JP5424914B2 - Catalyst for producing methacrylic acid, method for producing the same, and method for producing methacrylic acid - Google Patents

Description

  The present invention relates to a method for producing a catalyst for producing methacrylic acid (hereinafter also simply referred to as “catalyst”) for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, and a catalyst produced by this method. And a method for producing methacrylic acid using the catalyst.

  As a methacrylic acid production catalyst for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, a heteropolyacid catalyst containing molybdenum and phosphorus is known. As such a heteropolyacid catalyst, a proton type heteropolyacid whose counter cation is a proton, and one obtained by substituting a part of the proton with an alkali metal such as cesium, rubidium, potassium, etc., are known. (Hereinafter, the proton type heteropolyacid is also simply referred to as “heteropolyacid”, and the proton type heteropolyacid and / or the heteropolyacid salt is also referred to as “heteropolyacid (salt)”). Proton type heteropolyacids are water-soluble, but heteropolyacid salts in which protons are substituted with alkali metals generally have poor solubility in water because of the ionic radius of these cations.

For example, Non-Patent Document 1 has the following description regarding the structure of a heteropolyacid (salt).
(A) The heteropolyacid (salt) has a heterogeneous element at the center, and has a mononuclear or binuclear complex ion formed by condensing condensed acid groups while sharing oxygen. Several types of condensation are known, and phosphorus, arsenic, silicon, germanium, titanium, and the like can be the central element.

Patent Document 1 discloses the following catalyst as a heteropolyacid catalyst that improves the selectivity of methacrylic acid from methacrolein.
(B) An oxide is used as a raw material for the molybdenum and vanadium components during catalyst preparation, and a mixture of catalyst raw material other than potassium, rubidium, cesium and thallium and water is heated to 85 ° C. or higher for 1 to 10 hours, and then mixed. The liquid is cooled to 80 ° C. or higher, and at least one element selected from the group consisting of potassium, rubidium, cesium and thallium is added, and then ammonium nitrate, ammonium carbonate, ammonium bicarbonate, Production of multi-component methacrylic acid containing phosphorus, molybdenum and vanadium, characterized in that after adding at least one compound selected from the group consisting of ammonium sulfate and ammonium hydrogen sulfate, water is removed and the residue is heat treated Catalyst.
On the other hand, Patent Documents 2 to 4 disclose the following catalysts as heteropolyacid catalysts for improving the selectivity of methacrylic acid from isobutane.
(C) A catalyst in which a heteropolyacid (salt) containing molybdenum or phosphorus and containing molybdenum as a central element is reduced by 1 to 6 electrons per molecule of the heteropolyacid (Patent Document 2).
(D) containing phosphorus, arsenic as a central element, molybdenum and vanadium as coordination elements, the ratio of which is 0.5-3 gram atom for the central element and 0.01-2 gram atom for vanadium with respect to 12 gram atom of molybdenum The catalyst containing the heteropolyacid (salt) which is (patent document 3).
(E) A catalyst containing a poorly water-soluble salt of a heteropolyacid and a composite oxide containing phosphorus, molybdenum, and vanadium (Patent Document 4).

JP-A-4-7037 JP-A 63-145249 Japanese Patent Laid-Open No. 02-42032 JP 2001-114726 A

Masayuki Otake, Takeshi Onoda, Catalyst, vol. 18, no. 6 (1976)

  However, the catalysts (b) to (e) still have insufficient selectivity for methacrylic acid as an industrial catalyst, and further improvement in the selectivity of methacrylic acid is desired for use as an industrial catalyst. Yes.

  An object of the present invention is to provide a catalyst for producing methacrylic acid capable of producing methacrylic acid with high selectivity, a method for producing the same, and a method for producing methacrylic acid using the catalyst.

The present invention relates to a phosphorus element, a molybdenum element, an X element (a group consisting of silicon, titanium, germanium, arsenic, antimony and cerium) used in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen. A method for producing a catalyst comprising at least one element selected from the group consisting of an alkali metal element,
(I) adding at least a molybdenum raw material and an X element raw material in water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid;
(Ii) adding an alkali metal compound to the aqueous slurry or aqueous solution to precipitate a heteropolyacid salt that is at least a part of the alkali metal salt of the heteropolyacid;
(Iii) adding a phosphorus raw material to the aqueous slurry in which the heteropolyacid salt is deposited;
(Iv) after adding the phosphorus raw material, maintaining the temperature of the aqueous slurry at 70 ° C. or lower to obtain a dried product by spray drying;
(V) heat-treating the dried product.

  Moreover, this invention is a catalyst for methacrylic acid manufacture manufactured with said manufacturing method. Moreover, this invention is a manufacturing method of methacrylic acid which manufactures methacrylic acid by carrying out the gaseous-phase contact oxidation of methacrolein with molecular oxygen using the catalyst for methacrylic acid manufacturing manufactured by said manufacturing method.

  According to the present invention, methacrylic acid production catalyst capable of producing methacrylic acid with high selectivity by gas phase catalytic oxidation of methacrolein with molecular oxygen, its production method, and methacrylic acid using the methacrylic acid production catalyst The manufacturing method of can be provided.

<Catalyst for methacrylic acid production and production method thereof>
The present invention is a catalyst comprising a phosphorus element, a molybdenum element, an X element (at least one element selected from the group consisting of silicon, titanium, germanium, arsenic, antimony and cerium) and an alkali metal element. It is preferable to have the composition represented by 1).

Mo _a P _b V _c Cu _d X _e Y _f Z _g O _h (1)
(In the formula, Mo, P, V, Cu and O are element symbols indicating molybdenum, phosphorus, vanadium, copper and oxygen, respectively. X is selected from the group consisting of silicon, titanium, germanium, arsenic, antimony and cerium. Y represents at least one element, Y represents at least one element selected from the group consisting of bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium and lanthanum; Represents at least one element selected from the group consisting of potassium, rubidium and cesium, where a, b, c, d, e, f, g and h represent the atomic ratio of each element, and when a = 12. B = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0.1-3, f = 0-3, g = 0.01-3, h Is Serial is an atomic ratio of oxygen required to satisfy the valence of each element.)
The catalyst of the present invention is produced by a production method having the following steps.
Step (i): At least a molybdenum raw material and an X element raw material are added in water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid (preparation step).
Step (ii): An alkali metal compound is added to the aqueous slurry or aqueous solution to precipitate a heteropolyacid salt in which at least a part of the heteropolyacid is an alkali metal salt (precipitation step).
Step (iii): A phosphorus raw material is added to the aqueous slurry in which the heteropolyacid salt is deposited (phosphorus addition step).
Step (iv): A step of adding a phosphorus raw material and then maintaining the temperature of the aqueous slurry at 70 ° C. or lower to obtain a dried product by spray drying (drying step).
Step (v): a step of heat-treating the dried product (heat treatment step).

  Furthermore, you may have the process (shaped process) which shapes the said dried material.

  The present inventors use X element and phosphorus element as the central elements of the heteropolyacid (salt) contained in the catalyst, add the X element raw material before precipitation of the heteropoly acid salt, and add the phosphorus raw material to the heteropoly acid salt. It was found that the catalyst performance is improved by adding after the precipitation and then performing spray drying while maintaining the temperature of the slurry below a certain level to obtain a dried product.

  The reason for this is that the X element present in the heteropolyacid (salt) contained in the catalyst affects the selectivity of methacrylic acid, and the raw material for the X element is added before precipitation of the heteropolyacid salt. Is added after the precipitation of the heteropolyacid salt to increase the proportion of the X element present in the heteropolyacid (salt), and the slurry after the addition of the phosphorus raw material is kept below a certain temperature and spray dried. Thus, it is presumed that this is because the amount of heteropolyacid (salt) produced with phosphorus as a central element can be appropriately controlled.

  The catalyst includes a proton-type heteropoly acid whose counter cation of the heteropoly acid is all hydrogen (proton), and a part or all of the proton substituted with an alkali metal such as cesium, rubidium, potassium, etc., to form a heteropoly acid salt Exists. Proton-type heteropolyacid has the effect of supplying oxygen to methacrolein and oxidizing it to methacrylic acid. Heteropolyacid salt has an oxidation reaction after methacrolein is oxidized to methacrylic acid. This has the effect of suppressing the sequential oxidation reaction. On the other hand, in the completed catalyst, there are impurities other than the heteropolyacid (salt) that could not be the heteropolyacid (salt).

  Although the role of impurities that could not become this heteropolyacid (salt) is not clear, the element X contributes to the improvement of the selectivity of methacrylic acid by constituting the heteropolyacid (salt), and the ratio that exists as an impurity As the value increases, the selectivity of methacrylic acid decreases. Therefore, the selectivity of methacrylic acid can be improved by increasing the proportion of the X element present in the heteropolyacid (salt).

  In the present invention, as the raw material for the central element, an alkali metal is added in the presence of the raw material for the X element, and after depositing the heteropolyacid salt having the X element as the central element, the phosphorus raw material is added. As a result, a heteropoly acid salt having the X element as the central element is formed in preference to the heteropoly acid (salt) having the phosphorus element as the central element, so that the proportion of the X element present as an impurity is reduced, and phosphorus It is speculated that by controlling the slurry temperature after the addition of the raw material and performing drying, the amount of heteropolyacid (salt) containing phosphorus as a central element is controlled, and the selectivity of methacrylic acid is improved.

[Preparation process]
In this step, at least a molybdenum raw material and an X element raw material are added to water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid. The phosphorus raw material is preferably not added in this step, but may be added as long as the phosphorus raw material has an amount of supplying a phosphorus element having a mole number smaller than the mole number of the X element in the X element raw material. In addition, molybdenum raw material, phosphorus raw material, X element raw material and raw materials other than alkali metal compounds (in the case of producing a catalyst having a composition represented by the formula (1), vanadium raw material, copper raw material and Y element raw material) Etc. may be added at any stage of the preparation process, the precipitation process and the phosphorus addition process. What is necessary is just to determine the compounding quantity of the raw material to add suitably according to the composition of the target catalyst.

  Examples of the raw material used include nitrates, carbonates, acetates, ammonium salts, oxides, halides and the like of each element. Examples of the molybdenum raw material include ammonium paramolybdate, molybdenum trioxide, molybdic acid, and molybdenum chloride. Examples of the copper raw material include copper nitrate, copper oxide, copper carbonate, and copper acetate.

  For preparing the aqueous slurry or aqueous solution, a method of adding a raw material of each element to water and stirring while heating is simple and preferable. The amount of water used in the preparation step is preferably such that the total mass of raw materials used in the preparation step: the mass of water used in the preparation step = 1: 0.5 to 1:15, and 1: 1 to 1: An amount of 2 is more preferred. By setting the amount of water used in the preparation step within this range, the selectivity of methacrylic acid is improved. Although the role of the amount of water used in the preparation process is not clear, the physical structure of the heteropolyacid salt formed in the next precipitation process is to suppress the sequential oxidation reaction by improving the concentration of the aqueous slurry. It is estimated that the structure becomes optimal and the selectivity of methacrylic acid is improved. The heating temperature of the aqueous slurry or aqueous solution is preferably 80 to 130 ° C, more preferably 90 to 130 ° C.

  When the pH of the aqueous slurry or aqueous solution to be prepared is high, it is preferable to select each raw material so as to contain a large amount of nitrate radicals. The pH of the prepared aqueous slurry or aqueous solution is preferably 4 or less, and more preferably 2 or less.

[Precipitation process]
In this step, an alkali metal compound is added to the aqueous slurry or aqueous solution obtained in the preparation step to precipitate a heteropolyacid salt in which at least a part of the heteropolyacid is an alkali metal salt. It is preferred to cool the aqueous slurry or aqueous solution before adding the alkali metal compound. The cooling temperature is preferably 20 to 80 ° C, more preferably 40 to 70 ° C.

The heteropolyacid salt to be deposited may have a Keggin type structure or a structure other than Keggin type such as Dawson type, but preferably has a Keggin type structure. When the heteropoly acid salt to be precipitated is Keggin type, the selectivity of methacrylic acid is further improved. In order to precipitate the heteropolyacid salt having a Keggin type structure, for example, molybdenum trioxide is used as a molybdenum raw material, and the pH in the precipitation step is adjusted to 3 or less. The structure of the deposited heteropolyacid salt can be confirmed by measuring the heteropolyacid salt separated by filtration or the like and drying it by infrared absorption analysis. In the case of a heteropolyacid salt having a Keggin structure, for example, when the X element is arsenic, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 960, 890, 870, and 780 cm ⁻¹ . In the case of a heteropolyacid salt having a Dawson structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 930, 870, and 720 cm ⁻¹ .

  Examples of the alkali metal compound include a cesium compound, a potassium compound, and a rubidium compound. In the case of producing a catalyst having the composition represented by the formula (1), it becomes a raw material for the Z element. From the viewpoint of thermal stability, a cesium compound is preferable. Examples of the cesium compound include cesium bicarbonate, cesium nitrate, and cesium oxide. What is necessary is just to determine the addition amount of an alkali metal compound suitably according to the composition of the target catalyst.

  The alkali metal compound is preferably added in the form of a solution or slurry of an alkali metal compound dissolved or suspended in a solvent. Examples of the solvent include water, ethyl alcohol, acetone and the like, but it is preferable to use the same water as the aqueous slurry or aqueous solution.

  The addition rate of the alkali metal compound solution or slurry is a ratio of 0.1 to 80 parts by mass of the alkali metal compound solution or slurry per minute when the total amount of the alkali metal compound solution or slurry is 100 parts by mass. It is preferable to add at a ratio of 1 to 20 parts by mass.

  The aqueous slurry to which the alkali metal compound has been added may be subsequently subjected to the phosphorus addition step or may be allowed to stand, but is preferably stirred. As the agitator, a rotary agitator such as a rotary blade agitator, a high-speed rotary shear agitator (homogenizer, etc.), a pendulum linear motion agitator, a shaker that shakes the whole container, an ultrasonic wave, or the like was used. A known stirring device such as a vibration type stirrer can be used. The rotational speed of the stirring blade or the rotary blade in the rotary stirring device may be appropriately adjusted in consideration of the shape of the container, stirring blade, baffle plate, etc., the amount of liquid, etc., to the extent that inconvenience such as liquid scattering does not occur. . Stirring may be performed either continuously or intermittently, but is preferably performed continuously.

  In order to adjust the pH of the aqueous slurry to be prepared, a nitric acid compound or an ammonia compound may be added. Nitric acid compounds include nitric acid and ammonium nitrate. Examples of the ammonia compound include aqueous ammonia, ammonium hydrogen carbonate, ammonium carbonate, and ammonium nitrate. The pH of the prepared aqueous slurry or aqueous solution is preferably 4 or less, and more preferably 2 or less.

  20-80 degreeC is preferable and the temperature of the aqueous slurry at the time of stirring has more preferable 40-70 degreeC. Moreover, 5 to 60 minutes are preferable and, as for the stirring time after adding an alkali metal compound, 10 to 30 minutes are more preferable.

  Moreover, 20-80 degreeC is preferable and, as for the temperature of the aqueous slurry or aqueous solution at the time of standing, 40-70 degreeC is more preferable. The time for standing still is preferably 5 to 60 minutes, and more preferably 10 to 30 minutes.

[Phosphorus addition process]
In this step, the phosphorus raw material is added to the aqueous slurry in which the heteropolyacid salt is precipitated. Examples of the phosphorus raw material include orthophosphoric acid, phosphorus pentoxide, and ammonium phosphate. What is necessary is just to determine the addition amount of a phosphorus raw material suitably according to the composition of the target catalyst.

  The phosphorus raw material may be added as it is, or may be added in the form of a solution or slurry of the phosphorus raw material dissolved or suspended in a solvent. In the case of using a solvent, examples of the solvent include water, ethyl alcohol, and acetone, but it is preferable to use the same water as the aqueous slurry or aqueous solution. The concentration of the phosphorus raw material is preferably 5 to 85% by mass, and more preferably 15 to 35% by mass.

  In the present invention, the aqueous slurry to which the phosphorus raw material is added is kept at 70 ° C. or lower and subjected to a drying process by spray drying. In this case, the phosphorus raw material may be added and the drying process may be performed immediately, but spray drying may be performed after a predetermined time has elapsed. When maintaining for a certain period of time, the aqueous slurry is preferably stirred. As the agitator, a rotary agitator such as a rotary blade agitator, a high-speed rotary shear agitator (homogenizer, etc.), a pendulum linear motion agitator, a shaker that shakes the whole container, an ultrasonic wave, or the like was used. A known stirring device such as a vibration type stirrer can be used. The rotational speed of the stirring blade or the rotary blade in the rotary stirring device may be appropriately adjusted in consideration of the shape of the container, stirring blade, baffle plate, etc., the amount of liquid, etc., to the extent that inconvenience such as liquid scattering does not occur. . Stirring may be performed either continuously or intermittently, but is preferably performed continuously.

  The temperature of the aqueous slurry at the time of stirring is 70 degrees C or less, 10-60 degreeC is preferable and 20-50 degreeC is more preferable. Moreover, 5 to 60 minutes are preferable and, as for the stirring time after adding a phosphorus raw material, 10 to 30 minutes are more preferable.

  Moreover, when standing aqueous slurry, the temperature is 70 degrees C or less, 10-60 degreeC is preferable and 20-50 degreeC is more preferable. The time for standing still is preferably 5 to 60 minutes, and more preferably 10 to 30 minutes. The shorter the standing time, the better, but it is preferably within 2 days.

[Drying process]
In this step, a dried product is obtained by drying an aqueous slurry containing all raw materials. As a drying method in the present invention, a spray drying method is used in order to prevent heat from being applied to the aqueous slurry containing molybdenum and phosphorus raw materials for a long time. Conditions such as the model used and the drying temperature are not particularly limited, but it is preferable to perform drying so that the time during which heat is applied to the slurry to be dried is shortened. At this time, the drying temperature is appropriately selected depending on the desired shape and size of the dried product.

The heteropolyacid (salt) in the dried product may have a Keggin type structure or a structure other than a Keggin type such as Dawson type, but preferably has a Keggin type structure. When the heteropolyacid (salt) in the dried product has a Keggin structure, the reaction rate of methacrolein is improved and the yield of methacrylic acid is increased. To obtain a dried product of Keggin-type heteropolyacid (salt), for example, the Keggin-type heteropolyacid salt is precipitated in the precipitation step by the above method, and the pH in the phosphorus addition step and the drying step is adjusted to 3 or less. The method of doing is mentioned. The structure of the heteropolyacid (salt) in the dried product can be confirmed by measurement by infrared absorption analysis. In the case of a heteropolyacid (salt) having a Keggin structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1060, 960, 870, and 780 cm ⁻¹ . On the other hand, in the case of a heteropolyacid (salt) having a Dawson type structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1040, 1020, 930, 720, and 680 cm ⁻¹ .

[Shaping process]
The obtained dried product may be heat-treated as it is, but the dried product may be shaped and the obtained shaped product may be heat-treated. Moreover, you may shape what heat-processed the dried material by the heat processing process mentioned later. Examples of the apparatus used for shaping the dried product or the heat-treated dried product include known powder molding machines such as a tableting machine, an extrusion molding machine, and a rolling granulator. There is no restriction | limiting in particular as a shape of a shaped article, Arbitrary shapes, such as spherical shape, ring shape, cylindrical shape, star shape, are mentioned.

[Heat treatment process]
In this step, the catalyst can be obtained by heat-treating the dried product or the shaped product of the dried product. The heat treatment conditions are not particularly limited, and known heat treatment conditions can be applied. The heat treatment is usually performed at 200 to 500 ° C., preferably 300 to 450 ° C., for 0.5 hours or more, preferably 1 to 40 hours under the flow of an oxygen-containing gas such as air and / or an inert gas. .

The catalyst for producing methacrylic acid according to the present invention as described above is a catalyst capable of producing methacrylic acid in high yield by gas phase catalytic oxidation of methacrolein with molecular oxygen.

<Method for producing methacrylic acid>
The method for producing methacrylic acid of the present invention is characterized in that methacrylic acid is produced by gas phase catalytic oxidation of methacrolein with molecular oxygen using the methacrylic acid production catalyst of the present invention.

  Specifically, methacrylic acid is produced by bringing a raw material gas containing methacrolein and molecular oxygen into contact with the catalyst of the present invention. This reaction is usually carried out in a fixed bed. Further, the catalyst layer may be one layer or two or more layers. The catalyst for producing methacrylic acid may be supported on a carrier or may be a mixture of other additive components.

  The concentration of methacrolein in the raw material gas can be varied within a wide range, preferably 1 to 20% by volume, more preferably 3 to 10% by volume. The methacrolein may contain a small amount of impurities such as water and lower saturated aldehyde that do not substantially affect this reaction.

  The concentration of molecular oxygen in the raw material gas is preferably 0.4 to 4 mol, more preferably 0.5 to 3 mol, per 1 mol of methacrolein. The molecular oxygen source is preferably air from the viewpoint of economy. If necessary, a gas or the like enriched with molecular oxygen by adding pure oxygen to air may be used.

  The source gas may be obtained by diluting methacrolein and a molecular oxygen source with an inert gas such as nitrogen or carbon dioxide. Further, water vapor may be added to the source gas. By performing the reaction in the presence of water, methacrylic acid can be obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably from 0.1 to 50% by volume, particularly preferably from 1 to 40% by volume.

  The contact time between the raw material gas and the catalyst for producing methacrylic acid is preferably 1.5 to 15 seconds, and more preferably 2 to 5 seconds.

  The reaction pressure is preferably atmospheric pressure (0.1 MPa-G) to several atmospheres (for example, 1 MPa-G). The reaction temperature is preferably 200 to 450 ° C, particularly preferably 250 to 400 ° C.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples. “Parts” in Examples and Comparative Examples means parts by mass.

  The catalyst composition was calculated by analyzing components dissolved in aqueous ammonia by ICP emission analysis and atomic absorption spectrometry.

The analysis of the raw material gas and the product was performed using gas chromatography. From the results of gas chromatography, the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined by the following formula.
Reaction rate of methacrolein (%) = (B / A) × 100
Methacrylic acid selectivity (%) = (C / B) × 100
Methacrylic acid yield (%) = (C / A) × 100
In the formula, A is the number of moles of methacrolein supplied, B is the number of moles of reacted methacrolein, and C is the number of moles of methacrylic acid produced.

[Example 1]
In 400 parts of pure water, 100 parts of molybdenum trioxide, 3.1 parts of ammonium metavanadate, 7.5 parts of 60% by mass arsenic acid and 1.5 parts of copper (II) nitrate trihydrate are dissolved and stirred. The mixture was heated to 95 ° C., and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. After cooling to 50 ° C., 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water and 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water were added dropwise while stirring with a rotary blade stirrer, and the heteropolyacid After the salt was precipitated, the mixture was stirred for 15 minutes. The precipitated heteropolyacid salt had a Keggin type structure. To this aqueous slurry, 7.3 parts of an 85 mass% phosphoric acid aqueous solution was added dropwise, and the mixture was further stirred at 50 ° C for 15 minutes.

  The obtained aqueous slurry was kept at 50 ° C. and dried by spray drying. The heteropolyacid (salt) in the obtained dried product had a Keggin type structure. This dried product was shaped by pressure molding, and the obtained shaped product was heat-treated at 380 ° C. for 5 hours under air flow. The elemental composition other than oxygen (hereinafter the same) of the obtained catalyst was as follows.

Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
The catalyst was filled in a reaction tube, and a raw material gas containing 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of steam, and 55% by volume of nitrogen was passed at a reaction temperature of 290 ° C. and a contact time of 3.6 seconds. The product was collected and analyzed by gas chromatography to determine methacrolein reaction rate, methacrylic acid selectivity, and methacrylic acid yield. The results are shown in Table 1.

[Example 2]
An aqueous slurry in which an 85% by mass phosphoric acid aqueous solution was dropped was heated to 60 ° C., and stirred for 15 minutes while maintaining the temperature at 60 ° C., and then dried in the same manner as in Example 1 except that spray drying was performed. It was. In addition, the heteropoly acid salt precipitated in the middle had a Keggin type structure, and the heteropoly acid (salt) in the dried product had a Keggin type structure. A catalyst was obtained from this dried product in the same manner as in Example 1. The elemental composition of the obtained catalyst was as follows.

Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
In the same manner as in Example 1, methacrylic acid was produced. The results are shown in Table 1.

[Comparative Example 1]
The dried slurry was treated in the same manner as in Example 1 except that the 85% by mass phosphoric acid aqueous solution was dropped to 90 ° C. and the mixture was stirred for 15 minutes while maintaining the temperature at 90 ° C. and then spray-dried. Obtained. In addition, the heteropoly acid salt precipitated in the middle had a Keggin-type structure, and the heteropolyacid (salt) in the dried product had a Keggin-type structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
A dried product was obtained in the same manner as in Example 1 except that the aqueous slurry after dropping the 85 mass% phosphoric acid aqueous solution was heated to 101 ° C and evaporated to dryness with stirring. In addition, the heteropoly acid salt precipitated in the middle had a Keggin-type structure, and the heteropolyacid (salt) in the dried product had a Keggin-type structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

Example 3
A catalyst was prepared in the same manner as in Example 1 except that 3.1 parts of ammonium metavanadate was changed to 2.4 parts of vanadium pentoxide. The precipitated heteropoly acid salt had a Keggin type structure, and the heteropoly acid (salt) in the dried product had a Keggin type structure. The elemental composition of the obtained catalyst was as follows.

Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
A methacrylic acid was produced in the same manner as in Example 1 except that this catalyst was used. The results are shown in Table 1.

[Comparative Example 3]
The dried slurry was treated in the same manner as in Example 3 except that the 85% by mass aqueous phosphoric acid solution was heated to 90 ° C. and stirred for 15 minutes while maintaining the temperature at 90 ° C., followed by spray drying. Obtained. In addition, the heteropoly acid salt precipitated in the middle had a Keggin-type structure, and the heteropolyacid (salt) in the dried product had a Keggin-type structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
A dried product was obtained in the same manner as in Example 3, except that the aqueous slurry in which the 85% by mass phosphoric acid aqueous solution was dropped was heated to 101 ° C. and evaporated to dryness while stirring. The precipitated heteropolyacid salt had a Keggin structure, and the heteropolyacid (salt) in the dried product had a Keggin structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.45 P _1.1 As _0.55 Cu _0.11 Cs _1.2
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

Example 4
200 parts of pure water, 100 parts of molybdenum trioxide, 6.1 parts of ammonium metavanadate, 11.0 parts of 60% by mass arsenic acid, 7.5 parts of cerium (III) nitrate hexahydrate and 3 parts of copper (II) nitrate 3.4 parts of the hydrate was dissolved, heated to 95 ° C. while stirring, and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. After cooling to 50 ° C., stirring with a rotary blade stirrer, 1.2 parts of cesium bicarbonate dissolved in 22 parts of pure water, 3.1 parts of rubidium nitrate dissolved in 6.0 parts of pure water, and 16 pure water After 7.2 parts of ammonium carbonate dissolved in the part was added dropwise to precipitate the heteropolyacid salt, the mixture was stirred for 15 minutes. The precipitated heteropolyacid salt had a Keggin type structure. To this solution, 4.0 parts of 85 mass% phosphoric acid aqueous solution was added dropwise, and the mixture was further stirred at 50 ° C for 15 minutes.

  The obtained aqueous slurry was kept at 50 ° C. and dried by spray drying. The heteropolyacid (salt) in the obtained dried product had a Keggin type structure. This dried product was shaped by pressure molding, and the obtained shaped product was heat-treated at 380 ° C. for 5 hours under air flow. The elemental composition of the obtained catalyst was as follows.

Mo ₁₂ V _0.9 P _0.6 As _0.8 Ce _0.3 Cu _0.24 Cs _1.0 Rb _0.1
A methacrylic acid was produced in the same manner as in Example 1 except that this catalyst was used. The results are shown in Table 1.

[Comparative Example 5]
The dried slurry was treated in the same manner as in Example 4 except that the 85% by mass phosphoric acid aqueous solution was dropped to 90 ° C. and the slurry was stirred for 15 minutes while maintaining the temperature at 90 ° C. and then spray-dried. Obtained. In addition, the heteropoly acid salt precipitated in the middle had a Keggin-type structure, and the heteropolyacid (salt) in the dried product had a Keggin-type structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.9 P _0.6 As _0.8 Ce _0.3 Cu _0.24 Cs _1.0 Rb _0.1
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 6]
A dried product was obtained in the same manner as in Example 4, except that the aqueous slurry in which the 85 mass% phosphoric acid aqueous solution was dropped was heated to 101 ° C and evaporated to dryness while stirring. In addition, the heteropolyacid salt precipitated in the middle had a Keggin type structure. The heteropolyacid (salt) in the obtained dried product had a Keggin type structure. This dried product was treated in the same manner as in Example 1 to obtain a catalyst. The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.9 P _0.6 As _0.8 Ce _0.3 Cu _0.24 Cs _1.0 Rb _0.1
Using this catalyst, methacrylic acid was produced in the same manner as in Example 1. The results are shown in Table 1.

Claims (5)

Phosphorus element, molybdenum element, X element (selected from the group consisting of silicon, titanium, germanium, arsenic, antimony and cerium) used in the production of methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen A method for producing a catalyst comprising at least one element) and an alkali metal element,
(I) adding at least a molybdenum raw material and an X element raw material in water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid;
(Ii) adding an alkali metal compound to the aqueous slurry or aqueous solution to precipitate a heteropolyacid salt in which at least a part of the heteropolyacid is an alkali metal salt;
(Iii) adding a phosphorus raw material to the aqueous slurry in which the heteropolyacid salt is deposited;
(Iv) after adding the phosphorus raw material, maintaining the temperature of the aqueous slurry at 70 ° C. or lower to obtain a dried product by spray drying;
(V) A method for producing a catalyst for producing methacrylic acid, comprising a step of heat-treating the dried product.   The method for producing a catalyst for producing methacrylic acid according to claim 1, wherein the heteropolyacid and the heteropolyacid salt in the dried product have a Keggin type structure.   The method for producing a catalyst for methacrylic acid production according to claim 1 or 2, wherein the dried product is shaped and the obtained shaped product is heat-treated.   The catalyst for methacrylic acid manufacture manufactured with the manufacturing method of the catalyst for methacrylic acid manufacture in any one of Claims 1-3.   Using the methacrylic acid production catalyst produced by the method for producing a methacrylic acid production catalyst according to any one of claims 1 to 3, methacrylic acid is produced by gas phase catalytic oxidation of methacrolein with molecular oxygen. A method for producing methacrylic acid.