JP2883454B2 - 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.
No. 3165 and JP-A No. 60-165165 as a catalyst in which a rare earth element is added to molybdovanadophosphoric acid for the purpose of improving the activity.
No. 239439.

[0004] However, disadvantages are that the reaction results are not sufficient, the catalyst activity is greatly reduced with time, the reaction temperature is too high, and the production of the catalyst is complicated because a nitrogen-containing heterocyclic compound is used during the production of the catalyst. At present, further improvements are desired when used as industrial catalysts.

[0005]

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 use of lanthanum and samarium as the catalyst under the well-known catalyst composition mainly composed of molybdovanadophosphoric acid enables practical use in both activity, selectivity and life. The present inventors have found that the catalyst has high catalytic properties 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_cLa_dSm_eCu_fX_gO_h  (Where P, Mo, V, La, Sm, Cu and O are
Phosphorus, molybdenum, vanadium, lantern, summary
X, potassium, rubidium,
Indicates at least one selected from cesium and thallium
And a, b, c, d, e, f, g, and h are the atomic ratios of each element.
A = 0.5-3, c = 0.1-3, when b = 12
d = 0.01-3, e is a value of 1 or less not including 0, f = 0.1
And g = 0.01 to 2, and h is the valence of each of the above components.
Indicates the number of oxygen atoms required to satisfy. Touch represented by)
Production of unsaturated carboxylic acids characterized by using a solvent
It provides a method.

The present invention is characterized in that lanthanum and samarium are used in combination in a catalyst containing phosphorus, molybdenum, vanadium and other specific elements. Since the catalyst used in the present invention has a high activity, a sufficient reaction rate can be achieved even at a low temperature. As a result, a high catalyst activity is maintained over a long period of time, so that the industrial value is extremely large. Although the effect of the combined use of lanthanum and samarium on the catalyst is not clear, it is presumed that the balance between oxidation and reduction probably becomes an ideal state.

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 the raw material compound used for preparing the catalyst, ammonium salts, nitrates, carbonates, halides, oxides and the like of each element can be used in combination.
For example, as a molybdenum raw material, ammonium paramolybdate, molybdenum trioxide, and as a vanadium raw material, ammonium metavanadate, vanadium pentoxide, and the like can be used.

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 calcined to obtain a catalyst. The calcining condition is suitably 300 to 400 ° C. if it is in the air. When baking is performed at a temperature of 380 to 500 ° C., it is desirable. 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 structure of the heteropolyacid is destroyed and the activity is significantly reduced.

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.

[0013]

(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 practicing the present invention, the concentration of unsaturated aldehyde in the raw material gas can be changed in a wide range.
The range of from 20 to 20% by weight is appropriate, and the range of from 3 to 10% by weight is particularly preferable. 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 can 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, but it is economical to partially use the reaction exhaust gas as the diluting gas.

The reaction may be carried out at normal pressure, increased pressure or reduced pressure, but it is generally convenient to carry out the reaction at normal pressure. Reaction temperature is 230-400 ° C, preferably 250-360 ° C
Is appropriate. The contact time depends on the reaction temperature,
0.1 to 15 seconds, preferably 0.5 to 10 seconds is suitable.

[0019]

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 Examples and Comparative Examples, the rate of change of methacrolein and the selectivity of methacrylic acid to be formed are defined as follows.

[0021]

(Equation 2)

Example 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate and 4.8 g of potassium 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. Meanwhile, 1.14 g of copper nitrate, 0.77 g of lanthanum oxide and 0.8 g of samarium oxide were added to 30 ml of pure water.
Prepare the solution added to. 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 450 ° C. for 4 hours in a nitrogen stream to obtain a catalyst. Composition of elements other than oxygen in the obtained catalyst (the same applies hereinafter)
_0.5 P _1.5 Mo ₁₂ V is La _0.1 K ₁ Cu _0.1 Sm _0.1
Met.

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 methacrylic acid selectivity of 86.2% was obtained at a methacrolein change rate of 87.1%.

Examples 2 to 5 Each of the catalysts shown in Table 1 below was prepared according to Example 1, and
The reaction was carried out under the same reaction conditions as described above to obtain the results shown in Table 1.

[0025]

[Table 1]

Example 6 The slurry obtained in the same manner as in Example 1 was transferred to a dish-type granulator, into which spherical porous α-alumina having a diameter of 3 mm (Ma-2063 manufactured by Shikishima Malby Co., apparent porosity 46%, 30% water absorption,
(Specific surface area: 1 m ² / g or less) 100 g was charged, and hot air of 60 ° C. was blown while rolling to evaporate to dryness. 420 ℃
For 4 hours in a nitrogen stream to obtain a catalyst. The composition of the elements other than oxygen in the obtained catalyst was P _1.5 Mo ₁₂ V _0.5 La
_{It was 0.1} K ₁ Cu _0.1 Sm _0.1 .

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 280 ° C., and a selectivity of methacrylic acid of 88.1% was obtained with a conversion of methacrolein of 86.8%.

Comparative Example 1 100 g of ammonium paramolybdate, 2.8 g of ammonium metavanadate and 9.2 g of cesium 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 0.8 g of samarium oxide to 30 ml of pure water. This solution is added to the solution with stirring. Ten
The mixture was evaporated to dryness while heating and stirring at 0 ° C. This dried product 4
The catalyst was obtained by calcining at 50 ° C. for 4 hours in an air stream. The composition of elements other than oxygen in the obtained catalyst was P _1.5 Mo ₁₂ V _0.5
Cs ₁ Cu _0.1 Sm _0.1 .

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 335 ° C., and a selectivity of methacrylic acid of 77.4% was obtained with a conversion of methacrolein of 73.0%.

Claims (2)

(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_cLa_dSm_eCu_fX_gO_h  (Where P, Mo, V, La, Sm, Cu and O are
Phosphorus, molybdenum, vanadium, lantern, summary
X, potassium, rubidium,
Indicates at least one selected from cesium and thallium
And a, b, c, d, e, f, g, and h are the atomic ratios of each element.
A = 0.5-3, c = 0.1-3, when b = 12
d = 0.01-3, e is a value of 1 or less not including 0, f = 0.1
And g = 0.01 to 2, and h is the valence of each of the above components.
Indicates the number of oxygen atoms required to satisfy. Touch represented by)
Production of unsaturated carboxylic acids characterized by using a solvent
Method. 2. The method according to claim 1, wherein the unsaturated aldehyde is methacrolein and the unsaturated carboxylic acid is methacrylic acid.