Method for treating a filter for filtering particulate matter and filter obtained by the method - Patents.com

Abstract

A method is disclosed for treating a filter (2) for filtering particulate matter from an exhaust gas, in which a dry powder (4) is entrained in a primary flow of gas and sprayed toward and through an inlet face of the filter (2) into contact with a porous structure of the filter. The back pressure of the filter (2) is monitored during spraying of the dry powder (4), and spraying of the dry powder (4) is stopped when the back pressure of the filter (2) reaches a required value. The required value may be the absolute back pressure, or a predetermined target back pressure for the filter minus an offset pressure, or equal to the estimated back pressure of the filter.

Description

[Technical field]

[0001] The present disclosure relates to improvements in and to particulate filters for filtering particulate matter from exhaust gases. In particular, the present invention relates to a method of coating a filter comprising a porous substrate having an inlet surface and an outlet surface, the inlet surface being separated from the outlet surface by a porous structure. The filter may be a wall-flow filter. [Background technology]

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

[0003] Diesel particulate filters (DPF) and gasoline particulate filters (GPF) have been fabricated using a variety of materials, including sintered metal, ceramic, or metal fibers, but the most common type in practical mass production is the wall-flow variety, made from porous ceramic materials fabricated in the form of a monolithic array of many small channels running along the length of the body. The alternating channels are plugged at one end, so that the exhaust gases are forced through the porous ceramic channel walls, which prevent most of the particulates from passing through, so that only the filtered gases enter the environment. Ceramic wall-flow filters in commercial production include those made from cordierite, various forms of silicon carbide, and aluminum titanate. The actual shape and dimensions of the practical filters on a vehicle, as well as their properties, such as the thickness of the channel walls and their porosity, depend on the application involved. The average size of the pores in the filter channel walls of a ceramic wall-flow filter through which the gases pass is typically in the range of 5 to 50 μm, usually about 20 μm. In sharp contrast, most diesel exhaust particulate matter from modern passenger car high speed diesel engines is very small in size, for example between 10 and 200 nm.

[0004] Some PM may be retained within the pore structure in the filter wall, which in some applications may gradually build up until the pores are bridged by a network of PM, which then readily leads to the formation of a cake of particulates on the inner walls of the filter channels. The particulate cake is an excellent filter medium, and its presence provides very high filtration efficiency. In some applications, the soot is continuously burned on the filter as it is deposited, which prevents the particulate cake from building up on the filter. In some filters, such as light-duty diesel particulate filters, it is necessary periodically to remove the trapped PM from the filter to prevent excessive backpressure buildup, which can be detrimental to engine performance and reduce fuel economy. In diesel applications, the retained PM is removed from the filter by burning it in air in a process during which the amount of available air and the amount of excess fuel used to achieve the high temperatures required to ignite the retained PM are very carefully controlled. Towards the end of this process, usually called regeneration, the removal of the last remaining particles in the filter can significantly reduce the filtration efficiency and lead to a burst release of many small particles into the environment. Thus, filters may have low filtration efficiency when they are first used, after each subsequent regeneration event, and during the latter part of each regeneration process.

[0005] 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 the filter becomes loaded with soot.

[0006] Liu, X., Szente, J., Pakko, J., Lambert, C. et al., "Using Artificial Ash to Improve GPF Performance at Zero Mileage," SAE Technical Paper 2019-01-0974, 2019, doi:10.4271 / 2019-01-0974, describes a process for loading submicron alumina particles generated by an atomizer onto a bare filter substrate to create an "artificial ash" coating for reducing soot emissions under cold start conditions. The process consists of generating aerosol particles by atomizing a liquid suspension with compressed air, drying the resulting ash-containing droplets by running them through an oven, and loading the dried ash particles into a filter via their capture by filtration. The process utilizes a high capacity atomizer (model PLG-2100 (PALAS, Germany)) to provide a flow rate of 100 l / min for a full size brick. Filter loading is monitored by the pressure drop across the filter and the PM concentrations before and after the filter recorded by a DustTrak aerosol monitor (TSI Inc, Minnesota, USA). Although the process has shown a reduction in soot emissions under cold start conditions, it is limited to materials that can be spray dried, requires an atomizer, drying oven and aerosol monitor, and artificial ash loading conditions may be constrained by the conditions necessary to achieve complete drying of the liquid aerosol before it reaches the filter substrate.

[0007] WO 2011 / 151711 describes a method for 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 comprising pores of a first average pore size. The inlet surface comprises a crosslinked network comprising 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 comprising the refractory material in dry powder form. Although the process has shown a reduction in PM emissions of the filter when first used and after each subsequent regeneration event, it would be desirable to provide an improved process, particularly with respect to controllability of the parameters of the filters produced.

[0008] US Patent Application Publication No. 2019 / 0048771 describes an engine exhaust particulate filter including a porous substrate having inert nanoparticles thereon in a concentration ranging from 0.01 g / L to 60 g / L of filter volume of the substrate, a portion of the nanoparticles configured and arranged to form a regeneration resistant porous structure configured to capture particulates from the exhaust gas stream. The filter is intended to provide an improvement in the zero kinetic efficiency of particulate filters, however, it would be desirable to provide an improved process, particularly to improve process controllability and flexibility.

[0009] The Applicant has discovered that filters having improved filtering efficiency during the initial life of the filter when first used and / or during and immediately after regeneration and / or when the filter has accumulated soot (as fully described in GB Patent No. 1911704, filed 15 August 2019, the entirety of which is incorporated herein by reference) may be obtained by a treatment method comprising the steps of: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device such that the dry powder is entrained in the primary gas flow and passes through the inlet face of the filter into contact with the porous structure.

[0010] In GB 1911704 the applicant describes how the dry powder may preferably comprise 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 aluminium oxide having a tap density of 0.05 g / l and a d50 of 5.97 micrometers is described.

[0011] While this treatment method has been found to produce filters with improved filtration efficiency characteristics, it remains desirable to further improve the treatment of such filters, and in particular to improve the durability of the treated filters.

[0012] As a result, the applicant has discovered that the durability of treated filters (as fully described in GB Patent No. 2002483, filed February 21, 2020, which is incorporated herein by reference in its entirety) may be improved by using a dry powder in the spray process that includes or consists of a metal compound to form a metal oxide by thermal decomposition.

[0013] In GB 2002483 the applicant explains that the use of metal compounds which pyrolyse to metal oxides as dry powders can provide substantial improvements in the durability of the treated filters compared to treatments with metal oxides including, for example, fumed aluminium oxide, and in particular in the ability of the dry powder to remain adhered to the porous structure and not become detached from the porous structure during subsequent operation of the filter.

[0014] Surprisingly, applicants have discovered that the improved adhesion of these dry powders can be achieved without the presence of any additional binders or adhesion promoters, or the need for any high temperature sintering of the filter. In particular, it has been surprisingly found that the use of such dry powders can result in good adhesion while maintaining high filtration efficiency and with acceptable cold flow back pressure.

[0015] Although the processing methods of GB 1911704 and GB 2002483 have been found to be effective in producing improved filters, improvements in the methods are still desirable. Summary of the Invention

[0016] In a first aspect, the present disclosure provides a method for treating a filter for filtering particulate matter from an exhaust gas, the method comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing spraying of the dry powder towards the inlet face of the filter when: ρ BP ≧ρ target -ρ offset During the ceremony, ρ BP is the back pressure of the filter, ρ target is the desired target backpressure for the filter; ρ offset is the preselected offset pressure.

[0017] Beneficially, the method may be able to more closely match the generated filter backpressure to a predetermined target backpressure, and the method may help to limit and reduce the occurrence of overshooting the target backpressure.

[0018] The desired backpressure for the filter, ρ target may be the absolute backpressure of the filter. For example, a predetermined target backpressure for the filter, ρ target may be a target backpressure between 20 and 180 mbar. Alternatively, a predetermined target backpressure for the filter, ρ target may be the relative backpressure of the filter. For example, a predetermined target backpressure for the filter, ρ target may be the backpressure relative to the initial backpressure on the filter prior to spraying of the dry powder. For example, a predetermined target backpressure on the filter, ρ target may be between 105% and 200%, optionally between 125% and 150%, of the initial backpressure of the filter.

[0019] In step f), ρ BP ≧ρ target -ρ offset is the minimum period, t minWhen this is true over the entire range, the spray of dry powder toward the inlet face of the filter can be stopped, where t min 0.1 seconds or more, optionally 0.5 seconds or more, optionally 1.0 seconds or more. In this manner, the method can be configured to avoid cessation of spraying due to, for example, short-term fluctuations in backpressure readings due to system noise and which may not reflect the true backpressure of the filter.

[0020] ρ offset may be, for example, 1 to 10 mbar, optionally 2 to 5 mbar, optionally 3 to 5 mbar. For example, such ρ offset is ρ target It can be used when the pressure is between 20 and 180 mbar.

[0021] In step f), the backpressure of the filter may be continuously monitored at least during step e). Optionally, the backpressure is monitored every 1 sample.s -1 Above, 5 samples can be selected. -1 Above, 10 samples.s -1 The back pressure can be continuously monitored by measuring it at a sample rate of 100 s or more.

[0022] The method may further include, in step c), monitoring the backpressure of the filter and passing the primary gas flow through the porous structure of the filter until the backpressure of the filter is stable before commencing step d). In this manner, a more accurate and reliable measurement of the initial backpressure of the filter may be obtained. In addition, such a stable backpressure may also be indicative of obtaining a stable flow rate of the primary gas flow through the porous structure of the filter. The predetermined target backpressure for the filter, ρ target may be for the stable backpressure monitored in step c). For example, a predetermined target backpressure for the filter, ρ target may be between 105% and 200%, optionally between 125% and 150%, of the stable backpressure monitored in step c).

[0023] The method may further include monitoring the filter back pressure and maintaining a primary gas flow through the porous structure of the filter after the spraying of the dry powder has stopped until the filter back pressure has stabilized, which may improve the ability to determine that an accurate cold flow back pressure (CFBP) for the filter has been obtained.

[0024] The back pressure of the filter is i) the primary gas flow rate is within 0.5% of the specified flow rate; ii) The first derivative of the primary gas flow rate is within ±0.15 m 3 time -1 .s -1 is as follows: iii) The first derivative of the filter back pressure is ±1.5 mbar.s -1 It can be considered stable when:

[0025] Back pressure, ρ BP may be the absolute back pressure measured relative to atmospheric pressure.

[0026] The method may use a coating apparatus to perform at least steps a) through f), and may further include applying a predetermined target backpressure, ρ, to the filter. target teeth, selecting a desired back pressure on the filter as measured by a test device different from the coating device; - establishing a calibration map for converting the back pressure measured on the test apparatus to the back pressure measured on the coating apparatus; - Convert the desired backpressure using a calibration map to a given target backpressure, ρ target It can be calculated by establishing

[0027] Beneficially, using a calibration map in this manner may allow the final backpressure of the filter to be targeted at a value as measured on a test apparatus during the coating process of the filter, without having to use that test apparatus. This may be advantageous since the backpressure of a filter is typically measured by purchasers of filters on their own test apparatus to ensure that the filter meets their requirements. For example, a purchaser may test a filter on a test apparatus such as a Superflow Flow Bench 1050 available from Superflow of Sussex, WI, USA. A requirement may be that the filter has a backpressure of, for example, 65 mbar±5 mbar when tested on the Superflow Flow Bench 1050. Use of a calibration map may allow a predetermined target backpressure ρ as measured by the coating apparatus to achieve the required backpressure on the Superflow Flow Bench 1050. target may be allowed to be selected.

[0028] In a second aspect, the present disclosure provides a method for treating a filter for filtering particulate matter from an exhaust gas, the method comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a reduced pressure to the outlet face of the filter while monitoring the back pressure of the filter, and passing the primary gas flow through the porous structure of the filter until the back pressure of the filter stabilizes; d) after establishing a stable back pressure on the filter, transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device, such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter, and contacts the porous structure, while monitoring the back pressure of the filter; f) stopping the spray of dry powder towards the inlet face of the filter; g) continuing to monitor the filter back pressure while maintaining the primary gas flow through the porous structure of the filter after the spraying of the dry powder has been stopped until the filter back pressure has stabilized.

[0029] The filter back pressure is the first derivative of the primary gas flow rate, ±Xm 3 time -1 .s -1 where X=0-0.30, optionally X=0.10-0.20, X=0.15, can be considered stable.

[0030] Additionally or alternatively, the filter backpressure may be expressed as a function of the first derivative of the filter backpressure ±Ymbar.s -1 and can be considered stable when Y=0.5-3.0, optionally Y=1.0-2.0, optionally Y=1.5.

[0031] Additionally or alternatively, the filter backpressure may be considered stable when the primary gas flow rate is within Z% of a predetermined flow rate, Z=1.5, optionally Z=1.0, optionally Z=0.5.

[0032] The backpressure may be an absolute backpressure measured relative to atmospheric pressure. The backpressure of the filter may be measured using a pressure sensor, optionally a single pressure sensor located in a filter holder or other housing fluidly connected to the outlet face of the filter.

[0033] In a third aspect, the present disclosure provides a method for treating a filter for filtering particulate matter from an exhaust gas, the method comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing spraying of the dry powder towards the inlet face of the filter when: ρ est ≧ρ target During the ceremony, ρ target is the desired target backpressure for the filter; ρ est is the estimated final back pressure of the filter, ρ est is calculated by extrapolation of the measured backpressure data for the filter obtained during step f).

[0034] Beneficially, the method may enable the backpressure of the generated filter to more closely match the predetermined target backpressure. The method may help to limit and reduce the occurrence of overshooting the target backpressure. In particular, the method may enable a better matching of the backpressure to the predetermined target backpressure for filters with different loading characteristics. For example, different filters (even within one batch of filters) may exhibit different rates of change in backpressure when loaded with dry powder. The method of the third aspect may help to adapt to different loading characteristics by using an estimated final backpressure parameter, which may be calculated for each individual filter. As a result, the method may enable the generation of filters with less change in the CFBP of the filter.

[0035] The estimated final back pressure of the filter, ρ est is the measured back pressure data T s can be calculated by extrapolating forward in time over T seconds. s is the settling time.

[0036] The method may be performed on a coating apparatus having a settling time, T s can be a coating equipment dependent variable and is preferably filter independent.

[0037] For example, the settling time of a coating apparatus may be affected by the design of the coating apparatus, such as valve closing times, powder spray rate, size of the flow conduit, any lag in pressure measurement by the pressure sensor, etc. Therefore, the settling time, T s The parameters of can be selected to characterize the performance of the coating apparatus. Settling time, T s can be theoretically calculated for the coating apparatus. Alternatively, the settling time, T s may be determined empirically for a coating apparatus by testing a sample filter.

[0038] The estimated final back pressure of the filter, ρ estcan be calculated by curve fitting the measured backpressure data and extrapolating the fitted curve forward in time.

[0039] Any of the above aspects may also additionally include one or more of the following features.

[0040] The dry powder may, in some embodiments, include or consist of one or more refractory powders, preferably including one or more fumed refractory powders, and / or one or more aerogels. The one or more fumed refractory powders may be produced by an exothermic process, such as flame pyrolysis. The one or more fumed refractory powders may include one or more of fumed alumina, fumed silica, fumed titania, other fumed metal oxides, and fumed mixed oxides. The one or more aerogels may include one or more of silica aerogels, alumina aerogels, carbon aerogels, titania aerogels, zirconia aerogels, ceria aerogels, metal oxide aerogels, and mixed oxide aerogels.

[0041] In these embodiments, the method further comprises providing a maximum loading of the filter of less than 10 g / l dry powder, optionally less than 5 g / l dry powder, optionally less than 2 g / l dry powder. 3 less than, optionally 0.08 g / cm 3 less than, optionally 0.07 g / cm 3 less than, optionally 0.06 g / cm 3 less than, optionally, 0.05 g / cm 3 The dry powder may have a d50 (by volume) of less than 25 micrometers, preferably less than 20 micrometers, more preferably less than 10 micrometers.

[0042] In some other examples, the dry powder may include or consist of a metal compound for forming a metal oxide by pyrolysis. The dry powder may consist of a single metal compound, a mixture, blend, or sequential doses of two or more metal compounds. The or each metal compound may contain one or more metal cations. When multiple metal cations are present, they may be the same metal or different metals. The metal compound may include or consist of a metal hydroxide, a metal phosphate, a metal carbonate, a metal sulfate, a metal perchlorate, a metal iodide, a metal oxalate, a metal acetate, a metal chlorate, or a mixture thereof. The metal of the metal compound may include or consist of one or more of magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper, or gallium. The dry powder may additionally include a metal oxide or a mixed metal oxide. Preferably, the dry powder comprises 90% or more by weight of a metal compound for forming a metal oxide by pyrolysis and 10% or less by weight of a metal oxide or mixed metal oxide. More preferably, the dry powder comprises 95% or more by weight of a metal compound for forming a metal oxide by pyrolysis and 5% or less by weight of a metal oxide or mixed metal oxide. Optionally, the dry powder comprises 99% or more by weight of a metal compound for forming a metal oxide by pyrolysis and 1% or less by weight of a metal oxide or mixed metal oxide. The metal of the metal oxide or mixed metal oxide may comprise or consist of one or more of aluminum, magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper, or gallium. Preferably, the dry powder comprises or consists of a metal hydroxide, a metal phosphate, a metal carbonate, or a mixture thereof. The metal hydroxide may be selected from the group consisting of magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. The metal phosphate may be selected from the group consisting of magnesium phosphate, calcium phosphate, strontium phosphate, and barium phosphate.The metal carbonate may be selected from the group consisting of magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate.

[0043] In these examples, the method may further include providing a maximum filter loading of 10-40 g / l, optionally 15-30 g / l, optionally about 20 g / l. The dry powder may be 1-3 g / cm. 3 , optionally 1.5 to 2.5 g / cm 3 , optionally about 2 g / cm 3 The dry powder may have a tap density of less than 10 micrometers, optionally less than 5 micrometers, optionally about 2 micrometers. Surprisingly, Applicants have discovered that the use of metal hydroxide, metal phosphate, and / or metal carbonate powders having such relatively small particle sizes can still produce an effective wall filtration layer on the walls of the porous substrate.

[0044] The dry powder may consist of a single powder type or a mixture of powder types.

[0045] The method may further comprise the step of calcining the filter. Calcination of the filter may be carried out at a temperature selected to produce pyrolysis of the dry powder in those instances where the dry powder comprises or consists of a metal compound for forming a metal oxide by pyrolysis. Preferably, at least a majority of such dry powder, more preferably all or substantially all of the dry powder, may be pyrolyzed during calcination. However, it will be appreciated that a residual amount of undecomposed dry powder may remain after calcination.

[0046] The firing temperature may be selected to be at least 150°C, optionally at least 250°C, optionally at least 500°C. In some embodiments, the firing temperature is preferably 550°C or less. However, in other embodiments, the firing temperature may be selected to be greater than 550°C. The firing temperature may be selected to be up to 900°C, optionally up to 1150°C. In one example, the firing temperature may be selected to be between 300°C and 500°C. In another example, the firing temperature may be selected to be about 520°C. In another example, the firing temperature may be selected to be about 580°C. In another example, the firing temperature may be selected to be about 900°C.

[0047] The baking may be carried out for 30 to 90 minutes, optionally 30 to 60 minutes. In one example, the duration is about 35 minutes. In another example, the duration is about 60 minutes. In any such baking, the residence time of each filter is preferably 1 to 15 minutes, preferably 5 to 10 minutes.

[0048] By "calcination" herein is meant a process in which a filter is typically, but not exclusively, combusted in air at a desired temperature for a desired length of time. However, it will be understood that, in general, even with microwave assistance, it is not possible to instantly raise the filter temperature to the indicated temperature. Instead, those skilled in the art will understand that in a typical calcination process, the filter is fed on a belt into a dynamic furnace, or a pallet of filters is placed in a static furnace, and in either case, the furnace or furnace temperature is raised to the desired temperature, and in the case of a furnace, this may be achieved by a zone in the furnace that increases the temperature to the desired temperature. That is, it may take time to raise the filter to the desired temperature. Thus, the calcination temperature defined herein refers to the preferred peak temperature at which the filter is calcined. The filter may eventually reach and be held at the peak temperature for a relatively short period of the total calcination cycle (the so-called "dwell time"). What the applicant's inventors have found is that the duration of the dwell time is important to achieve the desired adhesion of the powder both to itself and in particular to the porous structure of the filter. Thus, "calcination" herein refers to the entire period or cycle of heating, residence time, and cooling of the combustion process. Thus, the entire calcination process, including heating, residence time, and cooling, may be 90 minutes long, but the residence time may only be 1-15 minutes within that 90 minutes.

[0049] Without wishing to be bound by theory, it is believed that applying a metal hydroxide, metal phosphate, metal carbonate, or mixtures thereof as a dry powder followed by calcination can produce a particularly effective porous layer, including at least a portion of the dry powder being retained on the walls of the porous substrate. In particular, it is believed that the decomposition of the metal hydroxide, metal phosphate, and / or metal carbonate to metal oxide produces a cementitious effect both between particles of the dry powder and between the dry powder and the porous substrate.

[0050] The calcined vehicle exhaust filter may have a filtering efficiency of greater than 90%, preferably greater than 95%, preferably greater than 98%, preferably greater than 99% at a soot loading of 0.02 g / l. 3 The flow rate may range from 20 to 180 mbar.

[0051] The calcined vehicle exhaust filter may exhibit a substantially linear load-backpressure response for soot loadings greater than 0.1 g / l, and preferably for soot loadings greater than 0.05 g / l.

[0052] The method may further include coating the filter with a washcoat, preferably a catalytic washcoat.

[0053] A secondary gas flow, separate from the primary gas flow, may be used to transport the dry powder from the reservoir to the spray device, and optionally, the secondary gas flow is controllable independently of the primary gas flow.

[0054] The secondary gas stream may comprise a stream of compressed gas, preferably air.

[0055] The secondary gas flow may be applied as a single burst or multiple intermittent bursts.

[0056] A vacuum generator can be used to establish a primary gas flow through the porous structure of the filter, and the level of pressure reduction generated by the vacuum generator can be controllable independently of the rate or mass flow rate of transfer of the dry powder from the reservoir to the spray device.

[0057] The primary gas flow is 10 m 3 / hour~5,000m 3 / h, preferably 400m 3 / hour~2,000m 3 / h, preferably 600m 3 / hour~1000m 3 / hr volumetric flow rate.

[0058] A pressure sensor, preferably a single pressure sensor, can be used to monitor the backpressure. The pressure sensor, preferably a single pressure sensor, can be disposed in a filter holder or other housing fluidly connected to the outlet face of the filter. The same pressure sensor, preferably the same single pressure sensor, can be used to monitor the backpressure of the filter during at least steps c) and f).

[0059] In step e), the dry powder may be sprayed from one or more outlets of the spray device.

[0060] The one or more outlets of the spray device may comprise an opening size of 1-10 mm, optionally 0.5-5.0 mm, optionally 1.0-2.5 mm, optionally 1.0-2.0 mm.

[0061] The dry powder may be sprayed from one or more fixed outlets of the spray device. Alternatively, the dry powder may be sprayed from one or more movable outlets of the spray device, preferably from one or more oscillating outlets.

[0062] The method may further comprise channelling the dry powder from the spray device to the inlet face of the filter in a flow conduit in step e). The flow conduit may provide an unobstructed flow path between the spray device and the inlet face of the filter. Alternatively, the flow conduit may comprise a flow regulator interposed between the spray device and the inlet face of the filter, the flow regulator acting to promote dispersion of the dry powder within the gas flow. The flow regulator may comprise one or more of a static mixer, a mesh, a sieve, a baffle and an orifice plate.

[0063] The inlet face of the filter may be located more than 10 cm, optionally more than 20 cm, from the nozzle outlet of the spray nozzle. Particular advantages may be found when the inlet face of the filter is located more than 75 cm, optionally more than 100 cm, from the nozzle outlet of the spray nozzle. Advantageously, such spacing increases the percentage area of ​​the inlet face of the filter that receives dry powder, leading to improved uniformity of dry powder application to the filter. Additionally or alternatively, the outlet nozzle of the spray nozzle may be located at a distance of up to 4 times the diameter of the inlet face of the filter from the inlet face of the filter.

[0064] The method may further include injecting the dry powder from the reservoir in step d), which may include injecting by one or more of weight, volume, number of particles, and time.

[0065] The method may include gravimetrically delivering the dry powder to the injection device.

[0066] The injecting may use a loss-in-weight feeder.

[0067] In step a), the dry powder may be contained in one or more hoppers.

[0068] In step b), the filter may be placed in the holder in a vertical orientation with the inlet face uppermost. In step d), the spray device may be placed vertically above the inlet face, and preferably the spray direction of the spray device may be coaxial with the longitudinal axis of the filter, and preferably the spray direction and the longitudinal axis are coincident.

[0069] The porous substrate can be a wall-flow filter.

[0070] The present disclosure extends to filters obtainable by any of the methods described above.

[0071] The filter may be a catalysed soot filter (CSF), a selective catalytic reduction filter (SCRF), a lean NOx trap filter (LNTF), or a gasoline particulate filter (GPF).

[0072] As used herein, the term "filter" refers to a porous substrate having a porous structure suitable for filtering particulate matter from exhaust gases. The porous substrate may be formed, for example, from sintered metal, ceramic, or metal fibers. The filter may be of the wall-flow variety made from a porous material, for example, a ceramic fabricated in the form of a monolithic array of many small channels running along the length of the body. For example, the filter may be formed from cordierite, various forms of silicon carbide, or aluminum titanate.

[0073] The filter may be a "bare" filter, or alternatively may have built-in catalytic functionality, such as oxidation, NOx trap, or selective catalytic reduction activity. The porous substrate may include a composition (known as a washcoat) that coats the porous structure of the filter. The washcoat may be a catalytic washcoat. The catalytic washcoat may include a catalyst selected from the group consisting of a hydrocarbon trap, a three-way catalyst (TWC), a NOx absorbent, an oxidation catalyst, a selective catalytic reduction (SCR) catalyst, a lean NOx catalyst, and any combination of two or more thereof. The catalysts, such as the TWC, the NOx absorbent, the oxidation catalyst, the hydrocarbon trap, and the lean NOx catalyst, may contain one or more platinum group metals, particularly those selected from the group consisting of platinum, palladium, and rhodium.

[0074] As a result, the coated filter may be, for example, a catalyzed 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 including a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC)).

[0075] The shape and dimensions of the filter, such as channel wall thickness and its porosity, and other properties, 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 an internal combustion engine in the form of a diesel or gasoline engine.

[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 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 dry 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] As used herein, the term "d50 (by volume)" refers to the d50 (by volume) measurement measured by a Malvern Mastersizer® 3000 equipped 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. Refractive index and absorptivity parameters are set according to the instructions provided in the Malvern Mastersizer® 3000 user manual.

[0081] As used herein, the term "vacuum generator" refers to a device or combination of devices that function to generate a pressure drop. Non-limiting examples of suitable devices include vacuum generators that operate on the Venturi principle, vacuum pumps, such as rotary vane and liquid ring vacuum pumps, and vortex blowers.

[0082] As used herein, the term "pressure sensor" refers to a device or combination of devices that function to measure absolute and / or relative pressure. Non-limiting examples of suitable devices include pressure transducers, which may be diaphragm-type pressure transducers. For example, a Wika® P30 pressure transmitter available from WIKA Alexander Wiegand SE & Co. KG (Klingenberg, Germany) may be used.

[0083] As used herein, the term "controller" refers to functionality that may include hardware and / or software. A controller may comprise a control unit or may be a computer program running on a dedicated or shared computing resource. A controller may comprise a single unit or may be composed of multiple operatively connected sub-units. A controller may be located on one processing resource or distributed across spatially separated processing resources. A controller may include a microcontroller, one or more processors (such as one or more microprocessors), memory, configurable logic, firmware, etc.

[0084] As used herein, ranges and amounts may be expressed as "about" a particular value or range. About also includes the exact amount. For example, "about 2 micrometers" also means "about 2 micrometers" and "2 micrometers." In general, the term "about" includes amounts that are expected within experimental error. The term "about" may include values ​​that are within 5% to more than 5% of the value provided. For example, "about 2 micrometers" means "1.9 micrometers to 2.1 micrometers."

[0085] As used herein, the expression "consisting of" a dry powder means a dry powder that consists essentially of only the specified components, excluding unavoidable impurities that are commonly encountered as recognized by those of skill in the art. [Brief description of the drawings]

[0086] Aspects and embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings. [Figure 1] 1 is a schematic diagram of an apparatus for treating a filter for filtering particulate matter from an exhaust gas according to the present disclosure; [Diagram 2] FIG. 2 is a flow diagram illustrating a method for manufacturing a filter according to the present disclosure that incorporates a method for processing the filter using the apparatus of FIG. 1. [Diagram 3] 2 is a flow diagram illustrating a method for treating a filter for filtering particulate matter from an exhaust gas using the apparatus of FIG. 1. [Figure 4] 1 is a graph showing backpressure versus time for two filters treated with different mass loadings of dry powder. [Diagram 5] 1 is a graph showing backpressure versus time for two filters subjected to two different regimes for aerosolizing dry powder. [Figure 6] 1 is a graph showing backpressure versus time for two filters subjected to two different regimes for aerosolizing dry powder. [Figure 7] 1 shows a calibration map comparing the cold flow back pressure (CFBP) in the coating and test fixtures. [Figure 8] 13 shows further calibration maps comparing CFBP on the coating and test fixtures. [Figure 9] 13 shows further calibration maps comparing CFBP on the coating and test fixtures. [Figure 10] 1 shows a graph showing backpressure versus time for eight filters. [Figure 11] 11 shows a graph showing backpressure versus time for two of the eight filters of FIG. 10. [Figure 12] 11 is a graph showing the backpressure for one of the eight filters of FIG. 10 subjected to two different regimes for aerosolizing dry powder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0087] Those skilled in the art will recognize that 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.

[0088] An example of an apparatus for carrying out the method of the present disclosure will now be described with reference to Figure 1, which shows a schematic diagram of an apparatus 1 for treating a filter 2 for filtering particulate matter from exhaust gases. The filter 2 is of the type 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.

[0089] The apparatus 1 comprises a reservoir 3 for containing a dry powder 4. A filter holder 5 is provided for holding the filter 2. A vacuum generator 6 is provided for establishing a primary gas flow through the porous structure of the filter 2 in use by applying a pressure drop to the outlet face of the filter 2. A transport device 8 is provided for transporting the dry powder 4 from the reservoir 3 to a spraying device 7. The spraying device 7 is provided for receiving the dry powder 4 from the transport device 8 and spraying the dry powder 4 towards the inlet face of the filter 2. A controller 9 is provided configured to control the operation of the apparatus 1.

[0090] The reservoir 3 can receive the dry powder 4 from a dry powder inlet 11. The dry powder inlet 11 can be the output of an upstream bulk supply of dry powder. For example, the dry powder inlet 11 can be a conduit connected upstream of a further reservoir of dry powder 4. The dry powder inlet 11 can represent a manual, semi-automatic or automatic refill of the reservoir 3 through a lid or opening of the reservoir 3.

[0091] The reservoir 3 may comprise one or more hoppers. The reservoir 3 may 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 so as to receive the dry powder 4 output from the first hopper 12. The one or more hoppers may be provided in separate housings. Alternatively, the one or more hoppers may be provided in a single housing. The one or more hoppers may comprise one or more chambers of a single container.

[0092] The reservoir 3 may include an injection device 15. The injection device 15 may inject the dry powder 4 by one or more of weight, volume, particle number, time. The injection device 15 may be located at or near the outlet of the reservoir 3. The injection device 15 may be located at or near the outlet of one or more hoppers of the reservoir 3. The injection device may be located at or near the outlet of the first hopper 12.

[0093] The injection device 15 may be gravimetrically fed with dry powder 4 from a reservoir 3 .

[0094] The injection device 15 can be a loss-in-weight feeder. The injection device 15 can be a volumetric feeder with an auger or thread configuration. Non-limiting examples of suitable injection devices include the Coperion® K-Tron Type K2-ML-T35 Gravimetric Twin Screw Feeder available from Coperion GmbH, Stuttgart, Germany, and the All-Fill® Series S1 Micro-Fill and All-Fill® Series 10 gravimetric or volumetric auger fillers available from All-Fill International Ltd, Sandy, UK.

[0095] The transport device 8 transports the dry powder 4 from the reservoir 3 to the spraying device 7. The transport device 8 may gravimetrically or volumetrically deliver the dry powder 4 towards the spraying device 7 at least part way.

[0096] The transport device 8 may comprise one or more components. The transport device 8 may comprise one or more conduits, such as passageways, pipes, hoses, and the like.

[0097] If the reservoir 3 comprises two or more hoppers, the transport device 8 may transport the dry powder 4 between the hoppers. The transport device 8 may feed the dry powder 4 gravimetrically or volumetrically 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 dry powder 4 may be fed gravimetrically along the first conduit 14.

[0098] The transport device 8 may comprise a second conduit 16 extending from the second hopper 13 to the spray device 7 .

[0099] The spraying device 7 is provided for receiving the dry powder 4 from the transport device 8 and spraying the dry powder 4 towards the inlet face of the filter 2. The spraying device 7 may comprise a secondary gas flow generator for generating a secondary gas flow that may be used to spray the dry powder 4 towards the inlet face of the filter 2.

[0100] The spray device 7 may further comprise one or more outlets for discharging the dry powder 4 towards the inlet face of the filter 2. The one or more outlets of the spray device may comprise an aperture size of 0.5-10 mm. The aperture may be circular, partially circular, or slot-shaped. The one or more outlets may be one or more fixed outlets. Alternatively, the one or more outlets may be one or more movable outlets, for example one or more swingable outlets.

[0101] The one or more outlets may be provided in one or more nozzles, each of which may include one or more spray outlets. In the illustrated example of Figure 1, a single nozzle 25 is provided with multiple spray outlets.

[0102] The secondary gas flow generator may comprise a compressed gas generator. In the illustrated example of Fig. 1, the secondary gas flow generator comprises a compressed air generator which may comprise a compressor 22. The compressor 22 may receive air from an air inlet 21 and supply compressed air via a supply line 23 to one or more outlets of the spraying device 7. A return line 24 may be provided. Valves and controls necessary for operation may be provided as known to those skilled in the art.

[0103] An interconnection may be provided between the transport device 8 and the spray device 7, in which the dry powder 4 is transported from the transport device 8 to the spray device 7. The interconnection may be provided at or near one or more outlets of the spray device 7. In one example, the interconnection may be provided at the nozzle 25. Alternatively, the interconnection may be provided at or near the reservoir 3, for example at 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 spray device 7 may be fluidly connected to the second conduit 16 at or near the outlet of the second hopper 13 to fluidize the dry powder 4 and assist in the transport of the dry powder 4 along at least a portion of the second conduit 16. In another example, the dry powder 4 may be fed by gravity along the second conduit 16. The flow of dry powder 4 down the second conduit 16 may be assisted by a suction force that draws the dry powder 4 towards the outlet of the second conduit 16. For example, the spray nozzle 25 may generate a suction force to assist in drawing the dry powder 4 along the second conduit 16 and through the spray nozzle 25. For example, the spray nozzle 25 may use a secondary gas flow from the feed line 23 to create a suction force in the powder flow conduit of the spray nozzle 25 by a Venturi device or similar apparatus.

[0104] In one example, the spray 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.

[0105] The filter holder 5 may function to maintain the filter 2 in a stationary position during processing. The filter holder 5 may grip the upper and / or lower ends of the filter 2. The filter holder 5 may include 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 support the respective upper and lower ends of the filter 2. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 may contact and / or engage with an outer surface of the filter 2. Each may form a liquid-tight or air-tight seal around the filter 2. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 may be supported by one or more housings (e.g., may be supported by the inner walls of one or more housings).

[0106] The apparatus 1 may be configured such that the filter 2 is disposed in the filter holder 5 in a vertical orientation with the inlet face of the filter uppermost. At least a portion of the spray device 7 may be disposed vertically above the inlet face. The spray direction of the spray device 7 may be coaxial with the longitudinal axis of the filter 2. The spray direction and the longitudinal axis of the filter 2 may coincide.

[0107] The apparatus 1 may further comprise a flow conduit 10 disposed between the spray device 7 and the inlet face of the filter 2. The flow conduit 10 may function to constrain and channel the primary gas flow towards the inlet face of the filter 2. The flow conduit 10 may function to align the primary gas flow such that the flow direction of the primary gas flow when it contacts the inlet face of the filter 2 is perpendicular to the inlet face.

[0108] The flow conduit 10 may be empty to provide an unobstructed flow path between the spray device 7 and the inlet face of the filter 2. Alternatively, the flow conduit 10 may include a flow regulator interposed between the spray device 7 and the inlet face of the filter 2, the flow regulator acting to facilitate dispersion of the dry powder 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.

[0109] 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 face of the filter 2. The flow conduit 10 may have a size that matches the size of the inlet face of the filter 2.

[0110] 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 in an upper region of the flow conduit 10. The nozzle 25 may be disposed in line with the longitudinal axis of the filter 2.

[0111] The inlet face of the filter 2 may be located from the spraying device, for example more than 10 cm, optionally more than 20 cm, from the nozzle 25 of the spraying device 7. Particular advantages may be found when the inlet face of the filter 2 is located more than 75 cm, optionally more than 100 cm, from the nozzle outlet of the spray nozzle 25. Additionally or alternatively, the spraying device may be located at a distance from the inlet face of the filter 2 that is up to four times the diameter of the inlet face of the filter 2, for example from the nozzle 25 of the spraying device 7.

[0112] A vacuum generator 6 is provided for establishing a primary gas flow through the porous structure of the filter 2 during use by applying a pressure drop to the outlet face of the filter 2. The vacuum generator 6 may include a vacuum cone 40 which may define a funnel that engages the outlet face of the filter 2. The inflatable lower seal bladder 30 may form a seal between the outlet face of the filter 2 and the vacuum cone 40. The vacuum generator 6 may include 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 stream.

[0113] The vacuum generator 6 may include a volumetric flow sensor, which may be an orifice plate 44 in combination with a pressure sensor 45 disposed along the conduit 43. The vacuum generator 6 may include a bypass conduit 46 that extends to an intake 47.

[0114] The apparatus 1 may further comprise a pressure sensor 41 for monitoring the back pressure of the filter 2. A single pressure sensor 41 may be used. The single pressure sensor 41 may be located within the vacuum generator 6, preferably within the filter holder or other housing of the vacuum generator, such as the vacuum cone 40.

[0115] The controller 9 controls the operation of at least the vacuum generator 6 and the spray device 7. In Figure 1, the operational connections between the controller 9 and the remainder of the apparatus 1 have been omitted for clarity. However, those skilled in the art will recognize that the necessary connections may be provided by any suitable means. Such connections may be wired or wireless.

[0116] The controller 9 may be configured to control the transfer of the dry powder 4 from the reservoir 3 to the spray 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.

[0117] The controller 9 may be configured to control the spraying of the dry powder 4 toward the inlet face of the filter 2 independently of controlling the primary gas flow. The use of the term "independently" herein refers to the ability of the controller 9 to control each of the variables of the spraying of the dry powder 4 and the primary gas flow individually and without regard to the status of the other variable. For example, the controller 9 may establish the primary gas flow without simultaneously spraying the dry powder 4. For example, the controller 9 may increase or decrease the spraying rate of the dry powder 4 without changing the volumetric flow rate of the primary gas flow. For example, the controller 9 may increase or decrease the volumetric flow rate of the primary gas flow without changing the spraying rate of the dry powder 4. For example, the controller 9 may control the operation of the spraying device 7 independently of controlling the operation of the vacuum pump 42.

[0118] The controller 9 may be configured to operate the vacuum generator 6 to establish a primary gas flow before the dry powder 4 is transferred to the spraying device 7 and sprayed towards the inlet face of the filter 2.

[0119] The controller 9 may be configured to control the secondary gas flow generator, e.g., compressor 22, independently of the vacuum generator 6. The 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 to operate the secondary gas flow generator, e.g., compressor 22, for only a portion of the period of the primary gas flow.

[0120] The controller 9 may be configured to control the vacuum generator 6 to control the level of pressure drop applied to the outlet face of the filter 2 independently of controlling the transport device 8 and / or the spraying device 7 in order to control the velocity or mass flow rate of the dry powder 4 sprayed towards the inlet face of the filter 2.

[0121] The controller 9 may be configured to stop spraying the dry powder 4 towards the inlet face of the filter 2 when a required value of back pressure on the filter 2 is reached, for example as detected by a pressure sensor 41 .

[0122] Apparatus 1 may be used to treat the filter with dry powder 4 that includes or consists of one or more refractory powders, optionally including one or more fumed refractory powders and / or one or more aerogels. Additionally or alternatively, apparatus 1 may be used to treat the filter with dry powder 4 that includes or consists of a metal compound for forming a metal oxide by pyrolysis. In examples, the metal compound may include or consist of a metal hydroxide, a metal phosphate, a metal carbonate, a metal sulfate, a metal perchlorate, a metal iodide, a metal oxalate, a metal acetate, a metal chlorate, or mixtures thereof.

[0123] An example of a method for treating a filter according to the present disclosure will now be described with reference to Figure 2, which shows a flow diagram illustrating a method for manufacturing a filter 2 incorporating the use of an apparatus 1. By way of example, the method will be described with reference to a filter 2 provided with a catalytic coating.

[0124] In step S21, a catalyst slurry is prepared by methods known in the art.

[0125] In step S22, a washcoat is prepared from the catalyst slurry by methods known in the art. The washcoat may 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 combinations of any two or more thereof.

[0126] In step S23, the washcoat is poured and applied to the bare filter 2 by methods known in the art. For example, the washcoat may be applied to a first side (e.g., top side) of the filter 2, and an opposite second side (e.g., bottom side) of the filter 2 may be subjected to at least a partial vacuum to effect migration of the washcoat through the porous structure of the filter 2. The filter 2 may be coated in one pour, and the washcoat may be applied to the filter 2 in a single step, leaving the filter 2 in a single orientation. Alternatively, the filter 2 may be coated in two pours. For example, in the first pour, the filter 2 may be in a first orientation with the first side uppermost and the second side lowermost. The coating may be applied to the first side, coating a portion of the length of the filter 2. The filter 2 may then be flipped so that the second side is uppermost. A coating may then be applied to the second side to coat the portions of the filter 2 that were not coated in the first pour. Advantageously, the two-injection process allows for different coatings to be applied to each end of the filter 2 .

[0127] In step S24, the filter 2 may be dried.

[0128] In step S25, the filter 2 may be fired by methods known in the art.

[0129] In optional step S26, the backpressure of the filter 2 before treatment may be measured.

[0130] In optional step S27, filter 2 may be placed in stock to await processing. Then, in step S28, filter 2 may be removed from stock and sent for processing. Alternatively, filter 2 may be processed immediately, i.e., by proceeding directly to step S29.

[0131] In step S29, Filter 2 is processed in accordance with the present disclosure, as described in further detail below with reference to FIG.

[0132] In step S30, after processing, the filter 2 may be fired.

[0133] Calcination of the filter may be carried out at a temperature selected to produce pyrolysis of the dry powder 4 .

[0134] The firing temperature may be selected to be at least 150°C, optionally at least 250°C, optionally at least 500°C.

[0135] In some embodiments, it is preferred that the firing temperature is no greater than 550° C. However, in other embodiments, the firing temperature may be selected to be greater than 550° C. The firing temperature may be selected to be up to 900° C., optionally up to 1150° C.

[0136] In one example, the firing temperature may be selected to be between 300°C and 500°C. In another example, the firing temperature may be selected to be about 520°C. In another example, the firing temperature may be selected to be about 580°C. In another example, the firing temperature may be selected to be about 900°C.

[0137] The baking may be carried out for 30 to 90 minutes, optionally for 30 to 60 minutes. In one example, the period is about 35 minutes. In another example, the period is about 60 minutes. In the baking, the residence time is 1 to 15 minutes, preferably 5 to 10 minutes.

[0138] In optional step S31, the backpressure of the filter 2 after treatment may be measured.

[0139] In step S32, the completed filter 2 may be prepared for shipment to a customer.

[0140] FIG. 3 is a flow diagram showing the process of step S29 in FIG.

[0141] In step S29-1, a filter may be loaded into a filter holder 5. The filter 2 may be held in a stationary position during processing. The filter 2 may be gripped at its upper and / or lower ends by the filter holder 5. The inflatable upper seal bladder 31 and the inflatable lower seal bladder 30 may be inflated to contact and / or engage an outer surface of the filter 2. The filter 2 may be held in a vertical orientation with the inlet face of the filter uppermost. Operation of the filter holder 5, such as the inflation of the inflatable upper seal bladder 31 and the inflatable lower seal bladder 30, may be controlled by the controller 9.

[0142] In step S29-2, the vacuum generator 6 may be activated by the controller 9 to establish a primary gas flow through the filter 2. Preferably, the primary gas flow is established before the dry powder 4 is transferred to the spraying device 7 and sprayed towards the inlet face of the filter 2. The level of pressure drop generated by the vacuum generator 6 may be controlled by the controller 9 independently of the rate or mass flow rate of transfer of the dry powder 4 from the reservoir 3 to the spraying device 7. The primary gas flow may be greater than 10 m 3 / hour~5,000m 3 / h, preferably 400m 3 / hour~2,000m 3 / h, preferably 600m 3 / hour~1000m 3 / hr volumetric flow rate.

[0143] In step S29-3, the backpressure of filter 2 may be measured while the primary gas flow is established but before the secondary gas flow is established. The backpressure may be measured in this step until the backpressure stabilizes.

[0144] The back pressure of filter 2 is the first derivative of the primary gas flow rate ±Xm 3 time -1 .s -1 where X=0-0.30, optionally X=0.10-0.20, X=0.15. Additionally or alternatively, the back pressure of the filter 2 may be considered stable when the first derivative of the filter back pressure is ±Ymbar.s -1 where Y=0.5-3.0, optionally Y=1.0-2.0, optionally Y=1.5. Additionally or alternatively, the back pressure of filter 2 may be considered stable when the primary gas flow rate is within a predetermined flow rate of Z%, Z=1.5, optionally Z=1.0, optionally Z=0.5.

[0145] The backpressure may be measured through the use of pressure sensor 41. The backpressure measurement in step S29-3 may be in addition to or instead of the backpressure measurement in step S26. Alternatively, the backpressure measurement in step S26 may be used in place of the backpressure measurement in step S29-3. The backpressure measurement in step S26 and / or the backpressure measurement in step S29-3 may be used by controller 9 as a first backpressure measurement in filter 2 before processing.

[0146] In step S29-4, the dry powder 4 is sprayed by the spraying device 7 onto the inlet face of the filter 2. During spraying of the dry powder 4, the dry powder 4 may be fed to the spraying device 7 by a transport device 8.

[0147] The spraying of dry powder 4 towards the inlet face of the filter 2 is preferably controllable by a controller 9 independently from establishing and controlling the primary gas flow.

[0148] During step S29-4, for example, a secondary gas flow provided by the compressor 22, separate from the primary gas flow, may be used to transport the dry powder 4 from the reservoir 3 to the spraying device 7. Preferably, the secondary gas flow is controllable by the controller 9 independently of the primary gas flow. For example, the controller 9 may control the operation of the compressor 22 and / or the valves and / or the nozzles 25 of the spraying device 7 independently of controlling the operation of the vacuum pump 42. The dry powder 4 may be sprayed towards the inlet face of the filter 2 by using the secondary gas flow. The secondary gas flow may comprise a flow of compressed gas, preferably air.

[0149] During step S29-4, the primary gas flow is preferably maintained as a continuous flow. During step S29-4, the secondary gas flow may be applied as a single burst or multiple intermittent bursts.

[0150] In step S29-5, the backpressure of the filter 2 is monitored while the dry powder 4 is being sprayed. The backpressure may be monitored by use of pressure sensor 41. The controller 9 may be configured to stop spraying of the dry powder 4 towards the inlet face of the filter 2 when the backpressure of the filter 2 reaches a required value. If the required value for the backpressure has not yet been reached, then the controller 9 is configured to return to step S29-4 and continue spraying of the dry powder 4. This feedback may be continuous and need not involve any pause in the spraying of the dry powder 4, i.e. the controller 9 may continuously monitor the backpressure of the filter 2 as the spraying of the dry powder 4 is in progress. The backpressure of the filter 2 may be continuously monitored during at least step S29-5. The backpressure may be monitored for one sample.s -1 More than 5 samples, optionally. -1 or more, optionally, 10 samples.s -1 The back pressure may be continuously monitored by measuring it at a sample rate of at least 100 s. The pressure sensor 41 may incorporate some damping to reduce or eliminate the effects of transient readings that may be related to noise.

[0151] In step S29-6, the nebulization of the dry powder 4 is stopped. For example, this may be accomplished by the controller 9 stopping the transfer of the dry powder by the transport device 8 and / or stopping the secondary gas flow of the nebulization device 7. In step S29-6, the primary gas flow may be maintained through the porous structure of the filter 2 for a period of time after the nebulization of the dry powder 4 has stopped. The controller 9 may be configured to operate the vacuum generator 6 for a period of time after the nebulization of the dry powder 4 has stopped. For example, the primary gas flow may be maintained until the back pressure measured in this step has stabilized.

[0152] As shown above, the back pressure of filter 2 is determined by the first derivative of the primary gas flow rate ±Xm 3 time -1 .s -1where X=0-0.30, optionally X=0.10-0.20, X=0.15. Additionally or alternatively, the back pressure of the filter 2 may be considered stable when the first derivative of the filter back pressure is ±Ymbar.s -1 where Y=0.5-3.0, optionally Y=1.0-2.0, optionally Y=1.5. Additionally or alternatively, the back pressure of filter 2 may be considered stable when the primary gas flow rate is within a predetermined flow rate of Z%, Z=1.5, optionally Z=1.0, optionally Z=0.5.

[0153] Optionally, in step S29-6, the amount of dry powder 4 delivered towards the inlet face of the filter 2 may be measured. The controller 9 is configured to determine the amount of dry powder 4 delivered, for example, from a signal output from the injection device 15, for example from an output from a loss-in-weight feeder.

[0154] The method may be configured to deliver a maximum filter load of 10-40 g / l, optionally 15-30 g / l, optionally about 20 g / l of dry powder 4, or to deliver a maximum filter load of <10 g / l, optionally <5 g / l, optionally <2 g / l of dry powder 4.

[0155] In step S29-7, the primary gas flow through filter 2 is stopped. This may be accomplished by the controller 9 shutting down the vacuum generator 6, i.e., shutting down the vacuum pump 42. Alternatively, this may be accomplished by the controller manipulating a valve on the vacuum generator 6 to redirect suction through bypass conduit 46 to draw air through intake 47. This may avoid the need to shut down the vacuum pump 42 between processing of successive filters 2, which may result in faster cycle times.

[0156] In step S29-8, the filter 2 is removed from the filter holder 5, for example, by deflating the inflatable upper seal bladder 31 and the inflatable lower seal bladder 30. The filter 2 may then be removed and proceed to step S30 as described above.

[0157] Returning to step 29-5, consider in more detail the events that trigger the cessation of aerosolization of dry powder 4.

[0158] When treating filter 2, applicants have found that the final backpressure of the filter cannot be controlled by simply controlling the mass loading of dry powder 4 applied to filter 2. For example, FIG. 4 illustrates the treatment of two filters A and B, which have similar initial backpressures (36 and 38 mbar) before coating. After treatment with dry powder 4, both filters have similar backpressures of 64 mbar and 67 mbar. However, the mass loadings of the filters were very different. Filter A was treated with 2.8 g of dry powder sprayed for 7 seconds. Filter B was treated with 8 g of dry powder sprayed for 20 seconds. The difference in the mass loading of dry powder required to achieve a similar increase in backpressure is believed to be due to differences in the substrate properties of the filters, including but not limited to the pore size and location of any applied washcoat.

[0159] As a result, it may be beneficial to monitor the back pressure of the filter 2 during spraying of the dry powder 4 in step S29-5 and, as described above, for the controller 9 to stop spraying of the dry powder 4 towards the inlet face of the filter 2 when the back pressure of the filter 2 reaches the required value.

[0160] In some examples, when the spraying of the dry powder 4 stops, the required value of the back pressure of the filter 2 is a predetermined target back pressure ρ target A given back pressure ρ target may be the desired final backpressure of the filter 2 as measured by the apparatus 1, i.e., the coating apparatus. The desired backpressure ρ targetcan be the absolute back pressure. The absolute back pressure can be, for example, 600 m 3 The pressure can be 20-180 mbar at a flow rate of 1 / hour.

[0161] The applicant believes that the required value is a given back pressure, ρ target For example, as illustrated in the example of FIG. 5, the filter 2 final backpressure may overshoot the target, ρ target Dry powder spraying started at about 17 seconds when the filter back pressure stabilized, and the filter back pressure, ρ BP However, it stopped at about 29 seconds when the target of 63 mbar was reached. However, the filter back pressure continued to increase, i.e., overshoot, and eventually stabilized around 70 mbar.

[0162] As a result, the Applicant has discovered that an improved processing method may be achieved by monitoring the back pressure of the filter 2 in step S29-5 and ceasing the spraying of the dry powder 4 towards the inlet face of the filter 2 if: ρ BP ≧ρ target -ρ offset During the ceremony, ρ BP is the back pressure of filter 2, ρ target is the predetermined target backpressure for filter 2, ρ offset is the preselected offset pressure.

[0163] For example, FIG. 6 shows the target for a given backpressure, ρ target , which indicates a corrected treatment process. offsetDry powder nebulization started at about 14 seconds when the filter back pressure stabilized and stopped at about 37 seconds when the filter back pressure, PBP, reached 60 mbar, i.e., 63 mbar to 3 mbar. The filter back pressure continued to increase after the cessation of dry powder nebulization and eventually stabilized at about 63 mbar, i.e., the desired final back pressure.

[0164] The desired back pressure for the filter, ρ target may be the absolute backpressure of filter 2. For example, a predetermined target backpressure for filter 2, ρ target may be a target backpressure between 20 and 180 mbar. Alternatively, a predetermined target backpressure for filter 2, ρ target may be the relative backpressure of filter 2. For example, a predetermined target backpressure for filter 2, ρ target may be the backpressure relative to the initial backpressure of the filter 2 prior to spraying of the dry powder 4. For example, a predetermined target backpressure for the filter 2, ρ target may be 105% to 200%, optionally 125% to 150%, of the initial back pressure of the filter 2.

[0165] ρ BP ≧ρ target -ρ offset is the minimum period, t min When this is true for a minimum period of time, the spraying of the dry powder 4 towards the inlet face of the filter 2 can be stopped. min It may be ≧0.1 seconds, optionally ≧0.5 seconds, optionally ≧1.0 seconds.

[0166] ρ offset may be, for example, 1 to 10 mbar, optionally 2 to 5 mbar, optionally 3 to 5 mbar. For example, such ρ offset is ρ target It can be used when the pressure is between 20 and 180 mbar.

[0167] The desired target backpressure of the filter, ρ target teeth, - selecting a desired back pressure on the filter as measured by a test device different from the coating device 1; - establishing a calibration map for converting the back pressure measured on the test apparatus to the back pressure measured on the coating apparatus 1; - Convert the desired backpressure using a calibration map to a given target backpressure ρ target and

[0168] For example, Figure 7 shows a first example of a calibration map for converting between the backpressure on a coating apparatus 1 (shown on the x-axis and entitled "Inline CFBP") and the backpressure on a test apparatus, in this case a Superflow Flow Bench 1050 available from Superflow of Sussex, Wl, USA. The backpressure on both the coating apparatus 1 and the test apparatus is measured at 600 m 3 CFBP is measured in mbar at a flow rate of 600 M / hr for both coating and testing devices. As can be seen, in this case a linear relationship can be established between the back pressures of both devices when measured at the same flow rate. In this example, for the range of CFBP of interest, the present application has found that a calibration map in the form of a linear or quadratic fit can accurately allow the conversion of CFBP on the coating device 1 and the testing device. In the example of FIG. 7, the flow rates at which CFBP was measured were 600 M / hr for both coating device 1 and the testing device. 3 It was / o'clock.

[0169] Moreover, applicants have found that a single linear or quadratic fit can accurately allow for the conversion of CFBP in the coating apparatus 1 and the test apparatus, regardless of the diameter, length, or substrate properties of the selected flow rate or filter 2, so long as the same selected flow rate is used in the coating apparatus 1 and the test apparatus. For example, FIG. 8 shows that a calibration map in the form of a single linear or quadratic fit accurately allows for the conversion of CFBP for two different filters, labeled Part 1 and Part 2 in FIG. 8. Not only that, but both Parts 1 and 2 are 600M 3 When tested at a flow rate of 800M / hr, 3 When testing at 100 Hz / hour, the same linear or quadratic fit is applied.

[0170] It may be desirable to convert between the CFBP on the coating apparatus 1 and the CFBP on the test apparatus where different flow rates are used on each apparatus. Applicants have discovered that this is possible by using a calibration map that includes a set of linear or quadratic fit lines. For example, FIG. 9 shows a calibration map with two fit lines. The leftmost fit line corresponds to the CFBP when the flow rates on the coating apparatus 1 and the test apparatus are both 600M. 3 The rightmost fitted line represents the conversion of CFBP for the same Part 1 and Part 2, with a flow rate of 800 M 3 / hr, and the flow rate in the test device is 600M 3 / hr. It will be appreciated that the calibration map may include any desired number of fit lines for any desired combination of coatings and test CFBPs.

[0171] The offset pressure, ρ, as explained above offset The use of a constant offset pressure, ρ, as explained above, may result in improved and acceptable results for the final back pressure of the filter 2. However, Applicant has discovered that further improvements may be made. For example, Applicant has discovered that the properties of the filter 2 may affect the loading of the dry powder, and in particular, the loading rate of the dry powder 4 with respect to time may be affected by properties including the pore size of the filter 2, the porosity of the filter 2, the wall thickness, and / or the cell density. As a result, the use of a constant offset pressure, ρ, as explained above, may result in improved and acceptable results for the final back pressure of the filter 2. offset Using a fixed offset pressure may still lead to some variation in the final backpressure obtained. This is shown in FIG. 10, which shows the powder loading stages of eight filters 2 with different pore sizes. As can be seen, the slope of the backpressure-time response curve differs between filters. Because of this, the use of a fixed offset pressure would not obtain a uniform final backpressure for all eight filters 2. For the eight exemplary filters of FIG. 10, the final obtained backpressure had an average backpressure of 64.5 mbar (compared to a target of 63 mbar) and a standard deviation of 1.2 mbar.

[0172] For example, Figure 11 illustrates this using filters numbers 4 and 6 from Figure 10 as examples. In both cases, the spraying of dry powder 4 is stopped when the filter reaches 60 mbar (target backpressure of 63 mbar minus an offset pressure of 3 mbar). Filter number 6 has a relatively shallow slope of its response curve (i.e., it requires a relatively large amount of powder for each mbar increase in backpressure), and the final obtained backpressure closely matches the target of 63.1 mbar. However, filter number 4 has a steeper slope of its response curve (i.e., it requires a relatively small amount of powder for each mbar increase in backpressure), and the final obtained backpressure passes the target and reaches 66.6 mbar.

[0173] As a result, Applicant has discovered that an improved processing method may be achieved by monitoring, in step S29-5, the back pressure of the filter 2 during the spraying of the dry powder 4, and ceasing the spraying of the dry powder towards the inlet face of the filter 2 when: ρ est ≧ρ target During the ceremony, ρ target is the desired target backpressure for the filter; ρ est is the estimated final back pressure of the filter, ρ est is calculated by extrapolation of the measured backpressure data for the filter, obtained during nebulization of the dry powder 4.

[0174] The estimated final back pressure of the filter, ρ est is the measured back pressure data T s can be calculated by extrapolating forward in time over T seconds. s is the settling time.

[0175] The method can be carried out on a coating apparatus 1, with a settling time, T scan be a coating equipment dependent variable, preferably independent of filter 2. Settling time, T s The parameters of can be selected to characterize the performance of the coating apparatus 1. Settling time, T s can be theoretically calculated for the coating apparatus 1. Alternatively, the settling time, T s may be determined experimentally for the coating apparatus 1 by testing a sample filter. For example, experiments may be performed iteratively to obtain a good estimate of the settling time.

[0176] Estimated final backpressure of filter 2, ρ est can be calculated by curve fitting the measured backpressure data and extrapolating the fitted curve forward in time. For example, backpressure measurements can be taken, preferably at a high sampling rate, during the initial loading of the dry powder 4 of the filter 2. The processor 9 (or other computational resources) can then calculate a fitted line that fits the recorded backpressure data and then use the fitted line to extrapolate forward in time. In some examples, the fitted line can be a quadratic fitted line that fits all or most of the recorded backpressure measurements. In other examples, the fitted line can be a linear fitted line that fits the current or most recent portion of the recorded backpressure measurements.

[0177] FIG. 12 shows the application of the method to filter number 4 referenced in FIG. 11. The settling time, T s was calculated from an examination of the results for the eight filters in FIG. 10 to be 3.5 seconds for the coating apparatus 1 used.

[0178] In Figure 12, 4.1 refers to filter number 4, which was processed with a fixed offset pressure as described above with reference to Figure 11. As mentioned above, powder spraying was stopped when the filter reached a backpressure of 60 mbar (target backpressure of 63 mbar minus the offset pressure of 3 mbar) and the final obtained backpressure reached 66.6 mbar, past the target.

[0179] The result marked as 4.2 is T s 10 shows the effect of using the improved method of extrapolating measured backpressure data forward in time for a period of 1000 s, i.e., 3.5 s in this example. As can be seen, the final obtained backpressure was 62.8 mbar, very close to the target of 63 mbar. For the eight exemplary filters of FIG. 10, the improved method can obtain a final backpressure with an average backpressure of 63.7 mbar (relative to the target of 63 mbar) and a standard deviation of 0.85 mbar, which is significantly improved compared to the results of the method using a fixed offset pressure.

[0180] In accordance with the present disclosure, a treated filter may be provided that has one or more advantages over prior art filters. Preferably, but not limited to, the treated filter may be treated in accordance with the present disclosure and / or may be treated using an apparatus in accordance with the present disclosure.

[0181] Further aspects and embodiments of the present disclosure are described in the following clauses.

[0182] Item A1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing spraying of the dry powder towards the inlet face of the filter when: ρ BP ≧ρ target- ρ offset During the ceremony, ρ BP is the back pressure of the filter, ρ target is the desired target backpressure for the filter; ρ offset is a preselected offset pressure.

[0183] In step f), ρ BP >ρ target -ρ offset is the minimum period, t min When the spray of dry powder toward the inlet face of the filter is stopped, the spray of dry powder toward the inlet face of the filter is stopped when ... min The method according to paragraph A1, wherein the time period is ≧0.1 seconds, optionally ≧0.5 seconds, optionally ≧1.0 seconds.

[0184] Term A3.ρ offset The method according to paragraph A1 or A2, wherein the pressure is 1 to 10 mbar, optionally 2 to 5 mbar, optionally 3 to 5 mbar.

[0185] In section A4. step f), during at least step e), the backpressure of the filter is continuously monitored, and optionally, the backpressure is monitored every 1 sample.s -1 More than 5 samples, optionally. -1 or more, optionally, 10 samples.s -1 The method of any one of paragraphs A1-A3, wherein the back pressure may be continuously monitored by measuring the back pressure at a sample rate equal to or greater than the sample rate.

[0186] Item A5. The method of any one of items A1-A4, further comprising, in step c), monitoring the back pressure of the filter, and passing the primary gas stream through the porous structure of the filter until the back pressure of the filter stabilizes before starting step d).

[0187] Term A6. The desired target backpressure for the filter, ρ target for a stable back pressure monitored in step c).

[0188] Section A7. The method according to any one of paragraphs A1 to A6, further comprising the step of: g) monitoring the back pressure of the filter and maintaining the primary gas flow through the porous structure of the filter until the back pressure of the filter stabilizes after the spraying of the dry powder has been stopped.

[0189] Item A8. Filter back pressure is i) the primary gas flow rate is within 0.5% of the specified flow rate; ii) The first derivative of the primary gas flow rate is within ±0.15 m 3 time -1 .s -1 is as follows: iii) The first derivative of the filter back pressure is ±1.5 mbar.s -1 The method of any one of paragraphs A5 to A7, which is considered stable when:

[0190] Term A9. Back pressure, ρ BP The method of any one of paragraphs A1-A8, wherein A is the absolute back pressure measured relative to atmospheric pressure.

[0191] Item A10. The method uses a coating apparatus to perform at least steps a) through f), and a predetermined target back pressure, ρ, on the filter. target ,but, selecting a desired back pressure on the filter as measured by a test device different from the coating device; - establishing a calibration map for converting the back pressure measured on the test apparatus to the back pressure measured on the coating apparatus; - Convert the desired backpressure using a calibration map to a given target backpressure, ρ target and establishing:

[0192] Item B1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a reduced pressure to the outlet face of the filter while monitoring the back pressure of the filter, and passing the primary gas flow through the porous structure of the filter until the back pressure of the filter stabilizes; d) after establishing a stable back pressure on the filter, transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device, such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter, and contacts the porous structure, while monitoring the back pressure of the filter; f) stopping the spray of dry powder towards the inlet face of the filter; g) continuing to monitor the filter backpressure while maintaining the primary gas flow through the porous structure of the filter after spraying of the dry powder has been stopped until the filter backpressure stabilizes.

[0193] Term B2. The first derivative of the primary gas flow rate is ±Xm 3 time -1 .s -1 The method of claim B1, wherein the filter back pressure is considered stable when X=0 to 0.30, optionally, X=0.10 to 0.20, X=0.15.

[0194] Term B3. The first derivative of the filter back pressure is ±Ymbar.s -1 The method of any one of paragraphs B1 to B2, wherein the filter backpressure is considered stable when Y=0.5-3.0, optionally Y=1.0-2.0, and optionally Y=1.5:

[0195] Paragraph B4. The method of any one of paragraphs B1-B3, wherein the filter backpressure is considered stable when the primary gas flow rate is within Z% of a predetermined flow rate, where Z=1.5, optionally Z=1.0, optionally Z=0.5.

[0196] Item B5. The method of any one of items B1-B4, wherein the back pressure is an absolute back pressure measured relative to atmospheric pressure.

[0197] Clause C1. The method of any one of clauses A1-A10 or B1-B5, wherein the backpressure of the filter is measured using a pressure sensor, optionally a single pressure sensor disposed within a filter holder or other housing fluidly connected to the outlet face of the filter.

[0198] Item D1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring the dry powder from the reservoir to a spray device located upstream of the inlet face of the filter; e) spraying a dry powder towards the inlet face of the filter using a spraying device such that the dry powder is entrained in the primary gas flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing spraying of the dry powder towards the inlet face of the filter when: ρ est ≧ρ target During the ceremony, ρ targetis the desired target backpressure for the filter; ρ est is the estimated final back pressure of the filter, ρ est is calculated by extrapolation of measured backpressure data for the filter obtained during step f).

[0199] Term D2.ρ est The measured back pressure data is s is calculated by extrapolating forward in time over seconds, T s is the settling time. The method according to item D1.

[0200] Item D3. The method is performed on a coating apparatus and has a settling time, T s The method according to item D2, wherein is a coating equipment dependent variable and is preferably independent of the filter.

[0201] Term D4.ρ est The method of any one of paragraphs D1-D3, wherein V is calculated by curve fitting the measured backpressure data and extrapolating the fitted curve forward in time.

[0202] Item E1. Dry powder, a) a metal compound for forming a metal oxide by pyrolysis; b) a metal oxide, or c) The method according to any one of paragraphs A1 to A10, or B1 to B5, or C1 to C2, or D1 to D4, which comprises or consists of an aerogel.

[0203] Item E2. The method of item E1, wherein the metal compound comprises or consists of a metal hydroxide, a metal phosphate, a metal carbonate, a metal sulfate, a metal perchlorate, a metal iodide, a metal oxalate, a metal acetate, a metal chlorate, or a mixture thereof.

[0204] Paragraph E3. The method of paragraphs E1 or E2, wherein the metal of the metal compound comprises or consists of one or more of magnesium, calcium, strontium, barium, aluminum, zirconium, manganese, lithium, iron, cobalt, nickel, copper, or gallium.

[0205] Paragraph E4. The method of any one of paragraphs E1-E3, wherein the metal oxide of option c) comprises one or more fumed metal oxides or fumed mixed oxides, such as fumed alumina, fumed silica, or fumed titania.

[0206] Paragraph E5. The method of any one of paragraphs E1-E4, wherein the aerogel comprises one or more of silica aerogel, alumina aerogel, carbon aerogel, titania aerogel, zirconia aerogel, ceria aerogel, metal oxide aerogel, and mixed oxide aerogel.

[0207] Item E6.Dry powder is 1~3g / cm 3 , optionally 1.5 to 2.5 g / cm 3 , optionally about 2 g / cm 3 or the dry powder has a tap density of 0.10 g / cm 3 less than, optionally 0.08 g / cm 3 less than, optionally 0.07 g / cm 3 less than, optionally 0.06 g / cm 3 less than, optionally, 0.05 g / cm 3 The method of any one of paragraphs E1-E5, having a tap density of less than 1000 nm.

[0208] Paragraph E7. The method of any one of paragraphs E1-E6, wherein the dry powder has a d50 (by volume) of less than 10 micrometers, optionally less than 5 micrometers, optionally about 2 micrometers.

[0209] Paragraph E8. The method of any one of paragraphs E1-E7, comprising providing a maximum filter loading of 10-40 g / l, optionally 15-30 g / l, optionally about 20 g / l of dry powder, or providing a maximum filter loading of less than 10 g / l of dry powder, optionally less than 5 g / l of dry powder, optionally less than 2 g / l of dry powder.

[0210] Paragraph E9. The method of any one of paragraphs E1-E8, further comprising coating the filter with a washcoat, preferably a catalytic washcoat, prior to step b).

[0211] Item F1. The method of any one of items A1 to E9, further comprising a step of calcining the filter after loading with the dry powder.

[0212] Item F2. The method of item F1, wherein the calcination is at a temperature of at least 150°C, optionally at least 250°C, optionally at least 500°C.

[0213] Paragraph F3. The method of paragraph F1 or F2, wherein the calcination is at a temperature of less than or equal to 550°C, alternatively at a temperature greater than 550°C, optionally at a temperature up to 900°C, optionally at a temperature up to 1150°C.

[0214] Paragraph F4. The method of any one of paragraphs F1-F3, wherein the calcination is carried out for a period of 30-90 minutes, optionally 30-60 minutes, including a residence time of 1-15 minutes, preferably 5-10 minutes.

[0215] The method of any one of paragraphs A1 to F4, wherein in paragraph G1. step d), a secondary gas flow separate from the primary gas flow is used to transport the dry powder from the reservoir to the spray device, and optionally, the secondary gas flow is controllable independently of the primary gas flow.

[0216] Paragraph G1. The method of paragraph G1, wherein the secondary gas stream comprises a stream of compressed gas, preferably air.

[0217] Paragraph G2. The method of paragraph G1 or G2, wherein the secondary gas flow is applied as a single burst or multiple intermittent bursts.

[0218] Paragraph G3. The method of any one of paragraphs A1-G2, including using a vacuum generator to establish a primary gas flow through the porous structure of the filter.

[0219] Paragraph G4. The method of paragraph G3, wherein the level of pressure drop generated by the vacuum generator is controllable independently of the rate or mass flow rate of transfer of the dry powder from the reservoir to the spray device.

[0220] Item G5. Primary gas flow is 10 m 3 / hour~5,000m 3 / h, preferably 400m 3 / hour~2,000m 3 / h, preferably 600m 3 / hour~1000m 3 The method according to any one of paragraphs A1 to G4, having a volumetric flow rate of 1 / hour.

[0221] Paragraph G6. The method of paragraph G5, further comprising using a pressure sensor, preferably a single pressure sensor, to monitor the backpressure.

[0222] Paragraph G7. The method of paragraph G6, wherein a pressure sensor, preferably a single pressure sensor, is disposed within a filter holder or other housing that is fluidly connected to the outlet face of the filter.

[0223] Paragraph G8. The method of paragraph G6 or G7, wherein the same pressure sensor, preferably the same single pressure sensor, is used to monitor the backpressure of the filter during at least steps c) and f).

[0224] Item G9. The method of any one of items A1 to G8, wherein in step e), the dry powder is sprayed from one or more outlets of the spray device.

[0225] Paragraph G10. The method of paragraph G9, wherein one or more outlets of the spray device include an opening size of 1-10 mm, optionally 0.5-5.0 mm, optionally 1.0-2.5 mm, optionally 1.0-2.0 mm.

[0226] Paragraph G11. The method of paragraph G9 or G10, wherein the dry powder is sprayed from one or more fixed outlets of a spray device.

[0227] Paragraph G12. The method of paragraph G9 or G10, wherein the dry powder is sprayed from one or more movable outlets of the spray device, preferably from one or more oscillating outlets.

[0228] Paragraph G13. The method of any one of paragraphs A1-G12, further comprising in step e) channeling dry powder from the spray device to an inlet face of a filter in the flow conduit.

[0229] Paragraph G14. The method of paragraph G13, wherein the flow conduit provides an unobstructed flow path between the spray device and the inlet face of the filter.

[0230] Paragraph G15. The method of paragraph G13, wherein the flow conduit includes a flow regulator interposed between the spray device and the inlet face of the filter, the flow regulator acting to promote dispersion of the dry powder within the gas flow.

[0231] Paragraph G16. The method of paragraph G15, wherein the flow regulator comprises one or more of a static mixer, a mesh, a sieve, a baffle, and an orifice plate.

[0232] Paragraph G17. The method according to any one of paragraphs A1 to G16, wherein the inlet face of the filter is located 10 to 80 cm, preferably 15 to 20 cm, from the spraying device, and / or the spraying device is located at a distance from the inlet face of the filter, the distance being at most 4 times the diameter of the inlet face of the filter.

[0233] Item G18. The method of any one of items A1 to G17, further comprising injecting dry powder from a reservoir in step d).

[0234] Paragraph G19. The method of paragraph G18, wherein injecting includes injecting by one or more of weight, volume, number of particles, and time.

[0235] Paragraph G20. The method of paragraph G18 or G19, comprising gravimetrically feeding the dry powder to the injection device.

[0236] Item G21. The method of any one of items G18 to G20, wherein the injecting uses a loss-in-weight feeder.

[0237] Item G22. The method according to any one of items A1 to G21, wherein in step a), the dry powder is contained in one or more hoppers.

[0238] Paragraph G23. The method of any one of paragraphs A1 to G22, wherein in step b), the filter is placed in the holder in a vertical orientation with the inlet surface uppermost.

[0239] The method according to paragraph G23, wherein in step d) the spraying device is arranged vertically above the inlet surface, and preferably the spraying direction of the spraying device is coaxial with the longitudinal axis of the filter, and preferably the spraying direction and the longitudinal axis coincide with each other.

[0240] Item G25. The method according to any one of items A1 to G24, wherein the porous substrate is a wall-flow filter.

[0241] Item H1. A filter obtainable by the method according to any one of items A1 to G25.

[0242] Paragraph H2. The filter of paragraph H1 that 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. 1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising the steps of: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring said dry powder from said reservoir to a spraying device located upstream of said inlet face of said 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 flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing the spraying of the dry powder towards the inlet face of the filter when: r ＢＰ ≧r ｔａｒｇｅｔ -r ｏｆｆｓｅｔ During the ceremony, ρ ＢＰ is the back pressure of the filter; ρ ｔａｒｇｅｔ is a predetermined target backpressure for the filter; ρ ｏｆｆｓｅｔ is the preselected offset pressure, A method wherein in step f) primary gas flow is maintained through the porous structure of the filter for a period of time after cessation of atomization of dry powder.

2. In step f), ρ ＢＰ >ρ ｔａｒｇｅｔ -ρ ｏｆｆｓｅｔ is the minimum period, t ｍｉｎ the spraying of the dry powder toward the inlet face of the filter is stopped when the equation: t ｍｉｎ 2. The method of claim 1, wherein the time is > 0.1 seconds.

3. ρ ｏｆｆｓｅｔ The method of claim 1, wherein the pressure is 1 to 10 mba.

4. 2. The method of claim 1, wherein in step f), the backpressure of the filter is continuously monitored during at least step e), optionally, the backpressure is continuously monitored by measuring the backpressure at a sample rate of 1 sample.s-1 or greater.

5. 10. The method of claim 1, further comprising, in step c), monitoring a back pressure of the filter; and, prior to commencing step d), passing the primary gas stream through the porous structure of the filter until the back pressure of the filter stabilizes.

6. The predetermined target backpressure for the filter, ρ ｔａｒｇｅｔ 6. The method of claim 5, wherein: a is related to the stable backpressure monitored in step c).

7. 10. The method of claim 1, further comprising the step of: g) monitoring the back pressure of the filter and maintaining the primary gas flow through the porous structure of the filter until the back pressure of the filter stabilizes after the atomization of the dry powder is stopped.

8. The back pressure of the filter is i) the primary gas flow rate is within 0.5% of the predetermined flow rate; ii) the first derivative of the primary gas flow rate is within ±0.15 m ３ time －１ .s －１ is as follows: iii) the first derivative of the back pressure of the filter is within ±1.5 mbar.s －１ 6. The method of claim 5, which is considered stable when:

9. The back pressure, ρ ＢＰ 2. The method of claim 1 , wherein A is the absolute back pressure measured relative to atmospheric pressure.

10. The method includes using a coating apparatus to perform at least steps a) through f), and the predetermined target backpressure, ρ ｔａｒｇｅｔ ,but, - selecting a desired back pressure for the filter as measured by a test device separate from the coating device; - establishing a calibration map for converting the back pressure measured on the test apparatus to the back pressure measured on the coating apparatus; - Converting the desired backpressure using the calibration map to obtain the predetermined target backpressure, ρ ｔａｒｇｅｔ and establishing:

11. 1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising the steps of: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a reduced pressure to the outlet face of the filter while monitoring the back pressure of the filter, and passing the primary gas flow through the porous structure of the filter until the back pressure of the filter stabilizes; d) after establishing a stable back pressure on the filter, transferring the dry powder from the reservoir to a spray device located 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 flow, passes through the inlet face of the filter, and contacts the porous structure while monitoring the back pressure of the filter; f) ceasing the spray of the dry powder towards the inlet face of the filter; g) continuing to monitor the back pressure of the filter while maintaining the primary gas flow through the porous structure of the filter after the atomization of the dry powder is stopped until the back pressure of the filter stabilizes; A method wherein in step f) primary gas flow is maintained through the porous structure of the filter for a period of time after cessation of atomization of dry powder.

12. The first derivative of the primary gas flow rate is ±Xm ３ time －１ .s －１ 12. The method of claim 11, wherein the backpressure of the filter is considered to be stable when X=0 to 0.30:

13. The first derivative of the back pressure of the filter is ±Ymbar.s －１ 12. The method of claim 11, wherein the backpressure of the filter is considered to be stable when Y=0.5 to 3.0:

14. 12. The method of claim 11, wherein the backpressure of the filter is considered stable when the primary gas flow rate is within Z % of a predetermined flow rate, where Z=1.

5.

15. The method of claim 11 , wherein the backpressure is an absolute backpressure measured relative to atmospheric pressure.

16. The method of claim 1 , wherein the backpressure of the filter is measured using a pressure sensor.

17. 1. A method for treating a filter for filtering particulate matter from an exhaust gas, comprising the steps of: a) containing a dry powder in a reservoir; b) placing a filter in 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) establishing a primary gas flow through the porous structure of the filter by applying a pressure drop across the outlet face of the filter; d) transferring said dry powder from said reservoir to a spraying device located upstream of said inlet face of said 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 flow, passes through the inlet face of the filter and contacts the porous structure; f) monitoring the back pressure of the filter during at least step e) and ceasing the spraying of the dry powder towards the inlet face of the filter when: r ｅｓｔ ≧r ｔａｒｇｅｔ During the ceremony, ρ ｔａｒｇｅｔ is a predetermined target backpressure for the filter; ρ ｅｓｔ is the estimated final back pressure of the filter; p ｅｓｔ is calculated by extrapolation of the measured backpressure data for the filter obtained during step f); A method wherein in step f) primary gas flow is maintained through the porous structure of the filter for a period of time after cessation of atomization of dry powder.

18. ρ ｅｓｔ 20. The method of claim 17, wherein V is calculated by extrapolating the measured backpressure data forward in time for Ts seconds, where Ts is the settling time.

19. The method is carried out on a coating apparatus, and the settling time, T ｓ The method of claim 18, wherein is a coating equipment dependent variable.

20. ρ ｅｓｔ 20. The method of claim 17, wherein A is calculated by curve fitting the measured backpressure data and extrapolating the fitted curve forward in time.

21. The method of claim 1 further comprising the step of firing the filter after loading with the dry powder.

22. The method of claim 1 further comprising coating the filter with a washcoat prior to step b).

23. 2. The method of claim 1, comprising providing a maximum loading of the filter of 10-40 g / l of dry powder, or providing a maximum loading of the filter of less than 10 g / l of dry powder.

24. The dry powder has a tap density of 1 to 3 g / cm3, or the dry powder has a tap density of 0.10 g / cm3 ３ The method of claim 1 having a tap density of less than

25. 10. The method of claim 1, wherein the dry powder has a d50 (by volume) of less than 10 microns.

26. 2. The method of claim 1, wherein in step d) a secondary gas flow separate from the primary gas flow is used to transport the dry powder from the reservoir to the spray device.

27. The method of claim 26 , wherein the secondary gas stream comprises a compressed gas stream.

28. 10. The method of claim 1, wherein the dry powder comprises or consists of a metal compound for forming a metal oxide upon pyrolysis.

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