WO2012141076A1 - Method for preparing catalyst for production of methacrylic acid - Google Patents

Abstract

A method for preparing a catalyst which is to be used in producing methacrylic acid from methacrolein by gas-phase catalytic oxidation with molecular oxygen and which contains at least molybdenum and phosphorus as catalyst components, comprising: a step of drying an aqueous mixed fluid that contains raw materials for catalyst components to form a dried substance having an apparent density (X) of 1.00 to 1.80kg/L; and a step of molding the dried substance or a mixture comprising the dried substance to form a molded catalyst that has a density (Y) of 1.60 to 2.40kg/L and an (X)/(Y) ratio of 0.50 to 0.80.

Description

Method for producing a catalyst for methacrylic acid production

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

As a catalyst component of a catalyst for producing methacrylic acid, a heteropolyacid compound typified by phosphomolybdic acid is known. In order to make this catalyst component act effectively in the gas phase catalytic oxidation reaction, many methods for forming an effective pore structure in the catalyst have been proposed.

Patent Document 1 proposes a method of forming a catalyst by adding a macromolecular organic compound such as polymethyl methacrylate or polystyrene that decomposes and vaporizes into a monomer at a relatively low temperature. Patent Document 2 proposes a method for producing a catalyst that forms a dried product of a mixed solution or an aqueous slurry containing a catalyst component, the particle size of which is adjusted to a range of 1 to 250 μm. Patent Document 3 discloses a catalyst having a secondary molding step in which particles including a catalyst component and a liquid are mixed to produce a primary molded product, and the primary molded product is molded into a final shape by a piston molding machine. The manufacturing method of this is proposed.

Japanese Patent Laid-Open No. 04-367737 Japanese Patent Laid-Open No. 08-10621 JP 2003-93882 A

However, it is desired to develop a catalyst that can further improve the yield of methacrylic acid in the gas phase catalytic oxidation reaction of methacrolein.

An object of the present invention is to provide a methacrylic acid production catalyst capable of producing methacrylic acid in a high yield by gas phase catalytic oxidation of methacrolein with molecular oxygen.

The method for producing a catalyst for producing methacrylic acid according to the present invention is used for producing methacrylic acid containing at least molybdenum and phosphorus as catalyst components, which is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. A method for producing a catalyst, comprising: drying an aqueous mixture containing a raw material compound of a catalyst component to produce a dried product having an apparent density (X) of 1.00 to 1.80 kg / L; A molded product or a mixture containing the dried product, the molded product density (Y) is 1.60 to 2.40 kg / L, and the ratio between the apparent density (X) and the molded product density (Y) And a step of producing a catalyst molded body having (X / Y) of 0.50 to 0.80.

According to the present invention, it is possible to provide a methacrylic acid production catalyst capable of producing methacrylic acid in high yield by vapor phase catalytic oxidation of methacrolein with molecular oxygen.

[Catalyst for methacrylic acid production]
The catalyst for producing methacrylic acid according to the present invention is a catalyst for producing methacrylic acid, which is used when producing methacrolein by vapor-phase catalytic oxidation of methacrolein with molecular oxygen and containing at least molybdenum and phosphorus as catalyst components. And manufactured by the method described later.

The composition of the catalyst component constituting the catalyst according to the present invention is not particularly limited as long as it contains at least molybdenum and phosphorus, and can be appropriately selected according to the performance of the target catalyst for producing methacrylic acid. The catalyst for producing methacrylic acid according to the present invention preferably has, for example, a composition represented by the following formula (A).

_{P a Mo b V c Cu d} X e Y f Z g O h (A)
In the formula (A), P, Mo, V, Cu and O represent phosphorus, molybdenum, vanadium, copper and oxygen, respectively. X represents at least one element selected from the group consisting of arsenic, antimony and tellurium. Y is at least one selected from the group consisting of bismuth, germanium, zirconium, silver, selenium, silicon, tungsten, boron, iron, zinc, chromium, magnesium, tantalum, cobalt, manganese, barium, gallium, cerium and lanthanum. Represents an element. Z represents at least one element selected from the group consisting of potassium, rubidium and cesium. a, b, c, d, e, f, g and h represent the atomic ratio of each element. When b = 12, a = 0.1 to 3, c = 0.01 to 3, d = 0. 01-2, e = 0-3, f = 0-3, g = 0.01-3, and h is the atomic ratio of oxygen necessary to satisfy the valence of each element. In addition, the said composition is the value calculated from the raw material preparation amount of each element.

[Method for producing catalyst for producing methacrylic acid]
The method for producing a catalyst for producing methacrylic acid according to the present invention is used for producing methacrylic acid containing at least molybdenum and phosphorus as catalyst components, which is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen. A method for producing a catalyst, comprising: drying an aqueous mixture containing a raw material compound of a catalyst component to produce a dried product having an apparent density (X) of 1.00 to 1.80 kg / L; A molded product or a mixture containing the dried product, the molded product density (Y) is 1.60 to 2.40 kg / L, and the ratio between the apparent density (X) and the molded product density (Y) And a step of producing a catalyst molded body having (X / Y) of 0.50 to 0.80.

It has been found that when X, Y, and X / Y satisfy the range defined by the present invention, the catalytic activity, methacrylic acid selectivity, and methacrylic acid yield are improved in methacrylic acid production. Hereinafter, embodiments of the method according to the present invention will be described.

(Preparation of aqueous mixture containing raw material compounds of catalyst components)
First, the raw material compound of the catalyst component of the catalyst for methacrylic acid production containing at least molybdenum and phosphorus is dissolved or suspended in water to prepare an aqueous mixed solution. The preparation method of the aqueous mixed solution is not particularly limited, and examples thereof include known methods such as a precipitation method and an oxide mixing method.

The raw material compound of the catalyst component used for the preparation of the aqueous mixture is not particularly limited. For example, nitrates, carbonates, acetates, ammonium salts, oxides, halides, oxoacids, oxoacid salts and the like of each constituent element of the catalyst can be used. These can be used alone or in combination of two or more. Examples of molybdenum source compounds include molybdenum oxides such as molybdenum trioxide, and ammonium molybdates such as ammonium paramolybdate and ammonium dimolybdate. Examples of the phosphorus source compound include phosphoric acid, phosphorus pentoxide, and ammonium phosphate. Examples of the vanadium raw material compound include ammonium metavanadate, vanadium pentoxide, and vanadyl oxalate. Examples of the raw material compound for copper include copper nitrate, copper oxide, copper carbonate, and copper acetate. The raw material compound of the catalyst component may be used alone or in combination of two or more for each element constituting the catalyst component.

In addition, the said aqueous liquid mixture may contain ethyl alcohol, acetone, etc. other than water as a solvent.

(Dry)
Next, the obtained aqueous mixed solution containing the raw material compound of the catalyst component is dried. The drying method is not particularly limited, and for example, an evaporation to dry method, a spray drying method (spray drying), a drum drying method, an air current drying method, or the like can be used. Of these, spray drying is preferred.

The apparent density (X) of the dried product in the present invention is in the range of 1.00 to 1.80 kg / L, preferably in the range of 1.00 to 1.60 kg / L, and in the range of 1.00 to 1.50 kg / L. The range is more preferable, and the range of 1.05 to 1.40 kg / L is more preferable. Since the apparent density (X) is in the range of 1.00 to 1.80 kg / L, a sufficient molded body density can be obtained while forming pores effective for selective oxidation of methacrolein. Catalyst activity and methacrylic acid selectivity in methacrylic acid production are improved. When the apparent density (X) is less than 1.00 kg / L, pores effective for the reaction can be formed, but the density of the molded body is reduced during molding, and the amount of catalyst filled in the reaction tube is reduced. Therefore, the reaction rate decreases. On the other hand, when the apparent density (X) is larger than 1.80 kg / L, the catalytic activity and the selectivity of methacrylic acid are lowered. Here, the apparent density (X) is a value measured by the method described in JIS K 7365. That is, the obtained dried product was measured in a 100 mL graduated cylinder, and was calculated from the mass of 100 mL by the following formula.

Apparent density (X) (kg / L (g / mL)) = 100 mL dry substance amount (g) / 100 filled in a graduated cylinder.

Spray drying can be carried out by supplying the aqueous mixture obtained by the above method and hot air to a spray dryer and spraying the aqueous mixture into hot air. Examples of the spraying method of the aqueous mixture include a rotating disk method and a pressure nozzle method. Further, as the hot air, an oxidizing gas such as air may be used, or a non-oxidizing gas such as nitrogen may be used. The apparent density (X) of the obtained dried product is such that the lower the inlet temperature of the hot air, the lower the temperature of the aqueous mixture to be supplied, and the stronger the stirring of the supplied aqueous mixture, the solid content of the aqueous mixture Higher rates tend to be larger. Therefore, these may be adjusted so that the apparent density (X) becomes 1.00 to 1.80 kg / L.

The hot air inlet temperature of the spray dryer is preferably 200 to 400 ° C, more preferably 210 to 370 ° C, still more preferably 220 to 300 ° C, and particularly preferably 230 to 280 ° C.

It is preferable to stir the aqueous mixture before charging the spray dryer as fast as possible. 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 (homogenizer, etc.) is preferable because the strength of stirring can be easily adjusted and is industrially simple. 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, the stirring blade, the baffle plate, etc., the amount of liquid, etc. to such an extent that the liquid does not scatter. The temperature of the aqueous mixture at the time of stirring is preferably 25 ° C. or less, more preferably 20 ° C. or less, further preferably 18 ° C. or less, and particularly preferably 15 ° C. or less. The stirring time is preferably 30 minutes or more, more preferably 40 minutes or more, further preferably 50 minutes or more, and particularly preferably 1 hour or more.

The solid content ratio of the aqueous mixed solution in the present invention is calculated by the following formula from the solid content mass after drying a part of the aqueous mixed solution with a hot air dryer or the like.

Solid content ratio (%) = (solid content after drying aqueous mixture / mass of aqueous mixture before drying) × 100.

The solid content of the aqueous mixed solution is preferably 18% or more, more preferably 20% or more, further preferably 22% or more, and particularly preferably 25% or more. The solid content of the aqueous mixed solution is preferably 50% or less, and more preferably 40% or less.

The average particle size of the dried product is preferably 1 to 250 μm. When the average particle diameter is 1 μm or more, the pore diameter necessary for the oxidation reaction of methacrolein can be ensured, and methacrylic acid can be obtained with a higher yield. Further, when the average particle size is 250 μm or less, the number of contact points between the dried particles per unit volume is not reduced, and a catalyst having sufficient mechanical strength can be obtained. The average particle size of the dried product is more preferably 5 to 150 μm. In addition, an average particle diameter means a volume average particle diameter, and is the value measured with the laser type particle size distribution measuring apparatus.

Further, the contact method between the sprayed liquid droplets and the hot air may be any of parallel flow, counter flow, and co-current flow (mixed flow), and in any case, it can be suitably dried.

The dried product thus obtained may be heat-treated (fired) at 200 to 500 ° C. as necessary to obtain a fired product. The firing conditions are not particularly limited, but the firing is usually performed under a flow of oxygen, air, or nitrogen. The firing time is appropriately set depending on the target catalyst. Hereinafter, the dried product that has not been fired and the fired product are collectively referred to as a dried product. When the heat treatment is performed, the apparent density (X) is measured on the fired product after the heat treatment, and the measured value may be included in the range of the apparent density (X) in the present invention. .

(Preparation of mixture containing dried product)
When extrusion molding is performed in the molding described later, a mixture containing the obtained dried product can be prepared and extrusion molding can be performed. The mixture is not particularly limited as long as it includes the dried product, but the mixture is preferably a kneaded product produced by kneading a liquid and an organic binder into the obtained dried product.

The apparatus used for kneading is not particularly limited. For example, a batch-type kneader equipped with a double-arm type stirring blade, a continuous kneader such as a rotary shaft reciprocating type or a self-cleaning type can be used. . However, a batch-type kneader is preferred from the viewpoint that kneading can be performed while checking the state of the kneaded product. The end point of kneading is the time when mixing is performed until the extrusion molding is possible, and the end point is determined by visual observation or touch.

The liquid is not particularly limited as long as it has a function of wetting the dried product, and examples thereof include water and alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol. Of these, ethyl alcohol and propyl alcohol are preferred from the viewpoint of preventing the particles of the dried product from collapsing and easily forming pores effective for the oxidation reaction. These may use only 1 type and may use 2 or more types together.

The amount of the liquid used is appropriately selected depending on the type and size of the dried product, the type of the liquid, etc., but is preferably 10 to 60 parts by mass with respect to 100 parts by mass of the dried product to be kneaded. When the amount of the liquid used is 10 parts by mass or more, since extrusion can be performed more smoothly, particles of the dried product are less likely to be crushed. Thereby, large voids, that is, large pores are formed in the dried and fired molded article, and the selectivity of methacrylic acid tends to be improved. On the other hand, when the amount of liquid used is 60 parts by mass or less, the adhesion at the time of molding is reduced and the handleability is improved. Further, since the molded product becomes denser, the strength of the molded product tends to be improved. The amount of liquid used is more preferably from 15 to 50 parts by weight, more preferably from 16 to 45 parts by weight, particularly preferably from 20 to 35 parts by weight, based on 100 parts by weight of the dried product to be kneaded. preferable.

The organic binder is not particularly limited, and examples thereof include polymer compounds such as polyvinyl alcohol, α-glucan derivatives, β-glucan derivatives, and the like. These may use only 1 type and may use 2 or more types together.

The α-glucan derivative is a polysaccharide in which glucose is bound in an α-type structure among polysaccharides composed of glucose. Examples thereof include derivatives such as α1-4 glucan, α1-6 glucan, α1-4 / 1-6 glucan and the like. Examples of such α-glucan derivatives include amylose, glycogen, amylopectin, pullulan, dextrin, cyclodextrin and the like. These may use only 1 type and may use 2 or more types together.

The β-glucan derivative is obtained by binding glucose with a β-type structure among polysaccharides composed of glucose. Examples thereof include derivatives such as β1-4 glucan, β1-3 glucan, β1-6 glucan, β1-3 / 1-6 glucan and the like. Examples of such β-glucan derivatives include cellulose derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose (HPMC), hydroxyethylmethylcellulose, hydroxybutylmethylcellulose, and ethylhydroxyethylcellulose. And β1-3 glucan such as curdlan, laminaran, paramylon, callose, pakiman, and scleroglucan. These may use only 1 type and may use 2 or more types together.

The organic binder may be used as it is or after purification. However, when a metal or an ignition residue is contained as an impurity, the catalyst performance may be lowered. Therefore, it is preferable that these contents are smaller.

The amount of the organic binder used is appropriately selected depending on the type and size of the dried product, the type of liquid, etc., but is preferably 0.05 to 15 parts by mass with respect to 100 parts by mass of the dried product to be kneaded. More preferably, the content is 0.1 to 10 parts by mass. There exists a tendency for a moldability to improve when the usage-amount of an organic binder is 0.05 mass part or more. On the other hand, when the amount of the organic binder used is 15 parts by mass or less, the removal process of the organic binder by heat treatment after molding is simplified.

In the kneading, inorganic compounds such as silica, alumina, silica-alumina, silicon carbide, titania, magnesia, graphite and diatomaceous earth, inorganic fibers such as glass fibers, ceramic fibers and carbon fibers, ceramic balls, stainless steel, etc. The inert carrier can be further added and kneaded. These may use only 1 type and may use 2 or more types together.

(Molding)
Next, the dried product or a mixture containing the dried product is molded to produce a catalyst molded body. Examples of the method for forming the dried product include known powder molding such as tableting, extrusion, and rolling granulation. Of these, extrusion molding is preferred. As described above, in the case of extrusion molding, a mixture containing the dried product can be extrusion molded. For the extrusion molding, for example, an auger type extrusion molding machine, a piston type extrusion molding machine or the like can be used. The shape of the catalyst molded body is not particularly limited, and may be any shape such as a ring shape, a cylindrical shape, or a star shape.

In the case of extrusion molding, an extruded product obtained by extrusion molding may be dried to form a catalyst molded body. The drying method is not particularly limited, and for example, generally known methods such as hot air drying, far-infrared drying, and microwave drying can be arbitrarily used. The drying conditions can be appropriately selected as long as the desired moisture content can be achieved. In addition, when this drying is performed with respect to an extruded product, the molded product density (Y) described later is measured on the catalyst molded body after the drying, and the measured value is the molded product density (Y) in the present invention. As long as the value of (X / Y) is included in the range of the present invention.

The molded product density (Y) of the catalyst molded body in the present invention is in the range of 1.60 to 2.40 kg / L, and preferably in the range of 1.65 to 2.30 kg / L. The range of 20 kg / L is more preferable, and the range of 1.75 to 2.10 kg / L is more preferable. In the present invention, the ratio (X / Y) of the apparent density (X) to the molded product density (Y) is in the range of 0.50 to 0.80, preferably in the range of 0.53 to 0.75 kg / L. The range of 0.55 to 0.73 kg / L is more preferable, and the range of 0.57 to 0.70 kg / L is more preferable. Here, the molded product density (Y) is calculated by dividing the mass (kg) per catalyst molded product by the volume (L), performing this on 100 catalyst molded products, and calculating the average value thereof. Value.

When the molded product density (Y) is in the range of 1.60 to 2.40 kg / L, a catalyst filling amount effective for the oxidation of methacrolein can be secured, so that the catalytic activity is improved in the production of methacrylic acid. Further, when the ratio (X / Y) is in the range of 0.50 to 0.80, the amount of pores effective for selective oxidation of methacrolein and the amount of catalyst loading effective for oxidation of methacrolein are reduced. Since securing is compatible, the yield of methacrylic acid improves.

The molded product density (Y) of the catalyst compact tends to increase as the amount of liquid decreases and the molding pressure increases when a liquid is added when preparing the mixture. Therefore, by adjusting these, the molded product density (Y) is 1.60 to 2.40 kg / L, and the ratio (X / Y) of the apparent density (X) to the molded product density (Y) is 0.00. It may be set to 50 to 0.80.

(Baking)
The obtained molded catalyst may be used as it is as a catalyst for producing methacrylic acid, or may be used as a catalyst for producing methacrylic acid after firing.

The firing conditions are not particularly limited, and known firing conditions can be applied. The firing temperature can be 200 to 600 ° C, preferably 200 to 500 ° C, more preferably 300 to 450 ° C. The firing time can be 1 to 24 hours.

[Method for producing methacrylic acid]
The method for producing methacrylic acid according to the present invention is a method for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen in the presence of a catalyst for producing methacrylic acid produced by the method according to the present invention. is there.

The gas phase catalytic oxidation reaction can be performed in a fixed bed. The catalyst layer is not particularly limited, and may be an undiluted layer containing only a catalyst, a diluted layer containing an inert carrier, or a single layer or a mixed layer composed of a plurality of layers.

For the gas phase catalytic oxidation reaction, it is preferable to use a raw material gas containing methacrolein and molecular oxygen. 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. The concentration of methacrolein in the raw material gas is preferably 20% by volume or less, and more preferably 10% by volume or less. 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. Further, the molecular oxygen concentration in the raw material gas is preferably 4 mol or less, more preferably 3 mol or less with respect to 1 mol of methacrolein. 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 raw material gas preferably contains water (water vapor) in addition to methacrolein and molecular oxygen. 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 0.1% by volume or more, and more preferably 1% by volume or more. The concentration of water vapor in the raw material gas is preferably 50% by volume or less, and more preferably 40% by volume or less. 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. The source gas may contain an inert gas such as nitrogen or carbon dioxide.

The reaction pressure of the gas phase catalytic oxidation reaction is preferably from atmospheric pressure (atmospheric pressure) to 5 atmospheres. The reaction temperature is preferably 230 ° C. or higher, more preferably 250 ° C. or higher. The reaction temperature is preferably 450 ° C. or lower, more preferably 400 ° C. or lower. 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 space velocity of the raw material gas is preferably 300 ~ 3000 hr ^-1, more preferably 500 ~ 2000 hr ^-1.

Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited to these examples. The “parts” in the following examples and comparative examples are parts by mass.

The raw material gas and the product were analyzed using gas chromatography. The methacrolein reaction rate, methacrylic acid selectivity, and methacrylic acid yield are defined as follows.

Methacrolein reaction rate (%) = (B / A) × 100
Methacrylic acid selectivity (%) = (C / B) × 100
Methacrylic acid yield (%) = (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.

Further, the apparent density (X) of the dried product, the molded product density (Y) of the catalyst molded body, and the solid content ratio of the slurry (aqueous mixed solution) were measured as follows.

(Apparent density of dried product (X))
The dried product was weighed into a 100 mL measuring cylinder by the method described in JIS K 7365. The apparent density (X) of the dried product was calculated from the mass of 100 mL by the following formula.

Apparent density (X) (kg / L (g / mL)) = 100 mL dry substance amount (g) / 100 filled in a graduated cylinder.

(Catalyst molded product density (Y))
The mass (kg) per catalyst molded product was divided by the volume (L). This calculation was performed on 100 catalyst molded products, and the molded product density (Y) of the catalyst molded product was calculated from the average value.

(Solid content ratio of slurry (aqueous mixture))
300 g of the slurry was dried with a hot air dryer. The solid content rate of the slurry (aqueous mixture) was calculated from the solid content mass after drying by the following formula.

Solid content ratio (%) = (solid content after slurry drying / mass of slurry before slurry drying) × 100.

Example 1
In 400 parts of pure water, 100 parts of molybdenum trioxide, 3.4 parts of ammonium metavanadate, 8.0 parts of 85 mass% phosphoric acid aqueous solution and 1.4 parts of copper nitrate were dissolved. The mixture was heated to 95 ° C. while stirring, and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. After cooling to 85 ° C., a solution obtained by dissolving 14.0 parts of cesium bicarbonate in 20 parts of pure water was added and stirred for 15 minutes while stirring using a rotary blade stirrer. Next, a solution obtained by dissolving 10.7 parts of ammonium nitrate in 20 parts of pure water was added and further stirred for 20 minutes. Then, it heated up to 100 degreeC, stirring a slurry, and concentrated until it became the slurry solid content rate shown in Table 1.

The slurry (aqueous mixed solution) containing the raw material compound of the catalyst component obtained as described above was divided into 20 L portions and stirred. Thereafter, the subdivided slurry was spray-dried under a condition of a rotating disk for slurry spraying at 18,000 rpm using a co-current type spray dryer. Table 1 shows the slurry stirring method, the stirring rotation speed, the stirring time, and the slurry liquid temperature as the stirring conditions of the slurry subdivided into 20 L before spray drying. Table 1 shows the hot air inlet temperature in spray drying and the apparent density (X) of the obtained dried product. In addition, although the slurry solid content rate shown in Table 1 is measured before stirring the subdivided slurry, the value does not change even after stirring.

The dried product thus obtained, HPMC, ethyl alcohol, and pure water were mixed and kneaded with a batch-type kneader equipped with a double-armed sigma blade until it became a clay.

Next, the kneaded mixture was extruded using a piston type extruder. In the extrusion molding, the mixture was molded into a cylindrical shape having an outer diameter of 4.8 mm and a length of 5 mm. This molded body was dried at 90 ° C. for 12 hours to obtain a catalyst molded body. Table 2 shows the amount of each additive and the molded product density (Y) of the obtained catalyst molded body.

Next, the molded catalyst was calcined at 380 ° C. for 18 hours under air flow to obtain a catalyst. The elemental composition other than oxygen (hereinafter the same) of the obtained catalyst was as follows.

_{Mo 12 V 0.5 P 1.2 Cu 0.1} Cs 1.25
The elemental composition is a value calculated from the raw material charge amount of each element.

This catalyst was packed in a stainless steel reaction tube having an outer diameter of 27.5 mm and a height of 6 m having an external heat medium bath so that the catalyst filling length was 5 m. Subsequently, the temperature of the heating medium bath is 285 ° C., and the reaction gas comprising 6% by volume of methacrolein, 12% by volume of oxygen, 10% by volume of water vapor and 72% by volume of nitrogen is passed through the catalyst layer at a space velocity of 1100 hr ^−1. A gas phase catalytic oxidation reaction of methacrolein was performed below. The product 24 hours after the start of the reaction was collected and analyzed by gas chromatography to determine the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid. The results are shown in Table 3.

(Example 2, Comparative Examples 1 to 4)
A catalyst was prepared in the same manner as in Example 1 except that the conditions shown in Tables 1 and 2 were used, and a gas phase catalytic oxidation reaction of methacrolein was performed. The results are shown in Table 3.

(Example 3)
In 400 parts of pure water, 100 parts of molybdenum trioxide, 2.7 parts of ammonium metavanadate, 7.3 parts of 85% by weight phosphoric acid aqueous solution, 7.5 parts of 60% by weight arsenic acid and 2.8 parts of copper nitrate were dissolved. . The mixture was heated to 95 ° C. while stirring, and stirred for 3 hours while maintaining the liquid temperature at 95 ° C. After cooling to 85 ° C., stirring with a rotary blade stirrer, 12.4 parts of cesium bicarbonate dissolved in 20 parts of pure water and 9.2 parts of ammonium carbonate dissolved in 20 parts of pure water were added to 26 parts of pure water. The dissolved solution was added and stirred for an additional 20 minutes. Then, it heated up to 100 degreeC, stirring a slurry, and concentrated until it became the slurry solid content rate shown in Table 1.

The slurry (aqueous mixed solution) containing the raw material compound of the catalyst component obtained as described above was divided into 20 L portions and stirred. Thereafter, the subdivided slurry was spray-dried under a condition of a rotating disk for slurry spraying at 18,000 rpm using a co-current type spray dryer. Table 1 shows the stirring conditions, the drying conditions, and the apparent density (X) of the obtained dried product.

The dried product thus obtained, HPMC, ethyl alcohol, and pure water were mixed and kneaded with a batch-type kneader equipped with a double-armed sigma blade until it became a clay.

Next, the kneaded mixture was extruded using a piston type extruder. In the extrusion molding, the mixture was formed into pellets having an outer diameter of 4.8 mm and a length of 5 mm. This molded body was dried at 90 ° C. for 12 hours to obtain a catalyst molded body. Table 2 shows the amount of each additive and the molded product density (Y) of the obtained catalyst molded body.

Next, the catalyst molded body was calcined at 380 ° C. for 15 hours under air flow to obtain a catalyst. The elemental composition other than oxygen of the obtained catalyst was as follows.

Mo ₁₂ V _0.4 P _1.1 As _0.55 Cu _0.2 Cs _1.1
This catalyst was packed in a stainless steel reaction tube having an outer diameter of 27.5 mm and a height of 6 m having an external heat medium bath so that the catalyst filling length was 5 m. Subsequently, the temperature of the heat medium bath is 285 ° C., and the reaction gas comprising 6% by volume of methacrolein, 12% by volume of oxygen, 10% by volume of water vapor and 72% by volume of nitrogen is passed through the catalyst layer at a space velocity of 1100 hr ^−1. A gas phase catalytic oxidation reaction of methacrolein was performed below. The product 24 hours after the start of the reaction was collected and analyzed by gas chromatography to determine the reaction rate of methacrolein, the selectivity of methacrylic acid, and the yield of methacrylic acid. The results are shown in Table 3.

(Examples 4 to 6, Comparative Examples 5 to 7)
A catalyst was prepared in the same manner as in Example 3 except that the conditions shown in Tables 1 and 2 were used, and a gas phase catalytic oxidation reaction of methacrolein was performed. The results are shown in Table 3.

Further, the reactions of Example 3, Comparative Example 5 and Comparative Example 6 were continuously performed for 2400 hours. The results are shown in Table 4.

As described above, when Examples and Comparative Examples having the same catalyst composition are compared, the apparent density (X) is 1.00 to 1.80 kg / L, and the molded product density (Y) is 1.60 to 2.40 kg / L. In all of the examples where L and (X / Y) were in the range of 0.50 to 0.80, the yield of methacrylic acid was better than that of the comparative example.

Claims (3)

A method for producing a catalyst for producing methacrylic acid, comprising at least molybdenum and phosphorus as catalyst components, which is used for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein with molecular oxygen,
Drying the aqueous mixture containing the raw material compound of the catalyst component to produce a dried product having an apparent density (X) of 1.00 to 1.80 kg / L;
The dried product or a mixture containing the dried product is molded to have a molded product density (Y) of 1.60 to 2.40 kg / L, and the apparent density (X) and the molded product density (Y) And a step of producing a catalyst molded body having a ratio (X / Y) of 0.50 to 0.80. 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.