JP2000210566A - Catalyst for producing methacrylic acid, its production, and production of methacrylic acid using same catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst capable of producing methacrylic acid at high production yield by gas phase contact oxidation of metacrolein, a production method of the catalyst, and a production method of methacrylic acid. SOLUTION: This catalyst for producing methacrylic acid is produced by heating a catalyst precursor containing at least molybdenum, phosphorus, and vanadium at 350-500 deg.C for 1-30 hours at least two times in the gas ventilation condition, temporarily cooling the catalyst precursor to 250 deg.C or lower between respective heating treatment, and keeping the temperature difference of the respective heating treatment within 30 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation, a method for producing the catalyst, and a method for producing methacrylic acid.

[0002]

2. Description of the Related Art Conventionally, many proposals have been made on catalysts used for producing methacrylic acid by gas phase catalytic oxidation of methacrolein. Molybdenum,
The catalyst containing phosphorus and vanadium is relatively excellent in view of the yield of methacrylic acid. Regarding the heat treatment method in the production process of this catalyst, for example, Japanese Patent Application Laid-Open No. 5-27929
No. 1, JP-A-9-75740, JP-A-9-1
No. 73852 and the like. JP-A-5-2792
Japanese Patent Laid-Open No. 91-75740 discloses a heat treatment under the flow of an oxygen-containing gas having an oxygen concentration of 0.1 to 10% by volume.
In JP-A-9-173852, heat treatment is performed at 180 to 300 ° C in an air flow, then wet shaping is performed, and heat treatment is performed again at 300 to 500 ° C. Methods have been proposed for each. However, catalysts obtained by these methods have problems such as inadequate reaction results and a large decrease in catalytic activity with time, and further improvement is desired as an industrial catalyst. It is the current situation.

[0003]

SUMMARY OF THE INVENTION The present invention provides a catalyst capable of producing methacrylic acid in a high yield by subjecting methacrolein to gas-phase catalytic oxidation, a method for producing the same, and a method for producing methacrylic acid using the catalyst. The purpose is.

[0004]

SUMMARY OF THE INVENTION The present invention provides a method for producing a catalyst containing at least molybdenum, phosphorus and vanadium which is used for producing methacrylic acid by subjecting methacrolein to gas phase catalytic oxidation. At least twice
Heat treatment is performed at a temperature of 350 to 500 ° C. for 1 to 30 hours under a gas flow, and the catalyst precursor is heated at 250 ° C. between each heat treatment.
Once cooled to below, and the difference between heat treatment
It is in the catalyst for producing methacrylic acid which is produced within 0 ° C.

Further, the present invention relates to a method for producing a catalyst containing at least molybdenum, phosphorus and vanadium which is used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation. Perform heat treatment at a temperature of 350 to 500 ° C for 1 to 30 hours under circulation,
There is a method for producing a catalyst for producing methacrylic acid in which the catalyst precursor is once cooled to 250 ° C. or less during each heat treatment, and the difference between the heat treatment temperatures is 30 ° C. or less.

Further, the present invention resides in a method for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation using the above catalyst.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The catalyst used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation according to the present invention contains at least molybdenum, phosphorus and vanadium. There are no particular limitations on the raw materials for preparing this catalyst, and nitrates, carbonates, acetates, ammonium salts, oxides, halides, and the like of each element can be used in combination. For example, as a molybdenum raw material, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride and the like can be used, and as a vanadium raw material, ammonium metavanadate, vanadium pentoxide, vanadium chloride and the like can be used.

The method for producing the catalyst precursor of the catalyst of the present invention from these raw materials for preparing the catalyst does not need to be limited to a special method, and it is well known in the art so long as there is no significant uneven distribution of components. Various methods such as the evaporation to dryness method, the precipitation method, and the oxide mixing method can be used. Then, the mixture containing the catalyst component is compressed into a tableting machine, an extruder,
Spherical, using a general powder molding machine such as a rolling granulator,
It is formed into an arbitrary shape such as a ring (cylindrical), a column, a hollow, and a star. In the present invention, the catalyst precursor refers to a catalyst precursor that has not been subjected to the final heat treatment.

In the method for producing a catalyst of the present invention, the catalyst precursor is heat-treated under a gas flow. The heat treatment is performed at least twice. As the gas used for the heat treatment, the gas used for the first heat treatment and the gas used for the second or subsequent heat treatment may be the same, but may not be the same.
As the type of the gas, a known gas used for the heat treatment of the catalyst precursor, such as an oxygen-containing gas such as air or air containing water vapor or an inert gas such as nitrogen or argon, can be used.

In the present invention, the above heat treatment may be carried out in a usual heating furnace (apparatus). However, in order to simplify the catalyst production process, a catalyst precursor is charged into a reaction tube for producing methacrylic acid, It is preferably performed in a reaction tube.

The space velocity of the flowing gas in the heat treatment of the catalyst precursor (hereinafter, abbreviated as SV) may be the same in each heat treatment, but may be different, depending on the size of the apparatus and furnace used for the heat treatment. It can be freely determined together, but 100 to 30000 h ^-1 is appropriate, and especially 300
A range of from ¹ to 10,000 h ^-1 is preferred. Further, it may be varied during each heat treatment.

The temperature of the heat treatment is 350 to 500 each time.
Within the range of ° C., it can be freely selected according to the type of gas used. The heat treatment is performed at least twice at a temperature in this range. By performing the heat treatment at least twice, the catalytic activity is improved, and the selectivity is maintained substantially the same as in the case of the single treatment, so that the yield of methacrylic acid is improved. The difference between the maximum value and the minimum value of the heat treatment temperature in each time is within 30 ° C. The time of each heat treatment applied to the catalyst precursor is 1 to 30 hours, preferably 1 to 15 hours.

Except for the last heat treatment performed on the catalyst precursor, after each heat treatment under the above conditions,
It is necessary to cool the catalyst precursor to a temperature of 50 ° C. or less, preferably 200 ° C. or less. The time for maintaining the temperature at 250 ° C. or lower can be freely determined, but is preferably in the range of 1 hour to 10 hours. The cooling means does not need to be limited to a special method, and can be performed by various methods such as natural cooling by stopping heating, cooling by flowing a low-temperature flowing gas, and the like. The catalyst that has been subjected to the final heat treatment may or may not be cooled before the reaction.

The present invention is particularly preferably applied to a catalyst having a composition represented by the following general formula. Pa Mob Vc Cud Xe Yf Zg Oh (where P, Mo, V, Cu and O are
Represents phosphorus, molybdenum, vanadium, copper and oxygen; X
Is at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten and boron, and Y is iron, zinc, chromium, magnesium, tantalum,
Z represents at least one element selected from the group consisting of cobalt, manganese, barium, gallium, cerium and lanthanum, and Z represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium. a, b, c, d, e, f, g, and h indicate the atomic ratio of each element, and when b = 12, a = 0.5-3, c
= 0.01-3, d = 0.01-2, e = 0-3, f =
0 to 3, g = 0.01 to 3, and h is an atomic ratio of oxygen necessary to satisfy the valence of each component. )

The catalyst of the present invention may be free of a carrier, or may be supported on an inert carrier such as silica, alumina, silica / alumina, silicon carbide, or diluted with such an inert carrier.

In producing methacrylic acid using the catalyst of the present invention, the concentration of methacrolein in the raw material gas can be varied in a wide range, but is suitably 1 to 20% by volume, and particularly preferably 3 to 20%. A range of 10% is preferred. The source gas may contain impurities such as a lower saturated aldehyde to such an extent that the reaction is not substantially affected.

Oxygen is required in the raw material gas, and it is economically advantageous to use air as the oxygen source. However, if necessary, air enriched with pure oxygen may be used. The amount of oxygen in the source gas is preferably in the range of 0.3 to 4 times mol, particularly 0.4 to 2.5 times mol of methacrolein. The source gas may contain an inert gas such as nitrogen, water vapor, or carbon dioxide.

The pressure of the reaction for producing methacrylic acid from methacrolein is preferably from normal pressure to several atmospheres. The reaction temperature can be selected in the range of 230 to 450 ° C.,
0-400 degreeC is preferable. The reaction can be carried out in a fixed bed or a fluidized bed.

[0019]

The present invention will be specifically described below with reference to examples and comparative examples. In the description, the conversion of methacrolein, the selectivity of methacrylic acid formed and the single-stream yield are defined as follows. “Parts” in the description are parts by weight, and the analysis of the raw material gas and the generated gas was performed by gas chromatography.

[0020]

## EQU00001 ## The reaction rate (%) of methacrolein = A / B.times.100 (A represents the number of moles of reacted methacrolein, and B represents the number of moles of supplied methacrolein.)

## EQU00002 ## Selectivity (%) of methacrylic acid = C / A.times.100 (A is the same as the above "expression 1," and C represents the number of moles of methacrylic acid produced.)

## EQU00003 ## Single-stream yield of methacrylic acid (%) = C / B.times.100 (B is the same as "Equation 1", and C is the same as "Equation 2")

Example 1 100 parts of ammonium paramolybdate, 2.8 parts of ammonium metavanadate and 9.2 parts of cesium nitrate were dissolved in 100 parts of pure water. To this was added a solution in which 8.2 parts of 85% by weight phosphoric acid was dissolved in 30 parts of pure water. Next, a solution prepared by dissolving 1.1 parts of copper nitrate in 30 parts of pure water was added, and the mixture was evaporated to dryness while heating and stirring. The obtained solid was dried at 130 ° C. for 16 hours and then molded under pressure to obtain a catalyst precursor. This catalyst precursor was treated with an inner diameter of 27.
A 5 mm, 1 m long stainless steel pipe was filled and heat-treated at 380 ° C. for 3 hours in an air flow of SV 1000 h ⁻¹ , then cooled to 180 ° C., and heated again to increase the air temperature to SV 1000 h ⁻¹ . The catalyst was prepared by heat treatment at 380 ° C. for 3 hours under circulation. The composition of elements other than oxygen in the obtained catalyst was as follows. Mo ₁₂ P _1.5 Cu _0.1 V _0.5 Cs ₁

This catalyst was filled in a reaction tube, and a mixed gas of 5% methacrolein, 10% oxygen, 30% steam and 55% (volume%) nitrogen was reacted at a reaction temperature of 290 ° C. and a contact time of 3.6.
Seconds passed. The product was collected and analyzed by gas chromatography. The reaction results are shown in Table 1 (the same applies hereinafter).

Comparative Example 1 A catalyst was prepared by heat-treating the same catalyst precursor used in Example 1 at a temperature of 380 ° C. for 6 hours under an air flow of SV 1000 h ^−1.
The reaction was performed in the same manner as described above.

Comparative Example 2 A catalyst was prepared in the same manner as in Example 1 except that the cooling temperature was changed to 260 ° C., and the reaction was carried out in the same manner as in Example 1.

Example 2 A catalyst was prepared in the same manner as in Example 1, except that the first heat treatment time was changed to 2 hours and the second heat treatment time was changed to 5 hours.
The reaction was performed in the same manner as described above.

Example 3 A catalyst was prepared in the same manner as in Example 1 except that the first heat treatment was performed for 4 hours and the second heat treatment was performed for 1.5 hours. Reaction was carried out in the same manner as 1.

Example 4 In Example 1, the first heat treatment temperature was 390 ° C., the second heat treatment temperature was 370 ° C., and the difference between the first heat treatment temperature and the second heat treatment temperature was 20.
A catalyst was prepared in the same manner as in Example 1 except that
The reaction was performed in the same manner as in Example 1.

Comparative Example 3 Same as Example 1 except that the second heat treatment temperature was 355 ° C. for 5 hours and the difference between the first heat treatment temperature and the second heat treatment temperature was 35 ° C. A catalyst was prepared by the same method and reacted in the same manner as in Example 1.

Example 5 100 parts of molybdenum trioxide
2.6 parts of vanadium pentoxide and 6.7 of 85% by weight phosphoric acid
Was added to 800 parts of pure water, and the mixture was heated and refluxed at 100 ° C. for 6 hours. To this was added 1.1 parts of copper nitrate, and the mixture was further heated and refluxed at 100 ° C. for 3 hours. After the reflux, the temperature of the mixture was cooled to 40 ° C.
After adding 11.2 parts of cesium bicarbonate dissolved in 100 parts of pure water, the mixture was heated and evaporated to dryness. The obtained solid was dried at 130 ° C. for 16 hours and then molded under pressure to obtain a catalyst precursor. The catalyst precursor was charged into a reaction tube for producing methacrylic acid, and the reaction was performed under a nitrogen flow of SV 1000 h ^-1.
After a heat treatment at 20 ° C. for 4 hours, the mixture was once cooled to 180 ° C., and heated again to 42 ° C. under a nitrogen flow of SV 1000 h ^−1.
A catalyst was prepared by heat treatment at 0 ° C. for 4 hours. The composition of elements other than oxygen in the obtained catalyst was as follows. Mo ₁₂ P _1.0 Cu _0.1 V _0.5 Cs _{1 Using} this catalyst, a reaction was carried out in the same manner as in Example 1.

Comparative Example 4 The same catalyst precursor as used in Example 5 was heat-treated at a temperature of 430 ° C. for 8 hours under a nitrogen flow of SV 1000 h ⁻¹ to prepare a catalyst.
The reaction was performed in the same manner as described above.

Example 6 In Example 5, the first heat treatment was performed at 400 ° C. for 4 hours under an air flow of SV 1000 h ⁻¹ , and then cooled to 220 ° C., and the first heat treatment temperature and the second heat treatment were performed. A catalyst was prepared in the same manner as in Example 5 except that the heat treatment temperature difference was changed to 20 ° C., and the reaction was carried out in the same manner as in Example 1.

[Example 7] In Example 5, the first heat treatment was performed for 3 hours, and the second heat treatment was performed at SV1000h ^-1.
A catalyst was prepared in the same manner as in Example 5 except that a heat treatment was performed at 395 ° C. for 6 hours under an air flow of 395 ° C., and the difference between the first heat treatment temperature and the second heat treatment temperature was set at 25 ° C. The reaction was performed in the manner described.

Example 8 A catalyst was prepared in the same manner as in Example 5, except that the first heat treatment was performed for 5 hours and the second heat treatment was performed for 2 hours. The reaction was performed in the manner described.

Comparative Example 5 In Example 7, the first heat treatment was performed for 4 hours, the second heat treatment was performed at 340 ° C. for 6 hours, and the difference between the first heat treatment temperature and the second heat treatment temperature was 80.
A catalyst was prepared in the same manner as in Example 5 except that
The reaction was performed in the same manner as in Example 1.

Table 1 summarizes the catalyst preparation conditions and the reaction results using the obtained catalysts in each of the above Examples and Comparative Examples.
It was shown to.

[0036]

[Table 1]

[0037]

The catalyst of the present invention can produce methacrylic acid in high yield by subjecting methacrolein to gas-phase catalytic oxidation. In the production of the catalyst of the present invention, if the heat treatment of the catalyst precursor is performed by filling the reaction tube for producing methacrylic acid, there is an effect that the catalyst production process is simplified.

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Okutake No. 20-1, Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory F-term (reference) 4G069 AA08 BC06B BC31B BC54A BC54B BC59A BC59B BD07A CB17 FB30 FC07 4H006 AA02 AC46 BA12 BA14 BA35 BA81 BC13 BE30 BS10 4H039 CA65 CC30

Claims (4)

[Claims] When producing a catalyst containing at least molybdenum, phosphorus and vanadium used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation, a catalyst precursor is subjected to gas flow at least twice. 350-50
A heat treatment at a temperature of 0 ° C. for 1 to 30 hours, a catalyst precursor is once cooled to 250 ° C. or less during each heat treatment, and a difference in heat treatment temperature of each time is made within 30 ° C. for methacrylic acid production. catalyst. 2. When producing a catalyst containing at least molybdenum, phosphorus and vanadium used for producing methacrylic acid by subjecting methacrolein to gas-phase catalytic oxidation, the catalyst precursor is subjected to gas flow at least twice. 350-50
Heat treatment at a temperature of 0 ° C. for 1 to 30 hours, a catalyst for methacrylic acid production wherein the catalyst precursor is once cooled to 250 ° C. or less during each heat treatment, and a difference in heat treatment temperature of each time is within 30 ° C. Manufacturing method. 3. The method for producing a catalyst according to claim 2, wherein the heat treatment of the catalyst precursor is carried out by filling the reaction tube for producing methacrylic acid. 4. A method for producing methacrylic acid, comprising subjecting methacrolein to gas-phase catalytic oxidation using the catalyst according to claim 1.