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

Abstract

Provided is a simple method for producing a catalyst, the method being capable of producing α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid at high yield. This method, which is for producing a catalyst and used when α,β-unsaturated aldehyde and / or α,β-unsaturated carboxylic acid is produced by an oxidation reaction, comprises: (i) a step for dissolving or suspending, in a solvent, a raw material compound containing molybdenum to prepare solutions or slurries (A); (ii) a step for pressurizing the solutions or slurries (A) and colliding the pressurized solutions or slurries (A) with each other to prepare a solution or slurry (B); and (iii) a step for drying the solution or slurry (B) to obtain dried matter.

Description

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

[0001] The first invention of the present application relates to a method for producing a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid, and a method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid ester using the catalyst. The second invention of the present application relates to a catalyst used in producing an α,β-unsaturated carboxylic acid, a method for producing the catalyst, and a method for producing an α,β-unsaturated carboxylic acid and an α,β-unsaturated carboxylic acid ester using the catalyst.

[0002] Numerous proposals have been made so far regarding catalysts used in the production of α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids by vapor-phase catalytic oxidation of alkenes, alcohols, or ethers, catalysts used in the production of α,β-unsaturated carboxylic acids by vapor-phase catalytic oxidation of α,β-unsaturated aldehydes, and methods for producing these catalysts. The basic performance of such catalysts depends mainly on the elemental composition, crystalline structure, particle size, and the like, and controlling these factors requires controlling the conditions, particularly conditions such as pH and temperature, during the preparation process of an aqueous slurry containing a catalyst precursor.

[0003] Patent Document 1 describes a method for producing a catalyst for methacrylic acid production, which includes preparing a slurry (Liquid A) containing at least molybdenum, phosphorus, and an alkali metal and / or alkaline earth metal, and a solution or slurry (Liquid B) containing ammonia or ammonium radicals, and mixing Liquid A and Liquid B to prepare an AB mixed solution or mixed slurry (Liquid AB). Patent Document 2 describes the use of ammonium nitrate as an ammonium raw material in the production of a catalyst for methacrylic acid production. Using ammonium nitrate as an ammonium raw material allows the pH of a slurry containing a heteropolyacid (salt) to be kept low, resulting in the formation of a crystalline structure suitable for the production of α,β-unsaturated carboxylic acids (see Non-Patent Document 1). However, as described in Patent Document 3, when an organic molding aid is added in the catalyst molding process, the presence of ammonium nitrate can result in significant heat generation during calcination. Patent Document 4 proposes a method for producing a catalyst for producing methacrylic acid having high reaction activity and selectivity by controlling the mixing state of a catalyst raw material solution using a high-speed rotary shear agitator such as a homogenizer and further performing a heat aging treatment.

[0004] On the other hand, heteropolyacid catalysts such as phosphomolybdic acid are known as catalysts for producing α,β-unsaturated carboxylic acids, which are used when producing α,β-unsaturated carboxylic acids by oxidizing α,β-unsaturated aldehydes. Numerous methods for producing heteropolyacid catalysts have been proposed. Patent Document 5 describes a method for producing a catalyst for producing methacrylic acid, which contains at least molybdenum and phosphorus as catalytic components and is used when producing methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen.

[0005] In the production of α,β-unsaturated carboxylic acids, catalysts are generally formed into spherical bodies with a diameter of approximately 2 to 20 mm, or cylindrical or columnar bodies with a diameter of approximately 2 to 10 mm and a length of approximately 2 to 20 mm. These molded catalyst bodies are then packed into reactors for use. Because the performance of molded catalyst bodies varies depending on the pore structure, many studies have been conducted to control the pore structure of molded catalyst bodies. Patent Document 6 describes a catalyst used to produce methacrylic acid, having a pore volume of 0.10 to 1.0 cc / g and a pore size distribution in which the pore diameters are concentrated in the ranges of 1 to 10 μm and 0.1 to less than 1 μm, respectively. Patent Document 7 describes a catalyst for producing methacrylic acid, which has at least two peaks in the pore radius range of 0.5 to 10 μm in a pore size distribution chart. Patent Document 8 also discloses a method for producing a catalyst containing at least molybdenum and phosphorus as catalytic components, which is used in the production of methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen. According to this production method, when the ratio of the apparent density of the dried product to the density of the molded product is within a specific range, it is possible to ensure both the amount of pores effective for the selective oxidation of methacrolein and the amount of catalyst loaded effective for the oxidation of methacrolein, thereby improving the yield of methacrylic acid.

[0006] Japanese Patent Application Laid-Open No. 2008-681 Japanese Patent Application Laid-Open No. 2014-226614 Japanese Patent Application Laid-Open No. 6-86933 Japanese Patent Application Laid-Open No. 7-185354 Japanese Patent Application Laid-Open No. 2011-224482 Japanese Patent Application Laid-Open No. 63-315148 Japanese Patent Application Laid-Open No. 2000-84412 International Publication No. 2012 / 141076

[0007] T. OKUHARA, N. MIZUNO, M. MISONO, ADVANCES IN CATALYSIS, 1996, Volume 41, pp. 113-252

[0008] From an industrial viewpoint, there is a need for the development of a method for producing a catalyst that can more simply and easily further increase the yield of the target product. An object of the first invention of the present application is to provide a simple method for producing a catalyst that can produce an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid in high yield. Another object of the first invention of the present application is to provide a method for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid ester in high yield using a catalyst obtained by such a production method.

[0009] Furthermore, conventional catalysts for producing α,β-unsaturated carboxylic acids lack sufficient mechanical strength, and cracks and chips may occur when the catalyst is packed into a reaction tube during the production of α,β-unsaturated carboxylic acids. As a result, the gas flow in the reaction tube becomes uneven, which can cause hot spots and adversely affect the catalyst performance and lifespan. The second invention of the present application aims to provide a catalyst that suppresses cracks and chips during catalyst packing and that can produce α,β-unsaturated carboxylic acids in high yields. The second invention of the present application also aims to provide a method for producing such a catalyst for producing α,β-unsaturated carboxylic acids, and a method for producing α,β-unsaturated carboxylic acids and α,β-unsaturated carboxylic acid esters in high yields using the catalyst.

[0010] The present inventors conducted extensive research in view of the problems associated with the first invention. As a result, they discovered that the problems can be solved by using a catalyst produced by pressurizing catalyst precursor slurries, causing them to collide with each other, and drying the resulting mixture, thereby completing the first invention. Furthermore, the present inventors conducted extensive research in view of the problems associated with the second invention. As a result, they discovered that the problems can be solved by controlling the catalyst physical properties so that the ratio (S / V) of the area-based median diameter (S) to the volume-based median diameter (V) falls within a specific range in a pore distribution curve, thereby completing the second invention. That is, the first and second inventions include the following features.

[0011] [1] A method for producing a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid by an oxidation reaction, the method comprising the following steps (i) to (iii): (i) dissolving or suspending a raw material compound containing molybdenum in a solvent to prepare a solution or slurry (A); (ii) pressurizing the solution or slurry (A) and causing particles of the pressurized solution or slurry (A) to collide with each other to prepare a solution or slurry (B); and (iii) drying the solution or slurry (B) to obtain a dried product. [2] The method for producing the catalyst according to [1], wherein in the step (ii), the pressurized solution or slurry (A) is sprayed from two or more nozzles to cause particles of the solution or slurry (A) to collide with each other. [3] The method for producing the catalyst according to [1] or [2], wherein in the step (ii), particles contained in the pressurized solution or slurry (A) are caused to collide with each other obliquely. [4] A method for producing a catalyst according to any one of [1] to [3], wherein in the step (ii), the solution or slurry (A) is pressurized to 50 MPa or more. [5] A method for producing a catalyst according to any one of [1] to [4], wherein the average particle size of particles contained in the solution or slurry (A) obtained in the step (i) is 1.0 μm or more. [6] A method for producing a catalyst according to any one of [1] to [5], wherein the average particle size of particles contained in the solution or slurry (B) obtained in the step (ii) is 0.5 μm or less. [7] A method for producing a catalyst according to any one of [1] to [6], wherein the catalyst is a catalyst used in producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid by an oxidation reaction of an alkene, an alcohol, or an ether. [8] A method for producing a catalyst according to [7], wherein the catalyst has a composition represented by the following formula (I): Mo ａ１ Bi ｂ１ Fe ｃ１ A ｄ１ E ｅ１ G ｆ１ J ｇ１ Si ｈ１ (NH ４ ) ｉ１ O ｊ１ (I) In formula (I), Mo, Bi, Fe, Si, NH ４, and O represent molybdenum, bismuth, iron, silicon, ammonium, and oxygen, respectively; A represents at least one element selected from the group consisting of cobalt and nickel; E represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, thallium, tantalum, and zinc; G represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. J represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, a1 to j1 represent the molar ratio of each component, and when a1 = 12, b1 = 0.01 to 3, c1 = 0.01 to 5, d1 = 0.01 to 12, e1 = 0 to 8, f1 = 0 to 5, g1 = 0.001 to 2, h1 = 0 to 20, and i1 = 0 to 30, and j1 represents the molar ratio of oxygen necessary to satisfy the valence of each component. [9] A method for producing a catalyst according to any one of [1] to [6], wherein the catalyst is a catalyst used in producing an α,β-unsaturated carboxylic acid by an oxidation reaction of an α,β-unsaturated aldehyde.

[10] A method for producing a catalyst according to [9], wherein the catalyst has a composition represented by the following formula (II): P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ X ｅ２ Y ｆ２ Z ｇ２ (NH ４ ) ｈ２ O ｉ２ (II) In formula (II), P, Mo, V, Cu, NH ４, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; X represents at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony, and bismuth; Y represents at least one element selected from the group consisting of niobium, tantalum, tungsten, cerium, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, and lanthanum; Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; a2 to 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 = 0.01 to 3, and h2 = 0.01 to 30; and i2 is the molar ratio of oxygen necessary to satisfy the valence of each component.

[11] The method for producing a catalyst according to

[10] , wherein in the step (i), the solution or slurry (A) is prepared by mixing a raw material liquid (A1) containing phosphorus and molybdenum with a raw material compound (A2) containing the Z element in formula (II).

[12] The method for producing a catalyst according to

[11] , wherein in the step (i), the temperature of the raw material liquid (A1) to be mixed with the raw material compound (A2) containing the Z element in formula (II) is 30° C. or higher.

[0012]

[13] A catalyst used in producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde, wherein the ratio (S / V) of the area-based median diameter (S) to the volume-based median diameter (V) in a pore distribution curve is 0.01 or more and 0.21 or less.

[14] The catalyst according to

[13] , wherein the area-based median diameter (S) is 0.25 μm or less.

[15] The catalyst according to

[13] or

[14] , wherein the volume-based median diameter (V) is 1.20 μm or more.

[16] The catalyst according to any one of

[13] to

[15] , wherein the catalyst contains phosphorus, molybdenum, and vanadium.

[17] The catalyst according to any one of

[13] to

[16] , wherein the catalyst has a composition represented by the following formula (II): P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ Xｅ２ Y ｆ２ Z ｇ２ (NH ４ ) ｈ２ O ｉ２ (II) In formula (II), P, Mo, V, Cu, NH ４ , and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; X represents at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony, and bismuth; Y represents at least one element selected from the group consisting of niobium, tantalum, tungsten, cerium, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, and lanthanum; Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; a2 to 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 = 0.01 to 3, and h2 = 0.01 to 30; and i2 is the molar ratio of oxygen necessary to satisfy the valence of each component.

[18] A method for producing the catalyst according to any one of

[13] to

[17] , comprising: a step of preparing a solution or slurry (A) containing a heteropolyacid salt having a Keggin structure; and a step of pressurizing the solution or slurry (A) and causing the pressurized solutions or slurries (A) to collide with each other to prepare a solution or slurry (B).

[0013]

[19] A method for producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid by oxidation of an alkene, an alcohol, or an ether in the presence of a catalyst produced by the method described in any one of [1] to [8].

[20] A method for producing an α,β-unsaturated carboxylic acid, comprising producing an α,β-unsaturated aldehyde by oxidation in the presence of a catalyst produced by the method described in any one of [1] to [6] and [9] to

[12] , the catalyst described in any one of

[13] to

[17] , or the catalyst produced by the method described in

[18] .

[21] A method for producing an α,β-unsaturated carboxylic acid ester, comprising esterifying the α,β-unsaturated carboxylic acid produced by the method described in

[19] .

[22] A method for producing an α,β-unsaturated carboxylic acid ester, comprising esterifying the α,β-unsaturated carboxylic acid produced by the method described in

[20] .

[0014] According to the first invention of the present application, it is possible to provide a simple method for producing a catalyst capable of producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid in high yield. Furthermore, according to the first invention, it is possible to produce an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid, and an α,β-unsaturated carboxylic acid ester in high yield using the catalyst obtained by such a production method.

[0015] According to the second invention of the present application, it is possible to provide a catalyst that can suppress cracking or chipping during catalyst packing and can produce an α,β-unsaturated carboxylic acid in high yield, and a method for producing the same. Furthermore, according to the second invention, it is possible to produce an α,β-unsaturated carboxylic acid and an α,β-unsaturated carboxylic acid ester in high yield using the catalyst.

[0016] Hereinafter, embodiments of the first and second inventions of the present application (hereinafter collectively referred to as "the present invention") will be described in detail. The following description of the constituent elements is an example of an embodiment of the present invention, and the present invention is not limited to these details. Furthermore, the expressions "XX or more and YY or less" and "XX to YY" representing a numerical range mean 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 and the numerical values ​​described in the examples can be arbitrarily combined to form a new numerical range.

[0017] <First Invention> <Method for Producing Catalyst> A method for producing a catalyst according to a first invention (hereinafter also referred to as "the present invention") is a method for producing a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid by an oxidation reaction.

[0018] [Catalyst] The catalyst obtained by the catalyst production method according to the present invention is used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid by an oxidation reaction. Specifically, the catalyst is preferably a catalyst used in producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid by an oxidation reaction of an alkene, an alcohol, or an ether, or in producing an α,β-unsaturated carboxylic acid by an oxidation reaction of an α,β-unsaturated aldehyde. Note that "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.

[0019] From the viewpoint of the yield of the target product, the catalyst preferably contains a catalyst having a composition represented by formula (I) or (II) below, and more preferably has a composition represented by formula (I) or (II) below. When the catalyst is used in producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid by the oxidation reaction of an alkene, an alcohol, or an ether, the catalyst containing a catalyst having a composition represented by formula (I) below allows the production of an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid in a higher yield. Furthermore, when the catalyst is used in producing an α,β-unsaturated carboxylic acid by the oxidation reaction of an α,β-unsaturated aldehyde, the catalyst containing a catalyst having a composition represented by formula (II) below allows the production of an α,β-unsaturated carboxylic acid in a higher yield. Note that the catalyst may contain small amounts of elements not represented by formula (I) or formula (II) below. Furthermore, when the catalyst is formed using a support, the catalyst is meant to include the support, and the composition represented by formula (I) or formula (II) below is a composition that takes the support into consideration.

[0020] Mo ａ１ Bi ｂ１ Fe ｃ１ A ｄ１ E ｅ１ G ｆ１ J ｇ１ Si ｈ１ (NH ４ ) ｉ１ O ｊ１ (I) In formula (I), Mo, Bi, Fe, Si, NH ４, and O represent molybdenum, bismuth, iron, silicon, ammonium, and oxygen, respectively. A represents at least one element selected from the group consisting of cobalt and nickel. E represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, thallium, tantalum, and zinc. G represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. J represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. a1 to j1 indicate the molar ratio of each component, and when a1 = 12, b1 = 0.01 to 3, c1 = 0.01 to 5, d1 = 0.01 to 12, e1 = 0 to 8, f1 = 0 to 5, g1 = 0.001 to 2, h1 = 0 to 20, and i1 = 0 to 30, and j1 is the molar ratio of oxygen necessary to satisfy the valence of each component.

[0021] P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ X ｅ２ Y ｆ２ Z ｇ２ (NH ４ ) ｈ２ O ｉ２ (II) In formula (II), P, Mo, V, Cu, NH ４, and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively. X represents at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony, and bismuth. Y represents at least one element selected from the group consisting of niobium, tantalum, tungsten, cerium, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, and lanthanum. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. a2 to i2 indicate the molar ratio 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 = 0.01 to 3, and h2 = 0.01 to 30, and i2 is the molar ratio of oxygen necessary to satisfy the valence of each component.

[0022] The molar ratio of each element in the above formula (I) and formula (II) is a value determined by analyzing a solution in which the catalyst is dissolved in ammonia water by ICP emission spectrometry. The molar ratio of ammonium radical is a value determined by analyzing the catalyst by Kjeldahl method. In the present invention, "ammonium radical" refers to ammonium ion (NH ４ ＋ ) which can be converted to ammonia (NH ３ ) and ammonium contained in ammonium-containing compounds such as ammonium salts.

[0023] [Method for Producing Catalyst] The method for producing a catalyst according to the present invention comprises at least the following steps (i) to (iii): (i) a step of dissolving or suspending a raw material compound containing at least molybdenum in a solvent to prepare a solution or slurry (A); (ii) a step of pressurizing the solution or slurry (A) and causing the pressurized solutions or slurries (A) to collide with each other to prepare a solution or slurry (B); and (iii) a step of drying the solution or slurry (B) to obtain a dried product. Each step will be described below.

[0024] (Step (i)) In step (i), a raw material compound containing at least molybdenum is dissolved or suspended in a solvent to prepare a solution or slurry (A). The method for preparing the solution or slurry (A) is not particularly limited, and the solution or slurry (A) can be prepared by, for example, a precipitation method or an oxide mixing method. The amount of the raw material compound used is preferably adjusted so that the resulting catalyst has a composition represented by formula (I) or formula (II).

[0025] The type of raw material compound is not particularly limited, and one selected from the group consisting of oxides, sulfates, nitrates, carbonates, hydroxides, and organic acid salts such as acetates of each constituent element contained in the catalyst, ammonium salts, halides, oxoacids, oxoacid salts, and alkali metal salts can be used alone or in combination of two or more. Examples of molybdenum raw material compounds include molybdenum oxides such as molybdenum trioxide, ammonium molybdates such as ammonium paramolybdate and ammonium dimolybdate, molybdic acid, and molybdenum chloride. Examples of bismuth raw material compounds include bismuth nitrate, bismuth oxide, bismuth acetate, and bismuth hydroxide. Examples of iron raw material compounds include iron nitrate, iron hydroxide, and iron oxide. Examples of silicon raw material compounds include silica, granular silica, colloidal silica, and fumed silica. Examples of phosphorus raw material compounds include phosphoric acid, phosphorus pentoxide, and phosphates such as ammonium phosphate. Examples of vanadium raw material compounds include ammonium vanadate, ammonium metavanadate, vanadium pentoxide, vanadium chloride, and vanadyl oxalate. Examples of copper raw material compounds include copper sulfate, copper nitrate, copper oxide, copper carbonate, copper acetate, and copper chloride. Examples of cesium raw material compounds include cesium nitrate, cesium sulfate, cesium chloride, cesium carbonate, cesium bicarbonate, and cesium acetate. Examples of ammonium radical raw material compounds include ammonium bicarbonate, ammonium carbonate, ammonium nitrate, and aqueous ammonia.

[0026] Examples of the solvent include water, ethanol, and acetone. These may be used alone or in combination of two or more. Among these, it is preferable to use water as the solvent.

[0027] When the catalyst contains a catalyst having a composition represented by formula (II), step (i) preferably includes the following steps (i-1) and (i-2): (i-1) a step of dissolving or suspending a raw material compound containing at least phosphorus and molybdenum in a solvent to prepare a raw material liquid (A1); and (i-2) a step of mixing the raw material liquid (A1) with a raw material compound (A2) containing the Z element in formula (II) to prepare the solution or slurry (A). Each step will be described below.

[0028] <Step (i-1)> In step (i-1), a raw material compound containing at least phosphorus and molybdenum is dissolved or suspended in a solvent to prepare a raw material solution (A1) containing at least phosphorus and molybdenum. In this step, a raw material compound containing vanadium and a raw material compound containing copper may be further added. The raw material compound containing vanadium and the raw material compound containing copper may be added in the form of a raw material solution in which they are added to a solvent. The pH of the raw material solution (A1) is preferably 0.3 to 5.5. The lower limit of the pH of the raw material solution (A1) is more preferably 0.5, and the upper limit is more preferably 4.5. The pH of the raw material solution (A1) can be adjusted by appropriately selecting the type and amount of the raw material compound used and adding nitric acid, oxalic acid, aqueous ammonia, or the like as needed. The pH can be measured using a pH meter. For example, a D-21 (trade name, manufactured by HORIBA, Ltd.) can be used as the pH meter.

[0029] The raw material liquid (A1) is preferably prepared by heating to 80°C to 130°C. By heating the raw material liquid (A1) to 80°C or higher, the dissolution rate of the raw material compounds can be sufficiently increased. Furthermore, by heating the raw material liquid (A1) to 130°C or lower, evaporation of the solvent can be suppressed. The heating temperature of the raw material liquid (A1) is more preferably 90°C or higher.

[0030] <Step (i-2)> In step (i-2), the raw material liquid (A1) obtained in step (i-1) is mixed with a raw material compound (A2) containing the Z element in formula (II) to prepare a solution or slurry (A). In this step, a raw material compound of an ammonium radical may be further mixed. The raw material compound (A2) containing the Z element and the raw material compound of an ammonium radical may be mixed with the raw material liquid (A1) in the form of a raw material liquid in which they are added to a solvent.

[0031] When the raw material liquid (A1) and the raw material compound (A2) containing the Z element are mixed, the temperature of the raw material liquid (A1) is preferably 30°C or higher, for example, 30°C to 99°C. This makes it possible to suppress local heat generation in the catalyst when the target product is produced using the obtained catalyst. The temperature of the raw material liquid (A1) is more preferably 40°C or higher and more preferably 95°C or lower.

[0032] (Solution or Slurry (A)) When the catalyst contains a catalyst having a composition represented by formula (II), the solution or slurry (A) contains a heteropolyacid salt. The heteropolyacid salt preferably has a Keggin structure. That is, when the catalyst contains a catalyst having a composition represented by formula (II), step (i) is preferably a step of dissolving or suspending a raw material compound containing at least phosphorus and molybdenum in a solvent to prepare a solution or slurry (A) containing a heteropolyacid salt having a Keggin structure. When the solution or slurry (A) contains a heteropolyacid salt having a Keggin structure, the particles contained in the solution or slurry (A) are less likely to change and can exist stably. As a result, a catalyst capable of producing the target product in a high yield is obtained. The presence of a heteropolyacid salt having a Keggin structure in the solution or slurry (A) can be confirmed by measuring the infrared absorption spectrum of a dried product obtained by drying the solution or slurry (A) using infrared spectroscopy. When the solution or slurry (A) contains a heteropolyacid salt having a Keggin structure, the resulting infrared absorption spectrum has a peak at 1065 cm －１ , 965 cm －１ , 870 cm －１ , and 790 cm －１There is a characteristic peak around

[0033] By adjusting the pH of the solution or slurry (A) to 4 or less, a solution or slurry (A) containing a heteropolyacid salt having a Keggin structure can be easily obtained. An example of a method for adjusting the pH of the solution or slurry (A) to 4 or less is to use molybdenum trioxide as a molybdenum raw material when preparing the raw material liquid (A1). Another example is to appropriately select raw material compounds and adjust the content of nitrate ions and oxalate ions to previously control the pH of the raw material liquid (A1) to a low level. From the viewpoint of stably forming a heteropolyacid salt having a Keggin structure, the pH of the solution or slurry (A) is more preferably 1 to 3, and even more preferably 1 to 2.5.

[0034] The average particle size of the particles contained in the solution or slurry (A) is preferably 1.0 μm or more. This can further suppress a decrease in the specific surface area and catalytic activity of the resulting catalyst, thereby further improving the selectivity of the target product in a reaction using the catalyst. There is no particular upper limit to the average particle size of the particles contained in the solution or slurry (A). In this specification, the term "average particle size" refers to the average diameter calculated from the arithmetic mean in a volume-based particle size distribution measured by a laser diffraction particle size distribution measurement method. There are no particular limitations on the method for achieving an average particle size of 1.0 μm or more in the solution or slurry (A). For example, when preparing the solution or slurry (A) by mixing the raw material liquid (A1) and the raw material compound (A2), stirring is performed for 0.5 to 1 hour using a rotary blade stirrer at a rotation speed of 50 to 200 rpm. The above stirring conditions are merely examples, and the stirring speed and stirring time can be adjusted as appropriate.

[0035] When producing a catalyst containing a catalyst having the composition represented by formula (II), the solution or slurry (A) preferably contains a compound having the composition represented by formula (II), which facilitates the adjustment of the average particle size in the step (ii) described below.

[0036] (Step (ii)) In step (ii), the solution or slurry (A) obtained in step (i) is pressurized, and the pressurized solutions or slurries (A) are caused to collide with each other to prepare a solution or slurry (B). Step (ii) is preferably carried out at a temperature within a range in which the solvent does not boil or the volume of the solvent does not change significantly, and can be carried out, for example, at 10°C to 50°C. Specific examples of a method for pressurizing and colliding the solution or slurry (A) include the following methods. The solution or slurry (A) is sprayed under pressure from two or more nozzles, for example, a pair of nozzles, and the resulting jets are caused to collide with each other. The shear force applied during this spraying and the collision energy during collision reduce the average particle size of the particles contained in the solution or slurry (A). As a result, a solution or slurry (B) is obtained that contains particles having an average particle size smaller than that of the particles contained in the solution or slurry (A). The average particle size of the particles contained in the solution or slurry (B) is preferably 0.5 μm or less, and more preferably 0.4 μm or less. By preparing such a solution or slurry (B), a catalyst capable of producing the target product in a higher yield can be obtained.

[0037] In the catalyst production method described in Patent Document 4, a catalyst raw material slurry is prepared at 40°C, and then the resulting catalyst raw material slurry is stirred and mixed at high speed using a high-speed rotary shear mixer such as a homogenizer while being heated at 100°C to 200°C for at least one hour. In other words, the method described in Patent Document 4 is an atomization treatment that uses chemical changes, in which fine particles are precipitated through a process of particle dissolution and reprecipitation by stirring the catalyst raw material slurry at high speed while heating it. On the other hand, the catalyst production method according to the present invention controls the average particle size of particles contained in the slurry solely by physical forces such as shear, collision, and cavitation, without using chemical changes.

[0038] As described above, according to the present invention, by physically controlling the average particle size of particles contained in the slurry, a catalyst capable of producing a target product with a high yield can be obtained. The reasons for this can be considered as follows. First, as described above, if the average particle size of particles contained in the solution or slurry (A) is preferably 1.0 μm or more, the selectivity of the target product in a reaction using the obtained catalyst is further improved. On the other hand, if the average particle size is too large, the specific surface area of ​​the obtained catalyst decreases, resulting in a decrease in catalytic activity. Since the yield of the target product is affected by both the catalytic activity and the selectivity of the target product, a catalyst produced using the solution or slurry (A) as is cannot achieve a sufficient yield of the target product. Therefore, in the present invention, first, a solution or slurry (A) containing particles having an average particle size of preferably 1.0 μm or more is prepared, and then, by performing an atomization treatment using a physical force as described above, the average particle size of the particles contained in the solution or slurry (A) is reduced to prepare a solution or slurry (B) containing particles having an average particle size of preferably 0.5 μm or less. By using this solution or slurry (B), it is possible to obtain a catalyst that is excellent in both catalytic activity and selectivity for the target product, and that is capable of producing the target product in a high yield.

[0039] In this step, the solution or slurry (A) is preferably pressurized to 50 MPa or more, more preferably 100 MPa or more. The upper limit of the pressure is, for example, 245 MPa. Even when treatment is performed at a pressure exceeding 245 MPa, the catalytic performance does not change. However, when performing atomization treatment using a general device, it is difficult to achieve a pressure exceeding 245 MPa. Furthermore, when the pressurized solutions or slurries (A) are caused to collide with each other, they may be caused to collide in a straight line or obliquely. However, from the viewpoint of ease of particle size reduction, it is preferable to cause the particles contained in the solution or slurry (A) to collide with each other obliquely. The number of times the solution or slurry (A) is caused to collide is not particularly limited, but is preferably 1 to 10 times, more preferably 1 to 5 times. If the number of collisions is 10 times or less, a decrease in productivity can be suppressed. Furthermore, the effect of frictional heat on the catalyst properties can be suppressed. An example of the atomization device used in this step is a wet atomization device STAR BURST (product name, model: HJP-25005V2, manufactured by Sugino Machine Ltd.). However, the atomization device is not limited as long as it is a device that can pressurize the solution or slurry (A) and spray it, thereby causing the pressurized solution or slurry (A) to collide with each other.

[0040] (Step (iii)) In step (iii), the solution or slurry (B) obtained in step (ii) is dried to obtain a dried product. As the drying method, known methods such as drum drying, flash drying, evaporation to dryness, and spray drying can be applied. Among these, the spray drying method using a spray dryer is preferred because particles are obtained simultaneously with drying and particles with a regular spherical shape are obtained. The drying conditions vary depending on the drying method, but when a spray dryer is used, the dryer inlet temperature is preferably 200°C to 400°C, with a lower limit of 220°C and an upper limit of 370°C. In addition, the contact method between the sprayed droplets and the hot air may be any of parallel flow, counterflow, and parallel counterflow (mixed flow), and drying can be performed suitably in any case.

[0041] The dried product obtained in step (iii) exhibits catalytic performance and can be used as a catalyst for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid. Furthermore, by subjecting the dried product to molding and calcination, as described below, the catalytic performance is further improved, which is preferable. In the present invention, the term "catalyst" collectively refers to the dried product obtained in step (iii) as well as the product obtained by molding and / or calcining the dried product.

[0042] (Shaping Step) In the shaping step, the dried product obtained in step (iii) is shaped as needed to obtain a molded product (catalyst molded product). The shaping step may be performed after the calcination step described below. There are no particular limitations on the shaping method, and known dry and wet shaping methods can be applied. Examples of the shaping method include tableting, press molding, extrusion molding, and granulation molding. The shape of the molded product is also not particularly limited, and examples include cylindrical, ring-shaped, and spherical shapes. The shaping step can be performed, for example, by mixing and kneading the dried product with, if necessary, a solvent and a carrier (shaping aid). Examples of the solvent include the same solvents as those used in preparing the solution or slurry (A). Examples of the shaping aid include known shaping aids such as organic binders such as hydroxypropyl cellulose, graphite, or talc.

[0043] (Caustic step) From the viewpoint of the yield of the target product, it is preferable to calcinate the dried product obtained in step (iii) or the molded body obtained in the molding step. The calcination can be carried out by heat treatment under the flow of at least one of an oxygen-containing gas such as air and an inert gas, but it is preferable to carry out the heat treatment under the flow of an oxygen-containing gas. Here, the inert gas refers to a gas that does not reduce the catalytic activity, and specific examples include nitrogen, carbon dioxide, helium, and argon. These inert gases may be used alone or in combination of two or more.

[0044] The shape of the heat treatment vessel used for firing is not particularly limited, but a box-shaped or tubular heat treatment vessel can be used. Alternatively, the object may be divided into multiple vessels and filled therein for heat treatment. The cross-sectional area of ​​each heat treatment vessel should be 1 cm or less. ２ ~10,000 cm ２ The heat treatment temperature (maximum temperature during heat treatment) is preferably 200°C to 700°C, with the lower limit more preferably 320°C and the upper limit more preferably 450°C. The heat treatment time is appropriately set depending on the target catalyst, but is preferably 0.5 hours to 40 hours, and more preferably 1 hour to 40 hours. In this manner, a catalyst for producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid can be produced.

[0045] According to the first aspect of the present invention, the specific surface area of ​​the catalyst obtained can be increased by performing the atomization treatment at the solution or slurry stage. From the viewpoint of obtaining a highly active catalyst, the BET specific surface area of ​​the catalyst (after calcination) is set to, for example, 6.0 m ２ / g to 7.0m ２ The BET specific surface area of ​​the catalyst can be calculated by the BET single-point method using nitrogen adsorption.

[0046] <Method for producing α,β-unsaturated aldehyde and α,β-unsaturated carboxylic acid> In the method for producing α,β-unsaturated aldehyde and α,β-unsaturated carboxylic acid according to the first aspect of the present invention, an oxidation reaction of an alkene, alcohol, or ether is carried out in the presence of a catalyst produced by the method for producing a catalyst according to the first aspect of the present invention, thereby making it possible to produce α,β-unsaturated aldehyde and α,β-unsaturated carboxylic acid in high yield.

[0047] Examples of alkenes include propylene and isobutylene, examples of alcohols include primary butyl alcohol and tertiary butyl alcohol, and examples of ethers include methyl tertiary butyl ether.

[0048] The resulting α,β-unsaturated aldehyde and α,β-unsaturated carboxylic acid correspond to the alkene, alcohol, or ether, respectively. For example, the α,β-unsaturated aldehyde corresponding to propylene is acrolein, and the corresponding α,β-unsaturated carboxylic acid is acrylic acid. Furthermore, the α,β-unsaturated aldehyde corresponding to isobutylene, primary butyl alcohol, tertiary butyl alcohol, and methyl tertiary butyl ether 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 α,β-unsaturated carboxylic acid are preferably (meth)acrolein and (meth)acrylic acid, respectively, and more preferably methacrolein and methacrylic acid. Note that "(meth)acrolein" refers to acrolein and methacrolein, and "(meth)acrylic acid" refers to acrylic acid and methacrylic acid.

[0049] As a representative example, a method for producing methacrolein and methacrylic acid as α,β-unsaturated aldehyde and α,β-unsaturated carboxylic acid by oxidation of isobutylene using a catalyst produced by the method of the present invention will be described below. However, the following description can also be applied to cases where an alkene other than isobutylene, or an alcohol or an ether is used.

[0050] In this method, methacrolein and methacrylic acid are produced by contacting a raw material gas containing isobutylene and oxygen with a catalyst in a reactor. A fixed-bed reactor can be used as the reactor. The reactor is filled with a catalyst, and the raw material gas is supplied to the reactor to carry out the oxidation reaction. The catalyst layer may be a single layer, or multiple catalysts with different activities may be packed in separate layers. In addition, the catalyst may be diluted with an inert carrier and packed to control the activity.

[0051] The concentration of isobutylene in the feed gas is not particularly limited, but is preferably 1% by volume to 20% by volume, more preferably 3% by volume as the lower limit, and more preferably 10% by volume as the upper limit. The concentration of oxygen in the feed gas is preferably 0.1 mol to 5 mol per mol of isobutylene, more preferably 0.5 mol as the lower limit, and more preferably 3 mol as the upper limit. From an economical viewpoint, air is preferred as the oxygen source. If necessary, a gas enriched with oxygen by adding pure oxygen to air may be used.

[0052] The raw material gas may be isobutylene and oxygen (or an oxygen source) 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, methacrolein and methacrylic acid can be obtained in higher yields. The concentration of water vapor in the raw material gas is preferably 0.1% by volume to 50% by volume, more preferably 1% by volume as the lower limit, and more preferably 40% by volume as the upper limit.

[0053] The contact time between the raw material gas and the catalyst is preferably 0.5 seconds to 10 seconds, more preferably 1 second as the lower limit, and more preferably 6 seconds as the upper limit. The reaction pressure is preferably 0.1 MPa (G) to 1 MPa (G). Note that the MPa (G) in the reaction pressure means gauge pressure. The reaction temperature is preferably 200°C to 420°C, more preferably 250°C as the lower limit, and more preferably 400°C as the upper limit. In this manner, methacrolein and / or methacrylic acid can be obtained in high yield.

[0054] <Method for producing α,β-unsaturated carboxylic acid> In the method for producing α,β-unsaturated carboxylic acid according to the first aspect of the invention, an oxidation reaction of an α,β-unsaturated aldehyde is carried out in the presence of a catalyst produced by the method for producing a catalyst according to the first aspect of the invention. This allows for the production of an α,β-unsaturated carboxylic acid in high yield. The α,β-unsaturated aldehyde may be one produced by the method for producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid according to the first aspect of the invention.

[0055] Examples of the α,β-unsaturated aldehyde include (meth)acrolein, crotonaldehyde (β-methylacrolein), and cinnamaldehyde (β-phenylacrolein).

[0056] The resulting α,β-unsaturated carboxylic acid is an α,β-unsaturated carboxylic acid in which the aldehyde group in the α,β-unsaturated aldehyde is converted to a carboxyl group. For example, 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.

[0057] As a representative example, a method for producing methacrylic acid by the oxidation reaction of methacrolein using a catalyst produced by the method according to the present invention will be described below. However, the following description can also be applied to the case where an α,β-unsaturated aldehyde other than methacrolein is used. In this method, methacrylic acid is produced by contacting a raw material gas containing methacrolein and oxygen with the catalyst in a reactor. A fixed-bed reactor can be used as the reactor. The catalyst is packed into the reactor, and the raw material gas is supplied to the reactor to carry out the oxidation reaction. The catalyst layer may be a single layer, or multiple catalysts with different activities may be packed separately in multiple layers. Furthermore, to control the activity, the catalyst may be diluted with an inert carrier and packed.

[0058] The concentration of methacrolein in the raw material gas is not particularly limited, but is preferably 1% by volume to 20% by volume, more preferably 3% by volume as the lower limit, and more preferably 10% by volume as the upper limit. Methacrolein may contain small amounts of impurities that do not substantially affect the reaction, such as lower saturated aldehydes. The concentration of oxygen in the raw material gas is preferably 0.4 mol to 4 mol per mol of methacrolein, more preferably 0.5 mol as the lower limit, and more preferably 3 mol as the upper limit. From an economical viewpoint, air is preferred as the oxygen source. If necessary, a gas enriched with oxygen by adding pure oxygen to air may be used.

[0059] The raw material gas may be prepared by diluting methacrolein and oxygen (or an oxygen source) 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, methacrylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1% by volume to 50% by volume, more preferably 1% by volume as the lower limit, and more preferably 40% by volume as the upper limit.

[0060] The contact time between the raw material gas and the catalyst is preferably 0.1 seconds to 30 seconds, more preferably a lower limit of 1.0 second, and more preferably an upper limit of 10 seconds. The reaction pressure is preferably 0.1 MPa (G) to 1 MPa (G). The reaction temperature is not particularly limited, but is preferably 200°C to 450°C, more preferably a lower limit of 250°C, and more preferably an upper limit of 400°C. In this manner, methacrylic acid can be obtained in a high yield.

[0061] <Method for Producing α,β-Unsaturated Carboxylic Acid Ester> In the method for producing an α,β-unsaturated carboxylic acid ester according to the first aspect of the present invention, the α,β-unsaturated carboxylic acid produced by the method according to the first aspect of the present invention is esterified. That is, the method for producing an α,β-unsaturated carboxylic acid according to the first aspect of the present invention includes the steps of producing an α,β-unsaturated carboxylic acid by the method according to the first aspect of the present invention and esterifying the α,β-unsaturated carboxylic acid. According to this method, an α,β-unsaturated carboxylic acid ester can be obtained using an α,β-unsaturated carboxylic acid obtained by the oxidation reaction of an alkene, an alcohol, or an ether, or by the oxidation reaction of an α,β-unsaturated aldehyde.

[0062] The alcohol to be reacted with the α,β-unsaturated carboxylic acid is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, n-butanol, and isobutanol. Examples of the resulting α,β-unsaturated carboxylic acid ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. The esterification 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°C to 200°C.

[0063] <Second Invention> <Catalyst> The catalyst according to the second invention (hereinafter also referred to as "the present invention") is used when producing an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde. The catalyst is not particularly limited as long as it is a catalyst for producing an α,β-unsaturated carboxylic acid, but from the viewpoint of improving the yield in the production of an α,β-unsaturated carboxylic acid, it preferably contains at least phosphorus, molybdenum, and vanadium. Furthermore, the catalyst more preferably contains a catalyst having a composition represented by formula (II) above, and even more preferably has a composition represented by formula (II) above. Note that in the present invention, when the catalyst is formed using a support, the catalyst means one that includes the support, and the composition represented by formula (II) above is a composition that takes into account the support.

[0064] In the catalyst according to the present invention, the ratio (S / V) of the area-based median diameter (S) to the volume-based median diameter (V) in the pore distribution curve is 0.01 or more and 0.21 or less. Here, the area-based median diameter (S) and the volume-based median diameter (V) are values ​​obtained from the pore distribution curve obtained by mercury intrusion porosimetry. Specifically, the area-based median diameter (S) means the pore diameter (μm) showing the 50% cumulative pore surface area in a pore distribution curve created with the pore diameter on the horizontal axis and the cumulative pore surface area on the vertical axis. Furthermore, the volume-based median diameter (V) means the pore diameter (μm) showing the 50% cumulative pore volume in a pore distribution curve created with the pore diameter on the horizontal axis and the cumulative pore volume on the vertical axis. The present inventors have found that when the S / V ratio of a catalyst is 0.01 or more and 0.21 or less, the catalyst has high mechanical strength and is excellent in both catalytic activity and α,β-unsaturated carboxylic acid selectivity. They have also found that by carrying out an oxidation reaction of an α,β-unsaturated aldehyde using such a catalyst, an α,β-unsaturated carboxylic acid can be obtained in high yield.

[0065] The inventors of the present invention believe that the reason why α,β-unsaturated carboxylic acids can be obtained in high yields by using the catalyst of the present invention is as follows. The finer the particle size of the catalyst, the smaller the area-based median diameter (S). A smaller S usually leads to poorer reaction results in reactions using such a catalyst. On the other hand, it is believed that as the particle size becomes finer and the adhesion of the particles increases, the particles become less likely to collapse, and the volume-based median diameter (V) increases. In the present invention, it is believed that increasing V improves the diffusibility of the fluid (feedstock gas), thereby improving reaction results even when S is somewhat smaller. In other words, it is believed that S is related to the fineness of the particles, which is equal to mechanical strength, and V is related to the number of large pores, which is equal to reaction results (diffusibility of the feedstock gas).

[0066] As described above, the S / V of the catalyst according to the present invention is 0.01 or more and 0.21 or less. The S / V is preferably 0.18 or less, and more preferably 0.15 or less. The S / V of the catalyst is preferably the S / V measured for the catalyst after the molding treatment and calcination treatment described below. That is, in the present invention, the S / V of the catalyst is preferably the S / V of the catalyst that is a calcined product, and more preferably the S / V of the catalyst that is a calcined product of a catalyst molded body.

[0067] The area-based median diameter (S) is preferably 0.25 μm or less, more preferably 0.20 μm or less, from the viewpoint of the mechanical strength of the catalyst, and the volume-based median diameter (V) is preferably 1.00 μm or more, more preferably 1.20 μm or more, from the viewpoint of the yield of α,β-unsaturated carboxylic acid.

[0068] In the present invention, the shape change rate (%) and shape powder rate (%) of the catalyst can be used as another index of the mechanical strength of the catalyst. A smaller shape change rate and shape powder rate indicate a higher mechanical strength, and a larger value indicates a lower mechanical strength. That is, when the shape change rate and shape powder rate of the catalyst are small, cracks and chips can be easily prevented when the catalyst is packed into a reaction tube. The smaller the shape change rate of the catalyst, the more preferable it is, for example, preferably 5% or less, more preferably 3% or less, and even more preferably 2% or less. The smaller the shape powder rate of the catalyst, the more preferable it is, for example, preferably 2% or less, and more preferably 1% or less. The method for measuring the shape change rate and shape powder rate will be described in the Examples section. The shape change rate and shape powder rate are preferably measured on a catalyst molded body that has undergone the molding process described below. The shape change rate and shape powder rate may vary depending on the calcination conditions, so they are preferably measured on a catalyst molded body before the calcination process.

[0069] <Method for producing catalyst> The method for producing the catalyst according to the second invention is not particularly limited, but similar to the method for producing the catalyst according to the first invention, it is preferable to produce the catalyst by a method including the following steps (i)' to (iii)': (i') a step of dissolving or suspending raw material compounds for the catalyst in a solvent to prepare a solution or slurry (A); (ii)' a step of pressurizing the solution or slurry (A) and causing the pressurized solutions or slurries (A) to collide with each other to prepare a solution or slurry (B); and (iii)' a step of drying the solution or slurry (B) to obtain a dried product. Each step will be described below.

[0070] (Step (i)') For example, when the catalyst contains at least phosphorus, molybdenum, and vanadium, in the above step (i)', raw material compounds containing at least phosphorus and molybdenum are dissolved or suspended in a solvent as raw material compounds for the catalyst to prepare a solution or slurry (A) containing at least phosphorus and molybdenum. In this step, a raw material compound containing vanadium may also be added. The raw material compound containing vanadium may be added in the form of a raw material liquid added to a solvent. The method for preparing the solution or slurry (A) is not particularly limited, and it can be prepared by, for example, a precipitation method or an oxide mixing method. It is preferable to adjust the amount of the raw material compounds used so that the obtained catalyst has a composition represented by the above formula (II).

[0071] The type of raw material compound is not particularly limited, and examples thereof include the same compounds as those exemplified as the raw material compounds in the first invention. Examples of solvents include water, ethanol, and acetone. These may be used alone or in combination of two or more. Among these, it is preferable to use water as the solvent.

[0072] When the catalyst contains a catalyst having a composition represented by formula (II), step (i)' preferably includes the following steps (i-1)' and (i-2)': (i-1)' a step of dissolving or suspending a raw material compound containing at least phosphorus and molybdenum in a solvent to prepare a raw material liquid (A1); and (i-2)' a step of mixing the raw material liquid (A1) with a raw material compound (A2) containing the Z element in formula (II) to prepare the solution or slurry (A). Furthermore, when the catalyst contains a catalyst having a composition represented by formula (II), step (i)' preferably includes a step of dissolving or suspending a raw material compound containing at least phosphorus and molybdenum in a solvent to prepare a solution or slurry (A) containing a heteropolyacid salt having a Keggin structure. Note that steps (i-1)' and (i-2)' correspond to steps (i-1) and (i-2), respectively, in the first aspect of the present invention, and detailed description thereof will be omitted.

[0073] The "solution or slurry (A)", "step (ii)'", and "step (iii)'" in the second invention correspond to the "solution or slurry (A)", "step (ii)", and "step (iii)" in the first invention, respectively, and the explanations thereof in the first invention can also be applied to the second invention. However, "step (i)" and the like in the explanation of the first invention should be read as "step (i)'" and the like.

[0074] The dried product obtained in step (iii)' exhibits catalytic performance and can be used as a catalyst for producing an α,β-unsaturated carboxylic acid. Furthermore, by subjecting the obtained dried product to molding and calcination, as described below, the catalytic performance is further improved, which is preferable. In the present invention, the term "catalyst" collectively refers to the dried product obtained in step (iii)' as well as the product obtained by molding and / or calcining the dried product.

[0075] (Forming Step) In the forming step, the dried product obtained in the step (iii)' is formed as necessary to obtain a formed body (catalyst formed body). The forming step may be performed after the calcination step described below. For details of the forming step, the explanation of the forming step in the first aspect of the invention can be applied.

[0076] (Caustic Step) From the viewpoint of the yield of α,β-unsaturated carboxylic acid, it is preferable to calcinate the dried product obtained in step (iii)' or the molded product obtained in the molding step. As described above, in the present invention, it is more preferable to measure the area-based median diameter (S) and the volume-based median diameter (V) of the catalyst obtained by calcining the molded product, i.e., the calcined product of the catalyst molded product, and calculate S / V. For details of the calcination, the explanation of the calcination step in the first invention above can be applied. In this manner, the catalyst for producing α,β-unsaturated carboxylic acid according to the second invention can be produced.

[0077] <Method for producing α,β-unsaturated carboxylic acid> In the method for producing α,β-unsaturated carboxylic acid according to the second invention, an oxidation reaction of an α,β-unsaturated aldehyde is carried out in the presence of the catalyst according to the second invention. This makes it possible to produce α,β-unsaturated carboxylic acid in high yield. The catalyst may be a catalyst produced by the method for producing a catalyst according to the second invention. The method for producing α,β-unsaturated carboxylic acid according to the second invention corresponds to the method for producing α,β-unsaturated carboxylic acid according to the first invention, and a detailed description thereof will be omitted.

[0078] <Method for Producing α,β-Unsaturated Carboxylic Acid Ester> In the method for producing an α,β-unsaturated carboxylic acid ester according to the second invention, the α,β-unsaturated carboxylic acid produced by the method according to the second invention is esterified. That is, the method for producing an α,β-unsaturated carboxylic acid according to the second invention comprises the steps of producing an α,β-unsaturated carboxylic acid by the method according to the second invention and esterifying the α,β-unsaturated carboxylic acid. According to this method, an α,β-unsaturated carboxylic acid ester can be obtained using an α,β-unsaturated carboxylic acid obtained by the oxidation reaction of an α,β-unsaturated aldehyde using the catalyst according to the second invention. Note that the method for producing an α,β-unsaturated carboxylic acid ester according to the second invention corresponds to the method for producing an α,β-unsaturated carboxylic acid ester according to the first invention, and a detailed description thereof will be omitted.

[0079] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these examples. In the following description, "parts" means "parts by mass."

[0080] <Catalyst Composition> The molar ratio of each element in the catalyst composition was determined by analyzing a solution of the catalyst dissolved in ammonia water by ICP atomic emission spectrometry. The molar ratio of ammonium radicals was determined by analyzing the catalyst by Kjeldahl method.

[0081] <Analysis of Raw Material Gas and Product> The raw material gas and product were analyzed using gas chromatography (apparatus: GC-2014 (trade name), manufactured by Horiba, Ltd.; column: DB-FFAP (trade name), 30 m × 0.32 mm, film thickness 1.0 μm, manufactured by Agilent Technologies, Inc.). From the results of gas chromatography, the yield of methacrylic acid was calculated using the following formula: Yield of methacrylic acid (%) = (N2 / N1) × 100, where N1 is the number of moles of methacrolein supplied, and N2 is the number of moles of methacrylic acid produced.

[0082] <Average particle size of particles contained in slurry> The average particle size of particles contained in the slurry was measured by a laser diffraction particle size distribution measurement method using a particle size distribution measurement device (product name: LA-960, manufactured by Horiba, Ltd.) In the obtained volume-based particle size distribution, the average diameter calculated from the arithmetic mean was defined as the average particle size.

[0083] <Shape Change Rate and Shape Powdering Rate of Catalyst> 100 g of catalyst (catalyst molded body) was weighed, and the number of catalyst molded bodies contained in 100 g of catalyst was designated as A. 100 g of the catalyst was dropped from the upper opening of a stainless steel cylinder with an inner diameter of 27.5 mm and a length of 6 m, which was installed so that its longitudinal direction was vertical and whose lower opening was closed with a stainless steel plate, to fill the cylinder. Of the catalyst recovered by opening the lower opening of the cylinder, the mass of the catalyst that did not pass through a sieve with 1 mm openings was designated as X g, and the number of catalyst molded bodies contained in X g of catalyst was designated as B. From the obtained values ​​of A, B, and X, the shape change rate and shape powdering rate were calculated using the following formulas: Shape change rate (%) = 100 × {(100 / A - X / B) / (100 / A)}; Shape powdering rate (%) = {(100 - X) / 100} × 100.

[0084] <BET Specific Surface Area of ​​Catalyst> The BET specific surface area of ​​the catalyst (calcined product of catalyst molded body) was calculated by the BET single-point method using nitrogen adsorption using Macsorb (trade name: HM model-1208, manufactured by Mountec Co., Ltd.).

[0085] <Area-based median diameter (S) and volume-based median diameter (V) of catalyst> Pore distribution measurement was performed under the following conditions using a mercury intrusion pore distribution measurement device AutoPore IV-9500 (trade name, manufactured by Micrometrics). From the obtained pore distribution curve, the area-based median diameter (S) and volume-based median diameter (V) of the catalyst (calcined product of catalyst molded body) were calculated. Measurement sample: 10 calcined products of catalyst molded body Cell volume: 1.131 mL Initial evacuation: 5 minutes at 50 μmHg Equilibration waiting time: 5 minutes Measurement pressure range: 0.0038 to 207 MPa Measurement pore diameter range: 0.006 to 329 μm

[0086] The physical properties of the mercury used in the measurements using the mercury intrusion porosimetry analyzer were as follows: Mercury contact angle: 130° Mercury surface tension: 485 dynes / cm Mercury density: 13.5335 g / mL

[0087] [Example 1] Pure water was used as the solvent. First, 100 parts of molybdenum trioxide, 7.5 parts of ammonium metavanadate, 11.4 parts of an 85% by mass aqueous phosphoric acid solution, and 7.0 parts of copper (II) nitrate trihydrate were added to 400 parts of pure water at 25 ° C. The resulting mixture was heated to 95 ° C. while stirring at a rotation speed of 110 rpm using a rotary blade stirrer, and then stirred for 3 hours while maintaining the liquid temperature at 95 ° C. to prepare a raw material solution (A1). Next, while maintaining the raw material solution (A1) at 95 ° C., a raw material solution (hereinafter referred to as "cesium raw material solution") in which 135 parts of cesium bicarbonate were dissolved in 200 parts of pure water and a raw material solution (hereinafter referred to as "ammonium root raw material solution") in which 92 parts of ammonium carbonate were dissolved in 260 parts of pure water were added to the raw material solution (A1) and stirred for 30 minutes. As described above, a slurry (A) containing a heteropolyacid salt having a Keggin structure was prepared (step (i)). The average particle size of the particles contained in the slurry (A) was 1.1 μm. The obtained slurry (A) was cooled to 30° C., and then pressurized to 150 MPa using a wet atomization device STAR BURST (trade name, model: HJP-25005V2, manufactured by Sugino Machine Co., Ltd.). The pressurized slurry (A) was then sprayed from a pair of nozzles to perform an atomization treatment once, in which the particles contained in the slurry (A) collided obliquely with each other, to prepare a slurry (B) (step (ii)). The average particle size of the particles contained in the slurry (B) was 0.3 μm. Next, the obtained slurry (B) was spray-dried at a dryer inlet temperature of 300° C. to obtain a dried product (catalyst) (step (iii): drying step). The composition of the dried product, excluding oxygen, was as follows: P １．６ Mo １２ V ０．５ Cu ０．２ Cs １．２ (NH ４ ) ３．８Next, 100 parts of the dried product were mixed with 4 parts of hydroxypropyl cellulose, 3 parts of pure water, and 16 parts of ethanol, and kneaded until a clay-like mixture was obtained. The mixture was extruded using an extrusion molding machine at an extrusion pressure of 10 MPa to form a cylindrical shape with a diameter of 5.5 mm and a height of 5 mm, and dried at 70°C for 12 hours under air flow to obtain a molded product (catalyst molded product). The shape change rate and shape powdering rate of the molded product were measured. In addition, the molded product was crushed and then heat-treated at 380°C for 5 hours under air flow to obtain a calcined catalyst. The BET specific surface area of ​​the obtained catalyst was 6.0 m ２ / g and S / V was 0.14.

[0088] The obtained catalyst was packed into a reaction tube equipped with a fixed-bed reactor, and a raw material gas consisting of 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of steam, and 55% by volume of nitrogen was passed through the reactor so that the contact time between the catalyst and the raw material gas was 3.5 seconds. The reaction temperature was adjusted so that the methacrolein conversion rate was 85%. The reaction pressure was 0.1 MPa (G). The product was collected from the reactor and analyzed by gas chromatography, and the methacrylic acid yield was calculated based on the obtained results. The methacrylic acid yield was 76%. The results are shown in Table 1.

[0089] [Example 2] A catalyst was obtained by molding and calcining in the same manner as in Example 1, except that the stirring time after adding the cesium raw material solution and the ammonium root raw material solution to the raw material solution (A1) was changed to 45 minutes. The average particle size of the particles contained in the slurry (A) was 1.6 μm, and the average particle size of the particles contained in the slurry (B) was 0.4 μm. The shape change rate and shape powdering rate of the molded body are shown in Table 1. The BET specific surface area of ​​the obtained catalyst was 6.4 m ２ / g, and S / V was 0.05. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1, and the yield of methacrylic acid was calculated. The yield of methacrylic acid was 77%. The results are shown in Table 1.

[0090] Comparative Example 1 A catalyst was obtained by molding and calcining in the same manner as in Example 1, except that the slurry (A) was prepared without being subjected to atomization treatment and then spray-dried to obtain a dried product. The shape change rate and shape powdering rate of the molded body are shown in Table 1. The BET specific surface area of ​​the obtained catalyst was 5.5 m ２ / g, and S / V was 0.74. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1, and the yield of methacrylic acid was calculated. The yield of methacrylic acid was 74%. The results are shown in Table 1.

[0091] Comparative Example 2 A catalyst was obtained by molding and calcining in the same manner as in Example 2, except that the slurry (A) was prepared without being subjected to atomization treatment and then spray-dried to obtain a dried product. The shape change rate and shape powdering rate of the molded body are shown in Table 1. The BET specific surface area of ​​the obtained catalyst was 3.2 m ２ / g, and S / V was 0.22. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1, and the yield of methacrylic acid was calculated. The yield of methacrylic acid was 75%. The results are shown in Table 1.

[0092] Comparative Example 3 A catalyst was obtained by molding and calcining in the same manner as in Example 1, except that in step (ii) before the drying step, a homogenizer (product name: T.K. Homomixer MARK II 2.5 type, manufactured by Primix Corporation) was used instead of the wet atomization device STAR BURST, and treatment was performed at 12,000 rpm for 30 minutes. The shape change rate and shape powdering rate of the molded body are shown in Table 1. The BET specific surface area of ​​the obtained catalyst was 5.4 m ２ / g, and S / V was 0.55. Using the obtained catalyst, an oxidation reaction of methacrolein was carried out in the same manner as in Example 1, and the yield of methacrylic acid was calculated. The yield of methacrylic acid was 75%. The results are shown in Table 1.

[0093]

[0094] As shown in Table 1, it was confirmed that in Examples 1 and 2, in which the oxidation reaction of methacrolein was carried out using the catalyst produced by the method according to the first invention, methacrylic acid was obtained in a high yield. On the other hand, in Comparative Examples 1 and 2, in which the atomization step for preparing slurry (B) was not carried out, the BET specific surface area of ​​the obtained catalyst was small, and the methacrylic acid yield was inferior to that of Examples 1 and 2. Furthermore, in Comparative Example 3, in which slurry (B) was prepared using a homogenizer, no change was observed in the average particle size of the particles contained in the slurry.

[0095] Furthermore, as shown in Table 1, the catalysts according to Examples 1 and 2, which have an S / V ratio within the range specified in the second invention, have small shape change rates and shape powdering rates, and it was confirmed that when used in the oxidation reaction of methacrolein, methacrylic acid can be obtained in high yield. On the other hand, the catalysts according to Comparative Examples 1 to 3, which do not have an S / V ratio within the range specified in the second invention, have particularly large shape change rates and, when used in the oxidation reaction of methacrolein, the methacrylic acid yield was low. In Comparative Example 3, in which the atomization step was performed using a homogenizer, the V value was not sufficiently improved. Note that methacrylic acid esters can be obtained by esterifying the methacrylic acid obtained in the above examples.

[0096] According to the first invention of the present application, a catalyst capable of achieving a high yield of the target product in the production of an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid can be provided by a simple method, which is industrially useful. Also, according to the second invention of the present application, a catalyst capable of achieving a high yield of methacrylic acid and having excellent mechanical strength can be provided in the production of an α,β-unsaturated carboxylic acid, which is industrially useful.

Claims

1. A method for producing a catalyst used in producing an α,β-unsaturated aldehyde and / or an α,β-unsaturated carboxylic acid by an oxidation reaction, comprising the following steps (i) to (iii): (i) a step of dissolving or suspending a raw material compound containing molybdenum in a solvent to prepare a solution or slurry (A); (ii) a step of pressurizing the solution or slurry (A) and causing the pressurized solutions or slurries (A) to collide with each other to prepare a solution or slurry (B); and (iii) a step of drying the solution or slurry (B) to obtain a dried product.

2. The method for producing a catalyst according to claim 1, wherein in step (ii), the pressurized solution or slurry (A) is sprayed from two or more nozzles to cause the solutions or slurries (A) to collide with each other.

3. The method for producing a catalyst according to claim 1, wherein in step (ii), particles contained in the pressurized solution or slurry (A) are caused to collide with each other obliquely.

4. The method for producing a catalyst according to claim 1, wherein in step (ii), the solution or slurry (A) is pressurized to 50 MPa or more.

5. The method for producing a catalyst according to claim 1, wherein the average particle size of the particles contained in the solution or slurry (A) obtained in step (i) is 1.0 μm or more.

6. The method for producing a catalyst according to claim 1, wherein the average particle size of the particles contained in the solution or slurry (B) obtained in step (ii) is 0.5 μm or less.

7. The method for producing a catalyst according to claim 1, wherein the catalyst is a catalyst used in producing α,β-unsaturated aldehydes and α,β-unsaturated carboxylic acids by oxidation of alkenes, alcohols, or ethers.

8. The method for producing a catalyst according to claim 7, wherein the catalyst has a composition represented by the following formula (I): Mo ａ１ Bi ｂ１ Fe ｃ１ A ｄ１ E ｅ１ G ｆ１ J ｇ１ Si ｈ１ (NH ４ ) ｉ１ O ｊ１ (I) In formula (I), Mo, Bi, Fe, Si, NH ４ , and O represent molybdenum, bismuth, iron, silicon, ammonium, and oxygen, respectively; A represents at least one element selected from the group consisting of cobalt and nickel; E represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, thallium, tantalum, and zinc; G represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. J represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; a1 to j1 represent the molar ratios of each component, and when a1 = 12, b1 = 0.01 to 3, c1 = 0.01 to 5, d1 = 0.01 to 12, e1 = 0 to 8, f1 = 0 to 5, g1 = 0.001 to 2, h1 = 0 to 20, and i1 = 0 to 30; and j1 is the molar ratio of oxygen necessary to satisfy the valence of each component.

9. The method for producing a catalyst according to claim 1, wherein the catalyst is a catalyst used in producing an α,β-unsaturated carboxylic acid by the oxidation reaction of an α,β-unsaturated aldehyde.

10. The method for producing a catalyst according to claim 9, wherein the catalyst has a composition represented by the following formula (II): P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ X ｅ２ Y ｆ２ Z ｇ２ (NH ４ ) ｈ２ O ｉ２ (II) In formula (II), P, Mo, V, Cu, NH ４ , and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; X represents at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony, and bismuth; Y represents at least one element selected from the group consisting of niobium, tantalum, tungsten, cerium, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, and lanthanum; Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; a2 to 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 = 0.01 to 3, and h2 = 0.01 to 30; and i2 is the molar ratio of oxygen necessary to satisfy the valence of each component.

11. The method for producing a catalyst according to claim 10, wherein in the step (i), the solution or slurry (A) is prepared by mixing a raw material liquid (A1) containing phosphorus and molybdenum with a raw material compound (A2) containing the Z element in formula (II).

12. The method for producing a catalyst according to claim 11, wherein in step (i), the temperature of the raw material liquid (A1) mixed with the raw material compound (A2) containing the Z element in formula (II) is 30°C or higher.

13. A catalyst used in the production of an α,β-unsaturated carboxylic acid by oxidizing an α,β-unsaturated aldehyde, in which the ratio (S / V) of the area-based median diameter (S) to the volume-based median diameter (V) in the pore distribution curve is 0.01 or more and 0.21 or less.

14. The catalyst according to claim 13, wherein the area-based median diameter (S) is 0.25 μm or less.

15. The catalyst according to claim 13, wherein the volume-based median diameter (V) is 1.20 μm or more.

16. The catalyst of claim 13, wherein the catalyst contains phosphorus, molybdenum, and vanadium.

17. The catalyst according to claim 13, wherein the catalyst has a composition represented by the following formula (II): P ａ２ Mo ｂ２ V ｃ２ Cu ｄ２ X ｅ２ Y ｆ２ Z ｇ２ (NH ４ ) ｈ２ O ｉ２ (II) In formula (II), P, Mo, V, Cu, NH ４ , and O represent phosphorus, molybdenum, vanadium, copper, ammonium, and oxygen, respectively; X represents at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony, and bismuth; Y represents at least one element selected from the group consisting of niobium, tantalum, tungsten, cerium, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, and lanthanum; Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium; a2 to 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 = 0.01 to 3, and h2 = 0.01 to 30; and i2 is the molar ratio of oxygen necessary to satisfy the valence of each component.

18. A method for producing a catalyst according to any one of claims 13 to 17, comprising the steps of: preparing a solution or slurry (A) containing a heteropolyacid salt having a Keggin structure; and pressurizing the solution or slurry (A) and causing the pressurized solutions or slurries (A) to collide with each other to prepare a solution or slurry (B).

19. A method for producing an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid, comprising the step of oxidizing an alkene, an alcohol, or an ether in the presence of a catalyst produced by the method according to any one of claims 1 to 8 to produce an α,β-unsaturated aldehyde and an α,β-unsaturated carboxylic acid.

20. A method for producing an α,β-unsaturated carboxylic acid, comprising the step of oxidizing an α,β-unsaturated aldehyde in the presence of a catalyst produced by the method according to any one of claims 1 to 6 and 9 to 12, or the catalyst according to any one of claims 13 to 17.

21. A method for producing an α,β-unsaturated carboxylic acid ester, which comprises esterifying the α,β-unsaturated carboxylic acid produced by the method of claim 19.

22. A method for producing an α,β-unsaturated carboxylic acid ester, which comprises esterifying the α,β-unsaturated carboxylic acid produced by the method according to claim 20.

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