JP2928397B2 - Method for producing unsaturated carboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an unsaturated carboxylic acid from an unsaturated aldehyde, and more particularly to a method for producing methacrylic acid by gas phase catalytic oxidation of methacrolein using a specific catalyst.

[0002]

2. Description of the Related Art
Numerous patents have been proposed for methods of producing unsaturated carboxylic acids by gas phase catalytic oxidation of unsaturated aldehydes. These are mainly methods for producing acrylic acid from acrolein, and claims have been made that include the production of methacrylic acid from methacrolein, but examples of the oxidation reaction of methacrolein are specifically disclosed. Are rare. Even if disclosed, methacrolein oxidation reaction is actually carried out by these catalysts, and in many cases, the combustion reaction of methacrolein is remarkable, and the rate of change, selectivity, and production amount are extremely low in many cases. Was short and impractical.

[0003] On the other hand, a number of catalysts have recently been proposed for a method for producing methacrylic acid from methacrolein. For example, Japanese Patent Application Laid-Open Nos.
However, there is a drawback in that the reaction results are not sufficient, the catalyst activity is greatly reduced with time, and the reaction temperature is too high, and further improvement is desired when used as an industrial catalyst. That is the current situation.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have developed an industrially advantageous catalyst for producing unsaturated carboxylic acids from unsaturated aldehydes, particularly methacrylic acid from methacrolein, which has a high activity and a long catalyst life. As a result of intensive studies, the present inventors have found that, under a specific catalyst composition, the presence of an ammonium group in the catalyst results in a highly practicable catalyst in both activity, selectivity and life, and completed the present invention. .

That is, the present invention relates to an unsaturated aldehyde
To produce unsaturated carboxylic acid by gas phase catalytic oxidation with oxygen
Hit, general formula P_aMo_bV_cCe_dTl_eX_f(NH_Four)_gO_h  (Where P, Mo, V, Ce, Tl, (NH_Four) And O are
Phosphorus, molybdenum, vanadium, cerium,
X represents copper and silver;
At least one selected from the group consisting of a, b, c, d,
e, f, g, and h represent the atomic ratio of each element, and b = 12
A = 0.5-3, c = 0.1-3, d = 0.01-3, e = 0.
01 to 2, f = 0 to 3, and h represents the valence of each component.
Represents the number of oxygen atoms required to satisfy, g is ammonium
G = 0.1-3. )
Using unsaturated carboxylic acid,
It is intended to provide a manufacturing method.

In the present invention, by adding a specific amount of thallium, cerium, an ammonium group and other specific elements to a catalyst containing phosphorus, molybdenum, and vanadium, the activity and selectivity are improved, and the activity is high, so that even at low temperatures, Sufficient conversion can be achieved, and as a result high catalytic activity is maintained over a long period of time, which is of great industrial value.

[0007] The existence state of each component element of the catalyst used in the present invention is extremely complicated and is not strictly clear. However, it is probably that each component element exists as a mixture of a composite oxide and a heteropolyacid salt, and the ammonium group has It is considered that the salt forms a double salt with the heteropolyacid and the heteropolyacid salts.

The method for producing the catalyst used in the present invention does not need to be a special method, and a conventionally well-known preparation method can be employed. For example, a compound containing each component element is mixed and dissolved or decomposed in the presence of water, and the obtained mixed solution or slurry is evaporated to dryness, dried, molded and calcined to obtain a catalyst.

As a raw material compound used for preparing the catalyst, an ammonium compound such as ammonium molybdate, ammonium phosphomolybdate, ammonium metavanadate and a nitrate, carbonate, oxide or the like of each element can be used in combination.

When the catalyst is prepared by dissolving in ammonia water or by adding ammonium nitrate or the like, it is not always necessary to use an ammonium compound as a catalyst raw material.

In producing the catalyst of the present invention, there is no particular limitation on the mixing order of the component compounds. The temperature for mixing is generally 20 to 100 ° C., and the mixing time is not particularly limited as long as mixing can be performed uniformly.
Aging for ~ 20 hours is desirable.

The catalyst precursor slurry thus obtained is concentrated to dryness and then subjected to a calcination step to obtain a catalyst. The calcination condition is preferably 300 to 400 ° C. if in air, but is preferably set in an inert gas stream such as nitrogen. In the case of baking at a temperature of 380 to 450 ° C., the baking is preferably performed. In order to sufficiently exhibit the activity of the present catalyst, it is preferable to perform calcination in an inert gas stream. Examples of the inert gas used include nitrogen, argon, and carbon dioxide. Firing at a high temperature of 400 ° C. or more in air is not preferable because the ammonium group is completely decomposed and the activity is significantly reduced. It is necessary to calcine at 380 to 450 ° C in an inert gas stream and determine the calcining time so that the ammonium group remains in the catalyst component. The lower the firing temperature, the longer the time is required, and generally 0.5 to 20 hours.

Although the catalyst used in the present invention exhibits high activity even without a carrier, it can be used by being supported on a carrier. The carrier used is inert alumina, silica, silicon carbide or the like, but the physical properties of the carrier used are important for sufficiently exhibiting the activity of the catalyst. As the physical properties that the carrier should have, the apparent porosity is 35 to 60%,
Water absorption 20-50%, specific surface area 5 m ² / g or less, particle size 2
~ 10 mm is preferred. In the present invention, the specific surface area is determined by the BET method using a nitrogen gas adsorption method, and the apparent porosity and the water absorption are determined by the following equations according to JIS R-2205.

[0014]

(Equation 1)

[W ₁ : dry weight (g) of 10 g of carrier,
W ₂ : weight of the saturated water sample in water (g); W ₃ : weight of the saturated water sample (g)] The method of loading the catalyst substance on the carrier is as follows. It can be concentrated and dried by a suitable method such as hot air while being rolled using a drum granulator or the like, and supported on a carrier, or the dried catalyst can be supported on a carrier by a centrifugal flow coating device or the like.

In carrying out the present invention, the concentration of the unsaturated aldehyde in the raw material gas can be changed in a wide range.
The range of from about 20% by weight to about 20% by weight is suitable, and particularly preferably from 3 to 10% by weight. The starting unsaturated aldehyde may contain a small amount of impurities such as water and lower saturated aldehyde, and these impurities do not substantially affect the reaction.

Although it is economical to use air as the oxygen source, air enriched with pure oxygen may be used if necessary.
The oxygen concentration in the source gas is regulated by the molar ratio to the unsaturated aldehyde, and this value is preferably from 0.3 to 4, particularly preferably from 0.4 to 2.5.

The raw material gas may be diluted by adding an inert gas such as nitrogen, water vapor or carbon dioxide gas. However, it is economical to use a part of the reaction exhaust gas as the diluting 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. Reaction temperature is 230-400 ° C, preferably 250-360 ° C
Is appropriate. The contact time depends on the reaction temperature,
A suitable time is 0.1 to 15 seconds, preferably 0.5 to 10 seconds.

[0020]

Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited by the examples unless it exceeds the gist of the present invention.

In the examples and comparative examples, the rate of change of methacrolein and the selectivity of methacrylic acid to be formed are defined as follows.

[0022]

(Equation 2)

EXAMPLE 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate and 12.6 g of thallium nitrate were added to 300 m of pure water.
Heat and dissolve in l. 6.2 g of 85% phosphoric acid in pure water 10
Add the one dissolved in ml. On the other hand, a solution is prepared by adding 1.14 g of copper nitrate and 0.81 g of ceric oxide to 30 ml of pure water. This solution is added to the solution with stirring. After aging at 90 ° C. for 15 hours with sufficient stirring, the mixture was evaporated to dryness while heating and stirring at 100 ° C. The dried product was calcined at 420 ° C. for 4 hours in a nitrogen stream to obtain a catalyst. The composition of the elements other than oxygen in the obtained catalyst (the same applies hereinafter) is P _1.5 Mo ₁₂ V _0.5
Ce _0.1 Tl ₁ Cu _0.1 (NH ₄ ) _0.4 .

This catalyst was charged into a reactor, and a mixed gas consisting of 5 mol% of methacrolein, 10 mol% of oxygen, 30 mol% of steam, and 55 mol% of nitrogen was reacted at a reaction temperature of 270 ° C. and a space velocity of 1 mol.
The reaction was performed at 200 hr- ¹ . As a result, a selectivity of methacrylic acid of 88.2% was obtained with a change rate of methacrolein of 87.9%.

Examples 2 to 4 In accordance with Example 1, each catalyst shown in Table 1 below was prepared.
The reaction was carried out under the same reaction conditions as described above to obtain the results shown in Table 1.

[0026]

[Table 1]

Example 5 The slurry obtained in the same manner as in Example 1 was transferred to a dish-type granulator, into which a spherical porous α-alumina having a diameter of 3 mm (Ma-2063 manufactured by Shikishima Malby Co., an apparent porosity of 46%, Water absorption 30
%, Specific surface area of 1 m ² / g or less), and the mixture was rolled and blown with hot air at 60 ° C. to evaporate to dryness. This is 4
The catalyst was obtained by calcining at 20 ° C. for 4 hours in a nitrogen stream. The composition of the elements other than oxygen in the obtained catalyst was P _1.5 Mo ₁₂ V _0.5 C
e _0.1 Tl ₁ Cu _0.1 (NH ₄ ) _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 a conversion of methacrolein of 87.1% and a selectivity of methacrylic acid of 88.5% were obtained.

COMPARATIVE EXAMPLE 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate and 12.6 g of thallium nitrate were added to 300 m of pure water.
Heat and dissolve in l. 6.2 g of 85% phosphoric acid in pure water 10
Add the one dissolved in ml. The mixture was evaporated to dryness while heating and stirring at 100 ° C. This dried product is stored at 420 ° C for 4
The catalyst was obtained by calcining for an hour in an air stream. The composition of the elements other than oxygen in the obtained catalyst was P _1.5 Mo ₁₂ V _0.5 Tl ₁
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 a selectivity of methacrylic acid of 64.5% was obtained with a conversion of methacrolein of 85.7%.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 57/055 B01J 27/24 C07B 61/00 300 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (5)

(57) [Claims] 1. Gas phase contact of unsaturated aldehyde with molecular oxygen
In producing an unsaturated carboxylic acid by catalytic oxidation, a general formula P_aMo_bV_cCe_dTl_eX_f(NH_Four)_gO_h  (Where P, Mo, V, Ce, Tl, (NH_Four) And O are
Phosphorus, molybdenum, vanadium, cerium,
X represents copper and silver;
At least one selected from the group consisting of a, b, c, d,
e, f, g, and h represent the atomic ratio of each element, and b = 12
A = 0.5-3, c = 0.1-3, d = 0.01-3, e = 0.
01 to 2, f = 0 to 3, and h represents the valence of each component.
Represents the number of oxygen atoms required to satisfy, g is ammonium
G = 0.1-3. )
Using unsaturated carboxylic acid,
Production method. 2. A catalyst raw material comprising at least a part thereof containing an ammonium group.
The manufacturing method as described. 3. The process according to claim 1, wherein 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, having an apparent porosity of 35 to 60%, a water absorption of 20 to 50%, and a specific surface area of 5 m ² / g.
2. The method according to claim 1, wherein a catalyst supported on a porous inert carrier having a particle size of 2 to 10 mm is used. 5. The method according to claim 1, wherein the unsaturated aldehyde is methacrolein and the unsaturated carboxylic acid is methacrylic acid.