JP2006007205A - Compound oxide catalyst and its manufacturing method - Google Patents

Abstract

A process for producing a complex 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. provide.
The composite oxide catalyst is represented by the following formula (I), has a specific surface area of 0.5 to 10 m ² / g, and a pore volume of 0.1 to 0.9 cc / g. The pore volume occupied by pores having a pore diameter of less than 0.1 to 1 μm is 10% or more of the total pore volume, and the pore volume occupied by pores having a pore diameter of less than 1 to 10 μm is 30% or more of the total pore volume, the pore volume occupied by pores having a pore diameter of less than 0.1 μm is 20% or less of the total pore volume, and further occupied by pores having a pore diameter of 10 μm or more The resulting pore volume has a pore size distribution that is 10% or less of the total pore volume. _{Mo 12 V a Nb b Cu c} X d Si c C f O g (I)
[Selection figure] None

Description

  The present invention relates to a composite oxide catalyst for producing an 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, and the production thereof. Regarding the method.

  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 conversion rate of unsaturated aldehyde and selectivity of unsaturated carboxylic acid as a target product. It is done. 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 product, acrylic acid, greatly increases at the level of hundreds to thousands of tons. Therefore, improvement in catalyst performance such as the conversion rate of raw material unsaturated aldehyde and the selectivity of unsaturated carboxylic acid contributes greatly to effective utilization of resources and rationalization of processes, even if only 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. As the composite oxide catalyst having an excellent performance for the, for example, Patent Document _{1, Mo 12 Nb a V b} Cu o Si d C e X f Y g Z h O i ( wherein, X is an alkali metal And at least one element selected from Tl, Y represents at least one element selected from Mg, Ca, Sr, Ba and Zn, and Z represents W, Ce, Sn, Cr, Mn, Fe Represents at least one element selected from Co, Y, Nd, Sm, Ge and Ti, wherein a, b, c, d, e, f and g represent the atomic ratio of each element, and a represents 0 < a ≦ 12, 0 <b ≦ 10, 0 <c ≦ 8, 0 <d ≦ 1000, 0 <e ≦ 1000, 0 ≦ f ≦ 2, 0 ≦ g <5, 0 ≦ h <5, i A catalyst having a composition having a number determined by the degree of oxidation of each component excluding Si and C among the components is proposed.

  However, although such a composite oxide catalyst exhibits excellent performance as it is, it is desired to further improve the conversion rate of the raw material unsaturated aldehyde and the selectivity of the unsaturated carboxylic acid.

Patent Document 2 discloses a general formula (Mo) a (V) b (A) c (B) d (C) e (D) f (O) x (where A is selected from W and Nb). B represents at least one element selected from Fe, Cu, Bi, Cr, and S, and C represents at least one element selected from alkali metals and alkaline earth metals. A = 12, b = 2 to 14, c = 0 to 12, d = 0 to 6, e = 0 to 6, f = 0 to 30), and the specific surface area is 0 .50 to 15.0 m ² / g, pore volume 0.10 to 0.90 cc / g, occupied by pores of 0.1 to 1.0 μm, 1.0 to 10 μm and 10 to 100 μm, respectively. A catalyst having a pore distribution in which the pore volume occupies at least 10% or more of the total pore volume is disclosed. Patent Document 2 discloses that a molded catalyst having such a pore distribution has a performance superior to that of normal molding when the centrifugal fluid coating method is used.

Patent Document 2 discloses that the characteristics of the catalyst are controlled by controlling the pore distribution of the catalyst. However, the performance provided by the use of such a catalyst is insufficient. Improvement of the conversion rate of high raw material unsaturated aldehyde and the selectivity of unsaturated carboxylic acid is desired.
JP 2003-200055 A Japanese Patent Publication No. 5-70502

  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, A composite oxide catalyst that exhibits stable performance over a long period of time and a method for producing the same are provided.

  As a result of diligent research to achieve the above object, the present inventor found that Mo, V, Nb, Cu, X, Si, and C having the same or similar composition as those of Patent Document 1 and Patent Document 2 described above. The composite oxide catalyst is contained in the catalyst. By selecting a new range different from the pore distribution disclosed in Patent Document 2 and the like as the pore distribution of the catalyst, the catalyst performance, particularly the object It has been found that the selectivity of the unsaturated carboxylic acid is improved.

  The composition of the catalyst in the present invention is the same or similar to that of Patent Document 1, but strictly speaking, it is clearly different from that of Patent Document 2 in that the catalyst of the present invention contains carbon atoms. Is different. The pore distribution of the catalyst of the present invention is clearly different from the pore distribution of the catalyst disclosed in Patent Document 2, which seems to be due to the difference in the composition of the catalyst. Actually, in the case of the catalyst of the composition of the present invention, as shown in a comparative example described later, the catalyst has excellent performance when it has a pore distribution specified by the present invention.

  Furthermore, when the present inventors produce a catalyst having the above specific composition and pore distribution according to the present invention, two or more types of silicon carbide having different particle diameters are used as source compounds for Si and C contained in the catalyst. It has been found that when a powder is used, the pore size distribution of the resulting catalyst is easily controlled, and the catalyst having the specific pore size distribution of the present invention can be produced satisfactorily. The control of the pore size distribution by this method can be applied to the case of a molded body catalyst as well as a catalyst of a single catalyst component. Further, as a molding method in the production of the adult catalyst of the present invention, an extrusion molding method or a tableting molding method is used without using a special molding method such as the centrifugal fluid coating method disclosed in Patent Document 2. Therefore, it is industrially advantageous because a normal molding method such as can be used.

Thus, the present invention is characterized by the following gist.
(1) A composite oxide catalyst used in the production of a corresponding unsaturated fatty acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas, represented by the following formula (I): And the specific surface area is 0.5 to 10 m ² / g, the pore volume is 0.1 to 0.9 cc / g, and the pore volume occupied by pores having a pore diameter of less than 0.1 to 1 μm is 10% or more of the total pore volume, the pore volume occupied by pores having a pore diameter of less than 1 to 10 μm is 30% or more of the total pore volume, and the pores having a pore diameter of less than 0.1 μm The pore volume occupied is not more than 20% of the total pore volume, and the pore volume occupied by pores having a pore diameter of 10 μm or more has a pore size distribution that is not more than 10% of the total pore volume. A complex oxide catalyst characterized.

_{Mo 12 V a Nb b Cu c} X d Si e C f O g (I)
(In the formula, each component and variable have the following meanings. X represents at least one element selected from the group consisting of W and Sb. A, b, c, d, e, f and g are each element. 0 <a ≦ 12, 0 <b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 <e ≦ 1000, 0 <f ≦ 1000, and g represents the formula (I ) Is determined by the degree of oxidation of each component)
(2) The composite oxide catalyst according to the above (1), wherein the catalyst is a cylindrical or ring shaped catalyst.
(3) Two or more types of silicon carbide powders having different particle diameters are used as Si and C source compounds contained in the catalyst, and the source compounds of the silicon carbide powder and other elements contained in the catalyst Of the composite oxide catalyst according to (1) or (2) above, wherein an aqueous solution or dispersion of the resulting integrated product is dried to prepare a powder, and the powder is calcined. Production method.
(4) The composite oxide catalyst according to (3), wherein the two or more types of silicon carbide powders having different particle sizes are a silicon carbide powder having an average particle size of 5 μm or more and a silicon carbide powder having an average particle size of less than 5 μm. Production method.
(5) The method for producing a composite oxide catalyst according to the above (3) or (4), wherein the powder is extruded or tableted before firing, and the molded product is fired.
(6) 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 according to (1) or (2).
(7) Acrolein is vapor-phase contact oxidized with a molecular oxygen-containing gas in the presence of the composite oxide catalyst obtained by the production method according to any one of (3) to (5) 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 composite oxide catalyst that provides stable performance over a long period of time.

  Further, according to the production method of the present invention, the pore distribution of the obtained catalyst can be easily controlled, and therefore the catalyst having the specific pore diameter distribution can be produced satisfactorily. Further, the control of the pore size distribution by this method can be applied to the molded body catalyst. In addition, as a molding method in the case of the molded body catalyst of the present invention, an extrusion molding method, a tableting molding method or the like is usually used without using a special molding method disclosed in Patent Document 2, such as the centrifugal fluid coating method. Therefore, it is industrially advantageous.

  The composite oxide catalyst produced in the present invention is represented by the above formula (I). In the formula (I), X, a, b, c, d, e, f, and g are as described above. Among these, 0.1 ≦ a ≦ 6, 0.1 ≦ b ≦ 6, 0.1 ≦ c ≦ 6, 0.01 ≦ d ≦ 6, 5 ≦ e ≦ 500, and 5 ≦ f ≦ 500 are preferable.

The catalyst having the above composition in the present invention has a specific surface area of 0.5 to 10 m ² / g, preferably 0.7 to ⁵ m ² / g, and a pore volume of 0.1 to 0.9 cc. / G, preferably 0.15 to 0.5 cc / g. The pore distribution is such that the pore volume occupied by pores having a pore diameter of less than 0.1 to 1 μm is 10% or more, preferably 15 to 40% of the total pore volume. The pore volume occupied by pores less than 10 μm is 30% or more of the total pore volume, preferably 45-80%, and the pore volume occupied by pores having a pore diameter of less than 0.1 μm The pore volume is 20% or less, preferably 15% or less of the pore volume, and the pore volume occupied by pores having a pore diameter of 10 μm or more is 10% or less, preferably 5% or less of the total pore volume. Even if the catalyst composition is the same, when such a pore distribution is not provided, the catalyst performance is lowered as shown in a comparative example described later. Among the pore distributions, the sum of the pore volume occupied by pores having a pore diameter of less than 0.1 to 1 μm and the pore volume occupied by pores having a pore diameter of less than 1 to 10 μm is the total pore size. Even better performance is obtained when the volume is 60% or more, preferably 80% or more.

  In addition, the specific surface area as used in the field of this invention is a surface area per unit weight of a catalyst measured by the BET method by nitrogen adsorption, and the pore diameter and pore volume are determined by measurement with a porosimeter by a mercury intrusion method. The pore diameter and the pore volume per unit weight of the catalyst.

  The composite oxide catalyst of the present invention integrates Mo, V, Nb, Cu, X, Si and C source compounds, which are components constituting the catalyst composition represented by formula (I), in an aqueous medium system. Then, an aqueous solution or dispersion of the resulting integrated product is dried to prepare a powder, and the powder is fired. The integration here means that each element is uniformly contained by mixing a source compound containing each component element in an aqueous system preferably consisting of an aqueous solution or an aqueous dispersion, and aging treatment as necessary. That means.

  (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, or a method in which (a) to (d) are combined. Included in the integration of the component element source compounds in aqueous systems.

  Here, as described in the Chemical Dictionary (Kyoritsu Shuppan), the above-mentioned “ripening” means that “industrial raw materials or semi-finished products are processed and processed under specific conditions such as constant temperature for a certain period of time. This refers to an operation for obtaining physical properties, chemical properties, raising or progressing a predetermined reaction. In addition, said fixed time says the range of 1 minute-24 hours in this invention, and said fixed temperature is the range of room temperature-200 degreeC.

  In the integration described above, not only the source compound of each element but also support materials such as alumina, silica, and refractory oxide are included as targets for such integration.

  The supply component compound of the catalyst component may be any compound that becomes an oxide by firing except for the silicon carbide compound. Examples of the raw material for the catalyst constituent element compound include molybdenum compounds, niobium compounds, vanadium compounds, and copper compounds. Specific examples of compounds include halides, sulfates, nitrates, ammonium salts, oxides, carboxylates, ammonium carboxylates, ammonium halides, hydrogenates, acetylacetonates, alkoxides, etc. An example is given.

  Specific examples of silicon and carbon source compounds include green silicon carbide and black silicon carbide, and silicon carbide is preferably a fine powder. Examples of the silicon supply source include colloidal silica, powder or granular silica, and examples of the aluminum supply source include alumina. These catalyst constituent compounds may be used alone or in combination of two or more.

  In the present invention, in particular, as described above, when at least two types of silicon carbide (SiC) powders having different particle diameters are used as Si and C source compounds, This is preferable because the pore size distribution can be controlled. In general, when a silicon carbide powder having a small particle diameter is used, a catalyst having a large proportion of pore volume having a small pore diameter is obtained. On the other hand, when a silicon carbide powder having a large particle diameter is used, a fine catalyst is obtained. A catalyst having a large proportion of the pore volume having a large pore diameter is obtained. In the present invention, it has been found that a catalyst having the above-described pore size distribution can be easily obtained by mixing silicon carbide powder having an average particle diameter of 5 μm or more and silicon carbide powder having an average particle diameter of less than 5 μm. The difference between the average particle diameters of both is preferably 3 μm or more, particularly preferably 5 μm or more. The use ratio of the silicon carbide powder having an average particle diameter of 5 μm or more and the silicon carbide powder having an average particle diameter of less than 5 μm to the former / the latter (weight ratio) is preferably 20 to 95/80 to 5, particularly preferably 70 to 95 / 30-5 is particularly preferable.

  The manufacturing process of the catalyst of the present invention will be described in order. First, an aqueous solution or water dispersion of the above-described catalyst component supply source compound is prepared. Hereinafter, unless otherwise specified, these aqueous solutions or aqueous dispersions are referred to as slurry liquids.

  The slurry liquid can be obtained by uniformly mixing the source compound of each component of the catalyst and water. The proportion of each constituent component used in the slurry is used so that the atomic ratio of each catalyst component falls within the composition range described above.

  The amount of water used in the slurry liquid is not particularly limited as long as the total amount of the source compound of each component can be completely dissolved or uniformly mixed, but is appropriately determined in consideration of the following heat treatment method and temperature. do it. Usually, it is 100 to 2000 parts by weight with respect to 100 parts by weight of the total weight of the source compound of each component. If the amount of water is less than the above predetermined amount, the source compound of each component may not be completely dissolved or may not be uniformly mixed. Moreover, if the amount of water exceeds the predetermined amount, a problem arises that the energy cost during heat treatment is increased. The integration of the catalyst components proceeds through mixing and stirring in the preparation process of the slurry liquid, but in order to further promote the integration, it is preferably room temperature to 200 ° C, particularly preferably 70 ° C to 100 ° C, preferably The aging treatment is suitable for 1 minute to 24 hours, particularly preferably 30 minutes to 6 hours.

  Next, the slurry liquid obtained in the above step is preferably dried. The drying method is not particularly limited as long as the slurry liquid can be completely 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 a slurry liquid state to a homogeneous powder state in a short time.

  The drying temperature varies depending on the concentration of the slurry liquid, the feeding speed, and the like, but is usually 90 to 200 ° C., preferably 130 to 170 ° C. at the outlet temperature of the dryer. Moreover, it is preferable to dry so that the particle size of dry powder may be 10-200 micrometers.

  The composite oxide catalyst obtained by the production method of the present invention can also be obtained by molding the powder after the heat treatment. There is no particular limitation on the molding method, and it is preferable to mold the heat-treated powder by mixing it with a molding aid such as a binder. Preferred binders include silica, graphite and crystalline cellulose when tableting the heat-treated powder, and silica gel, diatomaceous earth, alumina powder and the like when extruding. About 1 to 50 parts by weight of the binder is preferably used with respect to 100 parts by weight of the heat-treated powder.

  Further, if necessary, inorganic fibers such as ceramic fibers and whiskers can be used as the strength improving material, thereby improving the mechanical strength of the catalyst. However, fibers that react with catalyst components such as potassium titanate whiskers and basic magnesium carbonate whiskers are not preferred. As the strength improving material, ceramic fiber is particularly preferable. The amount of these fibers used is usually 1 to 30 parts by weight with respect to 100 parts by weight of the heat-treated powder. The molding aid and the strength improver are usually used by mixing with heat-treated powder.

  The powder mixed with the molding aid, the strength improver and the like can be molded by an appropriate molding method such as (A) tableting molding, (B) extrusion molding, or (C) coating support molding on a spherical carrier. As the shape of the molded body, an appropriate shape such as a pellet shape, a spherical shape, a cylindrical shape, and a ring shape can be selected. Is preferred.

  Next, the molded product can be fired to obtain a composite oxide catalyst. The firing temperature can usually be 250 to 600 ° 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. This is because when the firing temperature is too low, thermal diffusion of the molybdenum element is not sufficient, and when it is too high, the molybdenum element may be lost by sublimation.

  Means for producing a corresponding unsaturated carboxylic acid by vapor-phase oxidation of an unsaturated aldehyde using a molecular oxygen-containing gas using the catalyst produced according to the present invention can be performed by an existing method. 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 acrolein conversion rate, 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 catalyst in which the composition 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 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 liquid.

  To this slurry liquid, 626 g of silicon carbide powder having an average particle diameter of 7 μm and 156 g of silicon carbide powder having an average particle diameter of 1 μm were added and 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 pulverized and sized catalyst of 20 to 28 mesh was charged into a U-shaped reaction tube having an inner diameter of 4 mm, and this reaction tube was placed in a heated nighter bath. Gas (acrolein: 5% by volume, oxygen: 8% by volume, steam: 15% by volume, nitrogen gas: 72% by volume) was introduced, and SV (space velocity; flow rate of raw material gas per unit time / filled catalyst) The apparent volume of the reaction was 14900 / hr ⁻¹ .

  The night bath refers to a salt bath in which a reaction tube is put into a heat medium made of an alkali metal nitrate and reacts. This heat medium melts at 200 ° C. or higher, and can be used up to 400 ° C. This reaction bath is suitable for oxidation reactions with a large exotherm.

  Table 1 and Table 1 show the results of physical property measurements such as specific surface area, pore volume, and pore volume ratio obtained for the composite oxide catalyst obtained above, and acrolein oxidation reaction using the obtained composite oxide. It was shown in 2.

Example 2
A composite metal oxide catalyst in which the composition formula of the constituent components excluding oxygen was 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 was heated to 80 ° C., and 201 g of ammonium paramolybdate, 26.7 g of ammonium metavanadate, and 21.9 g of ammonium metatungstate were dissolved with sequential stirring. To this was added 13.8 g of antimony trioxide, a copper sulfate aqueous 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 liquid, 626 g of silicon carbide powder having an average particle diameter of 7 μm and 156 g of silicon carbide powder having an average particle diameter of 1 μm were added and 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.
Tables 1 and 2 show the results of measurement of physical properties such as the specific surface area of the obtained composite oxide catalyst and the acrolein oxidation reaction using the obtained composite oxide.

Comparative Example 1
A composite metal oxide catalyst in which the composition 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 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 liquid.

To this slurry liquid, 782 g of silicon carbide powder having an average particle diameter of 7 μm was added and 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.
Tables 1 and 2 show the results of measurement of physical properties such as the specific surface area of the obtained composite oxide catalyst and the acrolein oxidation reaction using the obtained composite oxide.

Comparative Example 2
A composite metal oxide catalyst in which the composition 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 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 liquid.

To this slurry liquid, 782 g of silicon carbide powder having an average particle diameter of 1 μm was added and sufficiently mixed with stirring. 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 calcining furnace as a catalyst. The reactivity of the obtained catalyst was evaluated under exactly the same conditions as in the examples.
Tables 1 and 2 show the results of measuring physical properties such as the specific surface area of the obtained composite oxide catalyst and the acrolein oxidation reaction using the obtained composite oxide.

  In Table 1, the ratio of the pore volume means the ratio of the pore volume occupied by the pores existing at 0.1 to 1 μm or the pores existing at 1 to 10 μm in the total pore volume.

  The catalyst obtained in Comparative Example 1 has an excessively small pore volume of 0.1 to 1 μm, and the catalyst obtained in Comparative Example 2 has an excessively small pore volume of 1 to 10 μm. Both were lower than those of Examples 1 and 2.

  The catalyst of the present invention is used in a step of producing an unsaturated carboxylic acid from an unsaturated aldehyde as a raw material, and is preferably used in a step of producing acrylic acid by oxidizing acrolein. That is, the catalyst of the present invention usually produces an unsaturated carboxylic acid from an olefin by dividing it into two steps of producing an unsaturated aldehyde by oxidation of an olefin and then producing an unsaturated carboxylic acid by oxidation of the unsaturated aldehyde. In this case, it is useful for the production of an unsaturated carboxylic acid by oxidation of an unsaturated aldehyde, which is the latter stage.

  Unsaturated carboxylic acids such as acrylic acid produced using the catalyst of the present invention are raw materials for various chemicals, monomers for general-purpose resins, monomers for functional resins such as water-absorbing resins, flocculants, and thickeners. Used for a wide range of purposes.

Claims (7)

A composite oxide catalyst used in the production of a corresponding unsaturated fatty acid by vapor-phase catalytic oxidation of an unsaturated aldehyde with a molecular oxygen-containing gas, which is represented by the following formula (I) and has a specific surface area 0.5 to 10 m ² / g, the pore volume is 0.1 to 0.9 cc / g, and the pore volume occupied by pores having a pore diameter of less than 0.1 to 1 μm is the total pores. 10% or more of the volume, and the pore volume occupied by pores having a pore diameter of less than 1 to 10 μm is 30% or more of the total pore volume, and the fine volume occupied by pores having a pore diameter of less than 0.1 μm. The pore volume is 20% or less of the total pore volume, and further has a pore size distribution in which the pore volume occupied by pores having a pore diameter of 10 μm or more is 10% or less of the total pore volume. Complex oxide catalyst.
_{Mo 12 V a Nb b Cu c} X d Si e C f O g (I)
(In the formula, each component and variable have the following meanings. X represents at least one element selected from the group consisting of W and Sb. A, b, c, d, e, f and g are each element. 0 <a ≦ 12, 0 <b ≦ 12, 0 <c ≦ 12, 0 ≦ d ≦ 8, 0 <e ≦ 1000, 0 <f ≦ 1000, and g is the formula ( I) is a number determined by the degree of oxidation of each of the above components)   The composite oxide catalyst according to claim 1, wherein the catalyst is a columnar or ring shaped catalyst.   Two or more kinds of silicon carbide powders having different particle diameters are used as Si and C source compounds contained in the catalyst, and the silicon carbide powder and other element source compounds contained in the catalyst are aqueous. The method for producing a composite oxide catalyst according to claim 1, wherein the powder is prepared by drying an aqueous solution or dispersion of the integrated product obtained by integration in a medium system and calcining the powder.   The method for producing a composite oxide catalyst according to claim 3, wherein the two or more types of silicon carbide powders having different particle sizes are a silicon carbide powder having an average particle size of 5 µm or more and a silicon carbide powder having an average particle size of less than 5 µm.   The method for producing a composite oxide catalyst according to claim 3 or 4, wherein the powder is extruded or tableted before firing, and the molded product is fired.   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 according to claim 1 or 2.   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 obtained by the production method according to claim 3.