JP2010119988A - Catalyst for manufacturing methacrylic acid and method of manufacturing the same, and method of manufacturing methacrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst for manufacturing a methacrylic acid, which can manufacture the methacrylic acid in good yield, a method of manufacturing the same, and a method of manufacturing the methacrylic acid using the catalyst. <P>SOLUTION: The method comprises the steps of adding at least a part of a molybdenum raw material and a phosphorus raw material under water, of preparing an aqueous solution or an aqueous slurry containing a heteropoly acid, of adding an alkali metal compound to the aqueous slurry or the aqueous solution, and of adding the remaining molybdenum raw material after at least a part of the heteropoly acid precipitates a heteropolyacid salt which has turned to an alkali metal salt, to manufacture the catalyst containing molybdenum, phosphorus, and an alkali metal. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 a heteropolyacid salt in which a part of the proton is substituted with an alkali metal such as cesium, rubidium, potassium, and the like are known (hereinafter referred to as “heteropolyacid catalyst”). 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.

The structure of the heteropolyacid (salt) includes the following description.
(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 forms are known, and phosphorus, arsenic, silicon, germanium, titanium, and the like can be the central element (Non-Patent Document 1).

Moreover, as a method for improving the selectivity of methacrylic acid from methacrolein using a heteropolyacid catalyst, for example, the following catalysts have been proposed.
(B) Since the heteropolyacid has high acidity, when it is used alone as a catalyst, the selectivity and yield of methacrylic acid are lowered. Then, it is set as the catalyst which adjusted the acidity by partially neutralizing a part of proton (nonpatent literature 2).
(C) 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 And a catalyst containing a heteropolyacid and / or a salt thereof (Patent Document 1).
(D) a step of mixing at least a catalyst raw material in a solvent to obtain a catalyst raw material mixed solution, a step of filtering the solid content contained in the catalyst raw material mixed solution, and a step of drying the filtered solid content under reduced pressure A catalyst for producing methacrylic acid is produced by a method comprising a step of firing the obtained dried product (Patent Document 2).
(E) When mixing a solution or slurry containing molybdenum, phosphorus and vanadium (solution A), a solution or slurry containing ammonium root (solution B), and a solution or slurry containing potassium, rubidium or cesium (solution C) A catalyst for producing methacrylic acid is produced by a method characterized by mixing the B liquid in the A liquid, the C liquid, or the mixed liquid of the A liquid and the C liquid in 0.1 to 15 minutes (Patent Document 3). .
Japanese Patent Laid-Open No. 02-42032 JP 2006-81974 A International Publication No. 04/004900 pamphlet Masayuki Otake, Takeshi Onoda, Catalyst, vol. 18, no. 6 (1976) Okuhara, et. al, J. et al. Catal, 121 (1983)

  However, the catalyst obtained by the methods (b) to (e) still has insufficient methacrylic acid yield as an industrial catalyst, and further improvement in methacrylic acid yield is desired for use as an industrial catalyst. ing.

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

That is, the present invention is a method for producing a catalyst containing molybdenum, phosphorus and an alkali metal, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen.
(I) adding at least a part of a molybdenum raw material and a phosphorus raw material in water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid; and (ii) adding an alkali metal compound to the aqueous slurry or aqueous solution, Depositing a heteropolyacid salt in which at least a part of the heteropolyacid is an alkali metal salt;
(Iii) adding the remaining molybdenum raw material to the aqueous slurry in which the heteropolyacid salt is precipitated;
(Iv) drying an aqueous slurry or aqueous solution containing all raw materials to obtain a dried product;
(V) A method for producing a catalyst for producing methacrylic acid, comprising a step of heat-treating the dried product.

  Moreover, this invention is a catalyst for methacrylic acid manufacture manufactured by said method.

  Furthermore, the present invention is a method for producing methacrylic acid in which methacrolein is vapor-phase contact oxidized with molecular oxygen using the above-mentioned catalyst for methacrylic acid production.

  According to the present invention, a catalyst for producing methacrylic acid capable of producing methacrylic acid in a high yield by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, a production method thereof, and methacrylic acid using the catalyst for producing methacrylic acid The manufacturing method of can be provided.

<Catalyst for methacrylic acid production and production method thereof>
The present invention is a catalyst containing a phosphorus element, a molybdenum element and an alkali metal element, and preferably has a composition represented by the following formula (1).

Mo _a P _b V _c Cu _d X _e Y _f O _g (1)
(In the formula, Mo, P, V, Cu and O are element symbols indicating molybdenum, phosphorus, vanadium, copper and oxygen, respectively. X is at least one selected from the group consisting of potassium, rubidium and cesium. Y represents iron, cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin, lead, arsenic, antimony And at least one element selected from the group consisting of bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium, tellurium, lanthanum and cerium, a, b, c, d, e, f and g are The atomic ratio of each element is represented. When a = 12, b = 0.5-3, c = 0.01-3 d = 0.01~2, e = 0.01~3, a f = 0 to 3, g is the the atomic ratio of oxygen required to satisfy the atomic ratio of each element.)
The catalyst of the present invention is produced by a production method having the following steps.
Step (i): At least a part of the molybdenum raw material and the phosphorus raw material are added to 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): The remaining molybdenum raw material is added to the aqueous slurry in which the heteropolyacid salt is precipitated (molybdenum addition step).
Step (iv): An aqueous slurry or aqueous solution containing all raw materials is dried to obtain a dried product (drying step).
Step (v): The dried product is heat treated (heat treatment step).

  Furthermore, you may have the process (molding process) of shaping the said dried material.

[Preparation process]
In this step, an aqueous slurry or aqueous solution containing a heteropoly acid is prepared by adding at least a part of the molybdenum raw material and the phosphorus raw material to water. That is, in the preparation process, only a part of the molybdenum raw material is added. And after depositing heteropolyacid salt using the obtained slurry or aqueous solution, the remaining molybdenum raw material is added after that. The inventors have thus added the molybdenum raw material separately before and after the precipitation of the heteropolyacid salt, and appropriately adjusted the mass ratio of the molybdenum raw material and the phosphorus raw material to be added in the preparation step. It has been found that can be greatly improved.

  The reason why such an effect appears is presumed as follows. First, the catalyst contains a water-soluble heteropolyacid and a poorly water-soluble heteropolyacid salt, and the heteropolyacid salt has an effect of suppressing a sequential oxidation reaction in the oxidation of methacrolein. That is, the heteropolyacid salt can suppress the sequential oxidation reaction in which carbon monoxide, carbon dioxide, acetic acid, etc. are by-produced by further burning the oxidation reaction after methacrolein is oxidized to methacrylic acid, Due to this effect, the yield of methacrylic acid can be improved. On the other hand, since there are also poorly water-soluble components other than heteropolyacid salts, the amount of heteroatoms relative to the mass of the poorly water-soluble component is not constant, and heteroatoms (phosphorus elements, etc.) present in the poorly water-soluble component in this catalyst The amount of is also considered to affect the yield of methacrylic acid. Therefore, it is considered that the selectivity of methacrylic acid is improved by adjusting the mass ratio of the poorly water-soluble component in the catalyst and the heteroatom ratio contained in the poorly water-soluble component among the heteroatoms contained in the catalyst.

  The ratio of the molybdenum raw material to be added in the preparation step and the molybdenum raw material to be added in the molybdenum addition step can be set as appropriate, but the molybdenum in the molybdenum raw material added in the preparation step and the phosphorus raw material added in the preparation step It is preferable to set the atomic ratio of phosphorus to 6.5: 1 to 9: 1, and more preferably to set 6.5: 1 to 8.0: 1. Within this range, as described later, the mass ratio of the poorly water-soluble component in the catalyst and the ratio of the heteroatom contained in the poorly water-soluble component among the heteroatoms contained in the catalyst can be optimized to produce methacrylic acid. It is considered that a chemical structure effective for the reaction is obtained.

  The raw materials other than the molybdenum raw material, phosphorus raw material and alkali metal compound (for example, in the case of producing a catalyst having the composition represented by the formula (1), vanadium raw material, copper raw material and Y element raw material) etc. You may add in any step of a preparation process, a precipitation process, and a molybdenum 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. However, regarding the molybdenum raw material, the total of the molybdenum raw materials added in the preparation step and the molybdenum addition step is appropriately determined 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 phosphorus raw material include orthophosphoric acid, phosphorus pentoxide, and ammonium phosphate. Examples of the vanadium raw material include ammonium metavanadate and vanadium pentoxide. 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 heating temperature 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 20 to 60 ° 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 type structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1060, 960, 870, and 780 cm ⁻¹ . If the obtained precipitate is a heteropolyacid salt having a Dawson structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1040, 1020, 930, 720, and 680 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 X 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 aqueous slurry or aqueous solution to which the alkali metal compound is added may be subsequently subjected to the molybdenum 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.

  The temperature of the aqueous slurry or aqueous solution during stirring is preferably 20 to 80 ° C, and more preferably 40 to 60 ° C. 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, 40-60 degreeC is more preferable. The time for standing still is preferably 5 to 60 minutes, and more preferably 10 to 30 minutes.

[Molybdenum addition process]
In this step, the remaining molybdenum raw material is added to the aqueous slurry in which the heteropolyacid salt is precipitated. The molybdenum raw material added here may be the same as or different from the molybdenum raw material added in the preparation step.

[Drying process]
In this step, a dry product can be obtained by heating and drying an aqueous slurry or an aqueous solution containing all raw materials. Examples of drying methods include known methods such as drum drying, airflow drying, evaporation to dryness, and spray drying. The drying is usually performed at 120 to 500 ° C., preferably 140 to 350 ° C. until the aqueous slurry or the aqueous solution is dried. The conditions such as the model of the dryer used at this time and the drying temperature are not particularly limited, and can be 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 by the above method in the precipitation step, and the pH in the molybdenum 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 structure, the obtained infrared absorption spectrum has characteristic peaks in the vicinity of 1040, 1020, 930, 720, and 680 cm ⁻¹ .

[Molding 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 molded article, Arbitrary shapes, such as spherical shape, ring shape, cylindrical shape, and star shape, are mentioned.

[Heat treatment process]
In this step, the catalyst can be obtained by heat-treating the dried product or the molded 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. .

  When the mass ratio of the hardly water-soluble component in the catalyst obtained by heat treatment in the heat treatment step is α mass%, and the hetero atom content of the poorly water-soluble component among the hetero atoms contained in the catalyst is β atom%, 65 ≦ It is preferable to satisfy α ≦ 80 and 50 ≦ β ≦ 70. By satisfying these conditions, the mass proportion of the poorly water-soluble component in the catalyst and the proportion of the heteroatom contained in the poorly water-soluble component among the heteroatoms contained in the catalyst are optimized, and effective chemistry for the reaction to produce methacrylic acid. A structure is obtained and the yield of methacrylic acid is greatly improved. As for α, it is more preferable to satisfy 65 ≦ α ≦ 75. As for β, it is more preferable to satisfy 60 ≦ β ≦ 70. α and β can be calculated by the following method.

(Mass ratio of poorly water-soluble component in catalyst)
0.2 g of the catalyst is dissolved in 100 g of pure water at room temperature, subjected to ultrasonic elution treatment, and the water elution part and the water insoluble part are further separated by a centrifuge. The ultrasonic elution treatment is performed at 38 to 45 kHz for 30 minutes. Subsequently, the water-insoluble part is dried and weighed. Then, the water-insoluble portion is regarded as a poorly water-soluble component, and the mass ratio of the poorly water-soluble component in the catalyst is calculated.

(Ratio of heteroatoms contained in poorly water-soluble components among heteroatoms contained in catalyst)
The entire catalyst is dissolved in aqueous ammonia and analyzed by ICP emission spectrometry and atomic absorption spectrometry. Subsequently, the water-insoluble part obtained when calculating the mass ratio of the poorly water-soluble component in the catalyst is dissolved in ammonia water, and similarly analyzed by ICP emission spectrometry and atomic absorption spectrometry. And a water insoluble part is considered as a poorly water-soluble component, and the ratio of the hetero atom contained in a poorly water-soluble component is calculated among the hetero atoms contained in a catalyst.

  The heteroatom contained in the catalyst means a different element at the center of the heteropolyacid (salt), and examples thereof include phosphorus, arsenic, silicon, germanium, and titanium.

  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 from 200 to 450 ° C, particularly preferably from 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,
The yield of methacrylic acid (%) = (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, 64.2 parts of molybdenum trioxide, 2.6 parts of vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid aqueous solution and 1.5 parts of copper nitrate were dissolved, and this was stirred at 95 ° C. The mixture was stirred for 3 hours while maintaining the liquid temperature at 95 ° C. While cooling to 25 ° C., while stirring with a rotary blade stirrer, 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water was added dropwise and stirred at 25 ° C. for 15 minutes to precipitate a heteropolyacid salt. The structure of the precipitated heteropolyacid salt was Keggin type. Thereafter, 35.8 parts of molybdenum trioxide was added and stirred at 50 ° C. for 15 minutes, and 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water was added dropwise and stirred for another 15 minutes.

  The resulting mixture was heated to 101 ° C. and evaporated to dryness with stirring. The structure of the heteropolyacid (salt) in the obtained dried product was Keggin type. The dried product was further dried at 130 ° C. for 16 hours, and then shaped by pressure molding. The obtained shaped product was heat-treated at 380 ° C. for 5 hours under air flow to obtain a catalyst. The elemental composition of the obtained catalyst (except for oxygen, the same shall apply hereinafter) was as follows. Moreover, as a result of calculating the mass and element distribution of the poorly water-soluble component at this time, they were α = 68.5 mass% and β = 66.4 atomic%.

Mo ₁₂ V _0.5 P _1.0 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 obtain methacrolein reaction rate, methacrylic acid selectivity and methacrylic acid yield. The results are shown in Table 1.

[Example 2]
In 400 parts of pure water, 55.8 parts of molybdenum trioxide, 2.6 parts of vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid aqueous solution and 1.5 parts of copper nitrate were dissolved, and this was stirred at 95 ° C. The mixture was stirred for 3 hours while maintaining the liquid temperature at 95 ° C. While cooling to 50 ° C. and stirring with a rotary blade stirrer, 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water was added dropwise and stirred at 25 ° C. for 15 minutes to precipitate a heteropolyacid salt. The structure of the precipitated heteropolyacid salt was Keggin type. Thereafter, 44.2 parts of molybdenum trioxide was added and stirred at 50 ° C. for 15 minutes, and 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water was added dropwise and stirred for another 15 minutes.

  A catalyst was produced in the same manner as in Example 1 except that the obtained mixed solution was used. The structure of the heteropolyacid (salt) in the dried product was a Keggin type. The elemental composition of the obtained catalyst was as follows. Moreover, as a result of calculating the mass and element distribution of the poorly water-soluble component at this time, they were α = 70.8 mass% and β = 68.5 atomic%.

Mo ₁₂ V _0.5 P _1.0 Cu _0.11 Cs _1.2
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

Example 3
In 400 parts of pure water, 83.3 parts of molybdenum trioxide, 2.6 parts of vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid aqueous solution and 1.5 parts of copper nitrate were dissolved, and this was stirred at 95 ° C. The mixture was stirred for 3 hours while maintaining the liquid temperature at 95 ° C. While cooling to 50 ° C. and stirring with a rotary blade stirrer, 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water was added dropwise and stirred at 25 ° C. for 15 minutes to precipitate a heteropolyacid salt. The structure of the precipitated heteropolyacid salt was Keggin type. Thereafter, 16.7 parts of molybdenum trioxide was added and stirred at 50 ° C. for 15 minutes, and 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water was added dropwise and stirred for another 15 minutes.

  A catalyst was produced in the same manner as in Example 1 except that the obtained mixed solution was used. The structure of the heteropolyacid (salt) in the dried product was a Keggin type. The elemental composition of the obtained catalyst was as follows. Moreover, as a result of calculating the mass and element distribution of the poorly water-soluble component at this time, they were α = 62.2 mass% and β = 59.3 atomic%.

Mo ₁₂ V _0.5 P _1.0 Cu _0.11 Cs _1.2
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

Example 4
In 400 parts of pure water, 41.7 parts of molybdenum trioxide, 2.6 parts of vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid aqueous solution and 1.5 parts of copper nitrate were dissolved, and the mixture was stirred at 95 ° C. The mixture was stirred for 3 hours while maintaining the liquid temperature at 95 ° C. While cooling to 50 ° C. and stirring with a rotary blade stirrer, 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water was added dropwise and stirred at 25 ° C. for 15 minutes to precipitate a heteropolyacid salt. The structure of the precipitated heteropolyacid salt was Keggin type. Thereafter, 58.3 parts of molybdenum trioxide was added and stirred at 50 ° C. for 15 minutes, and 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water was added dropwise and stirred for another 15 minutes.

  A catalyst was produced in the same manner as in Example 1 except that the obtained mixed solution was used. The structure of the heteropolyacid (salt) in the dried product was a Keggin type. The elemental composition of the obtained catalyst was as follows. Moreover, as a result of calculating the mass and element distribution of the poorly water-soluble component at this time, they were α = 75.4 mass% and β = 73.6 atomic%.

Mo ₁₂ V _0.5 P _1.0 Cu _0.11 Cs _1.2
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

[Comparative Example 1]
In 400 parts of pure water, 100 parts of molybdenum trioxide, 2.6 parts of vanadium pentoxide, 6.7 parts of 85 mass% phosphoric acid aqueous solution and 1.5 parts of copper nitrate are dissolved, and the temperature is raised to 95 ° C. with stirring. The mixture was warmed and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. While cooling to 50 ° C. and stirring with a rotary blade stirrer, 13.5 parts of cesium bicarbonate dissolved in 20 parts of pure water was added dropwise and stirred at 25 ° C. for 15 minutes to precipitate a heteropolyacid salt. The structure of the precipitated heteropolyacid salt was Keggin type. Thereafter, 11.6 parts of ammonium nitrate dissolved in 20 parts of pure water was added dropwise and stirred for another 15 minutes.

  A catalyst was produced in the same manner as in Example 1 except that the obtained mixed solution was used. The structure of the heteropolyacid (salt) in the dried product was a Keggin type. The elemental composition of the obtained catalyst was as follows. Moreover, as a result of computing the mass and element distribution of the poorly water-soluble component at this time, they were α = 61.5 mass% and β = 59.2 atomic%.

Mo ₁₂ V _0.5 P _1.0 Cu _0.11 Cs _1.2
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

[Comparative Example 2]
A mixed solution was obtained in the same manner as in Comparative Example 1 except that the cooling temperature when dropping cesium bicarbonate was changed from 50 ° C to 25 ° C. The structure of the precipitated heteropolyacid salt was Keggin type.

  A catalyst was produced in the same manner as in Example 1 except that the obtained mixed solution was used. The structure of the heteropolyacid (salt) in the dried product was a Keggin type. The elemental composition of the obtained catalyst was as follows. Moreover, as a result of calculating the mass and element distribution of the poorly water-soluble component at this time, they were α = 54.8 mass% and β = 87.0 atomic%.

Mo ₁₂ V _0.5 P _1.0 Cu _0.11 Cs _1.2
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

  Based on the above results, an aqueous slurry or aqueous solution containing a heteropolyacid is prepared by adding at least a part of the molybdenum raw material and a phosphorus raw material, and an alkali metal compound is added to precipitate the heteropolyacid salt, and then the remaining molybdenum raw material By using the catalysts of Examples 1 to 4 produced by the method of adding methacrylic acid, it was possible to produce methacrylic acid with high yield. In particular, the atomic ratio of molybdenum in the molybdenum raw material added in the preparation step and phosphorus in the phosphorus raw material added in the preparation step is in the range of 6.5: 1 to 9: 1, and α and β are 65 ≦ α ≦ 80. Further, by using the catalysts of Examples 1 and 2 satisfying 50 ≦ β ≦ 70, methacrylic acid could be produced with a higher yield. On the other hand, in the catalysts of Comparative Examples 1 and 2 manufactured by a method in which all of the molybdenum raw material is added in the adjusting step and the method does not have the molybdenum adding step, both α and β are 65 ≦ α ≦ 80 and 50 ≦ β. ≦ 70 could not be satisfied, and the methacrylic acid yield was low.

  The catalyst for producing methacrylic acid of the present invention is useful for producing methacrylic acid.

Claims (5)

A method for producing a catalyst containing molybdenum, phosphorus and an alkali metal, which is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen,
(I) adding at least a part of a molybdenum raw material and a phosphorus raw material in water to prepare an aqueous slurry or aqueous solution containing a heteropolyacid; and (ii) adding an alkali metal compound to the aqueous slurry or aqueous solution, Depositing a heteropolyacid salt in which at least a part of the heteropolyacid is an alkali metal salt;
(Iii) adding the remaining molybdenum raw material to the aqueous slurry in which the heteropolyacid salt is precipitated;
(Iv) drying an aqueous slurry or aqueous solution containing all raw materials to obtain a dried product;
(V) A method for producing a catalyst for producing methacrylic acid, comprising a step of heat-treating the dried product.   An atomic ratio between molybdenum in the molybdenum raw material added in the step (i) and phosphorus in the phosphorus raw material added in the step (i) is 6.5: 1 to 9: 1. The manufacturing method of the catalyst for methacrylic acid manufacture of Claim 1.   When the mass ratio of the poorly water-soluble component in the catalyst heat-treated in the step (v) is α mass%, and the hetero atom contained in the poorly water-soluble component among the hetero atoms contained in the catalyst is β atomic%, 65 ≦ The method for producing a catalyst for producing methacrylic acid according to claim 1, wherein α ≦ 80 and 50 ≦ β ≦ 70 are satisfied.   The catalyst for methacrylic acid manufacture manufactured with the method in any one of Claims 1-3.   A method for producing methacrylic acid, wherein the methacrolein is vapor-phase contact oxidized with molecular oxygen using the methacrylic acid production catalyst according to claim 4.