Apparatus for manufacturing a catalyst for methacrylic acid production and method for manufacturing a catalyst for methacrylic acid production

Abstract

To provide a catalyst for producing (meth)acrylic acid having stable catalyst activity throughout the seasons.SOLUTION: A firing device 10 comprises: a compressor 12 that takes in and compresses outside air; a dehumidifier 13 that is connected to the compressor by first piping 11a and dehumidifies the outside air compressed by the compressor; a heater 14 that is connected to the dehumidifier by second piping 11b and heats the outside air dehumidified by the dehumidifier; and firing furnace 15 that is connected to the heater by third piping 11c, is supplied with the outside air heated by the heater and fires a precursor of a catalyst for producing (meth)acrylic acid including a heteropolyacid compound including phosphorus and molybdenum; and a steam generator 16 that is connected to either one or both the second piping and the third piping connected by a fourth piping 11da and 11db, and supplies steam to either one or both of the second piping and the third piping to adjust a water content of the mixed gas to be supplied to the firing furnace.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an apparatus for producing a catalyst for methacrylic acid production, and further to a method for producing a catalyst for methacrylic acid production. [Background technology]

[0002] Conventionally, heteropoly acids containing phosphorus and molybdenum, and their salts, have been known to be effective catalysts for producing methacrylic acid by gas-phase catalytic oxidation reactions such as those of methacrolein. Such catalysts are usually produced by drying an aqueous mixture containing the catalyst raw materials and then calcining it (see Patent Document 1).

[0003] Specifically, Patent Document 1 discloses a method for producing a catalyst for methacrylic acid production, which involves calcining a catalyst precursor under predetermined conditions, with the aim of producing a catalyst for methacrylic acid production having excellent catalytic activity and catalyst life. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2012-245432 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the conventional method for producing methacrylic acid catalysts, as exemplified by Patent Document 1 mentioned above, the catalytic activity of the produced methacrylic acid catalyst can fluctuate depending on the time of year (season) in which the catalyst is produced, which can lead to significant fluctuations in the conversion rate of methacrylic acid.

[0006] Here, we will explain in detail with reference to Figure 3. Figure 3 is a graph showing an example of fluctuations in the H2O concentration in the ambient air.

[0007] As shown in Figure 3, the concentration of H2O in the outside air varies greatly with the seasons. In Japan in particular, it tends to be high at around 3% in summer (July and August) and low at around 0.5% in winter (December to March).

[0008] Furthermore, the activity of the catalyst for methacrylic acid production correlates with seasonal fluctuations in the concentration of H2O in the ambient air; the higher the concentration of H2O in the ambient air, the lower the catalytic activity of the catalyst for methacrylic acid production, i.e., the conversion rate to methacrylic acid.

[0009] Therefore, there is a need for a method for producing a methacrylic acid catalyst that suppresses fluctuations in catalytic activity depending on the timing of production and has stable catalytic activity throughout the four seasons, as well as a manufacturing apparatus for carrying out this method. [Means for solving the problem]

[0010] The inventors of the present invention conducted diligent studies to solve the above problems and found that the above problems can be solved by a calcination apparatus having a predetermined configuration, and furthermore, by a catalyst for methacrylic acid production equipped with the calcination apparatus, thus completing the present invention.

[0011] In other words, the present invention provides the following [1] to [7]. [1] A compressor that takes in outside air and compresses it, A dehumidifier is connected to the compressor by a first pipe and dehumidifies the outside air compressed by the compressor, A heater is connected to the dehumidifier by a second pipe, and the heater heats the outside air from which the dehumidifier has removed moisture. A calcination furnace is connected to the heater by a third pipe, to which heated outside air from the heater is supplied, and to calcine a precursor of a methacrylic acid production catalyst containing a heteropoly acid compound containing phosphorus and molybdenum, A steam generator is connected to either or both of the second and third pipes by a fourth pipe, and supplies steam to either or both of the second and third pipes to adjust the water content of the mixed gas supplied to the firing furnace. A firing apparatus equipped with the following features. [2] The firing apparatus according to claim 1, wherein the fourth pipe is a pipe connecting the steam generator and the third pipe. [3] The firing apparatus according to [1] or [2], wherein the steam generator is a device that adjusts the water content of the mixed gas supplied to the firing furnace to 0.1 to 2.0 volume percent. [4] The firing apparatus according to any one of items [1] to [3], wherein the heater is a device that heats the outside air supplied from the dehumidifier to 60 to 200°C. [5] A catalyst for methacrylic acid production apparatus including a calcination apparatus as described in any one of items [1] to [4], A slurry preparation unit for preparing a raw material slurry containing phosphorus and molybdenum, A drying unit connected to the slurry preparation unit, which dries the raw material slurry prepared in the slurry preparation unit to form a powder, A kneading and extrusion molding unit connected to the drying unit, which kneads and extrudes the powder dried by the drying unit to form a precursor for a catalyst for methacrylic acid production, A calcination apparatus connected to the extrusion molding section, which calcines the precursor of the methacrylic acid production catalyst formed in the kneading and extrusion molding section to produce a methacrylic acid production catalyst, and A catalyst manufacturing apparatus for methacrylic acid production, equipped with the following features. [6] A slurry preparation step for preparing a raw material slurry containing phosphorus and molybdenum, A drying step in which the raw material slurry is dried to form a powder, A kneading and extrusion process to knead the aforementioned powder and extrude it to form a precursor for a catalyst for methacrylic acid production, The process includes a calcination step of calcining the precursor of the catalyst for methacrylic acid production to obtain the catalyst for methacrylic acid production, The firing step is carried out using a firing apparatus comprising a compressor that takes in and compresses outside air, a dehumidifier connected to the compressor by a first pipe and that dehumidifies the outside air compressed by the compressor, a heater connected to the dehumidifier by a second pipe and that heats the outside air dehumidified by the dehumidifier, a firing furnace connected to the heater by a third pipe and into which the outside air heated by the heater is supplied to fire a precursor of a catalyst for producing methacrylic acid containing a heteropolyacid compound containing phosphorus and molybdenum, and a steam generator connected by a fourth pipe to either one or both of the second pipe and the third pipe and that supplies steam to either one or both of the second pipe and the third pipe, the firing step being one in which steam is supplied from the steam generator to either one or both of the second pipe and the third pipe to form a mixed gas containing outside air and steam, and the precursor of the catalyst for producing methacrylic acid is fired to form a catalyst for producing methacrylic acid while adjusting the water content of the mixed gas supplied to the firing furnace. A method for producing a catalyst for producing methacrylic acid. 〔7〕 The method for producing a catalyst for producing methacrylic acid according to 〔6〕, wherein the firing step is carried out while adjusting the water content of the mixed gas supplied to the firing furnace to 0.1 to 2.0% by volume.

Effects of the Invention

[0012] According to the present invention, it is possible to provide a method for producing a catalyst for producing methacrylic acid that suppresses fluctuations in the catalytic activity of the catalyst for producing methacrylic acid depending on the production timing and has a stable catalytic activity throughout the four seasons, and further, a production apparatus for carrying out the production method.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a schematic diagram for explaining a configuration example of the production apparatus of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram for explaining a configuration example of the firing apparatus of the present embodiment. [Figure 3] FIG. 3 is a graph showing an example of fluctuations in the H2O concentration in the outside air. [Modes for carrying out the invention]

[0014] The embodiments of the present invention will be described in detail below. The present invention is not limited to the specific embodiments shown below. The drawings only schematically show the shape, size, and arrangement of the components to the extent that the invention can be understood, and each component can be modified as appropriate without departing from the spirit of the present invention.

[0015] 1. Apparatus for manufacturing catalysts for methacrylic acid production First, with reference to Figure 1, the general outline of the manufacturing apparatus for the methacrylic acid production catalyst of this embodiment will be described. Figure 1 is a schematic diagram illustrating an example of the configuration of the manufacturing apparatus of this embodiment.

[0016] As shown in Figure 1, the methacrylic acid production catalyst production apparatus 1 of this embodiment comprises a slurry preparation unit 20 for preparing a raw material slurry containing phosphorus and molybdenum, a drying unit 30 connected to the slurry preparation unit 20 for drying the raw material slurry prepared in the slurry preparation unit 20 into a powder, a kneading and extrusion molding unit 40 connected to the drying unit 30 for kneading and extruding the powder dried in the drying unit 30 to form a precursor for the methacrylic acid production catalyst, and a calcination apparatus 10 connected to the kneading and extrusion molding unit 40 for calcining the precursor for the methacrylic acid production catalyst formed in the kneading and extrusion molding unit 40.

[0017] The configuration of the catalyst manufacturing apparatus for methacrylic acid production according to this embodiment will be described in detail below. The slurry preparation section 20, drying section 30, and kneading and extrusion molding section 40 are equipped with conventionally known and suitable configurations, and can be constructed using conventionally known and suitable configurations, functional parts, devices, piping, etc. Therefore, a detailed explanation of these will be omitted, and a particular example of the configuration of the calcination apparatus 10 will be described.

[0018] (Firing equipment) Referring to Figure 2, an example of the configuration of the firing apparatus 10 of this embodiment will be described. Figure 2 is a schematic diagram illustrating an example of the configuration of the firing apparatus of this embodiment.

[0019] As shown in Figure 2, the firing apparatus 10 includes a compressor 12 that takes in and compresses outside air, connected to the compressor 12 by a first pipe 11a (sometimes called line A), a dehumidifier 13 that dehumidifies the outside air compressed by the compressor 12, connected to the dehumidifier 13 by a second pipe 11b (sometimes called line B), a heater 14 that heats the outside air dehumidified by the dehumidifier 13, connected to the heater 14 by a third pipe 11c (sometimes called line C), and the outside air heated by the heater 14 The system includes a calcination furnace 15 that calcines a precursor for a methacrylic acid production catalyst containing a heteropoly acid compound containing phosphorus and molybdenum, and a steam generator 16 that is connected to either or both of the second pipe 11b and the third pipe 11c by a fourth pipe 11d (11da and 11db) (sometimes referred to as line D), and supplies steam to either or both of the second pipe 11b and the third pipe 11c to adjust the water content of the mixed gas supplied to the calcination furnace 15.

[0020] (i) Compressor In this embodiment, the configuration of the compressor 12 is not particularly limited, provided that it can take in outside air, compress it, and send the compressed outside air to the dehumidifier 13 via the first piping 11a. Any suitable configuration, functional parts, and devices conventionally known in the art can be applied to the compressor 12.

[0021] (ii) Dehumidifier In this embodiment, the dehumidifier 13 is not particularly limited, provided that it can introduce compressed outside air (sometimes called compressed outside air) sent from the compressor 12, dehydrate the compressed outside air to reduce its moisture content, and send the compressed outside air with reduced moisture content to the heater 14 via the second pipe 11b. Any suitable configuration, functional parts, and devices conventionally known in the art can be applied to the dehumidifier 13.

[0022] (iii) Heater In this embodiment, the heater 14 is not particularly limited, provided that it can heat outside air (compressed outside air) with reduced moisture content sent from the dehumidifier 13 by introducing steam supplied from the steam generator 16 via the second pipe 11b, and further via the fourth pipe 11da if the fourth pipe 11da is present. Any suitable configuration, functional parts, and devices conventionally known in the art can be applied to the heater 14.

[0023] It is preferable that the heater 14 can heat the outside air supplied from the dehumidifier 13 to a temperature of 60 to 200°C, and more preferably that it is a device that can heat it to a temperature of 60 to 100°C.

[0024] (iv) Firing furnace In this embodiment, the calcination furnace 15 is not particularly limited, provided that it can calcine the precursor of the methacrylic acid production catalyst formed in the kneading and extrusion molding section 40 by introducing steam supplied from the steam generator 16 through the third pipe 11c, and further through the fourth pipe 11db if a fourth pipe 11db is present. The calcination furnace 15 can be any suitable configuration, function, and apparatus that are conventionally known in the art.

[0025] (v) Steam generator In this embodiment, the steam generator 16 is not particularly limited, provided that it can generate steam and supply steam to either or both of the fourth pipe 11da connected to the second pipe 11b and the fourth pipe 14db connected to the third pipe 11c via the fourth pipe 11d (11da and 11db) to adjust the water content of the mixed gas supplied to the firing furnace 15. Any suitable configuration, functional parts, and apparatus conventionally known in the art can be applied to the steam generator 16.

[0026] Furthermore, the fourth pipe 11d is preferably a pipe (fourth pipe 11db) that connects the steam generator 16 and the third pipe 11c, particularly from the viewpoint of preventing condensation of water vapor.

[0027] Known methods can be applied to generate superheated steam in the steam generator 16. Examples of methods for generating superheated steam in the steam generator 16 include heating by a burner, heating by an electric heater, or heating using electromagnetic induction, with heating by an electric heater being preferred.

[0028] (vi) Piping The piping 11, including the first piping 11a, the second piping 11b, the third piping 11c, the fourth piping 11da and 11db, and the piping that can interconnect the firing apparatus 10, slurry preparation section 20, drying section 30, and kneading and extrusion molding section 40, are not particularly limited, provided that they can introduce outside air, raw materials, etc., delivered from the functional section provided in the preceding stage to the functional section of the next stage.

[0029] In this embodiment, it is preferable that the fourth pipe 11d is a pipe connecting the steam generator 16 and the third pipe 11c, and in this case, only the fourth pipe 11db may be provided as the fourth pipe 11d. By providing the fourth pipe 11db, steam can be supplied at a position closer to the firing furnace 15, so that the moisture content of the mixed gas introduced into the firing furnace 15 can be adjusted to the above predetermined range more reliably and accurately.

[0030] 2. Catalyst for the production of methacrylic acid The catalyst for methacrylic acid production obtained by the manufacturing method using the manufacturing apparatus 1 including the calcination apparatus 10 of this embodiment is preferably used as a catalyst having catalytic activity in the second step reaction of the methacrylic acid production method (details will be described later), particularly preferably the C4 direct acid method, i.e., the reaction in which methacrolein is converted to methacrylic acid.

[0031] The catalyst for methacrylic acid production in this embodiment includes a heteropoly acid compound containing phosphorus and molybdenum. In this embodiment, the heteropoly acid compound may include free heteropoly acid or a salt of heteropoly acid.

[0032] The catalyst for producing methacrylic acid in this embodiment preferably contains an acidic salt (partially neutralized salt) of a heteropoly acid, and more preferably contains an acidic salt of a Keggin-type heteropoly acid.

[0033] The heteropoly acid compound contains phosphorus and molybdenum as essential elements and may contain other elements, provided that catalytic activity is not inhibited. Other elements include vanadium, potassium, rubidium, cesium, thallium, copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium. A heteropoly acid compound containing other elements preferably contains, for example, the following elements: Lin; molybdenum; vanadium; At least one element selected from the group consisting of potassium, rubidium, cesium, and thallium (hereinafter sometimes referred to as "element X"); and At least one element selected from the group consisting of copper, arsenic, antimony, boron, silver, bismuth, iron, cobalt, lanthanum, and cerium (hereinafter sometimes referred to as "element Y").

[0034] As a heteropoly acid compound, it is particularly preferable that phosphorus, vanadium, element X, and element Y are each present in proportions of 3 atoms or less per 12 atoms of molybdenum.

[0035] 3. Method for producing a catalyst for methacrylic acid The method for producing the catalyst for methacrylic acid according to this embodiment is: A slurry preparation step for preparing a raw material slurry containing phosphorus and molybdenum, A drying process in which the raw material slurry is dried to form a powder, A kneading and extrusion process to form a precursor for a catalyst for methacrylic acid production by kneading powder and extruding it, This includes a calcination step of calcining a precursor for a catalyst used to produce methacrylic acid, The calcination process includes a compressor 12 that takes in and compresses outside air, a dehumidifier 13 connected to the compressor 12 by a first pipe 11a that dehumidifies the outside air compressed by the compressor 12, a heater 14 connected to the dehumidifier 13 by a second pipe 11b that heats the outside air dehumidified by the dehumidifier 13, a calcination furnace 15 connected to the heater 14 by a third pipe 11c that supplies the outside air heated by the heater 14 and calcines a precursor for a methacrylic acid production catalyst containing a heteropoly acid compound containing phosphorus and molybdenum, and the second pipe 11b and the third pipe 11c A calcination process is carried out using a calcination apparatus 10 which includes a steam generator 16 connected to either or both of the second pipe 11b and the third pipe 11c by a fourth pipe 11da and 11db, and which supplies steam to either or both of the second pipe 11b and the third pipe 11c, and the calcination process includes supplying steam from the steam generator 16 to either or both of the second pipe 11b and the third pipe 11c to form a mixed gas containing outside air and steam, and calcining a precursor for a catalyst for methacrylic acid production while adjusting the water content of the mixed gas supplied to the calcination furnace 15. The above process will be described below.

[0036] (Slurry preparation process) The slurry preparation process is a process of preparing a raw material slurry containing raw materials that include phosphorus and molybdenum. In the slurry preparation process, a mixture of raw material compounds containing each element found in the catalyst for methacrylic acid production is used. Examples of such compounds include oxoacids, oxoates, oxides, nitrates, carbonates, bicarbonates, hydroxides, and halides containing the "essential elements" already described, particularly phosphorus and molybdenum, and "other elements."

[0037] In this embodiment, examples of compounds containing phosphorus as an element include phosphoric acid and phosphates. Examples of compounds containing molybdenum as an element include molybdic acid, molybdate salts, molybdenum oxide, and molybdenum chloride. Examples of compounds containing vanadium as an element include vanadic acid, vanadate salts, vanadium oxide, and vanadium chloride.

[0038] Compounds containing the previously described "element X" include oxides, nitrates, carbonates, bicarbonates, hydroxides, and halides. Compounds containing the above-mentioned element Y include oxoacids, oxoates, nitrates, carbonates, hydroxides, and halides.

[0039] In forming a precursor for the methacrylic acid production catalyst, first, a raw material slurry is prepared according to conventional methods. Specifically, the above-mentioned raw material compound is mixed with water to prepare an aqueous solution or suspension, and then matured at a conventionally known suitable temperature and time to prepare the raw material slurry.

[0040] In the slurry preparation process, when preparing aqueous solutions or suspensions, it is preferable to further add ammonia and ammonium salts to obtain aqueous solutions or suspensions containing ammonium salts.

[0041] Furthermore, in the slurry preparation step, instead of adding ammonia or ammonium salt when preparing aqueous solutions or suspensions, an ammonium compound may be used as at least one of the above compounds containing phosphorus, molybdenum, vanadium, element X, or element Y. When an ammonium compound is used in this way, a precursor for a methacrylic acid production catalyst containing a non-Kegin-type heteropolyate can be obtained, and furthermore, a precursor for a methacrylic acid production catalyst containing a Kegin-type heteropolyate can be obtained by heat treatment.

[0042] (drying process) In this embodiment, the drying step is connected to the slurry preparation unit 20 and is a step in which the raw material slurry prepared in the slurry preparation unit 20 as described above is dried in the drying unit 30 to form a powder. In this embodiment, it is preferable that the drying unit 30 is a functional unit equipped with a conventionally known and suitable spray dryer.

[0043] The drying process can be carried out by any suitable drying method that is conventionally known. Examples of drying methods include spray drying using a spray dryer, drum rotation drying using a rotary kiln, continuous instantaneous airflow drying using a flash jet dryer, vacuum drying using a vacuum drum dryer, and methods using a filtration drying apparatus.

[0044] In this embodiment, the drying process is preferably carried out by a spray drying method using a conventionally known and suitable spray dryer.

[0045] (Mixing and extrusion process) In this embodiment, the kneading and extrusion process is a process of kneading the powder and extruding it to form a precursor for the methacrylic acid production catalyst.

[0046] Specifically, first, to the powder obtained by the above drying process (a precursor of the powdered methacrylic acid production catalyst), conventionally known and suitable molding aids such as ceramic fibers, biosoluble fibers, and binders such as methylcellulose are added as needed, and then water, ammonium nitrate water, etc., are added and kneaded.

[0047] Next, the mixture obtained by kneading is molded. Specifically, it is preferable to mold it into pellets of a desired shape (e.g., cylindrical, spherical, ring-shaped, etc.) depending on the intended use.

[0048] As described above, it is preferable to subject the resulting pellets to a temperature and humidity control treatment before the firing process described later. The method of such a temperature and humidity control treatment is not particularly limited. As a temperature and humidity control treatment, it is preferable to expose the pellets (molded bodies) to an atmosphere with a temperature of 40 to 100°C and a relative humidity of 10 to 60% for about 0.5 to 10 hours. Such a temperature and humidity control treatment may be carried out, for example, in a temperature and humidity controlled tank, or by blowing a temperature and humidity controlled gas onto the pellets, and the specific treatment method is not particularly limited. In addition, air is usually used as the gas when performing such a temperature and humidity control treatment, but an inert gas such as nitrogen gas may also be used.

[0049] Next, the obtained pellets are pre-calcined by heat treatment at a temperature of approximately 180-300°C in an oxidizing gas atmosphere or a non-oxidizing gas atmosphere.

[0050] The kneading and extrusion processes can be carried out using any suitable kneading and drying equipment that is conventionally known. Examples of kneading equipment include any suitable Banbury mixer and kneader that is conventionally known, and examples of extrusion equipment include any suitable plunger extruder, single-screw extruder, twin-screw coaxial extruder, and twin-screw anomalous-direction extruder that is conventionally known.

[0051] (Firing process) The calcination step in the method for producing a methacrylic acid catalyst of this embodiment (hereinafter sometimes simply referred to as the "production method") may include a first calcination step, a second calcination step, and a cooling step. These will be described in detail below.

[0052] (First firing process) The first calcination step is a process in which the precursor of the methacrylic acid production catalyst, which has been prepared and delivered in the kneading and extrusion molding section 40 as described above, is calcined in the calcination furnace 15 of the calcination apparatus 10 having the configuration described above. This will be explained in detail below.

[0053] In carrying out the first firing process, it is preferable to adjust the water content of the mixed gas supplied to the firing furnace 15 to preferably 0.1 to 2.0 volume%, more preferably 0.8 to 1.8 volume%, using the steam generated and supplied by the steam generator 16.

[0054] As described above, by adjusting the water content of the mixed gas, fluctuations in the catalytic activity of the methacrylic acid production catalyst due to the time of year can be effectively suppressed, and a methacrylic acid production catalyst with stable catalytic activity throughout the four seasons can be produced. Furthermore, catalytic activity and catalyst life can be effectively improved.

[0055] The temperature in the first firing step is preferably 360 to 410°C, and more preferably 380 to 400°C. Such temperatures effectively improve the catalytic activity and lifespan of the methacrylic acid production catalyst.

[0056] The firing time in the first firing step is preferably 1 to 20 hours, and more preferably 1 to 5 hours. Performing the first firing for 1 to 20 hours ensures that the catalyst precursor is sufficiently fired regardless of its composition.

[0057] The mixed gas used in the first calcination step may contain oxidizing gases (such as outside air and oxygen), non-oxidizing gases (such as inert gases like nitrogen, argon, helium, and neon), and reducing gases like carbon dioxide, hydrogen, and ammonia). Among these, it is preferable that nitrogen, air, argon, helium, and carbon dioxide be included, and it is more preferable that nitrogen and air be included. These gases may be used individually or in combination of two or more.

[0058] (Second firing process) The second firing step is preferably a step in which the fired product obtained in the first firing step is further fired at 420 to 500°C under the non-oxidizing gas atmosphere described above.

[0059] Examples of non-oxidizing gases that can be used in the second firing process include non-oxidizing gases (inert gases such as nitrogen gas, argon gas, helium gas, and neon gas) and reducing gases such as carbon dioxide, hydrogen, and ammonia. Among these non-oxidizing gases, nitrogen gas, argon gas, helium gas, and carbon dioxide gas are preferred, and nitrogen gas is more preferred. Non-oxidizing gases may be used individually or in combination of two or more. Furthermore, it is preferable to use a non-oxidizing gas in a dry state that contains as little moisture as possible as the non-oxidizing gas used in the second firing process.

[0060] The second firing process is preferably carried out at a temperature of 420 to 500°C, and more preferably at 430 to 440°C.

[0061] The firing time in the second firing process is preferably 1 to 20 hours, and more preferably 1 to 5 hours.

[0062] (cooling process) The cooling process involves cooling the calcined product obtained in the second calcination process to a temperature of 280°C or lower, for example, under a non-oxidizing gas atmosphere as previously described.

[0063] Non-oxidizing gases used in the cooling process include the non-oxidizing gases mentioned above (inert gases (nitrogen gas, argon gas, helium gas, neon gas), reducing gases (carbon dioxide, hydrogen, ammonia)). Among these non-oxidizing gases, nitrogen gas, argon gas, helium gas, and carbon dioxide are preferred, with nitrogen gas being more preferred. From the viewpoint of workability, it is preferable to use the same non-oxidizing gas used in the second firing process as the non-oxidizing gas used in the cooling process, that is, to use the same non-oxidizing gas used in the second firing process. Non-oxidizing gases may be used alone or in combination of two or more. Furthermore, it is preferable to use a non-oxidizing gas in the cooling process that is as dry as possible and contains as little moisture as possible.

[0064] The cooling process is preferably carried out at a temperature of 280°C or lower, and more preferably at 250°C or lower, from the viewpoint of effectively improving catalyst activity and catalyst life.

[0065] (Methacrylic acid production method) The catalyst for methacrylic acid production obtained by the method for producing methacrylic acid according to this embodiment has excellent catalytic activity and catalyst life. Using this catalyst for methacrylic acid production, for example, raw material compounds such as methacrolein, isobutyraldehyde, isobutane, and isobutyric acid can be subjected to a gas-phase catalytic oxidation reaction to convert the raw material compounds with a good conversion rate, thereby enabling the stable production of methacrylic acid over a long period of time.

[0066] The production of methacrylic acid is typically carried out by filling a fixed-bed multitube reactor with a catalyst for methacrylic acid production and supplying the raw material compound and a mixed gas with the water content adjusted as previously described to this reactor. Alternatively, fluidized-bed or moving-bed reactors may also be used instead of fixed-bed reactors.

[0067] When methacrolein is used as a starting compound, the reaction is preferably carried out under the following conditions. The space velocity is determined by dividing the supply rate of raw materials (starting compound and mixed gas) per hour (L / h) passing through the reactor by the volume (L) of the catalyst for methacrylic acid production in the reactor. Concentration of methacrolein in the raw material: 1-10% by volume Water vapor concentration in raw materials: 1-30% by volume Molar ratio of methacrolein to oxygen: 1 / 1 to 1 / 5 (methacrolein / oxygen) Space velocity: 500~5000h -1 (Standard condition criteria) Reaction temperature: 250~350℃ Reaction pressure: 0.1~0.3 MPa

[0068] When isobutane is used as a starting compound, the reaction is preferably carried out under the following conditions. Isobutane concentration in raw materials: 1-85% by volume Water vapor concentration in raw materials: 3-30% by volume Molar ratio of isobutane to oxygen: 1 / 0.05 to 1 / 4 (isobutane / oxygen) Space velocity: 400~5000h -1 (Standard condition criteria) Reaction temperature: 250~400℃ Reaction pressure: 0.1~1MPa

[0069] Furthermore, when using isobutyraldehyde and isobutyric acid as raw material compounds, the process can be carried out under the same conditions as when using methacrolein. These raw material compounds do not need to be highly purified. For example, in the case of methacrolein, unpurified methacrolein obtained by the gas-phase catalytic oxidation reaction of isobutylene and tert-butyl alcohol may be used as the raw material compound. [Examples]

[0070] The present invention will be described more specifically below based on examples and reference examples. The present invention is not limited to the following examples.

[0071] (Reference example 1) [Preparation process for aqueous mixture (A1)] First, 483.51 g of 67.5% by mass nitric acid, 507.47 g of 75% by mass orthophosphate, and 706.55 g of cesium nitrate [CsNO3] were dissolved in 4144 g of deionized water heated to 40°C to obtain aqueous mixture (A1).

[0072] [Preparation process for aqueous mixture (B1)] 6105g of ion-exchanged water heated to 40℃, to which ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O 24 After dissolving 5487.47g of [4H2O], 151.48g of ammonium metavanadate [NH4VO3] was suspended to obtain aqueous mixture (B1).

[0073] [Preparation process for aqueous slurry (C1)] While maintaining the temperature of the aqueous mixture (A1) and the aqueous mixture (B1) at 40°C, the aqueous mixture (A1) was added dropwise to the aqueous mixture (B1) under stirring conditions and mixed. The resulting mixture was then stirred in a sealed container while being maintained at 120°C for 5 hours to obtain an aqueous slurry (C1).

[0074] [Preparation process for aqueous mixture (D1)] An aqueous mixture (D1) was prepared by suspending 187.77 g of antimony trioxide [Sb2O3] and 621.46 g of a 30.6% by mass aqueous solution of copper nitrate trihydrate [Cu(NO3)2·3H2O] in 500 g of deionized water.

[0075] [Preparation process for aqueous slurry (E1)] In the preparation step of the aqueous slurry (C1) described above, immediately after preparing the aqueous slurry (C1) in a sealed container, the aqueous mixture (D1) was added to the aqueous slurry (C1) which was kept agitated at 120°C in the sealed container, and the resulting mixture was agitated while being held at 120°C for 5 hours in the sealed container to obtain aqueous slurry (E1).

[0076] [Drying and calcination process of aqueous slurry (E1) (production of heteropoly acid compound (1))] The aqueous slurry (E1) obtained as described above was spray-dried using a spray dryer to obtain a dried powder. Next, 4 parts by mass of ceramic fiber, 10.50 parts by mass of ammonium nitrate, and 9.25 parts by mass of deionized water were added to 100 parts by mass of the obtained powder and kneaded, and then extruded into a cylindrical shape with a diameter of 5 mm and a height of 6 mm to obtain a molded body.

[0077] Next, the obtained molded body was subjected to a temperature and humidity control treatment, in which it was dried for 3 hours under conditions of 90°C and 30% relative humidity. Then, a pre-calcination treatment was performed in which it was held in an airflow at 220°C for 22 hours, followed by holding at 250°C for 1 hour, thereby obtaining a molded body (F1), which is a precursor of the catalyst for methacrylic acid production.

[0078] Thereafter, the obtained molded body (F1) was subjected to a firing process in a mixed gas containing air (outside air) and steam (water vapor) (water content: 1.0% by volume) at 390 °C for 3 hours, and then held at 435 °C for 3 hours in a nitrogen stream, whereby a heteropolyacid compound (1) which is a catalyst for producing methacrylic acid was obtained.

[0079] The heteropolyacid compound (1) thus obtained contains phosphorus (P), molybdenum (Mo), copper (Cu), vanadium (V), cesium (Cs) and antimony (Sb), and the atomic ratio (P:Mo:Cu:V:Cs:Sb) of the metal elements contained in the heteropolyacid compound (1) was 1.5:12:0.3:0.5:1.4:0.5.

[0080] From the above production method and atomic ratio, it can be seen that the obtained heteropolyacid compound (1) is a partially neutralized salt represented by the formula: P 1.5 Mo 12 Cu 0.12 V 0.5 Cs 1.4 Sb 0.5 O x In the formula, x is a value determined by the oxidation state of each atom.

[0081] 〔Activity test of heteropolyacid compound (1)〕 9 g of the obtained heteropolyacid compound (1) was filled into a glass microreactor having an inner diameter of 16 mm, and the furnace temperature (the temperature of the furnace for heating the microreactor) was raised to 355 °C.

[0082] Thereafter, 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 (outside air), steam (water vapor) and nitrogen gas was supplied into the microreactor under the condition of a space velocity of 670 h -1 and reacted for 1 hour to initially deteriorate the catalyst for producing methacrylic acid.

[0083] Subsequently, the microreactor's furnace temperature was increased to 280°C, and the reaction was carried out by supplying a raw material gas of the same composition as above at the same space velocity as above, thereby producing methacrylic acid from the raw material gas.

[0084] The outlet gas (reaction gas) from the microreactor was sampled one hour after the start of the reaction and analyzed by gas chromatography. The methacrolein conversion rate (%) (sometimes simply referred to as the conversion rate) was determined based on the following formula. The results of the activity test are shown in Table 1. Formula: Metacrolein conversion rate (%) = [Number of moles of methacrolein reacted ÷ Number of moles of methacrolein supplied] × 100

[0085] (Reference example 2) [Production of heteropoly acid compound (2)] The same procedure as in Reference Example 1 was performed, except that the water content of the mixed gas in Reference Example 1 was set to 2.0 volume%, to obtain heteropoly acid compound (2), which is a catalyst for the production of metatacrylic acid.

[0086] [Activity test of heteropoly acid compound (2)] The activity test was conducted using the same procedure as in the [activity test for heteropoly acid compound (1)] adopted in Reference Example 1 above, except that heteropoly acid compound (2) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 1.

[0087] (Reference example 3) [Production of heteropoly acid compounds (3)] The same procedure as in Reference Example 1 was performed, except that the water content of the mixed gas in Reference Example 1 was set to 2.8% by volume, to obtain a heteropoly acid compound (3), which is a catalyst for the production of metatacrylic acid.

[0088] [Activity test of heteropoly acid compound (3)] The activity test was conducted using the same procedure as in the [activity test for heteropoly acid compound (1)] adopted in Reference Example 1 above, except that heteropoly acid compound (3) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 1.

[0089] (Reference example 4) [Production of heteropoly acid compounds (4)] The same procedure as in Reference Example 1 was performed, except that the water content of the mixed gas in Reference Example 1 was set to 3.5% by volume, to obtain a heteropoly acid compound (4), which is a catalyst for the production of metatacrylic acid.

[0090] [Activity test of heteropoly acid compound (4)] The activity test was conducted using the same procedure as in the [activity test for heteropoly acid compound (1)] adopted in Reference Example 1 above, except that heteropoly acid compound (4) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 1.

[0091] (Reference example 5) [Production of heteropoly acid compounds (5)] Except for setting the water content of the mixed gas in Reference Example 1 to 4.0% by volume, the same procedure as in Reference Example 1 was performed to obtain a heteropoly acid compound (5), which is a catalyst for the production of metatacrylic acid.

[0092] [Activity test of heteropoly acid compound (5)] The activity test was conducted using the same procedure as in the [activity test for heteropoly acid compound (1)] adopted in Reference Example 1 above, except that heteropoly acid compound (5) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 1.

[0093] [Table 1]

[0094] (Example 1) [Preparation process of aqueous mixture (A2)] First, 308.3 kg of 67.5% by mass nitric acid, 323.5 kg of 75% by mass orthophosphate, and 450 kg of cesium nitrate [CsNO3] were dissolved in 2585 kg of deionized water heated to 40°C to obtain aqueous mixture (A2).

[0095] [Preparation process of aqueous mixture (B2)] 582 kg of ion-exchanged water heated to 40°C, to which ammonium heptamolybdate tetrahydrate [(NH4)6Mo7O 24 After dissolving 556 kg of [4H2O], 15.3 kg of ammonium metavanadate [NH4VO3] was suspended to obtain aqueous mixture (B2).

[0096] [Preparation process for aqueous slurry (C2)] While maintaining the temperatures of the aqueous mixture (A2) and aqueous mixture (B2) at 40°C, 578 kg of aqueous mixture (A2) was added dropwise to 1153.3 kg of aqueous mixture (B2) under stirring conditions and mixed. The resulting mixture was then stirred in a sealed container while being maintained at 120°C for 5 hours to obtain aqueous slurry (C2).

[0097] [Preparation process of aqueous mixture (D2)] 19.1 kg of antimony trioxide [Sb2O3] was suspended in 63 kg of a 30.6 mass% aqueous solution of copper nitrate trihydrate [Cu(NO3)2·3H2O], and 4.4 kg of deionized water was added to prepare aqueous mixture (D2).

[0098] [Preparation process for aqueous slurry (E2)] In the aforementioned aqueous slurry (C2) preparation step, immediately after preparing the aqueous slurry (C2) in a sealed container, the aqueous mixture (D2) was added to the aqueous slurry (C2), which was kept agitated at 120°C in the sealed container. The resulting mixture was then agitated in the sealed container at 120°C for 5 hours to obtain aqueous slurry (E2).

[0099] [Drying and firing process of aqueous slurry (E2)] The aqueous slurry (E2) obtained as described above was diluted with 1364 kg of deionized water and then spray-dried using a spray dryer to obtain a dried powder.

[0100] Next, 4 parts by mass of ceramic fiber, 10.50 parts by mass of ammonium nitrate, and 9.25 parts by mass of deionized water were added to 100 parts by mass of the obtained powder and kneaded. The mixture was then extruded into a cylindrical shape with a diameter of 5 mm and a height of 6 mm to obtain a molded body.

[0101] Next, the resulting molded body was subjected to a temperature and humidity control treatment, in which it was dried for 3 hours at a temperature of 90°C and a relative humidity of 35%. After that, the precursor of the catalyst for methacrylic acid production was loaded into a firing apparatus having the configuration described above.

[0102] During the firing process, a pre-firing treatment was performed in a firing apparatus under a nitrogen atmosphere at 228°C for 17 hours, followed by holding at 250°C for 0.5 hours.

[0103] A mixed gas (water content 1.5 vol%) containing outside air and steam for use in firing was prepared by performing the following steps (a) to (d) using a firing apparatus having the configuration already described, and supplied to the firing furnace. (i) Using a compressor, outside air containing 2.5% by volume of moisture was taken in and compressed. (b) Compressed outside air was sent to a dehumidifier via line A (first piping) and dehumidified in a dehumidifier filled with activated alumina. (h) The outside air, after dehumidification by the dehumidifier, was sent via line B (second piping) to a heater equipped with an electric heater, where it was heated to 80°C. The dehumidified and heated outside air was then circulated through line C (third piping). (ii) Steam generated by the steam generator was circulated through line D (the fourth pipe) and mixed with the dehumidified and heated outside air circulating through line C to prepare a mixed gas containing outside air with 1.5 volume% moisture and steam, which was then circulated to the firing furnace A via line C.

[0104] [Production of heteropoly acid compounds (9)] A heteropoly acid compound (9), which is a catalyst for the production of metatacrylic acid, was obtained by performing a calcination process in which the mixed gas was supplied to calcination furnace A at 390°C for 4 hours, followed by supplying nitrogen gas to the calcination apparatus and maintaining the temperature at 435°C for 4 hours.

[0105] [Activity test of heteropoly acid compounds (9)] The activity test was conducted using the same procedure as in the [activity test for heteropoly acid compound (1)] adopted in Reference Example 1 above, except that heteropoly acid compound (9) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 2.

[0106] (Example 2) In Example 1, the same procedure as in Example 1 was performed except that when preparing the mixed gas (water content 1.5 vol%) for use in calcination, outside air containing 3.1 vol% moisture was taken in and compressed using a compressor, thereby obtaining a heteropoly acid compound (10) which is a catalyst for the production of metatacrylic acid.

[0107] [Activity test of heteropoly acid compound (10)] The activity test was conducted using the same procedure as in Reference Example 1 [Activity Test of Heteropoly Acid Compound (1)], except that heteropoly acid compound (10) was used instead of heteropoly acid compound (1). The results of the activity test are shown in Table 2.

[0108] [Table 2] [Explanation of Symbols]

[0109] 1 Manufacturing equipment 10. Firing apparatus 11a First piping (Line A) 11b Second piping (line B) 11c Third piping (line C) 11d (11da, 11db) Fourth piping (line D) 12 Compressor 13 Dehumidifier 14 Heater 15. Firing furnace 16. Steam generator 20 Slurry preparation section 30 Drying section 40 Mixing and extrusion molding section

Claims

1. A compressor that takes in outside air and compresses it, A dehumidifier is connected to the compressor by a first pipe and dehumidifies the outside air compressed by the compressor, A heater is connected to the dehumidifier by a second pipe, and the heater heats the outside air from which the dehumidifier has removed moisture. A calcination furnace is connected to the heater by a third pipe, to which heated outside air from the heater is supplied, and to calcine a precursor of a methacrylic acid production catalyst containing a heteropoly acid compound containing phosphorus and molybdenum, A steam generator is connected to the third pipe by a fourth pipe, and supplies steam to the third pipe to adjust the water content of the mixed gas supplied to the firing furnace to 0.1 to 2.0 volume percent. A firing apparatus equipped with the following features.

2. The firing apparatus according to claim 1, wherein the heater is a device that heats the outside air supplied from the dehumidifier to 60 to 200°C.

3. A catalyst for methacrylic acid production apparatus comprising the calcination apparatus described in claim 1 or 2, A slurry preparation unit for preparing a raw material slurry containing phosphorus and molybdenum, A drying unit connected to the slurry preparation unit, which dries the raw material slurry prepared in the slurry preparation unit to form a powder, A kneading and extrusion molding unit connected to the drying unit, which kneads and extrudes the powder dried by the drying unit to form a precursor for a catalyst for methacrylic acid production, A calcination apparatus connected to the extrusion molding section, which calcines the precursor of the methacrylic acid production catalyst formed in the kneading and extrusion molding section to produce a methacrylic acid production catalyst, and A catalyst manufacturing apparatus for methacrylic acid production, equipped with the following features.

4. A slurry preparation step for preparing a raw material slurry containing phosphorus and molybdenum, A drying step in which the raw material slurry is dried to form a powder, A kneading and extrusion process to knead the aforementioned powder and extrude it to form a precursor for a catalyst for methacrylic acid production, The process includes a calcination step of calcining the precursor of the catalyst for methacrylic acid production to obtain the catalyst for methacrylic acid production, The calcination process comprises a compressor that takes in outside air and compresses it, a dehumidifier connected to the compressor by a first pipe and dehumidifies the outside air compressed by the compressor, a heater connected to the dehumidifier by a second pipe and heats the outside air dehumidified by the dehumidifier, a calcination furnace connected to the heater by a third pipe and supplied with the outside air heated by the heater, which calcines a precursor of a methacrylic acid production catalyst containing a heteropoly acid compound containing phosphorus and molybdenum, and the third pipe A method for producing a catalyst for methacrylic acid, comprising a firing apparatus that includes a steam generator connected by a fourth pipe and supplying steam to the third pipe, wherein steam is supplied from the steam generator to the third pipe to form a mixed gas containing outside air and steam, and the precursor of the catalyst for methacrylic acid production is fired to produce a catalyst for methacrylic acid while adjusting the water content of the mixed gas supplied to the firing furnace to 0.1 to 2.0 volume percent.

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