JP2006088097A - Production method of catalyst for producing methacrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst to be used for producing metacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen, producing a catalyst precursor dried matter of an excellent fluidity obtained in the above production process and capable of producing methacrylic acid at high yield, and its production method. <P>SOLUTION: The production method of the catalyst to be used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation with molecular oxygen and containing at least molybdenum and phosphorus includes the steps of preparing a solution or slurry (precursor mixed solution) containing at least raw material molybdenum and phosphorus, concentrating the precursor mixed solution by a heating device to produce a concentrate and drying and firing the concentrate. In the method, temperature of a heat transfer face of the heating device for the above concentration is 100-150°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Examples of a method for producing a methacrylic acid production catalyst by mixing two or more kinds of mixed solutions containing catalyst component elements include methods described in Patent Documents 1 to 5 and the like. Among these, Patent Document 2 mixes a homogeneous solution containing the fourth component X such as molybdenum, vanadium, phosphorus, and antimony, ammonia water, and a homogeneous solution containing other catalyst component elements such as cesium, A method for producing a catalyst for producing methacrylic acid by drying the mixed solution is disclosed. Thereby, the solubility of the fourth component X (especially antimony) is improved, and the catalyst performance is excellent in reproducibility and stability, and a long-life catalyst is obtained.

Patent Document 6 discloses that a solution in which all catalyst raw materials are dissolved or suspended in water has an ammonium root content in the range of 17 to 100 mol with respect to 12 atoms of molybdenum and a pH of 6.5. A method for producing an oxidation catalyst in the range of ˜13 is disclosed. The pH is adjusted by adding nitric acid or aqueous ammonia.
JP-A-4-182450 JP-A-5-31368 JP-A-7-185354 JP-A-8-157414 JP-A-8-196908 JP-A-9-290162

  However, a catalyst produced by using such a conventional catalyst raw material mixing method or pH adjusting method is not necessarily sufficient as an industrial catalyst in terms of reaction results, and further improvement in catalyst performance is desired.

  The present invention is a catalyst used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, a catalyst for producing methacrylic acid capable of producing methacrylic acid in high yield, a production method thereof, And it aims at providing the manufacturing method of methacrylic acid using this catalyst.

  The above problems can be solved by the present invention described below.

That is, the present invention
In a method for producing a methacrylic acid production catalyst containing at least molybdenum and phosphorus, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen,
(A) preparing a solution or slurry (precursor mixture) containing at least a molybdenum raw material and a phosphorus raw material;
(B) concentrating the precursor mixture with a heating device to obtain a concentrate;
(C) drying and baking the concentrate;
And a heating heat transfer surface temperature of the heating device when the concentration is performed is 100 to 150 ° C., a method for producing a catalyst for methacrylic acid production.

The present invention also provides:
A catalyst for producing methacrylic acid produced by the production method described above.

Furthermore, the present invention provides
This is a method for producing methacrylic acid, in which methacrolein is vapor-phase contact oxidized with molecular oxygen in the presence of the catalyst for producing methacrylic acid.

  According to the present invention, a catalyst used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen, which is excellent in fluidity of a dried catalyst precursor obtained in the production process, and The catalyst which can manufacture methacrylic acid with a high yield, its manufacturing method, and the manufacturing method of methacrylic acid using this catalyst can be provided.

The catalyst of the present invention is a catalyst for producing methacrylic acid containing at least molybdenum and phosphorus, which is used in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein,
(A) preparing a solution or slurry (precursor mixture) containing at least a molybdenum raw material and a phosphorus raw material;
(B) concentrating the precursor mixture with a heating device to obtain a concentrate;
(C) drying and baking the concentrate,
It is manufactured by the method characterized by the heating-heat-transfer surface temperature of the said heating apparatus at the time of performing the said concentration being 100-150 degreeC. In particular, the catalyst has a composition represented by the following formula (1).

_{P a Mo b V c Cu d} X e Y f Z g O h (1)
(In the formula (1) and the specification, P, Mo, V, Cu and O respectively represent phosphorus, molybdenum, vanadium, copper and oxygen, and X represents antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, Represents at least one element selected from the group consisting of selenium, silicon, tungsten and boron, and Y is selected from the group consisting of iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium and lanthanum Z represents at least one element selected from the group consisting of potassium, rubidium, and cesium, and a, b, c, d, e, f, g, and h represent each element. And when b = 12, a = 0.5-3, c = 0.01-3, d = 0.01-2, e = 0-3, = 0-3, a g = 0.01 to 3, h is an atomic ratio of oxygen required to satisfy the valence of each component.)
The catalyst component is composed of phosphorus, molybdenum, vanadium, copper, Z element and oxygen as essential components, and the X element and Y element are optional components. a is preferably from 0.5 to 2. c is preferably from 0.01 to 1. As for g, 0.5-2 are preferred. The element Z is preferably cesium. The atomic ratio (a and c to g) of each element in the target catalyst for methacrylic acid production can be arbitrarily set within the above range by appropriately adjusting the blending ratio of each raw material to be described later. The composition of the produced catalyst for producing methacrylic acid can be analyzed for a composition other than oxygen, for example, by analyzing a catalyst dissolved in aqueous ammonia by ICP emission spectrometry and atomic absorption spectrometry.

  The mechanism of improving the fluidity and catalyst performance of the dried catalyst precursor obtained by the production method of the present invention is not clear, but by concentrating the precursor mixed solution under specific conditions, it is possible to prevent hopper bridging and the like. Catalyst precursor dry matter with excellent fluidity that contributes to stable production of the catalyst, such as problems in body transportation, and powder mixing into molds such as tableting and press molding can be easily performed in a short time. And a crystal structure of the catalyst from which methacrylic acid is obtained in high yield is presumed.

  Hereinafter, the method for producing the catalyst for producing methacrylic acid of the present invention will be described in more detail.

[(A) Preparation of precursor mixture]
First, a solution or slurry (precursor mixture) containing at least a molybdenum raw material and a phosphorus raw material is prepared. It does not specifically limit as a preparation method, It can carry out by the method of dissolving or disperse | distributing a required raw material in a solvent. A system involving ammonium in the preparation stage is common. Examples of preparation methods include the coprecipitation method and the oxide mixing method.
(I) preparing a solution or slurry (liquid A) containing a molybdenum raw material, a phosphorus raw material and a vanadium raw material;
(Ii) preparing a solution or slurry (liquid B) containing ammonia or an ammonia compound;
(Iii) preparing a solution or slurry (solution C) containing a raw material for the Z element;
(Iv) mixing the liquid A and the liquid C to obtain an AC mixed liquid;
(V) mixing the A-C mixture and the B solution to obtain an A-C-B mixture;
(Vi) a step of mixing the A-C-B mixed liquid and other necessary raw materials to obtain a precursor mixed liquid;
By performing by the method which has this, the catalyst which has a composition represented by said Formula (1) can be manufactured. Hereinafter, this method will be described in detail.

<(I) Preparation of solution A>
The liquid A is a solution or slurry containing a molybdenum raw material, a phosphorus raw material, and a vanadium raw material, and can be prepared by dissolving or suspending a molybdenum raw material, a phosphorus raw material, and a vanadium raw material in a solvent. It is preferable that the molybdenum raw material used for preparation of A liquid does not contain ammonium. Further, it is preferable that the liquid A does not contain other raw materials, that is, raw materials of copper, X element, Y element, and Z element. The amount of ammonium contained in the A liquid is preferably 1.5 mol or less with respect to 12 mol of molybdenum atoms contained in the A liquid.

Here, “ammonium” means not only NH ₄ ⁺ but also NH ₃ , and “ammonium-free” means the sum of NH ₄ ⁺ and NH _{3 in} a general analytical method (eg, Kjeldahl method). Is less than the limit of quantification, and may contain 0.01 part by mass or less of ammonium with respect to 100 parts by mass of molybdenum, phosphorus and vanadium contained in the raw material (described later). The same applies to liquid C).

  It does not specifically limit as a molybdenum raw material to be used, For example, a molybdenum trioxide, molybdic acid etc. are mentioned. The molybdenum raw material may be used alone or in combination of two or more. It does not specifically limit as a phosphorus raw material to be used, For example, normal phosphoric acid, phosphorus pentoxide, ammonium phosphate, etc. are mentioned. A phosphorus raw material may use 1 type, or may use 2 or more types together. The vanadium raw material to be used is not particularly limited. Examples of the vanadium raw material include vanadium pentoxide and ammonium metavanadate. The vanadium raw material may be used alone or in combination of two or more. What is necessary is just to set suitably the compounding ratio of these raw materials so that it may become the composition of the target catalyst.

  In addition, molybdenum raw material, phosphorus raw material, and vanadium raw material may be included in the liquid A, only a part may be included in the liquid A, and the remainder may be included in the liquid B or liquid C. You may mix with B liquid mixture. Since these can be easily prepared, it is preferable to include these raw materials in the total amount of the liquid A.

  As the solvent, water is preferably used. Although the quantity of the solvent in A liquid is not specifically limited, It is preferable that the ratio (mass ratio) of the molybdenum compound used for manufacture of A liquid and a solvent is 1: 0.1-1: 100.

  The state of the liquid A is not particularly limited, and may be a solution in which the raw material is completely dissolved in a solvent, or a slurry in which a part or all of the raw material is suspended in the solvent.

  In addition, although A liquid can be prepared by stirring at normal temperature, you may heat and prepare to about 100 degreeC as needed.

<(Ii) Preparation of solution B>
Liquid B is a solution or slurry containing ammonia or an ammonia compound, and can be prepared by dissolving or suspending ammonia and / or an ammonia compound in a solvent. It is preferable that the B liquid does not contain a molybdenum raw material. In addition, other catalyst raw materials, that is, phosphorus, vanadium, copper, X element, Y element, and Z element raw materials may be included unless the total amount, but it is more preferable that these are not included.

  The ammonia and the ammonia compound to be used are not particularly limited, and examples thereof include ammonia (ammonia water), ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrate and the like. Ammonia and / or ammonia compounds may be used alone or in combination of two or more.

  It is preferable to use water as the solvent for the liquid B. The amount of the solvent in the B liquid is not particularly limited, but the ratio (mass ratio) of ammonia and the ammonia compound used in the manufacture of the B liquid to the solvent is preferably 1: 0.1 to 1: 100.

  The state of the B liquid is not particularly limited, and may be a solution in which ammonia and / or an ammonia compound is completely dissolved in a solvent, or a slurry in which a part or all of the suspension is suspended in a solvent.

  In addition, although B liquid can be normally prepared by stirring at normal temperature, you may heat and prepare to the temperature range of the range which does not evaporate as ammonia as needed.

<(Iii) Preparation of solution C>
The liquid C is a solution or slurry containing a Z element raw material, and can be prepared by dissolving or suspending the Z element raw material in a solvent. Here, the Z element is at least one element selected from the group consisting of potassium, rubidium, and cesium. The liquid C may contain other raw materials, that is, raw materials of phosphorus, molybdenum, vanadium, copper, X element, and Y element, if they are not in total amount, but it is more preferable not to contain them. Moreover, it is preferable that C liquid does not contain ammonium. In the present invention, when the Z element is cesium, a particularly excellent effect is obtained.

  As a raw material for the Z element to be used, nitrates, carbonates, hydroxides and the like of each element can be appropriately selected and used. For example, as a cesium raw material, cesium nitrate, cesium carbonate, cesium hydroxide and the like can be used. Each raw material may use 1 type with respect to each element, or may use 2 or more types together.

  The total amount of the Z element raw material may be included in the C liquid, only a part may be included in the C liquid, and the rest may be included in the A liquid or the B liquid. You may mix. These raw materials are preferably included in the total amount C solution because they can be easily prepared.

  As the solvent, water is preferably used. The amount of the solvent in the liquid C is not particularly limited, but the ratio (mass ratio) of all the raw materials and the solvent contained in the liquid C is preferably 1: 0.1 to 1: 100.

  In addition, although C liquid can be prepared by stirring at normal temperature, you may heat and prepare to about 80 degreeC as needed.

<(Iv) Preparation of AC mixture>
Next, the A liquid and the C liquid prepared as described above are mixed to prepare an AC mixed liquid.

  The mixing method of A liquid and C liquid is not specifically limited, For example, the method of adding C liquid to the container containing A liquid, the method of adding A liquid to the container containing C liquid, Arbitrary methods, such as the method of pouring C liquid simultaneously, can be used. Mixing is usually performed with stirring, and the AC mixture is preferably as uniform as possible. What is necessary is just to set suitably the mixing ratio of A liquid and C liquid so that it may become the composition of the target catalyst.

  The state of the AC mixed solution is not particularly limited, and may be a solution or a slurry (suspension).

  The A-C mixed solution may be prepared usually at room temperature, but it may be prepared by heating to about 100 ° C. if necessary. Moreover, you may perform operation, such as heat processing, with respect to the obtained AC mixed liquid suitably. The temperature of the heat treatment is preferably up to 100 ° C., but can be raised to 100 ° C. or higher by using an autoclave or the like as necessary. Note that the heating time may be determined as appropriate.

<(V) Preparation of A-C-B mixture>
Next, the A-C liquid and B liquid prepared as described above are mixed to prepare an A-C-B mixed liquid.

  The mixing method of the A-C liquid and the B liquid is not particularly limited. For example, a method of adding the B liquid to the container containing the A-C liquid, a method of adding the A-C liquid to the container containing the B liquid, separately prepared Arbitrary methods, such as the method of pouring A-C liquid and B liquid simultaneously in the container which carried out, can be utilized. Mixing is usually carried out with stirring, and the A-C-B mixture is preferably as uniform as possible.

  The mixing ratio of the AC liquid and the B liquid is such that a catalyst with a high methacrylic acid yield is obtained, so that the amount of ammonium in the B liquid is 6 moles or more, particularly 12 moles of molybdenum atoms in the A liquid. The amount is preferably 7 mol or more, more preferably 17 mol or less, and particularly preferably 15 mol or less.

  The state of the A-C-B mixed liquid is not particularly limited, and may be a solution or a slurry (suspension).

  The A-C-B mixed solution may be usually prepared at room temperature, but may be prepared by heating to about 100 ° C. as necessary. Moreover, you may perform operations, such as heat processing, suitably with respect to the obtained ACB mixed liquid. The temperature of the heat treatment is preferably up to 100 ° C., but can be raised to 100 ° C. or higher by using an autoclave or the like as necessary. Note that the heating time may be determined as appropriate.

<(Vi) Mixing of A-C-B mixture and other necessary raw materials>
Next, the prepared A-C-B mixture is mixed with other raw materials necessary for achieving the target catalyst composition, and a solution or slurry containing the catalyst precursor (precursor mixture) is obtained. Prepare.

  It does not specifically limit as a raw material to be used, Nitrate, carbonate, a hydroxide, etc. of each element can be selected suitably and can be used. For example, copper nitrate, copper carbonate, or the like can be used as the copper raw material. A raw material may use 1 type with respect to each element, or may use 2 or more types together.

  These raw materials may be mixed as they are, or may be mixed in the form of a solution or suspension previously mixed with a solvent. As a solvent for the solution or suspension, water is preferably used. The amount of the solvent is not particularly limited and may be determined as appropriate. What is necessary is just to set the mixing amount of a raw material suitably so that it may become the composition of the target catalyst.

  The mixing method is not particularly limited. For example, a method of sequentially adding other raw materials necessary to a container containing an A-C-B mixed solution, or A-C-B mixing to a container containing other necessary raw materials. Arbitrary methods such as a method of adding a liquid and a method of simultaneously pouring the A-C-B mixed solution and other necessary raw materials into a separately prepared container can be used. Mixing is usually carried out with stirring.

  Although the temperature of the solution at the time of mixing an ACB liquid mixture and other required raw materials is not specifically limited, It is preferable that it is 100 degrees C or less. Moreover, you may perform operation, such as heat processing, suitably with respect to the solution or slurry (precursor mixed solution) containing the obtained catalyst precursor. Although the temperature of the heat treatment is preferably up to 100 ° C., it can be raised to 100 ° C. or higher using an autoclave or the like as necessary. Note that the heating time may be determined as appropriate.

[(B) Concentration of precursor mixture]
Next, the solution or slurry (precursor mixture) containing all the catalyst raw materials thus obtained is concentrated by a heating device to obtain a concentrate.

  The pressure during concentration can be any of reduced pressure, normal pressure, and increased pressure, but normal pressure is preferred from the economic viewpoint. The shape of the heating device for concentrating is not particularly limited, but it is desirable to perform the heating using a jacket type or an internal coil type. At this time, the heat transfer surface temperature with the heating device during concentration is set to 100 ° C to 150 ° C. It is desirable that the temperature be 120 ° C or higher, and it is desirable that the temperature be 130 ° C or lower. The concentration time is preferably 0.5 to 10 hours, more preferably 2 hours or more, and more preferably 5 hours or less, as the time during which the temperature of the precursor mixture is equal to or higher than the boiling point of the mixture −30 ° C. In order to facilitate temperature control during concentration, it is preferable to use saturated steam of 150 to 700 kPa (absolute pressure; hereinafter, pressure is expressed as absolute pressure) as a heating medium. It is more preferable to use saturated steam of 200 kPa or more, and it is more preferable to use saturated steam of 400 kPa or less. In the case of a stainless steel heating heat transfer surface having a thickness of about 5 mm, the temperature of the heating medium and the temperature of the heating heat transfer surface are substantially equal. Here, the concentration means that the solution or slurry of the precursor mixed solution is heated to lower the liquid content, and the liquid content of the obtained concentrate is 20% by mass or more.

  Even if other known techniques such as a coprecipitation method are used, the flowability of the precursor dried product described later is excellent and methacrylic acid can be obtained in a high yield by carrying out the preparation within the concentration conditions described above. However, good results are obtained particularly with the catalyst of the present invention.

[(C) Drying and baking of concentrate]
Subsequently, the concentrate thus obtained is dried to obtain a dried catalyst precursor.

  As the drying method, various methods can be used, and for example, an evaporating and drying method, a spray drying method, a drum drying method, an air current drying method, and the like can be used. The model of the dryer used for drying, the temperature and time during drying, etc. are not particularly limited, and a dried catalyst precursor according to the purpose can be obtained by appropriately changing the drying conditions.

A fluidity index was used as a method for evaluating the fluidity of the dried catalyst precursor. [Carr, R .; L. , Chem. Eng. 72. Jan. 18 (1965)]
The dried catalyst precursor obtained in this manner may be pulverized if necessary, and then subjected to subsequent firing without molding, but usually the molded product is fired.

  The molding method is not particularly limited, and various known dry and wet molding methods can be applied, but it is preferable to mold without including a carrier such as silica. Specific examples of the molding method include tableting molding, press molding, extrusion molding, and granulation molding. The shape of the molded product is not particularly limited, and for example, a desired shape such as a columnar shape, a ring shape, or a spherical shape can be selected. In molding, a small amount of known additives such as graphite and talc may be added.

  And the dried catalyst precursor obtained in this way or its molded product is fired to obtain a catalyst for producing methacrylic acid.

  The firing method and firing conditions are not particularly limited, and known treatment methods and conditions can be applied. Optimum conditions for calcination vary depending on the catalyst raw material, catalyst composition, preparation method, and the like, but are usually 200 to 500 ° C., preferably 300 to 450 under an oxygen-containing gas flow such as air and / or an inert gas flow. It is carried out at 0 ° 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 reaction activity of the catalyst, and specifically includes nitrogen, carbon dioxide, helium, argon, and the like.

<Method for producing methacrylic acid>
Next, the manufacturing method of methacrylic acid of this invention is demonstrated. The method for producing methacrylic acid of the present invention is a method for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of the catalyst for producing methacrylic acid of the present invention obtained as described above. .

  The gas phase catalytic oxidation reaction is usually performed in a fixed bed. The catalyst layer may be one layer or two or more layers, and may be a catalyst-only layer, a layer in which a catalyst is supported on a carrier, or a layer in which other additive components are mixed.

  When producing methacrylic acid using the above-described catalyst for producing methacrylic acid of the present invention, a raw material gas containing methacrolein and molecular oxygen is brought into contact with the catalyst.

  The concentration of methacrolein in the raw material gas can be varied within a wide range, but is preferably 1% by volume or more, and more preferably 3% by volume or more. Moreover, 20 volume% or less is preferable and 10 volume% or less is more preferable.

  Although it is economical to use air as the molecular oxygen source, air or the like enriched with pure oxygen can also be used if necessary. The molecular oxygen concentration in the raw material gas is preferably 0.4 mol or more, more preferably 0.5 mol or more with respect to 1 mol of methacrolein. Moreover, 4 mol or less is preferable with respect to 1 mol of methacrolein, and 3 mol or less is more preferable.

  Moreover, it is preferable that source gas contains water vapor | steam. When the reaction is carried out in the presence of water, methacrylic acid is obtained in a higher yield. The concentration of water vapor in the raw material gas is preferably 0.1% by volume or more, and more preferably 1% by volume or more. Moreover, 50 volume% or less is preferable and 40 volume% or less is more preferable.

  The source gas may contain a small amount of impurities such as a lower saturated aldehyde, but the amount is preferably as small as possible. Moreover, inert gas, such as nitrogen and a carbon dioxide gas, may be included.

  The flow rate of the raw material gas is not particularly limited, and can be appropriately set so as to have an appropriate contact time. The contact time is preferably 1.5 seconds or longer, and more preferably 2 seconds or longer. Moreover, 15 seconds or less are preferable and 5 seconds or less are more preferable.

  The reaction pressure of the methacrylic acid production reaction is from normal pressure (atmospheric pressure) to 607.8 kPa (absolute pressure). The reaction temperature is preferably 230 ° C or higher, more preferably 250 ° C or higher. Moreover, 450 degrees C or less is preferable and 400 degrees C or less is more preferable.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

In addition, the reaction rate of methacrolein, the selectivity of the produced methacrylic acid, and the single flow yield of methacrylic acid are defined as follows.
Reaction rate (%) of methacrolein (MAL) = (B / A) × 100
Methacrylic acid (MAA) selectivity (%) = (C / B) × 100
Single flow yield (%) of methacrylic acid (MAA) = (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]
(Preparation of solution A)
To 200 parts by mass of pure water, 100 parts by mass of molybdenum trioxide, 6.66 parts by mass of 85 mass% phosphoric acid aqueous solution and 2.70 parts by mass of ammonium metavanadate were added and stirred for 2 hours under reflux to prepare solution A. (The mass ratio of the molybdenum compound to water as the solvent is 1: 2.01).

(Preparation of liquid B)
The liquid B was 36 parts by mass of 29% by mass ammonia water. The amount of ammonium contained in the liquid B was 10 moles with respect to 12 moles of molybdenum atoms contained in the liquid A (the mass ratio of ammonia and the ammonia compound to water as the solvent was 1: 2.45). .

(Preparation of liquid C)
Cesium nitrate 11.28 parts by mass was dissolved in 23.6 parts by mass of pure water to prepare liquid C (the mass ratio of all raw materials contained in liquid C and water as the solvent was 1: 2.09). .

(Preparation of precursor mixture)
After cooling A liquid to 50 degreeC, C liquid was dripped at A liquid, stirring, and also it stirred for 15 minutes, and prepared AC mixed liquid. Next, the B liquid was mixed with the A-C mixed liquid while stirring to prepare an A-C-B mixed liquid. At this time, the liquid temperature was kept at 70 ° C.

  A slurry containing catalyst precursor by adding 2.10 parts of cupric nitrate and 2.34 parts of ferric nitrate while stirring the A-C-B mixed solution thus obtained at a liquid temperature of 50 ° C. A precursor mixed solution) was obtained.

(Concentration, drying, firing of precursor mixture)
This precursor mixed liquid was heated in a stirring jacket with a heating jacket (the tank has an inner diameter of 0.35 m, a depth of 0.45 m, and the heating heat transfer surface is made of SUS316 having a thickness of 5 mm). The mixture was concentrated by heating at 0 ° C. for 3 hours. A saturated water vapor of 300 kPa (absolute pressure) was used as the heating medium. The liquid temperature of the precursor mixture at this time was 100 ° C. The obtained slurry (concentrate, moisture content 50 mass%) is dropped onto a drying drum at 130 ° C. and dried, and the resulting dry powder is compressed into a tableting ring with an outer diameter of 4 mm, an inner diameter of 1 mm, and a height of 4 mm. After molding, it was calcined at 375 ° C. for 10 hours under air flow to obtain a catalyst for producing methacrylic acid. The composition of the obtained catalyst (other than oxygen atoms) was P _1.0 Mo ₁₂ V _0.65 Cu _0.15 Fe _0.1 Cs _0.1 .

(Synthetic reaction of methacrylic acid (continuous reaction test))
This catalyst was charged into a reaction tube, and a mixed gas of 5% methacrolein, 10% oxygen, 30% water vapor, and 55% nitrogen (both volume%) was used under normal pressure, reaction temperature of 285 ° C., and contact time of 3.6 seconds. A continuous reaction test was conducted. The results are shown in Table 1.

(Flowability index of dried catalyst precursor)
For the dry powder obtained by drying the concentrate, the flowability index [Carr, R .; L. , Chem. Eng. 72. Jan. 18 (1965)]. The results are shown in Table 1.

[Example 2]
Similar to Example 1 except that saturated water vapor of 650 kPa (absolute pressure) is used as the heating medium, the heat transfer surface temperature is 150 ° C. (the liquid temperature of the precursor mixture is 100 ° C.), and the heating concentration time is 2 hours. Thus, a catalyst for methacrylic acid production was obtained, and the continuous reaction test and evaluation of the fluidity index of the dried catalyst precursor were performed in the same manner as in Example 1. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

[Example 3]
Example 1 except that saturated water vapor of 180 kPa (absolute pressure) is used as the heating medium, the heating heat transfer surface temperature is 100 ° C. (the liquid temperature of the precursor mixture is 90 ° C.), and the heating concentration time is 5 hours. Thus, a catalyst for methacrylic acid production was obtained, and the continuous reaction test and evaluation of the fluidity index of the dried catalyst precursor were performed in the same manner as in Example 1. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

[Example 4]
The amount of the precursor mixture to be concentrated is reduced to 38 parts by mass (the component ratio of each element in the mixture is the same as in Example 1), and the heat concentration time is 0.25 hours (the liquid temperature of the precursor mixture is 100). The catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that the temperature was changed to 0 ° C.), and the flowability index of the continuous reaction test and the dried catalyst precursor was evaluated in the same manner as in Example 1. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

[Comparative Example 1]
The amount of the precursor mixture to be concentrated is increased to 800 parts by mass (the component ratio of each element in the mixture is the same as in Example 1), 1500 kPa (absolute pressure) saturated steam is used as a heating medium, and heat transfer A catalyst for methacrylic acid production was obtained in the same manner as in Example 1 except that the surface temperature was 200 ° C. (the liquid temperature of the precursor mixture was 100 ° C.) and the heating concentration time was 3 hours. The fluidity index of the reaction test and the dried catalyst precursor was evaluated. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

[Comparative Example 2]
Similar to Example 1 except that saturated water vapor of 1500 kPa (absolute pressure) is used as the heating medium, the heating heat transfer surface temperature is 200 ° C. (the liquid temperature of the precursor mixture is 100 ° C.), and the heating concentration time is 30 minutes. Thus, a catalyst for methacrylic acid production was obtained, and the continuous reaction test and evaluation of the fluidity index of the dried catalyst precursor were performed in the same manner as in Example 1. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

[Comparative Example 3]
Example 1 except that saturated water vapor of 80 kPa (absolute pressure) is used as the heating medium, the heat transfer surface temperature is 85 ° C. (the liquid temperature of the precursor mixture is 70 ° C.), and the heating concentration time is 12 hours. Thus, a catalyst for methacrylic acid production was obtained, and the continuous reaction test and evaluation of the fluidity index of the dried catalyst precursor were performed in the same manner as in Example 1. The results are shown in Table 1. The water content of the concentrate was 50% by mass.

Claims (3)

In a method for producing a methacrylic acid production catalyst containing at least molybdenum and phosphorus, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen,
(A) preparing a solution or slurry (precursor mixture) containing at least a molybdenum raw material and a phosphorus raw material;
(B) concentrating the precursor mixture with a heating device to obtain a concentrate;
(C) drying and baking the concentrate;
And a heating heat transfer surface temperature of the heating device when performing the concentration is 100 to 150 ° C., a method for producing a catalyst for methacrylic acid production.   A catalyst for producing methacrylic acid produced by the method according to claim 1. A method for producing methacrylic acid, comprising subjecting methacrolein to gas phase catalytic oxidation with molecular oxygen in the presence of the catalyst for producing methacrylic acid according to claim 2.