Method for producing catalyst for methacrylic acid production

Abstract

The present invention relates to a method for producing a catalyst for methacrylic acid production, which comprises the following steps. Step (1): a step for preparing a first slurry containing first heteropolyacid compound particles, the first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium; step (2): a step for preparing a second slurry containing second heteropolyacid compound particles by wet grinding the first slurry, the second heteropolyacid compound particles having a median diameter of 0.50 [mu] m to 8.0 [mu] m when converted on a volume basis by laser diffraction particle size distribution measurement; the ratio of heteropolyacid compound particles having a particle diameter of 10 [mu] m or less is 65% or more; step (3): a step in which the second slurry is dried to obtain a dried body containing second heteropolyacid compound particles, and the dried body is kneaded and extrusion-molded to obtain a molded body; step (4): a step for obtaining a catalyst for methacrylic acid production by calcining the molded body.

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 in the gas-phase catalytic oxidation reaction of methacrolein or the like to produce methacrylic acid, it is known that heteropolyacids containing phosphorus and molybdenum and their salts are effective. Such a catalyst is usually produced by drying an aqueous mixture of a catalyst-containing raw material and then calcining it (see Patent Document 1).

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

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 7-185354 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, according to the conventional method for producing a catalyst for producing methacrylic acid represented by the above Patent Document 1, the production efficiency of the catalyst for producing methacrylic acid may sometimes be reduced due to a prescribed process.

[0009] Therefore, there is a demand for a method for producing a catalyst for producing methacrylic acid that can further improve the production efficiency and further reduce the production cost.

[0010] Means for Solving the Problems

[0011] The present inventors conducted intensive studies to solve the above problems, and as a result, found that by performing a prescribed process in the method for producing a catalyst for producing methacrylic acid, the above problems can be solved, and thus the present invention was completed.

[0012] That is, the present invention provides the following [1] to [7].

[0013] [1] A method for producing a catalyst for producing methacrylic acid, wherein the catalyst for producing methacrylic acid contains heteropolyacid compound particles, and the production method includes the following steps (1) to (4):

[0014] [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles, wherein the first heteropolyacid compound particles contain at least molybdenum, phosphorus, copper, vanadium, and cesium;

[0015] [Step (2)] A step of preparing a second slurry containing second heteropolyacid compound particles by subjecting the first slurry to wet grinding treatment. When performing laser diffraction particle size distribution measurement and converting on a volume basis, the median particle size (D50) of the second heteropolyacid compound particles is 0.50 μm to 8.0 μm, and the ratio of heteropolyacid compound particles having a particle size of 10 μm or less is 65% or more;

[0016] [Step (3)] A step of drying the second slurry to obtain a dried body containing the second heteropolyacid compound particles, kneading the dried body, and performing extrusion molding to obtain a molded body;

[0017] [Step (4)] A step of calcining the molded body to obtain a catalyst for methacrylic acid production.

[0018] [2] The method for producing a catalyst for methacrylic acid production according to [1], wherein when performing laser diffraction particle size distribution measurement and converting on a volume basis, the 10% particle size (D10) of the second heteropolyacid compound particles contained in the second slurry is 0.30 μm or more and 1.8 μm or less.

[0019] [3] The method for producing a catalyst for methacrylic acid production according to [1] or [2], wherein when performing laser diffraction particle size distribution measurement and converting on a volume basis, the 90% particle size (D90) of the second heteropolyacid compound particles contained in the second slurry is 2.0 μm or more and 17 μm or less.

[0020] [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.

[0021] [5] The method for producing a catalyst for methacrylic acid production according to any one of [1] to [4], wherein the step (4) is the following step: calcining the molded body at 360 °C to 410 °C in an oxidizing gas atmosphere, and then calcining at 420 °C to 500 °C in a non-oxidizing gas atmosphere.

[0022] [6] The method for producing a catalyst for methacrylic acid production according to any one of [1] to [5], wherein the heteropolyacid compound contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles is a partial neutralization salt of a heteropolyacid represented by the following formula (I).

[0023] P a Mo b Cu c V d Cs e Y f O x (I)

[0024] (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,

[0025] 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,

[0026] When b is set to 12, a to f 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, 0.4 ≤ f ≤ 0.6, x represents a value determined by the oxidation state of each atom, and when Y is two or more atoms, f represents the total ratio of the two or more atoms.)

[0027] [7] A method for producing methacrylic acid, wherein the method for producing methacrylic acid includes the following step: subjecting at least one compound selected from the group consisting of methacrolein, isobutyraldehyde, isobutane, and isobutyric acid to a gas-phase catalytic oxidation reaction by contacting it with 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]], thereby obtaining methacrylic acid.

[0028] Advantages of the Invention

[0029] 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. Detailed Embodiments

[0030] Hereinafter, the embodiments of the present invention will be specifically described. The present invention is not limited to the specific embodiments shown below.

[0031] 1. Method for Producing Catalyst for Methacrylic Acid Production

[0032] The manufacturing method of the catalyst for methacrylic acid production in this embodiment (hereinafter sometimes simply referred to as "manufacturing method") is a manufacturing method of a catalyst for methacrylic acid production containing heteropolyacid compound particles, which includes the following steps (1) to (4).

[0033] [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles, wherein the first heteropolyacid compound particles contain at least molybdenum, phosphorus, copper, vanadium, and cesium;

[0034] [Step (2)] A step of preparing a second slurry containing second heteropolyacid compound particles by subjecting the first slurry to wet pulverization treatment. When performing laser diffraction particle size distribution measurement and converting on a volume basis, the median particle diameter (D50) of the second heteropolyacid compound particles is 0.50 μm to 8.0 μm, and the ratio of heteropolyacid compound particles having a particle diameter of 10 μm or less is 65% or more;

[0035] [Step (3)] A step of drying the second slurry to obtain a dried body containing the second heteropolyacid compound particles, kneading the dried body, and performing extrusion molding to obtain a molded body;

[0036] [Step (4)] A step of calcining the molded body to obtain a catalyst for methacrylic acid production.

[0037] Hereinafter, the above steps (1) to (4) of the manufacturing method of the catalyst for methacrylic acid production in this embodiment will be specifically described.

[0038] (1) [Step (1)] (A step of preparing a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium)

[0039] Step (1) is a step of preparing a first slurry containing first heteropolyacid compound particles.

[0040] The first slurry prepared in step (1) of the manufacturing method in this embodiment contains first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium.

[0041] In step (1), first, a mixture of compounds containing elements 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.

[0042] Examples of the raw material compounds include: oxyacids, oxygen-containing salts, oxides, nitrates, carbonates, bicarbonates, hydroxides, and halides containing at least molybdenum, phosphorus, copper, vanadium, cesium, and other allowed elements (details will be described later).

[0043] In the present embodiment, examples of the compound containing molybdenum as an element include molybdic acid, molybdates (ammonium heptamolybdate tetrahydrate), molybdenum oxide, and molybdenum chloride. Examples of the compound containing phosphorus as an element include phosphoric acid (orthophosphoric acid), phosphates. Examples of the compound containing copper as an element include cuprous oxide, copper oxide, copper peroxide, copper nitrate, basic copper carbonate, copper hydroxide, and copper halides. Examples of the compound containing vanadium as an element include vanadic acid, vanadates (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 halides.

[0044] In the present embodiment, examples of the compound containing "other elements" include oxides, nitrates, carbonates, bicarbonates, hydroxides, oxyacids, oxyacid salts, and halides.

[0045] In the present embodiment, in the case of "halides", from the viewpoint of corrosion, chlorides, bromides, and iodides are preferred, and more specifically, cesium chloride, cesium bromide, and cesium iodide are preferred.

[0046] In step (1), a first slurry for manufacturing a catalyst for manufacturing methacrylic acid is prepared using a mixture of the above raw material compounds.

[0047] Specifically, an aqueous solution is prepared by mixing the raw material compound with water (e.g., ion-exchanged water) to dissolve it, or a liquid in which the raw material compounds are mixed and suspended is prepared in the form of a mixture, and then it is aged under any suitable temperature and time conditions known in the past, thereby obtaining a first slurry containing first heteropolyacid compound particles containing at least molybdenum, phosphorus, copper, vanadium, and cesium.

[0048] The aging temperature in step (1) is not particularly limited. The aging temperature in step (1) is generally greater than or equal to 30°C and less than 200°C, preferably greater than or equal to 100°C and less than 140°C.

[0049] In step (1), when preparing an aqueous solution, a mixed solution, or a suspension as a mixture for obtaining the first slurry, it is preferable to further add at least one selected from the group consisting of ammonia and ammonium salts, thereby preparing an aqueous solution, a mixed solution, or a suspension containing ammonia and ammonium salts.

[0050] In addition, in step (1), when preparing an aqueous solution, a mixed solution, or a suspension as a mixture for obtaining the first slurry, an ammonium compound that is at least one of the raw material compounds containing at least molybdenum, phosphorus, copper, vanadium, and cesium can be used instead of adding at least one selected from the group consisting of ammonia and ammonium salts. If an ammonium compound is used in this way, for example, a first slurry containing first heteropolyacid compound particles containing a non-Keggin type heteropolyacid salt can be obtained.

[0051] Here, when performing laser diffraction particle size distribution measurement and converting based on volume, the median particle size (D50) of the first heteropolyacid compound particles that can be obtained through step (1) is preferably 5 μm or more and 200 μm or less, more preferably 8 μm or more and 150 μm or less.

[0052] Regarding the particle size of the first heteropolyacid compound particles that can be obtained through step (1), when performing laser diffraction particle size distribution measurement and converting based on volume, 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.

[0053] Regarding the particle size of the first heteropolyacid compound particles that can be obtained through step (1), when performing laser diffraction particle size distribution measurement and converting based on volume, 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.

[0054] (2) [Step (2)] (A step of preparing a second slurry containing second heteropolyacid compound particles by subjecting the first slurry to wet pulverization treatment. When performing laser diffraction particle size distribution measurement and converting based on volume, the median particle size (D50) of the second heteropolyacid compound particles is 0.50 μm to 8.0 μm, and the ratio of heteropolyacid compound particles having a particle size of 10 μm or less is 65% or more)

[0055] In step (2), the first slurry prepared through step (1) is subjected to wet pulverization treatment.

[0056] Specifically, for the first heteropolyacid compound particles contained in the first slurry, a second slurry containing second heteropolyacid compound particles is obtained by wet pulverization treatment. When performing laser diffraction particle size distribution measurement and converting based on volume, the median particle size (D50) of the second heteropolyacid compound particles is 0.50 μm to 8.0 μm, and the ratio of heteropolyacid compound particles having a particle size of 10 μm or less is 65% or more.

[0057] Here, as the wet pulverization treatment, any suitable treatment known in the past that includes pulverization treatment and dispersion treatment can be used. Specifically, as the wet pulverization treatment, for example, a homogenizer (e.g., ULTRA-DISPERSER LK-41), a ball mill, a bead mill, and a DYNO mill can be used for implementation.

[0058] Regarding the conditions of the wet pulverization treatment, for example, in the case of using a homogenizer, from the viewpoint of further reducing the particle size of the second heteropolyacid compound contained in the second slurry to improve the extrudability, specifically, it is preferable to set the treatment time to 30 seconds or more. In order to adjust the particle size (median particle size, 10% particle size, and 90% particle size) of the second heteropolyacid compound contained in the second slurry to a preferable particle size range after the pulverization treatment, the treatment time can be extended, and in addition, the number of implementation times can also be increased. From the viewpoints of preventing the volatilization of the solvent component and avoiding the freezing of the slurry, the temperature of the slurry is preferably set to 0°C or more and 80°C or less, and more preferably set to 0°C or more and 40°C or less.

[0059] In the present embodiment, from the viewpoints of the durability of the selected equipment and avoiding the freezing of the slurry, the wet pulverization treatment in step (2) is preferably performed at a temperature of 0°C or more and 80°C or less. From the viewpoint of suppressing the wear of the equipment, it is more preferably performed at a temperature of 0°C or more and 50°C or less. From the viewpoint of the restriction of the material of the equipment, it is further preferably performed at a temperature of 0°C or more and 40°C or less. In addition, in order to obtain a second slurry containing second heteropolyacid compound particles having a specified particle size, the treatment time of the wet pulverization treatment can be appropriately adjusted. Specifically, for example, in order to adjust the particle size (median particle size, 10% particle size, and 90% particle size) of the heteropolyacid compound particles after the wet pulverization treatment to a preferable particle size range, the time taken for the wet pulverization treatment can be extended, and in addition, the number of implementation times can also be increased. Specifically, in the case of performing the wet pulverization treatment using a DYNO mill, by further slowing down the supply speed of the first slurry, the treatment time taken for the wet pulverization treatment can be extended, and by performing the pulverization treatment again on the slurry after the wet pulverization treatment, the number of treatment times can be increased. In addition, the first slurry can also be diluted with water or a solvent in advance and then the wet pulverization treatment can be performed.

[0060] In the present embodiment, the "particle size of the second heteropolyacid compound particles (median particle size (D50), 10% particle size (D10), 90% particle size (D90))" and the "ratio 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 type particle size distribution measurement, can be carried out under any suitable conditions well-known in the past using any suitable measurement device well-known in the past, and the value obtained by conversion based on the volume basis is used. As the device capable of measuring the particle size (the ratio of particles having a specified 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 cited.

[0061] In the present embodiment, when performing the laser diffraction type particle size distribution measurement and converting based on the volume basis, from the viewpoint of improving the extrudability, the median particle size (D50) of the second heteropolyacid compound particles that can be obtained by wet grinding treatment is preferably 0.50 μm to 8.0 μm, more preferably 0.50 μm to 7.2 μm, still more preferably 1.3 μm to 7.2 μm, and the ratio of heteropolyacid compound particles having a particle size of 10 μm or less is preferably 65% or more, more preferably 70% to 100%.

[0062] Regarding the particle size of the second heteropolyacid compound particles that can be obtained by wet grinding treatment, when performing the laser diffraction type particle size distribution measurement and converting based on the volume basis, from the viewpoint of further improving the extrudability, the 10% particle size (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.

[0063] Regarding the particle size of the second heteropolyacid compound particles that can be obtained by wet grinding treatment, when performing the laser diffraction type particle size distribution measurement and converting based on the volume basis, from the viewpoint of further improving the extrudability, the 90% particle size (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.

[0064] Regarding the conditions for wet grinding treatment, for example, in the case of using a homogenizer, in view of the performance of the selected equipment, specifically, it is preferably set to a temperature of 0°C or higher and 80°C or lower, more preferably set to a temperature of 0°C or higher and 65°C or lower, and it is preferably carried out considering an appropriate treatment time and the number of treatment times. When adjusting the particle size (median particle size, 10% particle size, and 90% particle size) to the above range and adjusting the ratio of heteropolyacid compound particles with a particle size of 10 μm or less to 65% or more, for example, it is preferably carried out with a treatment time of 30 seconds or more and 600 seconds or less. However, when the particle size after treatment is too large, in order to adjust the particle size to the preferred range already described, it is preferably carried out again for the purpose of increasing the number of treatment times. After carrying out the wet grinding treatment again, the particle size is measured again to confirm whether it is within the preferred particle size range. If it is not within the preferred range, it is more preferable to determine to extend the treatment time or increase the number of treatment times.

[0065] The properties such as the viscosity of the second slurry are not particularly limited as long as they can be applied to the subsequent processes. For example, from the viewpoint of more efficient preparation, they can have any suitable properties known in the past. Specifically, the properties of the second slurry can be adjusted, for example, by adjusting the content of the liquid already described or by further adding a solvent for dilution.

[0066] Here, the heteropolyacid compounds that can be contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles of the present embodiment that can be manufactured by process (1) and process (2) will be described.

[0067] (Heteropolyacid compound)

[0068] The catalyst for producing methacrylic acid of the present embodiment contains a heteropolyacid compound that can at least contain phosphorus and molybdenum. In the present embodiment, the heteropolyacid compound can contain free heteropolyacid or a salt of heteropolyacid.

[0069] The catalyst for producing methacrylic acid of the present embodiment preferably contains an acid salt (partially neutralized salt) of heteropolyacid in the salt of heteropolyacid as the heteropolyacid compound, and more preferably contains an acid salt of Keggin-type heteropolyacid as the heteropolyacid compound.

[0070] The heteropolyacid compound contains at least phosphorus and molybdenum, and can also contain other elements on the condition that it does not hinder the catalyst activity. 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 the present embodiment preferably contains the following elements, for example.

[0071] Phosphorus;

[0072] Molybdenum;

[0073] Copper;

[0074] Vanadium;

[0075] at least one element selected from the group consisting of cesium and thallium; and

[0076] at least one element selected from the group consisting of arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium.

[0077] In the present embodiment, the heteropolyacid compound particles, namely the first heteropolyacid compound particles and the second heteropolyacid compound particles, preferably contain a partial neutral salt of a heteropolyacid represented by the following formula (I).

[0078] P a Mo b Cu c V d Cs e Y f O x (I)

[0079] 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,

[0080] 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,

[0081] When b is set to 12, a to f 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, 0.4 ≤ f ≤ 0.6, and x represents a value determined by the oxidation states of the respective atoms. When Y is two or more atoms, f represents the total ratio of the two or more atoms.

[0082] In the present embodiment, as the heteropolyacid represented by formula (I), from the viewpoint of improving the catalyst 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.

[0083] In the present embodiment, more specifically, for the partial neutral salt of the heteropolyacid represented by formula (I), it is more preferable that Y is an antimony atom and f is 0.45 to 0.55.

[0084] (3) [Process (3)] (A process of drying the second slurry to obtain a dried body containing the second heteropolyacid compound particles, kneading the dried body, and performing extrusion molding to obtain a molded body)

[0085] (i) Drying treatment

[0086] In step (3), first, the second slurry obtained in step (2) is dried. The drying treatment in step (3) can be carried out by any suitable drying method known in the art. Examples of the drying method include: evaporation to dryness method, spray drying method using a spray dryer, drum rotary drying method using a rotary kiln, continuous flash gas drying method using a flash dryer, vacuum drying method using a vacuum drum dryer, and method using a filter drying device.

[0087] In the present embodiment, the drying treatment in step (3) is preferably carried out by a spray drying method using any suitable spray dryer known in the art. Regarding the drying conditions, they can be appropriately set as long as the water content in the aqueous slurry (E) is sufficiently reduced, and there is no particular limitation. The temperature during the drying treatment in step (3) is preferably less than 300°C.

[0088] (ii) Kneading treatment and extrusion molding treatment

[0089] Next, a kneading treatment is carried out on the dried body obtained by the drying treatment, and an extrusion molding treatment is carried out using the kneaded product obtained by the kneading treatment, thereby forming a precursor of the catalyst for manufacturing methacrylic acid. In addition, in such an extrusion molding treatment, water, a molding aid, a pore-forming agent, etc. can be added to the dried body as needed. 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 a function as a pore-forming agent in addition to its function as a molding aid.

[0090] Specifically, first, in the dried body (powder-like precursor of the catalyst for manufacturing methacrylic acid) obtained by the above-mentioned drying treatment, fibers such as ceramic fiber and bio-soluble fiber are added as a molding aid as needed, and further water, ammonium nitrate, etc. are added and kneaded to form a kneaded product as a paste-like mixture. The amount of the molding aid is not particularly limited. With respect to 100 parts by mass of the dried body, the amount of fibers such as ceramic fiber, glass fiber, and bio-soluble fiber as the molding 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. With respect to 100 parts by mass of the dried body, 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. With respect to 100 parts by mass of the dried body, 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.

[0091] Next, the kneaded product obtained by the kneading treatment is subjected to an extrusion molding treatment. Specifically, the kneaded product is molded into a granular molded body having a desired shape (such as a cylindrical shape, a spherical shape, a ring shape, etc.) corresponding to the usage mode of the catalyst for methacrylic acid production as a finished product by extrusion molding.

[0092] For the molded body obtained by the extrusion molding treatment as described above, before performing the calcination treatment described later, it is preferable to perform a temperature and humidity adjustment treatment. The method of such a temperature and humidity adjustment treatment is not particularly limited.

[0093] As the temperature and humidity adjustment treatment, for example, a method of exposing the obtained molded body in an atmosphere with a relative humidity of 10% to 60% at a temperature of 40°C to 100°C for about 0.5 hours to about 10 hours is preferably adopted. Such a temperature and humidity adjustment treatment can be performed, for example, in a tank after temperature and humidity adjustment, or by blowing a gas after temperature and humidity adjustment to the molded body. The specific treatment method is not particularly limited. In addition, as the gas for performing such a temperature and humidity adjustment treatment, air is usually used, but an inert gas such as nitrogen can also be used.

[0094] The kneading treatment can be performed using any conventionally known suitable device under any conventionally known suitable conditions selected in consideration of the composition and properties.

[0095] The kneading treatment and the extrusion molding treatment can be carried out using any conventionally known suitable kneading device and extrusion molding device. Examples of the extrusion device that can be used include: any conventionally known suitable Banbury mixer, kneader. Examples of the extrusion molding device that can be used include: any conventionally known suitable plunger extruder, single-screw extruder, co-rotating twin-screw extruder, counter-rotating twin-screw extruder.

[0096] The configuration of the extrusion device that can be used in the extrusion molding treatment is not particularly limited on the condition that the kneaded product obtained as described above can be extruded and molded into a cylindrical shape. For example, the extrusion molding into a cylindrical shape can be performed by using a device equipped with an extrusion die having a cylindrical through-hole. The extrusion speed in the extrusion molding treatment is not particularly limited. When performing the extrusion molding treatment, it is preferable to set the extrusion speed to be constant and perform it.

[0097] In the method for manufacturing the catalyst for methacrylic acid production of the present embodiment, by adjusting the particle size of the heteropolyacid compound particles to the specified range described above through the "wet pulverization treatment" already described, the efficiency of the extrusion molding treatment can be improved.

[0098] Here, the "efficiency of the extrusion molding process" can be evaluated, for example, by the pressure difference between the first extrusion pressure and the second extrusion pressure (second extrusion pressure - first extrusion pressure). The first extrusion pressure is the pressure when the kneaded material is introduced into the extrusion device and the extrusion speed of the molded body extruded from the extrusion device through the extrusion molding process is 0.0051 m / s (first extrusion speed), and the second extrusion pressure is the pressure when the extrusion speed of the molded body is 0.0308 m / s (second extrusion speed).

[0099] The measurement of the extrusion pressure can be carried out as follows: Using an extrusion device equipped with an extrusion die head having a cylindrical through-hole and any suitable pressure sensor known in the past, the pressure is measured using the pressure sensor while performing extrusion at a constant speed. Specific examples are described below. However, the method for measuring the extrusion pressure is not limited to the specific examples described later.

[0100] Regarding the measurement of the extrusion pressure, for example, the kneaded material that has undergone the kneading process described above can be put into a cylindrical mold with an inner diameter of 40 mm equipped with an extrusion die head having a cylindrical through-hole with an inner diameter of 5.4 mm and a length of 10 mm and a pressure sensor, and the first extrusion pressure and the second extrusion pressure are measured, and thus the pressure difference is obtained.

[0101] The pressure sensor only needs to be able to measure the pressure applied to the kneaded material, and there is no particular limitation. As the pressure sensor, specifically, for example, a small pressure sensor "PGM-E" manufactured by Kyowa Electronic Instruments Co., Ltd. can be used.

[0102] When measuring the extrusion pressure, there is no particular limitation on the method for performing extrusion at a constant speed. Such extrusion can, for example, use the extrusion die described above in combination with a Tensilon universal material testing machine, and the crosshead speed of the Tensilon universal material testing machine is set to be constant to extrude the kneaded material, thereby performing extrusion at a constant speed.

[0103] It can be said that the smaller the pressure difference (second extrusion pressure - first extrusion pressure), the more stable the extrusion molding can be performed. Therefore, the smaller this pressure difference, the more it can be evaluated that the efficiency of the extrusion molding process can be improved, and furthermore, the manufacturing efficiency of the catalyst for methacrylic acid production can be improved.

[0104] 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 (second extrusion pressure - first extrusion pressure) is preferably 1.6 MPa or less, and more preferably 1.3 MPa or less.

[0105] (iii) Pre-calcination treatment

[0106] From the viewpoint of removing the contained ammonium nitrate and changing the structure of the heteropolyacid compound, before the calcination described below, it is preferable to perform a treatment (pre-calcination treatment) of holding at a temperature of about 180°C to about 300°C in an atmosphere of an oxidizing gas or a non-oxidizing gas as pre-calcination.

[0107] The pre-calcination treatment may be a treatment of calcining the 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 calcination furnace provided in a calcination apparatus having any suitable configuration known in the art.

[0108] (4) [Step (4)] A step of calcining the molded body to obtain a catalyst for methacrylic acid production

[0109] The calcination treatment in the production method of the present embodiment is a step of calcining the molded body. As the calcination method, there is no particular limitation, and a method commonly used in the art can be appropriately adopted. It should be noted that such a calcination step can be carried out, for example, in an atmosphere of an oxidizing gas such as oxygen or in an atmosphere of a non-oxidizing gas such as nitrogen, and the calcination temperature is preferably set at 300°C or higher. In addition, when the pre-calcination step already described is carried out before such a calcination step, it is preferable to carry out the calcination step at a temperature higher than the temperature used in the pre-calcination step already described.

[0110] In step (4), from the viewpoint of further improving the catalyst activity, it is preferable to adopt a method of performing a multi-stage calcination treatment in an atmosphere of an oxidizing gas or a non-oxidizing gas, and more preferably includes a first calcination treatment of calcining at 360°C to 410°C in an oxidizing gas atmosphere, a second calcination treatment of calcining at 420°C to 500°C in a non-oxidizing gas atmosphere, and a cooling treatment. Hereinafter, a specific description will be given. The calcination treatment is not limited to the specific examples described below.

[0111] (First Calcination Treatment)

[0112] The gas (mixed gas) used for the first calcination treatment may include an oxidizing gas (external air (air), oxygen, etc.), a non-oxidizing gas (inert gas (nitrogen, argon, helium, neon, etc.), reducing gas (carbon dioxide, hydrogen, ammonia, etc.)). In addition, moisture may be present in the oxidizing gas as needed. In this case, the concentration of moisture that can be contained is usually 10% by volume or less. Among them, the mixed gas preferably includes nitrogen, air, argon, helium, and carbon dioxide gas, and more preferably includes nitrogen and air.

[0113] The temperature in the first calcination treatment is preferably set to 360°C to 410°C, more preferably set to 380°C to 410°C. If the temperature in the first calcination treatment is set to such a temperature, the catalytic activity and catalyst life of the catalyst for manufacturing methacrylic acid can be effectively improved.

[0114] The calcination time in the first calcination treatment is preferably 1 hour to 20 hours, more preferably 1 hour to 5 hours. If the first calcination treatment is carried out for 1 hour to 20 hours, calcination can be sufficiently carried out regardless of the composition of the molded body to be treated.

[0115] (Second calcination treatment)

[0116] The second calcination treatment is preferably a treatment of further calcining the calcined product obtained in the first calcination treatment in a calcination furnace that has been pre-calcined. Alternatively, the second calcination treatment can also be carried out for the calcined product obtained in the first calcination treatment in a calcination furnace different from the calcination furnace used for the first calcination treatment.

[0117] Examples of the gas (mixed gas) that can be used in the second calcination treatment include: non-oxidizing gases (inert gases (nitrogen, argon, helium, neon, etc.), reducing gases (carbon dioxide gas, hydrogen, ammonia, etc.)). Among these non-oxidizing gases, nitrogen, argon, helium, and carbon dioxide gas are preferably used, and nitrogen is more preferably used. The non-oxidizing gas can be used alone or in combination of two or more. In addition, as the non-oxidizing gas used in the second calcination treatment, a dry non-oxidizing gas that contains as little moisture as possible is preferably used.

[0118] The second calcination treatment is preferably carried out by setting the temperature to 420°C to 500°C, more preferably by setting the temperature to 430°C to 440°C.

[0119] The calcination time in the second calcination treatment is preferably 1 hour to 20 hours, more preferably 1 hour to 5 hours.

[0120] (Cooling treatment)

[0121] The cooling treatment is an optional step for cooling the calcined product obtained in the second calcination treatment to a specified temperature. Specifically, the calcined product obtained in the second calcination treatment can be cooled to a temperature preferably below 280°C, more preferably below 90°C, for example, in the non-oxidizing gas atmosphere described above.

[0122] Regarding the non-oxidizing gases that can be used in the cooling treatment, examples include: the non-oxidizing gases already described (inert gases (nitrogen, argon, helium, neon), reducing gases (carbon dioxide gas, hydrogen gas, ammonia gas)), etc. Among these non-oxidizing gases, nitrogen, argon, helium, and carbon dioxide are preferred, and nitrogen is more preferred. From the perspective of improving workability, the non-oxidizing gas used in the cooling process is preferably the same gas as the non-oxidizing gas used in the second calcination treatment, that is, directly use the non-oxidizing gas used in the second calcination treatment. The non-oxidizing gas can be used alone or in combination of two or more. In addition, the non-oxidizing gas used in the cooling treatment is preferably a dry non-oxidizing gas that contains as little moisture as possible.

[0123] From the perspective of effectively improving the catalyst activity and catalyst life, the cooling treatment is preferably carried out by adjusting the temperature to 280 °C or lower, and more preferably carried out by adjusting the temperature to 90 °C or lower.

[0124] According to the "method for manufacturing a catalyst for producing methacrylic acid" of the present embodiment including the above processes (treatments), the particle size (median particle size, 10% particle size, 90% particle size) of the heteropolyacid compound particles is adjusted to the specified range already described by wet pulverization treatment, and the ratio of the heteropolyacid compound particles with a particle size of 10 μm or less is adjusted to the specified 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 manufacturing efficiency of the catalyst for producing methacrylic acid can be further improved, and the manufacturing cost of the catalyst for producing methacrylic acid can be further reduced.

[0125] 2. Production of Methacrylic Acid

[0126] The catalyst for producing methacrylic acid that can be produced by the production method already described in the present 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 with the catalyst under specified conditions, and the at least one compound is subjected to a gas-phase catalytic oxidation reaction to obtain methacrylic acid.

[0127] More specifically, the catalyst for producing methacrylic acid obtained by the production method of the present embodiment is particularly preferably used as a catalyst having catalytic activity in the second-stage reaction of the method for producing methacrylic acid by the C4 direct oxidation method, that is, the reaction of converting methacrolein into methacrylic acid.

[0128] Here, the production of methacrylic acid can be carried out by any conventionally known and suitable production method in which a 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 the reactor. Alternatively, a fluidized-bed or moving-bed reactor can be used instead of the fixed-bed reactor.

[0129] When methacrolein is used as the raw material compound, the reaction is preferably carried out under the following conditions. It should be noted that the space velocity can be obtained by dividing the supply amount (L / hour) of the raw materials (raw material compound and mixed gas) passing through the reactor per hour by the volume (L) of the catalyst for producing methacrylic acid in the reactor.

[0130] Conditions:

[0131] Concentration of methacrolein in the raw materials: 1 vol% to 10 vol%

[0132] Concentration of water vapor in the raw materials: 1 vol% to 30 vol%

[0133] Molar ratio of methacrolein to oxygen: 1 / 1 to 1 / 5 (methacrolein / oxygen)

[0134] Space velocity: 500 h -1 ~5000 h -1 (standard state basis)

[0135] Reaction temperature: 250°C to 350°C

[0136] Reaction pressure: 0.1 MPa to 0.3 MPa

[0137] When isobutane is used as the raw material compound, the reaction is preferably carried out under the following conditions.

[0138] Conditions:

[0139] Concentration of isobutane in the raw materials: 1 vol% to 85 vol%

[0140] Concentration of water vapor in the raw materials: 3 vol% to 30 vol%

[0141] Molar ratio of isobutane to oxygen: 1 / 0.05 to 1 / 4 (isobutane / oxygen)

[0142] Space velocity: 400 h -1 ~5000 h -1 (standard state basis)

[0143] Reaction temperature: 250°C to 400°C

[0144] Reaction pressure: 0.1 MPa to 1 MPa

[0145] It should be noted that when isobutyraldehyde and isobutyric acid are used as raw material compounds, the same conditions as those when methacrolein is used as a raw material compound can be set and implemented. In addition, none of the above raw material compounds need to be highly purified products. As a raw material compound, for example, in the case of methacrolein, methacrolein obtained by the gas-phase catalytic oxidation reaction of isobutene and tert-butanol can be used in an unpurified state.

[0146] The evaluation of the methacrylic acid production catalyst manufactured by the method for manufacturing a methacrylic acid production catalyst according to this embodiment, specifically, for example, the methacrolein conversion rate (%), methacrylic acid selectivity (%), and methacrylic acid yield (%) in the case of using methacrolein as a raw material compound can be calculated based on the following formulas.

[0147] Formula:

[0148] Methacrolein conversion rate (%) = [moles of methacrolein that have reacted ÷ moles of methacrolein supplied] × 100

[0149] Methacrylic acid selectivity (%) = [moles of methacrylic acid generated ÷ moles of methacrolein that have reacted] × 100

[0150] Methacrylic acid yield (%) = [methacrolein conversion rate (%) × methacrylic acid selectivity (%)] ÷ 100

[0151] Examples

[0152] Hereinafter, the present invention will be specifically described by way of examples and comparative examples. The present invention is not limited to the examples described below.

[0153] Preparation Example 1

[0154] [Preparation of Aqueous Slurry E]

[0155] 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] were dissolved in 224 g of ion-exchanged water to obtain an aqueous mixture A.

[0156] Ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O] 297 g was dissolved in 330 g of ion-exchanged water heated to 40 °C, and then 8.19 g of ammonium metavanadate [NH4VO3] was suspended therein to obtain an aqueous mixture B.

[0157] While maintaining the temperatures of aqueous mixture A and aqueous mixture B at 40 °C using a water bath, aqueous mixture A was added dropwise to aqueous mixture B with stirring, and then stirred in a sealed container at 120 °C for 5 hours, thereby obtaining aqueous slurry C. The molar ratios of phosphorus to molybdenum (P / Mo), vanadium to molybdenum (V / Mo), and cesium to molybdenum (Cs / Mo) contained in aqueous slurry C were 1.5 / 12, 0.5 / 12, and 1.4 / 12, respectively.

[0158] 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 aqueous mixture D.

[0159] The obtained aqueous mixture D was heated to 120 °C and added to aqueous slurry C in a sealed container while maintaining the temperature at 120 °C and stirring. It was then stirred at 120 °C for another 5 hours, thereby obtaining aqueous slurry E as a first slurry containing first heteropolyacid compound particles a containing a heteropolyacid compound. The molar ratios of phosphorus to molybdenum (P / Mo), vanadium to molybdenum (V / Mo), cesium to molybdenum (Cs / Mo), copper to molybdenum (Cu / Mo), and antimony to molybdenum (Sb / Mo) contained in the first heteropolyacid compound particles a in aqueous slurry E were 1.5 / 12, 0.5 / 12, 1.4 / 12, 0.3 / 12, and 0.5 / 12, respectively.

[0160] For the obtained aqueous slurry E, the particle size distribution of the first heteropolyacid compound particles a contained in aqueous slurry E was measured using a laser diffraction / scattering particle size distribution analyzer [LA-920 manufactured by HORIBA STEC Co., Ltd.]. As a result, the median particle size (50% particle size: D50) was 10.2 μm, the ratio of heteropolyacid compound particles with a particle size of 10 μm or less was 49%, the value of the 10% particle size (D10) was 2.6 μm, and the value of the 90% particle size (D90) was 29.9 μm.

[0161] Example 1

[0162] [Preparation of Aqueous Slurry F1]

[0163] Using a homogenizing mixer (ULTRA-DISPERSER LK-41), an aqueous slurry E containing first heteropolyacid compound particles a was subjected to wet grinding treatment at 30°C for 1 minute, thereby obtaining an aqueous slurry F1 as a second slurry containing second heteropolyacid compound particles b. The median particle size 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 size of 10 μm or less was 90%, the D10 value was 1.0 μm, and the D90 value was 10.1 μm.

[0164] [Preparation of Heteropolyacid Compound Particles (1)]

[0165] The obtained aqueous slurry F1 was heated to 135°C in the atmosphere to evaporate the water and dry it, thereby obtaining heteropolyacid compound particles (1).

[0166] [Preparation of Kneaded Material]

[0167] With respect to 100 parts by mass of the heteropolyacid compound particles (1), 4 parts by mass of ceramic fiber RCF-400SL manufactured by Isolite 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 material.

[0168] [Measurement of Extrusion Pressure]

[0169] The prepared kneaded material 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 Tensilon universal material testing machine. Here, the first extrusion pressure when the extrusion speed of the formed body extruded from the extrusion die was 0.0051 m / s (first extrusion speed) was 1.9 MPa, the second extrusion pressure when the extrusion speed of the formed body was 0.0308 m / s (second extrusion speed) was 2.8 MPa, and the pressure difference between them (second extrusion pressure - first extrusion pressure) was 0.9 MPa. The results are shown in Table 1 below.

[0170] Production Example 1

[0171] [Formation of Formed Body (Extrusion Molding)]

[0172] The kneaded material containing 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 was extruded at an extrusion speed of the formed body of 0.0051 m / s, thereby obtaining a cylindrical formed body.

[0173] [Production of Catalyst for Methacrylic Acid Production]

[0174] The obtained molded body was subjected to temperature and humidity conditioning treatment of drying at 90 °C and 30% relative humidity for 3 hours, then maintained at 220 °C for 22 hours in an air stream, followed by a pre-calcination treatment of maintaining at 250 °C for 1 hour, then a first calcination treatment of maintaining at 390 °C for 4 hours in an air stream, and then a second calcination treatment of maintaining at 435 °C for 4 hours in a nitrogen stream, whereby a particulate catalyst for methacrylic acid production containing heteropolyacid compound particles (1) was obtained.

[0175] [Activity Test of Catalyst for Methacrylic Acid Production]

[0176] 4.5 g of the obtained catalyst for methacrylic acid production was filled 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. Then, a raw material gas (composition: methacrolein 4% by volume, molecular oxygen 12% by volume, water vapor 17% by volume, nitrogen 67% by volume) prepared by mixing methacrolein, air, water vapor and nitrogen 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, whereby a deteriorated catalyst was obtained. Then, the furnace temperature was adjusted to 280 °C, and the raw material gas of the composition described above was further supplied to the obtained deteriorated catalyst at a space velocity of 670 h -1 and reacted. The reaction gas (the gas after reaction) derived 1 hour after the start of the reaction at a furnace temperature of 280 °C was sampled, analyzed by gas chromatography, and the methacrolein conversion rate (%), methacrylic acid selectivity (%) and methacrylic acid yield (%) were calculated based on the following formula. 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%.

[0177] Methacrolein conversion rate (%) = [moles of methacrolein reacted ÷ moles of methacrolein supplied] × 100

[0178] Methacrylic acid selectivity (%) = [moles of methacrylic acid formed ÷ moles of methacrolein reacted] × 100

[0179] Methacrylic acid yield (%) = [methacrolein conversion rate (%) × methacrylic acid selectivity (%)] ÷ 100

[0180] Example 2

[0181] [Preparation of Aqueous Slurry F2]

[0182] The aqueous slurry F1 of 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 particle size of the heteropolyacid compound particles contained in the aqueous slurry F2 was 6.0 μm, the ratio of heteropolyacid compound particles with a particle size of 10 μm or less was 80%, the D10 value was 1.2 μm, and the D90 value was 12.8 μm.

[0183] [Preparation of Heteropolyacid Compound Particles (2)]

[0184] The obtained aqueous slurry F2 was heated to 135°C in the atmosphere to evaporate the water and dry it, thereby obtaining heteropolyacid compound particles (2).

[0185] [Preparation of Kneaded Product]

[0186] Except for using the heteropolyacid compound particles (2) instead of the heteropolyacid compound particles (1) of Example 1 described above, the operation was the same as that in [Preparation of Kneaded Product] of Example 1 to prepare a kneaded product.

[0187] [Measurement of Extrusion Pressure]

[0188] Using the obtained kneaded product, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 described above. 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.

[0189] Example 3

[0190] [Preparation of Aqueous Slurry F3]

[0191] The aqueous slurry F1 of Preparation Example 1 described above and the aqueous slurry E were mixed at a ratio of 1:1 (volume ratio) to obtain an aqueous slurry F3. The median particle size of the heteropolyacid compound particles contained in the aqueous slurry F3 was 7.2 μm, the ratio of heteropolyacid compound particles with a particle size of 10 μm or less was 70%, the D10 value was 1.5 μm, and the D90 value was 15.2 μm.

[0192] [Preparation of Heteropolyacid Compound Particles (3)]

[0193] The obtained aqueous slurry F3 was heated to 135°C in the atmosphere to evaporate the water and dry it, thereby obtaining heteropolyacid compound particles (3).

[0194] [Preparation of the Kneaded Product]

[0195] A kneaded product was prepared by operating in the same manner as in [Preparation of the Kneaded Product] of Example 1, except that the heteropolyacid compound particles (3) were used instead of the heteropolyacid compound particles (1) of Preparation Example 1 described above.

[0196] [Measurement of Extrusion Pressure]

[0197] Using the obtained kneaded product, the extrusion pressure was measured in the same manner as in [Measurement of Extrusion Pressure] of Example 1 described above. Here, the first extrusion pressure was 2.0 MPa when the extrusion speed of the molded body extruded from the extrusion device was 0.0051 m / s (first extrusion speed), and the second extrusion pressure was 3.4 MPa when the extrusion speed of the molded body was 0.0308 m / s (second extrusion speed). The pressure difference between them (second extrusion pressure - first extrusion pressure) was 1.4 MPa.

[0198] Example 4

[0199] [Preparation of Aqueous Slurry F4]

[0200] The aqueous slurry E of Preparation Example 1 described above and 2700 g of alumina balls with a diameter of 15 mm were placed together in an alumina container, and pulverized for 16 hours by continuously rotating a rotary ball mill at a speed of 53 revolutions per minute, thereby obtaining an aqueous slurry F4. The median particle size 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 size of 10 μm or less was 100%, the D10 value was 0.6 μm, and the D90 value was 2.6 μm.

[0201] [Preparation of Heteropolyacid Compound Particles (4)]

[0202] The obtained aqueous slurry F4 was heated to 135°C in the atmosphere to evaporate the moisture and dry it, thereby obtaining heteropolyacid compound particles (4).

[0203] [Preparation of the Kneaded Product]

[0204] A kneaded product was prepared by operating in the same manner as in [Preparation of the Kneaded Product] of Example 1, except that the heteropolyacid compound particles (4) were used instead of the heteropolyacid compound particles (1) of Preparation Example 1 described above.

[0205] [Measurement of Extrusion Pressure]

[0206] Using the obtained kneaded mixture, the extrusion pressure was measured in the same manner as in [Measurement of extrusion pressure] of Example 1 described above. 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. The pressure difference between them (second extrusion pressure - first extrusion pressure) was 1.0 MPa. The results are shown in Table 1 below.

[0207] Comparative Example 1

[0208] [Preparation of heteropolyacid compound particles (5)]

[0209] The aqueous slurry E of Preparation Example 1 described above was heated to 135°C in the atmosphere to evaporate the moisture and dry it, thereby obtaining heteropolyacid compound particles (5).

[0210] [Preparation of kneaded mixture]

[0211] Except for using heteropolyacid compound particles (5) instead of the heteropolyacid compound particles (1) of Preparation Example 1 described above, the operation was the same as in [Preparation of kneaded mixture] of Example 1, thereby preparing a kneaded mixture.

[0212] [Measurement of extrusion pressure]

[0213] Using the obtained kneaded mixture, the extrusion pressure was measured in the same manner as in [Measurement of extrusion pressure] of Example 1 described above. 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. The pressure difference between them (second extrusion pressure - first extrusion pressure) was 2.8 MPa. The results are shown in Table 1 below.

[0214] Comparative Example 2

[0215] [Preparation of aqueous slurry F5]

[0216] The aqueous slurry F1 and the aqueous slurry E of Preparation Example 1 described above were mixed at a ratio of 1:3 (volume ratio) to obtain an aqueous slurry F5. The median particle diameter of the heteropolyacid compound particles contained in the aqueous slurry F5 was 8.7 μm, the proportion of heteropolyacid compound particles with a particle diameter of 10 μm or less was 59%, the D10 value was 1.9 μm, and the D90 value was 19.9 μm.

[0217] [Preparation of heteropolyacid compound particles (6)]

[0218] The obtained aqueous slurry F5 was heated to 135 °C in the atmosphere to evaporate the moisture and dry it, thereby obtaining heteropolyacid compound particles (6).

[0219] [Preparation of the kneaded product]

[0220] A kneaded product was prepared in the same manner as in [Preparation of the kneaded product] of Example 1, except that the heteropolyacid compound particles (6) were used instead of the heteropolyacid compound particles (1) of Preparation Example 1 described above.

[0221] [Measurement of extrusion pressure]

[0222] Using the obtained kneaded product, 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 them was 1.8 MPa. The results are shown in Table 1 below.

[0223] [Table 1]

[0224]

[0225] According to Examples 1 to 4 in which the particle size (median particle size, 10% particle size, 90% particle size) of the heteropolyacid compound particles was adjusted to a specified range by wet pulverization treatment and the ratio of particles having a particle size of 10 μm or less was adjusted to 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 Example 1 and Comparative Example 2.

Claims

1. A method for producing a catalyst for producing methacrylic acid, wherein: The catalyst for producing methacrylic acid contains heteropolyacid compound particles, and the production method comprises the following steps (1) to (4): [Step (1)] A step of preparing a first slurry containing first heteropolyacid compound particles, wherein the first heteropolyacid compound particles contain at least molybdenum, phosphorus, copper, vanadium, and cesium; [Step (2)] a step of preparing a second slurry containing second heteropolyacid compound particles by wet pulverizing the first slurry, wherein the median particle size (D50) of the second heteropolyacid compound particles is 0.50 μm to 8.0 μm when the laser diffraction particle size distribution is measured and converted on a volume basis, and the ratio of the heteropolyacid compound particles having a particle size of 10 μm or less is 65% or more; [Step (3)] a step of drying the second slurry to obtain a dried body containing the second heteropolyacid compound particles, kneading the dried body, and extruding the mixed body to obtain a molded body; [Step (4)] A step of calcining the molded body to obtain a catalyst for producing methacrylic acid.

2. The method for producing a catalyst for producing methacrylic acid according to claim 1, wherein When laser diffraction particle size distribution measurement is performed and the particle size distribution is converted on a volume basis, a 10% particle size (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 producing methacrylic acid according to claim 1 or 2, wherein: When laser diffraction particle size distribution measurement is performed and the particle size distribution is converted on a volume basis, a 90% particle size (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 producing methacrylic acid according to claim 1 or 2, wherein: The wet pulverization treatment is performed at a temperature of 0° C. or higher and 80° C. or lower.

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

6. The method for producing a catalyst for producing methacrylic acid according to claim 1 or 2, wherein: The heteropolyacid compound contained in the first heteropolyacid compound particles and the second heteropolyacid compound particles is a partially neutralized salt of a heteropolyacid represented by the following formula (I), P a Mo b With c V d Cs e Y f A 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, and 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 set to 12, a~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, x represents a value determined by the oxidation state of each atom, and when Y is two or more atoms, f represents the total ratio of the two or more atoms.

7. A method for producing methacrylic acid, wherein: The method for producing methacrylic acid comprises the step of bringing at least one compound selected from the group consisting of methacrolein, isobutylaldehyde, isobutane and isobutyric acid into contact with the catalyst for producing methacrylic acid produced by the method for producing the catalyst for producing methacrylic acid according to claim 1 or 2, and subjecting the at least one compound to a gas-phase catalytic oxidation reaction, thereby obtaining methacrylic acid.

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