JPS62161739A - Production of methacrylic acid - Google Patents

Abstract

PURPOSE:To obtain methacrylic acid in high yield, by catalytically oxidizing methacrolein in the vapor phase in the presence of a catalyst containing specific amounts of iron, Sb and another specific element added to a catalyst containing P, Mo, V and copper and having high activity, selectivity and long life. CONSTITUTION:Methacrolein is catalytically oxidized with molecular oxygen in the vapor phase to give methacrylic acid. In the process, a catalyst expressed by formula I (X is at least one selected from K, Rb, Cs and Tl; Y is at least one selected from Te, La, B, Ag, Mg and Ba; a is 0.3-4; c is 0.01-3; d is 0.01-4; e is 0.01-3; f is 0.01-3; g is 0.01-3; h is 0.001-5 when b is 12 and i is the number of oxygen atoms satisfying the valence of each component), e.g. catalyst having the composition of elements other than oxygen is formula II, etc., is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing dimethacrylic acid by vapor phase catalytic oxidation of methacrolein.

Many patents have been proposed. These mainly focus on methods for producing acrylic acid from acrolein, and when the catalysts proposed there are used for producing methacrylic acid, the selectivity is low due to large side reactions.
Moreover, the lifespan was short and it was not practical.

On the other hand, many catalysts have been proposed for the production of methacrylic acid from methacrolein, but all of them are
It has disadvantages such as unsatisfactory reaction performance, large decrease in catalyst activity over time, and too high reaction temperature, and further improvements are desired for use as an industrial catalyst.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a method for advantageously producing methacrylic acid from methacrolein, and in particular, to provide a method for producing methacrylic acid using a catalyst that is highly practical in terms of activity, selectivity, and service life.

[Means for solving problems]

The present invention uses the general formula % formula % (wherein At least one selected element, Y is at least one selected from the group consisting of tellurium, lanthanum, boron, silver, magnesium, and barium.
Indicates the elements of species or higher, a or earth represents the atomic ratio of each element, and when b; 12, a = (13-4, C; α0
1-3, d = 0.01-4, e-α01-3, f-
101-3, g-0,01-3, h-0
,001-5, and 1 is the number of oxygen atoms necessary to satisfy the valence of each component. ) is a method for producing megacrylic acid, which is characterized by using a catalyst represented by:

In the present invention, by adding specific amounts of iron, antimony, and other specific elements to a catalyst containing phosphorus, molybdenum, vanadium, and copper, the activity and selectivity are high (because of the high activity, even at low reaction temperatures). Since a sufficient reaction rate can be achieved and, as a result, high catalytic activity is maintained over a long period of time, a method for producing megacrylic acid of extremely high industrial value can be provided.

The method for producing the catalyst used in the present invention does not need to be limited to a special method, and as long as it does not involve significant uneven distribution of components, conventionally well-known methods such as evaporation to dryness,
Various methods can be used, such as precipitation methods.

As the raw material compounds used for preparing the catalyst, nitrates, carbonates, ammonium salts, halides, oxides, etc. of each element can be used in combination.

Although the catalyst used in the method of the present invention is effective even without a carrier,
It can be supported on an inert carrier such as silica, alumina, silica 7A/l, silicon carbide, etc., or it can be used after being diluted with it.

In carrying out the present invention, the concentration of methacrolein in the raw material gas can be varied within a wide range;
1 is suitable, and 3 to 10 is particularly preferred.

The raw material methacrolein may contain small amounts of impurities such as water and lower saturated aldehydes, but these impurities do not substantially affect the reaction.

It is economical to use air as the oxygen source, but air enriched with pure oxygen can also be used if necessary.

The oxygen concentration in the raw material gas is defined by the mower ratio to methacrolein, and this value is 0.3 to 4, particularly 0.4 to z5.
is preferred.

The raw material gas may be diluted by adding an inert gas such as nitrogen, water vapor, or carbon dioxide gas. The reaction pressure is preferably from normal pressure to several atmospheres. Although the reaction temperature can be selected within the range of 230 to 450°C, 250 to 400°C is particularly preferred. The reaction can be carried out in a fixed bed or in a fluidized bed.

〔Example〕

Hereinafter, a method for preparing a catalyst according to the present invention and a reaction example using the same will be specifically explained.

In Examples and Comparative Examples, parts mean parts by weight, and analysis was performed by gas chromatography. Furthermore, the reaction rate of methacrolein and the selectivity of methacrylic acid produced are defined as follows.

Reaction rate of methacrolein (%;') Selectivity of megacrylic acid (motor of hook-reacted methacrolein/'a) To this was added 2 parts of 85 tyrinic acid a dissolved in 10 parts of pure water, and further 3 parts of Tefi//I/acid 5 dissolved in 20 parts of pure water and anticef trioxide 54. The mixture was heated to 95° C. with stirring.

Then, a solution of 4 parts of steel nitrate and 5.7 parts of ferric nitrate dissolved in 30 parts of pure water was added, and the mixture was heated to 100°C and evaporated to dryness while stirring.

The obtained solid product was dried at 130° C. for 16 hours, pressure molded, and heat-treated at 380° C. for 5 hours under air circulation, which was used as a catalyst.

The composition of elements other than oxygen (the same applies hereinafter) of the obtained catalyst is P
l, 5 MO12VQ, 5 Fe(1,3cuff, 3
It was 5bOJ KI Te6,3. This catalyst was packed into a reactor, and 5 inches of methachloride, 10 inches of oxygen, and 3 inches of water vapor were charged.
0q6, nitrogen 55% (volume %) mixed gas at reaction temperature 2
The temperature was 90°C and the contact time was 56 seconds. When the product was collected and analyzed by gas chromatography, the methacrolein reaction rate was 87.5%, and the methacrolein/L/acid selectivity was 87.3.
%Met.

When the reaction was continued for about 1000 hours under the same conditions, the methacrolein reaction rate was 87.5% and the methacrylic acid selectivity was 87.
．． It was 0%.

Example 2 PI Mo12 MI F130.2 according to Example 1
When a catalyst with the composition Cuo, I 5b ICsl 13o, s was prepared and reacted under the same conditions as in Example 1, the reaction rate of methacrylic acid, loraine was 8% and 5%, and the selectivity of methacrylic acid was 87.
It was 9%.

Example 3 100 parts of ammonium buffmolybdate, 2.8 parts of ammonium metavanadate, and 4.8 parts of potassium nitrate were dissolved in 300 parts of pure water.

8596 for this! A solution of 5.4 parts of phosphoric acid dissolved in 10 parts of pure water was added, and further 4.8 parts of antimony trioxide were added, and the temperature was raised to 95° C. with stirring.

Next, 1.1 parts of copper nitrate, 9.5 parts of ferric nitrate, and 4 parts of silver nitrate dissolved in 40 parts of pure water were added, and the mixture was heated to 100° C. and evaporated to dryness while stirring.

The obtained solid product was dried at 130° C. for 16 hours, pressure molded, and heat-treated at 380° C. for 5 hours under air circulation, which was used as a catalyst.

The elemental composition of the obtained catalyst is PHMo,,V,! ! Fe
6.5 Cuo,t 5t)o,y KI Ago,o
It was s.

When a reaction was carried out using this catalyst under the same reaction conditions as in Example 1, the methacrolein reaction rate was 8 aO% and the methacrylic acid selectivity was 8&7%.

Examples 4 to 11 Each catalyst shown in the table below was prepared according to Example 3, and reacted under the same conditions as in Example 1 to obtain the results shown in the table below.

Comparative Examples 1 to 3 Comparative catalysts shown in the table below were prepared according to Example 1, and
The reaction was carried out under the same conditions as , and the following results were obtained.

-2 Procedural amendment February 2nd, 1986

Claims (1)

[Claims] In producing methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen, the general formula PaMobVcFedCueSbfXgYhOi (wherein, X is selected from the group consisting of potassium, rubidium, cesium, and thallium) is used. At least one element, Y represents at least one element selected from the group consisting of tellurium, lanthanum, boron, silver, magnesium, and barium, a to i represent the atomic ratio of each element, and b = 12, a=0.3~4, c=0.01~3,
d=0.01~4, e=0.01~3, f=0.01~
3, g=0.01-3, h=0.01-5, and i is the number of oxygen atoms necessary to satisfy the valence of each component. ) A method for producing methacrylic acid, characterized by using a catalyst represented by: