JP3743682B2 - Method for anodizing structure and method for producing catalyst structure using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an anodizing method, and more particularly, to an anodizing method capable of anodizing the inside of a structure, which has been impossible in the past, and a method for producing a catalyst structure using the method.
[0002]
[Prior art]
Conventionally, anodization is usually performed on the outer surface. When anodizing the inner surface of a tubular body, a metal wire serving as a cathode must be installed inside the tubular body, which is complicated. In addition, advanced technology was required. Accordingly, the size and shape of the object when the inner surface is anodized naturally must be constrained, and conventionally, for example, a structure having a deep hole (5 cm or more) and a narrow hole (with a radius of 5 mm or less). As for, the inner surface could not be anodized because it was technically difficult to insert the cathode.
Therefore, in such a case, it is necessary to use a metal plate that has been anodized in advance and process the structure with the anodized surface as the inner surface, so that the upper anodized surface, which is troublesome twice, is not damaged or soiled. It had to be managed so that it was complicated.
[0003]
[Problems to be solved by the invention]
Therefore, as a result of intensive studies on anodizing the inside of the structure as it is, the present inventors have found that when an electrolyte is passed through the structure that becomes the anode, There is no need to provide a cathode, and by passing an electric current between the cathode and the cathode provided outside the structure, the inner surface of the structure of any shape can be formed as long as the inside is a metal that can be anodized. The present inventors have found that it can be anodized and have reached the present invention.
[0004]
Accordingly, a first object of the present invention is to provide a method for anodizing the inside of an arbitrarily shaped structure having an anodizable surface therein.
The second object of the present invention is to provide a method for producing a high-performance catalyst structure by anodizing the inside of a structure having a shape and structure as a catalyst reactor and then supporting the catalyst.
[0005]
[Means for Solving the Problems]
The above-mentioned objects of the present invention are a method for anodizing the inner surface of a structure having an anodizable surface therein, and flowing an electrolyte into the structure, outside the structure, In the vicinity of the inlet and outlet for the electrolyte of the structure, a cathode is arranged in parallel with the outlet and inlet surfaces of the structure so that the electrolyte can smoothly enter and exit the passage of the structure. The present invention has been achieved by a method for anodizing a structure, and a method for producing a catalyst structure using the method, wherein a current is passed between the structure serving as the cathode and the anode.
[0006]
The inner surface of the structure in the present invention is not limited as long as it can be anodized, but generally contains aluminum alone, a metal provided with an aluminum layer, or 60% by weight or more of aluminum. An alloy such as duralumin.
In this case, the surface shape may be any shape, and may be a plate shape, a wave shape, a ribbon shape, a tubular shape, a honeycomb shape, or a combination thereof depending on the application or usage method.
In addition, the shape of the structure may be any shape as long as it has an outlet and an inlet for smoothly flowing the electrolytic solution, and can be processed into an S shape, a U shape, or the like according to the application. From the viewpoint of a catalytic reaction chamber, an elongated structure is preferable.
[0007]
The cathode used in the present invention can be appropriately selected from those known as anodic oxidation cathodes. The cathode is outside the structure and in the vicinity of the inlet and outlet of the structure serving as a passage for the electrolyte so that the electrolyte is parallel to the outlet surface and the inlet surface of the structure. it arranged so as to be smoothly out of the passageway of the structure.
[0008]
In the present invention, for example, when the electrolytic solution is circulated inside a narrow honeycomb structure, it is accompanied by anodization that the structure is arranged in the electrolytic solution in the vertical direction or in a direction slightly inclined from the vertical. It is preferable because the electrolyte solution can be circulated by natural convection based on heat generation or generated gas (see FIG. 1). As the inclination of the structure from the vertical direction increases, the natural convection of the electrolyte is less likely to occur. In such a case, the electrolyte may be forced to flow into the structure using an appropriate reflux device. It is preferable to let it flow out.
[0009]
The flow rate of the electrolytic solution in the present invention varies depending on the length of the structure, the current density, the acid concentration, and the like, so it cannot be clearly stated, and an appropriate condition may be selected for the formation of the target structure. . For example, when an anodized film having a uniform film thickness is formed, the flow rate may be adjusted so that the difference between the temperature near the inlet and the temperature near the outlet is within 2 ° C. In addition, when the film thickness distribution is formed from the inlet toward the outlet, the flow rate may be adjusted so as to generate a temperature difference between the vicinity of the inlet and the vicinity of the outlet.
[0010]
The electrolyte used in the present invention can be appropriately selected from known electrolytes used for anodization, such as sulfuric acid, chromic acid, oxalic acid, phosphoric acid, etc., but is easy to handle and control of anodization. From this viewpoint, oxalic acid is most preferable.
The acid concentration can be appropriately selected within the range of 1 wt% to 10 wt%, the liquid temperature is 5 ° C. to 45 ° C., and the current density is within the range of 10 A / m ^{2 to} 1,000 A / m ^2. It is preferable that the liquid temperature is 15 ° C. to 25 ° C., and the current is 50 A / m ^{2 to} 100 A / m ² .
By anodizing for 30 minutes to 50 hours under the conditions described above, an anodized film of 30 μm to 500 μm can be freely formed on the inner surface of the structure.
[0011]
In the catalyst structure of the present invention, the structure is anodized as it is by the method of the present invention to form an anodized film inside, and then hydrated to increase the BET surface area of the film surface. After carrying out, or simultaneously with a hydration process, it can manufacture by carrying out a catalyst carrying process and then performing a calcination process.
The hydration treatment is preferably performed by immersing the structure in a treatment solution for 15 minutes to 3 hours.
[0012]
If the hydration treatment is carried out with water or steam, it is necessary to carry out the catalyst loading treatment in the next step. If the hydration treatment is carried out with an aqueous solution in which the water-soluble salt of the catalyst is dissolved, the catalyst loading treatment is performed simultaneously with the hydration treatment. It can be performed. The hydration treatment is preferably performed at 5 ° C to 80 ° C. Moreover, as a subsequent baking process, it is preferable to use the method of air baking at 300 to 500 degreeC.
[0013]
As an aqueous solution containing a soluble salt of the catalyst, for example, a solution having a pH of about 11 including a nitrate solution such as platinum group metal, manganese, nickel, cobalt, or a normal chloride solution is preferable.
The usual catalyst loading is in the range of 0.1 g metal / m ² to 15 g metal / m ² , and from the industrial point of view, 1 g metal / m ² is particularly preferable. In order to use for a long period of time, the catalyst loading amount may be increased.
Note that, unlike the case of anodization, the treatment liquid only needs to be present inside the structure during the hydration treatment or the catalyst support treatment, and it is not essential to flow.
[0014]
【The invention's effect】
According to the present invention, since the structure can be manufactured in advance and anodized later, the quality control during the manufacture of the structure can be greatly reduced, and thus the total cost of the catalyst structure can be reduced. Can also be reduced.
[0015]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this.
[0016]
Example 1.
A JIS-A1050 standard aluminum plate having a width of 10 cm, a depth of 10 cm, and a thickness of 0.3 mm was processed into a corrugated shape having a height of 1.2 cm, and this was stacked in nine layers to obtain a structure having corrugated fins inside. (See FIG. 2). The obtained structure was washed in a 20 wt% aqueous sodium hydroxide solution for 3 minutes and then pretreated by neutralizing in a 30 wt% nitric acid aqueous solution for 1 minute. Subsequently, the current density was set to 100 A / m ² in an aqueous oxalic acid solution of 3% by weight at 20 ° C., and anodization was performed for 8 hours. The obtained structure was cut, and the thickness of the anodized film formed on the surface of the wavy fin inside the structure was measured and found to be about 100 μm.
[0017]
Example 2
Anodization was performed under exactly the same conditions as in Example 1 except that oxalic acid used in Example 1 was changed to sulfuric acid.
In the case of energization amount 800 Ah / m ^2, by the above process, as in Example 1, it was confirmed that anodic oxide film having a thickness of 100μm is obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram in which electrolyte is circulated by natural convection based on heat generated by anodization and generated gas.
FIG. 2 is a conceptual diagram of a structure having corrugated fins in which corrugated aluminum plates having a height of 1.2 cm are stacked in nine layers.

Claims (4)

A method of anodizing an inner surface of a structure having an anodizable surface therein, wherein an electrolyte is flowed into the structure, and the outside of the structure is an inlet and an outlet for the electrolyte of the structure In the vicinity of the structure, a cathode is disposed so as to be parallel to the exit surface and the entrance surface of the structure and so that the electrolyte can smoothly enter and exit the passage of the structure, and the structure becomes the cathode and the anode. A method for anodizing a structure, comprising passing an electric current between the bodies.   The anodizing method according to claim 1, wherein the structure has an elongated shape.   The anodizing method according to claim 1, wherein the structure is a honeycomb structure, and at least the surface of the honeycomb is an anodizable surface.   The structure anodized inside by the method according to claim 1 is hydrated using water at 5 ° C to 80 ° C, and then calcined at 300 ° C to 500 ° C. A method for producing a catalyst structure, wherein the catalyst is supported on an anodized film inside the structure by dipping in a solution containing a salt.

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