JP2007253033A - Catalyst for producing methacrylic acid, its production method, and production method of methacrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst used when producing methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen, which can display higher yield of methacrylic acid. <P>SOLUTION: A production method of the catalyst with a specific composition for producing methacrylic acid has a calcination step for calcining a catalyst precursor at 200-500°C, and a removing step for extracting at least a part of water-soluble component in a calcined material obtained in the calcination step from the calcined material into an extraction solvent to be removed. After the removing step, drying and calcination are usually carried out. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst for producing methacrylic acid used when producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, a method for producing the same, and a method for producing methacrylic acid.

  As a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, a catalyst containing molybdophosphoric acid, molybdophosphate or the like as a main component is known. Many studies have been made on the production methods of these catalysts. In many of them, first, a raw material liquid such as an aqueous solution or an aqueous slurry containing each element constituting the catalyst is prepared, and then this is dried and calcined. And the catalyst is manufactured. In addition, after the raw material liquid is dried and pre-baked, a method of kneading with ammonia water, re-drying, and baking is also studied (see Patent Document 1).

However, the catalysts produced by these conventional methods do not always exhibit a sufficient methacrylic acid yield as an industrial catalyst.
Therefore, a method for improving the performance of the catalyst by removing low active components in the catalyst and increasing the ratio of active species has been studied. The active species of this type of catalyst are considered to be water-soluble components such as molybdophosphoric acid and molybdovanaric acid (see Non-Patent Document 1), while sulfate radicals derived from catalyst raw materials are low-activity components. It is considered. From such a viewpoint, for example, Patent Document 2 discloses a technique for removing sulfate radicals as barium sulfate from a catalyst raw material liquid.
JP-A-9-290161 JP-A-6-287160 Ueshima et al., Surface, 24 (10), 582 (1986)

  However, even with the method described in Patent Document 2, the improvement in catalyst performance was insufficient.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the catalyst for methacrylic acid production which can exhibit a higher methacrylic acid yield.

  As described above, the active species of this type of methacrylic acid production catalyst are considered to be water-soluble components such as molybdophosphoric acid and molybdovanaric acid, and conventionally, the ratio of such water-soluble components in the catalyst will be increased. However, as a result of intensive studies, the present inventors have surprisingly found that the reason for this is not clear by removing at least a part of the water-soluble component, but higher methacrylic acid yield. The present invention was completed by finding that a catalyst for producing methacrylic acid capable of exhibiting a high rate was obtained.

The method for producing a catalyst for producing methacrylic acid according to the present invention is a method for producing a catalyst represented by the following formula (1) for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. A firing step of firing the precursor at 200 to 500 ° C., and a removal step of extracting and removing at least a part of the water-soluble components in the fired product from the fired product obtained in the firing step into an extraction solvent. It is characterized by having.
P _α1 Mo _α2 V _α3 Cu _α4 X _α5 Y _α6 Z _α7 O _α8 (1)
(Wherein, P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. X is 1 selected from the group consisting of arsenic, tellurium, antimony, selenium and silicon. Y represents one element, Y represents one element selected from the group consisting of bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium, and lanthanum, and Z represents potassium and rubidium. , And one element selected from the group consisting of cesium, α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01-2, α5 = 0.01-3, α6 = 0-3, α7 = 0.01-3, and α8 is an oxygen atom necessary to satisfy the valence of each component. (The ratio.)
The catalyst for producing methacrylic acid of the present invention is produced by the production method described above.
Moreover, the manufacturing method of methacrylic acid of this invention uses the said catalyst for methacrylic acid manufacture.

  ADVANTAGE OF THE INVENTION According to this invention, the catalyst for methacrylic acid manufacture which can exhibit a higher methacrylic acid yield can be provided.

Hereinafter, the present invention will be described in detail.
The present invention relates to a method for producing a catalyst for producing methacrylic acid, which has a composition represented by the following formula (1), and is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. Is.

P _α1 Mo _α2 V _α3 Cu _α4 X _α5 Y _α6 Z _α7 O _α8 (1)
(Wherein, P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. X is 1 selected from the group consisting of arsenic, tellurium, antimony, selenium and silicon. Y represents one element, Y represents one element selected from the group consisting of bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium, and lanthanum, and Z represents potassium and rubidium. , And one element selected from the group consisting of cesium, α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01-2, α5 = 0.01-3, α6 = 0-3, α7 = 0.01-3, and α8 is an oxygen atom necessary to satisfy the valence of each component. (The ratio.)

When producing the methacrylic acid production catalyst of the above formula (1), preferably, first, a raw material liquid containing each element (other than oxygen) constituting the catalyst at a ratio represented by the above formula (1) is prepared. (Raw material preparation step) Then, this is dried (drying step) to produce a catalyst precursor.
The method for preparing the raw material liquid is not particularly limited, but a method of preparing a slurry-like raw material liquid by charging the raw materials of each element into water and heating and stirring at 30 to 100 ° C. is preferable. As for the usage-amount of water, 200-1000 mass parts is preferable with respect to a total of 100 mass parts of the raw material of each element.

As raw materials for each element, oxides, nitrates, carbonates, ammonium salts and the like of each element can be appropriately selected and used. For example, molybdic acid or molybdenum trioxide is preferable as a raw material of molybdenum, but ammonium paramolybdate or the like can also be used. As a raw material of phosphorus, orthophosphoric acid, phosphorus pentoxide, ammonium phosphate, etc. can be used. As a raw material of vanadium, ammonium metavanadate, divanadium pentoxide, or the like can be used. Moreover, copper nitrate, copper sulfate, copper carbonate, etc. can be used as a raw material of copper.
Although there is no particular limitation on the preparation scale of the raw material liquid, a preferable raw material liquid can be stably prepared when the amount of the molybdenum raw material used is preferably 100 g to 10 t, more preferably 1 kg to 1 t. it can.

  Moreover, when preparing a slurry-form raw material liquid, the pH of the raw material liquid is preferably less than 8, and more preferably less than 3. When the pH is less than 8, a catalyst precursor having a preferable structure is easily obtained, and as a result, a catalyst for producing methacrylic acid capable of exhibiting a higher yield of methacrylic acid is obtained.

  There are no particular limitations on the specific method of the drying step of drying such a raw material liquid to obtain a catalyst precursor, and examples thereof include an evaporating and drying method, a spray drying method, a drum drying method, and an airflow drying method. . There are no particular limitations on the type, model, drying temperature, atmosphere, and the like of the dryer used for drying, and examples include conditions for drying at 100 to 180 ° C. in an air atmosphere for 0.1 to 20 hours. Since the physical properties such as fluidity and moldability of the catalyst precursor can be controlled by changing the drying conditions, it is preferable to set conditions according to the purpose.

Next, a firing step is performed in which the catalyst precursor obtained by drying in this manner is fired at 200 to 500 ° C. Moreover, you may implement the shaping | molding process which preforms a catalyst precursor as needed before a baking process.
In that case, there is no restriction | limiting in particular in a specific shaping | molding method, A well-known dry type and wet shaping | molding method can be applied, For example, tableting shaping | molding, press molding, extrusion molding, granulation shaping | molding etc. are mentioned. The shape of the molded product is not particularly limited, and examples thereof include a columnar shape, a ring shape, and a spherical shape. Further, at the time of molding, it is preferable to mold only the catalyst precursor without adding a carrier or the like to the catalyst precursor.

  The firing method and firing conditions in the firing step are not particularly limited, and known methods and conditions can be applied. Preferable calcination conditions vary depending on the raw materials (catalyst raw materials) of each element constituting the catalyst, the catalyst composition, the preparation method of the raw material liquid, etc., but are usually 200 to 200 under an oxygen-containing gas flow such as air or an inert gas flow. Baking is performed at 500 ° C., preferably 300 to 400 ° C., for 0.5 hour or longer, preferably 1 to 40 hours. Here, the inert gas refers to a gas that does not decrease the catalytic activity, and examples thereof include nitrogen, carbon dioxide, helium, and argon.

Next, a removal step is performed in which at least a part of the water-soluble component in the fired product obtained in the firing step is extracted from the fired product and removed. Specifically, after the fired product is dispersed or immersed in the extraction solvent, solid-liquid separation is performed by a known separation method to recover the solid component.
As the extraction solvent used for extraction, water or an aqueous solvent such as an aqueous solution of an inorganic acid and / or an inorganic salt is suitable. In the case of using an aqueous solution of an inorganic acid and / or an inorganic salt, the pH is preferably less than 8 from the viewpoint of maintaining the chemical structure and physical structure of the catalyst, and includes sodium, potassium, calcium and magnesium. It is more preferable that it does not adversely affect the performance of the catalyst. Although the usage-amount of an extraction solvent is not specifically limited, It is preferable that it is the mass of 500 times or less with respect to the mass of a baked product, and 2-50 times is more preferable.

When the fired product is dispersed in the extraction solvent, the fired product may be simply added to the extraction solvent and stirred, but it is preferable to hold for 1 to 60 minutes while irradiating ultrasonic waves because the extraction efficiency is increased. . The temperature of the extraction solvent is preferably 10 to 100 ° C.
As the solid-liquid separation method, filtration, centrifugation, or the like can be applied, and it may be selected according to the particle size of the fired product. For example, when the particle size of the fired product in the extraction solvent is several μm or more, filtration can be applied. However, when the fired product in the extraction solvent contains particles of 1 μm or less, such particles are separated. Since it is difficult to filter, it is preferable to apply centrifugation.
When centrifugation is applied, the total amount of the liquid component does not necessarily have to be removed from the solid component, but since a catalyst for producing methacrylic acid with a higher methacrylic acid yield is obtained, the mass of the extraction solvent used It is preferable to remove an amount of liquid corresponding to 10% by mass or more, and considering workability, it is preferable to remove an amount of 50 to 80% by mass.
According to such a removal process, the component containing elements other than the element shown by Z in said Formula (1) is mainly removed as a water-soluble component.

The solid slurry after removing at least a part of the water-soluble component in this way, or the mixed slurry of the solid component and the residual liquid remaining accompanying the solid component is dried again (re-drying step), preferably again By calcination (refiring step), a catalyst for producing methacrylic acid is obtained. What is necessary is just to perform a re-drying process and a rebaking process by the method and conditions similar to the above-mentioned drying process and baking process, respectively.
Moreover, you may perform the remolding process of remolding the re-dried product obtained by the re-drying process by the well-known dry type and wet molding method before a rebaking process as needed. As specific molding methods and shapes of molded products, various methods and shapes exemplified above in the molding step can be similarly employed. Further, at the time of molding, it is preferable to mold without adding a carrier or the like, but a known additive such as graphite or talc may be added as necessary.

By contacting the raw material gas containing methacrolein and molecular oxygen with the methacrylic acid production catalyst thus produced, methacrolein is vapor-phase contact oxidized with molecular oxygen to obtain methacrylic acid.
Here, there is no restriction | limiting in the methacrolein density | concentration in source gas, Although it can set to arbitrary density | concentrations, 1-20 volume% is suitable, and 3-10 volume% is especially preferable. The molecular oxygen concentration in the raw material gas is preferably 0.5 to 4 mol, more preferably 1 to 3 mol, relative to 1 mol of methacrolein. In addition, an inert gas such as nitrogen or carbon dioxide may be added to the raw material gas for dilution, or water vapor may be added.
The reaction pressure is usually set within a range from atmospheric pressure to several hundred kPa. The reaction temperature is usually set within the range of 230 to 450 ° C., and from the point of methacrylic acid yield, 250 to 400 ° C. is preferable.

  The method for producing a catalyst for producing methacrylic acid described above includes a firing step of firing a catalyst precursor at 200 to 500 ° C., and at least a part of the water-soluble component in the fired product obtained in the firing step from the fired product. However, the reason is not clear, but a catalyst for methacrylic acid production capable of producing methacrylic acid in a high yield can be provided.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.
Further, “parts” in the following examples and comparative examples are parts by mass.
The analysis of the raw material gas and the product was performed using gas chromatography. In addition, the reaction rate of methacrolein, the selectivity of the methacrylic acid to produce | generate, and a single flow yield are defined as follows.
Reaction rate of methacrolein (%) = (B / A) × 100
Methacrylic acid selectivity (%) = (C / B) × 100
Single flow yield of methacrylic acid (%) = (C / A) × 100
Here, 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]
(1) Raw material solution preparation step (preparation of solution A)
200 parts of pure water, 100 parts of molybdenum trioxide, 6.67 parts of 85 mass% phosphoric acid, 3.39 parts of ammonium metavanadate, 2.10 parts of cupric nitrate, 0.47 parts of ferric nitrate, 60% A solution A was prepared by adding 9.59 parts of an aqueous arsenic acid solution and stirring for 5 hours at 100 ° C. under reflux.
The amount of ammonium contained in the A liquid was 0.5 mol with respect to 12 mol of molybdenum atoms contained in the A liquid.
(Preparation of liquid B)
Liquid B was prepared by dissolving 10.10 parts of cesium bicarbonate in 28.43 parts of pure water at 50 ° C.
(Mixing of liquid A and liquid B)
After cooling A liquid to 50 degreeC, B liquid was mixed with A liquid, stirring, and it stirred for 10 minutes, and prepared AB mixed liquid.
While stirring the AB mixture thus obtained at a liquid temperature of 50 ° C., 2.20 parts of ammonium nitrate and 12.00 parts of ammonium bicarbonate were added to 20.00 parts of pure water. The solution dissolved in was added to obtain a slurry containing the catalyst precursor.
(2) Drying Step The slurry containing this catalyst precursor was heated to 101 ° C., evaporated to dryness with stirring, and further dried at 130 ° C. for 16 hours to obtain a catalyst precursor.
(3) Molding step and calcination step The obtained catalyst precursor was molded into a ring shape having an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5 mm by a tableting machine. This molded product was fired at 380 ° C. for 12 hours under air flow to obtain a fired product.

(4) Removal step 100 parts of the obtained fired product was added to 1000 parts of water and stirred at room temperature for 1 hour. Subsequently, the obtained dispersion was subjected to a centrifuge in which an angle rotor R20A2 was mounted on a Himac CR22F manufactured by Hitachi Koki Co., Ltd., and separation was performed for 5 minutes under conditions of 12000 rpm and 5 ° C. The calculated value of gravity applied by centrifugation under this condition is about 17300G. After sedimentation of the solid component by centrifugation, 750 parts (corresponding to 75% by mass of the extraction solvent used) of the supernatant were removed.
When the supernatant was dried, 47 parts by mass of solid was obtained. Further, when this solid was subjected to elemental analysis by atomic absorption spectrophotometry and ICP emission spectrometry, the composition other than oxygen was P _1.0 Mo ₁₂ V _0.77 As _0.88 Cu _0.24 Fe _0.02 . there were.
(5) Re-drying step The mixture of the solid component after removing the supernatant containing at least a part of the water-soluble component and the residual liquid remaining therewith is stirred again to form a slurry and evaporated to dryness. Then, it was dried at 130 ° C. for 16 hours to obtain a re-dried product.
(6) Re-molding step and re-baking step The obtained re-dried product was re-formed into a ring shape having an outer diameter of 5 mm, an inner diameter of 2 mm, and a length of 5 mm using a tableting machine. The remolded product was calcined at 380 ° C. for 12 hours under air flow to obtain a methacrylic acid production catalyst.
The composition of the obtained catalyst other than oxygen was P _1.0 Mo ₁₂ V _0.2 As _0.5 Cu _0.05 Fe _0.02 Cs _1.9 .
This catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the following conditions. The results are shown in Table 1.

(Reaction conditions)
Reaction gas: 5% by volume of methacrolein, 10% by volume of oxygen, 30% by volume of water vapor, 55% by volume of nitrogen Reaction temperature: 290 ° C.
Reaction pressure: 101 kPa (absolute pressure)
Contact time: 3.6 seconds

[Example 2]
(1) Raw material solution preparation step (preparation of solution A)
To 200 parts of pure water, 100 parts of molybdenum trioxide, 6.67 parts of 85% by weight phosphoric acid, 3.39 parts of ammonium metavanadate, and 9.59 parts of 60% aqueous arsenic acid solution are added and stirred at 100 ° C. under reflux for 5 hours. A solution was prepared.
The amount of ammonium contained in the A liquid was 0.5 mol with respect to 12 mol of molybdenum atoms contained in the A liquid.
(Preparation of liquid B)
Liquid B was prepared by dissolving 10.10 parts of cesium bicarbonate in 28.43 parts of pure water at 50 ° C.
(Preparation of liquid C)
The liquid C was 41.34 parts of 25% by mass aqueous ammonia.
The amount of ammonium contained in the C liquid was 10.5 mol with respect to 12 mol of molybdenum atoms contained in the A liquid.
(Mixture of liquid A, liquid B, liquid C)
After cooling A liquid to 70 degreeC, B liquid was mixed with A liquid, stirring, and it stirred for 10 minutes, and prepared AB mixed liquid. Subsequently, C liquid was gradually added over 10 minutes to this AB mixed liquid, stirring AB mixed liquid. After mixing the liquid C, the mixture was stirred and held at 50 ° C. for 60 minutes to prepare an ABC liquid mixture.
While stirring the thus-obtained ABC mixed liquid at a liquid temperature of 50 ° C., 2.10 parts of cupric nitrate and 0.47 part of ferric nitrate were added to 9.80 parts of pure water. The solution dissolved in was added to obtain a slurry containing the catalyst precursor.

(2) Drying step to (6) Re-molding step and re-baking step The steps (2) to (6) were carried out in the same manner as in Example 1 to obtain a catalyst for producing methacrylic acid.
The composition of the obtained catalyst other than oxygen was P _1.0 Mo ₁₂ V _0.2 As _0.4 Cu _0.05 Fe _0.015 Cs _2.0 .
The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
In addition, when the supernatant liquid obtained at the removal process was dried, 45 mass parts solid was obtained. When this solid was subjected to elemental analysis in the same manner as in Example 1, the composition other than oxygen was P _1.0 Mo ₁₂ V _0.75 As _0.95 Cu _0.23 Fe _0.02 .

[Example 3]
To 200 parts of pure water, 100 parts of molybdenum trioxide, 6.67 parts of 85% by weight phosphoric acid, 7.59 parts of 70.9% by weight vanadyl oxalate, 2.10 parts of cupric nitrate, 0. A catalyst for methacrylic acid production was produced in the same manner as in Example 1 except that 47 parts and 3.70 parts of tellurium oxide were added and stirred for 5 hours under reflux at 100 ° C. to prepare solution A.
The composition of the obtained catalyst other than oxygen was P _1.0 Mo ₁₂ V _0.2 Te _0.3 Cu _0.05 Fe _0.01 Cs _1.9 .
The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
In addition, when the supernatant liquid obtained at the removal process was dried, 47 mass parts solid was obtained. When this solid was subjected to elemental analysis in the same manner as in Example 1, the composition other than oxygen was P _1.0 Mo ₁₂ V _0.77 Te _0.49 Cu _0.24 Fe _0.02 .

[Example 4]
200 parts of pure water, 100 parts of molybdenum trioxide, 6.67 parts of 85 mass% phosphoric acid, 7.59 parts of 70.9 mass% vanadyl oxalate, 2.10 parts of cupric nitrate, 2.49 parts of manganese nitrate A catalyst for methacrylic acid production was produced in the same manner as in Example 1 except that 3.38 parts of antimony trioxide was added and stirred for 5 hours under reflux at 100 ° C. to prepare solution A.
The composition of the obtained catalyst other than oxygen was P _1.0 Mo ₁₂ V _0.2 Sb _0.3 Cu _0.05 Mn _0.1 Cs _1.9 .
The catalyst was filled in a reaction tube, and methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
In addition, when the supernatant liquid obtained at the removal process was dried, 47 mass parts solid was obtained. In addition, when the solid was subjected to elemental analysis in the same manner as in Example 1, the composition other than oxygen was P _1.0 Mo ₁₂ V _0.77 Sb _0.49 Cu _0.24 Mn _0.1 .

[Comparative Example 1]
In Example 1, (1) the raw material liquid preparation step to (3) the molding step and the firing step are performed, (4) the steps after the removal step are not performed, and the fired product obtained in (3) is used as a catalyst. Then, methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
The composition of the obtained catalyst (baked product) other than oxygen was P _1.0 Mo ₁₂ V _0.5 As _0.7 Cu _0.15 Fe _0.02 Cs _0.9 .

[Comparative Example 2]
In Example 2, (1) the raw material solution preparation step to (3) the molding step and the firing step are performed, (4) the steps after the removal step are not performed, and the fired product obtained in (3) is used as a catalyst. Then, methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
The composition of the obtained catalyst (baked product) other than oxygen was P _1.0 Mo ₁₂ V _0.5 As _0.7 Cu _0.15 Fe _0.02 Cs _0.9 .

[Comparative Example 3]
In Example 3, (1) the raw material solution preparation step to (3) the molding step and the firing step are performed, (4) the steps after the removal step are not performed, and the fired product obtained in (3) is used as a catalyst. Then, methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
The composition of the obtained catalyst (calcined product) other than oxygen was P _1.0 Mo ₁₂ V _0.5 Te _0.4 Cu _0.15 Fe _0.02 Cs _0.9 .

[Comparative Example 4]
In Example 4, (1) the raw material solution preparation step to (3) the molding step and the firing step are performed, (4) the steps after the removal step are not performed, and the fired product obtained in (3) is used as a catalyst. Then, methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
The composition of the obtained catalyst (baked product) other than oxygen was P _1.0 Mo ₁₂ V _0.5 Sb _0.4 Cu _0.15 Mn _0.1 Cs _0.9 .

[Comparative Example 5]
A baked product was obtained in the same manner as in Comparative Example 1, and this was used as a catalyst to produce methacrylic acid by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
However, the composition other than oxygen in the calcined product is the same _P 1.0 methacrylic acid production catalyst prepared in Example _{1 Mo 12 V 0.2 As 0.5 Cu} 0.05 Fe 0.02 Cs 1. _The amount of the raw material used in the raw material liquid preparation step was adjusted so as to be ₉ .

[Comparative Example 6]
A fired product was obtained in the same manner as in Comparative Example 2, and this was used as a catalyst to produce methacrylic acid by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
However, the composition other than oxygen of the baked product is the same as the catalyst for producing methacrylic acid produced in Example 2 P _1.0 Mo ₁₂ V _0.2 As _0.4 Cu _0.05 Fe _0.015 Cs2 _{. The} amount of the raw material used in the raw material liquid preparation step was adjusted so as to be _zero .

[Comparative Example 7]
A baked product was obtained in the same manner as in Comparative Example 3, and this was used as a catalyst to produce methacrylic acid by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
However, the composition of the fired product other than oxygen is the same as that of the methacrylic acid production catalyst produced in Example 3 P _1.0 Mo ₁₂ V _0.2 Te _0.3 Cu _0.05 Fe _0.01 Cs1 _{. The} amount of the raw material used in the raw material liquid preparation step was adjusted so as to be ₉ .

[Comparative Example 8]
A baked product was obtained in the same manner as in Comparative Example 4, and this was used as a catalyst to produce methacrylic acid by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.
However, P _1.0 Mo ₁₂ V _0.2 Sb _0.3 Cu _0.05 Mn _0.1 Cs _1. The composition other than oxygen of the fired product is the same as that of the catalyst for methacrylic acid production produced in Example 4 _{. The} amount of the raw material used in the raw material liquid preparation step was adjusted so as to be ₉ .

[Comparative Example 9]
(1) The raw material solution preparation step and (2) the drying step were performed in the same manner as in Comparative Example 1.
Subsequently, 100 parts of the obtained catalyst precursor was added to 1000 parts of water and stirred at room temperature for 1 hour. Thereafter, the obtained slurry was evaporated to dryness in the same manner as in the re-drying step (5) of Example 1, and then the same steps as the re-forming step and the re-firing step in Example 1 were performed.
Using the obtained product as a catalyst, methacrylic acid was produced by gas phase catalytic oxidation under the same conditions as in Example 1. The results are shown in Table 1.

As shown in Table 1, when the methacrylic acid production catalyst obtained in each example was used, methacrylic acid could be produced in a high yield.
On the other hand, in Comparative Examples 1-8 which did not implement after a removal process, the methacrylic acid yield became a result lower than Examples 1-4. In particular, in Comparative Examples 5 to 8, although the final catalyst composition was adjusted to that of Examples 1 to 4, the methacrylic acid yield was low, indicating the importance of the removal step. Moreover, in the comparative example 9 which performed the removal process before the baking process, the methacrylic acid yield became a very low result.

Claims (3)

A method for producing a methacrylic acid production catalyst represented by the following formula (1) for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen,
A firing step of firing the catalyst precursor at 200 to 500 ° C .;
A method for producing a catalyst for methacrylic acid production, comprising: removing from the calcined product obtained in the calcining step by extracting at least a part of the water-soluble components in the calcined product into an extraction solvent. .
P _α1 Mo _α2 V _α3 Cu _α4 X _α5 Y _α6 Z _α7 O _α8 (1)
(Wherein, P, Mo, V, Cu and O are element symbols indicating phosphorus, molybdenum, vanadium, copper and oxygen, respectively. X is 1 selected from the group consisting of arsenic, tellurium, antimony, selenium and silicon. Y represents one element, Y represents one element selected from the group consisting of bismuth, zirconium, silver, iron, zinc, chromium, magnesium, cobalt, manganese, barium, cerium, and lanthanum, and Z represents potassium and rubidium. , And one element selected from the group consisting of cesium, α1 to α8 represent the atomic ratio of each element, and when α2 = 12, α1 = 0.5 to 3, α3 = 0.01 to 3, α4 = 0.01-2, α5 = 0.01-3, α6 = 0-3, α7 = 0.01-3, and α8 is an oxygen atom necessary to satisfy the valence of each component. (The ratio.)   A catalyst for producing methacrylic acid, which is produced by the production method according to claim 1. A method for producing methacrylic acid, comprising using the catalyst for producing methacrylic acid according to claim 2.