JPH04257539A - Produciton of unsaturated carboxylic acid - Google Patents

Abstract

PURPOSE:To industrially and advantageously produce an unsaturated carboxylic acid from an unsaturated aldehyde using a catalyst having high practicality of all the activity, selectivity and life. CONSTITUTION:An unsaturated aldehyde such as methacrolein is catalytically oxidized with molecular oxygen in the vapor phase to produce an unsaturated carboxylic acid such as methacrylic acid. In the process, a catalyst expressed by the general formula PaMobVcCedTleXf(NH4)gOh [P, Mo, V, Ce, Tl, (NH4) and O respectively represent phosphorus, molybdenum, vanadium, cerium, thallium, ammonium group and oxygen; X represents at least one selected from silver and copper; (a), (b), (c), (d), (e), (f), (g) and (h) are atomic ratios of the respective elements; when (b) is 12, (a) is 0.5-3; (c) is 0.1-3; (d) is 0.01-3; (e) is 0.01-2; (f) is 0-3; (h) represents the number of oxygen atoms required to satisfy the valences of the aforementioned respective components; (g) represents the number of molecules of ammonium groups; (g) is 0.1-3] is used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing unsaturated carboxylic acids from unsaturated aldehydes, and more particularly to a method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein using a specific catalyst.

0002

[Prior art and problems to be solved by the invention] Conventionally,
A large number of patents have been proposed regarding methods for producing unsaturated carboxylic acids by vapor phase catalytic oxidation of unsaturated aldehydes. These are mainly methods for producing acrylic acid from acrolein, and patent claims include the production of methacrylic acid from methacrolein, but no specific example of the oxidation reaction of methacrolein is disclosed. Those that exist are rare. Even if these catalysts are disclosed, when methacrolein is actually oxidized using these catalysts, the combustion reaction of methacrolein is significant in many cases, and the conversion rate, selectivity, and production amount are often extremely low, and the lifespan is short. was too short and impractical.

[0003] On the other hand, in recent years, many catalysts have been proposed for the production of methacrylic acid from methacrolein. For example, JP-A-50-41811, JP-A-53
-3165, etc., but it has drawbacks such as insufficient reaction results, large decrease in catalyst activity over time, and too high reaction temperature, and further improvements are desired when used as an industrial catalyst. The current situation is that

0004

[Means for Solving the Problems] The present inventors developed a catalyst with high activity and long catalyst life in order to industrially advantageously produce methacrylic acid from unsaturated carboxylic acid from unsaturated aldehyde, especially methacrolein. As a result of intensive studies, we discovered that by having an ammonium group present in a catalyst under a specific catalyst composition, a highly practical catalyst with high activity, selectivity, and service life can be obtained, and the present invention was completed. .

That is, in the present invention, in producing an unsaturated carboxylic acid by gas phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen, the general formula Pa Mob Vc Ced Tle Xf (NH4
)g Oh (where P, Mo, V, Ce, Tl, (NH
4) and O are phosphorus, molybdenum, vanadium, respectively.
Indicates cerium, thallium, ammonium group and oxygen,
X represents at least one selected from copper and silver, a,
b, c, d, e, f, g, h represent the atomic ratio of each element, when b = 12, a = 0.5 ~ 3, c = 0.1 ~ 3
, d = 0.01-3, e = 0.01-2, f = 0-3, h represents the number of oxygen atoms necessary to satisfy the valence of each component, and g represents the ammonium group. represents the number of molecules of
g=0.1 to 3. ) provides a method for producing an unsaturated carboxylic acid characterized by using a catalyst represented by:

In the present invention, activity and selectivity are increased by adding specific amounts of thallium, cerium, ammonium groups, and other specific elements to a catalyst containing phosphorus, molybdenum, and vanadium. A sufficient reaction rate can be achieved, and as a result, high catalytic activity is maintained over a long period of time, so it is of extremely great industrial value.

[0007] The state of existence of each component element in the catalyst used in the present invention is extremely complex and is not strictly clear, but it is likely that each component element exists as a mixture of a complex oxide and a heteropolyacid salt, and the ammonium group is It is thought to form double salts with heteropolyacids and heteropolyacid salts.

The method for producing the catalyst used in the present invention does not need to be a special method, and conventionally well-known preparation methods can be employed. For example, compounds containing each component element are mixed in the presence of water and dissolved or decomposed, the resulting mixed solution or slurry is evaporated to dryness, and after drying, it is shaped and calcined to obtain a catalyst.

[0009] As raw material compounds used for preparing the catalyst, ammonium compounds such as ammonium molybdate, ammonium phosphomolybdate, and ammonium metavanadate can be used in combination with nitrates, carbonates, oxides, etc. of each element.

[0010] Furthermore, when the catalyst is prepared by dissolving it in aqueous ammonia or by adding ammonium nitrate or the like, it is not necessarily necessary to use an ammonium compound as the catalyst raw material.

When producing the catalyst of the present invention, there is no particular restriction on the order in which the component compounds are mixed. The appropriate temperature for mixing is generally 20 to 100°C, and the mixing time is not particularly limited as long as it can be mixed uniformly, but the temperature should be 50 to 100°C after mixing.
It is desirable to age at 100°C for 1 to 20 hours.

The catalyst precursor slurry thus obtained is concentrated to dryness and then subjected to a calcination step to form a catalyst.The appropriate calcination conditions are 300 to 400°C in air, but in an inert gas stream of nitrogen or the like. If firing at 380~4
It is desirable to bake at a temperature of 50°C. In order to fully demonstrate the activity of this catalyst, it is preferable to calcinate it in an inert gas stream. Examples of the inert gas used include nitrogen, argon, carbon dioxide, and the like. Calcining in air at a high temperature of 400° C. or higher is not preferred because the ammonium group is completely decomposed and the activity is significantly reduced. It is necessary to determine the firing time so that ammonium groups remain in the catalyst component by firing at 380 to 450°C in an inert gas flow. The lower the firing temperature, the longer the firing time is required, and generally 0
．． It is 5 to 20 hours.

The catalyst used in the present invention exhibits high activity even without a carrier, but it can also be used supported on a carrier. The carrier used is inert alumina, silica, silicon carbide, etc., but the physical properties of the carrier used are important in order to fully demonstrate the activity of the catalyst. The physical properties that the carrier should have include an apparent porosity of 35 to 60%.
, water absorption rate of 20-50%, specific surface area of 5 m2/g or less,
Preferably, the particle size is 2 to 10 mm. In the present invention, the specific surface area is determined by B. E. T method, and the apparent porosity and water absorption rate are determined according to JIS R-220.
It is calculated using the following formula according to 5.

[0014]

[Math 1]

[W1: dry weight (g) of 10 g of carrier,
W2: Weight of saturated water sample in water (g), W3: Weight of saturated water sample (g)] The method for supporting the catalyst substance on the carrier is to add it to the slurry of the catalyst, and use a dish-type granulator or drum granulator. Concentrate using an appropriate method such as hot air while rolling using a granulator, etc.
The catalyst can be dried and supported on a carrier, or the dried catalyst can be supported on a carrier using a centrifugal fluid coating device or the like.

In carrying out the present invention, the concentration of unsaturated aldehyde in the raw material gas can be varied within a wide range;
A range of 20% by weight is suitable, with 3% to 10% by weight being particularly preferred. The raw material unsaturated aldehyde may contain small amounts of impurities such as water and lower saturated aldehydes, but these impurities do not substantially affect the reaction.

Although it is economical to use air as the oxygen source, air enriched with pure oxygen can also be used if necessary. The oxygen concentration in the raw material gas is regulated by the molar ratio to the unsaturated aldehyde, and this value is 0.3 to 4, especially 0.4 to 4.
2.5 is preferred.

Although the raw material gas may be diluted by adding an inert gas such as nitrogen, steam, or carbon dioxide, it is economical to use a portion of the reaction exhaust gas as the diluent gas.

The reaction may be carried out under normal pressure, increased pressure or reduced pressure, but it is generally convenient to carry out the reaction under normal pressure. The reaction temperature is 230-400℃, preferably 2
A temperature of 50 to 360°C is suitable. The contact time varies depending on the reaction temperature, but is 0.1 to 15 seconds, preferably 0.5 seconds.
~10 seconds is appropriate.

[0020]

[Examples] The present invention will be explained below using specific examples, but the present invention is not limited by these examples unless the gist of the invention is exceeded.

In Examples and Comparative Examples, the rate of change of methacrolein and the selectivity of methacrylic acid produced are defined as follows.

[0022]

[Math 2]

Example 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate, and 12.6 g of thallium nitrate.
Heat and dissolve in 300 ml of pure water. 85% in this solution
A solution of 6.2 g of phosphoric acid dissolved in 10 ml of pure water is added. On the other hand, copper nitrate 1.14g, ceric oxide 0.8
A solution is prepared by adding 1 g to 30 ml of pure water. This solution is added to the above solution with stirring. After aging at 90°C for 15 hours with sufficient stirring, the mixture was evaporated to dryness at 100°C while stirring. This dry product was calcined at 420° C. for 4 hours in a nitrogen stream to obtain a catalyst. The composition of elements other than oxygen in the obtained catalyst (the same applies below) is P1.5 Mo12
V0.5 Ce0.1 Tl1 Cu0.1 (NH4
) was 0.4.

This catalyst was packed in a reactor, and a mixed gas consisting of 5 mol% methacrolein, 10 mol% oxygen, 30 mol% steam, and 55 mol% nitrogen was reacted at a reaction temperature of 270°C and a space velocity of 1200 hr-1. I did it. As a result, a methacrolein conversion rate of 87.9% and a methacrylic acid selectivity of 88.2% were obtained.

Examples 2 to 4 Each catalyst shown in Table 1 below was prepared according to Example 1.
The reaction was carried out under the same reaction conditions as , and the results shown in Table 1 were obtained.

[0026]

[Table 1]

Example 5 The slurry obtained in the same manner as in Example 1 was transferred to a dish-type granulator, and spherical porous α-alumina with a diameter of 3 mm (Ma-2063 manufactured by Shikishima Marubi Co., Ltd., apparent porosity 46%, 100 g of water (water absorption rate: 30%, specific surface area: 1 m2/g or less) was added, and hot air at 60° C. was blown thereon while rolling to evaporate to dryness. This was calcined at 420°C for 4 hours in a nitrogen stream to obtain a catalyst. The composition of elements other than oxygen in the obtained catalyst was P
1.5 Mo12V0.5 Ce0.1 Tl1 Cu
0.1 (NH4)0.3.

Using this catalyst, the reaction was carried out under the same reaction conditions as in Example 1 except that the reaction temperature was changed to 285°C, and the conversion of methacrolein was 87.1% and the methacrylic acid selectivity was 8.
8.5% was obtained.

Comparative Example 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate, and 12.6 g of thallium nitrate.
Heat and dissolve in 300 ml of pure water. 85% in this solution
A solution of 6.2 g of phosphoric acid dissolved in 10 ml of pure water is added. This mixed solution was evaporated to dryness while heating and stirring at 100°C. This dry product was calcined at 420° C. for 4 hours in an air stream to obtain a catalyst. The composition of elements other than oxygen in the obtained catalyst is P1.5 Mo12V0.5 Tl1
Met.

Using this catalyst, the reaction was carried out under the same reaction conditions as in Example 1 except that the reaction temperature was changed to 340°C, and the change rate of methacrolein was 85.7% and the methacrylic acid selectivity was 6.
4.5% was obtained.

Claims (5)

[Claims] Claim 1: In producing an unsaturated carboxylic acid by gas phase catalytic oxidation of an unsaturated aldehyde with molecular oxygen, the general formula Pa Mob Vc Ced Tle Xf (NH
4) g Oh (where P, Mo, V, Ce, Tl, (N
H4) and O represent phosphorus, molybdenum, vanadium, cerium, thallium, ammonium group and oxygen, respectively, X represents at least one selected from copper and silver, and a
, b, c, d, e, f, g, h represent the atomic ratio of each element, and when b = 12, a = 0.5 ~ 3, c = 0.1 ~
3, d=0.01~3, e=0.01~2, f=0~3
where h represents the number of oxygen atoms necessary to satisfy the valence of each component, g represents the number of ammonium group molecules, and g = 0.1 to 3. ) A method for producing an unsaturated carboxylic acid, characterized by using a catalyst represented by: 2. The production method according to claim 1, wherein at least a portion of the catalyst raw material contains an ammonium radical. 3. A method according to claim 1, characterized in that the catalyst is calcined in an inert gas at a temperature in the range of 380 to 450°C. 4. The catalyst composition according to claim 1 is a porous inert material having an apparent porosity of 35 to 60%, a water absorption rate of 20 to 50%, a specific surface area of 5 m2/g or less, and a particle size of 2 to 10 mm. Claim 1 characterized in that a catalyst supported on a carrier is used.
Manufacturing method described. [Claim 5]Claim 1, wherein the unsaturated aldehyde is methacrolein and the unsaturated carboxylic acid is methacrylic acid.
Manufacturing method described.