JP2828359B2 - Method for producing vanadium oxide having fiber structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing vanadium (V) oxide, and more particularly to a method for producing a catalyst having a large specific surface area, such as a reduction reaction of nitrogen oxide or an oxidation reaction of saturated hydrocarbon. The present invention relates to a method for producing a vanadium oxide having a fiber structure to contribute to the vanadium oxide.

[0002]

2. Description of the Related Art Today, vanadium oxide is used as a catalyst for chemical reactions in many fields. Reduction reaction of nitrogen oxides in flue gas generated during combustion of fossil fuels,
A reaction for producing maleic anhydride by oxidizing a hydrocarbon having 4 carbon atoms or an oxidation reaction of a gas containing ammonia into N ₂
Such as decomposing reaction in H ₂ O and is a typical reaction example.

In many cases, the method of reducing nitrogen oxides is based on the method disclosed in US Pat. No. 4,048,112, and selectively reduces nitrogen oxides in the presence of ammonia and a vanadium-based catalyst. Ways have been tried. In this case, as a catalyst, vanadium oxide supported on anatase titanium oxide or vanadium oxide
Mixtures of oxides such as u, Zn, and Sn are used, and various attempts have been made on carriers to increase the surface area. For example, U.S. Pat.
No. 6,089 proposes a method for producing a catalyst having a large surface area and a small bulk specific gravity by premixing alkoxides of titanium and silicon and adding the alkoxide mixture to a catalyst medium to form a precipitate of silica-titania. Have been. Also, U.S. Pat. No. 4,188,365 discloses a catalyst consisting of an average particle size of the catalytic metal oxide is deposited thereon and molded carrier made of TiO ₂ and clay 0.1 100 microns, for example, vanadium oxide . In this case, it is suggested that the fibrous or porous molded carrier is more effective.

On the other hand, vanadium-phosphorus oxides are also effective as catalysts for producing maleic anhydride by gas-phase oxidation of C4 paraffinic or olefinic hydrocarbons such as butane and butene. Research and application examples are increasing. For example, a crystalline compound having a composition of (VO) ₂ P ₂ O ₇ is a typical example. Usually, this catalyst reacts V ₂ O ₄ with phosphoric acid to form (VO) ₂ H ₄
After P ₂ O ₉ is synthesized, it is obtained by thermal decomposition in an atmosphere such as nitrogen. More practically, these catalysts are finely pulverized to a particle diameter of 1 μm or less using, for example, a ball mill, and then suspended in water to form an aqueous slurry, which is spray-dried and calcined and used as a fluidized bed. However, although the catalyst obtained in this way can increase the surface area by being finely divided, it has poor abrasion resistance when used as a fluidized bed due to the problem of mechanical strength, and withstands actual industrial operation. Can not do. For this reason, it has been proposed that solid particles obtained by spray drying are formed into pellets or other shapes and used as a fixed-bed catalyst. However, in this case, problems such as a decrease in the surface area of the catalyst occur.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a vanadium oxide having a large surface area desired for such a vanadium-based catalyst.
In other words, there is no need for special treatment for increasing the surface area such as making the substrate or the carrier finer or making the surface porous, and the substrate or the carrier surface is coated with a fibrous structure of vanadium oxide. The purpose of the present invention is to provide a solution to the problems of vanadium catalysts.

[0006]

According to the present invention, there is provided a method for producing a vanadium oxide film, comprising: a treatment solution containing a vanadium oxide and fluorine, wherein the vanadium oxide is in a supersaturated state; And depositing a vanadium oxide film on the surface of the substrate, followed by heat treatment at a temperature of 200 ° C. or more.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The processing solution in which the vanadium oxide used in the present invention is in a supersaturated state is, for example, the following (a) or (b)
Can be prepared.

(A) An additive such as a metal having a higher ionization tendency than hydrogen, KI, or AlCl _{3 is} added to a liquid obtained by substantially saturating vanadium oxide with hydrofluoric acid (HF).
A metal halide such or _{H 3 BO 3,, NH 4} OH
A method of adding a compound having high reactivity with HF, such as HF.

(B) A method of dissolving vanadium fluoride in water until it is substantially saturated, and then adding an additive thereto as in (a).

The concentration of hydrofluoric acid is preferably 0.1 to 4.0 mol / l. The additive to be added to the substantially saturated solution prepared in (a) to (b) is desirably added at a rate of 0.01 to 10 mol per 1 mol of vanadium in the treatment liquid. If the amount of the additive is less than 0.01 mol, the precipitation is slow due to the low degree of supersaturation of the vanadium oxide, and the base material is sometimes etched because the formation of the coating takes time. On the other hand, if the proportion of the additive is more than 10 mol, the supersaturation of the vanadium oxide is too high,
Precipitation of vanadium oxides occurs preferentially in the processing solution.

The substrate on which the vanadium oxide film is formed may be in any form, such as powders, fibrous materials, cylinders, plates or amorphous materials used as fluidized bed catalysts or fixed bed catalysts. However, it is necessary not to contain an alkali metal such as Na and K. That is, when the base material contains an alkali metal, when the alkali metal is brought into contact with the processing solution, the alkali metal dissolves as ions in the processing solution, and the ionized metal is contained in the vanadium oxide. And vanadium oxide having a fibrous structure cannot be obtained. According to the study of the present inventor, for example, when soda lime glass containing an alkali component is used for the substrate, the obtained vanadium oxide has a layered structure, and this structure does not change even when subjected to heat treatment. On the other hand, if borosilicate glass or alumina plate is used as the base material, the film having a granular structure immediately after deposition (a film composed of fine particles), but the fiber is subjected to heat treatment at 200 ° C. or more. A structure can be obtained, and a fibrous or acicular vanadium oxide coating can be obtained. In addition, as a similar experiment, after adding an alkali fluoride compound such as LiF, NaF, or KF to the treatment liquid, a glass containing no alkali was immersed as a substrate to form a vanadium oxide on the substrate. However, the obtained film remains in a layered structure even when subjected to heat treatment, and a target vanadium oxide film cannot be obtained if alkali metal ions are present in the processing solution.

In the present invention, the treatment liquid is brought into contact with the substrate to deposit a vanadium oxide film on the surface of the substrate. The temperature of the treatment liquid at this time is preferably in the range of 5 to 40 ° C. When the temperature of the processing solution is 5 ° C. or lower, the deposition rate of the vanadium oxide film is slow and not practical. On the other hand, at 40 ° C. or higher, the deposition is possible, but the fluoride gas escapes from the processing solution sharply, so that it is practical. Not.

The method of bringing the treatment liquid into contact with the substrate is not particularly limited, but a method of dipping the substrate in the treatment liquid is simple and a uniform coating is easily obtained. The immersion time is not particularly limited, and immersion may be performed until a desired film thickness is formed.

The substrate brought into contact with the treatment liquid is usually washed with water,
After drying, it is then heated. The heat treatment of the deposited and grown vanadium oxide film is considered to be related to the degree of crystallinity and orientation of the obtained fibrous or acicular vanadium oxide, and the preferred temperature range is 200 ° C.
That is all. The processing temperature should take into account the heat resistance of the substrate
The substrate can be appropriately selected from a temperature range of 200 ° C. or higher and can be treated at a high temperature as long as the substrate has heat resistance. For example, when an alumina plate is used as the substrate, the temperature may be raised to about 1000 ° C. Heat treatment time is usually 10 minutes to 5 minutes
Time is appropriate.

Next, the present invention will be described with reference to examples, but the present invention is not limited to only these examples.

Example 1 A borosilicate glass having a length and width of 50 mm and a thickness of about 1 mm was sufficiently washed.
It dried and was set as the sample base material. Next, 47% hydrofluoric acid
After dissolving and saturating vanadium pentoxide in the double dilution solution, filtering the remaining vanadium pentoxide and diluting with water, the vanadium pentoxide concentration is 0.031 mol / l or 0.062 m
ol / liter solution.

An aluminum plate was inserted into a container, and then a solution having the above-mentioned concentration was injected to prepare a treatment solution. Then, the substrate was immersed and the container was sealed. Then, leave it in a constant temperature bath set at 25 ° C or shake it for about
A predetermined time of 50 hours was maintained. Thereafter, the substrate is taken out, washed with water, dried at room temperature, and further dried at 400 ° C. for 1 hour.
The sample was fired for a period of time.

The prepared sample was confirmed to be vanadium pentoxide by X-ray diffraction and infrared absorption spectrum. Observation of these surfaces with a scanning electron microscope revealed a fibrous structure.

Example 2 An alumina plate having a length and width of 50 mm and a thickness of about 1 mm was sufficiently washed and dried to obtain a sample substrate. Next, vanadium pentoxide is dissolved and saturated in a 10-fold diluted solution of 47% hydrofluoric acid, and the remaining dissolved vanadium pentoxide is filtered. The solution was used.

An aluminum plate was inserted into the container, and then a solution having the above-mentioned concentration was injected to prepare a treatment solution. Then, the substrate was immersed and the container was sealed. Then, leave it in a constant temperature bath set at 25 ° C or shake it for about
A predetermined time of 50 hours was maintained. Thereafter, the substrate is taken out, washed with water, dried at room temperature, and further dried at 400 ° C. for 1 hour.
The sample was fired for a period of time.

The prepared sample was confirmed to be vanadium pentoxide by X-ray diffraction and infrared absorption spectrum. Observation of this surface with a scanning electron microscope revealed a fibrous structure.

Comparative Example 1 Soda lime glass having a length and width of 50 mm and a thickness of about 1 mm was sufficiently washed and dried to obtain a sample substrate. Next, vanadium pentoxide was dissolved and saturated in a 10-fold diluted solution of 47% hydrofluoric acid. After the remaining vanadium pentoxide was filtered, the mixture was diluted with water to obtain a vanadium pentoxide concentration of 0.031 mol / liter or
A 0.062 mol / liter solution was obtained.

An aluminum plate was inserted into the container, and then a solution having the above-mentioned concentration was injected to prepare a treatment solution. Then, the substrate was immersed and the container was sealed. Then, leave it in a constant temperature bath set at 25 ° C or shake it for about
A predetermined time of 50 hours was maintained. Thereafter, the substrate was taken out, washed with water, and dried at room temperature to obtain a sample.

The prepared sample was subjected to NaV by X-ray diffraction.
It was confirmed that the ₆ O _15. Observation of these surfaces with a scanning electron microscope revealed a film having a granular structure.

When the obtained film was baked at 400 ° C. for 1 hour, no change was observed in the granular structure.

Comparative Example 2 A borosilicate glass having a length and width of 50 mm and a thickness of about 1 mm was sufficiently washed.
It dried and was set as the sample base material. Next, 47% hydrofluoric acid
Vanadium pentoxide was dissolved and saturated in the double dilution solution.
After the remaining vanadium pentoxide is filtered, it is diluted with water to obtain a vanadium pentoxide concentration of 0.031 mol / liter or 0.06 mol / l.
A 2 mol / liter solution was obtained.

An aluminum plate was inserted into the container, and then a solution having the above-mentioned concentration was injected to prepare a treatment solution. Then, the substrate was immersed, and the container was sealed. Then, leave it in a constant temperature bath set at 25 ° C or shake it for about
A predetermined time of 50 hours was maintained. Thereafter, the substrate was taken out, washed with water, and dried at room temperature to obtain a sample.

The prepared sample was confirmed to be vanadium pentoxide by X-ray diffraction and infrared absorption spectrum. Observation of these surfaces with a scanning electron microscope revealed a film having a granular structure.

[0029]

[Effect of the Invention] No special treatment such as miniaturization of a base material or a carrier or making its surface porous,
A vanadium oxide film having an increased surface area can be formed on the surface of a substrate or carrier having an arbitrary shape by a simple operation, and can be effectively used, for example, for producing a vanadium-based catalyst.

Claims (1)

(57) [Claims] 1. A treatment solution comprising a vanadium oxide and fluorine, wherein the vanadium oxide is in a supersaturated state,
A vanadium oxide film having a fibrous structure, characterized in that a vanadium oxide film is deposited on the surface of the substrate by contacting the substrate with an alkali metal-free substrate and then subjected to a heat treatment at a temperature of 200 ° C. or more. Manufacturing method.