JPH03167152A - Production of methacrylic acid - Google Patents

Abstract

PURPOSE:To obtain the title compound in an advantageous manner by vapor phase catalytic oxidation of methacrolein with molecular oxygen in the presence of a specific catalyst active for a long period of time which is prepared by introducing gallium into a catalyst containing elements like phosphorus and molybdenum. CONSTITUTION:The objective compound can be obtained by vapor phase catalytic oxidation of methacrolein with molecular oxygen in the presence of a catalyst of the formula (P, Mo, Cu, V, Ga and O are phosphorus, molybdenum, copper, vanadium, gallium and oxygen, respectively; X is arsenic, antimony, zirconium, boron, germanium, tellurium, bismuth, silver, tantalum, iron, chromium, etc.; Y is potassium, rubidium, cesium, etc.; a-h are atom rates for the respective elements, when b=12, a=0.5-3, c=0.01-2, d=0.01-3, e=0.01-1, f=0-3, g=0.01-2, h is the number of the oxygen atoms necessary for satisfying the valences of the above respective components).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a catalyst used in the production of methacrylic acid by gas phase catalytic oxidation of methacrolein.

[Conventional technology]

Conventionally, many proposals have been made regarding methods and catalysts for producing methacrylic acid by gas-phase catalytic oxidation of methacrolein. In particular, since heteropolyacid catalysts were discovered as catalysts for methacrolein oxidation, numerous patents have been proposed for their improvement. For example, JP-A-54-100
313, JP-A No. 61-7233, and JP-A-61-259762, etc., but they have drawbacks such as insufficient reaction results and a large decrease in catalyst activity over time, and are not suitable for industrial use. At present, further improvement is desired when used as a catalyst.

[Purpose of the invention]

The present invention aims to provide a novel catalyst for advantageously producing methacrylic acid from methacrolein.

Means for Solving Problem c] The present invention provides a method for producing methacrylic acid by gas-phase catalytic oxidation of methacrolein with molecular oxygen. Phosphorus, molybdenum, copper, vanadium, gallium and oxygen, respectively, X is arsenic, antimony, zirconium, boron,
kermanium, tellurium, bismuth, silver, tantalum, iron,
At least one element selected from the group consisting of chromium, magnesium, manganese, barium, calcium and cerium, Y represents at least one element selected from the group consisting of potassium, rubidium, cesium and thallium, a, b, cSdSe, f, g and h represent the atomic ratio of each element; when b=12, a=0, 5-3, c=0.
01-2, d-~0.01-3, e=0.5-3, c=
0 to 3, g=o, and 01 to 2, and h is the number of oxygen atoms necessary to satisfy the valence of each component. ) is a method for producing methacrylic acid characterized by using a catalyst represented by:

The present invention is characterized in that a specific amount of gallium is introduced into a catalyst containing phosphorus, molybdenum, copper, vanadium, and other specific elements. As a result, activity and selectivity become higher. That is, since the activity is high, a sufficient yield of methacrylic acid can be achieved even at a lower reaction temperature. As a result, high catalytic activity is maintained over a long period of time, so the industrial value is extremely high.

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

As raw materials used for preparing the catalyst, nitrates, carbonates, acetates, ammonium salts, oxides, halides, and the like of each element can be used in combination. For example, as molybdenum raw materials, ammonium paramolybdate, molybdenum trioxide, molybdic acid, molybdenum chloride, etc. can be used, and as vanadium raw materials, ammonium metavanadate, vanadium pentoxide, vanadium chloride, etc. can be used.

The catalyst used in the present invention may be unsupported, but silica,
It can be supported on an inert carrier such as alumina, silica/alumina, silicon carbide, etc., or it can be used after being diluted with this.

In carrying out the present invention, the concentration of methacrolein in the raw material gas can be varied within a wide range;
% is appropriate, 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 molar ratio to methacrolein,
This value is preferably 0.3 to 4, particularly 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.

The reaction pressure is preferably from normal pressure to several atmospheres. The reaction temperature is 23
It can be selected in the range of 0 to 450℃, especially 250 to 4
00°C is 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, the reaction rate of methacrolein and the selectivity of methacrylic acid produced are defined as follows.

Reaction rate of methacrolein (%) = Selectivity of methacrylic acid (%) = Parts in the following Examples and Comparative Examples are parts by weight, and analysis was performed by gas chromatography.

Example 1 100 parts of ammonium paramolybdate, 4.42 parts of ammonium metavanadate, and 4.77 parts of potassium nitrate were dissolved in 300 parts of pure water. Add to this 85% phosphoric acid 5.4
4 parts of gallium nitrate (Ga content 20.3%) dissolved in 10 parts of pure water were added thereto, and then 1.62 parts of gallium nitrate (Ga content 20.3%) dissolved in 10 parts of pure water were added, and the temperature was raised to 95° C. with stirring.

Next, 3.44 parts of antimony trioxide was added, followed by 1.14 parts of copper nitrate dissolved in 30 parts of pure water, and the mixed solution was evaporated to dryness while heating and stirring. 1 of the obtained solids
After drying at 30°C for 16 hours, it was pressure-molded and molded under air circulation for 38 hours.
The catalyst was heat treated at 0°C for 5 hours and used as a catalyst.

The composition of elements other than oxygen in the obtained catalyst (the same applies hereinafter) is P+Mo+ 2Cuo, +Va, 5Gao, +S
bo, sK+.

This catalyst was packed into a reaction tube, and 5% methacrolein and 1% oxygen were added.
A mixed gas of 0% water vapor, 30% water vapor, and 55% nitrogen (volume %) was passed through the reactor at a reaction temperature of 270° C. and a contact time of 3.6 seconds. When the product was collected and analyzed by gas chromatography, it was found that the methacrolein reaction rate was 90.6% and the methacrylic acid selectivity was 90.0%.

Example 2 100 parts of molybdenum dioxide, 1.57 parts of vanadium pentoxide
3 parts and 6.67 parts of 85% phosphoric acid to 800 parts of pure water.
The mixture was heated to reflux for an hour. Next, 1.09 parts of gallium oxide and 0.92 parts of copper oxide were added, and the mixture was heated under reflux for 2 hours. After cooling this mixture to 50°C, cesium bicarbonate 11.23
Add 10 parts of ammonium nitrate and stir for 10 minutes, then add 10 parts of ammonium nitrate.
A solution of 1 part dissolved in 20 parts of pure water was added and evaporated to dryness while heating. The obtained solid was dried at 120° C. for 16 hours, then pressure-molded, and heat-treated at 380° C. for 3 hours under air circulation, which was then used as a catalyst.

The obtained catalysts are P+MO+zCuo, 2VO, 5Gao, 2cs+
Met.

When a reaction was carried out using this catalyst under the same reaction conditions as in Example 1, the methacrolein reaction rate was 90.5% and the methacrylic acid selectivity was 89.8%.

Examples 3 to 14 Each catalyst shown in the table below was prepared according to Example 1, and reacted under the same conditions as in Example 1 to obtain the results shown in the table below.

Comparative Example 1 Comparative catalyst PtMO+*CLIo, +Vo, 5sbo, sK according to Example 1
+ was prepared and a reaction was carried out using this catalyst under the same reaction conditions as in Example 1, and the methacrolein reaction rate was 80.
．． 8%, and methacrylic acid selectivity was 82.0%.

Procedure support device (voluntary) May 10, 1990

Claims (1)

[Claims] In producing methacrylic acid by gas phase catalytic oxidation of methacrolein with molecular oxygen, the general formula P_aMo_bCu_
cV_dGa_eX_fY_gO_h (P, Mo,
Cu, V, Ga and O are phosphorus, molybdenum, copper, vanadium, gallium and oxygen, respectively; X is arsenic, antimony, zirconium, boron, germanium, tellurium, bismuth, silver, tantalum, iron, chromium, magnesium, manganese and barium , at least one element selected from the group consisting of calcium and cerium, Y 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 represent the atomic ratio of each element, when b = 12, a = 0.5 ~ 3, c = 0.01 ~ 2, d = 0.01 ~
3, e=0.01-2, f=0-3, g=0.01-2
where h 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: