Coating on monolithic articles

Abstract

The present disclosure relates to a coated monolith article for filtering particulate matter from exhaust gas. The monolith article has an inlet end and an outlet end, and includes a coating. The article includes an inorganic oxide applied to the inlet end of the article and a washcoat applied to the outlet end of the article. The present disclosure also relates to methods of forming the coated monolith articles as described herein and exhaust systems having the coated monolith articles as described herein.

Description

Technical Field

[0001] The present disclosure relates to a coated monolithic article for filtering particulate matter from an exhaust gas. The monolithic article has an inlet end and an outlet end and includes a coating. The article includes an inorganic oxide applied to the inlet end of the article and a washcoat applied to the outlet end of the article. The present disclosure also relates to a method of forming the coated monolithic article as described herein and an exhaust system having the coated monolithic article as described herein. Background Art

[0002] There are problems with the emission of particulate matter (PM) (commonly referred to as soot) from internal combustion engines, especially diesel and gasoline engines in automotive applications. The main problems are associated with potential health effects, especially with very small particles in the nanometer size range.

[0003] Diesel particulate filters (DPFs) and gasoline particulate filters (GPFs) have been made from a variety of materials, including sintered metals, ceramics, or metal fibers, etc. The most common type in actual large-scale production is the wall-flow type made of porous ceramic materials, which are manufactured in the form of a monolithic array of many small channels extending along the body length. Alternate channels are blocked at one end, so the exhaust gas is forced through the porous ceramic channel walls, which prevent most of the particulates from passing through, and thus only the filtered gas enters the environment. Ceramic wall-flow filters in commercial production include those made of cordierite, various forms of silicon carbide, and aluminum titanate. The actual shape and size of the practical filters on vehicles and characteristics such as the channel wall thickness and its porosity depend on the application of interest. The average size of the pores in the filter channel walls of the ceramic wall-flow filters through which the gas passes is typically in the range of 5 μm to 50 μm and is usually about 15 μm. In stark contrast, most of the diesel particulate matter from modern passenger car high-speed diesel engines is much, much smaller, for example, in the range of 10 nm to 200 nm.

[0004] Some PM may remain within the pore structure in the filter walls, and this can gradually accumulate in some applications until the pores are bridged by a network of PM, and this PM network then enables the easy formation of a particulate cake on the inner walls of the filter channels. The particulate cake is an excellent filtering medium, and its presence provides very high filtration efficiency. In some applications, the soot is continuously combusted on the filter upon deposition, which prevents the particulate cake from accumulating on the filter.

[0005] For some filters, such as light diesel particulate filters, it is necessary to periodically remove the captured PM from the filter to prevent the accumulation of excessive backpressure, which is harmful to engine performance and can lead to poor fuel economy. Thus, in diesel applications, the retained PM is removed from the filter by burning it in air during a process in which the amount of available air and the amount of excess fuel used to reach the high temperatures required to ignite the retained PM are very carefully controlled. Towards the end of this process, commonly referred to as regeneration, removing the last remaining particulates from the filter can result in a significant reduction in filtration efficiency and the sudden release of many small particles into the environment. Thus, the filter may have a low filtration efficiency when first used and subsequently after each regeneration event and also during the latter part of each regeneration process.

[0006] Accordingly, it is desirable to improve and / or maintain filtration efficiency at all times - for example during the early life of the filter when first used, and / or during and immediately after regeneration, and / or when the filter is loaded with soot.

[0007] WO2021 / 028691 describes a method of coating a filter that includes a porous substrate having an inlet surface and an outlet surface, where the inlet surface is separated from the outlet surface by a porous structure. The filter is coated with a dry powder that is applied through the inlet face of the filter.

[0008] WO2021 / 165658 describes an apparatus and method for coating a filter that includes a porous substrate having an inlet surface and an outlet surface. The filter is coated with a dry powder through the inlet face of the filter, and the dry powder includes a metal compound for forming a metal oxide by thermal decomposition.

[0009] WO2011 / 151711 describes a method of preparing a filter that includes a porous substrate having an inlet surface and an outlet surface, where the inlet surface is separated from the outlet surface by a porous structure containing pores having a first average pore size. The inlet surface includes a bridging network that includes interconnected refractory particles over the pores of the porous structure. The method includes the step of contacting the inlet surface of the filter substrate with an aerosol including a refractory material in dry powder form. SUMMARY OF THE INVENTION

[0010] In a first aspect, the present disclosure provides a coated monolithic article for filtering particulate matter from an exhaust gas.

[0011] The monolithic article includes an inlet end and an outlet end, and a coating that includes:

[0012] a) an inorganic oxide coating applied to the inlet end of the article, and

[0013] b) A carrier coating applied to the outlet end of the article.

[0014] In another aspect, there is provided a method of forming a monolithic article (e.g., a monolithic article as described herein), the method comprising:

[0015] i) providing a monolithic article having an inlet end and an outlet end,

[0016] ii) applying an inorganic oxide coating to the inlet end,

[0017] iii) optionally drying and / or calcining the inorganic coating,

[0018] iv) applying a carrier coating to the outlet end,

[0019] v) optionally drying / calcining the resulting article.

[0020] In another aspect, there is provided an exhaust gas system comprising a coated monolithic article (e.g., a coated monolithic article as described herein or prepared by a method as described herein), and optionally an internal combustion engine.

[0021] In another aspect, there is provided a method for treating exhaust gas, the method comprising contacting the exhaust gas with a coated monolithic article (e.g., a coated monolithic article as described herein or prepared by a method as described herein).

[0022] At the time of the present invention, it was considered impossible to apply an inorganic coating as a first step and then use a carrier coating because the inorganic coating would be unstable during the subsequent application of the carrier coating. Even when the inorganic coating was adjusted to be stable during the application of the carrier coating, it was found that applying the inorganic coating as a first step provided less control over the final back pressure and also less control over the position of the carrier coating. The inventors have surprisingly found that by adjusting the composition of the inorganic coating, the final back pressure and the position of the carrier coating can be controlled, and the inorganic coating is stable for the subsequent application of the carrier coating.

[0023] A coated monolithic article as described herein (or prepared by a method as described herein) has improved properties over coated monolithic articles of the prior art. For example, a coated monolithic article according to the present invention has improved filtration efficiency without experiencing an increase in back pressure typically associated with improved filtration efficiency. The coated monolithic article of the present invention has a low back pressure and a high filtration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 There is shown a coated monolithic article according to the present invention.

[0025] Figure 2 There is shown the filtration efficiency for Comparative Examples 1 and 2 and Sample 3.

[0026] Figure 3 Shows the mass loading and cold flow back pressure for Comparative Examples 1 and 2 and Sample 3.

[0027] Figure 4 Shows the filtration efficiency for Comparative Examples 1 and 2 and Sample 3. Detailed Description

[0028] In a first aspect, the present disclosure provides a coated monolithic article for filtering particulate matter from an exhaust gas.

[0029] The monolithic article includes an inlet end and an outlet end, and a coating, the coating comprising:

[0030] a) an inorganic oxide coating applied to the inlet end of the article, and

[0031] b) a support coating applied to the outlet end of the article.

[0032] Monolithic article

[0033] The monolithic article as described herein may include a plurality of channels for the passage of exhaust gas, each channel having a gas contact surface. Monolithic articles are well known in the art.

[0034] Monolithic articles are sometimes referred to as substrates, preferably honeycomb substrates, more preferably ceramic honeycomb substrates. Such substrates include a plurality of channels adapted for the passage of exhaust gas. The channels are parallel and extend from an inlet end (or first end) to an outlet end (or second end), i.e., the channels extend axially through the article. Typically, the channels have a square cross-section, but any known monolithic design may be used.

[0035] The monolithic article / substrate may be formed of, for example, sintered metal, ceramic, or metal fibers. For example, the article may be formed of cordierite, various forms of silicon carbide, or aluminum titanate.

[0036] In some embodiments, the monolithic article is a monolithic filter. Particularly preferably, the monolithic filter is a wall-flow filter (also referred to as a wall-flow monolithic article). Wall-flow filters are well known and typically, adjacent channels are alternately blocked at each end of the monolithic article such that in use, exhaust gas passes along inlet channels (i.e., channels that are open at the inlet end of the monolithic article for receiving exhaust gas) and is forced through the channel walls into adjacent outlet channels (i.e., channels that are open at the outlet end of the monolithic article).

[0037] The channel walls may have a pore distribution that provides the desired porosity for the monolithic article. The average size of the pores in the channel walls (e.g., the filter walls) is typically in the range of 5 μm to 50 μm. Each channel may have a gas contact surface. That is, each channel may have a surface adapted to contact, for example, exhaust gas during use. This surface may be provided by the channel wall surface and / or the pores contained therein.

[0038] In another particularly preferred embodiment, the monolithic article is a catalyst article (i.e., a catalytic filter). Catalytic porous monolithic articles are well known and exhibit catalytic functions such as oxidation, NO x trapping or selective catalytic reduction activity. The catalyst article may also be selected from, for example, a three-way catalyst (TWC), NO x adsorbent, oxidation catalyst, selective reduction catalyst (SCR), hydrocarbon trap, and lean NO x catalyst.

[0039] In another particularly preferred embodiment, the monolithic article is a catalytic wall-flow filter. Thus, the article may be, for example, a catalytic 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 including a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC)).

[0040] In another particularly preferred embodiment, the monolithic article is a gasoline particulate filter, which is a catalytic wall-flow filter containing a TWC catalyst. Generally speaking, a gasoline particulate filter contains: platinum group metals selected from the group consisting of Pt, Pd, Rh, and mixtures thereof; an oxygen storage capacity (OSC) material; and optionally an inorganic carrier material.

[0041] The shape and size of the filter (e.g., characteristics such as the channel wall thickness and its porosity) may vary according to the intended application of the filter. The filter may 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 may be a gasoline spark-ignition engine. However, when configured to be used with an internal combustion engine in the form of a diesel or gasoline engine, the filter has a specific application.

[0042] The wall-flow filter can be an asymmetric wall-flow filter. Asymmetric wall-flow filter designs are known, for example, from WO2005 / 030365, which discloses a honeycomb filter comprising an array of interconnected porous walls that define an array of first and second channels. The first channels are bounded on their sides by the second channels and have a larger hydraulic diameter than the second channels. The first channels have a square cross-section, where the corners of the first channels have a shape such that the thickness of the porous walls adjacent to the corners of the first channels is comparable to the thickness of the porous walls adjacent to the edges of the first and second channels. In use, the first channels with the larger hydraulic diameter are oriented to the upstream side. Society of Automotive Engineers (SAE) Technical Paper Series 2007-01-0656 explains that "due to the contraction and expansion of the gas at the filter channel inlet and outlet, there is a pressure drop loss in the clean state for the ACT design [for catalytic asymmetric channel technology (ACT) wall-flow filters]. However, when operating on a vehicle, the filter is in a completely clean (fully regenerated) state for a very short time." WO2005 / 030365 also explains that the advantages of the asymmetric filter design include an increased effective surface area available for collecting soot and ash particles in the inlet portion of the honeycomb filter, thereby increasing the total storage capacity of the honeycomb filter. The general knowledge textbook "Catalytic Air Pollution Control—Commercial Technology", 3rd Edition, Ronald M. Heck et al., John Wiley & Sons, Hoboken, New Jersey, USA (2009), pages 338-340, explains that "such [asymmetric filter] channel designs achieve a combination of higher ash storage capacity and lower ash loading backpressure due to the larger hydraulic diameter and higher open volume at the inlet. The ACT design also helps to maintain the mechanical and thermal durability of the filter.

[0043] Inorganic oxide coating

[0044] The inorganic oxide coating as described herein can comprise inorganic particles comprising a silicoaluminate zeolite and an organosilicon resin.

[0045] The inorganic particles can comprise aluminosilicate zeolites having a SAR (SAR) greater than 10:1, greater than 20:1, greater than 50:1, greater than 75:1, or greater than 100:1. The aluminosilicate zeolites preferably have a SAR greater than 200:1, more preferably greater than 300:1, even more preferably greater than 400:1, and most preferably greater than 500:1. In some embodiments, the aluminosilicate zeolites have a SAR greater than 1000:1.

[0046] The aluminosilicate zeolite may have a framework type selected from the following: 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 a combination thereof. In some embodiments, the aluminosilicate zeolite may have a framework type selected from the following: 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. In some embodiments, the aluminosilicate zeolite may have a framework type selected from the group consisting of (or consisting of) the following: AEI, BEA, CHA, FAU (e.g., zeolite Y), and MFI. In some embodiments, the aluminosilicate zeolite has a BEA framework type.In some embodiments, the aluminosilicate zeolite has an MFI framework type. In some embodiments, the aluminosilicate has an FAU framework type. In some embodiments, the zeolite is zeolite Y.

[0047] In addition to the aluminosilicate zeolite, the inorganic particles can include a second zeolite material. Examples of suitable second zeolite materials include silicate zeolites, aluminosilicate zeolites, metal-substituted aluminosilicate zeolites, AlPO, MeAlPO, SAPO, MeAPSO, etc. The second zeolite material can have a framework type selected from the following: 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 a combination thereof.

[0048] The inorganic particles may include refractory oxide particles, which may be based on oxides selected from the group consisting of (or consisting of) the following: alumina, silica, zirconia, ceria, chromia, magnesia, calcia, titania, and mixed oxides of any two or more thereof. Preferably, the refractory oxide particles include calcium aluminate, pyrogenic alumina, pyrogenic silica, pyrogenic titania, pyrogenic zirconia, pyrogenic ceria, alumina aerogel, silica aerogel, titania aerogel, zirconia aerogel, ceria aerogel, or mixtures thereof. The one or more refractory powders (refractory oxide particles) may be produced by a pyrometallurgical process, such as flame pyrolysis.

[0049] The amount of aluminosilicate zeolite present in the inorganic particles may be from 10 wt% to 99 wt%, preferably from 50 wt% to 99 wt%, more preferably from 80 wt% to 99 wt%, and most preferably from 90 wt% to 99 wt%. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite. In some embodiments, the inorganic particles consist of an aluminosilicate zeolite having a SAR greater than 100:1. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite having a SAR greater than 200:1. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite having a SAR greater than 300:1. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite having a SAR greater than 400:1. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite having a SAR greater than 500:1. In some embodiments, the inorganic particles comprise (or consist of) an aluminosilicate zeolite having a SAR greater than 1000:1.

[0050] Silicone resins are known and are branched cage-like oligosiloxanes and polysiloxanes. The branching in silicone resins is due to the presence of so-called "T" and / or "Q" units in the resin, which refer to RSiO3 and SiO4 units (R is an alkyl or aryl group), respectively, where additional silicon units are bonded to oxygen atoms. The "M" unit (i.e., R3SiO unit) is a terminal unit where the oxygen atom provides the connection to the resin backbone. Similarly, the "D" unit (i.e., R2SiO2 unit) provides a linear connection spanning two oxygen atoms. A well-known non-branched and linear polysiloxane is polydimethylsiloxane (PDMS; i.e., (Me2SiO) n )

[0051] Preferably, the silicone resin is a solid at room temperature (e.g., about 25 °C). Thus, the silicone resin preferably has a melting point greater than 25 °C, preferably greater than 30 °C, more preferably greater than 35 °C. Preferably, the melting point of the silicone resin is less than 100 °C, preferably less than 95 °C, less than 90 °C, less than 85 °C or less than 80 °C. Unbranched polysiloxanes such as PDMS generally have a lower melting point than branched silicone resins. For example, the melting point of PDMS is about -40 °C. WO 2011 / 151711 discloses binding powders in place by treatment with polydimethylsiloxane, which forms silica when hydrolyzed at a sufficiently high temperature.

[0052] Similarly, the inventors have found that it can be preferable for the silicone resin to have a glass transition temperature (Tg) greater than 30 °C, preferably greater than 35 °C, and / or less than 100 °C, preferably less than 80 °C. Without wishing to be bound by theory, the inventors believe that silicone resins having such a melting point and / or glass transition temperature are particularly suitable for powder coating processes, i.e., for effectively dispersing fine particles together with inorganic particles on a monolithic article, but the melting point and / or glass transition temperature is low enough to allow low temperature calcination, thereby effectively and efficiently adhering the inorganic particles to the gas contact surface of the channel wall.

[0053] Preferably, the silicone resin has a molecular weight greater than 1,000, preferably greater than 2,000, preferably greater than 5,000, preferably greater than 10,000, and / or less than 500,000, preferably less than 200,000.

[0054] As used herein, the molecular weight refers to the weight average molecular weight (M W w), which can be measured using any conventional device in the art. In some embodiments, particularly those described herein in which the silicone resin contains hydroxyl functional groups, the molecular weight may be relatively low because the hydrogen bonds provided by the hydroxyl functional groups provide a sufficiently high melting point and / or glass transition temperature for the silicone resin. Thus, in some embodiments, the molecular weight of the silicone resin can be from 1,000 to 10,000, preferably from 1,000 to 5,000, preferably from 1,200 to 3,500, such as from 1,500 to 2,000. Silicone resins having a molecular weight below 1,000 are less preferred because these silicone resins are generally liquids and are not suitable for dry spraying, or do not have as many branches as larger molecules, and branching is thought to enhance the binding of inorganic particles to the monolithic article.

[0055] However, the molecular weight of the silicone resin can preferably be from 15,000 to 150,000, preferably from 20,000 to 120,000, preferably from 60,000 to 100,000. Some preferred resins have an Mw of from 8,000 to 15,000, some resins are from 20,000 to 60,000, and other resins are from 80,000 to 120,000.

[0056] Particularly preferably, the silicone resin has the formula [R x SiX y O z n , where R is an alkyl or aryl group, X is a functional group bonded to silicon, and where z is greater than 1 and less than 2. As will be understood, n is large in order to provide the oligomers or polymers required for silicone resins, particularly those that are solids at room temperature. Although depending on the molecular weight of the R and X groups, when n is greater than 10, an M W greater than 1,000 can be obtained, when n is greater than 100, an M W greater than 10,000 can be obtained, and when n is greater than 1,000, an M W greater than 100,000 can be obtained. Thus, n can preferably be greater than 10, greater than 100, greater than 1,000.

[0057] As will be understood, R is an alkyl or aryl group bonded to silicon, while X is a non-hydrocarbon functional group bonded to silicon. Similarly, since silicon is a tetravalent atom, it should be understood that x + y + 2z = 4. z is less than 2 because where z = 2, x and y = 0, providing silicon dioxide (i.e., silica; (SiO2) n ). Similarly, z is greater than 1 because where z = 1, x + y = 2, giving a substituted polysiloxane composed of "D" units (e.g., (RXSiO) n ), giving a linear resin (e.g., –O–(SiRX)–O–(SiRX)–O–). An example is polydimethylsiloxane. Thus, O refers to the oxygen that bridges two silicon atoms in the polymer backbone of the silicone resin.

[0058] Preferably, 0 < x + y < 2, preferably 0 < x + y ≤ 1.5, preferably 0 < x + y ≤ 1. Preferably, x, y, and / or x + y are greater than 0.1, preferably greater than 0.2. In a preferred embodiment, x + y is 1, giving a silicone resin commonly referred to as a polyhedral oligomeric silsesquioxane. Preferably, y is less than 1 and / or y is less than x. Even more preferably, 2y ≤ x, preferably 5y ≤ x, preferably 10y ≤ x. In one embodiment, y is 0. For example, y is 0 where the polyhedral oligomeric silsesquioxane is a polyalkylsilsesquioxane, such as polymethylsilsesquioxane (MeSiO 3 / 2 ) n .​

[0059] Typically, when present, X is one or more of H, hydroxy (OH), Cl, and C1–C6 alkoxy groups, preferably one or more of OH and C1–C6 alkoxy groups, preferably where the C1–C6 alkoxy group is selected from methoxy (OCH3) and ethoxy (OCH2CH3). In a particularly preferred embodiment, X is one or both of OH and ethoxy. However, X is a functional group and can also be a reactive functional group such as an amino group (NH2, NR2), epoxy group, acrylate group, and vinyl group, but these functional groups are less preferred because the presence of a hydroxy or alkoxy group is considered to provide more effective crosslinking during calcination. As described above, any oxygen present in the terminal functional group does not contribute to the "O" in the above formula, and this "O" refers to the silicon of the bridging oxygen atom. z " z " refers to the silicon of the bridging oxygen atom.

[0060] The inventors have found that the silicone resins described herein provide beneficial coated monolithic articles having enhanced water resistance and improved thermal stability. The silicone resins have been found to be particularly advantageous in binding inorganic particles to the monolithic article. Without wishing to be bound by theory, the inventors believe that the branched structure and physical properties of the silicone resin allow the resin to first melt during the calcination step as described herein and begin to cure after binding (either tightly binding or depositing thereon) to the inorganic particles on the gas contact surface of the channels. As the resin cures, the resin forms additional –Si–O–Si–O–Si– bridges / bonds, further increasing its branched structure. Additionally, the inventors believe that this binding can also form, for example, through the formation of –Si–O–Al– bonds, together with the gas contact surface (i.e., the monolithic article itself) and the inorganic particles, further binding the particles in place in the article. As the temperature continues to increase during calcination, the R and X groups are oxidized, leaving behind a silica (SiO2) backbone. Thus, silicon- and / or aluminum-containing inorganic particles may be preferred, such as zeolites, calcium aluminate, alumina, and / or silica.

[0061] Preferably, the silicone resin has a degree of crosslinking greater than 55%, preferably greater than 60%, more preferably greater than 65%, and / or less than 85%, preferably less than 80%.

[0062] As described herein, in view of the tetravalent nature of silicon, such as the formula [R x SiX y O z [ nThe silicon atoms of the described silicone resins can be in one of four coordination environments, namely, SiO(R / X)3, SiO2(R / X)2, SiO3(R / X), or SiO4, which are referred to in the art as "M", "D", "T", and "Q", respectively. Thus, the above formula can be described by aMbDcTdQ, where a + b + c + d = 1, and the degree of crosslinking is defined by [(a + 2b + 3c + 4d) / 4]*100. The relative ratio of the number of silicon atoms in each coordination environment can be determined using standard spectroscopic techniques (such as multinuclear NMR spectroscopy, especially 29 Si NMR spectroscopy). Alternatively, for commercially available silicone resins, the degree of crosslinking can be provided in the technical data sheet.

[0063] In other words, silica (SiO2) is formed entirely of "Q" SiO4 units, where each silicon atom is bonded to four connected oxygen atoms. Thus, in the case where d is 1, this gives silica a 100% degree of crosslinking. On the other hand, by way of example, PDMS is formed entirely of "D" Si(Me)2O2. Thus, in the case where b is 1, this gives polydimethylsiloxane a 50% degree of crosslinking. Thus, the silicone resin preferably has a degree of crosslinking between these two extremes and includes a mixture of such units. Thus, the silicone resin may preferably comprise MDT units, MTQ units, DTQ units, or DT units (or consist of them).

[0064] Preferably, R is one or more of C1-C6 alkyl or phenyl. Due to the oligomeric or polymeric nature of the silicone resin, the number of monomer units is typically large. There may be many cases of the two groups R and X such that a silicone resin described by a single monomer unit can contain multiple different groups. As described above for the functional group X, X can preferably be both OH and ethoxy. Similarly, R can include more than one C1-C6 alkyl and / or phenyl. Thus, when R is described by more than one group (such as R' and R”), the formula of the silicone resin can be [R' x’ R” x” SiX y O z n , where x'+x” = x. This also applies to the functional group X.

[0065] Preferably, R is one or more of straight-chain or branched-chain alkyl and phenyl, straight-chain alkyl and phenyl, more preferably one or more of methyl and phenyl. In some preferred embodiments, where R is both methyl and phenyl, the ratio of phenyl to methyl is less than 2, preferably less than 1.5, preferably less than 1, preferably less than 0.5. In some embodiments, R is phenyl. More preferably, R is methyl (i.e., the ratio is 0). ​

[0066] For the R and X groups, smaller organic groups such as methyl, methoxy, and ethoxy groups are particularly preferred because this increases the SiO2 content of the starting silicone resin, thereby reducing the weight loss during calcination. Additionally, the smoke and loss of volatiles such as H2O, CO2, and other volatile organic compounds during calcination are reduced.

[0067] Accordingly, it is preferred that the silicone resin has a silica content greater than 50 wt%, preferably greater than 60 wt%, preferably greater than 70 wt%, preferably greater than 80 wt%. The silica content may also be referred to as the ash content, which is the weight of the product remaining after complete oxidation (in this case, the product is silica), based on the weight of the starting silicone resin. For example, the oxidation may be carried out at about 1000 °C. Alternatively, the silica content may be obtained from the technical data sheet of a suitable commercially available silicone resin. Alternatively, the silica content may be calculated based on the complete oxidation of silicon to silica and the resin chemical formula. By way of example only, based on the weight of a silicone resin with a formula weight of 66.1 and a silicon atomic weight of 28.1, polymethylsilsesquioxane (MeSiO 3 / 2 ) n is about 42.7 wt% silicon. Silica has a formula weight of 60.1, which is about 2.1 times the formula weight of silicon. Thus, the silica content of polymethylsilsesquioxane is 2.1 * 42.7 = 89.7 wt% (i.e., based on the weight of the silicone resin).

[0068] A particularly preferred silicone resin for use in the method of the present invention is a highly crosslinked ethoxylated poly(dimethylsiloxane) having a silica content of about 82 wt% and a melting point of 35 °C to 55 °C.

[0069] Preferably, the inorganic particles and / or silicone resin particles have a d 50 .

[0070] Preferably, the total inorganic oxide coating can be applied to the monolithic article at a mass loading of less than 50 g / L, preferably less than 30 g / L. In a preferred embodiment, the total mass loading of the inorganic oxide coating is from 1 g / L to 25 g / L, such as from 2 g / L to 20 g / L, or preferably from 3 g / L to 15 g / L. Preferably, the mass loading of the inorganic particles is at least 1 g / L and / or less than 25 g / L. Preferably, the mass loading of the silicone resin is at least 1 g / L and / or less than 25 g / L. In a preferred embodiment, the mass loading of the inorganic particles is from 1 g / L to 15 g / L and / or the mass loading of the silicone resin is from 1 g / L to 15 g / L. By way of example, in the case where the weight ratio of inorganic particles to silicone resin is 1:1, the loading of the inorganic particles can be 5 g / L and the loading of the silicone resin can be 5 g / L, such that the total loading of the inorganic oxide coating is 10 g / L. By way of example, in the case where the ratio is 2:1, the inorganic particle loading can be 10 g / L while the silicone resin loading is 5 g / L, such that the total loading is 15 g / L.

[0071] In some embodiments, the ratio of inorganic particles to silicone resin in the inorganic oxide coating is from 0.5:1 to 5:1, preferably from 1:1 to 4:1, such as about 2:1 or 3:1.

[0072] Support coating

[0073] The washcoat as described herein can comprise an oxygen storage capacity (OSC) material, an inorganic oxide support, a noble metal, and / or a rheology modifier.

[0074] "Oxygen storage capacity" refers to the ability of a material used as an oxygen storage capacity material in a catalyst to store oxygen under lean conditions and release it under rich conditions.

[0075] Examples of OSC materials that can be used in the washcoat include Al2O3, SiO2, TiO2, CeO2, ZrO2, V2O5, La2O3, Nd2O3, Pr6O 11 , HfO2, and zeolites (e.g., zeolites as described herein). In a preferred embodiment, the OSC material present in the washcoat comprises one or more mixed oxides, such as a mixed oxide of cerium and zirconium, a mixed oxide of cerium, zirconium, and aluminum, a mixed oxide of cerium, zirconium, and neodymium, a mixed oxide of cerium, zirconium, and praseodymium, or a mixed oxide of cerium, zirconium, lanthanum, and neodymium. As used herein, the term "mixed oxide" generally refers to a mixture of oxides in a single-phase form, as is commonly known in the art. In a further preferred embodiment, the washcoat comprises one or more OSC materials selected from a mixed oxide of cerium and zirconium, a mixed oxide of cerium, zirconium, and neodymium, a mixed oxide of cerium, zirconium, lanthanum, and neodymium, or a mixed oxide of cerium, zirconium, lanthanum, hafnium, and neodymium.

[0076] The amount of the OSC material in the carrier coating can be 5 wt% to 50 wt%, preferably 10 wt% to 30 wt%, relative to the total weight of the carrier coating.

[0077] Examples of the inorganic oxide carrier can be oxides of Group 2, 3, 4, 5, 13, and 14 elements. The inorganic oxide carrier is preferably a refractory oxide that exhibits chemical and physical stability at high temperatures such as those associated with gasoline engine exhaust. The inorganic oxide carrier can be selected from alumina, silica, titania, and their mixed oxides or composite oxides. More preferably, the inorganic oxide carrier is alumina. In one embodiment, the inorganic oxide carrier is γ-alumina. The γ-alumina used as the inorganic oxide carrier preferably has an average particle size of 1 μm to 10 μm, more preferably 2 μm to 8 μm. In another embodiment, the inorganic oxide carrier is nano-alumina. The nano-alumina used as the inorganic oxide carrier preferably has an average particle size of less than 1 μm.

[0078] The inorganic oxide carrier can be doped with dopants. The dopants can be selected from La, Sr, Si, Ba, Y, Pr, Nd, Ce, and their mixtures. Preferably, the dopants are La, Ba, Nd, or Ce. Most preferably, the dopants are La or Nd. The dopant content in the inorganic oxide carrier can be 1 wt% to 30 wt%, preferably 2 wt% to 25 wt%, more preferably 3 wt% to 20 wt%.

[0079] The amount of the inorganic oxide carrier in the carrier coating can be 2 wt% to 30 wt%, preferably 5 wt% to 20 wt%, relative to the total weight of the carrier coating.

[0080] Examples of the noble metals that can be used in the carrier coating include platinum group metals (such as Ru, Rh, Pt, Os, Ir, and Pd), Ag, Au, In, Re, Ge, Be, Ga, Te, Bi, and Hg. In a preferred embodiment, the noble metals that can be used in the carrier coating are selected from the group consisting of Pt, Pd, and Rh.

[0081] The amount of the total noble metals in the carrier coating can be 0.005 wt% to 10 wt%, preferably 0.001 wt% to 5 wt%, more preferably 0.05 wt% to 3.0 wt%, relative to the total weight of the carrier coating.

[0082] Examples of rheology modifiers that can be used in the carrier coating include silanes, amines, acids, polysaccharides (such as starch, cellulose, galactomannan gum, xanthan gum, curdlan, etc.), dispersible cellulose (e.g., Natrosol), TEAOH (tetraethylammonium hydroxide), Dispex, amino acids, β-alanine, and ammonia. In a preferred embodiment, the rheology modifier for the carrier coating is selected from polysaccharides and amino acids, such as Natrosol and β-alanine.

[0083] The carrier coating may also contain C2-C6 aliphatic amino acids. Suitable C2-C6 aliphatic amino acids include 3-amino-propionic acid, L-alanine, glycine, serine, L-valine, etc. Preferably, the C2-C6 aliphatic amino acid is a C2-C6 aliphatic amino acid having the formula HO2C-(CH2) n -NH2 amino acids, wherein n is 1 to 5, preferably 1 to 3. A preferred amino acid is 3-amino-propionic acid (n=2).

[0084] The amount of C2-C6 aliphatic amino acid in the carrier coating may be 1 to 50 wt %, preferably 2 to 40 wt %, more preferably 3 to 30 wt % or 5 to 25 wt % relative to the solid mass in the carrier coating.

[0085] The carrier coating may also contain additional components such as metal hydroxides, metal phosphates, metal carbonates or mixtures thereof. The metal hydroxide may be selected from magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide. The metal phosphate may be selected from magnesium phosphate, calcium phosphate, strontium phosphate and barium phosphate. The metal carbonate may be selected from magnesium carbonate, calcium carbonate, strontium carbonate and barium carbonate. In a preferred embodiment, the carrier coating comprises barium hydroxide.

[0086] In a preferred embodiment, the washcoat comprises ceria zirconia, alumina, a noble metal selected from Pd, Pt or Rh, barium hydroxide, a rheology modifier and a C2-C6 aliphatic amino acid (e.g., 3-aminopropionic acid). The washcoat may optionally further comprise lanthanum oxide and / or neodymium oxide.

[0087] Preferably, the total washcoat loading is 35 g / L to 150 g / L, preferably 40 g / L to 125 g / L, for example 50 g / L to 100 g / L, 60 g / L to 90 g / L or 65 g / L to 85 g / L. In alternative embodiments, the total washcoat loading is about 70 g / L, about 75 g / L or about 80 g / L.

[0088] The washcoat may have a pH between 4 and 7, such as between 4.5 and 6.5, preferably between 5 and 6.

[0089] The carrier coating may have a conductivity of 1 mS to 100 mS, for example 2 mS to 50 mS, 3 mS to 30 mS, 5 mS to 25 mS or 10 mS to 20 mS. In a preferred embodiment, the conductivity is 1 mS to 30 mS, for example 5 mS to 25 mS, 8 mS to 22 mS, 10 mS to 20 mS, or 12 mS to 18 mS.

[0090] Conductivity can be measured using a Cole Parmer conductivity meter at 20°C.

[0091] The viscosity of the carrier coating may be between 0 cPs and 5,000 cPs, such as 1 cPs to 3,000 cPs, 2 cPs to 2,000 cPs, 3 cPs to 1,000 cPs, 4 cPs to 500 cPs or 5 cPs to 300 cPs. In a preferred embodiment, the viscosity is between 5 cPs and 250 cPs, between 10 cPs and 200 cPs, between 15 cPs and 180 cPs, between 25 cPs and 150 cPs, between 50 cPs and 120 cPs or between 60 cPs and 100 cPs. In a more preferred embodiment, the viscosity of the carrier coating is between 5 cPs and 200 cPs, even more preferably between 25 cPs and 120 cPs, such as between 50 cPs and 100 cPs.

[0092] Viscosity can be measured at 20°C on a Brookfield RV DVII+ Extra Pro viscometer using a SC4-27 spindle at a spindle speed of 50 rpm.

[0093] Total washcoat d 90 (by volume) may be between 0.1 μm and 100 μm, preferably between 0.2 μm and 50 μm, between 0.5 μm and 40 μm, between 1 μm and 30 μm, between 1.5 μm and 20 μm, between 2 μm and 10 μm, between 3 μm and 8 μm. In a preferred embodiment, the d of the total carrier coating is 90 (by volume) between 0.1 μm and 10 μm, between 0.5 μm and 9 μm, between 1 μm and 8 μm, between 1.5 μm and 7.5 μm, between 2 μm and 7 μm, between 2.5 μm and 6 μm, between 3 μm and 5.9 μm. In a more preferred embodiment, the d 90 (by volume) between 4 μm and 5.8 μm, for example about 5.5 μm.

[0094] As used herein, the term “ 90"(by volume)" refers to the Malvern Panalytical with Aero s dispersion unit available from Malvern Panalytical Ltd., Malvern, UK. 3000 measured d 90 (by volume) Measurement results. Dispersion conditions: air pressure = 2 bar, feed rate = 65%, hopper gap = 1.2 mm. According to Malvern Set the refractive index and absorption parameters following the instructions provided in the 3000 User Manual.

[0095] Coated monolithic article

[0096] The monolithic article includes different coating layers, the coating layers being different from each other.The monolithic article may include two or more layers (eg, two or more different layers).

[0097] In one embodiment, the monolithic article comprises two coatings, an inorganic coating (e.g., an inorganic coating as described herein) and a washcoat (e.g., a washcoat as described herein). In a preferred embodiment, the inorganic coating (e.g., an inorganic coating as described herein) is applied directly to the monolithic article on the inlet end thereof (i.e., there is no intervening layer between the monolithic article and the inorganic oxide coating). In a preferred embodiment, the washcoat (e.g., a washcoat as described herein) is applied directly to the monolithic article on the outlet end thereof (i.e., there is no intervening layer between the monolithic article and the washcoat).

[0098] Figure 1 An embodiment of the present invention is shown. The article is made of a plurality of channels and has an inlet end (1) and an outlet end (2). The inlet end has an applied inorganic oxide coating (3), and the outlet end has an applied support coating (4). The inorganic oxide coating and the support coating are Figure 1 As depicted in the drawings as covering 100% of the length of the article, however, as will be appreciated by those skilled in the art, the inorganic coating may be applied such that it extends from 80% to 100% of the length of the article from the inlet end (preferably from 90% to 100% or about 100% of the length of the article from the inlet end). In additional or alternative embodiments, the washcoat may be applied such that it extends from 60% to 100% of the length of the article from the outlet end (preferably from 65% to 95%, e.g., from 70% to 90% or from 75% to 80% of the length of the article from the outlet end).

[0099] In an alternative embodiment, an inorganic coating (e.g., an inorganic coating as described herein) is directly applied to the monolithic article (i.e., there is no intermediate layer between the monolithic article and the inorganic oxide coating), and a support coating (e.g., a support coating as described herein) is directly applied to the inorganic coating (i.e., there is no intermediate layer between the inorganic coating and the support coating).

[0100] Inlet end

[0101] The inlet end of the monolithic article (e.g., the inlet end as described herein) comprises an inorganic oxide coating (e.g., consisting of an inorganic oxide coating).

[0102] In a preferred embodiment, the inorganic oxide coating of the inlet end is directly applied to the monolithic article (i.e., there is no intermediate layer between the monolithic article and the inorganic oxide coating).

[0103] Outlet end

[0104] The outlet end of the monolithic article (e.g., the outlet end as described herein) comprises a support coating (e.g., consisting of a support coating).

[0105] In a preferred embodiment, the support coating of the outlet end is directly applied to the monolithic article (i.e., there is no intermediate layer between the monolithic article and the support coating).

[0106] Method for forming a coated monolithic article

[0107] The present invention also relates to a method of forming a coated monolithic article (e.g., a coated monolithic article as described herein), the method comprising:

[0108] i) providing a monolithic article having an inlet end and an outlet end,

[0109] ii) applying an inorganic oxide coating to the inlet end,

[0110] iii) optionally drying and / or calcining the inorganic coating,

[0111] iv) applying a support coating to the outlet end,

[0112] v) optionally drying and / or calcining the resulting article.

[0113] An inorganic oxide coating (e.g., the inorganic oxide coating of step ii)) is applied to the monolithic article. In a preferred embodiment, the inorganic oxide coating is applied in a spraying step. In a particularly preferred embodiment, the inorganic coating is applied only from the inlet end in the spraying step.

[0114] In one embodiment, an inorganic oxide coating is applied in a spraying step, which spraying step includes a first spraying step in which inorganic particles are sprayed as a first dry particulate aerosol to form an inorganic particle layer, and then a silicone resin is sprayed as a second dry particulate aerosol onto the inorganic particle layer in a second spraying step. Thus, the inorganic particles are sprayed and then the silicone resin is separately sprayed onto the article coated with the inorganic particles. In a particularly preferred embodiment, only the inorganic particles and the silicone resin are applied from the inlet end in the spraying step.

[0115] Even more preferably, a mixture of the inorganic particles and the silicone resin is sprayed as a dry particulate aerosol to form the inorganic oxide coating. Thus, a tight mixture of the inorganic particles and the silicone resin is applied, and the adhesion of the inorganic particles to the monolithic article is enhanced when the silicone resin is calcined. In a particularly preferred embodiment, the mixture of the inorganic particles and the silicone resin is sprayed as a dry particulate aerosol only from the inlet end.

[0116] In the case where a mixture of the inorganic particles and the silicone resin is sprayed as a dry particulate aerosol to form the inorganic oxide coating (preferably, where the dry particulate composition consists of the inorganic particles and the silicone resin), in the mixture, the weight ratio of the inorganic particles to the silicone resin is preferably greater than 0.5 (in other words, greater than 0.5:1), preferably greater than 0.7, preferably greater than 0.9, and / or less than 10, preferably less than 8, preferably less than 5. For example, the ratio may preferably be about 2 or about 3. Preferably, the ratio is from 1 to 4, preferably from 2 to 4.5, preferably from 2.5 to 4, preferably from 2.5 to 3.5, for example about 3.

[0117] The method may further include calcining the inorganic oxide coating before applying the carrier coating. That is, the method includes calcining the monolithic article having the inorganic particles and the silicone resin sprayed on the porous monolithic article on the gas contact surfaces of the plurality of channels. Preferably, the calcining step includes heating to a temperature of at least 200 °C, preferably at least 300 °C, more preferably at least 400 °C, and / or at most 600 °C, preferably at most 550 °C, more preferably at most 530 °C. Thus, the calcining preferably includes heating to a temperature of 200 °C to 600 °C, preferably 300 °C to 550 °C, preferably 400 °C to 530 °C, more preferably 400 °C to 500 °C, even more preferably 400 °C to 450 °C.

[0118] In a preferred embodiment, the inorganic oxide coating is dried but not calcined before applying the carrier coating. The inventors have surprisingly found that it is not necessary to calcine the inorganic oxide coating before applying the carrier coating. This can reduce the energy required to produce the product of the present invention. Thus, in a preferred embodiment, the inorganic oxide coating is not calcined before applying the carrier coating.

[0119] An inorganic oxide coating can be applied such that it extends from the inlet end 80% to 100% of the length of the substrate. In a preferred embodiment, the inorganic oxide coating extends from the inlet end 90% to 99% of the length of the substrate, more preferably 95% to 98%, such as about 100%, about 95% or about 90%.

[0120] A carrier coating (e.g., the carrier coating as described herein, particularly the carrier coating of step iv)) is applied to the monolithic article at the outlet end of the monolithic article. The carrier coating can be applied to the outlet end of the monolithic article in a single dose or multiple doses (e.g., 2 doses, 3 doses, 4 doses or 5 doses). In a preferred embodiment, the carrier coating is applied to the monolithic article in a single dose or two doses, most preferably in a single dose. When a multiple-dose carrier coating is applied to the monolithic article, the same or different carrier coatings can be applied each time, preferably the same carrier coating is applied to the monolithic article.

[0121] A carrier coating (e.g., the carrier coating of step iv)) can be applied such that the carrier coating extends from the outlet end 60% to 100% of the length of the article. In a preferred embodiment, the carrier coating extends from the outlet end 65% to 95% of the length of the substrate, more preferably 70% to 90%, 75% to 80%, such as about 80%, about 75% or about 70%.

[0122] The carrier coating (e.g., the carrier coating of step iv)) can be applied using any conventional method, such as the Automatic Inversion Depositor (AID) method or the Precision Coating (PC) method. The AID process involves using a piston to push the carrier coating into the filter, flipping the part, and then the carrier coating infiltrates into the walls of the substrate. The PC method involves using a spray head to apply the correct dose, sucking the carrier coating into the part by gravity and / or vacuum, and immersing the carrier coating into the substrate walls. In a preferred embodiment, the PC process is used to apply the carrier coating to the substrate. The carrier coating can be applied by metering the carrier coating through the outlet end and:

[0123] i) applying a vacuum to the carrier coating, and / or

[0124] i) applying a positive pressure to the carrier coating, and / or

[0125] iii) metering the carrier coating by capillary action,

[0126] to allow it to coat at least a portion of the channels with the carrier coating.

[0127] Preferably, the calcination step includes heating to a temperature of at least 200 °C, preferably at least 300 °C, more preferably at least 400 °C, and / or at most 600 °C, preferably at most 550 °C, more preferably at most 530 °C. Thus, the calcination preferably includes heating to a temperature of 200 °C to 600 °C, preferably 300 °C to 550 °C, preferably 400 °C to 530 °C, more preferably 400 °C to 500 °C, and even more preferably 400 °C to 450 °C.

[0128] Such temperatures have been found to be most suitable for forming an effective binder that provides favorable water resistance to the coated monolithic article. Such temperatures are particularly advantageous when the monolithic article is a catalyst article, such as a catalytic wall flow filter, as these temperatures allow the silicone resin to be calcined into cross-linked silica without negatively affecting the catalytic efficiency (i.e., without degrading the catalyst article). It is believed that linear siloxanes such as PDMS not only do not provide the required branching to effectively bind inorganic particles and adhere to the article, but also require temperatures in excess of 550 °C or even 600 °C to fully degrade into SiO2. Ideally, the calcination temperature is kept as low as possible to reduce the likelihood of affecting the catalytic activity of any catalyst present in the monolithic article.

[0129] Exhaust system and method

[0130] According to a further aspect, there is provided an exhaust gas system that includes a coated monolithic article as described herein or prepared by a method as described herein, and optionally an internal combustion engine. The internal combustion engine can be a diesel engine, a lean burn gasoline engine, or an engine powered by liquefied petroleum gas or natural gas. Preferably, the internal combustion engine is a diesel engine. The coated monolithic article can be disposed downstream of the engine to treat the exhaust gas discharged from the engine.

[0131] According to yet another aspect of the present invention, there is provided a method for treating exhaust gas that includes contacting the exhaust gas with a coated monolithic article as described herein or prepared by a method as described herein.

[0132] Although the preferred embodiments of the present invention have been described in detail herein, those skilled in the art should understand that various changes can be made to the present invention without departing from the scope of the present invention or the appended claims.

[0133] The present invention will now be further described in connection with the following non-limiting examples and the accompanying drawings.

[0134] As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" include plural referents. 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 feature options that must be limited to those described. In other words, the term also includes the limitations "consisting essentially of" (which is intended to mean that certain additional components may be present, provided that they do not substantially affect the basic characteristics of the described features) and "consisting of" (which is intended to mean that no other features may be included, such that if these components are expressed as percentages of their proportions, these will total 100%, taking into account any unavoidable impurities), unless the context clearly indicates otherwise.

[0135] As used herein, the term "g / L" (grams per liter) refers to the mass of the powder divided by the volume of the filter.

[0136] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments shown herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

[0137] Examples

[0138] Example 1

[0139] Preparation of Comparative Example 1

[0140] Provide a monolithic article having an inlet end and an outlet end. Meter in 100% of the carrier coating via a depositor from the outlet end, dry the article in a dynamic drying oven at 115 °C, and then calcine at 500 °C. Apply an inorganic oxide coating to the inlet and calcine the resulting coated article at 500 °C.

[0141] Preparation of Comparative Example 2

[0142] Provide a monolithic article having an inlet end and an outlet end. Meter in 50% of the carrier coating via a depositor from the outlet end, dry the article in a dynamic drying oven at 115 °C, and then meter in an additional 50% of the carrier coating from the outlet end via a depositor. Then dry the article in a dynamic drying oven at 115 °C and then calcine at 500 °C. Apply an inorganic oxide coating to the inlet and calcine the resulting coated article at 500 °C.

[0143] Preparation of Sample 3 according to the present invention

[0144] Provide a monolithic article having an inlet end and an outlet end. Apply an inorganic oxide coating to the inlet, and dry the article in a dynamic drying oven at 115 °C. Meter in 50% of the carrier coating via a depositor from the outlet end, dry the article in a dynamic drying oven at 115 °C, and then meter in an additional 50% of the carrier coating via the depositor from the outlet end. Then dry the article in a dynamic drying oven at 115 °C and calcine it at 500 °C.

[0145] Example 2

[0146] Calculate the filtration efficiency for Comparative Examples 1 and 2 and Sample 3. On a DPG (Diesel Particulate Generator), measure the soot before and after the filter, and calculate the filtration efficiency using the following equation:

[0147] Filtration efficiency = 1 - (soot after filter / soot before filter)

[0148] The results are shown in Figure 2 .

[0149] Figure 2 Show that, compared with Comparative Examples 1 and 2, the results for Sample 3 according to the present invention have substantially the same filtration efficiency, indicating that the present invention shows comparable filtration efficiency and can be used as a viable alternative to Comparative Examples 1 and 2.

[0150] Example 3

[0151] Calculate the mass loading and cold flow back pressure for Comparative Examples 1 and 2 and Sample 3. Measure the mass loading before and after loading on a balance. Measure the cold flow back pressure by passing 600 m 3 / h of air flow and measuring its pressure drop (in millibars). The results are shown in Figure 3 .

[0152] Figure 3 Show that, compared with Comparative Examples 1 and 2, Sample 3 according to the present invention has substantially the same cold flow back pressure, indicating that the present invention shows comparable cold flow back pressure and can be used as a viable alternative to Comparative Examples 1 and 2. In addition, compared with Comparative Examples 1 and 2, substantially the same inorganic coating can be loaded onto Sample 3, resulting in a similar catalyst mass loading for a similar cold flow back pressure.

[0153] Example 4

[0154] Evaluate the filtration efficiency of the fresh sample on an engine via a VW RDE Max drive cycle evaluation. Test the sample after a reference flow-through catalyst. Calculate the filtration efficiency using the following equation.

[0155]

[0156] The results are shown in Figure 4 for particulate matter greater than 10 nm (left) and greater than 23 nm (right).

[0157] Figure 4 Show that, compared with Comparative Examples 1 and 2, the samples according to the present invention have substantially filtration efficiency, indicating that the present invention shows considerable filtration efficiency and can be used as a viable alternative to Comparative Examples 1 and 2.

Claims

1. A monolithic article, comprising an inlet end and an outlet end, and a coating, wherein the coating comprises: a) an inorganic oxide coating applied to said inlet end of said article, and b) a washcoat applied to the outlet end of the article.

2. The monolithic article according to claim 1, wherein the monolithic article is a monolithic filter, preferably a wall flow filter, and / or a catalyst article, preferably a catalytic wall flow filter.

3. The monolithic article according to any preceding claim, wherein the inorganic oxide coating comprises inorganic particles (e.g., inorganic particles comprising aluminosilicate zeolites) and a silicone resin, Preferably wherein the inorganic particles comprise an aluminosilicate zeolite selected from the group comprising AEI, BEA, CHA, FAU (e.g. zeolite Y) and MFI, and / or Wherein the total inorganic oxide coating is present at a mass loading of 1 g / L to 25 g / L, such as 2 g / L to 20 g / L, preferably 3 g / L to 15 g / L.

4. The monolithic article according to claim 3, wherein the ratio of inorganic particles to silicone resin in the inorganic oxide coating is 0.5:1 to 5:1, preferably 1:1 to 4:1, such as about 2:1 or 3:

1.

5. The monolithic article according to any preceding claim, wherein the washcoat comprises ceria zirconia, alumina, a noble metal selected from Pd, Pt or Rh, barium hydroxide, a rheology modifier and a C2-C6 aliphatic amino acid (e.g., 3-amino-propionic acid), and / or wherein the total washcoat loading is 35 g / L to 150 g / L, preferably 40 g / L to 125 g / L, for example 50 g / L to 100 g / L, 60 g / L to 90 g / L or 65 g / L to 85 g / L.

6. A method of forming a coated monolithic article (e.g., a coated monolithic article according to any preceding claim), the method comprising: i) providing a monolithic article having an inlet end and an outlet end, ii) applying an inorganic oxide coating to said inlet end, iii) optionally drying and / or calcining the inorganic coating, iv) applying a washcoat to said outlet end, v) optionally drying and / or calcining the obtained article.

7. A method according to claim 6, wherein the carrier coating is applied so that it extends from 60% to 100% of the length of the article from the outlet end, preferably from 65% to 95% of the length of the article from the outlet end, for example from 70% to 90% or from 75% to 80%.

8. The method according to any one of claims 6 to 7, wherein the washcoat layer is applied to the monolithic article at the outlet end of the monolithic article in a single or multiple doses, preferably in a single or two doses.

9. The method according to any one of claims 6 to 8, wherein a mixture of inorganic particles and silicone resin is sprayed as a dry particulate aerosol to form the inorganic oxide coating.

10. The method according to any one of claims 6 to 9, wherein the inorganic oxide coating comprises inorganic particles (e.g., inorganic particles comprising aluminosilicate zeolites) and a silicone resin, preferably wherein the inorganic particles comprise aluminosilicate zeolites selected from the group comprising AEI, BEA, CHA, FAU (e.g., zeolite Y) and MFI.

11. The method of any one of claims 6 to 10, wherein the silicone resin has a molecular weight greater than 1,000, preferably greater than 2,000, preferably greater than 5,000, preferably greater than 10,000, and / or a molecular weight less than 500,000, preferably less than 200,000.

12. The method according to any one of claims 6 to 11, wherein the organosilicon resin has the formula [R x SiX y O z ] n , wherein R is an alkyl or aryl group, X is a functional group bonded to silicon, and z is greater than 1 and less than 2, and preferably: y is less than 1 and / or y is less than x.

13. The method according to any one of claims 6 to 12, wherein the silicone resin has a crosslinking degree of greater than 55%, preferably greater than 60%, more preferably greater than 65%, and / or a crosslinking degree of less than 85%, preferably less than 80%.

14. An exhaust system comprising a coated monolithic article according to any one of claims 1 to 5 or prepared by a method according to any one of claims 6 to 13, and optionally an internal combustion engine.

15. A method for treating exhaust gas, the method comprising contacting the exhaust gas with a coated monolithic article according to any one of claims 1 to 5 or prepared by the method according to any one of claims 6 to 13.

Images