JP2009066463A - Method for producing methacrylic acid synthesis catalyst and methacrylic acid synthesis catalyst - Google Patents

Abstract

The present invention provides a method for producing a catalyst for synthesizing methacrylic acid, which can obtain methacrylic acid in a high yield by a gas phase catalytic oxidation reaction of methacrolein.
SOLUTION: Molybdenum, phosphorus, vanadium, copper, and X (X represents one or more atoms selected from potassium, rubidium, cesium, and thallium) and contain 12 atoms of molybdenum. A solid A containing 0.5 to 3 atoms of phosphorus, molybdenum, copper and Y (Y represents one or more atoms selected from silicon, arsenic and germanium); After dry-mixing solid B containing no phosphorus or less than 0.1 atom with respect to 12 atoms of molybdenum, the molded product obtained by molding is fired at 300 ° C. or higher and 500 ° C. or lower.
[Selection figure] None

Description

  The present invention relates to a method for producing a catalyst for use in producing methacrylic acid by vapor phase catalytic oxidation of methacrolein.

  Conventionally, many proposals have been made regarding catalysts used for producing methacrylic acid by gas phase catalytic oxidation of methacrolein. Among these, it is known that a catalyst containing molybdenum, phosphorus and vanadium is relatively excellent in view of the yield of methacrylic acid. As a method for producing these catalysts, a method is generally used in which one type of aqueous slurry containing each metal component is dried, molded, and then fired, but satisfactory results have not always been obtained.

  On the other hand, a catalyst manufacturing method (Patent Document 1) has been reported in which two types of catalyst dry powders prepared from different molybdenum raw materials are dry-mixed and then molded and calcined. According to this method, it is described that the selectivity of methacrylic acid is improved as compared with a catalyst obtained by molding and firing each dry powder alone. A catalyst that improves the selectivity of methacrylic acid by a catalyst obtained by dry-mixing a solid containing molybdenum, phosphorus, or alkali metal and a solid containing molybdenum, phosphorus, and no alkali metal, followed by molding and firing. (Patent Document 2) has been reported.

In the industrial production of methacrylic acid by the gas phase catalytic oxidation reaction of methacrolein, a catalyst capable of further improving the yield is desired.
Japanese Patent Laid-Open No. 5-96172 Japanese Patent Laid-Open No. 2003-1111

  The subject of this invention is providing the manufacturing method of the catalyst which can obtain methacrylic acid with a high yield by the vapor phase catalytic oxidation reaction of methacrolein.

  The present invention includes molybdenum, phosphorus, vanadium, copper, and X (X represents one or more atoms selected from potassium, rubidium, cesium, and thallium), with respect to 12 atoms of molybdenum. A solid A containing 0.5 to 3 atoms of phosphorus, molybdenum, copper and Y (Y represents one or more atoms selected from silicon, arsenic and germanium); Methacrylic acid that is obtained by dry-mixing solid B containing no phosphorus or less than 0.1 atoms with respect to 12 atoms of molybdenum and then molding the resulting product at 300 ° C. or more and 500 ° C. or less. The present invention relates to a method for producing a synthesis catalyst.

  According to the method for producing a catalyst for synthesizing methacrylic acid of the present invention, a catalyst capable of obtaining methacrylic acid in high yield can be obtained by subjecting methacrolein to gas phase catalytic oxidation with molecular oxygen.

  The method for producing a catalyst for synthesizing methacrylic acid of the present invention is molybdenum, phosphorus, vanadium, copper and X (X represents one or more atoms selected from potassium, rubidium, cesium and thallium.) A solid A containing 0.5 to 3 atoms of phosphorus with respect to 12 atoms of molybdenum, molybdenum, copper and Y (where Y is one or more selected from silicon, arsenic and germanium) A solid product B that contains 12 atoms of molybdenum and does not contain phosphorus or contains less than 0.1 atom, and then is molded at 300 ° C. It is characterized by firing at 500 ° C. or lower.

  In the method for producing a catalyst for synthesizing methacrylic acid of the present invention, the solid A to be used contains molybdenum, phosphorus, vanadium, copper, and X, and contains 0.5 atom or more and 3 atoms or less of phosphorus with respect to 12 atoms of molybdenum. . By containing phosphorus atoms in this range with respect to molybdenum atoms, a catalyst capable of obtaining methacrylic acid in a high yield in the gas phase catalytic oxidation reaction of methacrolein can be produced. X represents one or more atoms selected from potassium, rubidium, cesium and thallium. As solid A, what has an atomic composition represented by Formula (2) is preferable.

Mo _a2 P _b2 V _c2 Cu _d2 X _e2 Z _g2 O _h2 (2)
In the formula (2), X represents one or more atoms selected from potassium, rubidium, cesium and thallium. Z is one or more selected from antimony, bismuth, zirconium, tellurium, silver, selenium, tungsten, boron, iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium and lanthanum. The atom of a2 to e2, g2 and h2 indicate the composition ratio of each atom. When a2 is 12, b2 is 0.5 or more and 3 or less, c2 is 0.01 or more and 3 or less, d2 is 0.01 or more and 2 or less, e2 Represents 0.01 or more and 3 or less, g2 represents 0 or more and 3 or less, and h2 represents the number of oxygen atoms necessary to satisfy the valence of the entire metal atom.

  The solid A having such a composition often has a heteropolyacid salt structure, but is not limited to one having a heteropolyacid salt structure. Any form of the solid A may be used, but a powder form is preferable.

  For the preparation of such a solid A, the following raw materials can be used. Each metal atom can be used in appropriate combination as nitrate, carbonate, acetate, ammonium salt, oxide, halide, and the like. As molybdenum, for example, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride or the like can be used as a molybdenum raw material, and molybdenum trioxide is particularly preferable. As the phosphorus, for example, phosphoric acid, phosphorous acid, phosphorus oxide, phosphorus pentachloride and the like can be used as a phosphorus raw material.

  The method for preparing the solid A using the above raw materials is not particularly limited, and various methods such as a coprecipitation method, an evaporation to dryness method, and an oxide mixing method can be used. In addition, a method of drying an aqueous slurry containing molybdenum, phosphorus, vanadium, copper and X is preferable. Although it does not specifically limit as a drying method of aqueous slurry, A box-type dryer, a spray dryer, a drum dryer, a slurry dryer etc. are mentioned as a dryer to be used. In addition, the solid substance A should just be a solid substance substantially, and even if it contains a water | moisture content, it does not interfere. As a medium used for the aqueous slurry, water or an aqueous medium containing alcohol, acetone or the like in water can be used.

  In the method for producing a catalyst for synthesizing methacrylic acid of the present invention, the solid B to be used contains molybdenum, copper and Y, and does not contain phosphorus or contains less than 0.1 atom with respect to 12 atoms of molybdenum. By containing phosphorus atoms in this range without containing phosphorus atoms or molybdenum atoms, a catalyst capable of obtaining methacrylic acid in a high yield in the gas phase catalytic oxidation reaction of methacrolein can be produced. Y represents one or more atoms selected from silicon, arsenic, and germanium. What has an atomic composition represented by Formula (3) is preferable.

Mo _a3 P _b3 V _c3 Cu _d3 X _e3 Y _f3 Z _g3 O _h3 (3)
In formula (3), X represents one or more atoms selected from potassium, rubidium, cesium and thallium. Y represents one or more selected from silicon, arsenic and germanium. Z is one or more selected from antimony, bismuth, zirconium, tellurium, silver, selenium, tungsten, boron, iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium and lanthanum. The elements of a3 to h3 indicate the composition ratio of each atom. When a3 is 12, b3 is 0 or more and less than 0.1, c3 is 0 or more and 3 or less, d3 is 0.01 or more and 2 or less, e3 is 0 or more and 3 or less, f3 represents 0.01 or more and 3 or less, g3 represents 0 or more and 3 or less, and h3 represents an oxygen atom necessary for satisfying the valence of the entire metal atom. In formula (3), the atoms represented by X and Z may be the same as or different from the atoms represented by X and Z in formula (2) representing the atomic composition of solid A.

  The solid B having such a composition can have a heteropolyacid salt structure by adjusting the pH as described later, but is not limited to one having a heteropolyacid salt structure.

  Although it does not specifically limit in preparation of the solid substance B, Like the solid substance A, various methods, such as a coprecipitation method, the evaporation-drying method, and an oxide mixing method, can be used. Moreover, the method of drying the aqueous slurry containing molybdenum, copper, and Y is preferable. The drying method of the aqueous slurry is not particularly limited, and a box-type dryer, a spray dryer, a drum dryer, a slurry dryer, or the like can be used similarly to the solid A. In addition, the solid substance B should just be a solid substance substantially, and even if it contains a water | moisture content, it does not interfere. Moreover, although a form is not limited, a powder form is preferable. Examples of the preparation method of the aqueous slurry include a method in which each metal atom is nitrate, carbonate, acetate, ammonium salt, oxide, halide, etc., and these are appropriately combined and dispersed in an aqueous medium. As the molybdenum, compounds similar to those exemplified as the molybdenum raw material that can be used in the solid A can be used as the molybdenum raw material, and among these, molybdenum trioxide is particularly preferable. The aqueous slurry preferably has a pH of 2 or more and 9 or less, more preferably a pH of 3 or more and 7 or less. When the pH of the aqueous slurry is within this range, it is preferable that the solid B is considered to form a heteropolyacid salt structure. The pH of the aqueous slurry can be adjusted by adding an alkali, and it is preferable to use ammonia as the alkali because it is decomposed and removed by a subsequent baking step.

  As a method for dry-mixing the solid A and the solid B, any method may be used as long as these solids are mixed substantially without using a liquid medium. A method of uniformly mixing the solid B with a powder mixer is preferable.

  In the dry mixing, an additive can be appropriately added as necessary within a range not inhibiting the functions of the solid A and the solid B. As additives, for example, inorganic salts such as barium sulfate and ammonium nitrate, lubricants such as graphite, etc. for the purpose of controlling the specific surface area, pore volume and pore distribution of the resulting molded article with good reproducibility and increasing mechanical strength. And organic substances such as cellulose, starch, polyvinyl alcohol and stearic acid, hydroxide sols such as silica sol and alumina sol, inorganic fibers such as whiskers, glass fibers and carbon fibers.

  A mixture of the solid A and the solid B is formed. As the molding method, various molding methods such as tableting molding, extrusion molding and granulation can be used. The shape of the molded product may be any of, for example, a spherical shape, a cylindrical shape, a ring shape, and a plate shape.

  The molded product thus obtained is fired at 300 ° C. or higher and 500 ° C. or lower. Calcination can usually be carried out under the flow of an oxygen-containing gas such as air, under the flow of an inert gas, or under the flow of a mixed gas thereof. The firing time can be appropriately selected depending on the water content of the solids A and B, the size of the molded product, and the like, and can be, for example, 0.5 hours or longer, preferably 1 hour to 40 hours or shorter. Remaining metal atom salts are decomposed by firing the molded product to form a metal into an oxide.

  The methacrylic acid synthesis catalyst thus obtained preferably has an atomic composition represented by the formula (1).

Mo _a1 P _b1 V _c1 Cu _d1 X _e1 Y _f1 Z _g1 O _h1 (1)
In the formula (1), X represents one or more atoms selected from potassium, rubidium, cesium and thallium. Y represents one or more atoms selected from silicon, arsenic, and germanium, and Z represents antimony, bismuth, zirconium, tellurium, silver, selenium, tungsten, boron, iron, zinc, chromium, magnesium, tantalum , Cobalt, manganese, barium, gallium, cerium, and lanthanum, showing one or more atoms. a1 to h1 indicate the composition ratio of each atom. When a1 is 12, b1 is 0.5 or more and 3 or less, c1 is 0.01 or more and 3 or less, d1 is 0.01 or more and 2 or less, and e1 is 0.01. 3 or less, f1 is 0.01 or more and 3 or less, g1 is 0 or more and 3 or less, and h1 is the number of oxygen atoms necessary to satisfy the valence of the entire metal element. The catalyst having such an atomic composition preferably contains a heteropolyacid or a heteropolyacid salt.

  Next, a method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein using the catalyst thus obtained will be described.

  For the gas phase catalytic oxidation reaction of methacrolein, it is preferable to use a tubular reactor filled with a catalyst, and a multitubular reactor can also be used.

  The methacrolein used for the gas phase catalytic oxidation is preferably used as a raw material gas diluted with an inert gas such as nitrogen or carbon dioxide, water vapor or the like, from an economical viewpoint. The concentration of methacrolein gas in the raw material gas can be varied within a wide range, but is preferably 1% by volume or more and 20% by volume or less, particularly preferably 3% by volume or more and 10% by volume or less. The raw material methacrolein may contain a small amount of impurities that do not substantially affect the reaction, such as water, lower saturated aldehydes, etc., but the raw material gas contains such an impurity derived from methacrolein. It may be.

  As molecular oxygen for oxidizing methacrolein, it is industrially advantageous to use air, but pure oxygen can also be mixed and used as necessary. The oxygen concentration in the raw material gas is defined by the molar ratio to methacrolein, and is preferably 0.3 mol or more and 4 mol or less, particularly preferably 0.4 mol or more and 2.5 mol or less with respect to 1 mol of methacrolein.

  The catalyst charged in the reaction vessel can be diluted with an inert substance such as silica, alumina, silica-alumina, magnesia, titania, silicon carbide or the like, if necessary.

  The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature can be selected in the range of 230 ° C. or higher and 450 ° C. or lower, and particularly preferably 250 ° C. or higher and 400 ° C. or lower. Examples of the contact time between the raw material gas and the catalyst include 1 second to 9 seconds, and preferably 2 seconds to 6 seconds.

  By such a gas phase catalytic oxidation reaction, methacrylic acid can be obtained in a high yield as a product.

  Hereinafter, although the manufacturing method of the catalyst for methacrylic acid synthesis | combination of this invention is demonstrated concretely, the technical scope of this invention is not limited to a following example. Hereinafter, in the examples, “part” means “part by mass”.

  Source gas and product analysis is by gas chromatography.

  The reaction rate of the raw material methacrolein, the selectivity of the produced methacrylic acid, and the yield of the produced methacrylic acid were calculated by the following formulas.

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 supplied metallolein, B is the number of moles of reacted methacrolein, and C is the number of moles of methacrylic acid produced.

[Example 1]
[Preparation of catalyst]
150 parts of molybdenum trioxide and 9.1 parts of ammonium metavanadate were added to 600 parts of pure water. Further, 20.8 parts of 85% phosphoric acid was dissolved in 16 parts of pure water, 2.1 parts of copper nitrate was dissolved in 5 parts of pure water, and 7.5 parts of ferric nitrate was dissolved in 5 parts of pure water. After adding the prepared solution, the mixture was refluxed at 95 ° C. for 2 hours. After the temperature was lowered to 50 ° C., a solution obtained by dissolving 16.8 parts of cesium bicarbonate in 30 parts of pure water was added, and 17.4 parts of ammonium nitrate was further added. The obtained aqueous slurry was evaporated to dryness with heating and stirring, dried at 130 ° C. for 16 hours, and then pulverized to obtain a powdery solid A. The atomic composition excluding oxygen of the obtained solid A was Mo ₁₂ P _2.1 V _1.1 Cu _0.1 Cs _1.0 Fe _0.3 .

Separately, 150 parts of molybdenum trioxide was added to 300 parts of pure water, and then 52.7 parts of 28% ammonia water was added. After heating to 65 ° C., a solution of 21.9 parts of a 60% aqueous arsenic acid solution in 40 parts of pure water was added. Further, a solution in which 2.1 parts of copper nitrate was dissolved in 17 parts of pure water and a solution in which 16.9 parts of cesium nitrate were dissolved in 36 parts of pure water were added. The pH of the obtained aqueous slurry was 6.5. The aqueous slurry was evaporated to dryness while stirring with heating, dried at 130 ° C. for 16 hours, and then pulverized to obtain a powdery solid B. The atomic composition excluding oxygen of the obtained solid B was Mo ₁₂ As _1.1 Cu _0.1 Cs _1.0 .

Next, after 41.7 parts of solid A and 25.0 parts of solid B were mixed well, this mixed powder was pressure-molded and calcined at 380 ° C. for 5 hours under air flow to obtain a catalyst. . The atomic composition of the obtained catalyst excluding oxygen is Mo ₁₂ P _1.3 As _0.4 V _0.7 Cu _0.1 Fe _0.2 Cs ₁ . 0.

[Synthesis of methacrylic acid]
The obtained catalyst was filled in a reaction tube, and a mixed gas of 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 285 ° C. and a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, the reaction rate of methacrolein was 85.0%, the selectivity of methacrylic acid was 87.2%, and the yield of methacrylic acid was 74.1%.

[Example 2]
In the preparation of solid A, 9.1 parts of ammonium metavanadate were changed to 5.7 parts and 16.8 parts of cesium bicarbonate were changed to 27.0 parts, and in the preparation of solid B, molybdenum trioxide was added to pure water. A catalyst was prepared in the same manner as in Example 1 except that 5.7 parts of ammonium metavanadate was added later and cesium nitrate was not used. The atomic composition excluding oxygen of the obtained solid A was Mo ₁₂ P _2.1 V _0.7 Cu _0.1 Cs _1.6 Fe _0.3 , and the atomic composition of the solid B excluding oxygen was Mo ₁₂ As _1.1 V _0.7 Cu _0.1 . Further, the atomic composition excluding oxygen of the obtained catalyst was Mo ₁₂ P _1.3 As _0.4 V _0.7 Cu _0.1 Fe _0.2 Cs _1.0 . As a result of synthesizing methacrylic acid in the same manner as in Example 1, the methacrolein reaction rate was 83.2%, the methacrylic acid selectivity was 86.1%, and the methacrylic acid yield was 71.6%.

[Comparative Example 1]
100 parts of molybdenum trioxide, 3.6 parts of vanadium pentoxide, 8.7 parts of 85% phosphoric acid and 5.5 parts of 65% arsenic acid were added to 400 parts of pure water and mixed. After heating and stirring for 3 hours under reflux, a solution in which 1.1 parts of copper oxide was dissolved in 30 parts of pure water and a solution in which 4.7 parts of ferric nitrate were dissolved in 30 parts of pure water were added. Stirring was performed for a period of time. After the temperature of the slurry was lowered to 50 ° C., 11.2 parts of cesium bicarbonate dissolved in 100 parts of pure water was added, and 5 parts of ammonium carbonate dissolved in 50 parts of pure water was further added. The resulting aqueous slurry was evaporated to dryness while stirring with heating, dried at 130 ° C. for 16 hours, and then pulverized. The dried powder was molded and fired in the same manner as in Example 1 to obtain a catalyst. The atomic composition of this catalyst excluding oxygen was Mo ₁₂ P _1.3 As _0.4 V _0.7 Cu _0.1 Fe _0.2 Cs _1.0 .

  As a result of synthesizing methacrylic acid in the same manner as in Example 1 using the obtained catalyst, methacrolein reaction rate was 73.8%, methacrylic acid selectivity was 87.0%, and methacrylic acid yield was 64.2%. there were.

[Comparative Example 2]
In the preparation of solid A, ammonium metavanadate and cesium bicarbonate were not used, and in the preparation of solid B, molybdenum trioxide was added to pure water, and then 15.2 parts of ammonium metavanadate was added, and cesium nitrate 16.9 was added. A catalyst was prepared in the same manner as in Example 1 except that the part was changed to 45.2 parts. The atomic composition of the obtained solid A excluding oxygen was Mo ₁₂ P _2.1 Cu _0.1 Fe _0.3 , and the atomic composition of the solid B excluding oxygen was Mo ₁₂ As _1.1 V _1.9 Cu _0.1 Cs _2.7 . The elemental composition excluding oxygen of the catalyst was Mo ₁₂ P _1.3 As _0.4 V _0.7 Cu _0.1 Fe _0.2 Cs _1.0 . As a result of synthesizing methacrylic acid in the same manner as in Example 1, the reaction rate of methacrolein was 9%, the selectivity of methacrylic acid was 84.3%, and the yield of methacrylic acid was 7.6%.

Claims (4)

  Including molybdenum, phosphorus, vanadium, copper, and X (X represents one or more atoms selected from potassium, rubidium, cesium, and thallium); Solid A containing 5 atoms or more and 3 atoms or less, molybdenum, copper and Y (Y represents any one or more atoms selected from silicon, arsenic and germanium), and molybdenum 12 atoms On the other hand, a catalyst for synthesizing methacrylic acid in which a molded product obtained by dry-mixing a solid B containing no phosphorus or containing less than 0.1 atom is calcined at a temperature of 300 ° C. to 500 ° C. Production method.   Solid A and solid B are produced using molybdenum trioxide as a molybdenum raw material, and solid B is produced by adjusting a slurry containing metal components to a pH range of 2 to 9 and drying. The method for producing a catalyst for methacrylic acid synthesis according to claim 1. The resulting catalyst for synthesizing methacrylic acid is represented by the formula (1)
Mo _a1 P _b1 V _c1 Cu _d1 X _e1 Y _f1 Z _g1 O _h1 (1)
(In the formula, X represents one or more selected from potassium, rubidium, cesium and thallium, Y represents one or more selected from silicon, arsenic and germanium, and Z represents One or more selected from antimony, bismuth, zirconium, tellurium, silver, selenium, tungsten, boron, iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium and lanthanum , A1 to h1 indicate the composition ratio of each element. When a is 12, b is 0.5 or more and 3 or less, c is 0.01 or more and 3 or less, d is 0.01 or more and 2 or less, and e is 0.00. 01 or more and 3 or less, f is 0.01 or more and 3 or less, g is 0 or more and 3 or less, and h is the number of oxygen atoms necessary to satisfy the valence of the whole metal atom. Claim 1 or 2 method for producing methacrylic acid synthesis catalyst, wherein the having that atomic composition. A catalyst for synthesizing methacrylic acid obtained by the method for producing a catalyst for synthesizing methacrylic acid according to any one of claims 1 to 3.