JP2005305421A - Method of producing compound oxide catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a compound oxide catalyst for producing a corresponding unsaturated carboxylic acid by subjecting an unsaturated aldehyde to gas phase catalytic oxidation by a molecular oxygen-containing gas stably for a long period of time and also at high yield. <P>SOLUTION: In the production of the compound oxide catalyst expressed by the formula: Mo<SB>12</SB>V<SB>a</SB>X<SB>b</SB>Cu<SB>c</SB>Y<SB>d</SB>C<SB>e</SB>Si<SB>f</SB>O<SB>g</SB>(where, X indicates at least one kind of element selected from Nb and W, Y indicates at least one kind of element selected from a group configured of Sb, Mg, Ca, Sr, Ba and Zn, a, b, c, d, e, f and g represent the atomic ratio of respective elements and satisfy, against 12 for molybdenum atom, the expressions of 0<a≤12, 0≤b≤12, 0<c≤12, 0≤d≤8, 0≤e≤1000, 0≤f≤1000, and g is the number of oxygen atoms which satisfies the oxidation state of the elements other than Si and C of the component elements in the formula), the feed source compounds of each component element are integrated in an aqueous medium and in the presence of an organic acid, and the aqueous solution or dispersion of an integrated object obtained is dried to prepare a powder material and a molded product obtained by molding the powder material is calcined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a composite oxide catalyst for producing a unsaturated carboxylic acid corresponding to a long-term stable and high yield by gas-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. About.

  Conventionally, various catalysts for producing unsaturated carboxylic acids such as acrylic acid and methacrylic acid by vapor-phase catalytic oxidation of unsaturated aldehydes such as acrolein and methacrolein with molecular oxygen have been proposed. From the viewpoint of effective utilization of unsaturated aldehyde raw materials produced from olefins and rationalization of processes in the reaction, these catalysts are required to have a slightly higher unsaturated aldehyde conversion rate and the selectivity of the unsaturated carboxylic acid as the target product. . In this case, for example, the production scale for producing acrylic acid by reacting with acrolein is usually carried out at a scale of 3 million tons / year, so that it can be obtained when the conversion rate and selectivity are improved even by 0.1%. The amount of acrylic acid increases greatly at the level of hundreds to thousands of tons. Therefore, improvement in catalyst performance such as conversion rate and selectivity greatly contributes to effective utilization of resources and rationalization of processes even if a slight improvement.

Conventionally, various proposals have been made with the aim of improving the catalyst performance such as the raw material conversion rate and selectivity of these reactions. The present applicant has also proposed, for example, Patent Document 1 as a composite oxide catalyst having excellent performance therefor. Patent Document 1, in _{Mo 12 Nb a V b Cu o} Si d C e X f Y g Z h O i ( wherein, X represents at least one element selected from alkali metals and Tl, Y is And at least one element selected from Mg, Ca, Sr, Ba and Zn, and Z is selected from W, Ce, Sn, Cr, Mn, Fe, Co, Y, Nd, Sm, Ge and Ti Represents at least one element, wherein a, b, c, d, e, f and g represent the atomic ratio of each element, and a is 0 <a ≦ 12 and 0 <b ≦ 10 with respect to the molybdenum atom 12. , 0 <c ≦ 8, 0 <d ≦ 1000, 0 <e ≦ 1000, 0 ≦ f ≦ 2, 0 ≦ g <5, 0 ≦ h <5, i excludes Si and C from the above components A catalyst having a composition having a number determined by the degree of oxidation.

Further, Patent Document 2, although the present applicant according to a separate applicant, as a catalyst used for the same reaction, the _{formula: Mo 12 V g Sb h A} i B i C k ( In the formula, A One or more elements selected from the group consisting of Nb and Ta, and B is Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Cr, W, Mn, Fe, Ru, Co, Ni or P, and C is Ag, Zn, Ti, Sn, Pb, Cu, As, or Se, g and h are each 0.01 to 1.5, and h / g = 0.3 to 1.0, i is 0.001 to 3.0, J is 0001 to 0.1, and K is 0 to 0.05).

However, although these conventional complex oxide catalysts each show excellent performance, further improvement in performance of raw material unsaturated aldehyde conversion rate and unsaturated carboxylic acid selectivity is desired.
JP 2003-200055 A JP 2000-317309 A

  The present invention provides a high conversion of raw material unsaturated aldehyde and high selectivity of unsaturated carboxylic acid when producing unsaturated carboxylic acid by gas phase catalytic oxidation of unsaturated aldehyde with molecular oxygen-containing gas, The present invention also provides a novel method for producing a composite oxide catalyst that exhibits stable performance over a long period of time.

  The present inventor has intensively studied to achieve the above object, and as a result, at least one selected from the group consisting of Mo, V, X (Nb and W) which is the same or similar to the above-mentioned Patent Document 1 and Patent Document 2. Element), Y (at least one element selected from the group consisting of Sb, Mg, Ca, Sr, Ba, and Zn), Cu, Si, and C. In this case, the raw material compounds of each element are integrated in an aqueous medium in the presence of an organic acid, and the resulting integrated product is dried, molded, and calcined, so that its catalytic performance, conversion rate of unsaturated aldehyde It has been found that the selectivity of the unsaturated carboxylic acid as the target product is improved.

  In the production of the composite oxide catalyst of the present invention, means for integrating each element source compound in an aqueous medium in the presence of an organic acid is disclosed in Patent Document 1 and Patent Document 2. It is different from the usual method. In the production process of the catalyst of Patent Document 1, no organic acid itself is used. Patent Document 2 uses oxalic acid, which is an organic acid used in the present invention in the process of producing a catalyst, but in the first place, the composition differs from the catalyst produced in the present invention containing Cu as an essential component. In the case of Patent Document 2, such oxalic acid is used to react with niobic acid to form a complex and dissolve water-insoluble niobic acid. It is not used to integrate the source compounds of each component in an aqueous medium.

  In the production method of the present invention, when the source compound of each component of the catalyst is integrated in an aqueous medium in the presence of an organic acid, the organic acid is coordinated with each component element constituting the catalyst, By suppressing the bonding between the component elements and changing the structure of the composite oxide catalyst finally obtained, the oxidation-reduction state, and the dispersion state of the catalyst component on the carrier, the characteristics are improved.

Thus, the present invention is characterized by the following gist.
_{(1): Mo 12 V a X b Cu} c Y d C e Si f O g ( wherein, Mo is molybdenum, V is vanadium, Cu is copper, C is carbon, Si is silicon, O is an oxygen , X represents at least one element selected from Nb and W, and Y represents at least one element selected from the group consisting of Sb, Mg, Ca, Sr, Ba, and Zn. , D, e, f and g indicate the atomic ratio of each element, 0 <a ≦ 12, 0 ≦ b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 1000, 0 ≦ f ≦ 1000, and g is a number determined by the number of oxygen atoms necessary to satisfy the oxidation state of other elements other than Si and C among the above components). In the production of the above, the source compound of each component element is integrated in the presence of an organic acid, and an aqueous solution or an integrated product obtained is integrated. Is a method for producing a composite oxide catalyst, comprising: drying a dispersion to prepare a powder; and firing a molded product obtained by molding the powder.
(2) The method for producing a composite oxide catalyst according to the above (1), wherein the organic acid is present in an amount of 0.001 to 1 mol with respect to 1 mol of molybdenum.
(3) The method for producing a composite oxide catalyst according to the above (1) or (2), wherein the organic acid is at least one selected from citric acid, oxalic acid and malic acid.
(4) Any of (1) to (3) above, wherein the composite oxide catalyst is a catalyst for producing a corresponding unsaturated carboxylic acid by gas phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. A method for producing the composite oxide catalyst described in 1.
(5) Acrolein is vapor-phase contact oxidized with a molecular oxygen-containing gas in the presence of the composite oxide catalyst produced by the production method according to any one of (1) to (4) above, and the corresponding acrylic acid is obtained. How to manufacture.

  According to the present invention, when producing unsaturated carboxylic acid by gas phase catalytic oxidation of unsaturated aldehyde with molecular oxygen-containing gas, high conversion of raw material unsaturated aldehyde and high selectivity of unsaturated carboxylic acid are achieved. Provided is a method for producing a composite oxide catalyst that exhibits stable performance over a long period of time.

  In particular, the conversion rate of acrolein per catalyst unit is improved, the selectivity of acrylic acid of the catalyst is improved, and a highly active composite oxide catalyst capable of efficiently performing the gas phase catalytic oxidation reaction of acrolein can be produced.

  The composite oxide catalyst produced in the present invention is represented by the above formula. In the above formula, X, Y, a, b, c, d, e, f and g are as described above. Among them, particularly preferably 0.1 ≦ a ≦ 6, 0.1 ≦ b ≦ 6, 0.1 ≦ c ≦ 6, 0.01 ≦ d ≦ 6, 5 ≦ e ≦ 500, 5 ≦ f ≦ 500. is there.

  Such a composite oxide catalyst of the present invention is produced by integrating the source compounds of the respective catalyst components constituting the above formula in the presence of an organic acid. Here, integrating the source compounds of the respective catalyst components preferably means mixing the source compounds of the respective catalyst component elements in an aqueous medium system composed of an aqueous solution or an aqueous dispersion, and aging treatment as necessary. Say. (B) a method of mixing each of the above-mentioned source compounds at once, (b) a method of mixing each of the above-mentioned source compounds at once, and further aging treatment, (c) each of the above-mentioned source compounds (D) a method in which each of the above-mentioned source compounds is mixed and aged repeatedly in a stepwise manner and / or a method in which the above (a) to (d) are combined. Included in the integration of the component element source compounds in the aqueous medium system.

  As described in the Chemical Dictionary (Kyoritsu Shuppan), the above-mentioned “aging” means “physical properties required by processing industrial raw materials or semi-finished products under specific conditions such as constant temperature for a certain period of time. This refers to an operation for obtaining, increasing, or progressing a predetermined reaction. In the present invention, the above-mentioned fixed time preferably refers to a range of 1 minute to 24 hours, and the above-mentioned fixed temperature is preferably in the range of room temperature to 200 ° C. In the above integration, not only the source compound of each element constituting the catalyst but also support materials such as alumina, silica, and heat-resistant oxide can be included as targets for such integration.

  As the organic acid that is present when the source compound of each element constituting the catalyst of the present invention is integrated, an organic acid having a property of being easily soluble in water can be used. Among these, at least one selected from citric acid, oxalic acid, and malic acid is preferable. The amount of the organic acid present is preferably 0.001 to 1 mol, particularly preferably 0.01 to 0.5 mol, relative to 1 mol of Mo. When the amount of the organic acid is less than 0.001 mol, the catalyst performance is not improved, and conversely, when the amount of the organic acid is more than 1 mol, the catalyst performance is decreased, which is preferable. Absent.

  The source compound of each component of the composite oxide catalyst of the present invention is not particularly limited as long as it is a compound that becomes an oxide by firing except a silicon carbide compound, whether it is water-soluble or poorly water-soluble. Specific examples of the compound include halides, sulfates, nitrates, ammonium salts, oxides, carboxylates, ammonium carboxylates, ammonium halides, hydrogen acids, acetylacetonates, alkoxides, and the like of each component. . Specific examples of silicon and carbon raw material compounds include green silicon carbide and black silicon carbide, and silicon carbide is preferably a fine powder. As the raw material compound, one containing each component alone may be used, or a raw material compound containing two or more components may be used.

  The preferred specific embodiments in the production method of the present invention will be described in order. First, an aqueous solution or aqueous dispersion of the above-mentioned catalyst component element source compound is prepared. In the present invention, these aqueous solutions or aqueous dispersions are also referred to as slurry solutions. The slurry solution can be obtained by uniformly mixing the source compound of each constituent component with water. The use ratio of the raw material compound of each constituent component in the slurry solution may be in a range in which the atomic ratio of each catalyst constituent element is represented by the above formula. The organic acid can be added after the slurry solution is prepared or in the middle of the preparation. Among them, it is preferable to add the organic acid at a stage after dissolving Mo and V.

  The amount of water in the slurry solution is not particularly limited as long as it can dissolve or uniformly disperse the raw material compounds of each component, but taking into consideration drying conditions such as the subsequent drying method, drying temperature, and drying time. And may be determined appropriately. The amount of water is usually 100 to 2000 parts by weight with respect to a total of 100 parts by weight of the raw material compounds. If the amount of water is less than the above predetermined amount, the compound may not be completely dissolved or may not be uniformly mixed. Further, if the amount of water is large, there is a risk that the energy cost during the heat treatment is increased. Integration of each element component constituting the catalyst proceeds through mixing and stirring in the preparation process of the slurry solution. However, in order to further promote the integration, preferably room temperature to 200 ° C., particularly preferably 70 to 100 ° C. And preferably aging treatment for 1 minute to 24 hours, particularly preferably 30 minutes to 6 hours.

  Next, the aqueous solution or aqueous dispersion is dried to form a powder. There is no particular limitation on the drying as long as the aqueous solution or aqueous dispersion can be sufficiently dried and a powder can be obtained. For example, drum drying, freeze drying, spray drying and the like are preferable methods. Spray drying is a method that can be preferably applied to the present invention because it can be dried from an aqueous solution or aqueous dispersion into a homogeneous powder state in a short time.

  The drying temperature is usually 90 to 200 ° C, preferably 130 to 170 ° C, although it varies depending on the concentration of the slurry solution. The particle size of the powder obtained by such drying is preferably 10 to 200 μm. For this reason, the powder can optionally be pulverized after drying.

  The powder obtained by the drying is then molded. There is no restriction | limiting in particular in a shaping | molding method, Preferably it shape | molds using a binder. Preferred binders are selected from the group consisting of silica, graphite and crystalline cellulose. The binder is preferably used in an amount of about 1 to 50 parts by weight with respect to 100 parts by weight of the powder. Further, if necessary, inorganic fibers such as ceramic fibers and whiskers can be used as a material for improving the mechanical strength of the catalyst particles. However, fibers that react with catalyst components such as potassium titanate whiskers and basic magnesium carbonate whiskers are not preferred. For improving the strength, ceramic fiber is particularly preferable. The amount of these fibers used is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the powder. The molding aid is usually used in advance mixed with powder.

  The powder mixed with a molding aid such as a binder is molded by a method such as (A) tableting molding, (B) extrusion molding, or (C) spherical or other shape support molding method. As the shape of the molded body, an appropriate shape such as a spherical shape, a cylindrical shape, or a ring shape is preferably selected. The molded product thus molded can then be calcined to obtain a composite oxide catalyst. The firing temperature can be usually 250 to 500 ° C, preferably 300 to 420 ° C, and the firing time is 1 to 50 hours. Firing can be performed in an atmosphere in the presence of an inert gas or molecular oxygen. If the firing temperature is too low, thermal diffusion of the molybdenum element is not sufficient, and if it is too high, the molybdenum element may be lost by sublimation.

  The means for producing a corresponding unsaturated carboxylic acid by vapor phase oxidation of an unsaturated aldehyde using molecular oxygen or a molecular oxygen-containing gas using the catalyst produced according to the present invention is performed by an existing method. be able to. For example, a fixed bed tube reactor is used as the reactor. In this case, the reaction may be a single flow method or a recycle method through the reactor, and can be carried out under conditions generally used for this type of reaction.

For example, a mixed gas composed of 1 to 15% by volume of acrolein, 0.5 to 25% by volume of molecular oxygen, 0 to 40% by volume of water vapor, 20 to 80% by volume of inert gas such as nitrogen and carbon dioxide, etc. Preferably, it is introduced at a space velocity (SV) of 300 to 5000 hr ⁻¹ under a pressure of 250 to 450 ° C. and a pressure of 0.1 to ¹ MPa in a catalyst layer filled in each reaction zone of each reaction tube of 15 to 50 mm. In the present invention, it is possible to operate even under high-load reaction conditions, for example, higher feed gas degree or higher space velocity conditions in order to increase productivity. Thus, acrylic acid can be produced with high selectivity and high yield by the catalyst produced in the present invention.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention should not be construed as being limited to these examples. The night bath used in the examples refers to a salt bath in which a reaction tube is placed in a heat medium made of an alkali metal nitrate and reacted. This heat medium melts at 200 ° C. or higher and can be used up to 400 ° C. Since the thermal efficiency is good, it is a reaction bath suitable for an oxidation reaction with a large calorific value.

  The acrolein conversion, acrylic acid selectivity, and acrylic acid yield are defined by the following formulas.

Acrolein conversion (mol%) = 100 × (number of moles of reacted acrolein) / (number of moles of supplied acrolein)
Acrylic acid selectivity (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of converted acrolein)
Acrylic acid yield (mol%) = 100 × (number of moles of acrylic acid produced) / (number of moles of acrolein supplied)

Example 1
A composite metal oxide in which the empirical formula of the constituent components excluding oxygen was Mo ₁₂ V _2.4 Nb ₁ Cu ₂ Si ₂₀₀ C ₂₀₀ was prepared as follows.
First, 1446 ml of pure water was heated to 80 ° C., and 207 g of ammonium paramolybdate, 27.5 g of ammonium metavanadate, and 12.0 g of citric acid were dissolved while sequentially stirring. A copper sulfate aqueous solution in which 48.6 g of copper sulfate was dissolved in 204 ml of pure water was added to the aqueous solution, and 19.3 g of niobium hydroxide was further added and stirred to obtain a slurry solution.

  782 g of silicon carbide powder was added to the slurry solution, and the mixture was sufficiently stirred and mixed. The slurry liquid was heated to 130 ° C. and dried. 1.5% by weight of graphite was added to and mixed with this, molded with a small tableting machine, and calcined at 380 ° C. for 3 hours in a nitrogen stream in a firing furnace as a catalyst.

In order to evaluate the obtained catalyst, 0.3 g of a 20-28 mesh pulverized and sized particle was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and this reaction tube was heated in a night bath (temperature: 288). The composition gas (5% by volume of acrolein, 8% by volume of oxygen, 15% by volume of steam and 72% by volume of nitrogen gas) is introduced into the reaction tube, and SV (space velocity; the raw material gas per unit time) is introduced. The flow rate / apparent volume of catalyst charged was reacted at 14900 / hr ⁻¹ . As a result of the reaction, the acrolein conversion was 99.0%, the acrylic acid selectivity was 98.6%, and the acrylic acid yield was 97.6%.

Example 2
A composite metal oxide in which the empirical formula of the constituent components excluding oxygen was Mo ₁₂ V _2.4 Nb ₁ Cu ₂ Si ₂₀₀ C ₂₀₀ was prepared as follows.
First, 1446 ml of pure water was heated to 80 ° C., and 207 g of ammonium paramolybdate, 27.5 g of ammonium metavanadate, and 12.0 g of oxalic acid were dissolved in this order with stirring. To this was added an aqueous copper sulfate solution in which 48.6 g of copper sulfate was dissolved in 204 ml of pure water, and 19.3 g of niobium hydroxide was further added and stirred to obtain a slurry solution.

  782 g of silicon carbide powder was added to the slurry solution, and the mixture was sufficiently stirred and mixed. The slurry liquid was heated to 130 ° C. and dried. 1.5% by weight of graphite was added to and mixed with this, molded with a small tableting machine, and calcined at 380 ° C. for 3 hours in a nitrogen stream in a firing furnace as a catalyst.

In order to evaluate the obtained catalyst, 0.3 g of a 20-28 mesh pulverized and sized particle was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and this reaction tube was heated in a night bath (temperature: 290). ) And a composition gas (5% by volume of acrolein, 8% by volume of oxygen, 15% by volume of steam, 72% by volume of nitrogen gas) is introduced into the reaction tube, and SV (space velocity; raw material gas per unit time) is introduced. The flow rate / apparent volume of catalyst charged was reacted at 14900 / hr ⁻¹ .

  As a result of the reaction, the acrolein conversion rate was 99.0%, the acrylic acid selectivity was 97.2%, and the acrylic acid yield was 96.2%.

Example 3
A composite metal oxide in which the empirical formula of the constituent components excluding oxygen is Mo ₁₂ V _2.4 Nb ₁ W _0.5 Cu ₂ Sb ₁ Si ₂₀₀ C ₂₀₀ was prepared as follows.
First, 1446 ml of pure water is heated to 80 ° C., and 201 g of ammonium paramolybdate, 26.7 g of ammonium metavanadate, 12.0 g of citric acid, and 21.9 g of ammonium metatungstate are dissolved while sequentially stirring. did. To this was added 13.8 g of antimony trioxide, and an aqueous copper sulfate solution in which 47.3 g of copper sulfate was dissolved in 204 ml of pure water was added, and 18.7 g of niobium hydroxide was added and stirred to obtain a slurry solution.

  To this slurry solution, 761 g of silicon carbide powder was added and mixed thoroughly. The slurry liquid was heated to 130 ° C. and dried. 1.5% by weight of graphite was added to and mixed with this, molded with a small tableting machine, and calcined at 380 ° C. for 3 hours in a nitrogen stream in a firing furnace as a catalyst.

In order to evaluate the obtained catalyst, 0.3 g of a 20-28 mesh pulverized and sized particle was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and this reaction tube was heated in a night bath (temperature: 290). ) And a composition gas (5% by volume of acrolein, 8% by volume of oxygen, 15% by volume of steam, 72% by volume of nitrogen gas) is introduced into the reaction tube, and SV (space velocity; raw material gas per unit time) is introduced. The flow rate / apparent volume of catalyst charged was reacted at 14900 / hr ⁻¹ .

  As a result of the reaction, acrolein conversion was 99.0%, acrylic acid selectivity was 98.7%, and acrylic acid yield was 97.7%.

Comparative Example A composite metal oxide in which the empirical formula of constituent components excluding oxygen was Mo ₁₂ V _2.4 Nb ₁ Cu ₂ Si ₂₀₀ C ₂₀₀ was prepared as follows.
First, 1446 ml of pure water was heated to 80 ° C., and 207 g of ammonium paramolybdate and 27.5 g of ammonium metavanadate were dissolved while sequentially stirring. To this was added an aqueous copper sulfate solution in which 48.6 g of copper sulfate was dissolved in 204 ml of pure water, and 19.3 g of niobium hydroxide was further added and stirred to obtain a slurry solution.

  782 g of silicon carbide powder was added to the slurry solution, and the mixture was sufficiently stirred and mixed. The slurry liquid was heated to 130 ° C. and dried. 1.5% by weight of graphite was added to and mixed with this, molded with a small tableting machine, and calcined at 380 ° C. for 3 hours in a nitrogen stream in a firing furnace as a catalyst.

  The reactivity of the obtained catalyst was evaluated under exactly the same conditions as in the examples. As a result of the reaction, the acrolein conversion rate was 99.0%, the acrylic acid selectivity was 97.0%, and the acrylic acid yield was 96.0% at a night bath temperature of 296 ° C.

  Thus, the comparative example in which no organic acid was added had a low acrylic acid selectivity, and the yield was 1.6% lower than that in Example 1.

  In contrast, Example 1, Example 2, and Example 3 to which an organic acid was added were all excellent in acrolein conversion, acrylic acid selectivity, and acrylic acid yield, so that the gas phase catalytic oxidation reaction of acrolein could be performed efficiently. It was.

  The catalyst produced by the process of the present invention is used for the gas phase catalytic oxidation of unsaturated aldehydes with molecular oxygen-containing gas to produce the corresponding unsaturated carboxylic acid in high yield. The produced unsaturated carboxylic acids such as acrylic acid are used in a wide range of applications as raw materials for various chemicals, monomers for general-purpose resins, monomers for functional resins such as water-absorbing resins, flocculants, and thickeners. The

Claims (5)

_{Formula: Mo 12 V a X b Cu} c Y d C e Si f O g
(Wherein X represents at least one element selected from Nb and W, Y represents at least one element selected from the group consisting of Sb, Mg, Ca, Sr, Ba and Zn; b, c, d, e, f and g indicate the atomic ratio of each element, and 0 <a ≦ 12, 0 ≦ b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 ≦ e ≦ 1000, 0 ≦ f ≦ 1000 is satisfied, and g is the number of oxygen atoms necessary to satisfy the oxidation state of other elements excluding Si and C among the component elements) In the production of a catalyst, the source compound of each component element is integrated in the presence of an organic acid in an aqueous medium system, and the aqueous solution or dispersion of the resulting integrated product is dried, molded, and calcined. A method for producing a composite oxide catalyst.   2. The method for producing a composite oxide catalyst according to claim 1, wherein the organic acid is present in an amount of 0.001 to 1 mole relative to 1 mole of molybdenum.   The method for producing a composite oxide catalyst according to claim 1 or 2, wherein the organic acid is at least one selected from the group consisting of citric acid, oxalic acid and malic acid.   The composite oxide according to any one of claims 1 to 3, wherein the composite oxide catalyst is a catalyst for producing a corresponding unsaturated carboxylic acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas. A method for producing a catalyst.   A method for producing a corresponding acrylic acid by vapor-phase catalytic oxidation of acrolein with a molecular oxygen-containing gas in the presence of the composite oxide catalyst produced by the production method according to claim 1.