Method for forming an inorganic oxide coating on a monolithic article

Abstract

A method for forming an inorganic oxide coating on a monolith article is disclosed. The coated monolith article is suitable for exhaust gas treatment. The method includes spraying inorganic particles including an aluminosilicate zeolite having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol to form a coating layer. The present invention also provides a green porous monolith article for use in forming a monolith article for exhaust gas treatment. The green monolith article includes a dry particulate composition including inorganic particles and a silicone resin.

Description

[Technical Field]

[0001] The present invention relates to a method for forming an inorganic oxide coating on a monolith article. In particular, the coated monolith article is suitable for exhaust gas treatment. More particularly, the method comprises spraying inorganic particles and a silicone resin as a dry particulate aerosol to form a coating layer. The present invention also relates to a green porous monolith article for use in forming a monolith article for exhaust gas treatment. In particular, the green monolith article comprises a dry particulate composition including inorganic particles and a silicone resin. [Background technology]

[0002] There are concerns regarding the 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 relate to potential health effects, specifically those related to very small particles with 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 metal, ceramic, or metal fiber. However, the most common type in practical mass production is the wall-flow variety, made from porous ceramic material fabricated in the form of a monolithic array of many small channels extending along the length of the body. The alternating channels are plugged at one end, forcing exhaust gases through the porous ceramic channel walls, which prevent the majority of particulates from passing through, allowing only filtered gases to enter the environment. Commercially produced ceramic wall-flow filters include those made from cordierite, various forms of silicon carbide, and aluminum titanate. The actual shape and dimensions of practical filters on vehicles, 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 in the filter channel walls through which gases pass is typically in the range of 5 to 50 μm, usually around 20 μm. In sharp contrast, most diesel exhaust particulate matter from modern passenger car high speed diesel engines is very small in size, eg, 10-200 nm.

[0004] Some PM may be retained within the pore structure within the filter wall, which in some applications may gradually build up until the pores are bridged by a network of PM, which then readily forms a cake of particulates 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 burned on the filter as it is deposited, which prevents the particulate cake from building up on the filter.

[0005] Some filters, such as light-duty diesel particulate filters, require periodic removal of trapped PM from the filter to prevent excessive backpressure buildup, which can be detrimental to engine performance and reduce fuel economy. In diesel applications, retained PM is removed from the filter by burning it in air during a process during which 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. Toward the end of this process, typically called regeneration, removal of the last remaining particulates in the filter can significantly reduce filtration efficiency and lead to the burst release of many small particles into the environment. Thus, filters can have low filtration efficiency when they are first used, after each subsequent regeneration event, and during the latter part of each regeneration process.

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

[0007] WO 2011 / 151711 (incorporated herein by reference in its entirety) describes a method of making a filter for filtering particulate matter from exhaust gases emitted from a lean-burn internal combustion engine. The filter includes a porous substrate having an inlet surface and an outlet surface, the inlet surface being separated from the outlet surface by a porous structure including pores of a first average pore size. The inlet surface includes a crosslinked network including interconnected particles of a refractory material throughout the pores of the porous structure. The method includes contacting the inlet surface of the filter substrate with an aerosol including the refractory material in dry powder form.

[0008] WO 2021 / 028692 (incorporated herein by reference in its entirety) describes a vehicle exhaust filter, the vehicle exhaust filter comprising a porous substrate having an inlet face and an outlet face, the porous substrate including inlet channels extending from the inlet face and outlet channels extending from the outlet face, the inlet channels and the outlet channels being separated by a plurality of filter walls having a porous structure, the vehicle exhaust filter comprising a porous substrate having a pore size of 0.10 g / cm 3 and a vehicle exhaust filter is described in which the vehicle exhaust filter is filled with a refractory powder having a tap density before filling of less than 10 g / L, the refractory powder having a mass loading of less than 10 g / L, more than 40% of the refractory powder being disposed within the porous structure of the plurality of filter walls, and less than 60% of the refractory powder being coated on the exterior surfaces of the plurality of filter walls. WO 2021 / 028692 also describes suitable methods and apparatus for spraying a dry refractory powder, such as a dry particulate aerosol, onto channels of a porous substrate, preferably more than 50% of the refractory powder, and optionally up to 100% of the refractory powder, may be disposed within the porous structure of the plurality of filter walls.

[0009] WO 2020 / 047708 discloses articles including a material, such as a filtration material, for example, a porous body, such as a porous ceramic honeycomb body, including a porous inorganic layer disposed on at least a portion of the porous body, and methods for making such articles and porous bodies. The method includes contacting an inorganic material in a suspension with a gaseous carrier fluid, which suspension may be aqueous or organic, for example, an alcohol such as ethanol or methanol.

[0010] The present inventors have found that porous filter substrates treated with refractory powder materials, such as those described in WO 2021 / 028692, have poor water resistance and adhesion. For example, porous filter substrates treated with fumed alumina (e.g., Aeroxide® Alu 130) failed to provide the water resistance desired for use under certain engine conditions, particularly during continuous engine cold starts. As discussed above, for example, heavy-duty diesel (HDD) catalytic soot filter (CSF) applications require the filter to be able to withstand several ash washing cycles.

[0011] The present invention provides improved methods for the more efficient production of coated monolithic articles that advantageously exhibit higher water resistance, improved filtration efficiency, and improved thermal stability. Summary of the Invention

[0012] According to a first aspect of the present invention, there is provided a method for forming an inorganic oxide coating on a monolith article for the treatment of exhaust gases, the method comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; spraying inorganic particles comprising an aluminosilicate zeolite having a silica-to-alumina molar ratio (SAR) greater than 100:1 and a silicone resin as a dry particulate aerosol onto the gas-contact surface to form a coating layer; and firing the coating layer to provide a coated monolith article.

[0013] In a further aspect, there is provided a green porous monolith article for use in forming a monolith article for the treatment of exhaust gases, the monolith article comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; and spraying inorganic particles having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol onto a gas-contact surface to form a coating layer.

[0014] In another aspect, a coated monolith article for exhaust gas treatment is provided, obtainable by the method described herein for the first aspect. The coated monolith article has improved water resistance and thermal stability over known coated monolith articles, and as described herein, the article is preferably a catalyst article and / or a wall-flow filter. Such articles are particularly suitable for treating exhaust gases, particularly vehicle exhaust gases. The inventors have found that the highly crosslinked silicon dioxide present in the coated monolith article is highly effective in bonding inorganic particles, including aluminosilicate zeolites having an SAR greater than 100:1, to the gas-contacting surfaces of the channels of the porous monolith article, and that the presence of the aluminosilicate zeolites having an SAR greater than 100:1 imparts improved thermal stability to the coated monolith article.

[0015] In a further aspect of the present invention, a vehicle exhaust system is provided that includes a coated monolith article. DETAILED DESCRIPTION OF THE INVENTION

[0016] According to a first aspect of the present invention, there is provided a method of forming an inorganic oxide coating on a monolith article for the treatment of exhaust gases, the method comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; spraying inorganic particles having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol onto a gas-contact surface to form a coating layer; and firing the coating layer to provide a coated monolith article.

[0017] The present disclosure will now be further described. In the following sections, different aspects / embodiments of the present disclosure are defined in more detail. Each aspect / embodiment so defined may be combined with any other aspect / embodiment or aspects / embodiments, unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0018] The method of the present invention forms an inorganic oxide coating on a monolith article, thereby forming a coated monolith article. The monolith article having the inorganic oxide coating is suitable for use in treating exhaust gases. The exhaust gases may preferably be lean-burn exhaust gases from a vehicle engine, and the exhaust gases are treated by passing the exhaust gases through the channels of the monolith article, thereby contacting the exhaust gases with the gas-contacting surfaces of the plurality of channels.

[0019] The method includes providing a porous monolithic article including a plurality of channels for the passage of exhaust gas, each channel having a gas contact surface. Porous monolithic articles are well known in the art. The porous monolithic article is sometimes 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), i.e., the channels extend axially through the article. Typically, the channels have a square cross-section, although any known monolith design can be used.

[0020] The porous monolith article / substrate may be formed from, for example, sintered metal, ceramic, or metal fibers, etc. For example, the article may be formed from cordierite, various forms of silicon carbide, or aluminum titanate.

[0021] In some embodiments, the monolith article is a monolith filter. It is particularly preferred that the monolith filter is a wall-flow filter (which may also be known as a wall-flow monolith article). Wall-flow filters are well known and typically have adjacent channels alternately blocked at each end of the monolith article, such that, in use, exhaust gas passes along the inlet channel (i.e., the channel that is open at the inlet end of the monolith article to receive the exhaust gas) and passes through the channel wall into the adjacent outlet channel (i.e., the channel that is open at the outlet end of the monolith article).

[0022] The channel walls have a distribution of pores that provides the required porosity to the monolith article, with the average size of the pores in the channel walls, e.g., filter walls, typically being in the range of 5-50 μm. Each channel has a gas-contacting surface, i.e., each channel has a surface suitable for contacting, e.g., exhaust gases, in use. The surface may be provided by the channel wall surface and / or the pores contained therein.

[0023] In another particularly preferred embodiment, the porous monolith article is a catalytic article (i.e., a catalytic filter). Catalytic porous monolith articles are well known and are used for the oxidation, NO x The porous monolithic article may include one or more washcoats, preferably catalytic washcoats. A washcoat is a composition that coats and permeates the porous structure of the article. The article including the one or more washcoats is then preferably calcined before spraying inorganic particles and silicone resin onto the channels, as described herein. Thus, the catalytic article may be used in applications such as, for example, three-way catalysts (TWCs), NO x Absorbents, oxidation catalysts, selective catalytic reduction (SCR), hydrocarbon traps and lean NO x The three-way catalyst (TWC) may contain one or more platinum group metals, particularly those selected from the group consisting of platinum, palladium, and rhodium.

[0024] In another particularly preferred embodiment, the porous monolith article is a catalytic wall-flow filter. As a result, the article can be used in a variety of applications, such as catalyzed soot filters (CSFs), selective catalytic reduction filters (SCRFs), lean NOx filters, and the like. x The filter may be a lubricating oil 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)).

[0025] In another particularly preferred embodiment, the porous monolith article is a gasoline particulate filter that is a catalytic wall-flow filter comprising a TWC catalyst. Generally, gasoline particulate filters comprise a platinum group metal selected from the group consisting of Pt, Pd, Rh and mixtures thereof, an oxygen storage capacity (OSC) material, and an optional inorganic support material.

[0026] The shape and dimensions of the filter, such as its channel wall thickness and its porosity, may vary depending on the intended use of the filter. The filter may be configured for use with an internal combustion engine to filter exhaust gases emitted by the internal combustion engine. The internal combustion engine may be a gasoline spark-ignition engine. However, the filter finds particular application when configured for use with internal combustion engines in the form of diesel or gasoline engines.

[0027] The wall-flow filter may be an asymmetric wall-flow filter. Asymmetric wall-flow filter designs are known, for example, from International Publication No. WO 2005 / 030365, which discloses a honeycomb filter including an array of interconnected porous walls defining an array of first and second channels. The first channels are adjacent to the second channels on their sides and have a larger hydraulic diameter than the second channels. The first channels have a square cross-section, and the corners of the first channels are shaped such that the thickness of the porous walls adjacent the corners of the first channels is comparable to the thickness of the porous walls adjacent the edges of the first and second channels. In use, the first channel with the larger hydraulic diameter is positioned upstream. Society of Automotive Engineers SAE Technical Paper Series 2007-01-0656 explains that "there is a pressure loss penalty in the clean state of the ACT design [in catalyzed asymmetric cell technology (ACT) wall-flow filters] due to gas contraction and expansion at the inlet and outlet of the filter channels. However, the filter only remains completely clean (fully regenerated) for a short period of time during on-vehicle operation." WO 2005 / 030365 also explains that advantages of the asymmetric filter design include an increase in the effective surface area available for collecting soot and ash particles at the inlet section of the honeycomb filter, thus increasing the overall storage capacity of the honeycomb filter. The common general knowledge textbook "Catalytic Air Pollution Control - Commercial Technology", 3rd Edition, Ronald M. Heck et al., John Wiley & Sons, Inc., Hoboken, NJ, USA (2009) pp. 338-340 explains that "Such [asymmetric filter] channel designs allow for higher ash storage capacity combined with lower back pressure after ash loading due to the larger hydraulic diameter and larger inlet open volume. The ACT design also helps maintain the mechanical and thermal durability of the filter."

[0028] The method further includes spraying inorganic particles including an aluminosilicate zeolite having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol onto the gas-contacting surface to form a coating layer. Thus, the method includes spraying a dry powder (i.e., dry particles) suspended in a gas (i.e., as an aerosol) onto the gas-contacting surface of a plurality of channels on the monolith article. Spraying dry powder onto monolith articles is known in the art. Suitable methods and apparatus are described, for example, in International Publication Nos. 2011 / 151711 and 2021 / 028692.

[0029] The inventors have discovered that by combining inorganic particles, including an aluminosilicate zeolite having an SAR greater than 100:1, with a silicone resin in a dry powder to form a dry particle aerosol, the resulting article exhibits significantly improved water resistance, improved adhesion of the inorganic particles to the surface of the channel walls, and improved thermal stability of the coated monolith article.

[0030] One advantage of the present invention is that coated monolith articles, such as filters containing catalysts within the filter walls, can be processed after the catalyst is loaded onto the filter so that the inorganic coating does not interfere with the catalyst within and / or on the filter walls. Furthermore, the inventors have discovered that the silicone resins described herein more effectively retain and allow inorganic particles to adhere to the article channels without the need for high-temperature treatments that can be detrimental to the catalyst. The presence of an aluminosilicate zeolite with an SAR greater than 100:1 improved the thermal stability of the coated monolith articles.

[0031] Silicone resins are known and are branched, cage-like oligosiloxanes and polysiloxanes. The branching in silicone resins arises from the presence of so-called "T" and / or "Q" units in the resin, which refer to RSiO3 and SiO4 units, respectively (R is an alkyl or aryl group), with additional silicon units bonded to oxygen atoms. "M" units, i.e., R3SiO units, are terminal units where the oxygen atom provides the bond to the resin backbone. Similarly, "D" units, i.e., R2SiO2 units, provide linear connectivity across two oxygen atoms. One well-known unbranched and linear polysiloxane is polydimethylsiloxane (PDMS, i.e., (Me2SiO) n )

[0032] As will be understood, the requirement that inorganic particles and silicone resin be sprayed as a dry particulate aerosol requires that the silicone resin be solid particulate. Therefore, in this specification, the silicone resin may be referred to as silicone resin particles. Preferably, the silicone resin is solid at room temperature (e.g., about 25°C). Therefore, the silicone resin preferably has a melting point above 25°C, preferably above 30°C, and more preferably above 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, typically have lower melting points than branched silicone resins. For example, the melting point of PDMS is about -40°C. International Publication No. 2011 / 151711 discloses binding powders in place by treating them with polydimethylsiloxane, which forms silica when hydrolyzed at a sufficiently high temperature.

[0033] Similarly, the inventors have found that it is 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 being bound by theory, the inventors believe that silicone resins having such melting points and / or glass transition temperatures are particularly suitable for powder coating processes, i.e., particularly suitable for effectively dispersing particulates on the monolith article along with inorganic particles, yet low enough to allow low temperature firing, thereby effectively and efficiently adhering the inorganic particles to the gas-contacting surfaces of the channel walls.

[0034] The inorganic particles comprise an aluminosilicate zeolite having a SAR greater than 100:1. The aluminosilicate zeolite preferably has 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 zeolite has a SAR greater than 1000:1.

[0035] Aluminosilicate zeolites with an SAR greater than 100:1 are 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, and C. FI, 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, L IO, 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, R The skeletal type may be selected from UT, 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 having a SAR greater than 100:1 can have 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.In some embodiments, the aluminosilicate zeolite having a SAR greater than 100:1 can have a framework type selected from the group consisting of AEI, BEA, CHA, and MFI. In some embodiments, the aluminosilicate zeolite having a SAR greater than 100:1 has a BEA framework type. In some embodiments, the aluminosilicate zeolite having a SAR greater than 100:1 has an MFI framework type.

[0036] In addition to the aluminosilicate zeolite having an SAR greater than 100:1, the inorganic particles may also include a second zeolite material. Examples of suitable second zeolite materials include silicate zeolites, aluminosilicate zeolites, metal-substituted aluminosilicate zeolites, AlPO, MeAlPO, SAPO, MeAPSO, and the like. The second zeolite material may be selected from the group consisting of 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, and the like. , 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, NA B, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RW The skeletal type may be selected from R, 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.

[0037] The inorganic particles may include refractory oxide particles, which may be based on an oxide selected from the group consisting of 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, fumed alumina, fumed silica, fumed titania, fumed zirconia, fumed ceria, alumina aerogel, silica aerogel, titania aerogel, zirconia aerogel, ceria aerogel, or a mixture thereof. One or more fumed refractory powders (refractory oxide particles) may be produced by an exothermic process, such as flame pyrolysis.

[0038] The amount of aluminosilicate zeolite having an SAR greater than 100:1 present in the inorganic particles can be 10 to 99 wt%, preferably 50 to 99 wt%, more preferably 80 to 99 wt%, and most preferably 90 to 99 wt%. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 100:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 100:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 200:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 300:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 400:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 500:1. In some embodiments, the inorganic particles are comprised of an aluminosilicate zeolite having an SAR greater than 1000:1.

[0039] Preferably, the inorganic particles and / or silicone resin particles have a d by volume of more than 0.2 μm, preferably more than 0.5 μm, and / or less than 50 μm, preferably less than 25 μm, preferably less than 20 μm, preferably less than 15 μm, preferably less than 10 μm. 50 It has.

[0040] Preferably, the dry particulate aerosol has a density of 1.5 g / cm 3 The dry particulate composition may be referred to as a dry particulate powder. The dry particulate composition preferably comprises inorganic particles and / or a silicone resin. In some preferred embodiments, the inorganic particles have a tap density of less than 0.1 g / cm. 3 In another preferred embodiment, the inorganic particles have a tap density of less than 0.1 g / cm 3 more than 0.2 g / cm 3 For example, zeolite particles, such as Cu-substituted zeolites, preferably have a tap density of greater than about 0.25 g / cm 3 In another preferred embodiment, the inorganic particles, such as refractory oxide particles, can have a tap density of 1.4 g / cm 3 less than 1.3 g / cm 3 less than 1.2 g / cm 3 By way of example only, calcium aluminate may have a tap density of less than about 1 g / cm 3 Therefore, the inorganic particles may preferably have a tap density of 0.1 g / cm 3 ~1.4g / cm 3 , preferably 0.2 g / cm 3 ~1.2g / cm 3 The silicone resin particles may have a tap density of 0.3 g / cm 3 ~0.9g / cm 3 , preferably 0.5 g / cm 3 ~0.7g / cm 3 The dry particulate composition comprising a mixture of inorganic particles and a silicone resin preferably has the same tap density as that described for either the inorganic particles or the silicone resin individually. In some preferred embodiments, the tap density of the dry particulate composition is 0.5 to 1.4 g / cm. 3 , preferably 0.7 g / cm 3 ~1.2g / cm 3 is.

[0041] In a preferred embodiment, the spraying step includes a first spraying step in which inorganic particles are sprayed as a first dry particulate aerosol onto the gas-contacting surface to form an inorganic particle layer, and then a second spraying step in which a silicone resin is sprayed as a second dry particulate aerosol onto the inorganic particle layer to form a coating layer. Thus, the inorganic particles are sprayed onto the channels of the monolith article before the silicone resin is separately sprayed onto the channels coated with the inorganic particles.

[0042] Even more preferably, the mixture of inorganic particles and silicone resin is sprayed onto the gas-contacting surfaces as a dry particulate aerosol to form the coating layer, such that an intimate mixture of inorganic particles and silicone resin is coated onto the gas-contacting surfaces of the channels, enhancing adhesion of the inorganic particles to the channel walls upon baking of the silicone resin.

[0043] When a mixture of inorganic particles and a silicone resin is sprayed as a dry particulate aerosol onto a gas-contact surface to form a coating layer (preferably when the dry particulate composition consists of inorganic particles and a silicone resin), the weight ratio of inorganic particles to silicone resin in the mixture 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 4, preferably less than 3, preferably less than 2.5. For example, this ratio may be preferably about 1 or about 2. Preferably, this ratio is 0.5 to 4, preferably 0.7 to 3, preferably 0.9 to 2.5, preferably 1 to 2.

[0044] Preferably, the silicone resin has a molecular weight of more than 1,000, preferably more than 2,000, preferably more than 5,000, preferably more than 10,000, and / or a molecular weight of less than 500,000, preferably less than 200,000.

[0045] As used herein, molecular weight refers to the weight average molecular weight (M), which can be measured using any conventional means in the art.W ) refers to a molecular weight of 1,000 to 10,000, preferably 1,000 to 5,000, preferably 1,200 to 3,500, e.g., 1,500 to 2,000. Silicone resins having a molecular weight of less than 1,000 are typically liquids and are less suitable for dry spraying or do not have as much branching as larger molecules, which may enhance bonding of inorganic particles to the monolith article.

[0046] Nevertheless, the molecular weight of the silicone resin may 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 Mw from 8,000 to 15,000, some from 20,000 to 60,000, and others from 80,000 to 120,000.

[0047] The silicone resin has the formula [R x Six y O z ] n where R is an alkyl or aryl group, X is a silicon-bonded functional group, and z is greater than 1 and less than 2. As will be appreciated, n is large enough to provide the necessary oligomers or polymers for silicone resins, especially resins that are solid at room temperature. Depending on the molecular weight of the R and X groups, n greater than 10 will provide for M greater than 1,000. W can be achieved, and when n is greater than 100, M greater than 10,000 can be achieved. W can be achieved, and when n is greater than 1,000, M greater than 100,000 can be achieved. W Therefore, n may preferably be greater than 10, greater than 100, or greater than 1,000.

[0048] As will be appreciated, R is an alkyl or aryl group bonded to silicon, and X is a non-hydrocarbon functional group bonded to silicon. Similarly, since silicon is a tetravalent atom, it will be understood that x + y + 2z = 4. z is less than 2. This is provided by z = 2, x and y = 0, and silica (i.e., silicon dioxide, (SiO2) n ). Similarly, z is greater than 1. This is provided by z = 1, x + y = 2, and a substituted polysiloxane (e.g., (RXSiO) n ) consisting of a "D" unit that provides a linear resin (e.g., -O-(SiRX)-O-(SiRX)-O-). One example is polydimethylsiloxane. Thus, O refers to oxygen that bridges two silicon atoms in the polymer backbone of the silicone resin.

[0049] 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 one preferred embodiment, x + y is 1, providing a silicone resin generally known as polysilsesquioxane. 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, when the polysilsesquioxane is a polyalkylsilsesquioxane such as polymethylsilsesquioxane (MeSiO 3 / 2 ) n y is 0.

[0050] Typically, when present, X is one or more of H, hydroxy (OH), Cl, and C1-C6 alkoxy, preferably one or more of OH and C1-C6 alkoxy, preferably C1-C6 alkoxy selected from methoxy (OCH3) and ethoxy (OCH2CH3). In particularly preferred embodiments, X is one or both of OH and ethoxy. However, X is a functional group that may also be a reactive functional group such as aminyl (NH2, NR2), epoxy, acrylate, and vinyl, although these are less preferred as the presence of hydroxy or alkoxy groups is believed to provide more effective crosslinking during baking. As noted above, any oxygen present in a terminal functional group may be replaced by "O" in the above formula, which refers to a silicon bridging oxygen atom. z " does not contribute to

[0051] The inventors have found that the silicone resins described herein provide coated monolith articles with the advantageous benefits of enhanced water resistance and improved thermal stability. Silicone resins have been found to be particularly advantageous for bonding inorganic particles to monolith articles. Without being bound by theory, the inventors believe that the branched structure and physical properties of silicone resins allow the resin to initially melt during the firing step described herein, bond with (either intimately or deposited on) the inorganic particles on the gas-contacting surfaces of the channels, and then begin to harden. As the resin hardens, it forms additional -Si-O-Si-O-Si- bridges / bonds, further increasing its branched structure. Furthermore, the inventors believe that such bonds may also form with the gas-contacting surface (i.e., the monolith article itself) along with the inorganic particles, further bonding the particles in place in the article, for example, by forming -Si-O-Al- bonds. As the temperature continues to increase during firing, the R and X groups are oxidized, leaving behind a silica (SiO2) framework. Therefore, silicon and / or aluminum containing inorganic particles, such as zeolites, calcium aluminate, alumina and / or silica, may be preferred.

[0052] Preferably, the silicone resin has a degree of cross-linking greater than 55%, preferably greater than 60%, more preferably greater than 65%, and / or a degree of cross-linking less than 85%, preferably less than 80%.

[0053] As described herein, a compound of the formula [R x Six y O z ] n The silicon atoms of silicone resins such as those described by the formula (I) may be in one of four coordination environments, i.e., SiO(R / X)3, SiO2(R / X)2, SiO3(R / X), or SiO4, known in the art as "M," "D," "T," and "Q," respectively, given the tetravalent nature of silicon. 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 proportions of the number of silicon atoms in each coordination environment can be determined using standard spectroscopic techniques, such as multinuclear NMR spectroscopy, particularly 29 It can be determined using Si NMR spectroscopy. Alternatively, for commercially available silicone resins, the degree of crosslinking may be provided on the technical data sheet.

[0054] In other words, silicon dioxide (SiO2) is formed entirely from "Q" SiO4 units, in which each silicon atom is bonded to four connecting oxygen atoms. Thus, when d is 1, this gives silicon dioxide a 100% degree of crosslinking. On the other hand, as an example, PDMS is formed entirely from "D" Si(Me)2O2. Thus, when b is 1, this gives polydimethylsiloxane a 50% degree of crosslinking. Consequently, the silicone resin preferably has a degree of crosslinking between these two extremes and includes a mixture of such units. Thus, the silicone resin can preferably be composed of MDT units, MTQ units, DTQ units, or DT units.

[0055] Preferably, R is one or more C1-C6 alkyl or phenyl groups. Due to the oligomeric or polymeric nature of silicone resins, the number of monomer units is typically large. There can be many instances of both the R and X groups, so that a silicone resin described by a single monomer unit can contain multiple different groups. As noted above with respect to the functional group X, X may preferably be both OH and ethoxy. Similarly, R may contain two or more C1-C6 alkyl and / or phenyl groups. Thus, when R is described by two or more groups, such as R' and R'', the formula of the silicone resin can be written as [R' x’ R'' x’’ Six y O z ] n where x'+x"=x. This applies equally to the functional group X.

[0056] Preferably, R is one or more of a linear or branched alkyl and a phenyl, one or more of a linear alkyl and a phenyl, more preferably one or both of a methyl and a phenyl. In some preferred embodiments where R is both a methyl and a phenyl, the phenyl to methyl ratio is less than 2, preferably less than 1.5, preferably less than 1, preferably less than 0.5. In some embodiments, R is a phenyl. More preferably, R is a methyl (i.e., the ratio is 0).

[0057] Smaller organic groups such as methyl, methoxy, and ethoxy for the R and X groups are particularly preferred because they increase the SiO content of the starting silicone resin, reducing weight loss during baking and, in turn, reducing smoke and volatile material (such as HO, CO, and other volatile organics) loss during baking.

[0058] Thus, it is preferred that the silicon dioxide content of the silicone resin is greater than 50% by weight, preferably greater than 60% by weight, preferably greater than 70% by weight, and preferably greater than 80% by weight. Silicon dioxide content may also be referred to as ash content, which is the weight of the product remaining after complete oxidation (in this case, the product is silicon dioxide) by weight of the starting silicone resin. For example, oxidation may be carried out at 1000°C. Alternatively, the silicon dioxide content may be available from the technical data sheet of the appropriate commercially available silicone resin. Alternatively, the silicon dioxide content may be calculated based on the complete oxidation of silicon to silicon dioxide and the chemical formula of the resin. By way of example only, polymethylsilsesquioxane (MeSiO 3 / 2 ) n is about 42.7% by weight of silicon, based on the weight of the silicone resin, which is based on a formula weight of 66.1 and an atomic weight of silicon of 28.1. The silicon dioxide has a formula weight of 60.1, which is about 2.1 times greater than the formula weight of silicon. Therefore, the silicon dioxide content of the polymethylsilsesquioxane is 2.1 * 42.7 = 89.7% by weight (i.e., by weight of the silicone resin).

[0059] One particularly preferred silicone resin for use in the method of the present invention is a highly crosslinked ethoxylated poly(dimethylsiloxane) having a silicon dioxide content of about 82% by weight and a melting point of 35°C to 55°C.

[0060] The method further includes firing the coating layer to provide a coated monolith article, i.e., the method includes firing the porous monolith article having inorganic particles and silicone resin sprayed onto the gas contact surface of the plurality of channels.

[0061] Preferably, the calcination step comprises heating to a temperature of at least 200°C, preferably at least 300°C, more preferably at least 400°C, and / or to a temperature of up to 600°C, preferably up to 550°C, more preferably up to 530°C. Calcination therefore preferably comprises heating to a temperature of between 200°C and 600°C, preferably between 300°C and 550°C, preferably between 400°C and 530°C, more preferably between 400°C and 500°C, even more preferably between 400°C and 450°C.

[0062] Such temperatures have been found to be optimal for forming an effective binder that imparts its advantageous water resistance to the coated monolith article. Such temperatures are particularly advantageous when the porous monolith article is a catalytic article, such as a catalytic wall-flow filter, because they allow the silicone resin to be calcined to crosslinked silicon dioxide without adversely affecting catalytic efficiency (i.e., without degrading the catalytic article). Linear siloxanes, such as PDMS, not only do not provide the branching necessary to effectively bind inorganic particles and adhere them to the article, but their complete decomposition to SiO2 appears to require temperatures above 550°C, or even 600°C. Ideally, the calcination temperature is kept as low as possible to reduce the possibility of affecting the catalytic activity of any catalyst present in the monolith article.

[0063] In a further aspect of the present invention, there is provided a green porous monolith article for use in forming a monolith article for the treatment of exhaust gases, the green porous monolith article comprising a plurality of channels and comprising a dry particulate composition comprising inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1 and a silicone resin, the dry particulate composition being located within the channels and / or pores of the green porous monolith.

[0064] Thus, the green porous monolith article is suitable for use in forming a monolith article that can be used in exhaust gas treatment. Preferably, the green porous monolith article is for use in forming a monolith article, and preferably, the monolith article is used in exhaust gas treatment. The green porous monolith article comprises a dry particulate composition comprising a plurality of channels, the dry particulate composition comprising inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1, and a silicone resin, as described herein with respect to the first aspect. The dry particulate composition is located within the channels and / or pores of the green porous monolith, i.e., the composition coats the gas-contacting surfaces of the channels.

[0065] An uncalcined porous monolithic article comprising the dry particulate composition may be formed into a monolithic article by calcining, whereby the silicone resin of the dry particulate composition is decomposed to silicon dioxide, preferably by heating to temperatures described herein.

[0066] Preferably, the mass loading of the dry particulate composition in the green porous monolith article is less than 50 g / L, preferably less than 30 g / L. Preferably, the mass loading of the inorganic particles in the green porous monolith article is at least 5 g / L and / or less than 25 g / L. Preferably, the mass loading of the silicone resin in the green porous monolith article is at least 5 g / L and / or less than 25 g / L. In a preferred embodiment, the mass loading of the inorganic particles in the green porous monolith article is 5 g / L to 15 g / L and / or the mass loading of the silicone resin is 5 g / L to 15 g / L. By way of example, if the weight ratio of inorganic particles to silicone resin is 1:1, the loading of the inorganic particles may be 10 g / L and the loading of the silicone resin may be 10 g / L, resulting in a total loading of the dry particulate composition of 20 g / L. As an example, if the ratio is 2:1, the inorganic particle loading may be 10 g / L and the silicone resin loading may be 5 g / L, giving a total loading of 15 g / L.

[0067] In a further aspect, there is provided a green porous monolith article for use in forming a monolith article for the treatment of exhaust gases, the monolith article comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; and spraying inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol onto a gas-contact surface to form a coating layer.

[0068] In another aspect, a coated monolith article for exhaust gas treatment is provided, obtainable by the method described herein for the first aspect. The coated monolith article has improved water resistance over known coated monolith articles, and as described herein, the article is preferably a catalyst article and / or a wall-flow filter. Such articles are particularly suitable for treating exhaust gases, particularly vehicle exhaust gases. The inventors have found that the highly crosslinked silicon dioxide present in the coated monolith article is very effective at binding inorganic particles to the gas-contacting surfaces of the channels of the porous monolith article, and that the presence of an aluminosilicate zeolite having an SAR greater than 100:1 confers improved thermal stability to the coated monolith article.

[0069] In a further aspect of the present invention, a vehicle exhaust system is provided that includes a coated monolith article. [Example]

[0070] Sample A A GPF filter with a washcoat loading of 75 g / L was prepared from a cordierite substrate, 300 / 8, 1.3 L type, according to the procedure of Example 1 of U.S. Patent Application Publication No. 20200306692(A1).

[0071] Then, the GPF filter was filled with beta zeolite powder (SAR = 500, d 10 = 0.56 μm, d 50 = 2.6 μm, d 90 = 37.8 μm) and highly crosslinked ethoxylated poly(dimethylsiloxane) powder (silicon dioxide content 82 wt%, melting point 35°C to 55°C, d 90 A mixture of 550m2 (0.0001µm) and 500m2 (0.0001µm) was filled in a weight ratio of 3:1. The powder loading before firing was 4g / L. The powder mixture was loaded according to the method and apparatus described in WO 2021 / 028692. 3 A primary gas flow of 1000 sq. ft. / h of air was passed through the filter using a downstream vortex blower. Back pressure was monitored by a Wika® P30 pressure transmitter located below the filter. The refractory powder was dispersed into the primary gas flow using a fixed nozzle equipped with a 2 mm fluid cap with a 0.5 mm clearance air cap. Compressed air was supplied to the nozzle at 4 bar and positioned 500 mm from the inlet face. Back pressure was used to determine the stop point of the powder mixture spraying. After filling was complete, the filter was calcined at 530°C for 35 minutes.

[0072] Comparative sample B Comparative sample B is chabazite zeolite powder (SAR=20, d 10 = 0.73 μm, d 50 = 2.4 μm, d 90 = 43.3 μm) and highly crosslinked ethoxylated poly(dimethylsiloxane) powder (silicon dioxide content 82 wt%, melting point 35 °C to 55 °C, d 90 It was prepared in the same manner as sample A, except that a mixture of SiO2 and SiO2 (=5 μm) was filled at a weight ratio of 3:1. The powder loading before firing was 5 g / L.

[0073] Filtration Test The samples, both fresh and after hydrothermal aging, were tested on an engine bench in an RDE cycle for filtration efficiency. The filter samples were exposed to an atmosphere containing 2% oxygen, 10% water, and 88% nitrogen by weight at 1050°C for 4 hours. The test results are shown in Table 1. The filtration efficiency in Table 1 is the soot particulate removed over the entire drive cycle.

[0074] [Table 1]

[0075] The results show that the loss in filtration efficiency of Sample A after aging at 1050°C is much lower than that of Comparative Sample B.

[0076] As used herein, the term "dry powder" refers to a particulate composition that is not suspended or dissolved in a liquid. This does not necessarily mean that it is completely free of all water molecules. Dry powders are preferably free-flowing.

[0077] As used herein, the term "tap density" refers to the tap density of a powder measured at 1250 taps according to Method 1 of Section 2.9.35 of the European Pharmacopoeia 7.0.

[0078] As used herein, the term "g / L" (grams per liter) refers to the mass of the dry powder divided by the volume of the filter.

[0079] As used herein, the terms "loading" and "mass loading" when referring to the amount of powder refer to the mass of powder added to the filter, which may be measured by weighing the filter before and after adding the powder to the filter.

[0080] In this specification, "d 50The term "(by volume)" refers to the amount of d measured by a Malvern Mastersizer® 3000 equipped with an Aero s dispersion unit available from Malvern Panalytics Ltd, Malvern, UK. 50 Refers to measurements (by volume). Dispersion conditions: air pressure = 2 barg, feed rate = 65%, hopper gap = 1.2 mm. Refractive index and absorption parameters are set according to the instructions provided in the Malvern Mastersizer® 3000 User Manual.

[0081] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Use of the term "comprising" is intended to be interpreted as including such features but not excluding other features, and is intended to include options of features necessarily limited to those recited. In other words, unless the context clearly dictates otherwise, this term also includes the limitations "consisting essentially of" (intended to mean that certain additional components may be present provided they do not materially affect the essential properties of the recited feature) and "consisting of" (intended to mean that when components are expressed as percentages by their proportions, these add up to 100%, while accounting for any unavoidable impurities, but that other features may not be included).

[0082] The foregoing detailed description has been provided for purposes of illustration and example, and is not intended to limit the scope of 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.

Claims

1. 1. A method for forming an inorganic oxide coating on a monolith article for the treatment of exhaust gases, comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; spraying inorganic particles comprising an aluminosilicate zeolite having a silica-to-alumina molar ratio (SAR) greater than 100:1 and a silicone resin as a dry particulate aerosol onto the gas-contacting surface to form a coating layer; and firing the coating layer to provide a coated monolith article.

2. 2. The method of claim 1, wherein the aluminosilicate zeolite has a SAR greater than 200:1, preferably greater than 300:1, more preferably greater than 400:

1.

3. 2. The method of claim 1, wherein the aluminosilicate zeolite is selected from the group consisting of AEI, BEA, CHA, and MFI.

4. 2. The method of claim 1, wherein the monolithic article is a monolithic filter, preferably a wall-flow filter, and / or a catalytic article, preferably a catalytic wall-flow filter.

5. (i) the inorganic particles are sprayed onto the gas-contacting surface as a first dry particulate aerosol to form an inorganic particle layer, and then the silicone resin is sprayed onto the inorganic particle layer as a second dry particulate aerosol to form the coating layer; or (ii) spraying the mixture of inorganic particles and silicone resin as a dry particulate aerosol onto the gas-contact surface to form the coating layer.

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

7. 7. The method according to any one of claims 1 to 6, wherein the silicone resin has a glass transition temperature (Tg) above 30°C, preferably above 35°C, and / or below 100°C, preferably below 80°C.

8. The silicone resin has the formula [R ｘ Six ｙ O ｚ ] ｎ wherein R is alkyl or aryl, X is a silicon-bonded functional group, and z is greater than 1 and less than 2.

9. 9. The method of claim 8, wherein y is less than 1 and / or y is less than x.

10. 10. The method according to claim 8 or 9, wherein the silicone resin has a degree of crosslinking of more than 55%, preferably more than 60%, more preferably more than 65%, and / or a degree of crosslinking of less than 85%, preferably less than 80%.

11. R is C １ ~C ６ A method according to any one of claims 8 to 10, wherein the alkyl is one or more of alkyl and phenyl, preferably one or more of straight chain alkyl and phenyl, preferably one or both of methyl and phenyl, more preferably methyl.

12. X is H, OH, Cl and C １ ~C ６ one or more of alkoxy, preferably OH and C １ ~C ６ A method according to any one of claims 8 to 11, wherein the alkyl group is one or more of alkoxy, more preferably one or both of OH and ethoxy.

13. 13. The method according to any one of the preceding claims, wherein the silicon dioxide content of the silicone resin is greater than 50% by weight, preferably greater than 60% by weight, preferably greater than 70% by weight, preferably greater than 80% by weight.

14. 14. The method according to any one of claims 1 to 13, wherein the aluminosilicate zeolite is present in the inorganic particles in an amount of 10 to 99 wt%, preferably in an amount of 50 to 99 wt%, more preferably in an amount of 80 to 99 wt%, and most preferably in an amount of 90 to 99 wt%.

15. The inorganic particles have a d by volume of more than 0.2 μm and / or less than 50 μm, preferably less than 25 μm ５０ The method according to any one of claims 1 to 14, comprising:

16. 16. The method of any one of claims 1 to 15, wherein calcining comprises heating to a temperature of at least 200°C, preferably at least 300°C, more preferably at least 400°C, and / or to a temperature of at most 600°C, preferably at most 550°C, more preferably at most 530°C.

17. The method of any one of claims 1 to 16, wherein the monolithic article comprises one or more platinum group metals.

18. The dry particulate aerosol has a density of 1.5 g / cm ３ The method of any one of claims 1 to 17, wherein the dry particulate composition has a tap density of less than 1000 .mu.m.

19. 19. The method according to any one of claims 1 to 18, wherein the mixture of inorganic particles and silicone resin is sprayed as a dry particulate aerosol onto the gas-contact surface to form the coating layer, and wherein in the mixture the weight ratio of inorganic particles to silicone resin is greater than 0.5, preferably greater than 0.7, preferably greater than 0.9, and / or less than 4, preferably less than 3, preferably less than 2.

5.

20. 1. An unsintered porous monolith article for use in forming a monolith article for the treatment of exhaust gases, the article comprising a dry particulate composition comprising inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1, the inorganic particles comprising a plurality of channels, the inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1, and a silicone resin, wherein the dry particulate composition is located within the channels and / or pores of the unsintered porous monolith.

21. 21. The green porous monolith article of claim 20, wherein the mass loading of the dry particulate composition is less than 50 g / L, preferably less than 30 g / L.

22. 1. A green porous monolith article for use in forming a monolith article for the treatment of exhaust gases, said monolith article comprising: providing a porous monolithic article including a plurality of channels for the passage of exhaust gases, each channel having a gas contact surface; spraying inorganic particles comprising an aluminosilicate zeolite having an SAR greater than 100:1 and a silicone resin as a dry particulate aerosol onto said gas contact surface to form a coating layer.

23. A coated monolithic article for exhaust gas treatment obtainable by the method according to any one of claims 1 to 19.

24. 24. A vehicle exhaust system comprising the coated monolith article of claim 23.

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