WASHCOAT METHOD

Abstract

A method of washcoating a porous ceramic substrate, the method comprising: (i) pre-treating the substrate to form a pre-treated substrate; (ii) contacting the pre-treated substrate with a washcoat composition, wherein the washcoat composition comprises a washcoat solvent and a refractory material (such as a high surface area refractory material), wherein step (i) comprises pre-treating the substrate so as to substantially prevent ingress of the washcoat solvent into pores of the substrate and wherein the porous ceramic substrate comprises a plurality of channels and a plurality of micro-channels.

Claims

1. A method of washcoating a porous ceramic substrate, the method comprising: (i) pre-treating the substrate to form a pre-treated substrate; (ii) contacting the pre-treated substrate with a washcoat composition, wherein the washcoat composition comprises a washcoat solvent and a refractory material (such as a high surface area refractory material), wherein step (i) comprises pre-treating the substrate so as to substantially prevent ingress of the washcoat solvent into pores of the substrate and wherein the porous ceramic substrate comprises a plurality of channels and a plurality of micro-channels.

2. The method according to claim 1, wherein the ingress of the washcoat solvent into pores of the substrate is substantially prevented by reducing or preventing capillary action of the pores.

3. The method according to claim 1, wherein the refractory material (for example high surface area refractory material) comprises a ceramic material.

4. The method according to claim 1, wherein the refractory material (for example high surface area refractory material) comprises a metal oxide or precursor thereof.

5. The method according to claim 1, wherein the ingress of the washcoat solvent into pores of the substrate is prevented by increasing the hydrophobicity of the substrate.

6. The method according to claim 5, wherein step (i) comprises contacting the substrate with a pre-treatment composition, wherein the pre-treatment composition comprises a first pre-treatment solvent and a hydrophobic compound.

7. The method according to claim 6, further comprising removing the first pre-treatment solvent from the substrate.

8. The method according to claim 1, wherein the ingress of the washcoat solvent into pores of the substrate is prevented by substantially saturating the pores of the substrate with a second pre-treatment solvent.

9. The method according to claim 8, wherein step (i) comprises contacting the substrate with a second pre-treatment solvent so as to substantially saturate the pores of the substrate with the second pre-treatment solvent.

10. The method according to claim 1, wherein the pre-treated substrate is subjected to ultrasonication or to a pressure of 20 to 200 kPa upon contacting with the washcoat composition.

11. The method according to claim 1, further comprising removing the washcoat solvent from the substrate after contacting with the washcoat composition.

12. The method according to claim 1, further comprising applying a catalytic species or precursor thereof to the substrate.

13. A washcoated porous ceramic substrate obtained by the method of claim 1.

14. A washcoated porous ceramic substrate comprising a plurality of micro-channels coated with a solid washcoat layer, wherein the quantity of the washcoat layer is proportional to the volume of the micro-channels.

15. A method of manufacturing a filter, the method comprising manufacturing a washcoated porous ceramic substrate according to claim 1 and blocking at least some channels in the substrate.

16. A method of filtering, the method comprising manufacturing a filter according to claim 15 and passing a composition through the filter.

17. A filter comprising a washcoated porous ceramic substrate according to claim 13 or comprising a plurality of micro-channels coated with a solid washcoat layer, wherein the quantity of the washcoat layer is proportional to the volume of the micro-channels.

18. A method of manufacturing a catalytic convertor, the method comprising manufacturing a washcoated porous ceramic substrate according to claim 1 and optionally depositing a catalytic species or precursor thereof on the washcoat.

19. A method of catalytic conversion of pollutants, the method comprising manufacturing a catalytic convertor according to claim 18 and passing a pollutant composition through the catalytic convertor.

20. A catalytic convertor comprising a washcoated porous ceramic substrate according to claim 13 or comprising a plurality of micro-channels coated with a solid washcoat layer, wherein the quantity of the washcoat layer is proportional to the volume of the micro-channels.

21. A method of manufacturing an exhaust system, the method comprising: manufacturing a filter and incorporating the filter into an exhaust system; and/or manufacturing a catalytic convertor and incorporating the catalytic convertor into an exhaust system, wherein the filter is manufactured by a method comprising manufacturing a washcoated porous ceramic substrate according to claim 1 and blocking at least some channels in the substrate and wherein the catalytic convertor is manufactured by a method comprising manufacturing a washcoated porous ceramic substrate according to claim 1 and optionally depositing a catalytic species or precursor thereof on the washcoat.

22. An exhaust system comprising a filter and/or a catalytic convertor, wherein the filter comprises a washcoated porous ceramic substrate obtained by the method of claim 1 or comprises a plurality of micro-channels coated with a solid washcoat layer, wherein the catalytic converter comprises the washcoated porous ceramic substrate obtained by the method of claim 1 or comprises the plurality of micro-channels coated with a solid washcoat layer, and wherein the quantity of the washcoat layer is proportional to the volume of the micro-channels.

23. A method of manufacturing a product including an internal combustion engine, the method comprising manufacturing an exhaust system according to claim 21 and incorporating the exhaust system into a product including an internal combustion engine.

24. A product including an internal combustion engine comprising an exhaust system according to claim 22.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0155] For a better understanding of the invention, and to show how exemplary embodiments of the same may be carried into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

[0156] FIG. 1 shows a schematic representation of a method according to the first aspect of the invention.

[0157] FIG. 2 shows a schematic representation of a method according to the first aspect of the invention

[0158] FIG. 3 shows an SEM image of the washcoated substrate of Example 2;

[0159] FIG. 4 shows an SEM image of the washcoated substrate of Example 2; and

[0160] FIG. 5 shows an SEM image of the washcoated substrate of the comparative example.

DETAILED DESCRIPTION OF DRAWINGS

[0161] FIG. 1 shows a schematic representation of a method according to the first aspect of the invention in which the pre-treatment of the substrate prior to contacting with the washcoat composition comprises contacting the substrate with a second pre-treatment solvent so as to substantially saturate the pores of the substrate with the solvent.

[0162] FIG. 1 shows steps 1 to 6 of a method of the first aspect of the invention. In step 1, the substrate 10 is placed on a slab of porous material 11 soaked with water. The water is absorbed from the slab of porous material 11 into the substrate by capillary action, as shown by the arrows in FIG. 1. This provides a saturated substrate 12 in which the pores are substantially saturated with water, as shown in step 2 of FIG. 1.

[0163] In step 3 of FIG. 1, the saturated substrate 12 is contacted with a washcoat composition (14) comprising a washcoat solvent (such as water) 15 and a metal oxide (such as gamma-alumina) 16. In step 4 excess fluid is removed from the channels by applying compressed air 18, so as to provide a substrate in which the micro-channels are filled with the washcoat fluid as shown in step 5 of FIG. 1. In step 6 of FIG. 1, the washcoat solvent (water) is removed from the substrate by heating or drying, so as to provide a washcoated substrate 19 in which the washcoat has formed a layer 20 on the surfaces of the micro-channels.

[0164] FIG. 2 shows a schematic representation of a method according to the first aspect of the invention in which the pre-treatment of the substrate prior to contacting with the washcoat composition comprises contacting the substrate with a pre-treatment composition, wherein the pre-treatment composition comprises a first pre-treatment solvent and a hydrophobic compound.

[0165] FIG. 2 shows steps 1 to 8 of a method of the first aspect of the invention. In step 1, the substrate 30 is immersed in a pre-treatment composition 31. The pre-treatment composition 31 is absorbed into the substrate by capillary action, as shown by the arrows in step 1 of FIG. 2.

[0166] This provides a saturated substrate 32 in which the pores are substantially saturated with the pre-treatment composition, as shown in step 2 of FIG. 2.

[0167] In step 3 of FIG. 2, the substrate is heated so as to remove the first pre-treatment solvent and provide a dry, hydrophobic substrate 33 as shown in step 3 of FIG. 2.

[0168] In step 4 of FIG. 2, the dry hydrophobic substrate 33 is contacted with a washcoat composition 34 comprising a washcoat solvent (such as water) 35 and a metal oxide (such as gamma-alumina) 36. In step 5, pressure is applied to the substrate to ensure that the washcoat composition floods the micro-channels 37 of the substrate. When the pressure is released in step 6, the washcoat composition exits the micro-channels leaving a washcoat residue 38 on the surfaces of the micro-channels. In step 7, excess fluid is removed from the channels by applying compressed air 39. In step 8 of FIG. 2, the washcoat solvent (water) and hydrophobic compound are removed from the substrate by heating, so as to provide a washcoated substrate 40 in which the washcoat has formed a layer 41 on the surfaces of the micro-channels.

EXAMPLES

[0169] The invention will now be described with reference to the following non-limiting examples.

[0170] Scanning electron microscope (SEM) images were obtained using a Phenom ProX desktop Scanning electron microscope (SEM). The settings used were an acceleration voltage of 15 kV and the backscattered electron detector. SEM samples were prepared by breaking the washcoated sample to expose a region at the sample centre. No further changes to the sample were made before analysis.

[0171] The washcoat loading was calculated using the following equation:

[00001]$\left(\frac{{\mathrm{weight}}_{\mathrm{after}}-{\mathrm{weight}}_{\mathrm{before}}}{{\mathrm{weight}}_{\mathrm{before}}}\right)?100$

Example 1

[0172] A washcoat fluid was prepared by mixing boehmite and deionized water at a loading of 15 and 85 wt % respectively. The components were mixed in a vessel at a rate of 1500 rpm for 15 hours (until complete dispersion of the boehmite in water was achieved).

[0173] The substrate was immersed in a 95:5 (by weight) solution of ethanol and caprylic acid respectively, for 2 minutes. The substrate was then removed from the ethanol and caprylic acid mixture and dried at 80? C. for 15 minutes (to remove the ethanol).

[0174] The substrate was then weighed, and the weight recorded. The substrate was then submerged in the washcoat fluid in a sealed container connected to a source of compressed air. A pressure of 1 bar was applied for 20 seconds after the substrate was submerged in the washcoat fluid. The pressure was then released, the sample removed from the container and any remaining fluid evacuated from the substrate channels using compressed air. The substrate was then dried at a temperature of 80? C. for 1 hour (to remove the deionized water). After drying, the substrate was fired at 550? C. for 2 hours to convert the boehmite washcoat material to gamma-alumina. The substrate was then weighed to determine the washcoat loading.

Example 2

[0175] A washcoat fluid was prepared by mixing boehmite and deionized water at a loading of 15 and 85 wt % respectively. The components were mixed in a vessel at a rate of 1500 rpm for 15 hours (until complete dispersion of the boehmite in water was achieved).

[0176] The substrate was weighed, and the weight recorded. The substrate was then placed on a slab of porous aluminium oxide soaked with water. The substrate was left on the slab for a period of 15 minutes for complete wetting to occur. After 15 minutes the substrate was removed from the porous material and evacuated with compressed air (to remove any excess water in the channels). The substrate was then submerged in the washcoat fluid in a sealed container for 10 minutes. The substrate was then removed from the container and any remaining washcoat fluid was evacuated from the substrate channels using compressed air. The substrate was then dried at a temperature of 80? C. for 1 hour (to remove the deionized water). After drying, the substrate was fired at 550? C. for 2 hours to convert the boehmite washcoat material to gamma-alumina. The substrate was then weighed to determine the washcoat loading.

[0177] FIGS. 3 and 4 show the results of the washcoating method. FIGS. 3 and 4 show that there is a coating of washcoat within the micro-channels and on the inner surface without any plugs or cake layer formation. In particular, FIG. 3 shows that the micro-channels are coated.

[0178] The washcoat loading (g washcoat per g of substrate) was 2.2%.

COMPARATIVE EXAMPLE

[0179] The comparative example uses a conventional washcoating method to apply a washcoat dispersion to a ceramic substrate. This conventional washcoating method relies on the transfer of water from the washcoat fluid to the dry substrate through capillary forces.

[0180] A washcoat fluid was prepared by mixing boehmite and deionized water at a loading of 15 and 85 wt % respectively. The components were mixed in a vessel at a rate of 1500 rpm for 15 hours (until complete dispersion of the boehmite in water was achieved).

[0181] The substrate was weighed, and the weight recorded. The substrate was then submerged in the washcoat fluid in a sealed container. The substrate was left submerged in the washcoat fluid for 10 minutes. The substrate was removed from the container and any remaining fluid was evacuated from the substrate channels using compressed air. The substrate was then dried at a temperature of 80? C. for 1 hour to remove the deionized water. After drying, the substrate was fired at 550? C. for 2 hours to convert the boehmite washcoat material to gamma-alumina. The substrate was then weighed and the washcoat loading was calculated.

[0182] FIG. 5 shows the results of the conventional washcoating method. There is a cake layer of washcoat material that has been deposited on the inner fibre surface (walls of substrate channels), but the method failed to coat the micro-channels of the substrate.

[0183] The washcoat loading (g washcoat per g of substrate) was 2.5%.

[0184] Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0185] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0186] All of the features disclosed in this specification (including any accompanying claims), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0187] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0188] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.