JPH06227819A - Preparation of compound metallic oxide - Google Patents

Abstract

PURPOSE:To prepare a compound metallic oxide suitable as a catalyst, especially the catalyst for ammoxidation reaction of alkanes at a relatively low temperature in good yield according to simple operation by mixing an Mo compound with a V compound at a specific ratio and then heating the resultant mixture in an organic solvent. CONSTITUTION:A molybdenum compound is mixed with a vanadium compound at a ratio (V/Mo) within the range of 0.01-10 and the resultant mixture is then heated in an organic solvent to prepare the objective compound metallic oxide. The organic solvent used is usually a 5-20C aliphatic hydrocarbon, a 6-20C aromatic hydrocarbon, a 1-20C alcohol, an aldehyde, a ketone, an ether, a carboxylic acid and a mixture thereof. The heating temperature is usually 100-350 deg.C. The produced compound metallic oxide, as necessary, is preferably burned and the crystallization can be accelerated by the burning.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for preparing a molybdenum-vanadium mixed metal oxide. The composite metal oxide is known as a catalyst, particularly as a gas phase partial oxidation catalyst for hydrocarbons, and is also attracting attention as an electrode material and the like.

[0002]

2. Description of the Related Art There are mainly two known methods for preparing a molybdenum-vanadium mixed metal oxide. The first is a method in which the oxides of the constituent metal elements of the composite metal oxide are sampled in predetermined amounts, mixed and pulverized, and prepared by a high temperature solid-state reaction (Journal of Catal).
ysis, 3,406-413 (1964), JP-A-6
3-88754, USP 4,751,157 etc.).

The second method is to prepare a mixed aqueous solution or slurry of a water-soluble salt of each metal element, evaporate it to dryness or coprecipitate it by adjusting the pH, and then bake the recovered solid content (JP-A-2- 257, Bull. Soc. Chim. F.
r, 5-6, Pt. 1,209-217 (1980)
etc).

[0004]

However, in the above-mentioned first solid-phase reaction method, generally, the firing conditions are usually high temperatures of 600 to 1000 ° C. and are usually carried out for a long time such as one day to one week. is necessary. The composite metal oxide prepared by this method usually has a low specific surface area and is not suitable for the purpose of serving as a catalyst. Also,
The above-mentioned second method requires a multi-step operation of firing the solid obtained after once forming an aqueous solution.
There are complicated points.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have prepared each of the composite metal oxides in the case of preparing a molybdenum-vanadium-based composite metal oxide. The inventors have found that a complex metal oxide can be obtained by a simple operation at a relatively low temperature by heating a compound of a metal element in an organic solvent, and arrived at the present invention.

That is, the gist of the present invention is to mix a molybdenum compound and a vanadium compound in an atomic ratio (V / Mo) of molybdenum atoms to vanadium atoms in the range of 0.01 to 10 and heat in an organic solvent. And a method for preparing a composite metal oxide.

The present invention will be described in detail below. The molybdenum compound, which is an essential raw material of the mixed metal oxide used in the present invention, as the vanadium compound, molybdenum, each carboxylic acid salt of vanadium, carboxylic acid ammonium salt,
Ammonium halide salts, oxides, halides, hydrogen acids, acetylacetonates, alkoxides, halides and the like can be used. The above raw material compounds are
Atomic ratio of molybdenum atom and vanadium atom (V / M
It is mixed so that o) is 0.01 to 10, preferably 0.1 to 2.

Further, as an arbitrary metal component other than molybdenum and vanadium, a compound of a metal such as tellurium or niobium, which will be described later, can be used as a raw material, and a specific compound to be used is carboxylate like molybdenum and vanadium. , Ammonium salt, ammonium carboxylic acid salt, hydrogen acid, alkoxide and the like. When this arbitrary metal is M, the atomic ratio (M / Mo) to molybdenum atoms is usually 0.
To be mixed in the range of 1.0.

Next, the organic solvent used in the present invention is not particularly limited, but is an aliphatic hydrocarbon having 5 to 20 carbon atoms, an aromatic hydrocarbon having 6 to 20 carbon atoms, and 1 to 20 carbon atoms.
Of alcohols, aldehydes, ketones, ethers, carboxylic acids and mixtures thereof. Of these, alcohols are preferable, and diols such as ethylene glycol, propylene glycol, and 1,4-butanediol are preferably used. The amount of the organic solvent used is usually 2 to 100 times by weight, preferably 10 to 40 times by weight, of the produced complex metal oxide.

The state of heating the mixed solution of the raw material metal compound and the organic solvent may be a uniform solution or a slurry suspension. At this time, an organic solvent corresponding to the heating temperature,
And it is preferable to proceed the reaction in a pressure-resistant container in consideration of the vapor pressure of the compound produced by decomposition of the raw material compound. Further, since the reaction system uses an organic solvent, it is preferable to replace the inside of the reactor with an inert gas such as nitrogen gas, and even if an inert gas is allowed to coexist in the system when heated in an organic solvent. Good.

The heating temperature is not particularly limited, but is usually 100 ° C. to 350 ° C., and particularly 120 to 290 ° C. is easy to operate. The reaction system can be kept more uniform by stirring, but it is not particularly necessary to stir, and the stirring method is not particularly limited. The heating reaction time is usually 1 to
Although it is 30 hours, a crystalline complex metal oxide having a specific structure as described later is often formed in about 2 to 6 hours. The composite metal oxide thus produced is usually a black powder, is stable against organic solvents and water, and is separated by an operation such as decantation, filtration, or centrifugation, and if necessary, is separated. After being washed, it is dried.

In the method of the present invention, heating in an organic solvent is believed to produce a complex metal oxide at a relatively low temperature because a homogeneous reaction or a partial dissolution proceeds in the solvent to cause a homogeneous reaction. . In addition, the above heat treatment alone may cause insufficient crystallization due to the difference in the raw material composition of the composite metal oxide or the heating conditions in the organic solvent, or may result in an amorphous crystal.

In such a case, it is preferable to calcine the produced composite metal oxide, if necessary, to promote crystallization. As the firing conditions, the firing atmosphere may be air or an atmosphere of an inert gas such as nitrogen, argon or helium, and the gas may contain a reducing gas such as hydrogen or hydrocarbon or water vapor. Or, in a vacuum, usually in the above-mentioned organic solvent at a heating temperature of 700 ° C. or less, preferably 400
It is carried out at a temperature of ~ 650 ° C for usually 0.5 to 30 hours, preferably 1 to 10 hours.

The composition of the composite metal oxide thus obtained is usually represented by the following formula (1). Mo _a V _b X _x O in _n (1) (Formula (1), X is Te, Nb, Ta, W, T
i, Al, Zr, Cr, Mn, Fe, Ru, Co, R
h, Ni, Pd, Pt, Sb, Bi, B, In and Ce
Represents one or more elements selected from
When set to 1, b = 0.01 to 10, preferably 0.1
.About.2.0, x = 0 to 1.0, and n is determined by the oxidation states of other elements. )

The coefficient a of each atom in the above equation (1),
b and x substantially match the atomic ratio when the raw material metal compound is charged. Further, when the above-mentioned composite metal oxide is particularly crystallized, it has the following pattern of powder X-ray diffraction (using Cu-Kα ray as an X-ray source).

[0016]

Table 2 X-ray lattice plane diffraction angle 2θ (°) Relative intensity 22.1 ± 0.5 100 28.2 ± 0.5 0 to 150, especially 5 to 120 36.2 ± 0.5 2 to 80, Especially 5-60 45.2 ± 0.5 2-40, especially 5-30 50.0 ± 0.5 0-40, especially 5-30

The composite metal oxide prepared by the method of the present invention includes a catalyst as one of its uses, and particularly, a vapor phase catalytic oxidation reaction of hydrocarbons. For example, it can be used as a catalyst used in the production of nitrile by the ammoxidation reaction of alkane, particularly in the production of acrylonitrile from propane. When used as the catalyst,
It is preferable that the composition of the composite metal oxide is represented by the following formula (2).

Mo _a V _b Te _c Y _y O _n (2) (In the formula (2), Y is Nb, Ta, W, Ti, A
1, Zr, Cr, Mn, Fe, Ru, Co, Rh, N
represents one or more elements selected from i, Pd, Pt, Sb, Bi, B, In and Ce, and when a = 1, b = 0.01 to 1.0, preferably 0.1-
0.6, c = 0.01 to 1.0, preferably 0.05 to
0.4, y = 0.01 to 1.0, preferably 0.1
0.6, and n is determined by the oxidation states of other elements. ) In the case of using this complex metal oxide in the ammoxidation reaction of alkane, those having the above-mentioned specific crystal structure show particularly excellent catalytic action.

When the above complex metal oxide is used as a catalyst for producing nitrile, the following reaction conditions are adopted. When propane is used as the alkane and air is used as the oxygen source, the ratio of the air supplied to the reaction is usually 25 mol times or less, and particularly in the range of 1 to 15 mol, showing high acrylonitrile selectivity. Further, the ratio of ammonia to be supplied to the reaction is 0.
A range of 2 to 5 molar times, particularly 0.5 to 3 molar times is preferable. Although this reaction is usually carried out under atmospheric pressure,
It can also be carried out under low pressure or reduced pressure. For other alkanes, the composition of the feed gas is selected according to the reaction conditions for propane. The reaction temperature is usually 340 to 480 ° C, preferably 400 to 450 ° C, and the gas space velocity SV is usually 100 to 10,000.
h ^-1, preferably from 300~2000h ^-1. An inert gas such as nitrogen, argon, or helium can be used as a diluent gas for adjusting the space velocity and the oxygen partial pressure.

[0020]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist. In addition,
The metal oxide yield (%) and propane conversion (%) in the gas phase catalytic oxidation reaction of propane, acrylonitrile selectivity (%), and acrylonitrile yield (%) in the following Examples and Comparative Examples are respectively calculated by the following formulas. Indicated by.

[0021]

[Equation 1] Yield of metal oxide (%) = (weight of complex metal oxide formed (g) / sum of weight of charged metal elements as oxides with the highest degree of oxidation (g)) × 100 conversion rate of propane (%) = (Mol number of propane consumed / mol number of propane supplied) × 100 acrylonitrile selectivity (%) = (mol number of acrylonitrile produced / mol number of propane consumed) × 100 acrylonitrile yield (%) = (Number of moles of acrylonitrile produced / number of moles of propane fed) × 100

Example 1 4.29 g of VO per 100 ml of 1,4-butanediol
(O-nBu) ₃ and 2.75 g of Nb (O-nBu) ₅
Was dissolved, and then 16.30 g of MoO ₂ (aca
c) ₂ , 2.64 g of H ₆ TeO ₆ was dispersed, and 200
The mixture was placed in a SUS316 autoclave with a volume of ml and purged with nitrogen (80 KG), then heated to 265 ° C. with stirring and heated and stirred for 2 hours. The slurry produced after cooling was separated by a centrifugal separator (3500 rpm, 20 minutes), and then washed with acetone and centrifugal separation were repeated until coloring of the washing liquid disappeared, air-dried and then dried at 150 ° C. in a drier. As a result, composition formula _{Mo 1.0 V 0.30 Nb 0.10 Te 0.23} O n a black solid was obtained 9.95 g (metal oxide yields 88.
8%).

The powder X-ray diffraction of the thus obtained composite metal oxide was measured. As a result, the diffraction angles 2θ (°) were 22.1 (100), 28.2 (60.0), 3
6.2 (16.3), 45.1 (10.2), 50.0
A main diffraction peak was observed at (6.1) (the numbers in parentheses indicate relative peak intensities when the peak at 22.1 ° was taken as 100. The same applies to the following Examples).

Example 2 32.62 g of MoO in 200 ml of ethylene glycol
₂ (acac) ₂ and 5.28 g of H ₆ TeO ₆ were dispersed, placed in a 500-ml four-necked flask and purged with nitrogen, and then heated to 100 ° C. with stirring to obtain a uniform solution. Then, 8.62 g of VO (O-nBu) ₃ and 5.66 g of Nb (O-nBu) ₅ were injected and dissolved,
The mixture was heated and stirred at 130 ° C for 2 hours. The produced slurry was cooled, filtered and separated, and then acetone washing and filtration were repeated until the washing liquid was no longer colored, and then the washing and filtration were repeated twice with water, followed by air drying and drying at 150 ° C. in a drier. As a result, composition formula _{Mo 1.0 V 0.30 Nb 0.10 Te 0.23} O n a black solid was obtained 16.9 g (metal oxide yield 7
5.4%).

Next, the composite metal oxide was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine and then pulverized to obtain 16 to
It was sieved to 28 mesh and fired in a nitrogen stream at 600 ° C. for 2 hours. When the powder X-ray diffraction measurement of the composite metal oxide thus obtained was carried out, the diffraction angle was 2θ (°), and
2.1 (100), 28.2 (59.7), 36.2
(18.1), 45.1 (13.9), 50.0 (9.
A major diffraction peak was observed in 7).

Example 3 1.99 g of VO (a) per 100 ml of ethylene glycol
cac) ₂ , 1.36 g ammonium niobium oxalate, 8.15 g MoO ₂ (acac) ₂ , 1.32 g
H ₆ TeO ₆ was dissolved to obtain a uniform solution. This solution was put in a 200 ml SUS316 autoclave, and the atmosphere was replaced with nitrogen (80 KG).
The temperature was raised to ° C and the mixture was heated and stirred for 2 hours. The slurry produced after cooling was separated by a centrifugal separator (3500 rpm, 20 minutes),
Washing with acetone and centrifugation were repeated until coloring of the washing liquid disappeared, followed by air drying and drying at 150 ° C. in a drier. As a result, composition formula _{Mo 1.0 V 0.3 Nb 0.10 Te 0.23} O n
4.74 g of a black solid was obtained (metal oxide yield 8
4.6%).

The powder X-ray diffraction of the thus obtained composite metal oxide was measured, and the diffraction angles 2θ (°) were 22.1 (100), 28.2 (60.0), 3
6.2 (18.0), 45.1 (10.0), 50.0
A major diffraction peak was observed at (6.0).

Example 4 As vanadium raw material, ammonium metavanadate 1.76
g, ammonium niobium oxalate 2.72 g, and molybdenum raw material are ammonium paramolybdate 8.83 g and 2.6.
Example 3 except that 4 g of H ₆ TeO ₆ was used as the raw material
A composite metal oxide was prepared in the same manner as in. As a result, the black solid composition formula _{Mo 1.0 V 0.3 Nb 0.10 Te 0.23} O n was obtained 3.67 g (metal oxide yield 65.5%),
It was an amorphous crystal on the powder X-ray diffraction pattern.

Example 5 A composite metal oxide was prepared in the same manner as in Example 4 except that 1.36 g of V ₂ O ₅ was used as a vanadium raw material. As a result, composition formula _{Mo 1.0 V 0.3 Nb 0.10 Te 0.23} O n a black solid was obtained 8.23 g (metal oxide yields 88.
2%). When the powder X-ray diffraction measurement of the composite metal oxide thus obtained was carried out, the diffraction angle was 2θ (°), and
2.1 (100), 28.2 (82.6), 36.2
(26.1), 45.1 (13.0), 50.0 (1
A major diffraction peak was observed at 6.5).

Example 6 A composite metal oxide was prepared in the same manner as in Example 5 except that 100 ml of 1,4-butanediol was used as the organic solvent. As a result, the black solid composition formula _{Mo 1.0 V 0.3 Nb 0.10 Te 0.} 23 O n was obtained 6.41 g (metal oxide yield 7
0.8%), and the crystals were amorphous on the powder X-ray diffraction pattern.

Example 7 A composite metal oxide was prepared in the same manner as in Example 1 except that H ₆ TeO ₆ was 2.29 g. As a result, the composition formula is Mo
_{1.0 V 0.3 Nb 0.10 Te 0.20 O} n a black solid 10.
0 g was obtained (metal oxide yield 87.8%). When powder X-ray diffraction measurement of the thus obtained composite metal oxide was carried out, a diffraction angle 2θ (°) was 22.1 (10).
0), 28.2 (60.6), 36.2 (18.2),
Major diffraction peaks were observed at 45.1 (13.6) and 50.0 (7.6).

Example 8 A composite metal oxide was prepared in the same manner as in Example 1 except that 1.95 g of H ₆ TeO ₆ was used. As a result, the composition formula is Mo
_{1.0 V 0.3 Nb 0.10 Te 0.17 O} n a black solid 9.2
6 g was obtained (metal oxide yield 81.0%). When powder X-ray diffraction measurement of the thus obtained composite metal oxide was carried out, a diffraction angle 2θ (°) was 22.1 (10).
0), 28.2 (69.2), 36.2 (23.1),
Major diffraction peaks were observed at 45.1 (13.8) and 50.0 (12.3).

Example 9 A composite metal oxide was prepared in the same manner as in Example 1 except that H ₆ TeO ₆ was changed to 1.61 g. As a result, the composition formula is Mo
_{1.0 V 0.3 Nb 0.10 Te 0.14 O} n a black solid 8.3
8 g was obtained (metal oxide yield 80.0%). When powder X-ray diffraction measurement of the thus obtained composite metal oxide was carried out, a diffraction angle 2θ (°) was 22.1 (10).
0), 28.2 (67.2), 36.2 (40.3),
Major diffraction peaks were observed at 45.1 (14.9) and 50.0 (11.9).

Example 10 A composite metal oxide was prepared in the same manner as in Example 1 except that H ₆ TeO ₆ was changed to 3.45 g. As a result, the composition formula is Mo
_{1.0 V 0.3 Nb 0.10 Te 0.30 O} n a black solid 11.
0 g was obtained (metal oxide yield 93.4%). When powder X-ray diffraction measurement of the thus obtained composite metal oxide was carried out (using Cu-Kα ray), the diffraction angles 2θ (°) were 22.1 (100), 28.2 (68. 0), 3
6.2 (20.0), 45.1 (13.1), 50.0
A major diffraction peak was observed at (10.1).

Example 11 A composite metal oxide was prepared in the same manner as in Example 1 except that H ₆ TeO ₆ was not added. As a result, the composition formula is Mo _1.0.
V _0.3 Nb _0.10 O _n a black solid was obtained 8.32 g (metal oxide yield 88.9%). The powder X-ray diffraction measurement of the thus-obtained composite metal oxide was carried out, and the diffraction angles 2θ (°) were 22.1 (100) and 36.2.
(17.2), 45.3 (13.8), 50.0 (5.
A major diffraction peak was observed in 2).

Example 12 A composite metal oxide was prepared in the same manner as in Example 1 except that Nb (O-nBu) ₅ was not added. As a result, a black solid composition formula Mo _1.0 V _0.3 Te _0.23 O _n is 9.90g
Obtained (yield of metal oxide: 95.2%). The powder X-ray diffraction measurement of the thus-obtained composite metal oxide was carried out, and it was found that the diffraction angle 2θ (°) was 22.1 (100), 2
8.4 (102.5), 36.5 (36.3), 45.
Major diffraction peaks were observed at 1 (12.5) and 50.1 (17.5).

Example 13 A composite metal oxide was prepared in the same manner as in Example 1 except that Nb (O-nBu) ₅ and H ₆ TeO ₆ were not added. As a result, the composition formula is solid black Mo _1.0 V _0.5 O _n was obtained 6.90 g (metal oxide yield 92.3%). A powder X-ray diffraction measurement of the thus-obtained composite metal oxide was performed, and it was found that the diffraction angle 2θ (°) was 22.1 (1
Major diffraction peaks were observed at 00), 36.2 (80.0), and 45.1 (8.5).

Example 14 A composite metal oxide was prepared in the same manner as in Example 1 except that ethylene glycol was used as the organic solvent. As a result, the composition formula of black _{Mo 1.0 V 0.3 Nb 0.10 Te 0.23} O n solid 1
0.5 g was obtained (metal oxide yield 94.0%). When powder X-ray diffraction measurement of the thus obtained composite metal oxide was carried out, a diffraction angle 2θ (°) was 22.1 (10).
0), 28.2 (68.8), 36.2 (18.7),
Major diffraction peaks were observed at 45.1 (11.5) and 50.0 (10.4).

Example 15 The composite metal oxide obtained in Example 1 was molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, and then pulverized to 16 to 2
It was sieved to 8 mesh and used as a catalyst. Catalyst 1.0m
1 was charged into a reactor, reaction temperature was 420 ° C., space velocity SV
At 500 h ^-1 , propane: ammonia: air = 1:
Table 1 shows the results of gas-phase catalytic reaction performed by supplying gas at a molar ratio of 3.0: 15.

Example 16 Tableting and composite metal oxide obtained in Example 2 after firing 1.
67 ml was charged into a reactor, gas was supplied at a reaction temperature of 450 ° C. and a space velocity SV of 300 h ⁻¹ at a molar ratio of propane: ammonia: air = 1: 3.0: 15 to carry out a gas phase catalytic reaction. The results obtained are shown in Table-1.

Comparative Example 1 1170 mg of ammonium ammonium metavanadate was dissolved in 100 ml of warm water, and 12.5 ml of an aqueous solution of niobium ammonium oxalate salt (0.2 Nb atom / 1) was added thereto.
0.0 ml of telluric acid aqueous solution (0.5 Te atom / 1) and 25.0 ml of ammonium paramolybdate aqueous solution (1.0 Mo atom / 1) were sequentially added to prepare a uniform aqueous solution, which was heated and then dried. composition formula was evaporated to dryness at 130 ° C. is Mo _1.0 V during vessel _0.4 Nb _0.1 Te _0.2 O _n
Of solids were obtained. When powder X-ray diffraction measurement was performed on the composite metal oxide thus obtained, a plurality of diffraction peaks were observed, but the pattern was completely different from that of Example 1.

This composite metal oxide was calcined at 350 ° C. under air flow, molded into a size of 5 mmφ × 3 mmL using a tablet molding machine, and then pulverized to obtain a catalyst sieved to 16 to 28 mesh. 1.0 ml of the catalyst was charged into a reactor, the reaction temperature was 420 ° C., the space velocity SV was 500 h ⁻¹ , and propane:
Table 1 shows the results of gas-phase catalytic reaction performed by supplying gas at a molar ratio of ammonia: air = 1: 1.2: 10.

[0043]

[Table 3]

[0044]

INDUSTRIAL APPLICABILITY According to the present invention, a composite metal oxide containing molybdenum and vanadium can be prepared in a good yield by a simple operation at a relatively low temperature. Further, the composite metal oxide obtained by the method of the present invention is useful as a catalyst, and is particularly suitable as a catalyst for ammoxidation reaction of alkane.

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Claims (7)

[Claims] 1. A molybdenum compound and a vanadium compound, wherein the atomic ratio of the molybdenum atom to the vanadium atom (V / M
o) is mixed in the range of 0.01 to 10 and heated in an organic solvent, which is a method for preparing a composite metal oxide. 2. The method for preparing a composite metal oxide according to claim 1, wherein the organic solvent is an alcohol. 3. The method for preparing a composite metal oxide according to claim 1, wherein the heating temperature is 100 to 350 ° C. 4. The method for preparing a composite metal oxide according to claim 1, wherein the solid obtained by heating in an organic solvent is fired at the heating temperature or higher and 700 ° C. or lower. 5. In the X-ray diffraction line of the composite metal oxide,
The method for preparing a composite metal oxide according to claim 1, wherein an X-ray diffraction peak is shown at a diffraction angle 2θ shown below. [Table 1] Diffraction angle 2θ (°) Relative intensity 22.1 ± 0.5 100 28.2 ± 0.5 0-150 36.2 ± 0.5 2-80 45.2 ± 0.5 2-40 50.0 ± 0.5 0-40 6. The method for preparing a composite metal oxide according to claim 1, wherein the composite metal oxide is represented by the following formula. Mo _a V _b X _x O in _n (1) (Formula (1), X is Te, Nb, Ta, W, T
i, Al, Zr, Cr, Mn, Fe, Ru, Co, R
h, Ni, Pd, Pt, Sb, Bi, B, In and Ce
Represents one or more elements selected from among the following, and when a = 1, b = 0.01-10 x = 0-1.0, and n is the oxidation state of another element. Determined by ) 7. A compound of molybdenum, vanadium and tellurium and niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, Nitrile from alkane consisting of complex metal oxide represented by the following formula, characterized by mixing with a compound consisting of one or more elements selected from indium and cerium and heating in an organic solvent A method for preparing a catalyst for producing a. _{Mo a V b Te c Y y} O in _n (2) (Equation (2), Y is Nb, Ta, W, Ti, A
1, Zr, Cr, Mn, Fe, Ru, Co, Rh, N
Represents one or more elements selected from i, Pd, Pt, Sb, Bi, B, In and Ce, and when a = 1, b = 0.01 to 1.0 c = 0 0.01 to 1.0 y = 0.01 to 1.0, and n is determined by the oxidation states of other elements. )