Catalyst, method for producing catalyst, and methods for producing α,β-unsaturated aldehyde, α,β-unsaturated carboxylic acid, and α,β-unsaturated carboxylic acid ester

Abstract

To provide a catalyst that ensures high yield of target products such as α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids.SOLUTION: A catalyst containing at least molybdenum, wherein the COD (chemical oxygen demand) of the catalyst is more than 300 ppm and less than 11000 ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst, a method for producing the catalyst, and a method for producing an α,β-unsaturated aldehyde, an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid ester. [Background technology]

[0002] Molybdenum-containing catalysts are often used in processes for producing organic compounds such as α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids. It is known that the catalytic performance of these catalysts varies depending on their physical properties, and many studies have been conducted to control their physical properties. Patent Document 1 describes a method for producing an unsaturated aldehyde from an olefin and / or alcohol as a raw material, which uses a catalyst containing molybdenum, bismuth, iron, cobalt, and a lanthanoid element, and Fe 2+ / (Fe 2+ +Fe 3+ It is described that a catalyst in which the ratio of

[0003] Patent Document 2 describes that a catalyst for producing unsaturated aldehydes and / or unsaturated carboxylic acids, which is made of a composite oxide containing molybdenum, bismuth, and iron, can be calcined in the presence of a reducing substance and the mass loss rate at that time controlled to obtain a catalyst with excellent mechanical strength. Patent Document 3 describes that, regarding a heteropolyacid-based catalyst for producing methacrylic acid, which contains a water-soluble heteropolyacid and a poorly water-soluble heteropolyacid salt, by controlling the degree of reduction of the water-soluble heteropolyacid and the poorly water-soluble heteropolyacid salt of the catalyst, a catalyst with high productivity for methacrylic acid can be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-161775 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-274034 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-284439 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the catalysts described in Patent Documents 1 to 3 did not necessarily provide sufficient yields of α,β-unsaturated aldehydes or α,β-unsaturated carboxylic acids. Therefore, from the viewpoint of further improving catalytic performance, it is necessary to control the physical properties of the catalysts. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst that provides a high yield of a target product such as an α,β-unsaturated aldehyde or an α,β-unsaturated carboxylic acid. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to achieve the above object, and as a result have discovered that, for molybdenum-containing catalysts, COD (chemical oxygen demand), an indicator of the oxidation-reduction state of the catalyst, has a significant effect on catalytic performance, and that controlling the COD within a certain range can provide a catalyst that produces a high yield of the target product, leading to the completion of the present invention.

[0007] That is, the present invention includes the following. [1]: A catalyst containing at least molybdenum, wherein the COD (chemical oxygen demand) of the catalyst is more than 300 ppm and less than 11,000 ppm. [2]: The COD (ppm) value is calculated based on the specific surface area S (m 2 / g) (COD / S) is 43μg / m 2 exceeding 3600 μg / m 2 The following is [1] The catalyst according to claim 1. [3]: The catalyst according to [1] or [2], which is used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether. [4]: The catalyst according to any one of [1] to [3], which has a composition represented by the following formula (1): Mo a1 Bi b1 Fe c1 M d1 X e1 Y f1 Si g1 (NH4) h1 O i1 (1) (In the formula (1), Mo, Bi, Fe, Si, NH4, and O represent molybdenum, bismuth, iron, silicon, ammonium, and oxygen, respectively. M represents at least one element selected from the group consisting of cobalt and nickel. X represents at least one element selected from the group consisting of zinc, chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum, tungsten, antimony, phosphorus, boron, sulfur, selenium, tellurium, cerium, and titanium.) represents an element. Y represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium. a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the molar ratio of each component, and when a1 = 12, b1 = 0.01 to 3, c1 = 0 to 8, d1 = 0 to 12, e1 = 0 to 8, f1 = 0.001 to 2, g1 = 0 to 20, and h1 = 0 to 30, and i1 is the molar ratio of oxygen required to satisfy the valence of each component. [5]: The catalyst according to [3] or [4], wherein the COD is more than 300 ppm and not more than 2000 ppm. [6]: The catalyst according to any one of [3] to [5], wherein the COD is 400 to 1500 ppm. [7]: The COD / S is 50 to 500 μg / m 2 The catalyst according to any one of [3] to [6], which is: [8]: The catalyst according to [1] or [2], which is used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde. [9]: The catalyst according to any one of [1], [2] and [8], which has a composition represented by the following formula (2): P a2 Mo b2 V c2Cu d2 A e2 E f2 G g2 (NH4) h2 O i2 (2) (In the formula (2), P, Mo, V, Cu, NH4, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. E represents iron, zinc, chromium, magnesium, calcium, strontium, tantalum, cobalt, nickel, manganese, barium, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, selenium, and selenium.) G represents at least one element selected from the group consisting of lithium, sodium, rubidium, potassium, cesium, and thallium. a2, b2, c2, d2, e2, f2, g2, h2, and i2 represent the molar ratios of each component, and when b2 = 12, a2 ​​= 0.5 to 3, c2 = 0.01 to 3, d2 = 0.01 to 2, e2 = 0 to 3, f2 = 0 to 3, g2 = 0 to 5, h2 = 0 to 30, and i2 is the molar ratio of oxygen required to satisfy the valence of each component.

[10] : The catalyst according to [8] or [9], wherein the COD is 2500 ppm or more and less than 11000 ppm.

[11] : The catalyst according to any one of [8] to

[10] , wherein the COD is 2600 to 10000 ppm.

[12] : The COD / S is 100 to 3000 μg / m 2 The catalyst according to any one of [8] to

[11] , wherein

[13] : A method for producing a catalyst containing at least molybdenum, comprising the steps of: ) to (v). (i) mixing at least a molybdenum raw material with a solvent to obtain a slurry (liquid A); (ii) stirring the solution A for 20 to 90 minutes at a temperature 1 to 30°C lower than the boiling point of the solvent to obtain a slurry (solution B); (iii) a step of stirring the liquid B for 10 minutes to 10 hours at a temperature that is 2°C or more higher than the temperature in the step (ii) to obtain a slurry (liquid C); (iv) drying the solution C to obtain a dried product; (v) A step of calcining the dried product to obtain a catalyst.

[14] : The method for producing a catalyst according to

[13] , wherein in the step (i), 50 mass % or more of the total solvent is water.

[15] : The method for producing a catalyst according to

[13] or

[14] , wherein the temperature in the step (iii) is 1 to 20° C. higher than the boiling point of the solvent.

[16] : The method for producing a catalyst according to any one of

[13] to

[15] , wherein in the step (iii), the solution B is stirred for 90 minutes to 10 hours to obtain the solution C.

[17] : The method for producing a catalyst according to any one of

[13] to

[16] , wherein in the step (v), the dried product is calcined under a flow of an oxygen-containing gas.

[18] : The method for producing a catalyst according to any one of

[13] to

[17] , which produces a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether.

[19] : A method for producing a catalyst according to any one of

[13] to

[17] , which is for producing a catalyst used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde.

[20] : A method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether using the catalyst according to any one of [1] to [7].

[21] : A method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether using a catalyst produced by the production method according to any one of

[13] to

[18] .

[22] : A method for producing an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde using the catalyst according to any one of [1], [2], and [8] to

[12] .

[23] : A method for producing an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde using a catalyst produced by the production method according to any one of

[13] to

[17] and

[19] .

[24] : A method for producing an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde produced by the method according to

[20] or

[21] .

[25] : A method for producing an α,β-unsaturated carboxylic acid ester, comprising producing an α,β-unsaturated carboxylic acid ester from an α,β-unsaturated carboxylic acid produced by the production method according to any one of

[20] to

[24] . [Effects of the Invention]

[0008] According to the present invention, a catalyst can be provided that provides a high yield of the target product. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following. Furthermore, the description of a numerical range such as "XX or more and YY or less" or "XX to YY" means a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

[0010] [catalyst] The catalyst according to the present invention contains at least molybdenum and has a COD (chemical oxygen demand) of more than 300 ppm and less than 11,000 ppm. By using such a catalyst, it is possible to produce a target product from raw materials in high yield. From the viewpoint of the yield of the target product, the catalyst according to the present invention is preferably an oxidation catalyst, and more preferably a catalyst for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid. Specifically, the catalyst is preferably a catalyst for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether, or a catalyst for producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde. Note that the phrase "producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid" means that either one of an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid or both may be produced.

[0011] (Catalyst Composition) The catalyst according to the present invention preferably contains at least molybdenum and has a composition represented by the following formula (1) or (2) from the viewpoint of the yield of the target product. When the catalyst according to the present invention is a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether, the catalyst having the composition represented by the following formula (1) allows the α,β-unsaturated aldehyde and / or the α,β-unsaturated carboxylic acid to be obtained in high yield. When the catalyst according to the present invention is a catalyst used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde, the catalyst having the composition represented by the following formula (2) allows the α,β-unsaturated carboxylic acid to be obtained in high yield. The catalyst components may contain small amounts of elements not represented by the following formula (1) or (2).

[0012] Mo a1 Bi b1 Fe c1 M d1 X e1 Y f1 Si g1 (NH4) h1 O i1 (1) In formula (1), Mo, Bi, Fe, Si, NH4, and O represent molybdenum, bismuth, iron, silicon, ammonium, and oxygen, respectively. M represents at least one element selected from the group consisting of cobalt and nickel. X represents at least one element selected from the group consisting of zinc, chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum, tungsten, antimony, phosphorus, boron, sulfur, selenium, tellurium, cerium, and titanium. Y represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium. a1, b1, c1, d1, e1, f1, g1, h1, and i1 represent the molar ratio of each component, and when a1=12, b1=0.01 to 3, c1=0 to 8, d1=0 to 12, e1=0 to 8, f1=0.001 to 2, g1=0 to 20, and h1=0 to 30, and i1 is the molar ratio of oxygen required to satisfy the valence of each component.

[0013] P a2 Mo b2 V c2 Cu d2 A e2 E f2 G g2 (NH4) h2 O i2 (2) In formula (2), P, Mo, V, Cu, NH4, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. E represents at least one element selected from the group consisting of iron, zinc, chromium, magnesium, calcium, strontium, tantalum, cobalt, nickel, manganese, barium, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium, and lanthanum. G represents at least one element selected from the group consisting of lithium, sodium, rubidium, potassium, cesium, and thallium. a2, b2, c2, d2, e2, f2, g2, h2, and i2 represent the molar ratios of each component. When b2=12, a2=0.5 to 3, c2=0.01 to 3, and d2 = 0.01 to 2, e2 = 0 to 3, f2 = 0 to 3, g2 = 0 to 5, h2 = 0 to 30, and i2 is the molar ratio of oxygen required to satisfy the valence of each of the above components.

[0014] The molar ratio of each component is determined by analyzing the catalyst dissolved in aqueous ammonia using ICP emission spectrometry, and the molar ratio of ammonium radical is determined by analyzing the catalyst using the Kjeldahl method.

[0015] When the catalyst according to the present invention has the elemental composition represented by formula (1), from the viewpoint of the yield of α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid, when a1 = 12, the lower limit of b1 is preferably 0.03 or more, more preferably 0.05 or more. The upper limit of b1 is preferably 2 or less, more preferably 1 or less. The lower limit of c1 is preferably 0.01 or more, more preferably 0.1 or more, and even more preferably 1 or more. The upper limit of c1 is preferably 5 or less, more preferably 3 or less. The lower limit of d1 is preferably 0.01 or more, more preferably 0.1 or more, even more preferably 1 or more, and particularly preferably 3 or more. The upper limit of d1 is preferably 10 or less, more preferably 9 or less. The lower limit of e1 is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more. The upper limit of e1 is preferably 6 or less, more preferably 4 or less. The lower limit of f1 is preferably 0.01 or more, more preferably 0.1 or more. The upper limit of f1 is preferably 1.5 or less, more preferably 1 or less. The lower limit of g1 may be 1 or more, or may be 5 or more. The upper limit of g1 is preferably 15 or less, more preferably 10 or less. The upper limit of h1 is preferably 20 or less, more preferably 10 or less.

[0016] Furthermore, when the catalyst according to the present invention has the elemental composition represented by formula (2), from the viewpoint of the yield of α,β-unsaturated carboxylic acid, when b2=12, the lower limit of a2 is preferably 0.8 or more, more preferably 1 or more. The upper limit of a2 is preferably 2.5 or less, more preferably 2 or less. The lower limit of c2 is preferably 0.1 or more, more preferably 0.2 or more. The upper limit of c2 is preferably 2.5 or less, more preferably 2 or less. The lower limit of d2 is preferably 0.05 or more, more preferably 0.1 or more. The upper limit of d2 is preferably 1 or less, more preferably 0.5 or less. The lower limit of e2 may be 0.01 or more, or may be 0.1 or more. The upper limit of e2 is preferably 2.5 or less, more preferably 2 or less. The lower limit of f2 may be 0.01 or more, or may be 0.03 or more. The upper limit of f2 is preferably 2.5 or less, more preferably 2 or less. The lower limit of g2 is preferably 0.1 or more, more preferably 0.5 or more. The upper limit of g2 is preferably 4 or less, more preferably 3 or less. The upper limit of h2 is preferably 20 or less, more preferably 10 or less.

[0017] The catalyst according to the present invention may have a carrier for supporting the catalytically active component. The carrier is not particularly limited, and examples thereof include silica, alumina, silica-alumina, magnesia, titania, and silicon carbide. Among these, silica is preferred to prevent the carrier itself from reacting. When a carrier is used in the catalyst according to the present invention, the carrier is also considered to be part of the catalyst.

[0018] (COD of catalyst) The COD of a catalyst represents the weight of oxygen molecules required to completely oxidize a unit weight of catalyst. When 1 μg of oxygen molecules is required to completely oxidize 1 g of catalyst, the COD value is 1 ppm. Here, the unit ppm represents μg / g.

[0019] The COD of the catalyst according to the present invention is greater than 300 ppm and less than 11,000 ppm. This allows the target product to be produced in high yield. The reason for this is not clear, but is presumed to be as follows: The active sites of the catalyst used to produce organic compounds such as α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids can take two states: an oxidized state and a reduced state. The active sites then undergo an oxidation-reduction cycle, changing between the oxidized and reduced states, to produce the target product. Products are produced. Therefore, for this redox cycle to operate, both the oxidized and reduced active sites must be stable. Here, the COD of a catalyst is an indicator of the abundance ratio of the oxidized and reduced states of the catalyst as a whole, not just of a specific element. When the COD of a catalyst is low, it indicates that the abundance ratio of the oxidized state is high and the oxidized state is relatively stable. On the other hand, when the COD of a catalyst is high, it indicates that the abundance ratio of the reduced state is high and the reduced state is relatively stable. When the COD of a catalyst is above 300 ppm and below 11,000 ppm, it can be said that both the oxidized and reduced states are stable. This is thought to facilitate the oxidation-reduction cycle of the catalyst, improving the yield of the target product.

[0020] The lower limit of the COD of the catalyst is preferably 400 ppm or more, more preferably 450 ppm or more, even more preferably 500 ppm or more, and particularly preferably 550 ppm or more, and the upper limit of the COD of the catalyst is preferably 10,000 ppm or less, more preferably 9,000 ppm or less, even more preferably 8,000 ppm or less, and particularly preferably 7,400 ppm or less.

[0021] The preferred range of the COD of the catalyst varies depending on the elemental composition and application of the catalyst. When the catalyst is used in a reaction requiring a large number of moles of oxygen to react with 1 mole of raw material substrate, many reduced active sites are generated during the reaction, and therefore, it is preferable that the oxidized state be more stable so that the generated reduced active sites can easily return to the oxidized state. That is, within the COD range of the catalyst according to the present invention (more than 300 ppm and less than 11,000 ppm), a relatively small COD range is preferred. On the other hand, when the catalyst is used in a reaction requiring a small number of moles of oxygen to react with 1 mole of raw material substrate, it is preferable that the reduced state be more stable because reduced active sites are less likely to be generated during the reaction. That is, within the COD range of the catalyst according to the present invention (more than 300 ppm and less than 11,000 ppm), a relatively large COD range is preferred.

[0022] As an example of a reaction for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether, the reaction for producing methacrolein by oxidizing isobutylene is shown in the following formula (4). Also, as an example of a reaction for producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde, the reaction for producing methacrylic acid by oxidizing methacrolein is shown in the following formula (5). C4H8 + O2 → C4H6O + H2O (4) C4H6O + 0.5O2 → C4H6O2(5)

[0023] The reaction shown in formula (4) requires 1 mole of oxygen molecules to oxidize 1 mole of raw material substrate. In contrast, the reaction shown in formula (5) requires 0.5 moles of oxygen molecules to oxidize 1 mole of raw material substrate, which is a smaller number of moles of oxygen molecules than the reaction shown in formula (4). Therefore, when the catalyst according to the present invention is used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether, the COD is preferably in a relatively small range. That is, the COD of the catalyst is preferably greater than 300 ppm and not more than 2000 ppm. The lower limit of the COD of the catalyst is more preferably 400 ppm or more, even more preferably 450 ppm or more, particularly preferably 500 ppm or more, and most preferably 550 ppm or more. The upper limit of the COD of the catalyst is more preferably 1500 ppm or less, even more preferably 1400 ppm or less, particularly preferably 1300 ppm or less, and most preferably 1200 ppm or less.

[0024] Furthermore, when the catalyst according to the present invention is used for producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde, the COD is preferably in a relatively large range. That is, the COD of the catalyst is preferably 2500 ppm or more and less than 11000 ppm. The lower limit of the COD of the catalyst is more preferably 2600 ppm or more, and even more preferably 2700 ppm or more. The upper limit of the COD is more preferably 10,000 ppm or less, even more preferably 9,000 ppm or less, particularly preferably 8,000 ppm or less, and most preferably 7,500 ppm or less.

[0025] The COD of the catalyst in the present invention is measured by the following procedures (1) to (9). (1): Put 0.2±0.05 g of catalyst into an Erlenmeyer flask and weigh it accurately. The weight of the catalyst weighed at this point is m (g). (2): Add 100 mL of pure water to the Erlenmeyer flask (1). (3): In the Erlenmeyer flask (2), add 10 mL of a sulfuric acid solution prepared by mixing concentrated sulfuric acid and pure water in a ratio of concentrated sulfuric acid:pure water = 1:2 (volume ratio) and 10 mL of a 5 mmol / L potassium permanganate solution. (4): Immerse the Erlenmeyer flask (3) in boiling water for 30 minutes. (5): The liquid in the Erlenmeyer flask obtained in (4) is filtered using a filter with a mesh size of 0.45 μm. (6): The filtrate obtained in (5) is immersed in boiling water for 5 minutes. (7): The filtrate obtained in (6) after immersion is placed in an Erlenmeyer flask, and 10 mL of a 12.5 mmol / L sodium oxalate aqueous solution is added. (8): The solution obtained in (7) is titrated with 5 mmol / L potassium permanganate solution until it turns a pale red color. The titration volume of the 5 mmol / L potassium permanganate solution is a (mL). (9) The COD of the catalyst is calculated using the following formula (3) from the precisely weighed value m of the catalyst and the titration amount a of the 5 mmol / L potassium permanganate aqueous solution.

number

[0026] The COD of the catalyst can be controlled within the above range, for example, by adjusting the catalyst composition as described above, or by adjusting the type of raw material, stirring time, heating time, heating temperature, calcination conditions, etc. in the catalyst production method described below. When adjusting the catalyst composition, the COD increases by increasing the molar ratio of transition metal elements such as Fe and Cu. Furthermore, a catalyst having a specified COD can be easily produced by using a method including steps (ii) and (iii) in the catalyst production method described below.

[0027] (Catalyst COD / S) The COD / S of a catalyst represents the weight of oxygen molecules required to completely oxidize the catalyst per unit surface area, and is considered to be an index of the abundance ratio of reduced states on the catalyst surface. The catalyst according to the present invention is characterized in that the COD of the catalyst is determined by the specific surface area S (m 2 COD / S (μg / m 2 ) is 43 μg / m 2exceeding 3600 μg / m 2 or less. This allows the target product to be produced in a higher yield. The reason for this is thought to be that both the oxidized and reduced states are stable even on the catalyst surface where the catalytic reaction mainly occurs, making it easier for the oxidation-reduction cycle of the catalyst to operate.

[0028] When the catalyst according to the present invention is a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether, the catalyst The COD / S of the medium is 45 to 500 μg / m 2 The lower limit of the COD / S of the catalyst is preferably 50 μg / m 2 More preferably, the upper limit of COD / S of the catalyst is 400 μg / m 2 Less than 300 μg / m is more preferable. 2 More preferably, 200 μg / m 2 Particularly preferred is 150 μg / m 2 The following are most preferred: Furthermore, when the catalyst according to the present invention is a catalyst used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde, the COD / S of the catalyst is 100 to 3000 μg / m 2 The lower limit of the COD / S of the catalyst is preferably 200 μg / m 2 More preferably, 300 μg / m 2 More preferably, 400 μg / m 2 More than 500 μg / m 2 The upper limit of COD / S of the catalyst is 2500 μg / m 2 Less than 2000 μg / m is more preferable. 2 More preferably, 1500 μg / m 2 The following are particularly preferred: The specific surface area S of the catalyst in the present invention is a value measured by nitrogen adsorption (BET one-point method, equilibrium relative pressure = 0.30) for 1.0 g of catalyst using a mixed gas of 30 vol% nitrogen and 70 vol% helium as the measurement gas. The specific surface area can be measured using, for example, a fully automatic specific surface area meter, Macsorb HM model-1200 (product name, manufactured by MOUNTECH). The specific surface area S of the catalyst can be adjusted, for example, by the calcination temperature and calcination time in step (v) described below. The specific surface area S tends to decrease when the calcination temperature is increased and the calcination time is extended. Furthermore, when producing a catalyst having a composition represented by formula (2), the specific surface area S tends to decrease by increasing the temperature of liquid A3 in step (i-4) described below.

[0029] (Catalyst structure) When the catalyst according to the present invention has the elemental composition represented by formula (2), it is preferable that the catalyst contains a Keggin-type heteropolyacid salt from the viewpoint of the yield of the target product. Whether or not the catalyst contains a Keggin-type heteropolyacid salt can be confirmed by infrared absorption analysis. Infrared absorption analysis can be performed using, for example, a NICOLET 6700 FT-IR (product name, manufactured by Thermo Electron). When a heteropolyacid salt having a Keggin structure is contained, the resulting infrared absorption spectrum has characteristic peaks near 1060, 960, 870, and 780 cm-1. To obtain a catalyst containing a heteropolyacid salt having a Keggin structure, for example, a method including producing a catalyst by a method including steps (i-3) and (i-4) described below, and adjusting the pH of solution A to 4 or less in step (i-4), or a method including calcining at 200°C or higher in step (v) described below can be mentioned.

[0030] [Catalyst manufacturing method] Another embodiment of the present invention is a method for producing a catalyst containing at least molybdenum, comprising the following steps (i) to (v): The obtained catalyst preferably has a COD of more than 300 ppm and less than 11,000 ppm. (i) A step of mixing at least a molybdenum raw material with a solvent to obtain a slurry (liquid A). (ii) A step of stirring the liquid A for 20 to 90 minutes at a temperature 1 to 30° C. lower than the boiling point of the solvent to obtain a slurry (liquid B). (iii) A step of stirring the liquid B for 10 minutes to 10 hours at a temperature at least 2°C higher than the temperature in the step (ii) to obtain a slurry (liquid C). (iv) A step of drying the solution C to obtain a dried product. (v) A step of calcining the dried product to obtain a catalyst. The method for producing a catalyst according to this embodiment may further include a molding step, which will be described later. Each step will be described in detail below.

[0031] (Step (i)) In step (i), at least a molybdenum raw material is mixed with a solvent to prepare a slurry (liquid A). Liquid A is prepared by mixing at least a molybdenum raw material with a solvent. Furthermore, raw materials for each element included in formula (1) or (2) (hereinafter also referred to as catalyst raw materials) may be further mixed. The amount of catalyst raw material used may be appropriately adjusted to obtain a desired catalyst composition.

[0032] The catalyst raw material is not particularly limited, and nitrates, carbonates, hydrogen carbonates, acetates, ammonium salts, sulfates, oxides, hydroxides, halides, oxoacids, oxoacid salts, etc. of each element can be used alone or in combination of two or more. Using a compound that acts as an oxidizing agent as the catalyst raw material tends to reduce COD and COD / S, while using a compound that acts as a reducing agent as the catalyst raw material tends to increase COD and COD / S.

[0033] Examples of molybdenum raw materials include ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, etc., with ammonium paramolybdate or molybdenum trioxide being preferred. Examples of bismuth raw materials include bismuth nitrate, bismuth oxide, bismuth subcarbonate, etc., with bismuth oxide being preferred. Examples of iron raw materials include iron nitrate, iron hydroxide, iron oxide, etc., with iron nitrate being preferred. Examples of phosphorus raw materials include phosphoric acid, phosphorus pentoxide, ammonium phosphate, cesium phosphate, etc., with phosphoric acid being preferred. Examples of vanadium raw materials include ammonium metavanadate, vanadium pentoxide, vanadium chloride, etc., with ammonium metavanadate or vanadium pentoxide being preferred. Examples of copper raw materials include copper sulfate, copper nitrate, copper oxide, copper carbonate, copper acetate, copper chloride, etc., with copper nitrate being preferred. Examples of ammonium root raw materials include ammonium bicarbonate, ammonium carbonate, ammonium nitrate, ammonia water, etc.

[0034] Furthermore, as the raw material for molybdenum, phosphorus, and vanadium, a heteropolyacid containing at least one element selected from molybdenum, phosphorus, and vanadium may be used. Examples of heteropolyacids include phosphomolybdic acid, phosphovanadomolybdic acid, and silicomolybdic acid. These may be used alone or in combination of two or more. The solvent is not particularly limited as long as it can dissolve or disperse the catalyst raw materials, but it preferably contains at least water, preferably 50 mass % or more of the total solvent is water, more preferably 80 mass % or more of the total solvent is water, and water alone may be used. The solvent may contain an organic solvent in addition to water. The organic solvent is not particularly limited, and examples include alcohol and acetone. The amount of solvent used is not particularly limited, but it is preferably 30 to 400 mass parts per 100 mass parts of the total catalyst raw materials.

[0035] <When producing a catalyst having a composition represented by formula (1)> When producing a catalyst having a composition represented by the formula (1), the step (i) preferably includes the following steps (i-1) and (i-2).

[0036] (i-1) A step of preparing a solution or slurry (Solution A1) containing molybdenum, bismuth, and the elements X and Y in formula (1), and a solution or slurry (Solution A2) containing iron and the element M in formula (1). (i-2) A step of mixing the A1 liquid and the A2 liquid to prepare the A liquid. Each step will be described below.

[0037] <<Process (i-1)>> In step (i-1), a solution or slurry (liquid A1) containing molybdenum, bismuth, and the elements X and Y in formula (1) is prepared, and a solution or slurry (liquid A2) containing iron and the element M in formula (1) is prepared. The order in which solutions A1 and A2 are prepared is not limited. Alternatively, solutions A1 and A2 may be prepared simultaneously. The amount of each catalyst raw material used is preferably adjusted so that the resulting catalyst has the composition represented by the above formula (1). The amount of solvent used is not particularly limited, but it is preferable that the amount of A1 solution is 70 to 400 parts by mass per 100 parts by mass of the total catalyst raw materials, and it is preferable that the amount of A2 solution is 30 to 230 parts by mass per 100 parts by mass of the total catalyst raw materials.

[0038] <<Process (i-2)>> In step (i-2), the A1 solution and the A2 solution obtained in step (i-1) are mixed to prepare the A solution.

[0039] <Production of a catalyst having a composition represented by formula (2)> When producing a catalyst having a composition represented by the formula (2), the step (i) preferably includes the following steps (i-3) and (i-4).

[0040] (i-3) A step of preparing a solution or slurry (Solution A3) containing at least molybdenum and phosphorus. (i-4) A step of preparing the solution A by mixing the solution A3 with a raw material of the element G in the formula (2). Each step will be described below.

[0041] <<Process (i-3)>> In step (i-3), a solution or slurry (Solution A3) containing at least molybdenum and phosphorus is prepared. Solution A3 preferably contains an element other than the element G in formula (2). Liquid A3 may contain ammonium radicals, but when the molar ratio of molybdenum in the produced catalyst is taken as 12, the molar ratio of ammonium radicals contained in Liquid A3 is preferably 3 or less. This ensures the stable formation of a heteropolyacid structure suitable for producing an α,β-unsaturated carboxylic acid in step (i-4) described below. The molar ratio of ammonium radicals contained in Liquid A3 is more preferably 1.5 or less, even more preferably 1 or less, and particularly preferably 0.6 or less. The amount of each catalyst raw material used is preferably adjusted so that the resulting catalyst has the composition represented by the above formula (2). The amount of the solvent used is not particularly limited, but is preferably 30 to 400 parts by mass per 100 parts by mass of the total catalyst raw materials. Liquid A3 is preferably prepared by heating to 80 to 130°C. By heating Liquid A3 to 80°C or higher, the dissolution rate of the catalyst raw materials can be sufficiently increased. Furthermore, by heating Liquid A3 to 130°C or lower, evaporation of the solvent can be suppressed. The lower limit of the heating temperature of Liquid A3 is more preferably 90°C or higher.

[0042] <<Process (i-4)>> In step (i-4), the A3 solution obtained in step (i-3) is mixed with a raw material for the G element in formula (2) to prepare the A solution. It is also preferable to mix a raw material for the ammonium radical in addition to the G element raw material. This allows for the stable formation of a heteropolyacid structure suitable for producing an α,β-unsaturated carboxylic acid. The raw material of the G element and the raw material of the ammonium radical are preferably dissolved or suspended in a solvent and then mixed with the A3 liquid, and more preferably dissolved in a solvent and then mixed with the A3 liquid.

[0043] When mixing the A3 solution with the G element raw material, the temperature of the A3 solution is preferably set to 30 to 99° C. This prevents localized oxidation of the catalyst when the target product is produced using the obtained catalyst. It is more preferable that the temperature of the A3 solution is 40°C or higher and 95°C or lower.

[0044] From the viewpoint of the yield of α,β-unsaturated carboxylic acid, it is preferable that the solution A obtained in step (i-4) contains a Keggin type heteropolyacid salt. The Keggin type heteropolyacid salt can be stably formed by adjusting the pH of the solution A to 4 or less, preferably 2 or less. For example, a method for adjusting the pH of the solution A to 4 or less can be mentioned in which the type and amount of the catalyst raw material are appropriately selected in the step (i-3) and nitric acid, oxalic acid, or the like is appropriately added to adjust the pH of the solution A. The pH can be measured using a pH meter. For example, a D-21 (product name, manufactured by Horiba, Ltd.) can be used as the pH meter.

[0045] (Step (ii)) In step (ii), the liquid A obtained in step (i) is stirred for 20 to 90 minutes at a temperature 1 to 30°C lower than the boiling point of the solvent to obtain a slurry (liquid B). For example, when water is used as the solvent in step (i), the boiling point of water is 100°C, so in step (ii), liquid A is stirred at 70 to 99°C. When multiple solvents with different boiling points are used in step (i), the stirring is performed at a temperature 1 to 30°C lower than the boiling point of the solvent with the largest mass proportion. In step (ii), the temperature and stirring time are set to the above conditions to adjust the solubility of the catalyst raw materials in the solvent to a constant level. This is thought to result in the formation of catalytic active sites in step (iii), which will be described later, where active sites are formed in both oxidized and reduced states, resulting in a catalyst with a COD of more than 300 ppm and less than 11,000 ppm. If the temperature in step (ii) is lower than specified or the stirring time is shorter than specified, the solubility of the catalyst raw materials tends to decrease, and the COD of the resulting catalyst tends to be 11,000 ppm or higher. On the other hand, if the temperature in step (ii) is higher than specified or the stirring time is longer than specified, the solubility of the catalyst raw materials tends to increase, and the COD of the resulting catalyst tends to be 300 ppm or lower.

[0046] The upper limit of the temperature during stirring of Solution A is preferably at least 3°C ​​lower than the boiling point of the solvent, more preferably at least 5°C lower, and the lower limit is preferably at most 25°C lower than the boiling point of the solvent, more preferably at most 20°C lower, and even more preferably at most 10°C lower. The lower limit of the stirring time within the above temperature range is preferably 30 minutes or more, more preferably 40 minutes or more, and the upper limit is preferably 80 minutes or less, more preferably 70 minutes or less.

[0047] (Step (iii)) In step (iii), the liquid B obtained in step (ii) is stirred for 10 minutes to 10 hours at a temperature at least 2° C. higher than the temperature in step (ii) to obtain a slurry (liquid C). In step (iii), active sites of the catalyst are formed. By stirring the solution B, in which the solubility of the catalyst raw materials has been adjusted in step (ii), at the above-mentioned temperature for the above-mentioned time, active sites in which both the oxidized and reduced states are stabilized are formed, and it is believed that a catalyst having a COD of more than 300 ppm and less than 11,000 ppm can be obtained. If the temperature in step (iii) is lower than specified or the stirring time is shorter than specified, the reduced state becomes more stable, and the COD of the resulting catalyst tends to be 11,000 ppm or higher. On the other hand, if the temperature in step (iii) is higher than specified or the stirring time is longer than specified, the oxidized state becomes more stable, and the COD of the resulting catalyst tends to be 300 ppm or lower.

[0048] The lower limit of the temperature during stirring of Solution B is preferably at least 5° C. higher than the temperature in step (ii), more preferably at least 6° C. higher, and even more preferably at least 8° C. higher. The upper limit is preferably at most 40° C. higher than the temperature in step (ii), more preferably at most 20° C. higher, and even more preferably at most 10° C. higher. Furthermore, the temperature at which Solution B is stirred is preferably 1 to 20°C higher than the boiling point of the solvent. For example, when water is used as the solvent in step (i), the boiling point of water is 100°C, so it is preferable to stir Solution B at 101 to 120°C in step (iii). The lower limit of the temperature at which Solution B is stirred is more preferably 2°C or higher, and even more preferably 3°C or higher, than the boiling point of the solvent. The upper limit is more preferably 10°C or lower, and even more preferably 5°C or lower, than the boiling point of the solvent.

[0049] The lower limit of the stirring time within the above temperature range is preferably 20 minutes or more, more preferably 30 minutes or more, even more preferably 60 minutes or more, particularly preferably 90 minutes or more, and most preferably 2 hours or more, and the upper limit is preferably 9 hours or less, more preferably 8 hours or less.

[0050] (Step (iv)) In step (iv), the liquid C obtained in step (iii) is dried to obtain a dried product. Liquid C can be dried by known methods such as drum drying, flash drying, evaporation to dryness, and spray drying. The drying temperature is preferably 120 to 500°C, more preferably a lower limit of 140°C or higher and an upper limit of 350°C or lower. Drying is preferably carried out so that the moisture content of the resulting dried product is 0.1 to 4.5% by mass. These conditions can be selected as appropriate depending on the shape and size of the desired catalyst. Drying Liquid C can prevent adhesion of the dried product and improve yield.

[0051] The dried product obtained in step (iv) may be directly used for calcination in step (v), but molding is preferred because it improves catalytic performance. Molding may also be performed after step (v), which will be described later.

[0052] (Process (v)) In step (v), the dried product obtained in step (iv) is calcined to obtain a catalyst. Calcination can also be carried out after the molding step described below to obtain a molded product. In the present invention, the calcined and molded products are collectively referred to as catalysts. The calcination may be carried out only once, or may be carried out in multiple steps, including the molding step described below. For example, a primary calcination may be carried out first, the resulting primary calcined product may be subjected to the molding step described below, and the resulting molded product may be subjected to a secondary calcination. Alternatively, primary and secondary calcinations may be carried out, and the resulting catalyst may be subjected to the molding step. Alternatively, the molding step described below may be carried out first, and the resulting molded product may be calcined. Calcination can be carried out under a flow of an oxygen-containing gas such as air, an inert gas, or a reducing gas. "Inert gas" refers to a gas that does not reduce catalytic activity, and examples include nitrogen, carbon dioxide, helium, and argon. Examples of reducing gases include hydrogen, propylene gas, isobutylene gas, acrolein gas, and methacrolein gas. These may be used alone or in combination of two or more. By performing calcination under a flow of an oxygen-containing gas such as air, the COD and COD / S of the catalyst tend to decrease, while by performing calcination under a flow of an inert gas or a reducing gas, the COD and COD / S of the catalyst tend to increase.

[0053] The firing temperature is preferably 200 to 700° C. The lower limit of the firing temperature is more preferably 300° C. or higher, while the upper limit is more preferably 500° C. or lower, and even more preferably 450° C. or lower. The calcination time is preferably 0.5 to 40 hours, and the lower limit is more preferably 1 hour or more. Increasing the calcination temperature and lengthening the calcination time tends to increase COD / S, while decreasing the calcination temperature and shortening the calcination time tends to decrease COD / S. The calcination time refers to the time during which a predetermined calcination temperature is maintained after it is reached.

[0054] Among the above, the catalyst is used to convert an α,β-unsaturated alkene, alcohol, or ether into an α,β-unsaturated alkene. In the case of a catalyst used in producing aldehyde and / or α,β-unsaturated carboxylic acid, or a catalyst having a composition represented by the formula (1), it is preferable to perform a primary calcination on the dried product, followed by molding, and then perform a secondary calcination on the resulting molded product. In this case, the firing temperature for the primary firing is preferably 200 to 600°C, more preferably 250°C or higher and 450°C or lower. The firing time for the primary firing is preferably 0.5 to 5 hours from the viewpoint of improving the yield of the target product. The type and method of the firing furnace for the primary firing are not particularly limited. For example, a box-type firing furnace, a tunnel-type firing furnace, or the like may be used to fire the dried or shaped product in a fixed state. Alternatively, a rotary kiln or the like may be used to fire the dried or shaped product while it is flowing.

[0055] The firing temperature for the secondary firing is preferably 300 to 700°C, more preferably a lower limit of 400°C or higher and an upper limit of 600°C or lower. From the viewpoint of improving the yield of the target product, the firing time for the secondary firing is preferably 10 minutes to 10 hours, more preferably a lower limit of 1 hour or higher. The type and method of firing apparatus for the secondary firing are not particularly limited, and for example, a box-type firing furnace, a tunnel-type firing furnace, or the like may be used to fire the molded product or the primary fired product in a fixed state. Alternatively, a rotary kiln or the like may be used to fire the molded product or the primary fired product while it is flowing. Furthermore, when the catalyst is a catalyst used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde, or a catalyst having a composition represented by the formula (2), it is preferable to mold the dried product and then calcinate the molded product.

[0056] (molding process) In the molding step, the dried product obtained in step (iv) or the baked product obtained in step (v) is molded to obtain a molded product. The molding method is not particularly limited, and known dry or wet molding methods can be used. Examples include tableting, extrusion, pressure molding, and rolling granulation. During molding, conventionally known additives, for example, organic compounds such as polyvinyl alcohol and carboxymethyl cellulose, inorganic compounds such as graphite, talc, and diatomaceous earth, and inorganic fibers such as glass fiber, ceramic fiber, and carbon fiber may be added.

[0057] The shape of the molded product is not particularly limited, and examples include any shape such as a sphere, a cylinder, a ring, a star, or granules crushed and classified after molding. Among these, from the viewpoint of mechanical strength, a sphere, a columnar shape, and a ring shape are preferred. The size of the molded product is not particularly limited, but for example, in the case of a sphere, the diameter of the sphere is preferably 0.1 to 10 mm. The lower limit of the diameter of the sphere is more preferably 0.5 mm or more, even more preferably 1 mm or more, and particularly preferably 3 mm or more. Furthermore, the upper limit of the diameter of the sphere is more preferably 8 mm or less, even more preferably 6 mm or less. In the case of a ring or columnar shape, the diameter and height of the circle at the base of the ring or column are both preferably 0.1 to 10 mm. The lower limits of the diameter and height are more preferably 0.5 mm or more, even more preferably 1 mm or more, and particularly preferably 3 mm or more. Furthermore, the upper limits of the diameter and height are more preferably 8 mm or less, even more preferably 6 mm or less. In the case of other shapes, the length between the two most distant points in the solid of the catalyst is preferably 0.1 to 10 mm. The lower limit of the distance between the two points is more preferably 0.5 mm or more, even more preferably 1 mm or more, and particularly preferably 3 mm or more. The upper limit of the distance between the two points is more preferably 8 mm or less, even more preferably 6 mm or less. This improves the yield of the target product and the catalyst life.

[0058] The outer surface area of ​​the molded product is not particularly limited, but from the viewpoint of stable production of the target product over a long period of time, the lower limit is 0.01 cm 2 More than 0.05cm is preferable. 2 More than 0.1cm is preferable. 2 On the other hand, from the viewpoint of improving the yield of the target product, the upper limit is 4 cm 2 Less than 3cm is preferable 2 Less than 2cm is preferable 2 The following is even more preferred:

[0059] The volume of the molded product is not particularly limited, but it is preferable to select a volume that satisfies the requirements for stable production of the target product over a long period of time. Therefore, the lower limit is 0.0001 cm 3 More than 0.001cm is preferable. 3 More than 0.01cm is preferable. 3On the other hand, from the viewpoint of improving the yield of the target product, the upper limit is 5 cm 3 Less than 1cm is preferable 3 Less than 0.5cm is preferable 3 The following is even more preferred:

[0060] The mass of the molded product is not particularly limited, but from the viewpoint of stable production of the target product over a long period of time, the lower limit is preferably 0.002 g / piece or more, more preferably 0.01 g / piece or more, and even more preferably 0.05 g / piece or more, while from the viewpoint of improving the yield of the target product, the upper limit is preferably 0.5 g / piece or less, more preferably 0.3 g / piece or less, and even more preferably 0.2 g / piece or less.

[0061] The packed bulk density of the molded product is not particularly limited, but from the viewpoint of stably producing the target product over a long period of time, the lower limit is 0.2 g / cm. 3 More than 0.3 g / cm is preferable. 3 More preferably, 0.4 g / cm 3 On the other hand, from the viewpoint of improving the yield of the target product, the upper limit is 2 g / cm 3 Less than 1.5 g / cm is preferred 3 Less than 1.3 g / cm is more preferable. 3 More preferably, 0.8 g / cm 3 The following is particularly preferred: The packed bulk density of the molded product means the value calculated from the total mass of the molded product when the molded product is packed into a 100 ml measuring cylinder by a method in accordance with JIS-K 7365.

[0062] The obtained shaped product may be supported on a carrier. Examples of the carrier used for supporting include silica, alumina, silica-alumina, magnesia, titania, silicon carbide, etc. The shaped product may also be diluted with an inert substance such as silica, alumina, silica-alumina, magnesia, titania, silicon carbide, etc. In this manner, the catalyst can be produced.

[0063] [Method for producing α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid] In the method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid according to the present invention, the corresponding α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid is produced from an alkene, an alcohol, or an ether using the catalyst according to the present invention or a catalyst produced by the production method according to the present invention. In the method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid according to the present invention, it is preferable to use a catalyst having a composition represented by the formula (1), and it is also preferable to use a catalyst having a COD of more than 300 ppm and not more than 2000 ppm.

[0064] Examples of the alkene include propylene and isobutylene. Examples of the alcohol include t-butyl alcohol and isobutyl alcohol. Examples of the ether include methyl t-butyl ether. By oxidizing these raw organic compounds, the corresponding α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid can be produced. For example, when the raw organic compound is propylene, the corresponding α,β-unsaturated aldehyde is acrolein, and the corresponding α,β-unsaturated carboxylic acid is acrylic acid. When the raw organic compound is isobutylene, t-butyl alcohol, isobutyl alcohol, or methyl t-butyl ether, the corresponding α,β-unsaturated aldehyde is methacrolein, and the corresponding α,β-unsaturated carboxylic acid is methacrylic acid. From the viewpoint of the yield of the target product, the α,β-unsaturated aldehyde and the α,β-unsaturated carboxylic acid are preferably (meth)acrolein and (meth)acrylic acid, respectively, and more preferably methacrolein and methacrylic acid. It should be noted that "(meth)acrolein" refers to acrolein and methacrolein, and "(meth)acrylic acid" refers to acrylic acid and methacrylic acid.

[0065] The method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid according to the present invention The process can be carried out by contacting the catalyst according to the present invention or the catalyst produced by the production process according to the present invention with the raw material organic compound and a raw material gas containing oxygen in a reactor. The reactor is not particularly limited, but it is preferable to use a tubular reactor equipped with a reaction tube filled with a catalyst, and industrially it is particularly preferable to use a multi-tubular reactor equipped with a plurality of such reaction tubes. The catalyst layer in the reactor may be a single layer, or multiple catalysts with different activities may be packed in multiple layers. In addition, the catalyst may be diluted with an inert carrier and packed in order to control the activity.

[0066] The concentration of the raw material organic compound in the raw material gas is preferably 1 to 20% by volume, more preferably 3% by volume or more and 10% by volume or less. The raw material organic compound may contain small amounts of impurities such as lower saturated alkanes that do not substantially affect the reaction.

[0067] The oxygen concentration in the raw material gas is preferably 0.1 to 5 moles per mole of the raw material organic compound, with the lower limit being more preferably 0.5 moles or more and the upper limit being more preferably 3 moles or less. From an economical viewpoint, air is preferably used as the oxygen source for the raw material gas. If necessary, a gas enriched in oxygen by mixing pure oxygen with air or the like may be used.

[0068] From the viewpoint of economy, the raw material gas may be diluted with an inert gas such as nitrogen or carbon dioxide. Furthermore, water vapor may be added to the raw material gas. By carrying out the reaction in the presence of water vapor, an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1 to 50% by volume, with the lower limit being more preferably 1% by volume or more and the upper limit being 40% by volume or less.

[0069] The reaction pressure is preferably 0 to 1 MPa (G). Here, "(G)" is a gauge pressure, and 0 MPa (G) means that the reaction pressure is atmospheric pressure. The reaction temperature is preferably 200 to 450°C, with a lower limit of 250°C or higher and an upper limit of 400°C or lower. The contact time between the raw material gas and the catalyst is preferably 0.5 to 15 seconds. The lower limit of the contact time is more preferably 1 second or more, while the upper limit is more preferably 10 seconds or less, and even more preferably 5 seconds or less. By carrying out the production process as described above, an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid corresponding to the starting organic compound used can be obtained in high yield.

[0070] [Method of producing α,β-unsaturated carboxylic acid] In the method for producing an α,β-unsaturated carboxylic acid according to the present invention, a corresponding α,β-unsaturated carboxylic acid is produced from an α,β-unsaturated aldehyde using the catalyst according to the present invention or a catalyst produced by the production method according to the present invention. The α,β-unsaturated aldehyde may be produced by the method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid according to the present invention.

[0071] In the method for producing an α,β-unsaturated carboxylic acid according to the present invention, it is preferable to use a catalyst having a composition represented by the formula (2) above, and it is also preferable to use a catalyst having a COD of 2500 ppm or more and less than 11000 ppm.

[0072] When an α,β-unsaturated carboxylic acid is produced from an α,β-unsaturated aldehyde produced by the production method of the present invention, the catalyst of the present invention or a catalyst produced by the production method of the present invention may be used, or other known catalysts may be used. Examples of the α,β-unsaturated aldehyde include (meth)acrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein). The α,β-unsaturated carboxylic acid produced is an α,β-unsaturated carboxylic acid in which the aldehyde group of the α,β-unsaturated aldehyde is converted into a carboxyl group. Specifically, When the α,β-unsaturated aldehyde is (meth)acrolein, (meth)acrylic acid is obtained. From the viewpoint of the yield of the target product, the α,β-unsaturated aldehyde and the α,β-unsaturated carboxylic acid are preferably (meth)acrolein and (meth)acrylic acid, respectively, and more preferably methacrolein and methacrylic acid.

[0073] The method for producing an α,β-unsaturated carboxylic acid according to the present invention can be carried out by contacting the catalyst according to the present invention or a catalyst produced by the production method according to the present invention with a raw material gas containing an α,β-unsaturated aldehyde and oxygen in a reactor. The reactor may be the same as the reactor used in the above-mentioned method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid. The catalyst layer in the reactor may be a single layer, or multiple catalysts with different activities may be packed in multiple layers. Furthermore, the catalyst may be diluted with an inert carrier and packed to control the activity.

[0074] The concentration of the α,β-unsaturated aldehyde in the raw material gas is preferably 1 to 20% by volume, more preferably 3% by volume or more and 10% by volume or less. The α,β-unsaturated aldehyde may contain small amounts of impurities such as lower saturated aldehydes that do not substantially affect the reaction.

[0075] The oxygen concentration in the raw material gas is preferably 0.4 to 4 moles per mole of α,β-unsaturated aldehyde, with the lower limit being more preferably 0.5 moles or more and the upper limit being more preferably 3 moles or less. From an economical viewpoint, air is preferably used as the oxygen source for the raw material gas. If necessary, a gas enriched in oxygen by mixing pure oxygen with air or the like may be used.

[0076] From the viewpoint of economy, the raw material gas may be diluted with an inert gas such as nitrogen or carbon dioxide. Furthermore, water vapor may be added to the raw material gas. By carrying out the reaction in the presence of water vapor, an α,β-unsaturated carboxylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1 to 50% by volume, and more preferably the lower limit is 1% by volume or more and the upper limit is 40% by volume or less.

[0077] The reaction pressure is preferably 0 to 1 MPa (G), and the reaction temperature is preferably 200 to 450°C, more preferably with a lower limit of 250°C or higher and an upper limit of 400°C or lower. The contact time between the raw material gas and the catalyst is preferably 0.5 to 15 seconds. The lower limit of the contact time is more preferably 1 second or more, while the upper limit is more preferably 10 seconds or less, and even more preferably 5 seconds or less.

[0078] [Method of producing α,β-unsaturated carboxylic acid ester] In the method for producing an α,β-unsaturated carboxylic acid ester according to the present invention, the α,β-unsaturated carboxylic acid produced by the production method according to the present invention is esterified. The alcohol to be reacted with the α,β-unsaturated carboxylic acid is not particularly limited, and examples thereof include methanol, ethanol, propanol, isopropanol, butanol, and isobutanol. Examples of the α,β-unsaturated carboxylic acid ester obtained include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. The reaction can be carried out in the presence of an acidic catalyst such as a sulfonic acid-type cation exchange resin. The reaction temperature is preferably 50 to 200°C. [Example]

[0079] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" means parts by mass.

[0080] (Catalyst Composition) The molar ratio of each element in the catalyst was determined by dissolving the catalyst in aqueous ammonia and analyzing the components by ICP atomic emission spectrometry using an ICP Optima 8300 (Perkin Elmer) analyzer with an output of 1300 W, plasma gas flow rate of 10 L / min, auxiliary gas flow rate of 0.2 L / min, nebulizer gas flow rate of 0.55 L / min, and detector: segmented array CCD. The molar ratio of ammonium radicals was determined by analyzing the catalyst by the Kjeldahl method.

[0081] (COD of catalyst) The COD of the catalyst was measured by the following procedures (1) to (9). (1): Put 0.2±0.05 g of catalyst into an Erlenmeyer flask and weigh it accurately. The weight of the catalyst weighed at this point is m (g). (2): Add 100 mL of pure water to the Erlenmeyer flask (1). (3): In the Erlenmeyer flask (2), add 10 mL of a sulfuric acid solution prepared by mixing concentrated sulfuric acid and pure water in a volume ratio of concentrated sulfuric acid:pure water = 1:2, and 10 mL of a 5 mmol / L potassium permanganate solution. (4): Immerse the Erlenmeyer flask (3) in boiling water for 30 minutes. (5): The liquid in the Erlenmeyer flask obtained in (4) is filtered using a filter with a mesh size of 0.45 μm. (6): The filtrate obtained in (5) is immersed in boiling water for 5 minutes. (7): The filtrate obtained in (6) after immersion is placed in an Erlenmeyer flask, and 10 mL of a 12.5 mmol / L sodium oxalate aqueous solution is added. (8): The solution obtained in (7) is titrated with 5 mmol / L potassium permanganate solution until it turns a pale red color. The titration volume of the 5 mmol / L potassium permanganate solution is a (mL). (9) The COD of the catalyst is calculated using the above formula (3) from the precisely weighed weight m of the catalyst and the titration amount a of the 5 mmol / L potassium permanganate aqueous solution.

[0082] (specific surface area of ​​catalyst) The specific surface area S of the catalyst was measured for 1.0 g of catalyst using a nitrogen adsorption method (BET one-point method, equilibrium relative pressure = 0.30) with a mixed gas of 30% by volume of nitrogen and 70% by volume of helium as the measurement gas. The measurement was performed using a fully automatic specific surface area analyzer, Macsorb HM model-1200 (product name, manufactured by MOUNTECH).

[0083] (Reaction evaluation) The reaction evaluation of the catalysts in Examples 1 to 3 and Comparative Examples 1 and 2 was carried out using the production of methacrolein and methacrylic acid by oxidation of isobutylene as an example. The raw material gas and products in the reaction evaluation were analyzed using gas chromatography. The apparatus and columns used are shown below. Equipment: Shimadzu GC-2014 Column (methacrolein): QUADREX 007-CW-60W-3.0F (length 60 m, inner diameter 0.32 mm, film thickness 3.0 μm) Column (methacrylic acid): DB-FFAP manufactured by J&W (length 30 m, inner diameter 0.32 mm, film thickness 1.0 μm) From the results of gas chromatography, the total yield of methacrolein and methacrylic acid was calculated using the following formula. Total yield of methacrolein and methacrylic acid (%) = (P1 + P2) / F1 × 100 In the above formula, F1 is the number of moles of isobutylene supplied per unit time, P1 is the number of moles of methacrolein produced per unit time, and P2 is the number of moles of methacrylic acid produced per unit time.

[0084] The reaction evaluation of the catalysts in Examples 4 to 6 and Comparative Examples 3 to 6 was carried out using the production of methacrylic acid by oxidation of methacrolein as an example. The raw material gas and the product in the reaction evaluation were analyzed using gas chromatography similar to that described above. From the results of gas chromatography, the yield of methacrylic acid was calculated using the following formula. Methacrylic acid yield (%) = P2 / F2 × 100 In the above formula, F2 is the number of moles of methacrolein supplied per unit time, and P2 is the number of moles of methacrylic acid produced per unit time.

[0085] Example 1 Solution A1 was obtained by mixing 500 parts by weight of ammonium paramolybdate tetrahydrate, 12.3 parts by weight of ammonium paratungstate, 27.6 parts by weight of cesium nitrate, 38.5 parts by weight of bismuth (III) oxide, and 20.6 parts by weight of antimony trioxide with 2,000 parts by weight of pure water at 60 ° C. Separately from Solution A1, Solution A2 was obtained by mixing 200.2 parts by weight of iron (III) nitrate nonahydrate and 515.1 parts by weight of cobalt (II) nitrate hexahydrate with 1,000 parts by weight of pure water. Next, Solution A1 and Solution A2 were mixed to obtain Solution A.

[0086] The obtained solution A was heated to 95°C and stirred for 1 hour while maintaining the solution temperature at 95°C to obtain solution B. The obtained solution B was heated to 103°C and stirred for 7 hours while maintaining the solution temperature at 103°C to obtain solution C. The obtained solution C was dried in a spray dryer to obtain a dried product. The dried product was in a good dry state with no adhesion to the inner wall of the dryer. The composition of the dried product excluding oxygen was Mo 12 Bi 0.7 Fe 2.1 Co 7.5 W 0.2 Sb 0.6 Cs 0.6 (NH4) 10.5 It was. The dried product was subjected to primary calcination in an air atmosphere at 300°C for 1 hour. The calcined dried product was then pressure-molded and crushed to obtain crushed particles. The crushed particles were then subjected to secondary calcination in an air atmosphere at 500°C for 6 hours to obtain a catalyst. The COD and specific surface area S of the obtained catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 1.

[0087] The resulting catalyst was then packed into a reaction tube to form a catalyst layer, and an oxidation reaction of isobutylene was carried out under the following conditions. The results are shown in Table 1. Feed gas composition: 5% by volume of isobutylene, 12% by volume of oxygen, 10% by volume of water vapor, and 73% by volume of nitrogen Reaction temperature: 340℃ Contact time between raw gas and catalyst: 3 seconds

[0088] <Example 2> A dried product was obtained in the same manner as in Example 1. The dried product was in a good dry state with no adhesion to the inner wall surface of the dryer. The composition of the dried product excluding oxygen was Mo 12 Bi 0.7 Fe 2.1 Co 7.5 W 0.2 Sb 0.6 Cs 0.6 (NH4) 10.5 It was. The dried product was subjected to primary calcination in the same manner as in Example 1. The calcined dried product was then extruded to obtain a ring-shaped product with an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5.5 mm. The product was then subjected to secondary calcination at 500°C for 6 hours in an air atmosphere to obtain a catalyst. The COD and specific surface area S of the obtained catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 1. The obtained catalyst was then packed into a reaction tube to form a catalyst layer, and an oxidation reaction of isobutylene was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0089] Example 3 Solution B was obtained in the same manner as in Example 1. The obtained solution B was heated to 103°C and stirred for 3 hours while maintaining the solution temperature at 103°C to obtain solution C. The obtained solution C was dried in a spray dryer to obtain a dried product. The dried product was in a good dry state with no adhesion to the inner wall of the dryer. The composition of the dried product excluding oxygen was Mo 12 Bi 0.7 Fe 2.1 Co 7.5 W 0.2 Sb 0.6 Cs 0.6 (NH4) 10.5 It was.

[0090] The obtained dried product was subjected to primary calcination, molding and secondary calcination in the same manner as in Example 2 to obtain a catalyst. The COD and specific surface area S of the obtained catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 1. The obtained catalyst was then packed into a reaction tube to form a catalyst layer, and the oxidation reaction of isobutylene was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0091] <Comparative Example 1> Solution B was obtained in the same manner as in Example 1. The obtained solution B was dried in a spray dryer to obtain a dried product. That is, the step (iii) was not carried out, and the solution B was dried to obtain a dried product. The dried product was in a good dry state without adhering to the inner wall surface of the spray dryer. In addition, the composition of the dried product excluding oxygen was Mo 12 Bi 0.7 Fe 2.1 Co 7.5 W 0.2 Sb 0.6 Cs 0.6 (NH4) 10.5 It was. The obtained dried product was subjected to primary calcination, molding and secondary calcination in the same manner as in Example 1 to obtain a catalyst. The COD and specific surface area S of the obtained catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 1. The obtained catalyst was then packed into a reaction tube to form a catalyst layer, and the oxidation reaction of isobutylene was carried out in the same manner as in Example 1. The results are shown in Table 1. <Comparative Example 2> Solution A was obtained in the same manner as in Example 1. The obtained solution A was heated to 95°C and stirred for 2 hours while maintaining the solution temperature at 95°C to obtain solution B'. That is, solution B' was obtained by stirring for a time longer than 90 minutes in step (ii). The obtained solution B' was heated to 100°C and stirred for 1 hour while maintaining the solution temperature at 100°C to obtain solution C. The obtained solution C was evaporated to dryness to obtain a dried product. The composition of the dried product other than oxygen was Mo 12 Bi 0.7 Fe 2.1 Co 7.5 W 0.2 Sb 0.6 Cs 0.6 (NH4) 10.5 It was. The resulting dried product was subjected to primary calcination, molding and secondary calcination to obtain a catalyst. The COD and specific surface area S of the obtained catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 1. The obtained catalyst was then packed into a reaction tube to form a catalyst layer, and an oxidation reaction of isobutylene was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0092] [Table 1]

[0093] Example 4 A solution of 500 parts by weight of molybdenum trioxide, 17 parts by weight of ammonium metavanadate, and 47 parts by weight of an 85% by weight aqueous phosphoric acid solution diluted with 30 parts by weight of pure water was added to 2,000 parts by weight of pure water at 25°C. The resulting slurry was heated to 95°C with stirring, and stirred for 2 hours while maintaining the liquid temperature at 95°C to obtain Solution A3. Next, while maintaining the temperature at 95°C and stirring, a solution of 56 parts by weight of cesium bicarbonate dissolved in 100 parts by weight of pure water and a solution of 46 parts by weight of ammonium carbonate dissolved in 132 parts by weight of pure water were mixed to obtain Solution A. The obtained solution A was stirred for 20 minutes while being kept at 95°C to obtain solution B. The obtained solution B was heated to 98°C and stirred for 15 minutes while maintaining the solution temperature at 98°C to obtain solution C. The obtained solution C was dried in a spray dryer to obtain a dried product. The composition of the dried product excluding oxygen was P 1.4 Mo 12 V 0.5 Cu 0.15 Cs1(NH4) 3.3 It was.

[0094] The resulting dried product was extruded into a cylindrical shape with a diameter of 5.5 mm and a height of 5.5 mm, and calcined at 380°C for 10 hours in an air atmosphere to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid salt. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. The catalyst thus obtained was then packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out under the following conditions. The results are shown in Table 2. Feed gas composition: methacrolein 5% by volume, oxygen 10% by volume, water vapor 30% by volume, and nitrogen 55% by volume Reaction temperature: 300°C Contact time between raw gas and catalyst: 2 seconds

[0095] <Example 5> To 1,000 parts by weight of 25°C pure water as a solvent, 500 parts by weight of molybdenum trioxide, 20.5 parts by weight of ammonium metavanadate, 36.5 parts by weight of 85% by weight aqueous phosphoric acid solution, a solution of 7 parts by weight of copper (II) nitrate trihydrate in 61 parts by weight of pure water, and a solution of 6 parts by weight of iron (III) nitrate nonahydrate in 25 parts by weight of pure water were added. The resulting slurry was heated to 95°C with stirring, and stirred for 2 hours while maintaining the liquid temperature at 95°C to obtain Solution A3. Next, Solution A3 was cooled from 95°C to 50°C, and while maintaining the liquid temperature at 50°C and stirring, a solution of 73 parts by weight of cesium nitrate in 125 parts by weight of pure water and 199 parts by weight of 25% by weight aqueous ammonia were mixed to obtain Solution A. The obtained solution A was heated to 70°C and stirred for 20 minutes while maintaining the solution temperature at 70°C to obtain solution B. The obtained solution B was heated to 101°C and stirred for 2 hours while maintaining the solution temperature at 101°C to obtain solution C. The obtained solution C was dried in a drum dryer to obtain a dried product. The composition of the dried product excluding oxygen was P 1.1 Mo 12 V 0.6 Cu 0.1 Fe 0.05 Cs 1.3 (NH4) 10.7 in there were.

[0096] The resulting dried product was tableted into cylindrical shapes with a diameter of 5.5 mm and a height of 5.5 mm, and calcined at 380°C for 10 hours in an air atmosphere to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid salt. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0097] Example 6 A dried product was obtained in the same manner as in Example 5. The dried product was in a good dry state with no adhesion to the inner wall surface of the dryer. The composition of the dried product excluding oxygen was P 1.1 Mo 12 V 0.6 Cu 0.1 Fe 0.05 Cs 1.3 (NH4) 10.7 It was.

[0098] The dried product was tableted to form a cylindrical shape with a diameter of 5.5 mm and a height of 5.5 mm, and the resulting product was subjected to a primary calcination at 380°C for 10 hours in an air atmosphere, followed by a secondary calcination at 305°C for 2 hours in a methacrolein gas atmosphere to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid salt. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0099] <Comparative Example 3> Solution B was obtained in the same manner as in Example 4. The obtained solution B was dried in a spray dryer to obtain a dried product. That is, the step (iii) was not carried out, and the solution B was dried to obtain a dried product. The composition of the dried product excluding oxygen was P 1.4 Mo 12 V 0.5 Cu 0.15 Cs1(NH4) 3.3 It was.

[0100] The dried product was extruded to form a cylindrical shape with a diameter of 5.5 mm and a height of 5.5 mm, and the resulting product was subjected to a primary calcination at 380°C for 10 hours in an air atmosphere, followed by a secondary calcination at 301°C for 16 hours in a methacrolein gas atmosphere to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid salt. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0101] <Comparative Example 4> Phosphomolybdic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) was used as a dried reagent. The composition of the dried product, excluding oxygen, was P1Mo 12 It was. The dried product was subjected to pressure molding, and the resulting molded product was crushed and calcined in an air atmosphere at 300° C. for 5 hours to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0102] <Comparative Example 5> The reagent phosphovanadomolybdic acid (manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) was used as a dried material. The composition of the dried material, excluding oxygen, was P 1.1 Mo 12 V 1.1 It was. The dried product was molded and calcined in the same manner as in Comparative Example 3 to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0103] <Comparative Example 6> To 800 parts by mass of pure water at 25°C was added 16.9 parts by mass of molybdenum trioxide, 1.0 part by mass of vanadium pentoxide, and 1.2 parts by mass of an 85% by mass aqueous solution of phosphoric acid. The resulting slurry was heated to 85°C with stirring, and stirred for 3 hours while maintaining the liquid temperature at 85°C to obtain liquid A. The obtained solution A was heated to 90°C and stirred for 1 hour while maintaining the solution temperature at 90°C to obtain solution B. The obtained solution B was evaporated to dryness to obtain a dried product. That is, the step (iii) was not carried out, and the solution B was dried to obtain a dried product. The composition of the dried product excluding oxygen was P 1.1 Mo 12 V 1.1 It was.

[0104] The obtained dried product was molded and calcined in the same manner as in Comparative Example 4 to obtain a catalyst. The catalyst thus obtained contained a Keggin-type heteropolyacid. The COD and specific surface area S of the catalyst were measured. The calculated COD and COD / S values ​​are shown in Table 2. Next, the obtained catalyst was packed into a reaction tube to form a catalyst layer, and the oxidation reaction of methacrolein was carried out in the same manner as in Example 4. The results are shown in Table 2.

[0105] [Table 2]

[0106] As shown in Table 1, in Examples 1 to 3 in which the COD was within the specified range, the total yield of methacrolein and methacrylic acid was good. It should be noted that methacrylic acid can be obtained by oxidizing the methacrolein obtained in this example, and methacrylic acid esters can be obtained by esterifying the methacrylic acid.

[0107] Furthermore, as shown in Table 2, in Examples 4 to 6 in which the COD was within the specified range, the yield of methacrylic acid was good. The methacrylic acid obtained in this example can be esterified to obtain a methacrylic acid ester. [Industrial Applicability]

[0108] INDUSTRIAL APPLICABILITY The present invention can provide a catalyst that can produce target products such as α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids in high yields, and is therefore industrially useful.

Claims

1. A method for producing a catalyst containing at least molybdenum, comprising the following steps (i) to (v): (i) mixing at least a molybdenum raw material with a solvent to obtain a slurry (liquid A); (ii) stirring the solution A for 20 to 90 minutes at a temperature 1 to 30° C. lower than the boiling point of the solvent to obtain a slurry (solution B); (iii) a step of stirring the solution B for 10 minutes to 10 hours at a temperature that is at least 2°C higher than the temperature in the step (ii) to obtain a slurry (solution C); (iv) drying the solution C to obtain a dried product; (v) A step of calcining the dried product to obtain a catalyst.

2. 2. The method for producing a catalyst according to claim 1, wherein in the step (i), 50 mass % or more of the total solvent is water.

3. The method for producing a catalyst according to claim 1 or 2, wherein the temperature in the step (iii) is 1 to 20°C higher than the boiling point of the solvent.

4. The method for producing a catalyst according to any one of claims 1 to 3, wherein in the step (iii), the solution B is stirred for 90 minutes to 10 hours to obtain the solution C.

5. The method for producing a catalyst according to any one of claims 1 to 4, wherein in the step (v), the dried product is calcined under a flow of an oxygen-containing gas.

6. The method for producing the catalyst according to any one of claims 1 to 5, which produces a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether.

7. The method for producing a catalyst according to any one of claims 1 to 5, which is for producing a catalyst used in producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde.

8. A method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid from an alkene, an alcohol, or an ether using a catalyst produced by the production method according to any one of claims 1 to 6.

9. A method for producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde using a catalyst produced by the production method according to any one of claims 1 to 5 and 7.

10. A method for producing an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated carboxylic acid from an α,β-unsaturated aldehyde produced by the method according to claim 8.

11. A method for producing an α,β-unsaturated carboxylic acid ester, comprising producing an α,β-unsaturated carboxylic acid ester from the α,β-unsaturated carboxylic acid produced by the production method according to any one of claims 8 to 10.

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