Coated filter

Abstract

The present disclosure relates to a powder-coated article for filtering particulate matter from exhaust gas. The powder-coated article includes a coated monolithic article and a powder coating on the coated monolithic article. The coated monolithic article is a monolithic article coated with an on-wall wash coat, and the powder coating includes inorganic particles and a silicone resin in a ratio of 50:1 to 1:9. The present disclosure also relates to a method of forming the powder-coated article.

Description

Technical Field

[0001] The present disclosure relates to a powder-coated article for filtering particulate matter from exhaust gas. The powder-coated article includes a coated monolithic article and a powder coating on the coated monolithic article. The coated monolithic article is a monolithic article coated with an on-wall wash coat, and the powder coating includes inorganic particles and a silicone resin in a ratio of 50:1 to 1:9. The present disclosure also relates to a method of forming the powder-coated article described herein.

Background Art

[0002] There are concerns regarding emissions of particulate matter (PM), commonly referred to as soot, from internal combustion engines, particularly diesel and gasoline engines for automotive applications. The main concerns are related to potential health effects, specifically those associated with very small particles having sizes in the nanometer range.

[0003] Diesel particulate filters (DPFs) and gasoline particulate filters (GPFs) have been manufactured using a variety of materials, including sintered metals, ceramics, or metal fibers. However, the most common type in actual mass production is of the wall-flow type made from porous ceramic materials fabricated in the form of a monolithic array of many small channels that extend along the length of the body. Since the alternating channels are blocked at one end, the exhaust gas is forced through the porous ceramic channel walls, which prevent most of the particulate matter from passing through, allowing only the filtered gas to enter the environment. Commercial production ceramic wall-flow filters include those made from cordierite, various forms of silicon carbide, and aluminum titanate. The actual shape and dimensions of a practical filter on a vehicle, as well as characteristics such as the thickness and porosity of the channel walls, depend on the application involved. The average size of the pores within the filter channel walls of a ceramic wall-flow filter through which the gas passes is typically in the range of 5 to 50 μm, usually about 20 μm. In marked contrast, most diesel particulate matter from modern passenger vehicle high-speed diesel engines is much smaller, for example, in the range of 10 to 200 nm.

[0004] Some PM can be retained within the pore structure of the filter wall, which in some applications can be gradually built up until the pores are bridged by a network of PM, which in turn will readily form a cake of particulate matter on the inner walls of the filter channels. The particulate cake is an excellent filter medium, and its presence results in very high filtration efficiency. In some applications, soot is continuously combusted on the filter as it is deposited, thereby preventing the particulate cake from accumulating on the filter.

[0005] In some filters, such as lightweight diesel particulate filters, it is periodically necessary to remove trapped PM from the filter to prevent an excessive increase in backpressure that can be harmful to engine performance and can also reduce fuel efficiency. In diesel applications, the retained PM is removed from the filter by burning it in air during a process, and during this process, the amount of available air and the amount of excess fuel used to achieve the high temperatures necessary to ignite the retained PM are very carefully controlled. Towards the end of this process, which is commonly referred to as regeneration, the removal of the last remaining particles within the filter can significantly reduce the filtration efficiency and can lead to a burst release of many small particles into the environment. Thus, the filters can have a low filtration efficiency when they are first used, after each subsequent regeneration event, and during the latter part of each regeneration process.

[0006] Accordingly, it is desirable to always improve and / or maintain the filtration efficiency, for example, during the initial life of the filter when it is first used, and / or during and immediately after regeneration, and / or when soot accumulates on the filter.

[0007] International Publication No. 2021 / 028692 (incorporated herein by reference in its entirety) discloses an exhaust filter for a vehicle, comprising a porous substrate having an inlet face and an outlet face, the porous substrate comprising an inlet channel extending from the inlet face and an outlet channel extending from the outlet face, the inlet channel and the outlet channel being separated by a plurality of filter walls having a porous structure, the exhaust filter for a vehicle having a density of 0.10 g / cm 3The exhaust filter for vehicles is filled with a refractory powder having a tap density before filling of less than, the mass filling amount of the refractory powder is less than 10 g / L, more than 40% of the refractory powder is arranged in the porous structure of a plurality of filter walls, and less than 60% of the refractory powder is coated on the outer surface of the plurality of filter walls. WO 2021 / 028692 also describes a suitable method and apparatus for spraying a dry refractory powder, such as a dry particle aerosol, onto the channels of a porous substrate, and preferably more than 50%, optionally up to 100% of the refractory powder can be arranged in the porous structure of a plurality of filter walls.

[0008] The inventors of the present application have developed the present invention to mitigate and / or overcome the problems found in the prior art. The present invention provides an improved method for the manufacture of a more efficient coated monolithic article, which advantageously exhibits higher water resistance and improved filtration efficiency.

SUMMARY OF THE INVENTION

[0009] The present invention relates to a powder-coated article comprising a coated monolithic article and a powder coating on the coated monolithic article. The coated monolithic article is a monolithic article coated with an on-wall wash coat, and the powder coating comprises inorganic particles and a silicone resin in a ratio of 50:1 to 1:9.

[0010] The present invention further relates to a method of forming the coated monolithic article and a fired powder-coated article.

[0011] The present invention also relates to a powder-coated article / fired powder-coated article for the treatment of exhaust gases and a vehicle exhaust system comprising the powder-coated article / fired powder-coated article.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0013] In one embodiment, the present invention is a powder-coated article, wherein the powder-coated article a) a coated monolithic article, and b) a powder coating on the coated monolithic article, and the coated monolithic article is a monolithic article coated with an on-wall wash coat, the powder coating relates to a powder-coated article containing inorganic particles and a silicone resin in a ratio of 50:1 to 1:9.

[0014] In a further embodiment, the present invention is a method of forming a powder-coated article as described herein, the method comprising i) providing a coated monolithic article, and ii) spraying inorganic particles and a silicone resin as dry particle aerosols onto the coated monolithic article to form a powder coating layer, the method of forming a powder-coated article, wherein the inorganic particles and the silicone resin are in a ratio of 50:1 to 1:9.

[0015] In a further embodiment, the present invention is a fired powder-coated article, wherein the powder-coated article a) A coated monolithic article, and b) A fired powder coating on the coated monolithic article, and The coated monolithic article is a monolithic article coated with an on-wall wash coat, The fired powder coating contains inorganic particles and silicon dioxide in a ratio of 65:1 to 1:7, and relates to a fired powder-coated article.

[0016] In a further embodiment, the present invention relates to a powder-coated article or a fired powder-coated article as described herein for the treatment of exhaust gases.

[0017] In a further embodiment, the present invention relates to a vehicle exhaust system comprising a powder-coated article or a fired powder-coated article as described herein.

[0018] Here, the present disclosure will be further described. In the following sections, different aspects / embodiments of the present disclosure are defined in more detail. Each aspect / embodiment so defined can be combined with any other aspect / embodiment or aspects / embodiments unless otherwise explicitly indicated. In particular, any feature indicated as being preferred or advantageous can be combined with any other feature or features indicated as being preferred or advantageous.

[0019] Coated monolithic article The monolithic article is a coated monolithic article. The coating includes one or more wash coats, preferably a catalyst wash coat. A wash coat is a composition that coats the porous structure of the article. Then, the article including one or more wash coats is preferably fired as described herein before spraying inorganic particles and a silicone resin onto the channels.

[0020] The catalyst washcoat may include a catalyst selected from the group consisting of a hydrocarbon trap, a three-way catalyst (TWC), a NOx absorbent, an oxidation catalyst, a selective catalytic reduction (SCR) catalyst, a lean NOx catalyst, and any combination of two or more thereof. Catalysts, such as TWC, NOx absorbent, oxidation catalyst, hydrocarbon trap, and lean NOx catalyst, may contain one or more platinum group metals, particularly those selected from the group consisting of platinum, palladium, and rhodium.

[0021] As a result, the coated monolithic article can be, for example, a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), a gasoline particulate filter (GPF), an ammonia slip catalyst filter (ASCF), or a combination of two or more thereof (for example, a filter including a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC)).

[0022] The coated monolithic article is coated with an on-wall washcoat. "On-wall" means that the washcoat exists as a coating on the wall of the monolithic article. The coating can be present on the wall of the monolithic article with a thickness of about 0.1 to 50% (for example, 0.1 to 30% or 0.5 to 15%) of the thickness of the wall on which the coating is disposed. A part of the on-wall coating can exist in-wall. "In-wall" means that the washcoat exists within the pores of the porous monolithic article.

[0023] The monolithic article can comprise a plurality of channels for the passage of exhaust gas, and each channel has a gas contact surface. Monolithic articles are well known in the art. A monolithic article may also be referred to as a substrate, preferably a honeycomb substrate, preferably a ceramic honeycomb substrate. Such a substrate includes a plurality of channels suitable for the passage of exhaust gas. The plurality of channels are parallel and extend from an inlet end (or first end) to an outlet end (or second end), that is, the channels extend axially through the article. Adjacent channels are alternately blocked at each end of the monolithic article, and during use, the exhaust gas passes along the inlet channels (i.e., the channels that are open at the inlet end of the monolithic article to receive the exhaust gas), passes through the channel walls, and enters the adjacent outlet channels (i.e., the channels that are open at the outlet end of the monolithic article). The monolithic article can comprise a plurality of inlet channels and a plurality of outlet channels. Typically, the channels have a square cross-section, but any known monolithic design can be employed.

[0024] In a preferred embodiment, 15 to 100%, preferably 16 to 99%, 17 to 95%, 18 to 90%, 19 to 80%, or 20 to 75% of the washcoat loading of the entire monolithic article is present on the walls. In an alternative embodiment, at least 15%, at least 16%, at least 17%, at least 17%, at least 18%, at least 19%, at least 20%, at least 21%, at least 22%, or at least 25% of the washcoat loading of the entire monolithic article is present on the walls. In a particularly preferred embodiment, at least 15% or at least 20% of the washcoat loading of the entire monolithic article is present on the walls.

[0025] In preferred embodiments, 50-100%, preferably 55-99%, 60-95%, 65-92%, 70-90%, or 80-90% of the washcoat loading in the inlet channels of the monolithic article is present on-wall. In alternative embodiments, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% of the washcoat loading in the inlet channels of the monolithic article is present on-wall. In particularly preferred embodiments, at least 80% or at least 90% of the washcoat loading in the inlet channels of the monolithic article is present on-wall.

[0026] In preferred embodiments, 5-100% of the part (e.g., article, inlet channel, and / or outlet channel) is coated with an on-wall washcoat. Preferably, 5-100%, 10-99%, 20-98%, 30-97%, 40-96%, 50-95%, 60-94%, 70-93%, 80-90% of the part is coated with an on-wall washcoat, e.g., at least 5%, at least 20%, at least 50%, at least 60%, at least 70%, at least 75%, or at least 80% of the part is coated with an on-wall washcoat.

[0027] As will be appreciated by those skilled in the art, the percentage of the coating present "on-wall" can be determined by techniques in the art such as scanning electron microscopy (SEM) or optical microscopy.

[0028] In some embodiments, the coated monolithic article has the following characteristics: 1) a d of 5-30 μm, e.g., 10-28 μm, 15-25 μm, preferably about 20 μm 90 , 2) 5 to 1500 cPs, for example 10 to 1400 cPs, 50 to 1300 cPs, 100 to 1200 cPs, 200 to 1100 cPs, 300 to 1000 cPs, 400 to 950 cPs, 500 to 900 cPs, 550 to 850 cPs, 600 to 800 cPs, 650 to 750 cPs, preferably a viscosity of about 700 cPs, 3) a pore former, for example a cellulose pore former, for example a pore former selected from Arbocel, Vivapur, Mipelon PM - 200, Propyltex, Orgasol, and Remyrise, is coated with an on - wall wash coat having one or more of the above.

[0029] It has been found that using one or more of the above - mentioned features can help promote the formation of the on - wall coating.

[0030] The viscosity can be measured at 20°C with a Brookfield RV DVII + Extra Pro viscometer using an SC4 - 27 spindle at a spindle speed of 50 rpm.

[0031] A washcoat that can be used to coat a monolithic article with an on-wall coating preferably includes a zeolite (e.g., a metal-supported zeolite), a binder, and a pore former. Examples of zeolites include small-pore zeolites, medium-pore zeolites, or large-pore zeolites, such as CHA, AEI, FAU, FER, and MFI. When a metal-loaded zeolite is used, the metal can be selected from one or more of transition metals, such as Cu, Ce, Fe, and Mn. Examples of binders are alumina binders such as boehmite, alpha alumina, beta alumina, and gamma alumina. Examples of pore formers include cellulose pore formers, polyethylene, starch, graphite, polypropylene, polyaramide, polytetrafluoroethylene, polystyrene, cellulose fibers, and polymethacryl methacrylate, such as Arbocel, Vivapur, Mipelon PM-200, Propyltex, Orgasol, and Remyrise. In some embodiments, the zeolite and the pore former are present in a ratio of 10:1 to 1:3, preferably 8:1 to 1:2, 6:1 to 1:1.5, 5:1 to 1:1, 4:1 to 1.5:1, 3:1 to 2:1, such as 5:1 to 1:2 or 3:1 to 1:1. In some embodiments, the zeolite and the binder (e.g., alumina binder) are present in a ratio of 20:1 to 1:1, such as 15:1 to 2:1, preferably 12:1 to 3:1, such as 10:1 to 5:1, more preferably about 9:1.

[0032] Preferably, the washcoat loading of the coated monolithic article is 0.1 g / in 3 ~10 g / in 3 、preferably, 0.1 g / in 3 ~8 g / in 3 、0.5 g / in 3 ~7 g / in 3 、0.8 g / in 3 ~6 g / in 3 、1 g / in 3 ~5 g / in 3 、1.25 g / in 3 ~4 g / in 3 、1.5 g / in3 ~3 g / in 3 、 2 g / in 3 ~2.5 g / in 3 It is. In a more preferred embodiment, the washcoat loading of the coated monolithic article is 0.5 g / in 3 ~5 g / in 3 or 1 g / in 3 ~2.5 g / in 3 It is.

[0033] The monolithic article / substrate may be formed from, for example, sintered metal, ceramic, or metal fibers. For example, the article may be formed from cordierite, various forms of silicon carbide, or aluminum titanate.

[0034] In some embodiments, the monolithic article is a monolithic filter. The monolithic filter is particularly preferably a wall flow filter (which may also be known as a wall flow monolithic article). Wall flow filters are well known and typically have adjacent channels alternately blocked at each end of the monolithic article, so that in use, the exhaust gas passes along the inlet channels (i.e., the channels open at the inlet end of the monolithic article to receive the exhaust gas) and is forced to pass through the channel walls and into the adjacent outlet channels (i.e., the channels open at the outlet end of the monolithic article).

[0035] The channel walls have a pore distribution that provides the required porosity to the monolithic article, and the average pore size in the channel walls, such as the filter walls, is typically in the range of 5 - 50 μm. Each channel has a gas contact surface. That is, each channel has a surface suitable for contacting, for example, exhaust gas in use. The surface may be provided by the channel wall surface and / or the pores contained therein.

[0036] In another particularly preferred embodiment, the monolithic article is a catalyst article (i.e., a catalyst article). Catalytic monolithic articles are well known and exhibit catalytic functions such as oxidation, NO x capture, or selective catalytic reduction activity.

[0037] In a particularly preferred embodiment, the monolithic article is a catalytic wall flow filter. As a result, the article can be, for example, a catalyzed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NO x trap filter (LNTF), a gasoline particulate filter (GPF), an ammonia slip catalyst filter (ASCF), or a combination of two or more thereof (e.g., a filter containing a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC)).

[0038] The shape and dimensions of the filter, such as properties like the channel wall thickness and its porosity, can vary depending on the intended use of the filter. The filter can be configured to be used with an internal combustion engine to filter the exhaust gas emitted by the internal combustion engine. The internal combustion engine can be a gasoline spark ignition engine. However, the filter finds particular applications when configured to be used with an internal combustion engine in the form of a diesel or gasoline engine.

[0039] Powder coating There is a powder coating on the coated monolithic article. The powder coating contains inorganic particles and a silicone resin in a weight ratio of 50:1 to 1:9. In a preferred embodiment, the weight ratio of the inorganic particles to the silicone resin is 40:1 to 1:8, 30:1 to 1:7, 20:1 to 1:6, 10:1 to 1:5, 9:1 to 1:4, 8:1 to 1:3, 7:1 to 1:2, 6:1 to 1:1, 5:1 to 2:1, or 4:1 to 3:1. In a more preferred embodiment, the weight ratio of the inorganic particles to the silicone resin is 10:1 to 1:3, preferably 5:1 to 1:2, more preferably 4:1 to 1:1, for example, about 3:1.

[0040] Without being bound by theory, the inventors have found that a specific ratio of inorganic particles to silicone resin can result in improved filtration efficiency and improved stability.

[0041] Preferably, the inorganic particles are selected from the group consisting of zeolites, refractory oxides, and mixtures thereof, preferably zeolites.

[0042] Zeolites have a structure formed from alumina and silica, and the SAR determines the reaction sites within the zeolite structure. Zeolites can be small-pore zeolites (e.g., zeolites having a maximum ring size of eight tetrahedral atoms), medium-pore zeolites (e.g., zeolites having a maximum ring size of ten tetrahedral atoms), or large-pore zeolites (e.g., zeolites having a maximum ring size of twelve tetrahedral atoms), or combinations of two or more of these.

[0043] Examples of suitable zeolites include silicate zeolites, aluminosilicate zeolites, metal-substituted aluminosilicate zeolites, AlPO, MeAlPO, SAPO, MeAPSO, and the like. In some embodiments, the zeolite is selected from aluminosilicates, borosilicates, gallosilicates, SAPO, AlPO, MeAPSO, and MeAPO zeolites.

[0044] When the zeolite is a small-pore zeolite, the small-pore zeolite can have a framework structure represented by a framework type code (FTC) selected from the group consisting of, for example, consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, LTA, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC, UEI, UFI, VNI, YUG, and ZON, or a mixture, combination, and / or intergrowth of two or more of these. In some embodiments, the small-pore zeolite has a framework structure selected from the group consisting of, for example, consisting of CHA, LEV, AEI, AFX, ERI, LTA, SFW, KFI, DDR, and ITE. In some embodiments, the small-pore zeolite has a framework structure selected from the group consisting of, for example, consisting of CHA and AEI. The small-pore zeolite can have a CHA framework structure.

[0045] When the zeolite is a mesoporous zeolite, the mesoporous zeolite can have a framework structure represented by a framework type code (FTC) selected from the group consisting of, for example, consisting of AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH, ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG, STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI, and WEN, or a mixture and / or intergrowth of two or more thereof. In some embodiments, the mesoporous zeolite has a framework structure selected from the group consisting of, for example, consisting of FER, MEL, MFI, and STT. In some embodiments, the mesoporous zeolite has a framework structure selected from the group consisting of, for example, consisting of FER and MFI, particularly MFI. When the mesoporous molecular sieve has a FER framework or an MFI framework, the zeolite can be ferrierite, silicalite, or ZSM-5.

[0046] When the zeolite is a large-pore zeolite, the large-pore zeolite can have a framework structure represented by a framework type code (FTC) selected from the group consisting of (e.g., consisting of) AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON, CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO, OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY, and VET, or a mixture of two or more thereof and / or intergrowths. In some embodiments, the large-pore zeolite has a framework structure selected from the group consisting of (e.g., consisting of) AFI, BEA, MAZ, MOR, and OFF. In some embodiments, the large-pore zeolite has a framework structure selected from the group consisting of (e.g., consisting of) BEA, MOR, and FAU. When the large-pore molecule has a framework structure of FTC, BEA, FAU, or MOR, the zeolite can be beta zeolite, faujasite, zeolite Y, zeolite X, or mordenite.

[0047] In some embodiments, the zeolite has a framework type selected from ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, SCO, CFI, SGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IFY, IHW, IRN, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MSO, MTF, MTN, MTT, MTW, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SFW, SGT, SOD, SOS, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, WI, VNI, VSV, WIE, WEN, YUG, ZON, or combinations thereof. In some embodiments, the zeolite has a framework type selected from AEI, AFT, AFV, AFX, AVL, BEA, CHA, DDR, EAB, EEI, ERI, FAU, FER, IFY, IRN, KFI, LEV, LTA, LTN, MER, MOR, MWF, MFI, NPT, PAU, RHO, RIE, RTH, SAS, SAT, SAV, SFW, TSC, and UFI.

[0048] In another embodiment, the inorganic particles can be refractory oxide particles based on oxides selected from the group consisting of alumina, silica, zirconia, ceria, chromia, magnesia, calcia, titania, and any two or more mixed oxides thereof. Preferably, the refractory oxide particles include calcium aluminate, fumed alumina, fumed silica, fumed titania, fumed zirconia, fumed ceria, alumina aerogel, silica aerogel, titania aerogel, zirconia aerogel, ceria aerogel, or mixtures thereof. One or more fumed refractory powders (refractory oxide particles) can be produced by an exothermic process, such as flame pyrolysis.

[0049] Preferably, the inorganic particles have a d (by volume) of 0.1 μm to 100 μm, preferably 0.2 μm to 50 μm, 0.5 to 40 μm, 1 μm to 30 μm, 2 μm to 20 μm, 5 μm to 15 μm, 6 μm to 10 μm. 90 In a preferred embodiment, the inorganic particles have a d (by volume) of 0.1 to 30 μm, 0.5 to 20 μm, or 1 μm to 10 μm. 90

[0050] Preferably, the inorganic particles have a crystallite size of 0.05 to 10 μm, preferably 0.1 to 8 μm, 0.5 to 6 μm, 0.75 to 5 μm, 1 to 4 μm, or 2 to 3 μm. In a particularly preferred embodiment, the inorganic particles have a crystallite size of 0.8 to 2.5 μm, such as 1 to 2 μm.

[0051] The particle size can be measured by standard methods such as scanning electron microscopy (SEM) and laser diffraction. When the particle size measurement value is obtained by laser diffraction particle size analysis, the particle size measurement value is obtained using the volume-based technique Malvern Mastersizer 3000 (i.e., D(v,0.1), D(v,0.5), D(v,0.9), and D(v,0.98) may also be referred to as DV10, DV50, DV90, and DV98 (or D10, D50, D90, and D98), respectively), and the mathematical Mie theory model is applied to determine the particle size distribution. ​

[0052] The silicone resin that can be used in the present invention is an oligosiloxane. Examples of the silicone resin that can be used in the present invention are as follows: polysilsesquioxane or polysiloxane, for example, polyalkylsilsesquioxane (such as polymethylsilsesquioxane), polyphenylsilsesquioxane, polyalkylsiloxane (such as polymethylsiloxane), and one or more of polyphenylsiloxane.

[0053] In this specification, the silicone resin may be referred to as silicone resin particles. Preferably, the melting point of the silicone resin is less than 150 °C, preferably less than 100 °C, less than 90 °C, less than 85 °C, or less than 80 °C. Without being bound by theory, the inventors believe that a silicone resin having such a melting point is particularly suitable for a powder coating process, that is, particularly suitable for effectively dispersing fine particles on a monolithic article together with inorganic particles, but is low enough to enable low-temperature firing, thereby effectively and efficiently adhering the inorganic particles to the gas contact surface of the channel wall.

[0054] Preferably, the silicone resin (i.e., silicone resin particles) has a d90 (by volume) of 0.1 μm to 100 μm, preferably 0.2 μm to 50 μm, 0.5 to 40 μm, 1 μm to 30 μm, 2 μm to 20 μm, 5 μm to 15 μm, 6 μm to 10 μm. In a preferred embodiment, the silicone resin (i.e., silicone resin particles) has a d90 (by volume) of 0.1 μm to 30 μm, 0.5 to 20 μm, or 1 to 10 μm.

[0055] Preferably, the mass filling amount of the powder coating (e.g., the total mass filling amount of the powder coating) is 0.1 g / L to 50 g / L, such as 0.5 g / L to 45 g / L, 1 g / L to 40 g / L, 2 g / L to 30 g / L, or 5 g / L to 25 g / L. Preferably, the mass filling amount of the inorganic particles is 0.05 g / L to 40 g / L, such as 0.1 g / L to 30 g / L, 1 g / L to 25 g / L, 5 g / L to 20 g / L, or 10 g / L to 15 g / L. Preferably, the mass filling amount of the silicone resin is 0.05 g / L to 30 g / L, such as 0.1 g / L to 25 g / L, 0.5 g / L to 20 g / L, 1 g / L to 15 g / L, or 5 g / L to 10 g / L. As an example, when the weight ratio of the inorganic particles to the silicone resin is 1:1, the filling amount of the inorganic particles may be 10 g / L, the filling amount of the silicone resin may be 10 g / L, and the total filling amount of the powder coating gives 20 g / L. As an example, when the ratio is 2:1, the inorganic particle filling amount may be 10 g / L, the silicone resin filling amount may be 5 g / L, giving a total filling amount of 15 g / L.

[0056] The powder coating is on the coated article. "On" can mean that the powder coating is immediately on the coated article, i.e., there is no intervening layer, or it can mean that the powder coating is on the coated article but one or more intervening layers are present. In a preferred embodiment, the powder coating is immediately on the coated article.

[0057] Method for forming a powder-coated article The method for forming a powder-coated article described herein includes spraying inorganic particles and a silicone resin as dry particulate aerosol onto a coated monolithic article to form a powder coating layer. The method can include spraying dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the gas contact surfaces of a plurality of channels on the coated monolithic article. Spraying of the dry powder onto the monolithic article is known in the art. Suitable methods and apparatuses are described, for example, in WO 2011 / 151711, WO 2021 / 028692, and WO 2021 / 028691.

[0058] In a preferred embodiment, the spraying step includes a first spraying step of spraying inorganic particles as a first dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto a coated monolithic article to form an inorganic particle layer, and then a second spraying step of spraying a silicone resin as a second dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the inorganic particle layer to form a coating layer. Thus, after the inorganic particles are sprayed onto the coated monolithic article, the silicone resin is sprayed separately onto the coated monolithic article further coated with the inorganic particles.

[0059] In a preferred embodiment, the spraying step includes a first spraying step of spraying a silicone resin as a first dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto a coated monolithic article to form a silicone resin layer, and then a second spraying step of spraying inorganic particles as a second dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the silicone resin layer to form a coating layer. Thus, after the silicone resin is sprayed onto the coated monolithic article, the inorganic particles are sprayed separately onto the coated monolithic article further coated with the silicone resin.

[0060] Even more preferably, the mixture of inorganic particles and silicone resin is sprayed as a dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the coated monolithic article in order to form a powder-coated article. Thus, a complete mixture of inorganic particles and silicone resin is coated onto the coated monolithic article, enhancing the adhesion of the inorganic particles to the coated monolithic article during the firing of the silicone resin.

[0061] In an alternative embodiment, the inorganic particles and the silicone resin are sprayed as a dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the coated monolithic article in order to form a powder-coated article. In this embodiment, the inorganic particles and the silicone resin are applied to the coated monolithic article separately but simultaneously.

[0062] The term "dry powder" or "dry particles" refers to a particulate composition that is not suspended or dissolved in a liquid. This does not necessarily mean that all water molecules are completely absent. The dry powder / dry particles preferably flow freely.

[0063] In a preferred embodiment, the spraying process is carried out under a constant gas flow rate, as described, for example, in WO 2021 / 028692. The gas can be selected from one or more of air, nitrogen, argon, helium, oxygen, carbon dioxide, etc. In a preferred embodiment, the gas is air. In a particularly preferred embodiment, the gas flow rate is 50 - 2000 m 3 / h, for example 80 - 1500 m 3 / h, 100 - 1,000 m 3 / h, 80 - 500 m 3 / h, for example 90 - 400 m 3 / h, 100 - 300 m 3 / h, 110 - 280 m 3 / h, 150 - 250 m 3 / hour, or 180 - 220 m 3 / hour. In a more preferred embodiment, the gas flow rate is 100 - 400 m 3 / hour, for example 150 - 350 m 3 / hour or 200 - 300 m 3 / hour.

[0064] The inventors have surprisingly found that by using a low air flow rate, the powder coating is deposited as a uniform layer along the channel, the accumulation at the end of the article becomes greater, and it is ensured that the gap between the end of the powder coating layer and the end of the article is filled.

[0065] The method can further include baking the coating layer to provide a baked powder-coated article. That is, the method includes baking a powder coating layer sprayed with inorganic particles and a silicone resin. By the baking process, the silicone resin is baked to become silicon dioxide in the powder coating. In some embodiments, by baking, about 100% of the silicone resin is baked to become silicon dioxide. In other embodiments, by baking, at least 95%, 90%, 80%, 75%, 60%, or 50% of the silicone resin is baked to become silicon dioxide.

[0066] The weight ratio of the inorganic particles to the silicon dioxide in the baked powder coating can be 65:1 - 1:7. In a preferred embodiment, the weight ratio of the inorganic particles to the silicon dioxide is 50:1 - 1:6, 38:1 - 1:6, 25:1 - 1:5, 13:1 - 1:4, 11:1 - 1:3, 10:1 - 1:2, 9:1 - 1:1.5, 8:1 - 1:0.8, 6:1 - 3:1, or 5:1 - 4:1. In a more preferred embodiment, the weight ratio of the inorganic particles to the silicon dioxide is 13:1 - 1:2, preferably 6:1 - 1:1.5, more preferably 5:1 - 1:0.8, for example about 2:1.

[0067] Preferably, the firing step includes heating to a temperature of at least 200°C, preferably at least 300°C, more preferably at least 400°C, and / or up to a temperature of 1,000°C maximum, 900°C maximum, 800°C maximum, 700°C maximum, 600°C maximum, preferably 550°C maximum, more preferably 530°C maximum. Accordingly, firing preferably includes heating to a temperature in the range of 200°C to 1,000°C, preferably 300°C to 900°C, preferably 400°C to 800°C, more preferably 400°C to 700°C, even more preferably 450°C to 550°C, for example, up to a temperature of about 500°C.

[0068] Such temperatures have been found to be most suitable for forming an effective binder that provides a fired powder-coated article with improved filtration efficiency and high water resistance. Such temperatures can bake the silicone resin to cross-linked silicon dioxide without adversely affecting the catalytic efficiency (i.e., without degrading the coated catalytic article), which is particularly advantageous when the coated monolithic article is a coated catalytic article such as a coated catalytic wall flow filter. Ideally, the firing temperature is kept as low as possible to reduce the potential to affect the catalytic activity of any catalyst present in the coated article.

[0069] The pore size of the fired powder coating layer is preferably in the range of 1 μm to 100 μm, preferably 1 μm to 50 μm, more preferably 1 μm to 20 μm, or 5 μm to 20 μm.

[0070] The pore size of the fired powder can be measured by techniques in the art, for example, by mercury intrusion porosimetry (MIP) using equipment from Micromeritics Autopore.

[0071] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly indicates otherwise. The use of the term "comprising" is intended to be construed as including such features but not excluding others, and is also intended to include alternatives of features that are necessarily limited to those described. In other words, this term is also intended to include, unless the context clearly indicates otherwise, "consisting essentially of" (which is intended to mean that certain further components may exist provided that they do not substantially affect the essential characteristics of the described features) and "consisting of" (which is intended to mean that when the components are expressed as percentages by their ratios, they total 100% while accounting for any inevitable impurities but not including other features).

[0072] As used herein, "d 90 (by volume)" refers to the d 90 (by volume) measurement obtained by a Malvern Mastersizer (registered trademark) 3000 with an Aero s dispersion unit available from Malvern Panalytical Ltd (Malvern, UK). Dispersion conditions: air pressure = 2 barg, feed rate = 65%, hopper gap = 1.2 mm. The refractive index and absorption rate parameters are set according to the instructions provided in the Malvern Mastersizer (registered trademark) 3000 user manual.

[0073] As used herein, the term "g / L" (grams per liter) refers to the mass of the powder divided by the volume of the filter.

[0074] The foregoing detailed description is provided for purposes of illustration and example and is not intended to limit the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Examples

[0075] Washcoat Preparation Washcoat A: A washcoat was prepared by suspending Cu-exchanged zeolite (CHA, SAR = 18.5, supplied by Tosoh, Cu loading = 3.3 wt%) and stabilized gamma alumina (supplied by PIDC) in water at a ratio of 9:1. The washcoat had a d of 4 - 6 μm 90 Before adding alumina, 4 wt% of TEAH of the zeolite is added.

[0076] Washcoat B: A washcoat was prepared by suspending Natrasol (a cellulose thickener), Cu-exchanged zeolite (CHA, SAR = 18.5, Cu loading = 3.3 wt%, supplied by Tosoh), Arbocel UFC100 (cellulose supplied by JRS), and boehmite (supplied by PIDC) in water at a ratio of 9:5:1 (zeolite:arbocel:boehmite). The washcoat had a d of 20 μm 90 It had.

[0077] Washcoat C: A washcoat containing Cu-exchanged zeolite (CHA, SAR = 18.5, supplied by Tosoh, Cu loading = 3.3 wt%) and stabilized gamma alumina (supplied by PIDC) suspended in water at a ratio of 9:1. The washcoat had a d of 4 - 5 μm 90 It had. The surface of the zeolite was modified using aminosilane (see US Patent No. 11192793 (B2)).

[0078] Method for preparing an in-wall coated filter, Filter A: Washcoat application according to European Patent No. 3122458. Washcoat C was applied to the outlet end of the filter (SC18 supplied by NGK), coating 80% of the filter volume, and 1.5 g.in per total filter volume -3was the fired filling amount. Washcoat A was applied to the inlet end of the filter, coating 30% of the filter volume, with a fired filling amount of 0.6 g.in -3 was the fired filling amount.

[0079] Method for preparing an on-wall coated filter, Filter B: Washcoat application according to European Patent No. 3122458. Washcoat A was applied to the outlet end of the filter (SC18 supplied by NGK), coating 80% of the filter volume, with a fired filling amount of 1.5 g.in -3 was the fired filling amount. Washcoat B was applied to the inlet end of the filter, coating 80% of the filter volume, with a fired filling amount of 0.6 g.in -3 was the fired filling amount.

[0080] General method for preparing a powder-coated article Zeo (chabazite zeolite having a SAR of 4 μm d 90 and 23, available from Tosoh) and a mixture with Silres MK powder (methyl silicone resin having a d of 9 μm 90 available from Wacker) were prepared in various different weight ratios. The resulting mixed powder was sprayed from the inlet end under a constant air flow rate of air onto the (on-wall) coated filter (Filter A) (using the spraying method of European Patent Application Publication No. 4013954 (A1)). The air flow rate was 100 - 200 m 3 / h. Subsequently, the coated portion was fired at 500 °C for 1 hour.

[0081] Example 1 - Ratio study Various different zeolite:silicone resin ratios were examined, and the results are shown in Table 1.

[0082] The inlet end was sprayed using compressed air, and then the outlet end was sprayed using compressed air. Subsequently, the mass loss was calculated.

[0083]

Table 1

[0084] Table 1 shows that the ratio of zeolite:silicone resin in the powder coating affects the cold flow back pressure and stability. The loss of mass indicates that the produced film layer is not stable.

[0085] Example 2 - Filtration Efficiency Study The filtration efficiency was tested under various conditions. The first condition was oven - cleaned in a cold - start WLTC test (high mass), the second condition was a hot - start WLTC test (high mass), and the third condition was a cold - start WLTC (regeneration) test (low mass). WLTC is a worldwide passenger vehicle test cycle, and the regeneration condition is a high temperature for decomposing the soot cake.

[0086] The results for a standard (in - wall) monolith article (Filter A), an (on - wall) coated monolith article (Filter B), and a powder - coated monolith article (3:1 Zeo:SilRes) are shown in Figure 1.

[0087] Figure 1 shows that the powder - coated monolith article according to the present invention exhibits improved filtration efficiency compared to the standard (in - wall) coated monolith and the (on - wall) coated monolith article under all test conditions.

[0088] Example 3 - Back Pressure The following samples were prepared. I 1:1 Zeo:SilRes 45 g II 1:1 Zeo:SilRes 60 g III 3:1 Zeo:SilRes 60 g IV 1:1 CuZeo2:SilRes 60 g​

[0089] When SilRes is the standard silicone resin MK material, Zeo2 is AEI zeolite, and the amount given in grams is the powder mass applied to the monolith.

[0090] Samples I - IV were completely submerged in a container of approximately 6 L of deionized water for about 10 seconds, then removed from the water, the parts were shaken to remove excess water, and dried in an oven at 115 °C under an air stream for about 45 minutes.

[0091] Samples I - IV were used to perform cold flow backpressure tests on a Superflow Flowbench SF - 1020 before and after water submersion treatment at a flow rate of 600 m 3 / h. The test results are shown in Table 2.

[0092]

Table 2

[0093] Table 2 shows that water submission caused only a slight change in the backpressure of Sample III.

[0094] Example 4 - Filtration Study The filtration efficiency was tested, and the results for a standard (in - wall) monolith article (Filter A), an (on - wall) coated monolith article (Filter B), an in - wall coated monolith article with a powder coating (Filter A + EFC), and a powder - coated monolith article (Filter B + EFC) are shown in Figure 2. EFC is an enhanced filter coating, i.e., the powder coating described herein.

[0095] Figure 2 shows that the powder-coated monolithic article according to the present invention exhibits improved filtration efficiency compared to a standard (in-wall) coated monolith, an (on-wall) coated monolithic article, and an in-wall coated monolith having a powder coating.

Claims

1. 1. A powder coated article, said powder coated article comprising: a) a coated monolith article; b) a powder coating on the coated monolith article; the coated monolith article is a monolith article coated with an on-wall washcoat; the powder coating comprises inorganic particles and a silicone resin in a weight ratio of 50:1 to 1:9; The on-wall washcoat d 90 between 5 μm and 30 μm; a viscosity of 5 cPs to 1500 cPs; and Pore-forming agents and A powder coated article wherein said inorganic particles are zeolites.

2. 10. The powder coated article of claim 1, wherein said inorganic particles are small pore zeolites.

3. 10. The powder coated article of claim 1, wherein said inorganic particles are CHA zeolite.

4. 10. The powder coated article of claim 1, wherein the coated monolith article is a coated monolith filter.

5. The powder coated article of claim 4, wherein the coated monolith filter is a coated wall-flow filter.

6. The powder coated article of claim 1, wherein the coated monolith article is a coated catalyst article.

7. The powder coated article of claim 6, wherein the coated catalytic article is a coated catalytic wall-flow filter.

8. 10. The powder coated article of claim 1, wherein the weight ratio of said inorganic particles to said silicone resin is from 10:1 to 1:

3.

9. The inorganic particles and / or the silicone resin particles have a d of 0.1 μm to 100 μm ９０ 10. The powder coated article of claim 1 having (by volume).

10. 10. The powder coated article of claim 1, wherein the powder coating has a mass loading of 0.1 g / L to 50 g / L.

11. 10. A method of forming a powder coated article according to claim 1, said method comprising: i) providing a coated monolith article; ii) spraying inorganic particles and a silicone resin as a dry particle aerosol onto the coated monolith article to form a powder coating layer; The inorganic particles and the silicone resin are in a weight ratio of 50:1 to 1:

9. A method for forming a powder coated article.

12. The method of claim 11 , wherein the atomization step is carried out under a constant gas flow rate.

13. The method of claim 12, wherein the gas flow rate is between 80 m 3 / hour and 300 m 3 / hour.

14. The method comprises: iii) firing the powder coating layer to provide a fired powder coated article. The method of claim 11 , further comprising the steps:

15. 15. The method of claim 14, wherein the calcining step comprises heating to a temperature of at least 200°C.

16. The method of claim 14, wherein the firing step includes heating to a temperature of up to 600°C.

17. 15. A fired powder coated article, optionally formed from the method of claim 14, said powder coated article comprising: a) a coated monolith article; b) a fired powder coating on the coated monolith article; the coated monolith article is a monolith article coated with an on-wall washcoat; the calcined powder coating comprises inorganic particles and silicon dioxide in a weight ratio of 65:1 to 1:7; The on-wall washcoat d 90 between 5 μm and 30 μm; a viscosity of 5 cPs to 1500 cPs; and Pore-forming agents and The inorganic particles are zeolite. Baked powder coated articles.

18. 18. The fired powder coated article of claim 17, wherein the weight ratio of inorganic particles to silicon dioxide is from 13:1 to 1:

2.

19. 18. The fired powder coated article of claim 17, wherein the pore size of the fired powder coating layer ranges from 1 μm to 100 μm.

20. 18. The powder coated article of claim 1 or the fired powder coated article of claim 17 for the treatment of exhaust gases.

21. 18. A vehicle exhaust system comprising the powder coated article of claim 1 or the baked powder coated article of claim 17.

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