

[0003] In recent years, several developments have been made regarding coatings on filter substrates to improve their filtration performance and lifespan. At least some of these coatings are applied to the inlet channel of a filter to form a surface layer that enhances the filtration activity of the underlying porous channel wall. These coatings may contain silica-based materials and may function to reduce the interaction between the filter portion and components in the exhaust gas.

[0004] International Publication No. 2014137827 discloses a catalyst washcoat with improved porosity. This process involves incorporating an oil-in-water macroemulsion into a catalyst slurry before washcoating a carrier substrate, and then calcining the washed-coated carrier substrate to remove the oil-in-water macroemulsion. The O / W emulsion is formed and stabilized with an organic surfactant, which, like the oil, is removed by calcination in the final step. The removal of the oil by calcination helps to form a porous structure.

[0005] U.S. Patent No. 9,687,786 discloses a diesel particulate filter capable of removing soot from exhaust gases while operating at low back pressure, the filter comprising (a) a wall-flow filter substrate having an average pore size, an inlet side, an outlet side, and a porous interior between the inlet and outlet sides, and (b) a catalyst composition coated on the inlet side of the substrate. The catalyst composition has a D50 particle size distribution smaller than the average pore size divided by 4.9, and the outlet side is substantially free of the catalyst coating.

[0006] German Patent No. 102007002903 discloses the use of a surfactant as a foaming aid in a catalyst washcoat suspension for forming an automotive catalytic converter. The surfactant is then associated with a gas treatment or degassing process.

[0007] U.S. Publication No. 2019 / 299139 discloses an exhaust gas purification filter that suppresses the increase in pressure loss associated with the formation of a catalyst layer and has good PM combustion quality.

[0008] U.S. Publication No. 2004 / 176246 discloses a catalytic filter and a method for arranging a catalyst on a filter medium, which involves positioning the catalyst on the filter medium in contact with the material to be catalyzed during the filtration process.

[0009] Japanese Patent Publication No. 2002361099 discloses a method for producing an inorganic fiber catalyst that exhibits sufficient catalytic activity by uniformly depositing catalytically active components onto an inorganic fiber structure.

[0010] International Publication No. 2012099868 discloses an exhaust system and components suitable for use with a gasoline engine to treat gaseous emissions such as hydrocarbons, nitrogen oxides, and carbon monoxide.

[0011] U.S. Publication No. 2022 / 258137 discloses a catalyst article comprising a substrate having a plurality of passages, further comprising a first oxidation region and a second oxidation region comprising a first subset and a second subset of the plurality of passages.

[0012] The applicant's International Publication No. 2023 / 026022(A1) discloses a method for forming an inorganic oxide coating on a monolithic article. The coated monolithic article is suitable for exhaust gas treatment. The method involves spraying inorganic particles and a silicone resin as a dry particulate aerosol to form a coating layer.

[0013] There is a need to address the problems related to providing washcoats having porous substrates treated with hydrophobic treatment, or to address problems related to the prior art, or at least to provide alternatives. [Overview of the project]

[0014] According to the first aspect, a method for manufacturing a catalytic filter for an exhaust gas treatment system, wherein the method is i) To provide a porous filter body, ii) A wash coat, (a) One or more platinum group metals (PGMs) (b) Support material and (c) To provide a wash coat containing a surfactant, iii) Coating the filter body with a wash coat to form a coated filter body, iv) Including firing the coated filter body to form a catalytic filter, A method is provided in which the surfactant is a nonionic, silicon-free organic surfactant. [Modes for carrying out the invention]

[0015] Herein lies a further explanation of this disclosure. Different aspects / embodiments of this disclosure are defined in more detail in the following sections. Each of the aspects / embodiments defined in this way may be combined with any other aspects / embodiments or more aspects / embodiments unless otherwise expressly indicated. In particular, any feature shown as preferred or advantageous may be combined with any other or more features shown as preferred or advantageous. Features disclosed in relation to a method may be combined with features disclosed in relation to use, and vice versa.

[0016] The inventors found that some of their products had a problem in that the applied washcoat slurry could not have a sufficiently strong interaction with the substrate, which led to difficulties in scaling up prototype production and insufficient catalytic performance in the final product. For example, there was a loss of washcoat slurry control, and a considerable portion of the washcoat slurry flowed along the length of the substrate channel without passing through the porous channel wall. In further investigation, it was found that these problems were related to modern pretreatments applied to the substrates discussed above, such as pre-coating the filter inlet channel with a surface layer to enhance the filtration activity of the underlying porous channel wall. The inventors found that the pretreatment had the inevitable increase in the hydrophobicity of the component.

[0017] The inventors attempted various solutions to the problems of applying washcoat slurry. They investigated whether it was possible to minimize the interaction of water with the inherent hydrophobicity of the substrate by reducing the water content of the washcoat. This resulted in a thicker, more viscous washcoat and a relative increase in washcoat solids. Similarly, the inventors focused on increasing the washcoat viscosity by including rheological modifiers such as gums, without necessarily adjusting the washcoat solids. While both approaches could improve the ability to control the flow of the washcoat and thus improve its position along the length of the substrate channel, the ability to penetrate the washcoat solids into the wall, i.e., laterally, was consequently reduced. The higher the washcoat solids on the wall, the higher the back pressure, which hindered the desired position of the PGM within the wall.

[0018] Other contemplated solutions included additional treatment of the substrate to reduce the apparent hydrophobicity of the substrate. However, this was found to impair the advantages inherent in the applied pretreatment. One approach included a pre-firing step, which was found to increase production costs and reduce production plant capacity because the parts required an increase in the manufacturing process steps. Further, the resulting products had a performance reduction in that the effectiveness of the initially applied pretreatment was impaired.

[0019] Ultimately, the inventors have found that careful selection of a specific surfactant can address the problem without necessarily adjusting the washcoat solids. While it is known to use some surfactants, it is not conventional to add a surfactant to a washcoat composition. This is because it is highly desirable to not include additives that do not have a technical benefit in the washcoat slurry. Including unnecessary additives not only increases the cost of the washcoat, but can also adversely affect the catalytic activity of the ultimately fired washcoat, for example, by affecting the location of the PGM in the final product. Indeed, these adverse effects were seen in the inventors' tests for certain surfactants and certain surfactant concentrations. Therefore, using a surfactant when preparing a PGM-containing washcoat for a filter is considered particularly unusual.

[0020] The inventors have found that by carefully selecting a surfactant, it is possible to address the problems that arise. This means that the inventors can arrive at a catalyzed filter that benefits from both the pretreatment of the substrate to improve its filtration performance and, at the same time, maintaining the catalytic activity of the applied catalyst coating. <000009o>

[0021] The method relates to the manufacture of a catalytic filter for an exhaust gas treatment system. The catalytic filter is a component of an exhaust gas treatment system through which the exhaust gas to be treated passes through the filter body. The filter body functions to remove particulate matter. The catalytic filter has catalytic properties by application of a washcoat containing a PGM material.

[0022] The method includes step (i) of providing a porous filter body. Preferably, the porous filter body is a wall-flow filter. The porous filter body can be made of a ceramic, such as silicon carbide, cordierite, aluminum nitride, silicon nitride, aluminum titanate, alumina, mullite, perlite, or a composite material containing any two or more of these segments. Preferably, the porous filter body is composed of silicon carbide (SiC), cordierite, or aluminum titanate. Preferably, the porous filter body has a hydrophobic coating applied thereto, and preferably, the method further includes applying a hydrophobic surface coating to the porous filter body before step (iii). The hydrophobic coating is preferably applied only to the surface of the inlet channels of the wall-flow filter.

[0023] To determine whether a porous filter body would particularly benefit from this method, it is useful to evaluate whether it is hydrophobic or has been subjected to a hydrophobic treatment. Preferably, the porous filter body provided in step (i) has a water contact angle greater than 90° when measured by the washburn method. The method is well known in the art and a good summary is available at https: / / www.kruss-scientific.com / en / know-how / glossary / washburn-method. For testing the porous filter body, the core is removed from the substrate, held in a force tensile meter, e.g., Kruess Tensio, with a special clip, brought into contact with the test liquid, the liquid is drawn into the substrate, and the change in mass with respect to time is determined. The first test liquid used is one that has optimal wetting where the contact angle is assumed to be 0° (e.g., n-heptane), and the washburn constant c is determined. Once the washburn constant c is found, the contact angles of other test liquids having known surface tension, viscosity, and density can be determined. Contact angles greater than 90° cannot be measured using this method because wetting does not occur. Therefore, the absence of a contact angle value for water on the substrate indicates that the contact angle is greater than 90° and the substrate is considered hydrophobic. This is not the case with conventional untreated filter substrates; in fact, conventional SiC or cordierite substrates wet very easily, making it difficult to measure values ​​close to zero.

[0024] Preferably, the hydrophobic surface coating is applied to the inlet channel of the porous filter body, preferably only to the inlet channel. Then, the wash coat is applied to the inlet and / or outlet channels. The length and extent of each wash coat coating depend on the desired catalytic performance. Applying the wash coat coating to the outlet channel helps reduce the initial hydrophobicity and repulsion of the substrate when in contact with the wash coat coating. It should be noted that although the wash coat coating is applied to the inlet or outlet channel, the material forming the wash coat coating may diffuse to some extent into and through the pores of the porous body. Preferably, the total length of the wash coat coating applied to the inlet and / or outlet channels is at least 100% of the longitudinal length of the porous filter body. That is, if only the outlet coating is present, preferably this is 100% of the longitudinal length of the porous filter body.

[0025] A preferred embodiment provides an inlet wash coat coating extending from the inlet end of the porous filter body along 50-90% of the longitudinal length of the porous filter body, and an outlet coating extending from the outlet end of the porous filter body along 50-10% of the longitudinal length of the porous filter body. A more preferred embodiment provides an inlet coating extending from the inlet end of the porous filter body along 70-80% of the longitudinal length of the porous filter body, and an outlet coating extending from the outlet end of the porous filter body along 30-20% of the longitudinal length of the porous filter body.

[0026] The method includes step (ii) providing a wash coat. Methods for forming and applying wash coats are well known in the art, and any suitable method may be used in conjunction with the present invention. Typically, the composition is an aqueous wash coat, and the components are added and dispersed before the coating step. The wash coat may contain conventional additives such as thickeners and acidity modifiers. Preferably, surfactants are added as the final component to minimize the opportunity for them to affect the PGM in the wash coat.

[0027] The wash coat contains one or more platinum group metals (PGMs). Preferably, the PGMs make up the final coating of at least 1 gft -3 It is present in a total amount such that it contains [the specified substance]. The amount of PGM varies depending on the catalyst product formed and the end use. Nevertheless, the presence of PGM is important because otherwise there would be no constraints on the addition of surfactants as described herein. Preferably, the wash coat is such that the final coating is 1 gft, especially for CSF. -3 ~100gft -3 , comfortably 1gft -3 ~5gft -3 , and especially regarding GPF, 25gft -3 ~50gft -3 The wash coat contains PGM in such a total amount as PGM. PGM exists in the wash coat as ions, for example, nitrate ions. Suitable precursors of Pt and Pd include salts containing these metals, such as platinum nitrate and palladium nitrate.

[0028] The wash coat includes a support material. Support materials are well known in the art, and specific properties of the support material are not important depending on the application. Suitable support materials include silica, alumina, ceria, ceria-zirconia, etc. Preferably, the support material includes alumina. One or more support materials may be present. Supports such as alumina can be doped with a dopant. The dopant can 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 can be 1 to 30% by weight, preferably 2 to 25% by weight, and more preferably 3 to 20% by weight.

[0029] Washcoat contains a surfactant. The surfactant is a nonionic, silicon-free organic surfactant. The surfactant must be nonionic to minimize interaction with other components of the washcoat. Nonionic means that, unlike cationic or anionic surfactants, the surfactant does not contain an electric charge. Commercially available surfactants are clearly identifiable as either nonionic or nonionic.

[0030] The surfactant must be silicon-free, because the inventors have found that silane-containing surfactants react harmfully with the wash coat components, potentially affecting the PGM distribution and thus the catalytic activity.

[0031] The surfactant must be organic so that it can be completely removed by the calcination process. In other words, the surfactant that remains as a residue or contaminant in the calcination catalyst must not contain any inorganic components.

[0032] Preferably, the surfactant comprises one or more acetylenediol surfactants. Preferably, the one or more acetylenediol surfactants are one or more alkoxylate acetylenediol surfactants. More preferably, the one or more alkoxylate acetylenediol surfactants are one or more ethoxylated acetylenediol surfactants. More preferably, the one or more ethoxylated acetylenediol surfactants are one or more ethoxylated tetramethyldodecylenediol surfactants. Most preferably, the surfactant comprises one or more ethoxylated acetylenediol surfactants represented by the following formula:

[0033] [ka] In the formula, m and n are integers, and their sum is between 1 and 15, preferably between 4 and 12.

[0034] Suitable surfactants, as well as their structures and production methods, are discussed in U.S. Patent No. 5,650,543, which is incorporated herein by reference.

[0035] Of the classes of surfactants considered above, the preferred surfactant is Dynol-607™, a so-called superwetting surfactant. It satisfies the requirements outlined herein as preferred and overcomes the problems of the wash-coating process without impairing the properties of the hydrophobically treated substrate. The term “superwetting” indicates a surfactant that achieves low equilibrium surface tension (i.e., is effective in reducing surface tension) and low dynamic surface tension (i.e., acts quickly even with limited mixing and penetrates the wash-coat very quickly).

[0036] The inventors also considered other surfactants, such as Tego Twin 4200, which has silica functional groups that may interact within the wash coat, for example, during firing. Another nonionic surfactant is BYK-349, which also contains siloxane functional groups, and this changed the PGM wash coat to a different color, providing strong evidence that some kind of PGM-surfactant interaction was occurring.

[0037] Preferably, the surfactant is non-reducing with respect to Pt and / or Pd ions (and Rh ions, if present) in the wash coat. That is, preferably, the PGM is present in the wash coat as ions, and the surfactant cannot reduce those ions, particularly to form metals. Preferably, the surfactant has a reduction potential, as measured by cyclic voltammetry under standard conditions, which is insufficient to reduce the Pt and / or Pd ions present in the wash coat. Methods for measuring reduction potential using cyclic voltammetry are well known in the art, and reference values ​​are available for many materials. This ensures that there is no reaction between the surfactant and the PGM.

[0038] Preferably, the surfactant exhibits an equilibrium surface tension of less than 30 mN / m when measured using a force tensile meter with the Wilhelmie plate method (using a platinum plate). The platinum plate is used because of its low surface energy (giving a contact angle of 0° for most liquids). The force tensile meter lowers the platinum plate into the liquid and measures the force. The surface tension σ of the liquid can be calculated according to the formula σ = F / (L.cosθ), where F = force, L = wetting length of the platinum plate, and θ = contact angle of the liquid on the plate (known to be 0). A surface tension of less than 30 mN / m is compared to water, which is about 72.8 mN / m at 20°C. This is a measure of the surfactant's ability to improve the surface wetting ability of the wash coat.

[0039] Preferably, the surfactant exhibits a dynamic surface tension of less than 30 mN / m (measured by a bubble tension meter, e.g., Kruess BP100). Bubbles are formed through capillary action in the liquid under investigation, and the maximum internal pressure of these bubbles is measured. The dependence of surface tension on surface life can be measured by varying the rate at which bubbles are generated. A dynamic surface tension of less than 30 mN / m ensures that the surfactant moves quickly to the surface / newly formed interface of the wash coat, improving the rate at which coating can be performed and the consistency of the product.

[0040] The amount of surfactant varies depending on the specific surfactant used, but is preferably 0.01–0.5% by weight of the wash coat, preferably 0.05–0.35% by weight, and preferably 0.1–0.2% by weight. The amount of surfactant can be determined by testing, and it is desirable to use as little as possible to avoid PGM breakdown. At the same time, as the amount is added, there is generally a point at which further addition does not yield further benefit, which is typically immediately after the critical micelle concentration (CMC) of the surfactant is achieved. The critical micelle concentration is defined as the concentration at which the surface (or air-liquid interface) is completely saturated with surfactant molecules, resulting in the formation of a large number of micelles. This can be determined by increasing the surfactant concentration and performing a series of surface tension measurements (using the Wilhelmy method with a force tensile meter). Above the CMC, static surface tension is independent of surface tension. To ensure that the effect of the surfactant is consistent within and between coating applications, it is desirable that the amount of surfactant used exceeds this threshold, but it is equally desirable that it not exceed this point significantly, as this would entail the risk of PGM interactions.

[0041] Preferably, the wash coat consists of components (a) to (c) and water, and additives totaling less than 5% by weight, preferably less than 2% by weight. Preferably, the additives include one or more of rheology modifiers, ammonia, and pH adjusters. Rheology modifiers are discussed, for example, in U.S. Patent No. 9,144,796. Suitable examples of rheology modifiers include long-chain polysaccharides, polyethylene glycol derivatives (PEG), and polymers such as acrylic polymers. The wash coat slurry may also contain organic pore-forming agents. Examples of pore-forming agents include cellulose, polyethylene, starch, graphite, polypropylene, polyaramid, polytetrafluoroethylene, polystyrene, cellulose fibers, and polymethacrylates, such as Arbocel, Vivapur, Mipelon PM-200, Propyltex, Orgasol, and Remyrise.

[0042] The method includes step (iii) coating the filter body with a wash coat to form a coated filter body. Preferably, in step (iii), the wash coat is coated on and inside the outlet channels of the porous filter body, preferably only on the outlet channels. As discussed above, this has synergistic benefits if a prior hydrophobic treatment is applied to the inlet surface. Treatment of the inlet surface minimizes interaction between the filter body and exhaust gas (especially moisture), enhancing the filtration performance and lifespan of the component. On the other hand, coating the outlet channels with a wash coat provides catalytic performance, and for the addition of surfactants, this can still penetrate and adhere to the porous body.

[0043] The method includes (iv) firing the coated filter body to form a catalytic filter. This serves to dry and fire the inorganic washcoat components. Simultaneously, the surfactant and any other carbon-based components are oxidized and eliminated. A drying step at a lower temperature (e.g., 100-200°C) may be performed prior to firing. Firing is commonplace in the art and can be carried out under normal conditions.

[0044] Preferably, the catalytic filter is a gasoline particulate filter (GPF), the wash coat further comprises an oxygen storage compound (OSC), preferably ceria or ceria-zirconia OSC, and one or more PGMs contain Pd and Rh. When forming a GPF, preferably the wash coat has a solid content of 25-40% by weight.

[0045] Preferably, the catalytic filter is a catalytic soot filter (CSF), and one or more PGMs include Pt and optionally Pd. When forming a CSF, preferably the wash coat has a solid content of 1 to 10% by weight. Since CSFs typically have lower requirements for catalytic material than GPFs, the wash coat contains less solid.

[0046] Preferably, the method does not involve forming an emulsion in the wash coat before coating in step (iii). The purpose of the surfactant is to change the surface tension of the wash coat and improve its adhesion, rather than to stabilize the emulsion.

[0047] Preferably, the method does not involve foaming the wash coat before coating in step (iii). The purpose of the surfactant is to change the surface tension of the wash coat and improve its adhesion, rather than to stabilize the foam. The foaming step is absent because it would actively hinder the application of the wash coat to the pores of the porous body.

[0048] Preferably, the method does not include degassing the washcoat before the coating in step (iii). Degassing is a complex additional step that is not required in this method.

[0049] According to a further aspect, there is provided the use of a non-ionic, silicon-free organic surfactant to improve the washcoat adhesion of a PGM-containing washcoat to a porous filter body having a water contact angle of greater than 90° when measured by the washburn incorporation method. All aspects of the methods disclosed herein can also be applied to this use.

Examples

[0050] Here, the present invention will be further described with reference to the following exemplary examples.

[0051] Various catalytic filters were produced and tested. The porous wall flow filter body was a cylindrical part with dimensions of 143.8 mm in diameter × 152.4 mm in length. All catalytic washcoat coatings had a total washcoat loading of 0.1 g / in 3 and were particulate alumina and 2 g / ft 3 of only Pt, i.e.,不含Pd或(1:0)。The wall flow filter body coated with the catalytic washcoat is known as a "catalyzed soot filter" or "CSF". The EFC coating coated at a loading of 12 g / L is disclosed in the applicant's International Publication No. 2023 / 026022 (A1) and is derived from a 50:50 weight mixture of particulate aluminosilicate CHA zeolite and highly cross-linked ethoxylated poly(dimethylsiloxane) powder. The fired EFC coating is hydrophobic.

[0052]

Table 1

[0053] All firings were carried out in a static oven at 500 °C in air.

[0054] Next, a 1-inch (2.54 cm) diameter core cut from the coated filter body was subjected to a Laboratory Synthetic Catalytic Activity Test (SCAT). The following test conditions were used for "fresh" as-manufactured products, "adjusted" fresh products, and "aged" fresh products. • "Fresh": Unprepared light-off (LO) gradient test. Each core was stabilized for 10 minutes at an inlet gas temperature of 150°C in the light-off gas mixture test described below, and then the light-off temperature gradient itself was started at a gradient rate of 1°C per minute. The gas exiting the sample was analyzed to determine the conversion of the inlet components. • "Preparation": The preparation of fresh samples was performed in the SCAT instrument itself by first exposing the sample to 100% N2, then increasing the inlet gas temperature to 500°C at a rate of 30°C / min, and then switching the inlet gas to the gradient LO gas mixture composition described below at 500°C for 15 minutes. The "prepared" core was then stabilized at 150°C for 10 minutes in the gradient light-off gas mixture as described above for the "fresh" sample, and then the light-off temperature gradient itself was started. • Aging: Fresh samples were aged in a static oven in air at 500°C for 200 hours. The aged samples were then prepared and tested according to the same protocol as the prepared samples described above. • Light-off (LO) gas mixture: propene 10 ppm (C3), propane 10 ppm (C3), toluene 4.3 ppm (C3), n-decane 3 ppm (C3), CO 60 ppm, NO 500 ppm, H2O 5%, CO2 5%, O2 12%, remainder N2 · Space velocity=25000h -1

[0055] The NO oxidation activity of each sample is reported in Table 2, which clearly shows the difference in oxidation activity between the tested samples. The goal of this experiment is to achieve an oxidation activity of the CSF coated filter body containing EFC coating that is as close as possible to that of the reference CSF coated filter body sample without EFC coating.

[0056] The catalytic performance of hydrophobically treated components coated with 0.1% and 0.4% by weight Dynol-containing washcoats was substantially identical to that of the reference component (non-EFC hydrophobic treatment). The performance of all components was significantly better than that of the component (reference) in which the hydrophobic EFC treatment was applied over the catalyst washcoat component. The activity of samples in which a catalyst washcoat containing a PVP additive was applied over the hydrophobic EFC coating was found to be inconsistent with the activity of samples containing the Dynol additive. The NO oxidation activity of the PVP examples was slightly better than the comparative example without surfactants under fresh and "adjusted" conditions, and substantially the same as after aging, but did not reach the NO oxidation activity of the reference without the EFC hydrophobic coating.

[0057] [Table 2]

[0058] The findings from the study are summarized below. • A hydrophobic EFC coating over a CSF coating (reference) significantly affects oxidative activity, as exemplified by NO oxidation. A CSF wash coat (WC) (without surfactant additives) coated over an EFC coating (comparison) shows lower NO2 / NOx than the non-EFC coated reference. • Adverse effects on oxidation activity are also observed in the CO oxidation of reference samples with hydrophobic EFC coatings applied over CSF WC, compared to the non-EFC coated reference. Fresh CO oxidation of CSF WC applied over hydrophobic EFC coatings (comparative example without surfactant) is initially slightly worse than the non-EFC coated reference, but the CO oxidation activity improves to become identical for both samples as they are aged. • Adverse effects on oxidation activity are also observed in the HC oxidation of reference samples with hydrophobic EFC coatings applied over CSF WC, compared to non-EFC coated references. Fresh HC oxidation of CSF WC (comparative example without surfactant) applied over hydrophobic EFC coatings is initially slightly worse than that of the non-EFC coated reference, but the HC oxidation activity improves to become identical for both samples as they are aged. • Adding PVP to CSF ​​wash coat coatings resulted in a modified NO2 / NO2 ratio compared to a comparative example without surfactants. x While it slightly improves oxidation activity, it still shows a performance disparity compared to the reference non-EFC coated CSF sample. CO oxidation is improved by PVP addition, from fresh to aged samples. For HC oxidation activity, PVP addition does not show any particular benefit, whether fresh or aged. • Adding dynolic acid results in NO2 / NO2 x This improves the level to that of the reference non-EFC coated sample. However, 0.4 wt% Dynol slightly lowers the aged NO2 / NO2 ratio. x It exhibits oxidative activity, which likely suggests an excess of dynolic acid. • The addition of dynolic acid results in CO oxidation activity very similar to that of the non-EFC coated reference. Furthermore, the 0.4 wt% dynolic acid coating exhibits slightly lower CO oxidation activity than the 0.1 wt% dynolic acid sample. The addition of dynolic acid, whether at 0.1% by weight or 0.4% by weight, results in HC oxidation activity very similar to that of the non-EFC coated reference.

[0059] It should be understood that the Dynol addition test demonstrates that the catalytic oxidation performance of the component matches that of the non-EFC coated CSF reference component. This means that there is virtually no loss of oxidation activity, and the component according to the present invention benefits from the additional filtration improvements provided by the EFC coating, namely, improved lower back pressure and better filtration performance.

[0060] Filtration efficiency test The filtration efficiency test was performed using the apparatus and method described in European Patent No. 1850068, which is available for purchase from Cambustion® (Cambridge, UK) as the “DPG Particulate Filter Testing System” (see https: / / www.cambustion.com / products / engine-exhaust-emissions / dpg-particulate-filter-testing-system). That is, (i) an apparatus for generating and collecting particulate matter induced from the combustion of a liquid carbon-containing fuel, wherein the apparatus includes a fuel burner including a nozzle, the nozzle is housed in a container, the container includes a gas inlet and a gas outlet, the gas outlet is connected to a conduit for transporting gas from the gas outlet to the atmosphere, means for detecting the velocity of gas flowing through the gas inlet, means for forcing oxidizing gas from the gas inlet to the atmosphere through the container, gas outlet and conduit, a station for collecting particulate matter from the gas flowing through the conduit, and means for controlling the means for forcing the gas flow in response to the gas flow velocity detected at the gas inlet, thereby maintaining the gas flow velocity at the gas inlet at a desired rate to provide quasi-stoichiometric combustion of the fuel in the container, thereby promoting particulate matter formation, and (ii) A method for generating and collecting particulate matter induced from the combustion of a liquid carbon-containing fuel in an oxidizing gas, the method comprising: burning the fuel in a quasi-stoichiometric amount of oxidizing gas in a fuel burner, wherein the fuel burner includes a nozzle, the nozzle being housed in a container; forcing the oxidizing gas to flow from a gas inlet to a container, to the atmosphere, through a gas outlet into a conduit connected to the container and the gas inlet; collecting particulate matter at a station located in the conduit; detecting the velocity of the oxidizing gas flow at the gas inlet; and controlling the velocity of the oxidizing gas flow so that a desired velocity of the oxidizing gas flow is maintained at the gas inlet.

[0061] The filter is inserted into a station for collecting particulate matter from the gas flowing through the conduit. A fresh filter is first pre-conditioned in a lean-burn combustion stream with low-sulfur diesel fuel (10 ppm S) at an air velocity of 80 kg / hour, raising the filter inlet temperature to 650°C, a temperature typically used in vehicles, to regenerate the soot-filled filter. The temperature in this pre-conditioning step was kept well above the soot combustion temperature to ensure that the filter was clean from the start during testing. Pressure sensors positioned upstream and downstream of the station monitor the back pressure across the filter. The test was conducted with a filter inlet temperature of 250°C at an air velocity of 180 kg / hour while burning low-sulfur diesel fuel (10 ppm S).

[0062] The filtration efficiency test was performed using the DPG particulate filter test system as follows: At a constant flow rate, the initial test involved detecting the particulate number (PN) every second upstream of the filter using a PN counter. The upstream raw PN data was averaged over an 11-second detection period to create an 11-second averaging window that shifted every second, reducing the influence of any fluctuations in PN generation. Here, time "t" corresponds to the midpoint of the 11-second window. Next, the sample filter was tested by detecting the post-filter PN, also using a PN counter. The instantaneous filtration efficiency at time "t" in the test is given by the following calculation. FE t [%] = [Average upstream PN at time t - Average downstream PN at time t] / [Average upstream PN at time t] × 100%

[0063] The results of the filtration efficiency analysis are shown in Table 3.

[0064] [Table 3]

[0065] This test demonstrates that the combination of EFC (hydrophobic treatment) and the inclusion of a suitable surfactant results in an optimized component, which possesses both improved filtration performance resulting from the treatment (better with Dynol than with PVP) and improved catalytic oxidation performance consistent with the performance of a preceding reference product (i.e., CSF WC without hydrophobic EFC coating) (i.e., effective use of PGM).

[0066] All percentages in this specification are by weight unless otherwise specified.

[0067] The detailed description above is provided for illustrative and illustrative purposes only and is not intended to limit the scope of the appended claims. Many modifications of the currently preferred embodiments illustrated herein will be obvious to those skilled in the art and remain within the scope of the appended claims and their equivalents.

[0068] To avoid any ambiguity, the entire contents of all documents found herein are incorporated herein by reference.

Claims

1. A method for manufacturing a catalytic filter for an exhaust gas treatment system, i) To provide a porous filter body, ii) It is a wash coat, (a) One or more platinum group metals (PGMs) and (b) Support material and (c) To provide a wash coat comprising a surfactant, iii) Coating the filter body with the wash coat to form a coated filter body, iv) Including firing the coated filter body to form the catalyst filter, A method wherein the surfactant is a nonionic, silicon-free organic surfactant.

2. The method according to claim 1, wherein the porous filter body provided in step (i) has a water contact angle of more than 90° when measured by the washburn intake method.

3. The method according to claim 1 or 2, wherein the porous filter body is composed of silicon carbide, cordierite, or aluminum titanate, and the method further comprises applying a hydrophobic surface coating to the porous filter body before step (iii).

4. The method according to claim 3, wherein the hydrophobic surface coating is applied to the inlet channel of the porous filter body, preferably only to the inlet channel.

5. The method according to any one of claims 1 to 4, wherein the wash coat is coated in step (iii) on the inlet channel of the porous filter body, preferably on both the inlet channel and the outlet channel.

6. The method according to any one of claims 1 to 5, wherein the support material includes alumina.

7. The method according to any one of claims 1 to 6, wherein the catalyst filter is a gasoline particulate filter (GPF), the wash coat further comprises an oxygen storage compound (OSC), preferably ceria or ceria-zirconia OSC, and the one or more PGMs comprises Pd and Rh.

8. The method according to claim 7, wherein the wash coat has a solid content of 25 to 40% by weight.

9. The method according to any one of claims 1 to 8, wherein the catalytic filter is a catalytic soot filter (CSF), and the one or more PGMs include Pt and optionally Pd.

10. The method according to claim 9, wherein the wash coat has a solid content of 1 to 10% by weight.

11. The method according to any one of claims 1 to 10, wherein the wash coat comprises components (a) to (c) and water, and additives totaling less than 5% by weight, preferably additives totaling less than 2% by weight.

12. The method according to claim 11, wherein the additive comprises one or more of a rheological modifier, ammonia, and a pH adjuster.

13. The above method, before coating in step (iii), (i) Forming an emulsion in the wash coat, (ii) Foaming the wash coat, or (iii) The method according to any one of claims 1 to 12, wherein the method is not comprising deaerating the wash coat.

14. The aforementioned surfactant, (I) Pt ２＋ and Pd ２＋ It is non-reducing with respect to ions, and / or (II) Exhibiting an equilibrium surface tension of less than 30 mN / m, and / or (III) Exhibiting a dynamic surface tension of less than 30 mN / m, and / or (IV) The method according to any one of claims 1 to 13, comprising forming 0.01 to 0.5% by weight, preferably 0.05 to 0.2% by weight, of the wash coat.

15. The method according to any one of claims 1 to 14, wherein the surfactant comprises one or more acetylenediol surfactants, preferably one or more alkoxylate acetylenediol surfactants.

16. The PGM is at least 1 gft －３ The method according to any one of claims 1 to 15, wherein the PGM is present in a total amount sufficient to form a coating.

17. The use of a nonionic, silicon-free organic surfactant to improve the adhesion of a PGM-containing wash coat to a porous filter body having a water contact angle exceeding 90° when measured by the washburn intake method.

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