Improvement of or relating to particulate filters

Abstract

The present disclosure relates to a method of forming a coated monolith article for the treatment of exhaust gases, the method comprising the steps of holding a porous monolith article in a coating apparatus, the porous monolith article including a plurality of channels for the passage of exhaust gases, each channel having a gas contacting surface, depositing cementitious particles as a dry powder on the gas contacting surfaces of at least some of the channels, and reacting the cementitious particles with a liquid or gaseous reagent in situ within the porous monolith article to provide a coated monolith article.

Description

Technical Field

[0001] The present disclosure relates to a method of forming a coated monolithic article for the treatment of exhaust gas and to the coated monolithic article. For example, the present disclosure relates to depositing cementitious particles on the gas contact surface of a monolithic article as a dry powder and reacting the cementitious particles in situ within the monolithic article with a liquid or gaseous reagent to provide the coated monolithic article.

Background Art

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

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

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

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

[0006] Therefore, it is desirable to always improve and / or maintain the 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] International Patent Application Publication No. 2021 / 028691 (A1), which is incorporated herein by reference in its entirety, describes that a filter having improved filtration efficiency can be obtained by a certain treatment method during the initial life of the filter when first used, and / or during and immediately after regeneration, and / or when soot is deposited on the filter, and the treatment method comprises a) a step of containing a dry powder in a reservoir; b) a step of disposing a filter within a filter holder, the filter comprising a porous substrate having an inlet face and an outlet face, the inlet face and the outlet face being separated by a porous structure; c) a step of establishing a primary gas flow through the porous structure of the filter by applying a reduced pressure to the outlet face of the filter; d) transferring the dry powder from the reservoir to a spraying device disposed upstream of the inlet face of the filter; e) spraying the dry powder towards the inlet face of the filter using the spraying device such that the dry powder is entrained in the primary gas stream and passes through the inlet face of the filter to contact the porous structure.

[0008] International Patent Application Publication No. 2021 / 028691 (A1) describes how dry powder can contain one or more of fumed alumina, fumed silica, fumed titania, silica aerogel, alumina aerogel, carbon aerogel, titania aerogel, zirconia aerogel or ceria aerogel. In particular, an example of a filter coated with fumed aluminum oxide having a tap density of 0.05 g / L and a d50 of 5.97 μm is described. The filter is preferably fired after coating with the dry powder.

[0009] This treatment method has been found to produce filters with improved filtration efficiency characteristics, but it is still desirable to further improve the treatment of such filters, particularly to improve the durability of the treated filters. In particular, it is desirable to improve the water resistance and adhesion of the powder deposited on the gas contact surface of the monolithic article in dry form. SUMMARY OF THE INVENTION

[0010] Aspects and embodiments of the present disclosure will now be described. One or more features of one aspect or embodiment of the present disclosure may be combined with one or more features of any other aspect or embodiment of the present disclosure, unless the immediate context teaches otherwise. In particular, any feature shown as being preferred or advantageous can be combined with any other feature or features shown as being preferred or advantageous.

[0011] In a first aspect, the present disclosure is a method of forming a coated monolithic article for the treatment of exhaust gas, comprising A step of holding a porous monolith article within a coating apparatus, wherein the porous monolith article includes a plurality of channels for the passage of exhaust gas, and each channel has a gas contact surface; the holding step A step of depositing cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels A step of reacting the cementitious particles in situ within the porous monolith article with a liquid or gaseous reagent to provide a coated monolith article. A method is provided that includes these steps

[0012] Advantageously, according to what the applicant has discovered, the cementitious particles are deposited in dry form on the gas contact surfaces of the monolith article and are then reacted in situ to provide a strongly adhered cementitious coating that exhibits high resistance to exposure to water during use

[0013] The method includes providing a porous monolith article that includes a plurality of channels for the passage of exhaust gas, and each channel has a gas contact surface. Porous monolith articles are well known in the art. Porous monolith articles may also be referred to as substrates, preferably honeycomb substrates, preferably ceramic honeycomb substrates. Such substrates include a plurality of channels suitable 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 monolith design may be employed

[0014] The porous monolith article / substrate may be formed from, for example, sintered metal, ceramic, or metal fibers. For example, the article may be formed from cordierite, various forms of silicon carbide, or aluminum titanate

[0015] In some embodiments, the monolithic article is a monolithic filter. The monolithic filter is particularly preferably a wall flow filter (which may also be known as a wall flow monolithic article). Wall flow filters are well known and typically, adjacent channels are alternately blocked at each end of the monolithic article, so that in use, the exhaust gas passes along the inlet channels (i.e., the channels that are open at the inlet end of the monolithic article to receive the exhaust gas) and is forced to pass through the channel walls and into the adjacent outlet channels (i.e., the channels that are open at the outlet end of the monolithic article).

[0016] The channel walls have a distribution of pores that provides the required porosity to the monolithic article, and the average dimension of the pores in the channel walls, such as the filter walls, is typically in the range of 5 to 50 μm. Each channel has a gas contact surface. That is, each channel has a surface suitable for contacting, for example, exhaust gas in use. The surface may be provided by the channel wall surface and / or the pores contained therein.

[0017] In another particularly preferred embodiment, the porous monolithic article is a catalyst article (i.e., a catalytic article). Catalytic porous monolithic articles are well known and exhibit catalytic functions such as oxidation, NOx trapping, or selective catalytic reduction activity. The porous monolithic article may include one or more washcoats, preferably catalytic washcoats. A washcoat is a composition that coats and penetrates the porous structure of the article. The article including the one or more washcoats is then preferably fired before depositing cementitious particles on the channels as described herein. Thus, the catalytic article may be selected from, for example, a three way catalyst (TWC), a NOx absorber, an oxidation catalyst, a selective reduction catalyst (SCR), a hydrocarbon trap, and a lean NOx catalyst. The catalytic article may contain one selected from the group consisting of one or more platinum group metals, particularly platinum, palladium, and rhodium.

[0018] In particularly preferred embodiments, the porous monolith article is a catalytic wall flow filter. As a result, the article can be, for example, a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), a gasoline particulate filter (GPF), an ammonia slip catalyst filter (ASCF), or a combination of two or more thereof (e.g., a filter comprising a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC)).

[0019] The shape and dimensions of the filter, such as the channel wall thickness and its porosity, can vary depending on the intended use of the filter. The filter can be configured to be used with an internal combustion engine to filter the exhaust gas emitted by the internal combustion engine. The internal combustion engine can be a gasoline spark ignition engine. However, the filter finds particular use when configured to be used with an internal combustion engine in the form of a diesel or gasoline engine.

[0020] In some embodiments, the cementitious particles are inorganic particles. Preferably, the cementitious particles Silicate( silicate ) , Aluminate( aluminate ) , or Aluminosilicate( aluminosilicate ) and include or consist of. The cementitious particles may consist of a single compound or a mixture of compounds.

[0021] In some preferred embodiments, the cementitious particles include or consist of hydraulic cementitious particles, and the step of reacting the cementitious particles with a liquid or gaseous reagent includes hydrating the hydraulic cementitious particles.

[0022] In some particularly preferred embodiments, the hydraulic cementitious particles comprise or consist of calcium silicate, calcium aluminate, calcium aluminosilicate and / or calcium aluminoferrite.

[0023] In a particularly preferred embodiment, the liquid or gaseous reagent comprises or consists of water molecules.

[0024] In some embodiments, the step of hydrating the hydraulic cementitious particles comprises allowing water molecules in the liquid phase to penetrate into the channels. For example, the water molecules in the liquid phase may comprise an aerosolized mist, and allowing the water molecules to penetrate into the channels may comprise spraying the aerosolized mist into the porous monolithic article and / or drawing the aerosolized mist through the porous monolithic article. Spraying and / or drawing the aerosolized mist may be carried out using a coating apparatus.

[0025] However, in a preferred embodiment, the step of hydrating the hydraulic cementitious particles comprises exposing the channels to water molecules in the gas phase, for example, within a humidification chamber.

[0026] In a particularly preferred embodiment, the water molecules in the gas phase comprise a humidifying gas, for example, humid air.

[0027] In some embodiments, the humidifying gas is actively blown through and / or drawn through the porous monolithic article, for example, using an external pump and / or a vacuum.

[0028] However, in a preferred embodiment, the humidifying gas diffuses and / or convects within the porous monolithic article.

[0029] In some embodiments, the humidifying gas has a relative humidity (RH) of 60% or 65% or 70% or 75% or 80% or 85% or 90% or 95% or more.

[0030] In a preferred embodiment, the step of hydrating the hydraulic cementitious particles includes, for example, a hydrothermal treatment in a hydrothermal oven.

[0031] The hydrothermal treatment may include subjecting the porous monolith article to an ambient temperature of 40 °C or higher, or 60 °C or higher, or 80 °C or higher, or 100 °C or higher.

[0032] In some embodiments, the hydrothermal treatment includes subjecting the porous monolith article to an ambient temperature of 80 °C, or 100 °C, or 120 °C, or 150 °C or lower.

[0033] In some embodiments, the hydrothermal treatment includes exposing the porous monolith article to a humidifying gas for 2 to 24 hours, optionally 4 to 12 hours, and optionally 6 to 8 hours.

[0034] In some embodiments, the cementitious particles comprise or consist of geopololymer precursor particles, and the step of reacting the cementitious particles with a liquid or gaseous reagent includes the step of chemically reacting the geopololymer precursor particles.

[0035] In some preferred embodiments, the geopololymer precursor particles comprise or consist of aluminosilicate, pozzolan, calcined clay, metakaolin, fly ash, blast furnace slag, or silica fume.

[0036] In some embodiments, the liquid or gaseous reactant is an alkali, preferably Alkali polysilicate( alkali polysilicate ) and more preferably comprises or consists of sodium silicate or potassium silicate.

[0037] In some embodiments, the cementitious particles have a density of 1 to 3 g / cm 3 optionally 1.5 to 2.5 g / cm 3 optionally about 2 g / cm3 has a tap density of

[0038] In some preferred embodiments, the cementitious particles have a d50 (by volume) of 5 to 60 microns.

[0039] The step of reacting the cementitious particles with a liquid or gaseous reagent is carried out before the monolithic article is installed in a device for the treatment of exhaust gases. For example, the reacting step can be carried out in a treatment apparatus before the monolithic article is installed in a device such as an exhaust system. The treatment apparatus may be, for example, a coating apparatus described herein, or a separate water spraying or atomizing apparatus, or a hydrothermal oven.

[0040] In some embodiments, the step of depositing the cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels includes spraying the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolithic article. In some preferred embodiments, the cementitious particles prior to spraying are held as dry particulates in a reservoir.

[0041] Thus, the method may preferably include spraying the cementitious particles as a dry particulate aerosol onto the gas contact surface. The method may include spraying a dry powder (i.e., dry cementitious particles) suspended in a gas (i.e., as an aerosol) onto the gas contact surfaces of a plurality of channels on the monolithic article. Suitable methods and apparatuses for spraying a dry powder onto a monolithic article are described, for example, in WO 2011 / 151711 (A1), WO 2021028691 (A1) and WO 2021 / 028692 (A1), the entire contents of all of which are incorporated herein by reference.

[0042] In a particularly preferred embodiment, the step of depositing cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels comprises drawing the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolith article and along the channels by applying a vacuum to the outlet face of the porous monolith article.

[0043] In some embodiments, the cementitious particles are deposited at a loading level of 1.5 to 15 g / l, optionally 3 to 10 g / l, optionally 4.5 to 9 g / l, optionally 4.5 g / l, or 6 g / l, or 9 g / l.

[0044] It is particularly preferred that the coated monolith article remains unburned prior to its installation into a device for the treatment of exhaust gases.

[0045] One of the main advantages of the method of the present disclosure is that the monolith article does not require a high temperature treatment, such as firing, to attach the particles to the gas contact surface after deposition of the dry particles. Instead, the cementitious particles are chemically reacted in-situ to form a cementitious coating. As used herein, "high temperature treatment" refers to a process carried out at a temperature typical for the firing of filters, e.g., typically above 400 °C or 500 °C, and should be contrasted with a process carried out at a high temperature of 150 °C or less.

[0046] By using a chemical reaction step instead of a firing step, the energy required for the manufacture of the coated monolith article is reduced. In addition, the method avoids the potentially harmful effects of high temperatures on any catalyst particles present in the monolith article and enables the catalyst particles to be more effectively retained and adhered in the monolith article channels.

[0047] In a second aspect, the present disclosure provides a coated monolith article obtainable by the method of the first aspect described above.

[0048] In a third aspect, the present disclosure provides a coated monolithic article for the treatment of exhaust gas, the monolithic article including a plurality of channels for the passage of exhaust gas, each channel having a gas contact surface, and at least some of the gas contact surfaces of the channels being at least partially coated by a cement-based coating.

[0049] In particularly preferred embodiments, the cement-based coating comprises or consists of calcium silicate hydrate, calcium aluminate hydrate, calcium aluminosilicate hydrate and / or calcium aluminoferrite hydrate.

[0050] In some embodiments, the cement-based coating comprises or consists of a geopolimer.

[0051] In preferred embodiments, the coated monolithic article is one or more of a catalyzed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), and a gasoline particulate filter (GPF).

[0052] 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 all water molecules are completely absent. The dry powder is preferably free-flowing.

[0053] As used herein, the term "tap density" refers to the tap density of a powder measured according to Method 1 of Section 2.9.35 of the European Pharmacopoeia 7.0 with 1250 taps.

[0054] As used herein, the term "g / l" (grams per liter) refers to the mass of a given substrate divided by the volume of the monolithic article.

[0055] As used herein, the terms "fill" and "mass fill" when referring to the amount of dry powder refer to the mass of the dry powder added to the monolithic article, which can be measured by weighing the monolithic article before and after the addition of the dry powder.

[0056] As used herein, the term "d50 (by volume)" refers to the d50 (by volume) measurement value measured by a Malvern Mastersizer® 3000 with an Aero s dispersion unit available from Malvern Panalytics Ltd, (Malvern, UK). Dispersion conditions: air pressure = 2 barg, feed rate = 65%, hopper gap = 1.2 mm. Set the refractive index and absorption parameters according to the instructions provided in the Malvern Mastersizer® 3000 User Manual.

[0057] As used herein, the term "vacuum generator" refers to a device or combination of devices that functions to generate a reduced pressure. Non-limiting examples of suitable devices include vacuum generators operating based on the Venturi principle, vacuum pumps, such as rotary vane and liquid ring vacuum pumps, and eddy current blowers.

[0058] As used herein, the term "pressure sensor" refers to a device or combination of devices that functions to measure absolute pressure and / or relative pressure. Non-limiting examples of suitable devices include pressure transducers, which can be diaphragm-type pressure transducers. For example, a Wika® P30 pressure transmitter available from WIKA Alexander Wiegand SE & Co. KG (Klingenberg, Germany) can be used.

[0059] As used herein, the term "controller" refers to a function that may include hardware and / or software. The controller may include a control unit, or may be a computer program running on dedicated or shared computing resources. The controller may include a single unit, or may be composed of a plurality of sub-units operably connected. The controller may be disposed on one processing resource, or may be distributed across spatially separated processing resources. The controller may include a microcontroller, one or more processors (such as one or more microprocessors), memory, configurable logic, firmware, and the like.

[0060] In this specification, ranges and amounts may be expressed as "about" a particular value or range. "About" also includes the exact amount. For example, "about 2 μm" means both "about 2 μm" and "2 μm". Generally, the term "about" includes amounts that are expected to be within experimental error. The term "about" may include values within less than 5% to more than 5% of the provided value. For example, "about 2 μm" means "1.9 μm to 2.1 μm".

[0061] As used herein, the expression that a dry powder "consists of" means a dry powder that consists essentially of only the specific components, excluding inevitable impurities that are commonly encountered as recognized by those skilled in the art.

Brief Description of the Drawings

[0062] Here, with reference to the accompanying drawings, the present disclosure will be described by way of example only.

[0063]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0064] According to the present disclosure, a method for forming a coated monolith article for the treatment of exhaust gas is provided. The method includes depositing cementitious particles as a dry powder on one or more gas contact surfaces of at least some of the channels of a porous monolith article, and then reacting the cementitious particles in situ with a liquid or gaseous reagent within the porous monolith article to produce a coated monolith article.

[0065] The step of depositing cementitious particles on the gas contact surface is carried out using a porous monolith article held within a coating apparatus. Various coating apparatuses can be used to deposit the cementitious particles. In the following description, one preferred embodiment of the coating apparatus 1 will be described as an example with reference to FIG. 1.

[0066] FIG. 1 shows a schematic view of a coating apparatus 1 (hereinafter simply referred to as "apparatus 1").

[0067] The apparatus 1 can include a reservoir 3 for containing cementitious particles 4 in the form of a dry powder. A holder 5 for holding the monolith article 2 may be provided. A vacuum generator 6 may be provided to establish a primary gas flow through the porous structure of the monolith article 2 during use by applying a reduced pressure to the outlet surface of the monolith article 2. A transport device 8 for transporting the cementitious particles 4 from the reservoir 3 to the spraying device 7 may be provided. The spraying device 7 may be provided to receive the cementitious particles 4 from the transport device 8 and spray the cementitious particles 4 towards the inlet surface of the monolith article 2. A controller 9 may be provided and configured to control the operation of the apparatus 1.

[0068] The reservoir 3 can receive the cementitious particles 4 from the dry powder inlet 11. The dry powder inlet 11 can be the output of the upstream bulk supply of the cementitious particles 4. For example, the dry powder inlet 11 can be a conduit connected upstream of a further reservoir of the cementitious particles 4. The dry powder inlet 11 can represent manual, semi-automatic or automatic refilling of the reservoir 3 through the lid or opening of the reservoir 3.

[0069] The reservoir 3 can comprise one or more hoppers. The reservoir 3 can comprise one hopper. In the illustrated example of FIG. 1, the reservoir 3 comprises a first hopper 12 and a second hopper 13. The second hopper 13 may be downstream of the first hopper 12 for receiving the cementitious particles 4 output from the first hopper 12. One or more hoppers may be provided in separate housings. Alternatively, one or more hoppers may be provided in a single housing. One or more hoppers can comprise one or more chambers of a single container.

[0070] The reservoir 3 can comprise an injection device 15. The injection device 15 can inject the cementitious particles 4 by one or more of weight, volume, number of particles, time. The injection device 15 can be arranged at or near the outlet of the reservoir 3. The injection device 15 can be arranged at or near the outlet of one or more hoppers of the reservoir 3. The injection device can be arranged at or near the outlet of the first hopper 12.

[0071] The injection device 15 can be supplied with the cementitious particles 4 from the reservoir 3 by weight measurement.

[0072] The injection device 15 can be a loss-in-weight feeder. Non-limiting examples of suitable injection devices include Coperion. Examples include the Coperio® K-Tron Type K2-ML-T35 Gravimetric Twin Screw Feeder available from Coperion GmbH (Stuttgart, Germany), and the All-Fill® Series S1 Micro-Fill available from All-Fill International Ltd, (Sandy, UK).

[0073] The transport device 8 transports the cementitious particles 4 from the reservoir 3 to the spraying device 7. The transport device 8 may supply the cementitious particles 4 gravimetrically at least part of the way towards the spraying device 7.

[0074] The transport device 8 may comprise one or more components. The transport device 8 may comprise one or more conduits, such as passages, pipes, hoses, etc.

[0075] If the reservoir 3 comprises two or more hoppers, the transport device 8 may transport the cementitious particles 4 between the hoppers. The transport device 8 may supply the cementitious particles 4 gravimetrically between the hoppers. The transport device 8 may comprise a first conduit 14 extending between the first hopper 12 and the second hopper 13. The first conduit 14 may extend from a first housing to a second housing. Alternatively, the first conduit 14 may extend from a first chamber to a second chamber of a single container. The cementitious particles 4 may be supplied gravimetrically along the first conduit 14. The transport device 8 may comprise a second conduit 16 extending from the second hopper 13 to the spraying device 7.

[0076] The spraying device 7 is provided to receive the cementitious particles 4 from the transport device 8 and spray the cementitious particles 4 towards the inlet surface of the monolithic article 2. The spraying device 7 may comprise a secondary gas flow generator for generating a secondary gas flow that can be used to spray the cementitious particles 4 towards the inlet surface of the monolithic article 2.

[0077] The spraying device 7 may further include one or more outlets for discharging the cementitious particles 4 towards the inlet surface of the monolithic article 2. The one or more outlets of the spraying device may have an aperture size of 1 to 10 mm. The one or more outlets may be provided within one or more nozzles. Each of the one or more nozzles may include one or more spray outlets. In the illustrated example of FIG. 1, a single nozzle 25 having a plurality of spray outlets is provided.

[0078] The secondary gas flow generator may include a compressed gas generator. In the illustrated example of FIG. 1, the secondary gas flow generator includes a compressed air generator that may include a compressor 22. The compressor 22 may receive air from an air inlet 21 and supply compressed air to one or more outlets of the spraying device 7 via a supply line 23. A return line 24 may be provided. Valves and control units necessary for operation may be provided as known to those skilled in the art.

[0079] An interconnection may be provided between the transport device 8 and the spraying device 7, whereby the cementitious particles 4 can be transported from the transport device 8 to the spraying device 7. The interconnection may be provided at or near one or more outlets of the spraying device 7. In one example, the interconnection may be provided in the nozzle 25. Alternatively, the interconnection may be provided in or near the reservoir 3, for example, in or near the second hopper 13 of the reservoir 3. In one example, the interconnection is a fluid connection between the supply line 23 and the second conduit 16. For example, the secondary gas flow of the spraying device 7 is fluidly connected to the second conduit 16 at or near the outlet of the second hopper 13 to fluidize the cementitious particles 4 and assist in the transport of the cementitious particles 4 in the form of a dry powder along at least a portion of the second conduit 16. For example, the secondary gas flow of the spraying device 7 may entrain the cementitious particles 4 from the second conduit 16. For example, the secondary gas flow of the spraying device 7 may generate a suction force in the second conduit to draw the cementitious particles 4 into the secondary gas flow.

[0080] In one example, the spraying device 7 comprises a compressed air gun. A non-limiting example of a suitable compressed air gun is the STAR Professional gravity feed spray gun 1.4 mm, part number STA 2591100C.

[0081] The holder 5 can function to maintain the monolithic article 2 in a stationary position during the deposition of the cementitious particles 4. The holder 5 can grip the upper end and / or the lower end of the monolithic article 2. The holder 5 can comprise an inflatable upper seal bladder 31 (also referred to as an upper inflatable collar) and / or an inflatable lower seal bladder 30 (also referred to as a lower inflatable collar) that respectively support the upper end and the lower end of the monolithic article 2. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 can contact and / or engage the outer surface of the monolithic article 2. Each can form a liquid-tight or gas-tight seal around the monolithic article 2. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 can be supported by one or more housings (e.g., supported by the inner walls of one or more housings).

[0082] The apparatus 1 can be configured such that the monolithic article 2 is disposed within the holder 5 in a vertical orientation with the inlet face of the monolithic article uppermost. At least a portion of the spraying device 7 can be disposed vertically above the inlet face. The spraying direction of the spraying device 7 can be coaxial with the longitudinal axis of the monolithic article 2. The spraying direction and the longitudinal axis of the monolithic article 2 may coincide.

[0083] The apparatus 1 can further comprise a flow conduit 10 disposed between the spraying device 7 and the inlet face of the monolithic article 2. The flow conduit 10 can function to restrict and channel a primary gas flow towards the inlet face of the monolithic article 2. The flow conduit 10 can function to align the primary gas flow such that the direction of flow of the primary gas flow when it contacts the inlet face of the monolithic article 2 is perpendicular to the inlet face.

[0084] The flow conduit 10 may be empty in order to provide an unobstructed flow path between the spray device 7 and the inlet surface of the monolithic article 2. Alternatively, the flow conduit 10 may comprise a flow regulator inserted between the spray device 7 and the inlet surface of the monolithic article 2, and the flow regulator acts to promote the dispersion of the cementitious particles 4. For example, the flow regulator may include one or more of a static mixer, a mesh, a sieve, a baffle, and an orifice plate.

[0085] The flow conduit 10 may include a tube. The flow conduit 10 may have a cross-sectional shape that matches the cross-sectional shape of the inlet surface of the monolithic article 2. The flow conduit 10 may have a size that matches the size of the inlet surface of the monolithic article 2.

[0086] The spray device 7 may extend into the flow conduit 10. One or more outlets of the spray device 7 may be disposed within the flow conduit 10. For example, the nozzle 25 may be disposed within the upper region of the flow conduit 10. The nozzle 25 may be disposed in alignment with the longitudinal axis of the monolithic article 2.

[0087] The inlet surface of the monolithic article 2 may be disposed 10 to 80 cm, preferably 15 to 20 cm, from the spray device, for example from the nozzle 25 of the spray device 7. Additionally or alternatively, the spray device may be disposed at a distance from the inlet surface of the monolithic article 2 that is up to four times the diameter of the inlet surface of the monolithic article, for example from the nozzle 25 of the spray device 7.

[0088] A vacuum generator 6 is provided for establishing a primary gas flow through the porous structure of the monolithic article 2 during use by applying a reduced pressure to the outlet surface of the monolithic article 2. The vacuum generator 6 may comprise a vacuum cone 40 that defines a funnel engaging the outlet surface of the monolithic article 2. An inflatable lower seal bladder 30 may form a seal between the outlet surface of the monolithic article 2 and the vacuum cone 40. The vacuum generator 6 may comprise a vacuum pump 42 connected to the flow cone by a conduit 43. The vacuum pump 42 may be controlled to control the volumetric flow rate of the primary gas flow.

[0089] The vacuum generator 6 may be provided with a volumetric flow rate sensor. The volumetric flow rate sensor may be an orifice plate 44 combined with a pressure sensor 45 arranged along the conduit 43. The vacuum generator 6 may be provided with a bypass conduit 46 extending up to the intake port 47.

[0090] The device 1 may further comprise a pressure sensor 41 for monitoring the back pressure of the monolithic article 2. A single pressure sensor 41 may be used. The single pressure sensor 41 may be arranged within the vacuum generator 6, preferably within a holder of the vacuum generator or another housing, such as within the vacuum cone 40.

[0091] The controller 9 controls at least the operation of the vacuum generator 6 and the spraying device 7. In FIG. 1, the operational connection between the controller 9 and the remainder of the device 1 is omitted for clarity. However, those skilled in the art will recognize that the necessary connections of any suitable means may be provided. Such connections may be wired or wireless.

[0092] The controller 9 may be configured to control the transfer of the cementitious particles 4 from the reservoir 3 to the spraying device 7 by the transport device 8, independently of controlling the primary gas flow generated by the vacuum generator 6. For example, the controller 9 may control the operation of the injection device 15.

[0093] Controller 9 may be configured to control the spraying of cementitious particles 4 toward the inlet surface of the monolithic article 2, independently of controlling the primary gas flow. The use of the term "independently" herein refers to the ability of controller 9 to control each of the variables of the spraying of cementitious particles 4 and the primary gas flow, individually and without regard to the status of the other variables. For example, controller 9 may establish the primary gas flow without spraying the cementitious particles 4 simultaneously. For example, controller 9 may increase or decrease the spraying rate of the cementitious particles 4 without changing the volumetric flow rate of the primary gas flow. For example, controller 9 may increase or decrease the volumetric flow rate of the primary gas flow without changing the spraying rate of the cementitious particles 4. For example, controller 9 may control the operation of the spraying device 7 independently of controlling the operation of the vacuum pump 42.

[0094] Controller 9 may be configured to operate the vacuum generator 6 to establish a primary gas flow before the cementitious particles 4 are transferred to the spraying device 7 and sprayed toward the inlet surface of the monolithic article 2.

[0095] Controller 9 may be configured to control a secondary gas flow generator, such as compressor 22, independently of the vacuum generator 6. Controller 9 may be configured to operate the vacuum generator 6 to maintain the primary gas flow as a continuous gas flow through the porous structure and, further, to operate a secondary gas flow generator, such as compressor 22, only for a portion of the duration of the primary gas flow.

[0096] Controller 9 may be configured to control the vacuum generator 6 to control the level of vacuum applied to the outlet surface of the monolithic article 2, independently of controlling the transport device 8 and / or the spraying device 7 to control the velocity or mass flow rate of the cementitious particles 4 sprayed toward the inlet surface of the monolithic article 2.

[0097] The controller 9 can be configured to stop the spraying of the cementitious particles 4 towards the inlet surface of the monolithic article 2 when a predetermined back pressure of the monolithic article 2 is reached, as detected by, for example, the pressure sensor 41. The predetermined back pressure may be an absolute back pressure or, alternatively, a relative back pressure.

[0098] Alternatively, the controller 9 can be configured to stop the spraying of the cementitious particles 4 towards the inlet surface of the monolithic article 2 when a predetermined total spraying time is reached.

[0099] The apparatus 1 can be used to coat the monolithic article 2 with the cementitious particles 4 that contain or consist of inorganic particles.

[0100] In some embodiments, the cementitious particles 4 contain or consist of silicates, aluminates, or aluminosilicates. In some particularly preferred embodiments, the cementitious particles 4 contain or consist of calcium silicate, calcium aluminate, calcium aluminosilicate, and / or calcium aluminoferrite.

[0101] In some embodiments, the cementitious particles 4 contain or consist of geopolimer precursor particles. In some particularly preferred embodiments, the geopolimer precursor particles contain or consist of aluminosilicates, pozzolans, calcined clays, metakaolin, fly ash, blast furnace slag, or silica fume.

[0102] The cementitious particles 4 may consist of a single compound or a mixture of compounds. For example, the cementitious particles 4 may include a mixture of two or more of calcium silicate, calcium aluminate, calcium aluminosilicate, calcium aluminoferrite, and the dipolymer precursor particles. In another example, the cementitious particles 4 may include a mixture of any two or more forms of calcium silicate, calcium aluminate, calcium aluminosilicate, and calcium aluminoferrite. For example, the mixture may include two or more of alite, belite, and wollastonite.

[0103] In some embodiments, the cementitious particles 4 have a tapped density of 1 to 3 g / cm 3 , optionally 1.5 to 2.5 g / cm 3 , optionally about 2 g / cm 3 .

[0104] In some embodiments, the cementitious particles 4 have a d50 (by volume) of 5 to 60 microns.

[0105] Here, an example of a method for treating the monolithic article 2 according to the present disclosure will be described with reference to FIG. 2, which shows a flowchart for explaining a method for manufacturing the monolithic article 2 incorporating the use of the apparatus 1. By way of example only, the method will be described with reference to the monolithic article 2 provided with a catalyst coating.

[0106] In step S21, the catalyst slurry is prepared by a method known in the art.

[0107] In step S22, a washcoat is prepared from the catalyst slurry by a method known in the art. The washcoat can be, for example, a hydrocarbon trap, a three-way catalyst (TWC), a NOx absorbent, an oxidation catalyst, a selective catalytic reduction (SCR) catalyst, a lean NOx catalyst, and any combination of two or more thereof.

[0108] In step S23, the washcoat is injected and applied to the bare monolithic article 2 by methods known in the art. For example, the washcoat may be applied to the first surface (e.g., the upper surface) of the monolithic article 2, and the second surface (e.g., the lower surface) opposite the monolithic article 2 may be subjected to at least a partial vacuum to achieve the movement of the washcoat through the porous structure of the monolithic article 2. The monolithic article 2 can be coated in a single injection, where the washcoat can be applied to the monolithic article 2 in a single step while keeping the monolithic article 2 in a single orientation. Alternatively, the monolithic article 2 may be coated in two injections. For example, in the first injection, the monolithic article 2 may assume a first orientation with the first surface uppermost and the second surface lowermost. The coating may be applied to the first surface and coat a portion of the length of the monolithic article 2. Thereafter, the monolithic article 2 can be inverted so that the second surface is uppermost. Next, the coating can be applied to the second surface to coat the portion of the monolithic article 2 that was not coated in the first injection. Advantageously, the two-injection process enables different coatings to be applied to each end of the monolithic article 2.

[0109] In step S24, the monolithic article 2 can be dried.

[0110] In step S25, the monolithic article 2 can be fired by methods known in the art.

[0111] In optional step S26, the back pressure of the monolithic article 2 before treatment can be measured.

[0112] In optional step S27, the monolithic article 2 can be placed in stock to await further processing. Thereafter, in step S28, the monolithic article 2 can be removed from stock and sent for further processing. Alternatively, the monolithic article 2 may be further processed immediately, i.e., by proceeding directly from step S26 to step S29.

[0113] In step S29, the monolithic article 2 is processed to deposit cementitious particles 4 on one or more gas contact surfaces of at least some of the channels of the monolithic article 2 as a dry powder, as will be described in more detail below with reference to FIG. 3.

[0114] In step S30, the cementitious particles 4 are reacted in situ with a liquid or gaseous reagent within the monolithic article 2 to produce a coated monolithic article, as will be described in more detail below.

[0115] In any step S31, the back pressure of the monolithic article 2 after the processing and reaction steps may be measured.

[0116] In step S32, the completed monolithic article 2 may be prepared for shipment to a customer.

[0117] Advantageously, the processing method of the present disclosure does not require high temperature processing such as firing to be performed on the monolithic article 2 after step 29 or 30. Instead, the cementitious particles 4 are reacted chemically in situ to form a cementitious coating.

[0118] FIG. 3 shows a flow diagram illustrating process step S29 of FIG. 2, including the deposition of cementitious particles 4.

[0119] In step S29-1, the monolithic article 2 can be filled into the holder 5. The monolithic article 2 can be held in a stationary position during processing. The monolithic article 2 can be gripped by the holder 5 at the upper end and / or the lower end of the monolithic article 2. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 can be inflated to contact and / or engage the outer surface of the monolithic article 2. The monolithic article 2 can be held in a vertical orientation with the inlet face of the monolithic article 2 at the top. The operation of the holder 5, for example, the inflation of the inflatable upper seal bladder 31 and the inflatable lower seal bladder 30, can be controlled by the controller 9.

[0120] In step S29-2, the vacuum generator 6 can be actuated by the controller 9 to establish a primary gas flow through the monolithic article 2. Preferably, the primary gas flow is established before the cementitious particles 4 are transferred to the spraying device 7 and sprayed towards the inlet face of the monolithic article 2. The level of reduced pressure generated by the vacuum generator 6 can be controlled by the controller 9 independently of the rate of transfer or mass flow rate of the cementitious particles 4 from the reservoir 3 to the spraying device 7. The primary gas flow can have a volumetric flow rate of 10 m 3 / hour to 5,000 m 3 / hour, preferably 400 m 3 / hour to 2,000 m 3 / hour, preferably 600 m 3 / hour to 1000 m 3 / hour.

[0121] In step S29-3, the back pressure of the monolithic article 2 can be measured while the primary gas flow is established but before the secondary gas flow is established. The back pressure can be measured by use of the pressure sensor 41. The back pressure measurement in step S29-3 may be in addition to or in place of the back pressure measurement in step S26. Alternatively, the back pressure measurement in step S26 may be used in place of the back pressure measurement in step S29-3. The back pressure measurement in step S26 and / or the back pressure measurement in step S29-3 can be used by the controller 9 as a measure of the first back pressure of the monolithic article 2 before treatment.

[0122] In step S29-4, the cementitious particles 4 are sprayed as a dry powder onto the inlet face of the monolithic article 2 by the spraying device 7. During spraying of the cementitious particles 4, the cementitious particles 4 can be supplied to the spraying device 7 as a dry powder by the transport device 8.

[0123] Spraying of the cementitious particles 4 towards the inlet face of the monolithic article 2 is preferably controllable by the controller 9 independently of establishing and controlling the primary gas flow.

[0124] During step S29-4, for example, a secondary gas stream supplied by the compressor 22, which is separate from the primary gas stream, can be used to transfer the cementitious particles 4 from the reservoir 3 to the spraying device 7. Preferably, the secondary gas stream is controllable by the controller 9 independently of the primary gas stream. For example, the controller 9 can control the operation of the compressor 22 and / or the valve and / or the nozzle 25 of the spraying device 7 independently of controlling the operation of the vacuum pump 42. The cementitious particles 4 can be sprayed towards the inlet surface of the monolithic article 2 by using the secondary gas stream. The secondary gas stream can include a stream of compressed gas, preferably air.

[0125] During step S29-4, the primary gas stream is preferably maintained as a continuous stream. During step S29-4, the secondary gas stream can be applied as a single burst or a plurality of intermittent bursts.

[0126] In step S29-5, the back pressure of the monolithic article 2 can be monitored. The back pressure can be monitored by using the pressure sensor 41. The controller 9 can be configured to stop the spraying of the cementitious particles 4 towards the inlet surface of the monolithic article 2 when a predetermined back pressure is reached. If the predetermined back pressure has not yet been reached, the controller 9 is configured to return to step S29-4 and continue the spraying of the cementitious particles 4. This feedback can be continuous and does not necessarily involve any interruption in the spraying of the cementitious particles 4, i.e., the controller 9 can continuously monitor the back pressure of the monolithic article 2 while the spraying of the cementitious particles 4 is in progress.

[0127] The predetermined back pressure can be an absolute back pressure. The absolute back pressure can be 20 to 180 mbar at a flow rate of 600 m 3 / hour.

[0128] Alternatively, the predetermined back pressure can be a relative back pressure. For example, the back pressure relative to the first back pressure of the monolithic article 2 before treatment measured in step S26 and / or step S29-3 can be used. The back pressure can be measured as a percentage of the first back pressure. The predetermined back pressure when the spraying of the cementitious particles 4 is stopped can be 105% to 200%, preferably 125% to 150% of the first back pressure.

[0129] Additionally or alternatively, the spraying of the cementitious particles 4 towards the inlet face of the monolithic article 2 can be stopped when a predetermined total spraying time is reached. The predetermined total spraying time can be 1 to 60 seconds, preferably 1 to 20 seconds, preferably about 10 seconds.

[0130] The controller 9 can be configured to stop the spraying of the cementitious particles 4 towards the inlet face of the monolithic article 2 when either the predetermined total spraying time or the predetermined back pressure of the monolithic article 2 is first reached, or when a target mass of the cementitious particles 4 has been sprayed towards the inlet face of the monolithic article.

[0131] In step S29-6, the spraying of the cementitious particles 4 is stopped. For example, this can be achieved by the controller 9 stopping the transfer of the cementitious particles 4 by the transport device 8 and / or by stopping the secondary gas flow of the spraying device 7. Preferably, in step S29-6, the primary gas flow through the porous structure of the monolithic article 2 is maintained for a certain time period after the spraying of the cementitious particles 4 is stopped. The controller 9 can be configured to operate the vacuum generator 6 for a certain time period after the spraying of the cementitious particles 4 is stopped.

[0132] Optionally, in step S29-6, the amount of the cementitious particles 4 delivered towards the inlet face of the monolithic article 2 may be measured. The controller 9 can be configured to determine the amount of the delivered cementitious particles 4, for example, from the signal output from the injection device 15, for example, from the output from a loss-in-weight feeder.

[0133] The method may be configured to deliver a maximum packing of the filter of 10 to 40 g / l, preferably 15 to 30 g / l, preferably about 20 g / l of cementitious particles 4.

[0134] In step S29-7, the primary gas flow through the monolith article 2 is stopped. This can be achieved by the controller 9 stopping the vacuum generator 6, i.e., stopping the vacuum pump 42. Alternatively, this can be achieved by the controller operating the valve of the vacuum generator 6 to redirect the suction through the bypass conduit 46 to draw air through the inlet 47. This can avoid the need to stop the vacuum pump 42 between successive treatments of the monolith article 2, which can result in a faster cycle time.

[0135] In step S29-8, the monolith article 2 may be held within the holder 5 for preparation for step S30 in embodiments where the step of reacting the cementitious particles 4 is carried out on the same apparatus 1, i.e., the coating apparatus 1. Alternatively, in step S29-8, the monolith article 2 may be removed from the holder 5 in embodiments where the step of reacting the cementitious particles 4 is carried out on a separate, optionally dedicated treatment apparatus as discussed below. The removal step may include, for example, contracting the inflatable upper seal bladder 31 and the inflatable lower seal bladder 30. The monolith article 2 can then be removed.

[0136] As described above, in step S30, the cementitious particles 4 are reacted in situ within the monolith article 2 with a liquid or gaseous reagent.

[0137] In some embodiments, the cementitious particles 4 may comprise or consist of hydraulic cementitious particles 4 that are hydrated and reacted. In such embodiments, the liquid or gaseous reagent comprises or consists of water molecules. The water molecules may be in the form of water in the gaseous or liquid state.

[0138] In some embodiments, water molecules in the liquid phase penetrate into the channels of the monolithic article 2. For example, liquid water may be poured onto the monolithic article 2, or the monolithic article 2 may be immersed in a water bath.

[0139] In a more preferred embodiment, the water molecules in the liquid phase may comprise or consist of an aerosolized mist of water that is sprayed into the monolithic article 2. Additionally or alternatively, the aerosolized mist of water may be actively drawn along the channels and / or through the monolithic article 2, for example, by use of a vacuum applied to the outlet surface of the monolithic article 2. The use of an aerosolized mist has been found to be beneficial compared to injection or dip coating as it is less likely to disrupt the coating of the cementitious particles 4 prior to cementing of the cementitious particles 4. This helps to result in an improved integrity of the cementitious coating and an improved coverage of the gas contact surface by the cementitious coating.

[0140] Spraying and / or drawing in the aerosolized mist of water may be carried out using the coating apparatus 1 used to deposit the cementitious particles 4 or by using a separate apparatus. In some preferred embodiments, the monolithic article 2 is held in the holder 5 after completion of the deposition of the cementitious particles 4 and the aerosolized mist is sprayed from a water nozzle disposed adjacent to the nozzle 25. Alternatively, between step S29 and step S30, the nozzle 25 for the dry powder and the nozzle for water may be exchanged manually, semi-automatically or automatically.

[0141] In a particularly preferred embodiment, the step of hydrating the cementitious particles 4 includes exposing the channels of the monolithic article 2 to water molecules in the gas phase, for example, in a humidification chamber. The water molecules in the gas phase may comprise or consist of a humidifying gas, for example, humid air.

[0142] The humidified gas may be actively blown through and / or drawn through the monolithic article 2, for example, using an external pump and / or vacuum, and / or may be applied to one or more surfaces of the monolithic article 2. Alternatively, the humidified gas may diffuse and / or convect within the monolithic article 2.

[0143] The use of water in the gas phase, particularly in the form of humid air, has been found to be particularly beneficial in minimizing interference with the coating of the cementitious particles 4 prior to the cementing of the cementitious particles 4. This helps to result in an improved integrity of the cementitious coating and an improved coverage of the gas contact surface by the cementitious coating.

[0144] The humidified gas may have a relative humidity (RH) of 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95% or more.

[0145] In a particularly preferred embodiment, hydrating the cementitious particles 4 includes a hydrothermal treatment, for example, placing the monolithic article in a hydrothermal oven. For example, the hydrothermal treatment may include subjecting the monolithic article (having the deposited cementitious particles 4) to an ambient temperature of 40°C or more, or 60°C or more, or 80°C or more, or 100°C or more. Additionally or alternatively, the hydrothermal treatment may include subjecting the monolithic article 2 to an ambient temperature of 80°C, or 100°C, or 120°C, or 150°C or less.

[0146] The hydrothermal treatment may include exposing the monolithic article 2 to the humidified gas for 2 to 24 hours, preferably 4 to 12 hours, more preferably 6 to 8 hours.

[0147] In some embodiments, the cementitious particles 4 may include or consist of geopololymer precursor particles. The step of reacting such cementitious particles 4 with a liquid or gaseous reagent may include chemically reacting the geopololymer precursor particles.

[0148] The liquid or gaseous reactant used may contain or consist of an alkali, optionally an alkali polysilicate, and optionally sodium silicate or potassium silicate. The reactant may be provided in liquid or gaseous form using the application modes described above, such as injection, immersion, aerosolized mist, or gas.

Example

[0149] Comparative Example A A silicon carbide wall flow filter substrate (MSC-2SR-HAC 165.0×140.5 mm 300 / 6, 3L type obtained from NGK Insulator, LTD) was filled with Aeroxide® Alu130 (fumed alumina) using the method and apparatus described herein. The diameter of the flow conduit was the same as the inlet face of the filter. A primary gas flow of air at 300 m 3 / hour was passed through the filter using a downstream vortex blower. The back pressure was monitored by a Wika® P30 pressure transmitter placed under the filter. The powder was dispersed into the primary gas flow using a STAR Professional gravity feed spray gun 1.4 mm, part number STA2591100C. The STAR Professional gravity feed spray gun was mounted 100 mm from the inlet face of the filter. The back pressure parameter was used to determine the stopping point of the refractory powder spray. The powder filling amount before firing was 1.5 g / L. After filling was completed, the filter was fired at 500 °C for 1 hour.

[0150] Example B Example B was prepared in the same manner as Comparative Example A, except that calcium silicate powder (d 50 = 6 μm, density = 2800 g / L) was used. The filter was filled with 3 g / L of powder. After powder filling, the filter was not fired. Then, the filter thus prepared was hydrated in air at 80 °C and 95% H 2 O humidity for 6 hours.

[0151] Example C Example C is prepared in the same manner as Example B, except that the filter is filled with 6 g / L of powder.

[0152] Example D Example C is prepared in the same manner as Example B, except that the filter is filled with 9 g / L of powder.

[0153] Example E Example E is prepared in the same way as Example B, except that a mixture of calcium silicates is used. The calcium silicate mixture consists of monocalcium silicate species, dicalcium silicate species and tricalcium silicate species, and calcium is rich at 10 - 22% in the form of CaO, and SiO 2 is rich at about 78% or more. The particle size distribution of the mixture was trimodal with a particle size range of 4 μm to 53 μm. The filter was filled with 8 g / L of the powder mixture. Then, the filter thus prepared was hydrated in air at 80 °C and 95% H 2 O humidity for 6 hours.

[0154] Filtration efficiency The filter samples were tested under the following test conditions using the Cambustion® Diesel Particulate Filter Testing System available from Cambustion Ltd., Cambridge, UK. a) Stabilization - mass flow rate of 250 kg / hour, 50 °C, 5 minutes b) Warm-up - mass flow rate of 250 kg / hour, 240 °C, 5 minutes c) Weighing - remove the filter from the rig and weigh it d) Warm-up - return the filter to the rig; mass flow rate of 250 kg / hour, 240 °C, 5 minutes e) Loading stage - mass flow rate of 250 kg / hour, 240 °C, loading rate: 2 g / hour until a soot loading of 2 g / L is reached; f) Weighing - remove the filter from the rig and weigh it.

[0155] The fuel used during the test is Carcal RF - 06 - 08 B5.

[0156] During the test, the particle counter continuously samples the sample downstream of the filter. Immediately before and immediately after a batch of the filter is tested, an "upstream" test is performed on the rig to enable the particle counter to sample the raw soot generation from the rig. The upstream test is 20 minutes in length and uses the same conditions as the above filling stage. The filtration efficiency is obtained by comparing the average of two upstream tests (before and after the filter test) with the data from the filling stage of the filter test.

[0157] Filtration efficiency data was collected 50 seconds after the start of the test.

[0158] Table 1 compares the filtration efficiencies of a wall-flow filter substrate (MSC-2SR-HAC 165.0X140.5mm 300 / 6, 3L type, no powder filling, obtained from NGK Insulator, LTD), Comparative Example A, Example B, Example C, and Example D.

[0159]

Table 1

[0160] Gas friction test Using a high-pressure air nozzle operating at a flow rate of 425 L / min, at a distance of 0.5 inches from the surface of the filter, the gas friction test was performed using Comparative Example A and Example E by moving it across the entire surface of the filter in a zigzag pattern at 6.7 mm / sec across the entire surface of the filter face. Friction treatment was performed on both the inlet and outlet faces of the filter. After drying in an oven at 115°C for 30 minutes before and after the friction treatment, the sample was weighed. The filtration efficiency of the sample thus obtained was measured and shown in Table 2.

[0161] Water resistance test A sample from Example E was completely submerged in a container of approximately 6 L of deionized water for about 10 seconds, then taken out of the water, and a part was shaken to remove excess water and dried in an oven at 115 °C for about 45 minutes. The filtration efficiency of the obtained sample was measured and shown in Table 2.

[0162] Another sample of Example E was completely submerged in a container of approximately 6 L of deionized water for about 10 seconds, then taken out of the water, and a part was shaken to remove excess water and dried in an oven at 115 °C for about 45 minutes. The same process was repeated 2 more times. The filtration efficiency of the obtained sample was measured and shown in Table 2.

[0163]

Table 2

[0164] Examples F-1 to F-8 Examples F-1 to F-8 were prepared in the same manner as Example E, except that the samples were filled with a powder mixture and then hydrated under various conditions described in Table 3. Table 3 also shows the mass loss of the samples after gas friction.

[0165]

Table 3

[10] The step of hydrating the hydraulic cementitious particles optionally includes exposing the channels to water molecules in the gas phase in a humidification chamber, the method described in [7] - [9].

[11] The water molecules in the gas phase include a humidifying gas, optionally humidified air, the method described in

[10] .

[12] The humidifying gas is actively blown through and / or drawn through the porous monolithic article optionally using an external pump and / or vacuum, the method described in

[11] .

[13] The humidifying gas diffuses and / or convects within the porous monolithic article, the method described in

[11] or

[12] .

[14] The humidifying gas has a relative humidity (RH) of 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95% or more, the method described in

[11] -

[13] .

[15] The step of hydrating the hydraulic cementitious particles optionally includes a hydrothermal treatment in a hydrothermal oven, the method described in [5] -

[14] .

[16] The hydrothermal treatment includes subjecting the porous monolithic article to an ambient temperature of 40°C or higher, or 60°C or higher, or 80°C or higher, or 100°C or higher, the method described in

[15] .

[17] The hydrothermal treatment includes subjecting the porous monolithic article to an ambient temperature of 80°C, or 100°C, or 120°C, or 150°C or lower, the method described in

[15] or

[16] .

[18] The hydrothermal treatment includes exposing the porous monolithic article to the humidifying gas for 2 - 24 hours, optionally 4 - 12 hours, optionally 6 - 8 hours, the method described in

[15] -

[17] .

[19] The cementitious particles include or consist of diopolymer precursor particles, and the step of reacting the cementitious particles with the liquid or gaseous reagent includes chemically reacting the diopolymer precursor particles, the method described in [1] -

[18] .

[20] The geopolymer precursor particles are obtained by the method described in

[19] , including or consisting of aluminosilicate, pozzolan, calcined clay, metakaolin, fly ash, blast furnace slag, or silica fume.

[21] The liquid or gaseous reactant is obtained by the method described in

[19] or

[20] , including or consisting of an alkali, optionally an alkali polysilicate, and optionally sodium silicate or potassium silicate.

[22] The cementitious particles have a tap density of 1 - 3 g / cm 3 , optionally 1.5 - 2.5 g / cm 3 , optionally about 2 g / cm 3 , by the method described in [1] -

[21] .

[23] The cementitious particles have a d50 (by volume) of 5 - 60 microns, by the method described in [1] -

[22] .

[24] The step of reacting the cementitious particles with the liquid or gaseous reagent is carried out before the monolith article is installed in a device for exhaust gas treatment, by the method described in [1] -

[23] .

[25] The step of depositing the cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels includes spraying the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolith article, and optionally, the cementitious particles before spraying are held as dry particulates in a reservoir, by the method described in [1] -

[24] .

[26] The step of depositing the cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels includes drawing the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolith article and along the channels by applying a vacuum to the outlet face of the porous monolith article, by the method described in [1] -

[25] .

[27] The cementitious particles are deposited at a filling level of 3 - 10 g / l, optionally 4.5 - 9 g / l, optionally 4.5 g / l, or 6 g / l, or 9 g / l, by the method described in [1] -

[26] .

[28] The coated monolith article remains uncalcined before its installation in a device for exhaust gas treatment, by the method described in [1] -

[27] .

[29] A coated monolith article obtainable by the method described in [1] -

[28] .

[30] A coated monolithic article for the treatment of exhaust gas, comprising a plurality of channels for the passage of exhaust gas, each channel having a gas contact surface, and at least some of the gas contact surfaces of the channels being at least partially coated by a cement-based coating.

[31] The cement-based coating of the coated monolith according to

[30] , comprising or consisting of calcium silicate hydrate, calcium aluminate hydrate, calcium aluminosilicate hydrate and / or calcium aluminoferrite hydrate.

[32] The cement-based coating of the coated monolith according to

[30] or

[31] , comprising or consisting of a geopolimer.

[33] The coated monolithic article according to

[29] to

[32] , which is one or more of a catalyzed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), and a gasoline particulate filter (GPF).

Claims

1. A method of forming a coated monolith article for the treatment of exhaust gas, comprising: holding a porous monolith article in a coating apparatus, wherein the porous monolith article includes a plurality of channels for the passage of exhaust gas, and each channel has a gas contact surface; depositing cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels; reacting the cementitious particles in situ within the porous monolith article with a liquid or gaseous reagent to provide the coated monolith article; wherein the cementitious particles comprise or consist of hydraulic cementitious particles; and the step of reacting the cementitious particles with the liquid or gaseous reagent includes hydrating the cementitious particles.

2. The method according to claim 1, wherein the monolith article is a catalytic wall flow filter.

3. The method according to claim 1 or 2, wherein the cementitious particles are inorganic particles.

4. The method according to claim 1, wherein the cementitious particles comprise or consist of calcium silicate, calcium aluminate, calcium aluminosilicate and / or calcium aluminoferrite.

5. The method according to claim 1, wherein the step of hydrating the cementitious particles includes permeating water molecules in the liquid phase into the channels.

6. The method according to claim 5, wherein the water molecules in the liquid phase include an aerosolized mist, and permeating the water molecules into the channels includes spraying the aerosolized mist into the porous monolith article.

7. The method according to claim 1, wherein the step of hydrating the cementitious particles includes exposing the channels to water molecules in the gas phase.

8. The method according to claim 7, wherein the water molecules in the gas phase include a humidified gas.

9. The method according to claim 8, wherein the humidified gas diffuses and / or convects within the porous monolith article.

10. The method according to claim 8, wherein the humidified gas has a relative humidity (RH) of 60% or more.

11. The method according to claim 1, wherein the step of hydrating the cementitious particles includes hydrothermal treatment.

12. The hydrothermal treatment comprises subjecting the porous monolith article to an ambient temperature of 40 °C or higher, the method according to claim 11.

13. The hydrothermal treatment comprises subjecting the porous monolith article to an ambient temperature of 150 °C or lower, the method according to claim 11 or 12.

14. The hydrothermal treatment comprises exposing the porous monolith article to a humid gas for 2 to 24 hours, the method according to claim 11.

15. The cementitious particles have a tap density of 1 to 3 g / cm3, the method according to claim 1.

16. The cementitious particles have a d50 (by volume) of 5 to 60 microns, the method according to claim 1.

17. The step of reacting the cementitious particles with the liquid or gaseous reagent is carried out before the monolith article is installed in a device for the treatment of exhaust gas, the method according to claim 1.

18. The step of depositing the cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels comprises spraying the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolith article, the method according to claim 1.

19. The step of depositing the cementitious particles as a dry powder on at least some of the gas contact surfaces of the channels comprises drawing the cementitious particles as a dry particulate aerosol into the inlet face of the porous monolith article and along the channels by applying a vacuum to the outlet face of the porous monolith article, the method according to claim 1.

20. The cementitious particles are deposited at a packing level of 3 to 10 g / l, the method according to claim 1.

21. The coated monolith article remains uncalcined before its installation in a device for the treatment of exhaust gas, the method according to claim 1.

22. A coated monolith article for the treatment of exhaust gas, The coated monolith article comprises a plurality of channels for the passage of exhaust gas, each channel having a gas contact surface, and at least some of the gas contact surfaces of the channels are at least partially coated by a cementitious coating, a coated monolith article. The cement-based coating is a coated monolithic article comprising, or consisting of, calcium silicate hydrate, calcium aluminate hydrate, calcium aluminosilicate hydrate and / or calcium aluminoferrite hydrate.

23. The cement-based coating is the coated monolithic article according to Claim 22, comprising, or consisting of, calcium silicate hydrate.

Images