JP2005279508A - Prior-to-drying pretreatment method of three-dimensional structure body, exhausted gas purification filter and production method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prior-to-drying pretreatment method for obtaining a honeycomb filter which reduces time required for drying a honeycomb filter to which a catalyst solution sticks, the honeycomb filter being free from the increase of pressure loss since its micropores are not covered and filled up by a catalyst, carrying a plurality of catalyst components which are homogeneously carried on it, and having a large catalyst-carrying area, so as to solve the problem that more time is required when a catalyst is carried on a three-dimensional structure body, and the pressure loss after the catalyst is carried on it greatly increases and the catalyst is not homogeneously carried on due to the movement of catalyst components in a catalyst solution; and also provide a method for manufacturing the honeycomb filter and a catalyst-carried exhausted gas purification filter obtained by said manufacturing method. <P>SOLUTION: In order to prevent a catalyst solution 9 from covering and filling the micropores 8 of a three-dimensional structure body, the micropores 8 are degassed by subjecting the three-dimensional structure body to vacuum processing or the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a three-dimensional structure pre-drying treatment method, a method for producing an exhaust gas treatment filter including the pre-drying treatment step, and a catalyst-supported exhaust gas treatment filter produced by the production method.

  In recent years, regulations and nitrogen oxides contained in exhaust gas discharged from an internal combustion engine have been gradually tightened for environmental protection and health reasons.

Conventionally, in order to collect and purify particulates and nitrogen oxides released into the atmosphere, a method of attaching a ceramic or metal honeycomb filter in the middle of the exhaust path has been generally proposed. More recently, as shown in Patent Document 1, an attempt has been made to support a catalyst for exhaust gas purification on a ceramic honeycomb structure and burn particulates with the heat of exhaust gas.
JP 2003-190793 A

  However, when the catalyst is supported on the honeycomb filter, if the catalyst is dried while covering the fine pores of the filter inner partition walls, the remaining catalyst covers and closes the fine pores. There was a problem that the loss would increase greatly. In addition, when the honeycomb filter to which the catalyst solution is attached is air-dried, the catalyst solution covers and closes the fine pores of the filter inner partition wall, which makes it difficult for air to pass and takes time to dry. Furthermore, as drying takes time, the catalyst component in the catalyst solution moves, and there is a problem that the amount of catalyst supported is distributed.

  Therefore, the present invention can not only shorten the drying time of the honeycomb filter to which the catalyst solution is adhered, but also suppresses an increase in pressure loss because the fine pores are not covered with the catalyst, and a plurality of catalysts It is an object of the present invention to provide a drying pretreatment method and a production method for obtaining a honeycomb filter in which components are uniformly supported and a catalyst supporting area is large. Another object of the present invention is to provide a catalyst-carrying exhaust gas purification filter obtained by the production method.

  The drying pretreatment method of the present invention is characterized in that the fine pores in the three-dimensional structure are not covered and blocked before the three-dimensional structure to which the catalyst solution is adhered is dried. As a result, the fine holes, particularly the through-holes, are not covered, so that the gas passing through the three-dimensional structure can easily pass through when drying by ventilation, thereby shortening the drying time. it can. Furthermore, by shortening the drying time, movement of the catalyst component can be prevented and the catalyst can be supported uniformly. Moreover, it can suppress that the pressure loss of the three-dimensional structure after drying raises. In addition, the catalyst solution can be spread to the inside of the micropores to increase the catalyst solution adhesion surface area.

  In addition, the drying pretreatment method of the present invention is characterized in that the inside of the micropores in the three-dimensional structure is degassed. As a result, when bubbles are removed from the micropores, the catalyst solution covering and closing the micropores can be removed, and the gas passing through the three-dimensional structure can easily pass through when drying by ventilation. , Drying time can be shortened. Furthermore, by shortening the drying time, movement of the catalyst component can be prevented and the catalyst can be supported uniformly. Moreover, it can suppress that the pressure loss of the three-dimensional structure after drying raises. In addition, the catalyst solution can be spread to the inside of the micropores to increase the catalyst solution adhesion surface area.

  The drying pretreatment method of the present invention is characterized in that the three-dimensional structure is decompressed. As a result, the catalyst solution covering and closing the micropores can be removed, and the gas passing through the three-dimensional structure can be easily passed during the ventilation drying, and the drying time can be shortened. . Furthermore, by shortening the drying time, movement of the catalyst component can be prevented and the catalyst can be supported uniformly. Moreover, it can suppress that the pressure loss of the three-dimensional structure after drying raises. In addition, the catalyst solution can be spread to the inside of the micropores to increase the catalyst solution adhesion surface area.

  The drying pretreatment method of the present invention is characterized in that the pressure is gradually reduced so that the catalyst solution does not ooze out from the three-dimensional structure. Thereby, the inside of a micropore can be deaerated, without reducing a catalyst liquid adhesion amount.

  Further, the drying pretreatment method of the present invention is characterized in that the temperature of the catalyst solution adhering to the three-dimensional structure is not set to a temperature at which the catalyst contained in the catalyst solution is deposited. Thereby, even if the catalyst contained in the catalyst liquid is a plurality of components, it is possible to perform a pretreatment without any one of the catalysts being deposited and the catalyst liquid components becoming non-uniform.

  In the drying pretreatment method of the present invention, the three-dimensional structure is an exhaust gas purifying filter. Thereby, exhaust gas containing harmful substances can be effectively collected and removed.

  The drying pretreatment method of the present invention is characterized in that the exhaust gas purifying filter is a metal or ceramic porous body. Thereby, the pre-drying process of a metal or ceramic porous body filter can be performed effectively.

  In addition, the exhaust gas purification filter manufacturing method of the present invention includes a step of performing the pre-drying treatment. Thereby, since drying time can be shortened, the time concerning manufacture can be shortened.

  In addition, the catalyst-carrying exhaust gas purification filter of the present invention is obtained by treating the exhaust gas purification filter to which a catalyst solution is adhered in the above production method. As a result, an increase in pressure loss is suppressed because the fine pores are not covered with the catalyst, and a catalyst-carrying exhaust gas purification filter having a plurality of catalyst components uniformly supported and a large catalyst-carrying area is obtained. be able to.

  ADVANTAGE OF THE INVENTION According to this invention, drying time can be shortened, Furthermore, movement of a catalyst component can be prevented by shortening drying time, and the drying pre-processing method which can carry | support a catalyst uniformly can be provided. .

  Further, according to the present invention, it is possible to suppress an increase in pressure loss of the three-dimensional structure after drying, and to spread the catalyst liquid to the inside of the micropores, thereby increasing the surface area of the catalyst liquid adhesion. A drying pretreatment method can be provided.

  Moreover, according to this invention, the drying pre-processing method which can deaerate the inside of a micropore can be provided, without reducing the catalyst liquid adhesion amount.

  Further, according to the present invention, it is possible to provide a drying pretreatment method in which any one catalyst is deposited and the catalyst liquid component does not become non-uniform even when the catalyst contained in the catalyst liquid is a plurality of components. .

  Moreover, according to this invention, the filter manufacturing method for exhaust gas purification which shortened drying time can be provided.

  Further, according to the present invention, the catalyst-supported exhaust gas having a large catalyst support area in which the increase in pressure loss is suppressed because the micropores are not covered with the catalyst, and a plurality of catalyst components are supported uniformly. A purification filter can be provided.

  The drying pretreatment method of the present invention is characterized in that the fine pores in the three-dimensional structure are not covered and blocked before the three-dimensional structure to which the catalyst solution is adhered is dried.

  The catalyst solution shown here is a solution obtained by dissolving or dispersing a catalyst in a solvent. Two or more components may be mixed in the catalyst. The solvent may be a polar solvent such as water or alcohol, or a nonpolar solvent. Further, there may be a dispersant or a surfactant for dispersing the catalyst in the catalyst solution. If the surface tension of the catalyst solution is small, it becomes difficult for the catalyst solution to cover and close the micropores in the three-dimensional structure. Therefore, an additive for reducing the surface tension may be added.

  Examples of the method for adhering the catalyst solution include impregnating the catalyst solution with the three-dimensional structure, spraying the catalyst solution, and applying the catalyst solution with a brush or a roller, but are not limited to these methods. It is not something.

  The three-dimensional structure shown here is not particularly limited as long as it has a three-dimensional structure and can be attached with a catalyst solution.

  Examples of the micropores shown here include, but are not limited to, hollows and through-holes that are often found in porous bodies.

  In addition, the drying pretreatment method of the present invention is characterized in that the inside of the micropores in the three-dimensional structure is degassed.

  As a degassing method, a method of pressurizing or depressurizing in a container capable of pressurization and depressurization can be considered, but it is not limited to these methods.

  The drying pretreatment method of the present invention is characterized in that the three-dimensional structure is decompressed.

  As a method of depressurization, there is a method of depressurizing by putting a three-dimensional structure adhering to a catalyst solution into a depressurizable container and sucking air in the container with a vacuum pump. However, the method is limited to this method. is not.

  The drying pretreatment method of the present invention is characterized in that the pressure is gradually reduced so that the catalyst solution does not ooze out from the three-dimensional structure.

  When the degree of vacuum increases, gas (usually air) escapes from the micropores in the three-dimensional structure, and at that time, the catalyst solution covering the surface of the micropores oozes out. If the exuded catalyst liquid accumulates in the lower part, the pressure loss in the lower part will increase, making it difficult to dry during ventilation drying. Also, it will be distributed in the catalyst loading of the three-dimensional structure after drying. This causes problems such as being able to

  In order to prevent the catalyst solution from oozing out, the degree of vacuum may be gradually increased, and when the catalyst solution is about to ooze out, leakage and lowering of the degree of vacuum may be repeated.

  Further, the drying pretreatment method of the present invention is characterized in that the temperature of the catalyst solution adhering to the three-dimensional structure is not set to a temperature at which the catalyst contained in the catalyst solution is deposited.

  This is particularly important when a multi-component catalyst is mixed in the catalyst solution. When the temperature of the catalyst solution reaches a temperature at which the catalyst is deposited, the catalyst solution is deposited in descending order of the solubility of the catalyst solution in the solvent. Then, a layer for each catalyst component is formed, and the catalyst having the highest solubility in the lowermost layer, that is, the solvent, looks like being coated with a catalyst having a low solubility and cannot function as a catalyst.

  Some salts, such as calcium hydroxide, that become less soluble as the temperature increases require that the temperature not be too high. When pretreatment by reduced pressure is performed, the evaporation of the solvent removes the heat of vaporization and lowers the temperature, so care must be taken with many salts whose solubility decreases as the temperature decreases.

  In the drying pretreatment method of the present invention, the three-dimensional structure is an exhaust gas purifying filter.

  Exhaust gas purification filters can purify various exhaust gases such as engines of transport engines such as automobiles, cultivators, ships and trains, fixed engines such as generators, and firing furnaces, incinerators, boilers, etc. it can. Examples of the engine include, but are not limited to, a gasoline engine and a diesel engine.

  Examples of the shape of the exhaust gas purifying filter include, but are not limited to, a cylindrical shape, a prismatic shape, a rectangular parallelepiped shape, and a cubic shape.

  The drying pretreatment method of the present invention is characterized in that the exhaust gas purifying filter is a metal or ceramic porous body.

  As the metal, a relatively inexpensive and high melting point single metal such as iron, copper, nickel, chromium, titanium, or a metal material such as an alloy thereof can be used, but is not limited thereto. As the ceramic porous body, mullite, cordierite, aluminum titanate, silica, alumina, silica alumina, silicon carbide, silicon nitride and the like can be used, but are not limited thereto.

  In addition, the exhaust gas purification filter manufacturing method of the present invention includes a step of performing the pre-drying treatment.

  After impregnating the exhaust gas purification filter into the catalyst solution or spraying the catalyst solution onto the exhaust gas purification filter, the catalyst solution is attached to the exhaust gas purification filter, and after the drying pretreatment of the present invention, Drying is performed by a method such as drying, ventilation drying, reduced pressure drying, heat drying, pressure drying, freeze drying, and then calcined at an appropriate temperature according to the catalyst if necessary.

  In addition, the catalyst-carrying exhaust gas purification filter of the present invention is obtained by treating the exhaust gas purification filter to which a catalyst solution is adhered in the above production method.

  By producing by the above production method, the increase in pressure loss is suppressed because the fine pores are not covered with the catalyst, and a plurality of catalyst components are uniformly supported, and the catalyst support having a large catalyst support area is supported. An exhaust gas purifying filter can be obtained. When this is installed in the exhaust path of the internal combustion engine, an increase in pressure loss is suppressed, so the load on the engine is reduced, and the exhaust gas can be efficiently purified because the catalyst carrying area is large.

  Further, the catalyst-carrying exhaust gas purification filter becomes an exhaust gas purification filter having various functions by changing the type of catalyst. For example, a combustion catalyst for burning particulates contained in diesel exhaust gas, an oxidation catalyst for oxidizing NO and CO and raising the exhaust gas temperature by oxidation heat, an occlusion catalyst for storing NOx and SOx, etc. There is. When combined with a heater for raising exhaust gas temperature or an oxidation catalyst-carrying exhaust gas purification filter in the front stage of the particulate combustion catalyst-carrying exhaust gas purification filter, and a downstream catalyst-carrying exhaust gas purification filter in the subsequent stage, the exhaust gas is further increased. Can be purified.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention should not be construed as being limited to the following description.

(Embodiment 1)
As shown in FIGS. 1 and 2, the decompression device 1 includes a container 2 that can be decompressed, a vacuum pump 3, a leak valve 4, and a thermocouple 5. The DPF 6 with the catalyst solution attached was placed in the depressurizable container 2, and the thermocouple 5 was inserted into the cell of the DPF 6 with the catalyst solution attached.

  In the above configuration, the inside of the depressurizable container 2 can be depressurized by sucking the air in the depressurizable container 2 with the vacuum pump 3. If the degree of vacuum increases rapidly, the catalyst solution may ooze out from the DPF 6 to which the catalyst solution adheres. Therefore, it is necessary to adjust the degree of vacuum by opening and closing the leak valve 4. In addition, since the temperature in the cell can be measured by inserting the thermocouple 5 into the cell of the DPF 6 to which the catalyst solution is adhered, pretreatment may be performed so as not to lower the temperature at which the catalyst is deposited. it can.

(Example 1)
As shown in FIGS. 3 and 4, a cylindrical diesel particulate filter (DPF) having a diameter of 5.66 inches and a length of 6 inches is added to an aqueous solution in which a plurality of catalyst components such as copper sulfate pentahydrate are dissolved. After impregnation, the excess liquid was removed by allowing to stand for about 1 hour. The DPF 6 to which the catalyst solution is attached is placed in a container 2 that can be depressurized, the thermocouple 5 is inserted into the center and outer peripheral cells of the DPF, the vacuum pump 3 is turned on, and the leak valve 4 is kept from leaking out the catalyst solution. Was gradually closed, and pressure reduction treatment was started to cover the fine holes and prevent clogging. When water begins to evaporate, the heat of vaporization is deprived, and the temperature starts to drop from the outer periphery. Therefore, by carefully checking the temperature of the thermocouple 5 so that the temperature of the catalyst solution does not drop too much, the leak valve 4 is adjusted gradually. Increased the degree of vacuum. The operation for raising the degree of vacuum was performed for a while, and when the temperature in the outer peripheral cell decreased to 10 ° C., the leak valve 4 was fully opened, and the pretreatment for drying was finished. FIG. 4 shows the inner wall 7 of the DPF cell to which the catalyst solution is attached.

  As a result, a DPF in which the fine holes 8 in the DPF are not covered with the catalyst liquid 9 and a plurality of catalyst components are uniformly attached is obtained.

(Example 2)
An aqueous solution in which a plurality of catalyst components such as copper sulfate pentahydrate is dissolved is impregnated with a cylindrical DPF having a diameter of 5.66 inches and a length of 6 inches, and then left to stand for about 1 hour to remove excess liquid. Removed. Then, the temperature in the center cell of DPF6 to which the catalyst liquid adhered at the time of drying when dry pretreatment was performed by the method described in Example 1 and when pretreatment was not performed was measured. The temperature in the dryer was increased from 25 ° C. to 150 ° C. at 5 ° C./min, and a fan was further provided to circulate the air in the dryer.

  From FIG. 5, it can be seen that the temperature is more likely to increase in the case of pre-drying treatment. This is because the catalyst solution covering and closing the fine holes 8 can be removed by performing the pretreatment to prevent the catalyst holes from covering and closing the fine holes of the DPF, thereby suppressing an increase in pressure loss. This is probably because hot air was easier to pass through.

(Example 3)
An aqueous solution in which a plurality of catalyst components such as copper sulfate pentahydrate is dissolved is impregnated with a cylindrical DPF having a diameter of 5.66 inches and a length of 6 inches, and then left to stand for about 1 hour to remove excess liquid. Removed. Thereafter, when the pre-drying treatment was performed by the method described in Example 1 and when the pre-treatment was not performed, the DPF 6 to which each catalyst solution was adhered was dried and calcined, and then the pressure loss was measured.

  As shown in FIG. 6, the measurement method adjusts the volume of the wind sent from the blower 10 by the volume adjustment handle 11 and sends it to the DPF attachment pipe 12. After firing, the pressure loss on the inlet side of the DPF 13 is read from the manometer 14. The measurement was performed by reading the pressure loss (unit: kPa) when the flow rate was 100, 150, 200, 250, 300 m ↑ 3 / h.

  Table 1 is a graph of the DPF center temperature. From Table 1, it can be seen that the pressure loss is lower when the pre-drying treatment is performed. This is because the catalyst liquid 9 covering and closing the fine holes 8 can be removed by performing the pretreatment to prevent the catalyst liquid 9 from covering and closing the fine holes 8 of the DPF. This is thought to be because the rise was suppressed.

Example 4
An aqueous solution in which a plurality of catalyst components such as copper sulfate pentahydrate is dissolved is impregnated with a cylindrical DPF having a diameter of 5.66 inches and a length of 6 inches, and left to stand for about 1 hour to remove excess liquid. Removed. Thereafter, when the drying pretreatment was performed by the method described in Example 1 and when the pretreatment was not performed, the DPF 6 to which each catalyst solution was adhered was dried and calcined, and then the combustion activation temperature (BPT) for the particulates was measured. . The measurement was performed using an engine bench, and the exhaust gas temperature was increased from 250 ° C. to 30 ° C. and kept at each temperature for 40 minutes, and the pressure loss at each temperature was measured. From this pressure loss value, the temperature when the pressure increase rate becomes 0, that is, the temperature when the particulate deposition rate and the particulate combustion rate are equal, is calculated, and the temperature at that time is expressed as BPT (unit: ° C).

  Table 2 is a table of BPT measurement results. From Table 2, it can be seen that the BPT is lower in the case of the pre-drying treatment, that is, the activity is higher. This is presumably because the catalyst was supported uniformly and over a wide range as a result of the pretreatment for preventing the catalyst solution 9 from covering and closing the fine holes 8 of the DPF.

  The drying pretreatment method of the present invention is useful because it can shorten the drying time of the three-dimensional structure to which the catalyst solution is adhered.

  In the drying pretreatment method of the present invention, the increase in pressure loss is suppressed because the fine pores are not covered with the catalyst, and a plurality of catalyst components are uniformly supported, and the catalyst supporting area is large. A catalyst-supporting exhaust gas purification filter can be provided and is useful.

Schematic cross-sectional view of the decompression device in Embodiment 1 of the present invention Thermocouple insertion position schematic diagram in Embodiment 1 of the present invention Schematic cross-sectional view of the decompression device in Example 1 of the present invention Enlarged schematic view of the inner wall of the DPF cell in Example 1 of the present invention Graph of DPF center temperature in Example 2 of the present invention Schematic of the pressure loss measuring device in Example 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Depressurization device 2 Depressurizable container 3 Vacuum pump 4 Leak valve 5 Thermocouple 6 DPF with catalyst solution attached
7 DPF cell inner wall to which catalyst solution adheres 8 Fine hole 9 Catalyst solution 10 Blower 11 Air flow rate adjustment handle 12 DPF attachment pipe 13 DPF after firing
14 Manometer

Claims (9)

A drying pretreatment method for a three-dimensional structure, characterized in that, before the three-dimensional structure to which the catalyst solution is adhered is dried, the micropores in the three-dimensional structure are covered and not blocked. The method for pre-drying a three-dimensional structure according to claim 1, wherein the inside of the micropores in the three-dimensional structure is degassed. The method for pre-drying a three-dimensional structure according to claim 1 or 2, wherein the three-dimensional structure is decompressed. The method for pre-drying a three-dimensional structure according to any one of claims 1 to 3, wherein the pressure is gradually reduced so that the catalyst solution does not ooze out of the three-dimensional structure. 5. The three-dimensional structure drying pretreatment method according to claim 1, wherein the temperature of the catalyst solution adhering to the three-dimensional structure is not set to a temperature at which the catalyst contained in the catalyst solution is deposited. 6. The three-dimensional structure pre-drying method according to claim 1, wherein the three-dimensional structure is an exhaust gas purification filter. The method for pre-drying a three-dimensional structure according to any one of claims 1 to 6, wherein the exhaust gas purifying filter is a metal or ceramic porous body. A method for producing an exhaust gas purifying filter, comprising a step of performing the pre-drying treatment according to claim 1. 9. A catalyst-supported exhaust gas purification filter, which is obtained by treating the exhaust gas purification filter to which a catalyst solution is adhered in the production method according to claim 8.

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