JP3003821B2 - Method for producing methacrylic acid - Google Patents

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 methacrylic acid by subjecting isobutyric acid to a catalytic oxidative dehydrogenation reaction with molecular oxygen in a high-temperature gas phase in the presence of an improved catalyst.

[0002]

2. Description of the Related Art A large number of methods for producing methacrylic acid by subjecting isobutyric acid to a catalytic oxidative dehydrogenation reaction with molecular oxygen in the presence of a catalyst in a high-temperature gas phase and a catalyst used for the production are known. I have.

For example, Japanese Patent Application Laid-Open No. 50-71618 discloses an Fe-P-Pb-O-based catalyst, and Japanese Patent Application Laid-Open No. 58-7253.
No. 7 discloses Fe-P-M-O (M = Co, La, T
e, Ag), USP. No. 4,314,075 discloses that
Mo-PM-Cu-V-X-M'-O (M = alkali metal, X = Ba, La, Ga, Al, Ag, Cd, T
i, Hg, Pb, Zn, M '= Fe, Co, Ni, S
r, Mn, In, Ta, Ge, S, Be) and the like are disclosed.

However, when producing methacrylic acid from isobutyric acid, it is relatively easy to increase the reaction rate of isobutyric acid, but it is difficult to maintain the selectivity of methacrylic acid together with the reaction rate at a high value. Yes, the yield of methacrylic acid is only about 50 to 70%.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have made intensive studies for the purpose of developing an industrial catalyst capable of producing methacrylic acid in high yield by catalytic oxidative dehydrogenation of isobutyric acid. Was done. As a result, it was found that by improving the iron phosphate-based catalyst, the selectivity as well as the reaction rate could be further increased, and methacrylic acid could be obtained in a high yield as high as 80% or more, leading to the present invention. .

[0006]

The present invention provides a method for producing methacrylic acid by subjecting isobutyric acid to a catalytic oxidative dehydrogenation reaction in the presence of a catalyst with molecular oxygen in a high-temperature gas phase. formula,

Embedded image

(Where Fe is iron, P is phosphorus, Co is cobalt, Pb is lead, and O is oxygen, and subscripts a, b,
c, d, and e indicate the number of atoms, and when a is fixed to 1, b is 0.7 to 5, preferably 0.8 to 4, and c is 0.
01 to 2, preferably 0.05 to 1, d is 0.01 to
3, preferably 0.05 to 2, and e is a value naturally determined by the valence of the element other than oxygen, and is usually 4 to 20.
Take the value of The present invention relates to a method for producing methacrylic acid, which comprises using the composition represented by the formula (1).

The catalyst used in the present invention is represented by the above general composition formula. When iron is fixed to one atom, phosphorus, cobalt, and lead may be out of the above range or lack any component. Then, the reaction rate of isobutyric acid is lowered, the selectivity of methacrylic acid is lowered, and the methacrylic acid yield is eventually lowered, which is not suitable.

In the present invention, when cerium (Ce) is contained in the catalyst, the yield of methacrylic acid is further improved. The amount of cerium is 0.01 per atom of iron.
3 to 3 atoms, preferably 0.05 to 2 atoms are suitable.

In the present invention, each element in the catalyst is mainly an oxide in which a plurality of elements such as iron phosphate, cobalt phosphate, lead phosphate, and cerium phosphate are bonded to oxygen, and a part of the element is used alone. It exists as an oxide of the element.

The catalyst used in the present invention is obtained by mixing a compound containing each component element constituting the catalyst, for example, a compound such as an oxide or a salt of each element in the presence of water, followed by drying and calcining. , Or coprecipitate from nitrate or ammonium salt, etc., and separate, dry,
It can be prepared by baking, or by separately preparing iron phosphate, cobalt phosphate, lead phosphate and the like in advance, mixing these in the presence of water, drying and baking.

Examples of oxides and salts of each element that can be used as starting materials for preparing the catalyst include ferrous nitrate, ferric nitrate, ferrous carbonate, ferric carbonate, ferrous chloride, and ferrous chloride. Iron compounds such as ferric, ferrous hydroxide, ferric hydroxide, ferrous oxide and ferric oxide, pyrophosphoric acid, metaphosphoric acid, orthophosphoric acid, ammonium phosphate, phosphorus trichloride, phosphorus tetrachloride ,
Phosphorus compounds such as phosphorus pentoxide, cobalt nitrate, cobalt oxide, cobalt carbonate, cobalt chloride, cobalt hydroxide,
Cobalt compounds such as cobaltous oxide, lead compounds such as lead nitrate, lead oxide, lead phosphate, lead hydroxide, lead chloride, and lead acetate; cerium compounds such as cerium nitrate and cerium chloride;

One example of a catalyst preparation method suitably used in the present invention will be described by taking a catalyst comprising iron, phosphorus, cobalt, lead and oxygen as an example. A predetermined amount of water-soluble iron,
Cobalt and a compound of lead, for example, nitrate, are dissolved in water, a predetermined amount of a water-soluble phosphate compound, for example, a solution of ammonium salt dissolved in water is added thereto, and a precipitate containing each catalyst component element is added. Generate. Next, this precipitate is separated as required, dried, molded, and calcined at 450 to 700 ° C. for 2 to 10 hours in an oxygen atmosphere to obtain a target catalyst.

In the present invention, the catalyst may be used alone or may be used by being supported on a carrier. Examples of the carrier include those conventionally known as carriers for oxidative dehydrogenation catalysts, such as silica, alumina, silica-alumina, zirconia, titanium oxide, carborundum, and diatomaceous earth. When the catalyst is supported on a carrier, the amount of the carrier is generally 3 g or less per 1 g of the catalyst.

In carrying out the oxidative dehydrogenation reaction of the present invention, a gas which is substantially inert to the reaction other than isobutyric acid and molecular oxygen can be used as a diluting gas. Examples of the dilution gas include water vapor, nitrogen gas, carbon dioxide gas, and the like. In particular, steam is
When this is present in the reaction system, the selectivity of methacrylic acid can be improved and the methacrylic acid yield can be increased, and further, there is an effect of maintaining the catalytic activity. Therefore, it is preferable that steam is present in the reaction system.

The amount of water vapor (H ₂ O) is preferably 5 to 100 mol, preferably 15 to 80 mol, and particularly preferably 18 to 70 mol, per 1 mol of isobutyric acid. Although the selectivity of methacrylic acid increases as the amount of water vapor with respect to isobutyric acid increases, an excessively large amount results in poor space-time yield of methacrylic acid, and the use of a large amount of water vapor is not economically preferable.

It is not necessary to use high-purity oxygen gas as the molecular oxygen, and an oxygen-containing gas, for example, a gas diluted with the diluent gas, air, or the like is generally used. The amount of molecular oxygen (O ₂ ) is 0.1 to 1 mol, preferably 0.5 to 0.9 mol, per 1 mol of isobutyric acid.

If the reaction temperature is too high, a decomposition reaction of the formed methacrylic acid occurs, so that it is appropriately selected from a temperature of generally 250 to 550 ° C, preferably 300 to 450 ° C. In addition, the contact time is generally 0.1.
1 to 7 seconds, preferably 0.2 to 5 seconds is suitable. The reaction pressure may be normal pressure, low pressure or reduced pressure, but it is generally appropriate to carry out the reaction under normal pressure. The reaction may be carried out in a fixed bed, a moving bed, a fluidized bed or the like, but it is generally appropriate to carry out the reaction in a fixed bed.

[0019]

According to the present invention, methacrylic acid can be produced at a high selectivity while maintaining the reaction rate of isobutyric acid at a high value, and the methacrylic acid can be produced at a high yield of 80% or more. Therefore, the industrial effect is extremely large.

[0020]

EXAMPLES In each example, the results were measured one hour after the start of the reaction. The conversion of isobutyric acid (%), the selectivity of methacrylic acid (%), and the yield of methacrylic acid (%)
Is defined as follows. In Table 1, IBA means isobutyric acid, and MAA means methacrylic acid.

Example 1 Ferric nitrate [Fe (NO ₃ ) ₃ .9H _{2 in} 1 liter of water
O] 202 g, cobalt nitrate [CO (NO ₃ ) ₂ .6H
₂ O] 29.1 g,及Hi lead nitrate [Pb _{(NO 3) 2]} 6
After dissolving 6.2 g, 188 g of ammonium phosphate [(NH ₄ ) ₃ PO ₄ .3H ₂ O] dissolved in 1 liter of water was added thereto to form a precipitate. The precipitate is filtered, washed, dried at 120 ° C., crushed and sized to 4 to 10 mesh size, and then calcined at 500 ° C. for 5 hours to obtain a catalyst composition (excluding oxygen). , Etc.) having the atomic ratios shown in Table 1. The catalyst 10 was packed in a stainless steel reaction tube having an inner diameter of 18 mmΦ, and isobutyric acid: H ₂ O:
A mixed gas having a molar ratio of N ₂ : O ₂ of 1: 15: 16.3: 0.7 was flowed at a flow rate of 10.31 ml / hour, at a reaction temperature of 400 ° C. and a contact time of 3 seconds under normal pressure. A catalytic oxidative dehydrogenation reaction of isobutyric acid was performed. Table 1 shows the results. Note that formation of acetone, carbon dioxide, and propylene was recognized as by-products.

Examples 2 to 7 Catalysts having the compositions shown in Table 1 were prepared in the same manner and in the same manner as in Example 1, and the reaction conditions were partially changed to those shown in Table 1. Similarly, catalytic oxidative dehydrogenation of isobutyric acid was performed. Cerium nitrate [Ce (NO ₃ ) ₃ .6H ₂ O] was used as a cerium source. Table 1 shows the results.

Comparative Examples 1-3 Catalysts having the compositions shown in Table 1 were prepared in the same manner and in the same manner as in Example 1, and the reaction conditions were partially changed to those shown in Table 1. Similarly, catalytic oxidative dehydrogenation of isobutyric acid was performed. Table 1 shows the results.

[0024]

[Table 1]

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C07C 51/377 C07C 57/05 CAPLUS (STN) REGISTRY (STN) WPIDS (STN)

Claims (1)

(57) [Claims] 1. A method for producing methacrylic acid by subjecting isobutyric acid to catalytic oxidative dehydrogenation reaction with molecular oxygen in the presence of a catalyst in a high-temperature gaseous phase, wherein the catalyst has the following general composition formula: (Where Fe is iron, P is phosphorus, Co is cobalt, Pb is lead, and O is oxygen, and the subscripts a, b, c, d, and e indicate the number of atoms, and when a is fixed to 1, , B is 0.7 ~
5, c is 0.01 to 2, d is 0.01 to 3, and e is a value naturally determined by the valence of the element other than oxygen,
Usually, it takes a value of 4 to 20. A method for producing methacrylic acid, comprising using the composition represented by the formula (1).