Method for producing catalyst for producing methacrylic acid

Abstract

To provide a method for producing a catalyst for producing methacrylic acid capable of more improving production efficiency, and capable of more reducing production cost.SOLUTION: A method for producing a catalyst for producing methacrylic acid includes: a process (1) of preparing a first slurry containing a first heteropolyacid compound particle including at least molybdenum, phosphorus, copper, vanadium, and cesium; a process (2) of preparing a second slurry containing a second heteropolyacid compound particle having a rate of a heteropolyacid compound particle having a median size of 0.50-8.0 μm, and a particle size of 10 μm or under of 65% or more when converting on volumetric basis by performing a laser diffraction type particle distribution measurement by subjecting the first slurry to wet pulverization treatment; a process (3) of kneading, and extruding a dried body including a second heteropolyacid compound particle obtained by drying the second slurry to obtain a molded body; and a process (4) of calcining the molded body to obtain a catalyst for producing methacrylic acid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a catalyst for producing methacrylic acid.

Background Art

[0002] Conventionally, as a catalyst used for producing methacrylic acid by a gas-phase catalytic oxidation reaction such as methacrolein, it is known that heteropolyacids containing phosphorus and molybdenum and salts thereof are effective. Such a catalyst is usually produced by drying an aqueous mixture containing a catalyst raw material and then firing it (see Patent Document 1).

[0003] Specifically, Patent Document 1 discloses a method for producing a catalyst for producing methacrylic acid, which improves the preparation process of a Dawson-type heteropolyacid salt as a catalyst precursor for the purpose of providing a catalyst having higher reaction activity, selectivity, catalyst strength, and a long catalyst life.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the conventional method for producing a catalyst for producing methacrylic acid represented by Patent Document 1 above, the production efficiency of the catalyst for producing methacrylic acid may decrease due to a predetermined process.

[0006] Therefore, there is a need for a method for producing a catalyst for producing methacrylic acid that can further improve the production efficiency and thus further reduce the production cost.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by carrying out a predetermined process in a method for producing a catalyst for methacrylic acid production, and have completed the present invention.

[0008] That is, the present invention provides the following [1] to [7]. [1] A method for producing a catalyst for methacrylic acid production, comprising the following steps (1) to (4). [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium [Step (2)] By subjecting the first slurry to wet grinding treatment, when laser diffraction particle size distribution measurement is performed and converted on a volume basis, the median diameter (D50) is 0.50 to 8.0 μm, and the proportion of heteropolyacid compound particles having a particle diameter of 10 μm or less is 65% or more. A step of preparing a second slurry containing second heteropolyacid compound particles [Step (3)] A step of kneading a dried product containing the second heteropolyacid compound particles obtained by drying the second slurry, and extrusion-molding to obtain a molded product [Step (4)] A step of firing the molded product to obtain a catalyst for methacrylic acid production [2] The method for producing a catalyst for methacrylic acid production according to [1], wherein when laser diffraction particle size distribution measurement is performed and converted on a volume basis, the 10% particle diameter (D10) of the second heteropolyacid compound particles contained in the second slurry is 0.30 μm or more and 1.8 μm or less. [3] The method for producing a catalyst for methacrylic acid production according to [1] or [2], wherein when laser diffraction particle size distribution measurement is performed and converted on a volume basis, the 90% particle diameter (D90) of the second heteropolyacid compound particles contained in the second slurry is 2.0 μm or more and 17 μm or less. [4] The method for producing a catalyst for methacrylic acid production according to any one of [1] to [3], wherein the wet grinding treatment is performed at a temperature of 0°C or higher and 80°C or lower. [5] The method for producing a catalyst for methacrylic acid production according to any one of [1] to [4], wherein the step (4) is a step of firing the molded body at 360°C to 410°C in an oxidizing gas atmosphere and then firing it at 420°C to 500°C in a non-oxidizing gas atmosphere. [6] The heteropolyacid compound contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles is represented by the following formula (I): P a Mo b Cu c V d Cs e Y f O x (I) (In formula (I), P represents a phosphorus atom, Mo represents a molybdenum atom, Cu represents a copper atom, V represents a vanadium atom, Cs represents a cesium atom, O represents an oxygen atom, Y represents at least one atom selected from the group consisting of an arsenic atom, an antimony atom, a boron atom, a silver atom, a bismuth atom, an iron atom, a cobalt atom, a lanthanum atom, and a cerium atom, a to f represent values that satisfy the conditions of 1.2 ≤ a ≤ 1.8, 0.01 ≤ c ≤ 0.4, 0.4 ≤ d ≤ 0.6, 1.2 ≤ e ≤ 1.8, and 0.4 ≤ f ≤ 0.6 when b is 12, x represents a value determined by the oxidation state of each atom, and f represents the total ratio of the two or more atoms when Y is two or more atoms.) The method for producing a catalyst for methacrylic acid production according to any one of [1] to [5], which is a partially neutralized salt of a heteropolyacid represented by the formula. [7] A method for producing methacrylic acid, which includes a step of subjecting a catalyst for methacrylic acid production produced by the method for producing a catalyst for methacrylic acid production according to any one of [1] to [6] to a gas-phase catalytic oxidation reaction by contacting it with at least one compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane, and isobutyric acid to obtain methacrylic acid. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a method for producing a catalyst for methacrylic acid production that can further improve the production efficiency of the catalyst for methacrylic acid production and can further reduce the production cost.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present invention will be specifically described. The present invention is not limited to the specific embodiments shown below.

[0011] 1. Method for Producing Catalyst for Methacrylic Acid Production The method for producing a catalyst for methacrylic acid production according to the present embodiment (hereinafter, may be simply referred to as "production method") is a method for producing a catalyst for methacrylic acid production containing heteropolyacid compound particles, including the following steps (1) to (4). [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium [Step (2)] A step of subjecting the first slurry to wet grinding treatment, and when performing laser diffraction particle size distribution measurement and converting on a volume basis, the median diameter (D50) is 0.50 to 8.0 μm, and the proportion of heteropolyacid compound particles having a particle diameter of 10 μm or less is 65% or more, to prepare a second slurry containing second heteropolyacid compound particles [Step (3)] A step of forming a molded body containing the solid second heteropolyacid compound particles obtained by drying the second slurry by extrusion molding [Step (4)] A step of firing the molded body to obtain a catalyst for methacrylic acid production

[0012] Hereinafter, the above steps (1) to (4) according to the method for producing a catalyst for methacrylic acid production of the present embodiment will be specifically described.

[0013] (1) [Step (1)] (A step of preparing a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium) Step (1) is a step of preparing a first slurry containing first heteropolyacid compound particles.

[0014] The first slurry prepared in step (1) of the production method according to the present embodiment contains first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium.

[0015] In step (1), first, a compound containing an element that can be contained in the heteropolyacid compound particles contained in the catalyst for methacrylic acid production, that is, a mixture of raw material compounds, is prepared.

[0016] Examples of the raw material compounds include oxoacids, oxoacid salts, oxides, nitrates, carbonates, bicarbonates, hydroxides, and halides containing at least molybdenum, phosphorus, copper, vanadium, cesium, and other allowable elements (details will be described later).

[0017] In the present embodiment, examples of the compound containing molybdenum as an element include molybdic acid, molybdate (ammonium heptamolybdate tetrahydrate), molybdenum oxide, and molybdenum chloride. Examples of the compound containing phosphorus as an element include phosphoric acid (orthophosphoric acid) and phosphate. Examples of the compound containing copper as an element include cuprous oxide, cupric oxide, copper peroxide, copper nitrate, basic copper carbonate, copper hydroxide, and copper halide. Examples of the compound containing vanadium as an element include vanadic acid, vanadate (ammonium metavanadate), vanadium oxide, and vanadium chloride. Examples of the compound containing cesium as an element include cesium oxide, cesium peroxide, cesium superoxide, cesium nitrate, cesium carbonate, cesium hydroxide, and cesium halide.

[0018] In the present embodiment, examples of the compound containing "other elements" include oxides, nitrates, carbonates, bicarbonates, hydroxides, oxoacids, oxoacid salts, and halides.

[0019] In the present embodiment, when referring to "halide", from the perspective of corrosion, it is preferably a chloride, bromide, or iodide, and more specifically, it is preferably cesium chloride, cesium bromide, and cesium iodide.

[0020] In step (1), a first slurry for producing a catalyst for methacrylic acid production is prepared using the above mixture of raw material compounds.

[0021] Specifically, an aqueous solution is prepared by mixing and dissolving the raw material compounds in water (e.g., ion-exchanged water), or a liquid in which the raw material compounds are mixed and suspended is prepared as a mixture, and further aged at any conventionally known suitable temperature and time to obtain a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium.

[0022] The aging temperature in step (1) is not particularly limited. The aging temperature in step (1) is usually 30°C or higher and less than 200°C, preferably 100°C or higher and less than 140°C.

[0023] In step (1), when preparing an aqueous solution, a mixed solution, or a suspension, which is a mixture for obtaining the first slurry, it is preferable to further add ammonia or an ammonium salt to obtain an aqueous solution, a mixed solution, or a suspension containing ammonia or an ammonium salt.

[0024] Also, in step (1), instead of adding ammonia or an ammonium salt when preparing an aqueous solution, a mixed solution, or a suspension, which is a mixture for obtaining the first slurry, an ammonium compound may be used as at least one of the raw material compounds containing at least molybdenum, phosphorus, copper, vanadium, and cesium. By using an ammonium compound in this way, for example, a first slurry containing first heteropolyacid compound particles containing a non-Keggin type heteropolyacid salt can be obtained.

[0025] Here, the first heteropolyacid compound particles obtainable by step (1) preferably have a median diameter (D50) of 5 μm or more and 200 μm or less, more preferably 8 μm or more and 150 μm or less, when measured by laser diffraction particle size distribution and converted on a volume basis.

[0026] Regarding the particle size of the first heteropolyacid compound particles obtainable by step (1), when measured by laser diffraction particle size distribution and converted on a volume basis, the 10% particle size (D10) of the first heteropolyacid compound particles contained in the first slurry is preferably 1.6 μm or more and 50 μm or less, more preferably 2.0 μm or more and 30 μm or less.

[0027] Regarding the particle size of the first heteropolyacid compound particles obtainable by step (1), when measured by laser diffraction particle size distribution and converted on a volume basis, the 90% particle size (D90) of the first heteropolyacid compound particles contained in the first slurry is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 300 μm or less.

[0028] (2) [Step (2)] (A step of preparing a second slurry containing second heteropolyacid compound particles having a median diameter (D50) of 0.50 to 8.0 μm and a proportion of heteropolyacid compound particles having a particle size of 10 μm or less of 65% or more when measured by laser diffraction particle size distribution and converted on a volume basis by subjecting the first slurry to wet grinding treatment) In step (2), wet grinding treatment is performed on the first slurry prepared in step (1).

[0029] Specifically, by wet grinding treatment, the first heteropolyacid compound particles contained in the first slurry are converted to a second slurry containing second heteropolyacid compound particles having a median diameter (D50) of 0.50 to 8.0 μm and a proportion of heteropolyacid compound particles having a particle size of 10 μm or less of 65% or more when measured by laser diffraction particle size distribution and converted on a volume basis.

[0030] Here, as the wet pulverization treatment, any conventionally known and arbitrarily suitable treatment including a crushing treatment and a dispersion treatment can be adopted. Specifically, for example, the wet pulverization treatment can be carried out using a homomixer (e.g., ULTRA-DISPERSER LK-41), a ball mill, a bead mill, and a dyno mill.

[0031] Regarding the conditions of the wet pulverization treatment, for example, when using a homomixer, from the viewpoint of making the particle size of the second heteropolyacid compound particles contained in the second slurry smaller to improve the extrudability, specifically, the treatment time is preferably 30 seconds or longer. In order to make the particle size (median diameter, 10% particle diameter, and 90% particle diameter) of the second heteropolyacid compound particles contained in the second slurry smaller after the pulverization treatment and adjust it to the preferred particle size range, the treatment time may be extended, and further, the number of times of implementation may be increased. From the viewpoint of preventing the volatilization of the solvent component and avoiding the freezing of the slurry, the temperature of the slurry is preferably 0°C or higher and 80°C or lower, and more preferably 0°C or higher and 40°C or lower.

[0032] In the present embodiment, the wet grinding treatment in step (2) is preferably carried out at a temperature of 0°C or higher and 80°C or lower from the viewpoints of the durability of the selected equipment and avoiding the freezing of the slurry, more preferably at a temperature of 0°C or higher and 50°C or lower from the viewpoint of suppressing the wear of the equipment, and even more preferably at a temperature of 0°C or higher and 40°C or lower from the viewpoint of the material constraints of the equipment. Further, the treatment time for the wet grinding treatment can be adjusted as appropriate to obtain a second slurry containing second heteropolyacid compound particles having a predetermined particle size. Specifically, for example, in order to adjust the particle size (median diameter, 10% particle size, and 90% particle size) of the heteropolyacid compound particles after the wet grinding treatment to be within a preferable particle size range, the time for the wet grinding treatment may be extended, or further, the number of times of implementation may be increased. Specifically, when carrying out the wet grinding treatment using a Dyno-Mill, the treatment time for the wet grinding treatment can be extended by making the supply rate of the first slurry slower, and the number of treatment times can be increased by carrying out the grinding treatment again on the slurry after the wet grinding treatment. Further, the wet grinding treatment may be carried out after diluting the first slurry with water or a solvent in advance.

[0033] In the present embodiment, the "particle size of the second heteropolyacid compound particles (median diameter (D50), 10% particle size (D10), 90% particle size (D90))", and further the "proportion of heteropolyacid compound particles having a particle size of 10 μm or less" can be measured by the laser diffraction scattering method according to a conventional method. The measurement of the particle size of the second heteropolyacid compound particles, that is, the laser diffraction particle size distribution measurement, is carried out under any suitable conditions known in the art using any suitable measuring device known in the art, and the value obtained by converting on a volume basis can be used. As the device capable of measuring the particle size (proportion of particles having a predetermined particle size), specifically, for example, "Microtrac" manufactured by Nikkiso Co., Ltd., "LA" manufactured by Horiba, Ltd., "CILAS" manufactured by Cilas, "Mastersizer" manufactured by Malvern, and "LS" manufactured by Beckman Coulter can be mentioned.

[0034] In this embodiment, the second heteropolyacid compound particles that can be obtained by wet grinding treatment preferably have a median diameter (D50) of 0.50 to 8.0 μm, more preferably 0.50 to 7.2 μm, still more preferably 1.3 to 7.2 μm, and the proportion of heteropolyacid compound particles having a particle diameter of 10 μm or less is preferably 65% or more, more preferably 70% to 100% from the viewpoint of improving extrudability when measured by laser diffraction particle size distribution and converted on a volume basis.

[0035] Regarding the particle diameter of the second heteropolyacid compound particles that can be obtained by wet grinding treatment, when measured by laser diffraction particle size distribution and converted on a volume basis, the 10% particle diameter (D10) of the second heteropolyacid compound particles contained in the second slurry is preferably 0.30 μm or more and 1.8 μm or less, more preferably 0.6 μm or more and 1.5 μm or less from the viewpoint of further improving extrudability.

[0036] Regarding the particle diameter of the second heteropolyacid compound particles that can be obtained by wet grinding treatment, when measured by laser diffraction particle size distribution and converted on a volume basis, the 90% particle diameter (D90) of the second heteropolyacid compound particles contained in the second slurry is preferably 2.0 μm or more and 17 μm or less, more preferably 2.6 μm or more and 15.2 μm or less from the viewpoint of further improving extrudability.

[0037] In the case of using, for example, a homomixer, the conditions for wet grinding treatment are preferably set, in view of the performance of the selected equipment, specifically, at a temperature of 0°C or higher and 80°C or lower, more preferably at a temperature of 0°C or higher and 65°C or lower, and it is preferable to carry out the treatment in consideration of suitable treatment time and number of treatments. When adjusting the particle size (median diameter, 10% particle size, and 90% particle size) to the above range and setting the proportion of heteropolyacid compound particles having a particle size of 10 μm or less to 65% or more, for example, it is preferably carried out at a treatment time of 30 seconds or more and 600 seconds or less. However, when the particle size after treatment is too large, it is preferable to carry out the wet grinding treatment again for the purpose of increasing the number of treatments in order to adjust the particle size within the suitable range already described. After carrying out the wet grinding treatment again, it is more preferable to measure the particle size again to confirm whether it is within the preferable particle size range, and if it is not within the preferable range, it is more preferable to determine to extend the treatment time or increase the number of treatments.

[0038] The properties such as the viscosity of the second slurry are not particularly limited as long as they can be applied to the subsequent steps. For example, from the viewpoint of more efficient preparation, they can have any conventionally known suitable properties. Specifically, the properties of the second slurry can be adjusted, for example, by adjusting the content of the liquid already described or further adding a solvent for dilution.

[0039] Here, the heteropolyacid compounds that can be contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles of the present embodiment, which can be produced by steps (1) and (2), will be described.

[0040] (Heteropolyacid compound) The catalyst for producing methacrylic acid of the present embodiment contains a heteropolyacid compound that can contain at least phosphorus and molybdenum. In the present embodiment, the heteropolyacid compound may contain free heteropolyacid or a salt of heteropolyacid.

[0041] The catalyst for methacrylic acid production in this embodiment preferably contains, as a heteropolyacid compound, an acidic salt (partial neutralization salt) of a heteropolyacid among salts of heteropolyacids, and more preferably contains an acidic salt of a Keggin-type heteropolyacid.

[0042] The heteropolyacid compound contains at least phosphorus and molybdenum, and may further contain other elements on the condition that the catalytic activity is not inhibited. Examples of other elements include vanadium, potassium, rubidium, cesium, thallium, copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium. That is, the heteropolyacid compound of this embodiment preferably contains, for example, the following elements. Phosphorus; Molybdenum; Copper; Vanadium; At least one element selected from the group consisting of cesium and thallium; and At least one element selected from the group consisting of arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium

[0043] In this embodiment, the heteropolyacid compound that can be included in the heteropolyacid compound particles, that is, the first heteropolyacid compound particles and the second heteropolyacid compound particles, is preferably a partial neutralization salt of a heteropolyacid represented by the following formula (I). P a Mo b Cu c V d Cs e Y f O x (I)

[0044] In formula (I), P represents a phosphorus atom, Mo represents a molybdenum atom, Cu represents a copper atom, V represents a vanadium atom, Cs represents a cesium atom, O represents an oxygen atom, Y represents at least one atom selected from the group consisting of an arsenic atom, an antimony atom, a boron atom, a silver atom, a bismuth atom, an iron atom, a cobalt atom, a lanthanum atom, and a cerium atom. When b is 12, a, f, c, d, e, and x represent values satisfying the conditions of 1.2 ≦ a ≦ 1.8, 0.01 ≦ c ≦ 0.4, 0.4 ≦ d ≦ 0.6, 1.2 ≦ e ≦ 1.8, and 0.4 ≦ f ≦ 0.6, respectively. x represents a value determined by the oxidation state of each atom. When Y is two or more kinds of atoms, f represents the total ratio of the two or more kinds of atoms.

[0045] In the present embodiment, as the heteropolyacid represented by formula (I), from the viewpoint of improving the catalytic performance, it is preferable that Y is an arsenic atom or an antimony atom, a is 1.4 to 1.6, c is 0.05 to 0.35, d is 0.45 to 0.55, and e is 1.2 to 1.6.

[0046] In the present embodiment, for the partially neutralized salt of the heteropolyacid represented by formula (I), more specifically, it is more preferable that Y is an antimony atom and f is 0.45 to 0.55.

[0047] (3) [Step (3)] (A step of kneading a dried body containing the second heteropolyacid compound particles obtained by drying the second slurry and then extrusion-molding to obtain a molded body) (i) Drying treatment In step (3), first, the second slurry obtained in step (2) is dried. The drying treatment according to step (3) can be carried out by any conventionally known suitable drying method. Examples of the drying method include an evaporation to dryness method, a spray drying method using a spray dryer, a drum rotary drying method using a rotary kiln, a continuous flash airflow drying method using a flash jet dryer, a vacuum drying method using a vacuum drum dryer, and a method using a filtration drying apparatus.

[0048] In the present embodiment, the drying treatment according to step (3) is preferably performed by a spray drying method using any conventionally known and suitable spray dryer. The drying conditions may be appropriately set so that the water content in the aqueous slurry (E) is sufficiently reduced, and there is no particular limitation. The temperature during the drying treatment according to step (3) is preferably less than 300°C.

[0049] (ii) Kneading treatment and extrusion molding treatment Next, a kneading treatment for kneading the dried body obtained by the drying treatment is performed, and an extrusion molding treatment is performed using the kneaded body obtained by the kneading treatment to form a precursor of the catalyst for producing methacrylic acid. Further, in such an extrusion molding treatment, water, a molding aid, a pore-forming agent, etc. may be added to the dried body as necessary. Examples of such a molding aid include fibers such as ceramic fiber, glass fiber, and bio-soluble fiber, methyl cellulose, and ammonium nitrate. The ceramic fiber is preferably a bio-soluble fiber. In particular, ammonium nitrate preferably has not only a function as a molding aid but also a function as a pore-forming agent.

[0050] Specifically, first, to the dried product (precursor of the powdery catalyst for methacrylic acid production) obtained by the drying treatment as described above, fibers such as ceramic fibers and bio-soluble fibers are added as a forming aid as needed, and further water, ammonium nitrate, etc. are added and kneaded to obtain a kneaded product which is a paste-like mixture by a kneading treatment. The amount of the forming aid is not particularly limited. The amount of fibers such as ceramic fibers, glass fibers, and bio-soluble fibers as the forming aid is usually 1 part by mass or more and 10 parts by mass or less, preferably 2 parts by mass or more and 8 parts by mass or less, based on 100 parts by mass of the dried product. The amount of ammonium nitrate is usually 5 parts by mass or more and 30 parts by mass or less, preferably 7 parts by mass or more and 25 parts by mass or less, more preferably 9 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the dried product. The amount of water is usually 4 parts by mass or more and 20 parts by mass or less, preferably 5 parts by mass or more and 15 parts by mass or less, more preferably 6 parts by mass or more and 12 parts by mass or less, based on 100 parts by mass of the dried product.

[0051] Next, the kneaded product obtained by the kneading treatment is subjected to an extrusion molding treatment. Specifically, by extrusion molding, the kneaded product is formed into a pellet-shaped molded body having a desired shape (for example, cylindrical, spherical, ring-shaped, etc.) according to the usage mode of the catalyst for methacrylic acid production which is the finished product.

[0052] It is preferable to perform a temperature and humidity conditioning treatment on the molded body obtained by the extrusion molding treatment as described above before performing the firing treatment described later. The method of such a temperature and humidity conditioning treatment is not particularly limited.

[0053] As the temperature and humidity conditioning treatment, for example, it is preferable to adopt a method of exposing the obtained molded body in an atmosphere with a relative humidity of 10 to 60% at a temperature condition of 40 to 100 °C for about 0.5 to 10 hours. Such a temperature and humidity conditioning treatment may be performed, for example, in a temperature and humidity controlled tank, or may be performed by blowing a temperature and humidity controlled gas onto the molded body, and the specific treatment method is not particularly limited. Also, as the gas for performing such a temperature and humidity conditioning treatment, air is usually used, but an inert gas such as nitrogen gas may also be used.

[0054] The kneading process can be carried out under any suitable known conditions selected in consideration of the components and properties using any suitable known apparatus.

[0055] The kneading process and the extrusion molding process can be carried out by any suitable known kneading apparatus and extrusion molding apparatus. Examples of the extrusion apparatus that can be used include any suitable known Banbury mixer and kneader. Examples of the extrusion molding apparatus that can be used include any suitable known plunger extruder, single-screw extruder, co-rotating twin-screw extruder, and counter-rotating twin-screw extruder.

[0056] The configuration of the extrusion apparatus that can be used in the extrusion molding process is not particularly limited on the condition that the kneaded product obtained as described above can be extruded into a cylindrical shape. For example, extrusion molding into a cylindrical shape can be carried out by using an apparatus equipped with an extrusion die having a cylindrical through-hole. The extrusion speed in the extrusion molding process is not particularly limited. In carrying out the extrusion molding process, it is preferable to carry out the process with a constant extrusion speed.

[0057] In the method for producing the catalyst for methacrylic acid production according to the present embodiment, the efficiency of the extrusion molding process can be improved by adjusting the particle size of the heteropolyacid compound particles to the predetermined range already described by the "wet grinding process" already described.

[0058] Here, the "efficiency of the extrusion molding process" can be evaluated, for example, by the pressure difference (second extrusion pressure - first extrusion pressure) between the first extrusion pressure, which is the pressure when the kneaded product is introduced into the extrusion apparatus and the extrusion speed of the molded product extruded from the extrusion apparatus by the extrusion molding process is 0.0051 m / s (first extrusion speed), and the second extrusion pressure, which is the pressure when the extrusion speed of the molded product is 0.0308 m / s (second extrusion speed).

[0059] The measurement of the extrusion pressure can be carried out by using an extrusion die having a cylindrical through-hole and an extrusion device equipped with any conventionally known and suitable pressure sensor, and measuring the pressure with the pressure sensor while performing extrusion at a constant speed. Specific examples will be described below. However, the method for measuring the extrusion pressure is not limited to the specific examples described later.

[0060] For example, the measurement of the extrusion pressure can be carried out by putting a kneaded material that has been subjected to the kneading process described above into a cylindrical mold with an inner diameter of 40 mm, which is equipped with an extrusion die having a cylindrical through-hole with an inner diameter of 5.4 mm and a length of 10 mm and a pressure sensor, and measuring the first extrusion pressure and the second extrusion pressure to obtain the pressure difference.

[0061] The pressure sensor is not particularly limited as long as it can measure the pressure applied to the kneaded material. Specifically, for example, a small pressure sensor "PGM-E" manufactured by Kyowa Electronic Instruments Co., Ltd. can be used as the pressure sensor.

[0062] When measuring the extrusion pressure, the method for performing extrusion at a constant speed is not particularly limited. Such extrusion can be carried out, for example, by combining the extrusion die described above and a tensilon universal material testing machine, and setting the crosshead speed of the tensilon universal material testing machine to be constant to extrude the kneaded material, thereby performing extrusion at a constant speed.

[0063] Since it can be said that the smaller the pressure difference (the second extrusion pressure - the first extrusion pressure), the more stably the extrusion molding can be performed, it can be evaluated that the smaller this pressure difference, the more the efficiency of the extrusion molding process, and thus the manufacturing efficiency of the catalyst for methacrylic acid production can be improved.

[0064] In the present embodiment, from the viewpoint of improving the efficiency of the extrusion molding process and the manufacturing efficiency of the catalyst for methacrylic acid production, the pressure difference (the second extrusion pressure - the first extrusion pressure) is preferably 1.6 MPa or less, and more preferably 1.3 MPa or less.

[0065] (iii) Pre-firing treatment From the viewpoint of removing the ammonium nitrate contained and changing the structure of the heteropolyacid compound, prior to the firing described below, as a pre-firing, it is preferable to perform a treatment (pre-firing treatment) of holding at a temperature of about 180 to 300 °C in an atmosphere of an oxidizing gas or a non-oxidizing gas.

[0066] The pre-firing treatment can be a treatment of firing a molded body, which is a precursor of the catalyst for methacrylic acid production obtained by the kneading treatment and the extrusion molding treatment already described, in a firing furnace provided in a firing apparatus having any conventionally known suitable configuration.

[0067] (4) [Step (4)] A step of firing the molded body to obtain a catalyst for methacrylic acid production The firing treatment in the production method of the present embodiment is a step of firing the molded body. The method of firing is not particularly limited, and a method usually used in this field can be appropriately adopted. Such a firing step may be performed, for example, in an atmosphere of an oxidizing gas such as oxygen gas or in an atmosphere of a non-oxidizing gas such as nitrogen gas, and the firing temperature is preferably 300 °C or higher. Further, when the pre-firing step already described is performed prior to such a firing step, it is preferable to perform the firing step at a temperature higher than the temperature adopted in the pre-firing step already described.

[0068] In step (4), from the viewpoint of making the catalytic activity higher, it is preferable to adopt a method of performing a multi-stage firing treatment in an atmosphere of an oxidizing gas or a non-oxidizing gas. It is more preferable to include a first firing treatment of firing at 360 °C to 410 °C in an oxidizing gas atmosphere, a second firing treatment of firing at 420 °C to 500 °C in a non-oxidizing gas atmosphere, and a cooling treatment. This will be specifically described below. The firing treatment is not limited to the specific examples described later.

[0069] (First firing treatment) The gas (mixed gas) subjected to the first firing treatment may contain an oxidizing gas (outside air (air), oxygen gas, etc.), a non-oxidizing gas (inert gas (nitrogen gas, argon gas, helium gas, neon gas, etc.), a reducing gas (carbon dioxide, hydrogen, ammonia, etc.). Further, moisture may be present in the oxidizing gas as necessary. In this case, the concentration of the moisture that can be contained is usually 10% by volume or less. Among these, the mixed gas preferably contains nitrogen gas, air, argon gas, helium gas, and carbon dioxide gas, and more preferably contains nitrogen gas and air.

[0070] The temperature in the first firing treatment is preferably 360°C to 410°C, and more preferably 380°C to 410°C. If the temperature in the first firing treatment is set to such a temperature, the catalytic activity and catalytic life of the catalyst for methacrylic acid production to be produced can be effectively improved.

[0071] The firing time in the first firing treatment is preferably 1 to 20 hours, and more preferably 1 to 5 hours. If the first firing treatment is carried out for 1 to 20 hours, firing can be sufficiently carried out regardless of the composition of the molded body to be treated.

[0072] (Second firing treatment) The second firing treatment is preferably a treatment in which the fired product obtained by the first firing treatment is further fired in the firing furnace in which the pre-firing treatment has been performed. Further, the second firing treatment may be performed on the fired product obtained by the first firing treatment in a firing furnace different from the firing furnace in which the first firing treatment was performed.

[0073] Examples of the gas (mixed gas) that can be used in the second firing process include non-oxidizing gases (inert gases (such as nitrogen gas, argon gas, helium gas, neon gas, etc.), reducing gases (such as carbon dioxide gas, hydrogen gas, ammonia gas, etc.)). Among these non-oxidizing gases, it is preferable to use nitrogen gas, argon gas, helium gas, and carbon dioxide gas, and it is more preferable to use nitrogen gas. The non-oxidizing gas may be used alone or in combination of two or more. Also, as the non-oxidizing gas used in the second firing process, it is preferable to use a dry non-oxidizing gas that contains as little moisture as possible.

[0074] The second firing process is preferably carried out at a temperature of 420°C to 500°C, and more preferably at a temperature of 430°C to 440°C.

[0075] The firing time in the second firing process is preferably 1 to 20 hours, and more preferably 1 to 5 hours.

[0076] (Cooling process) The cooling process is an optional step for cooling the fired product obtained in the second firing process to a predetermined temperature. Specifically, the fired product obtained in the second firing process may be cooled, for example, in the non-oxidizing gas atmosphere already described, preferably at a temperature of 280°C or lower, and more preferably at a temperature of 90°C or lower.

[0077] Non-oxidizing gases that can be used in the cooling treatment include the non-oxidizing gases (inert gases (nitrogen gas, argon gas, helium gas, neon gas), reducing gases (carbon dioxide gas, hydrogen gas, ammonia gas)) already described. Among these non-oxidizing gases, nitrogen gas, argon gas, helium gas, and carbon dioxide are preferred, and nitrogen gas is more preferred. From the perspective of improving workability, it is preferable to use the same non-oxidizing gas as that used in the second firing treatment, that is, to use the non-oxidizing gas used in the second firing treatment as it is, for the non-oxidizing gas used in the cooling step. The non-oxidizing gas may be used alone or in combination of two or more. Also, it is preferable to use a dry non-oxidizing gas that contains as little moisture as possible for the non-oxidizing gas used in the cooling treatment.

[0078] From the perspective of effectively improving the catalytic activity and catalyst life, the cooling treatment is preferably carried out at a temperature of 280°C or lower, and more preferably at 90°C or lower.

[0079] According to the "method for producing a catalyst for methacrylic acid production" according to this embodiment including the above steps (treatments), the particle size (median diameter, and further the 10% particle size, 90% particle size) of the heteropolyacid compound particles is adjusted to the predetermined range already described by wet grinding treatment, and the ratio of the heteropolyacid compound particles having a particle size of 10 μm or less is adjusted to the predetermined range. Therefore, the extrusion pressure in the extrusion molding treatment can be further reduced, and the efficiency of the extrusion molding treatment can be further improved. As a result, the production efficiency of the catalyst for methacrylic acid production can be further improved, and the production cost of the catalyst for methacrylic acid production can be further reduced.

[0080] 2. Production of Methacrylic Acid The catalyst for methacrylic acid production that can be produced by the production method already described in this embodiment can be suitably applied to the "method for producing methacrylic acid" in which at least one compound (raw material compound) selected from the group consisting of methacrolein, isobutyraldehyde, isobutane, and isobutyric acid is brought into contact under predetermined conditions to be subjected to a gas-phase catalytic oxidation reaction to obtain methacrylic acid.

[0081] More specifically, the catalyst for producing methacrylic acid obtainable by the production method of the present embodiment is particularly preferably used as a catalyst having catalytic activity in the second-stage reaction in the production method of methacrylic acid carried out by the C4 straight acid method, that is, the reaction for converting methacrolein into methacrylic acid.

[0082] Here, the production of methacrylic acid can be carried out by a conventionally known and arbitrarily suitable production method in which the catalyst for producing methacrylic acid of the present embodiment is filled in a fixed-bed multitubular reactor, and a raw material compound and a mixed gas are supplied to this reactor. Further, instead of the fixed bed, a reactor in the form of a fluidized bed or a moving bed can also be employed.

[0083] When using methacrolein as a raw material compound, the reaction can preferably be carried out under the following conditions. The space velocity can be obtained by dividing the supply amount (L / h) of the raw materials (raw material compound and mixed gas) per hour passing through the reactor by the volume (L) of the catalyst for producing methacrylic acid in the reactor. Conditions: Concentration of methacrolein in the raw material: 1 to 10% by volume Concentration of water vapor in the raw material: 1 to 30% by volume Molar ratio of methacrolein to oxygen: 1 / 1 to 1 / 5 (methacrolein / oxygen) Space velocity: 500 to 5000 h -1 (Based on standard conditions) Reaction temperature: 250 to 350 °C Reaction pressure: 0.1 to 0.3 MPa

[0084] When using isobutane as a raw material compound, the reaction can preferably be carried out under the following conditions. Conditions: Concentration of isobutane in the raw material: 1 to 85% by volume Concentration of water vapor in the raw material: 3 to 30% by volume Molar ratio of isobutane to oxygen: 1 / 0.05 to 1 / 4 (isobutane / oxygen) Space velocity: 400 to 5000 h-1 (Standard state reference) Reaction temperature: 250 - 400 °C Reaction pressure: 0.1 - 1 MPa

[0085] When isobutyraldehyde and isobutyric acid are used as raw material compounds, it can be carried out under the same conditions as when methacrolein is used as the raw material compound. Also, none of the above raw material compounds need to be highly purified products. For example, in the case of methacrolein as a raw material compound, methacrolein obtained by the gas-phase catalytic oxidation reaction of isobutylene and tert-butyl alcohol may be used without purification.

[0086] The evaluation of the catalyst for methacrylic acid production produced by the production method of the catalyst for methacrylic acid production of this embodiment, specifically, the methacrolein conversion rate (%), methacrylic acid selectivity (%), and methacrylic acid yield (%) when using methacrolein as a raw material compound, for example, can be calculated based on the following formulas. Formula: Methacrolein conversion rate (%) = [moles of reacted methacrolein ÷ moles of supplied methacrolein] × 100 Methacrylic acid selectivity (%) = [moles of produced methacrylic acid ÷ moles of reacted methacrolein] × 100 Methacrylic acid yield (%) = [methacrolein conversion rate (%) × methacrylic acid selectivity (%)] ÷ 100

Examples

[0087] Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited to the examples described below.

[0088] Preparation Example 1 〔Preparation of aqueous slurry E〕 Dissolve 39.20 g of 67.5 mass% nitric acid, 27.43 g of 75 mass% orthophosphoric acid, and 38.19 g of cesium nitrate [CsNO3] in 224 g of ion-exchanged water to obtain an aqueous mixture A.

[0089] To 330 g of ion-exchanged water heated to 40°C, 297 g of hexaammonium heptamolybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O] was dissolved, and then 8.19 g of ammonium metavanadate [NH4VO3] was suspended to obtain an aqueous mixture B.

[0090] Using a water bath, while maintaining the temperature of each of the aqueous mixture A and the aqueous mixture B at 40°C, the aqueous mixture A was added dropwise to the aqueous mixture B with stirring, and then stirred in a sealed container at 120°C for 5 hours to obtain an aqueous slurry C. The molar ratio of phosphorus to molybdenum (phosphorus / molybdenum), the molar ratio of vanadium to molybdenum (vanadium / molybdenum), and the molar ratio of cesium to molybdenum (cesium / molybdenum) contained in the aqueous slurry C are 1.5 / 12, 0.5 / 12, and 1.4 / 12, respectively.

[0091] 10.2 g of antimony trioxide [Sb2O3] and 33.59 g of a 30.6 mass% aqueous solution of copper(II) nitrate trihydrate [Cu(NO3)2·3H2O] were suspended in 100 g of ion-exchanged water to prepare an aqueous mixture D.

[0092] The obtained aqueous mixture D was heated to 120°C and added to the aqueous slurry C in a sealed container while maintaining the temperature at 120°C and stirring, and then stirred at 120°C for an additional 5 hours to obtain an aqueous slurry E, which is a first slurry containing first heteropolyacid compound particles a containing a heteropolyacid compound. The molar ratio of phosphorus to molybdenum (phosphorus / molybdenum), the molar ratio of vanadium to molybdenum (vanadium / molybdenum), the molar ratio of cesium to molybdenum (cesium / molybdenum), the molar ratio of copper to molybdenum (copper / molybdenum), and the molar ratio of antimony to molybdenum (antimony / molybdenum) contained in the first heteropolyacid compound particles a in the aqueous slurry C are 1.5 / 12, 0.5 / 12, 1.4 / 12, 0.3 / 12, and 0.5 / 12, respectively.

[0093] Regarding the obtained aqueous slurry E, the particle size distribution of the first heteropolyacid compound particles a contained in the aqueous slurry E was measured using a laser diffraction / scattering particle size distribution measuring device [LA-920 manufactured by Horiba, Ltd.]. As a result, the median diameter (50% particle diameter: D50) was 10.2 μm, the ratio of heteropolyacid compound particles having a particle diameter of 10 μm or less was 49%, the value of the 10% particle diameter (D10) was 2.6 μm, and the value of the 90% particle diameter (D90) was 29.9 μm.

[0094] Example 1 [Preparation of Aqueous Slurry F1] The aqueous slurry E containing the first heteropolyacid compound particles a was subjected to wet pulverization treatment at 30 °C for 1 minute using a homomixer (ULTRA-DISPERSER LK-41) to obtain an aqueous slurry F1, which is a second slurry containing the second heteropolyacid compound particles b. The median diameter of the second heteropolyacid compound particles b contained in the obtained aqueous slurry F1 was 4.8 μm, the ratio of heteropolyacid compound particles having a particle diameter of 10 μm or less was 90%, the value of D10 was 1.0 μm, and the value of D90 was 10.1 μm.

[0095] [Preparation of Heteropolyacid Compound Particles (1)] The obtained aqueous slurry F1 was heated to 135 °C in the air, and the water was evaporated and dried to obtain heteropolyacid compound particles (1).

[0096] [Preparation of Kneaded Body] To 100 parts by mass of the heteropolyacid compound particles (1), 4 parts by mass of ceramic fiber RCF-400SL manufactured by Isolite Industries Co., Ltd., 15.1 parts by mass of ammonium nitrate, and 9.7 parts by mass of ion-exchanged water were added and kneaded to prepare a kneaded body.

[0097] [Measurement of Extrusion Pressure] The kneaded mixture prepared was placed in a cylindrical mold with an inner diameter of 40 mm, equipped with an extrusion die having a cylindrical through-hole with an inner diameter of 5.4 mm and a length of 10 mm and a pressure sensor (Kyowa Electronic Instruments Co., Ltd. PGM-100KE), and the extrusion pressure was measured while extruding at a constant speed using a tensile universal material testing machine. Here, when the extrusion speed of the molded body extruded from the extrusion die was 0.0051 m / s (the first extrusion speed), the first extrusion pressure was 1.9 MPa, and when the extrusion speed of the molded body was 0.0308 m / s (the second extrusion speed), the second extrusion pressure was 2.8 MPa. The pressure difference between these (the second extrusion pressure - the first extrusion pressure) was 0.9 MPa. The results are shown in Table 1 below.

[0098] Production Example 1 〔Formation of Molded Body (Extrusion Molding)〕 The kneaded mixture containing the heteropolyacid compound particles (1) obtained in Example 1 above was placed in a cylindrical mold with an inner diameter of 40 mm, equipped with an extrusion die having a cylindrical through-hole with an inner diameter of 5.4 mm and a length of 10 mm, and the kneaded mixture was extruded so that the extrusion speed of the molded body became 0.0051 m / s, thereby obtaining a cylindrical molded body.

[0099] 〔Production of Catalyst for Methacrylic Acid Production〕 After performing a temperature and humidity conditioning treatment of drying the obtained molded body at a temperature of 90°C and a relative humidity of 30% for 3 hours, a pre-firing treatment of holding at 220°C for 22 hours in an air stream and then holding at 250°C for 1 hour was performed. Subsequently, a first firing treatment of holding at 390°C for 4 hours in an air stream was performed, and then a second firing treatment of holding at 435°C for 4 hours in a nitrogen stream was performed, thereby obtaining a pellet-shaped catalyst for methacrylic acid production containing the heteropolyacid compound particles (1).

[0100] 〔Activity Test of Catalyst for Methacrylic Acid Production〕 4.5 g of the obtained catalyst for methacrylic acid production was charged into a glass microreactor with an inner diameter of 16 mm, and the furnace temperature (the temperature of the furnace for heating the microreactor) was raised to 355 °C. Subsequently, a raw material gas (composition: 4 vol% methacrolein, 12 vol% molecular oxygen, 17 vol% steam, 67 vol% nitrogen) prepared by mixing methacrolein, air, steam, and nitrogen gas was supplied to the microreactor at a space velocity of 670 h -1 and reacted for 1 hour to forcibly deteriorate the catalyst for methacrylic acid production, thereby obtaining a deteriorated catalyst. Subsequently, the furnace temperature was set to 280 °C, and the raw material gas with the composition described above was supplied to the obtained deteriorated catalyst at a space velocity of 670 h -1 and reacted. The reaction gas (gas after reaction) derived 1 hour after the start of the reaction at a furnace temperature of 280 °C was sampled and analyzed by gas chromatography, and based on the following formula, the methacrolein conversion rate (%), methacrylic acid selectivity (%), and methacrylic acid yield (%) were determined. As a result, the methacrolein conversion rate was 76.4%, the methacrylic acid selectivity was 78.7%, and the methacrylic acid yield was 60.1%.

[0101] Methacrolein conversion rate (%) = [number of moles of reacted methacrolein ÷ number of moles of supplied methacrolein] × 100 Methacrylic acid selectivity (%) = [number of moles of produced methacrylic acid ÷ number of moles of reacted methacrolein] × 100 Methacrylic acid yield (%) = [methacrolein conversion rate (%) × methacrylic acid selectivity (%)] ÷ 100

[0102] Example 2 [Preparation of aqueous slurry F2] The aqueous slurry F1 according to Preparation Example 1 described above and the aqueous slurry E were mixed at a ratio of 3:1 (volume ratio) to obtain an aqueous slurry F2. The median diameter of the heteropolyacid compound particles contained in the aqueous slurry F2 was 6.0 μm, the ratio of the heteropolyacid compound particles with a particle diameter of 10 μm or less was 80%, the value of D10 was 1.2 μm, and the value of D90 was 12.8 μm.

[0103] [Preparation of Heteropoly Acid Compound Particles (2)] The obtained aqueous slurry F2 was heated to 135°C in the air to evaporate and dry the water, thereby obtaining heteropoly acid compound particles (2).

[0104] [Preparation of Kneaded Body] A kneaded body was prepared in the same manner as in [Preparation of Kneaded Body] of Example 1, except that heteropoly acid compound particles (2) were used instead of the heteropoly acid compound particles (1) according to Example 1 already described.

[0105] [Measurement of Extrusion Pressure] Using the obtained kneaded body, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 already described. Here, when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed), the first extrusion pressure was 1.4 MPa, and when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed), the second extrusion pressure was 2.5 MPa, and the pressure difference (second extrusion pressure - first extrusion pressure) was 1.1 MPa.

[0106] Example 3 [Preparation of Aqueous Slurry F3] The aqueous slurry F1 according to Preparation Example 1 already described and the aqueous slurry E were mixed at a ratio of 1:1 to obtain an aqueous slurry F3. The median diameter of the heteropoly acid compound particles contained in the aqueous slurry F3 was 7.2 μm, the ratio of the heteropoly acid compound particles having a particle diameter of 10 μm or less was 70%, the value of D10 was 1.5 μm, and the value of D90 was 15.2 μm.

[0107] [Preparation of Heteropoly Acid Compound Particles (3)] The obtained aqueous slurry F3 was heated to 135°C in the air to evaporate and dry the water, thereby obtaining heteropoly acid compound particles (3).

[0108] [Preparation of Kneaded Body] A kneaded body was prepared in the same manner as in [Preparation of Kneaded Body] of Example 1, except that the heteropolyacid compound particles (3) were used instead of the heteropolyacid compound particles (1) according to Preparation Example 1 already described.

[0109] [Measurement of Extrusion Pressure] Using the obtained kneaded body, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 already described. Here, when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed), the first extrusion pressure was 2.0 MPa, and when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed), the second extrusion pressure was 3.4 MPa, and the pressure difference (second extrusion pressure - first extrusion pressure) was 1.4 MPa.

[0110] Example 4 [Preparation of Aqueous Slurry F4] The aqueous slurry E according to Preparation Example 1 already described was placed in an alumina container together with 2700 g of alumina balls having a diameter of 15 mm, and pulverized for 16 hours by continuously rotating at a speed of 53 revolutions per minute using a rotary ball mill to obtain an aqueous slurry F4. The median diameter of the heteropolyacid compound particles contained in the aqueous slurry F4 was 1.3 μm, the ratio of the heteropolyacid compound particles having a particle diameter of 10 μm or less was 100%, the value of D10 was 0.6 μm, and the value of D90 was 2.6 μm.

[0111] [Preparation of Heteropolyacid Compound Particles (4)] The obtained aqueous slurry F4 was heated to 135 °C in the air to evaporate and dry the water, thereby obtaining heteropolyacid compound particles (4).

[0112] [Preparation of Kneaded Body] A kneaded body was prepared in the same manner as in [Preparation of Kneaded Body] of Example 1, except that the heteropolyacid compound particles (4) were used instead of the heteropolyacid compound particles (1) according to Preparation Example 1 already described.

[0113] [Measurement of Extrusion Pressure] Using the obtained kneaded material, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 already described. Here, when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed), the first extrusion pressure was 2.0 MPa, and when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed), the second extrusion pressure was 3.0 MPa, and the pressure difference between these (second extrusion pressure - first extrusion pressure) was 1.0 MPa. The results are shown in Table 1 below.

[0114] Comparative Example 1 [Preparation of Heteropoly Acid Compound Particles (5)] The aqueous slurry E according to Preparation Example 1 already described was heated to 135 °C in the atmosphere to evaporate and dry the water, thereby obtaining heteropoly acid compound particles (5).

[0115] [Preparation of Kneaded Material] A kneaded material was prepared in the same manner as in [Preparation of Kneaded Material] of Example 1, except that heteropoly acid compound particles (5) were used instead of the heteropoly acid compound particles (1) according to Preparation Example 1 already described.

[0116] [Measurement of Extrusion Pressure] Using the obtained kneaded material, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 already described. Here, when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed), the first extrusion pressure was 2.7 MPa, and when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed), the second extrusion pressure was 5.5 MPa, and the pressure difference between these (second extrusion pressure - first extrusion pressure) was 2.8 MPa. The results are shown in Table 1 below.

[0117] Comparative Example 2 [Preparation of Aqueous Slurry F5] The aqueous slurry F1 according to Preparation Example 1 described above and the aqueous slurry E were mixed at a ratio of 1:3 to obtain an aqueous slurry F5. The median diameter of the heteropolyacid compound particles contained in the aqueous slurry F5 was 8.7 μm, the ratio of the heteropolyacid compound particles having a particle diameter of 10 μm or less was 59%, the value of D10 was 1.9 μm, and the value of D90 was 19.9 μm.

[0118] [Preparation of Heteropolyacid Compound Particles (6)] The obtained aqueous slurry F5 was heated to 135° C. in the air to evaporate and dry the water, thereby obtaining heteropolyacid compound particles (6).

[0119] [Preparation of Kneaded Body] A kneaded body was prepared in the same manner as in [Preparation of Kneaded Body] of Example 1, except that the heteropolyacid compound particles (6) were used instead of the heteropolyacid compound (1) according to Preparation Example 1 described above.

[0120] [Measurement of Extrusion Pressure] Using the obtained kneaded body, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1. Here, the first extrusion pressure when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed) was 1.7 MPa, and the second extrusion pressure when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed) was 3.5 MPa, and the pressure difference (MPa) between these pressures was 1.8 MPa. The results are shown in Table 1 below.

[0121] [Table 1]

[0122] According to Examples 1 to 4 in which the particle diameter (median diameter, 10% particle diameter, 90% particle diameter) of the heteropolyacid compound particles was adjusted to a predetermined range by wet pulverization treatment and the ratio of the particles having a particle diameter of 10 μm or less was 65% or more, the pressure difference between the first extrusion pressure and the second extrusion pressure could be significantly reduced to 1.4 or less, specifically in the range of 0.9 to 1.4, as compared with Comparative Examples 1 and 2.

Claims

1. A method for producing a catalyst for methacrylic acid production, comprising the following steps (1) to (4) and containing heteropolyacid compound particles. [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium [Step (2)] By subjecting the first slurry to wet grinding treatment and performing laser diffraction particle size distribution measurement and converting on a volume basis, when the median diameter (D50) is 0.50 to 8.0 μm and the particle size is 10 μm or less, a step of preparing a second slurry containing second heteropolyacid compound particles with a proportion of 65% or more [Step (3)] A step of kneading a dried body containing the second heteropolyacid compound particles obtained by drying the second slurry and performing extrusion molding to obtain a molded body [Step (4)] A step of firing the molded body to obtain a catalyst for methacrylic acid production

2. When performing laser diffraction particle size distribution measurement and converting on a volume basis, the 10% particle diameter (D10) of the second heteropolyacid compound particles contained in the second slurry is 0.30 μm or more and 1.8 μm or less. The method for producing a catalyst for methacrylic acid production according to Claim 1.

3. When performing laser diffraction particle size distribution measurement and converting on a volume basis, the 90% particle diameter (D90) of the second heteropolyacid compound particles contained in the second slurry is 2.0 μm or more and 17 μm or less. The method for producing a catalyst for methacrylic acid production according to Claim 1 or 2.

4. The method for producing a catalyst for methacrylic acid production according to Claim 1 or 2, wherein the wet grinding treatment is performed at a temperature of 0°C or higher and 80°C or lower.

5. The method for producing a catalyst for methacrylic acid production according to Claim 1 or 2, wherein the step (4) is a step of firing the molded body at 360°C to 410°C in an oxidizing gas atmosphere and then firing at 420°C to 500°C in a non-oxidizing gas atmosphere.

6. The heteropolyacid compound contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles is represented by the following formula (I): P ａ Mo ｂ Cu ｃ V ｄ Cs ｅ Y ｆ O ｘ (I) (In formula (I), P represents a phosphorus atom, Mo represents a molybdenum atom, Cu represents a copper atom, V represents a vanadium atom, Cs represents a cesium atom, O represents an oxygen atom, Y represents at least one atom selected from the group consisting of an arsenic atom, an antimony atom, a boron atom, a silver atom, a bismuth atom, an iron atom, a cobalt atom, a lanthanum atom, and a cerium atom, a to f represent values that satisfy the conditions of 1.2 ≤ a ≤ 1.8, 0.01 ≤ c ≤ 0.4, 0.4 ≤ d ≤ 0.6, 1.2 ≤ e ≤ 1.8, and 0.4 ≤ f ≤ 0.6 when b is 12. x represents a value determined by the oxidation state of each atom. f represents the total ratio of the two or more atoms when Y is two or more atoms. The method for producing a catalyst for methacrylic acid production according to claim 1 or 2, which is a partially neutralized salt of a heteropolyacid represented by

7. A method for producing methacrylic acid, comprising a step of subjecting a catalyst for methacrylic acid production produced by the method for producing a catalyst for methacrylic acid production according to claim 1 or 2 to a gas-phase catalytic oxidation reaction by contacting it with at least one compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane, and isobutyric acid to obtain methacrylic acid.

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