JP4846397B2 - Catalyst for producing methacrylic acid, method for producing the same, and method for producing methacrylic acid - Google Patents

Description

  The present invention relates to a catalyst for producing methacrylic acid for 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 using the catalyst for producing methacrylic acid.

As a methacrylic acid production catalyst for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen, a heteropolyacid catalyst containing molybdenum and phosphorus is known. As a method for producing a catalyst for producing methacrylic acid, for example, the following method has been proposed.
(1) A method in which a plurality of solutions containing catalyst component elements are mixed within a temperature range of 0 to 25 ° C. and the product is dried (Patent Document 1).
(2) A method of rapidly supplying a plurality of catalyst raw material solutions, stirring and mixing at high speed, and performing heat aging treatment under high speed stirring (Patent Document 2).
(3) A method in which a mixed solution or an aqueous slurry containing a catalyst component is treated with a sound wave of 16000 Hz or higher and then dried and heat-treated (Patent Document 3).
(4) Precipitated particle size by pouring a pouring solution containing an acid or alkali into a reaction mother liquor containing a metal salt and increasing the concentration of the pouring solution stepwise or continuously as the reaction proceeds. To improve the catalyst performance (Patent Document 4).
(5) A method of subjecting agglomerated particles in an aqueous suspension containing molybdenum and silicon to dispersion treatment (homogenizer, ultrasonic wave) (Patent Document 5).

However, the catalyst obtained by the methods (1) to (5) still has insufficient methacrylic acid yield as an industrial catalyst, and further improvement in methacrylic acid yield is desired for use as an industrial catalyst. It is rare.
JP 05-031368 A Japanese Patent Laid-Open No. 07-185354 JP 07-299369 A Japanese Patent Laid-Open No. 08-318153 JP 2003-170052 A

  An object of the present invention is to produce a methacrylic acid production catalyst capable of obtaining a methacrylic acid selectivity and high yield catalyst, a methacrylic acid production catalyst with high methacrylic acid selectivity and yield, and produce methacrylic acid. An object of the present invention is to provide a method for producing methacrylic acid which can be produced with good performance.

  The method for producing a catalyst for producing methacrylic acid according to the present invention is a method for producing a catalyst containing molybdenum, phosphorus, vanadium and an alkali metal, which is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. Then, after adding a sublimable substance to an aqueous slurry or aqueous solution containing molybdenum, phosphorus and vanadium and cooling the aqueous slurry or aqueous solution, an alkali metal compound is added to the aqueous slurry or aqueous solution while stirring the aqueous slurry or aqueous solution. It has the process of producing | generating an aggregate.

The sublimable substance is preferably dry ice.
The temperature at which the alkali metal compound is added to the aqueous slurry or aqueous solution is preferably 30 ° C. or lower.
When stirring the aqueous slurry or aqueous solution, it is preferable to use a high-speed rotary shear stirrer such as a homogenizer.

The resulting catalyst for producing methacrylic acid is preferably a composite oxide represented by the composition formula of the following formula (1).
Mo _a P _b V _c Cu _d X _e Y _f O _g (1).
In the formula, Mo, P, V, Cu and O represent molybdenum, phosphorus, vanadium, copper and oxygen, respectively, and X represents at least one element selected from the group consisting of potassium, rubidium and cesium. , Y is iron, cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin, lead, arsenic, antimony, bismuth, It represents at least one element selected from the group consisting of niobium, tantalum, zirconium, indium, sulfur, selenium, tellurium, lanthanum and cerium, and a, b, c, d, e, f and g are Represents an atomic ratio, and when a = 12, 0.1 ≦ b ≦ 3, 0.01 ≦ c ≦ 3, 0.01 ≦ ≦ 3,0.01 a ≦ e ≦ 3,0 ≦ f ≦ 3, g is the the atomic ratio of oxygen required to satisfy the atomic ratio of each element.

According to the method for producing a methacrylic acid production catalyst of the present invention, a catalyst having a high methacrylic acid selectivity and a high yield can be obtained.
The catalyst for producing methacrylic acid of the present invention has high methacrylic acid selectivity and yield.
According to the method for producing methacrylic acid of the present invention, methacrylic acid can be produced with high productivity.

<Catalyst for methacrylic acid synthesis>
The catalyst for synthesizing methacrylic acid (hereinafter also simply referred to as “catalyst”) of the present invention is a composite oxide containing at least molybdenum, phosphorus, vanadium and an alkali metal. The catalyst preferably contains a heteropolyacid or heteropolyacid salt structure.

  The catalyst is further copper, iron, cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin, lead, arsenic, antimony , Bismuth, niobium, tantalum, zirconium, indium, sulfur, selenium, tellurium, lanthanum, cerium and the like may be contained as appropriate.

As the catalyst, a composite oxide represented by the composition formula of the formula (1) is particularly preferable.
Mo _a P _b V _c Cu _d X _e Y _f O _g (1).
In the formula, Mo, P, V, Cu and O represent molybdenum, phosphorus, vanadium, copper and oxygen, respectively, and X represents at least one element selected from the group consisting of potassium, rubidium and cesium. , Y is iron, cobalt, nickel, zinc, magnesium, calcium, strontium, barium, titanium, chromium, tungsten, manganese, silver, boron, silicon, aluminum, gallium, germanium, tin, lead, arsenic, antimony, bismuth, It represents at least one element selected from the group consisting of niobium, tantalum, zirconium, indium, sulfur, selenium, tellurium, lanthanum and cerium, and a, b, c, d, e, f and g are Represents an atomic ratio, and when a = 12, 0.1 ≦ b ≦ 3, 0.01 ≦ c ≦ 3, 0.01 ≦ ≦ 3,0.01 a ≦ e ≦ 3,0 ≦ f ≦ 3, g is the the atomic ratio of oxygen required to satisfy the atomic ratio of each element.

<Method for producing catalyst for producing methacrylic acid>
The catalyst for synthesizing methacrylic acid according to the present invention adds a sublimable substance to an aqueous slurry or aqueous solution containing molybdenum, phosphorus and vanadium, cools the aqueous slurry or aqueous solution, and then stirs the aqueous slurry or aqueous solution into the aqueous slurry or aqueous solution. It is manufactured by the manufacturing method which has the process of adding an alkali metal compound and producing | generating an aggregate.

  The catalyst for producing methacrylic acid of the present invention includes, for example, a step of preparing an aqueous slurry or aqueous solution containing at least molybdenum, phosphorus and vanadium (preparation step), and adding an aqueous slurry or aqueous solution by adding a sublimable substance to the aqueous slurry or aqueous solution. After cooling, the step of adding an alkali metal compound to the aqueous slurry or aqueous solution while stirring the aqueous slurry or aqueous solution to form an aggregate (aggregation process), and the step of drying the liquid containing the aggregate to obtain a dried product ( It is manufactured through a drying step), a step of shaping a dried product to obtain a shaped product (molding step), and a step of heat-treating the shaped product (heat treatment step).

(Preparation process)
Examples of the preparation method of the aqueous slurry or aqueous solution include known methods such as a coprecipitation method, an evaporation to dryness method, and an oxide mixing method.
As a method for preparing the aqueous slurry or aqueous solution, a method of adding a raw material of each element to water and stirring while heating is preferable from the viewpoint of simplicity. The heating temperature is preferably 80 to 130 ° C, particularly preferably 90 to 130 ° C.

Examples of the raw material for each element include nitrates, carbonates, acetates, ammonium salts, oxides and halides of each element.
Examples of the molybdenum raw material include ammonium paramolybdate, molybdenum trioxide, molybdic acid, and molybdenum chloride.
Examples of the phosphorus raw material include orthophosphoric acid, phosphorus pentoxide, and ammonium phosphate.
Examples of the vanadium raw material include vanadium pentoxide and ammonium metavanadate.

(Aggregation process)
First, the aqueous slurry or aqueous solution heated in the preparation process is cooled. The cooling is performed by adding a sublimable substance directly to the aqueous slurry or solution.
Examples of the sublimable substance include dry ice and sulfur hexafluoride, and dry ice is preferred from the viewpoint of economy and environment.
The amount of the sublimable substance added is preferably 3 to 20 parts by mass, particularly preferably 3 to 10 parts by mass with respect to 100 parts by mass of the aqueous slurry or aqueous solution.

Next, an alkali metal compound is added to the aqueous slurry or aqueous solution while stirring the aqueous slurry or aqueous solution to form an aggregate and precipitate.
The temperature at which the alkali metal compound is added to the aqueous slurry or aqueous solution is preferably 30 ° C. or lower, and more preferably 15 ° C. or lower. The lower limit of the temperature at which the alkali metal compound is added to the aqueous slurry or aqueous solution is not particularly limited as long as the aqueous slurry or aqueous solution does not affect the addition of the alkali metal compound.
When the alkali metal compound is added to the aqueous slurry or aqueous solution, the sublimable substance may or may not remain in the aqueous slurry or aqueous solution.

Examples of the alkali metal compound include a cesium compound, a potassium compound, and a rubidium compound, and a cesium compound is preferable from the viewpoint of thermal stability.
Examples of the cesium compound include cesium bicarbonate, cesium nitrate, and cesium oxide.
What is necessary is just to determine the addition amount of an alkali metal compound suitably according to the composition of the target catalyst.

As the agitator, a rotary agitator such as a rotary blade agitator, a high-speed rotary shear agitator (homogenizer, etc.), a pendulum linear motion agitator, a shaker that shakes the whole container, an ultrasonic wave, or the like was used. A known stirring device such as a vibration type stirrer can be used.
As the stirrer, a rotary stirrer such as a rotary blade stirrer or a high-speed rotary shear stirrer is preferable because the strength of stirring can be easily adjusted and is industrially simple. A high-speed rotary shear stirrer such as a homogenizer is particularly preferable because it can be retained and a catalyst having superior catalytic activity and selectivity can be obtained.

The rotational speed of the stirring blade or the rotary blade in the rotary stirring device may be appropriately adjusted in consideration of the shape of the container, stirring blade, baffle plate, etc., the amount of liquid, etc., to the extent that inconvenience such as liquid scattering does not occur. .
5-40 degreeC is preferable and, as for the temperature of the liquid after alkali metal compound addition, More preferably, it is 5-20 degreeC. The stirring time is preferably 5 to 60 minutes, more preferably 10 to 30 minutes.

  The average particle diameter of the aggregate (aggregated particles) in the aqueous slurry or aqueous solution subjected to the above treatment is preferably 0.1 to 1 μm, particularly preferably 0.1 to 0.5 μm. The average particle diameter of the aggregated particles is a volume-based 50% diameter measured by a laser diffraction particle size distribution measurement method using SALD-7000 manufactured by Shimadzu Corporation.

(Drying process)
The liquid containing the aggregates is heated and dried to obtain a dried product.
Examples of drying methods include known methods such as drum drying, airflow drying, evaporation to dryness, and spray drying.

(Molding process)
Examples of the apparatus used for shaping the dried product include known powder molding machines such as a tableting molding machine, an extrusion molding machine, and a rolling granulator.
There is no restriction | limiting in particular as a shape of a molded article, Arbitrary shapes, such as spherical shape, ring shape, column shape, and star shape, are mentioned.

(Heat treatment process)
The heat treatment conditions are not particularly limited, and known heat treatment conditions can be applied. The heat treatment is usually performed at 200 to 500 ° C., preferably 300 to 450 ° C., for 0.5 hours or more, preferably 1 to 40 hours under the flow of an oxygen-containing gas such as air and / or an inert gas. .

<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 methacrylic acid production catalyst of the present invention obtained as described above. .
The reaction is usually carried out in a fixed bed. Further, the catalyst layer may be one layer or two or more layers. The catalyst for producing methacrylic acid may be supported on a carrier, or may be a mixture of other additive components.

When producing methacrylic acid using the methacrylic acid production catalyst of the present invention, a raw material gas containing methacrolein and molecular oxygen is brought into contact with the catalyst.
The methacrolein concentration in the raw material gas can be varied within a wide range, preferably 1 to 20% by volume, particularly preferably 3 to 10% by volume. The methacrolein may contain a small amount of impurities such as water and lower saturated aldehyde that do not substantially affect this reaction.
The molecular oxygen concentration in the raw material gas is preferably 0.4 to 4 mol, particularly preferably 0.5 to 3 mol, relative to 1 mol of methacrolein.
As the molecular oxygen source, air is preferable from the viewpoint of economy. If necessary, a gas or the like enriched with molecular oxygen by adding pure oxygen to air may be used.

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

The contact time between the raw material gas and the catalyst for producing methacrylic acid is preferably 1.5 to 15 seconds, and more preferably 2 to 5 seconds.
The reaction pressure is preferably from atmospheric pressure to several atmospheres.
The reaction temperature is preferably from 200 to 450 ° C, particularly preferably from 250 to 400 ° C.

  In the method for producing a catalyst for producing methacrylic acid of the present invention described above, a sublimable substance is added to an aqueous slurry or aqueous solution containing molybdenum, phosphorus and vanadium to cool the aqueous slurry or aqueous solution. A catalyst with a high rate and yield can be obtained. The reason for this is that by adding a sublimable substance, the gas generated from the sublimable substance is taken into the agglomerate, causing a local pH change or temperature change, which affects the chemical structure of the final catalyst. It is thought to be because of the effect.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these Examples.
“Parts” in Examples and Comparative Examples means parts by mass.
The catalyst composition was determined from the amount of raw material charged for each element.
The average particle diameter (volume basis 50% diameter) of the aggregated particles was measured by a laser diffraction particle size distribution measurement method using SALD-7000 manufactured by Shimadzu Corporation.

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

[Example 1]
In 400 parts of pure water, 100 parts of molybdenum trioxide, 3.4 parts of ammonium metavanadate, 7.3 parts of 85% by weight phosphoric acid aqueous solution and 5.6 parts of copper nitrate were dissolved, and the temperature was raised to 95 ° C. while stirring. The mixture was warmed and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. 5 parts of dry ice was added to the obtained aqueous slurry, and the mixture was cooled with stirring using a homogenizer. When the aqueous slurry reached 15 ° C., a solution obtained by dissolving 11.2 parts of cesium bicarbonate in 20 parts of pure water was added to the aqueous slurry while stirring using a homogenizer, and further stirred at 15 ° C. for 20 minutes. . The average particle diameter of the aggregated particles in the obtained mixed liquid was 0.46 μm. The mixture was heated to 101 ° C. and evaporated to dryness with stirring. The obtained dried product was further dried at 130 ° C. for 16 hours, and then shaped by pressure molding. The obtained shaped product was heat-treated at 380 ° C. for 5 hours under air flow.
The elemental composition other than oxygen (hereinafter the same) of the obtained catalyst was as follows.
Mo ₁₂ V _0.5 P _1.1 Cu ₁ Cs ₁

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

[Example 2]
When the aqueous slurry reached 30 ° C., a mixed solution was obtained in the same manner as in Example 1 except that the cesium bicarbonate solution was added to the aqueous slurry and the mixture was further stirred at 30 ° C. for 20 minutes. The average particle diameter of the aggregated particles in the obtained mixed liquid was 0.44 μm. A catalyst having the same composition as in Example 1 was obtained in the same manner as in Example 1 except that this mixed solution was used.
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

[Comparative Example 1]
Instead of adding dry ice to the aqueous slurry, a mixed solution was obtained in the same manner as in Example 1 except that the flask containing the aqueous slurry was cooled by immersing it in ice water. The average particle diameter of the aggregated particles in the obtained liquid mixture was 0.39 μm. A catalyst having the same composition as in Example 1 was obtained in the same manner as in Example 1 except that this mixed solution was used.
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

[Comparative Example 2]
Instead of adding dry ice to the aqueous slurry, the flask containing the aqueous slurry was cooled by immersing it in ice water, and when the aqueous slurry reached 50 ° C. using a rotary blade stirrer instead of the homogenizer, the aqueous slurry was bicarbonated. A mixed solution was obtained in the same manner as in Example 1 except that the cesium solution was added and further stirred at 50 ° C. for 20 minutes. The average particle diameter of the aggregated particles in the obtained mixed liquid was 0.84 μm. A catalyst having the same composition as in Example 1 was obtained in the same manner as in Example 1 except that this mixed solution was used.
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 1.

Example 3
In 200 parts of pure water, 100 parts of molybdenum trioxide, 3.4 parts of ammonium metavanadate, and 7.3 parts of 85 mass% phosphoric acid aqueous solution were dissolved, and the temperature was raised to 95 ° C. while stirring, and the liquid temperature was 95. The mixture was stirred for 3 hours while maintaining the temperature. 5 parts of dry ice was added to the obtained aqueous slurry, and the mixture was cooled with stirring using a homogenizer. When the aqueous slurry reaches 15 ° C., a solution obtained by dissolving 11.3 parts of cesium nitrate in 20 parts of pure water and 36.3 parts of aqueous ammonia are added to the aqueous slurry while stirring with a homogenizer, and further 15 Stir at 20 ° C. for 20 minutes. Thereafter, the liquid temperature was raised to 70 ° C., and 5.6 parts of copper nitrate and 1.2 parts of iron nitrate were added. The average particle diameter of the aggregated particles in the obtained mixed liquid was 0.54 μm. The mixture was heated to 101 ° C. and evaporated to dryness with stirring. The obtained dried product was further dried at 130 ° C. for 16 hours, and then shaped by pressure molding. The obtained shaped product was heat-treated at 380 ° C. for 5 hours under air flow.
The elemental composition of the obtained catalyst was as follows.
Mo ₁₂ V _0.5 P _1.1 Cu _0.4 Fe _0.05 Cs ₁

  Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 2.

Example 4
A mixed solution was obtained in the same manner as in Example 3 except that a rotating blade stirrer was used instead of the homogenizer. The average particle diameter of the aggregated particles in the obtained mixed liquid was 4.64 μm. A catalyst having the same composition as in Example 3 was obtained in the same manner as in Example 3 except that this mixed solution was used.
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 2.

[Comparative Example 3]
A rotary blade stirrer was used instead of the homogenizer, and instead of adding dry ice to the aqueous slurry, the flask containing the aqueous slurry was cooled by immersing it in ice water, and when the aqueous slurry reached 50 ° C, the aqueous slurry was cesium nitrate Was added in the same manner as in Example 3 except that the mixture was further stirred at 50 ° C. for 20 minutes. The average particle diameter of the aggregated particles in the obtained mixed liquid was 4.67 μm. A catalyst having the same composition as in Example 3 was obtained in the same manner as in Example 3 except that this mixed solution was used.
Except for using this catalyst, methacrylic acid was produced in the same manner as in Example 1, and the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid were determined. The results are shown in Table 2.

  From the above results, the catalyst obtained by cooling the aqueous slurry containing the catalyst component to 30 ° C. or lower using dry ice, adding the alkali metal compound while stirring with a homogenizer, and precipitating the aggregates is It can be seen that the reaction rate of methacrolein is greatly increased while the acid selectivity is substantially maintained. On the other hand, all of the catalysts of Comparative Examples 1 to 3 which used ice water instead of dry ice for cooling the aqueous slurry had reduced catalytic activity.

The catalyst for producing methacrylic acid of the present invention has a high selectivity and yield of methacrylic acid and is useful for producing methacrylic acid.

Claims (3)

A method for producing a catalyst containing molybdenum, phosphorus, vanadium and an alkali metal, which is used for producing methacrylic acid by vapor phase catalytic oxidation of methacrolein with molecular oxygen,
After adding dry ice to an aqueous slurry or aqueous solution containing molybdenum, phosphorus, and vanadium to cool the aqueous slurry or aqueous solution, an alkali metal compound is added to the aqueous slurry or aqueous solution while stirring the aqueous slurry or aqueous solution to form an aggregate. A process for producing a catalyst for producing methacrylic acid, comprising a step.   A catalyst for producing methacrylic acid produced by the method for producing a catalyst for producing methacrylic acid according to claim 1. A method for producing methacrylic acid, which comprises producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen using the catalyst for producing methacrylic acid produced by the method for producing a catalyst for producing methacrylic acid according to claim 1. .