JPH11124359A - Method for producing formamide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining formamide by reacting methyl formate with ammonia, thereby efficiently reducing the amount of impurities such as diformamide generated during the reaction and distillation and purification of a target product, and efficiently producing formamide. Providing a way to do it. SOLUTION: 1) Methyl formate 1 and ammonia 2 are reacted in a reaction vessel A in the presence of formamide at a molar ratio of ammonia / methyl formate>1;
To remove the low-boiling fraction 4 from the top of the column by distillation, and 3) take out the low-boiling separated liquid 7 from the bottom of the column and supply it to the product distillation column C. 4) Formamide 8 from the top of the product distillation column C 5) The high boiling separated liquid 10 taken out from the bottom of the column is circulated and supplied to the reaction vessel A or the low boiling separation tower B1 to produce formamide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing formamide by reacting methyl formate with ammonia. Formamide is an industrially useful substance as a solvent, a raw material for organic synthesis, a raw material for medicine, and the like.

[0002]

2. Description of the Related Art Several methods have been proposed for producing formamide from methyl formate and ammonia. For example, Japanese Patent Publication No. 38-2857 discloses that the reaction rate increases when a catalytic amount of water is added to methyl formate and ammonia is introduced. Japanese Patent Application Laid-Open No. 3-68544 describes a method for producing formamide from methyl formate and ammonia using a basic catalyst. However, the method using water or a basic catalyst as a catalyst has a problem in that formamide produced is hydrolyzed and formic acid and ammonia are by-produced.

[0003] As a method for continuously producing formamide from methyl formate and ammonia, there is the following method. In Japanese Patent Application Laid-Open No. 52-142010, a part of a liquid extracted from a reactor is cooled, and methyl formate is added thereto.
By reacting with gaseous ammonia sprayed from the nozzle,
A method is described in which both are supplied to a reactor again to react methyl formate and ammonia gas at a low temperature to produce formamide. JP-A-57-150648 describes a method of continuously producing formamide from methyl formate and ammonia while recovering methanol as a reaction by-product. These documents do not describe the reduction of diformamide by-produced in the formed formamide.

Japanese Patent Application Laid-Open No. Hei 6-340601 describes a method for producing formamide in the presence of at least 20% by weight of an alcohol with respect to methyl formate. Therefore, such a method of adding an alcohol is not efficient.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and has as its object to industrially produce formamide by reacting methyl formate with ammonia. In doing so, it is an object of the present invention to provide a method capable of efficiently producing formamide by reducing impurities such as diformamide, formic acid, and ammonia generated during the reaction and distillation and purification of a target product.

[0006]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have conducted a continuous reaction in the presence of formamide and free ammonia in a method for producing formamide from methyl formate and ammonia. By this, by-products of diformamide during the reaction are suppressed, and the liquid extracted from the bottom of the product distillation column is circulated and supplied to the reaction tank or the low-boiling separation column to recover formamide in the bottom liquid. And that diformamide in the bottom liquid was changed to formamide to improve the yield of the desired formamide, and completed the present invention.

That is, the present invention relates to a method for producing formamide by reacting methyl formate with ammonia, comprising the steps of: 1) reacting methyl formate with ammonia in a reaction vessel in the presence of formamide in a molar ratio of ammonia / methyl formate>1; 2) The reaction solution is supplied to a low-boiling separation column to remove low-boiling components from the top by distillation, and 3) the low-boiling liquid is taken out from the bottom and supplied to a product distillation column. The gist of the present invention is a method for producing formamide, wherein formamide is taken out from the top of a product distillation column, and 5) the high-boiling separated liquid taken out from the bottom is circulated and supplied to a reaction tank or a low-boiling separation column.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a view showing one embodiment of the manufacturing process of the present invention.

In the method of the present invention, the reaction between methyl formate and ammonia is carried out in the presence of formamide.
Therefore, before starting the reaction by supplying methyl formate and ammonia, it is necessary to charge formamide into the reaction vessel A in advance. A very small amount is sufficient, but from the viewpoint of operability, the volume of the reactor is preferably 100 to 10%.
% Is preferable. The concentration of formamide during the reaction is 30 to 99%, preferably 50 to 70%, as the concentration in the reaction solution.

It is desired that the raw materials methyl formate and ammonia used in the method of the present invention have as high a purity as possible, but they may be industrial ones.

In FIG. 1, methyl formate (1) and ammonia (2) are supplied to a reaction vessel A at the same time. / Methyl formate> 1, preferably 1.01 to 1.5, more preferably 1.01 to 1.2
It is in the range of 0. The reaction temperature ranges from 10 to 60C, preferably from 30 to 50C.

The reaction solution (3) thus obtained is withdrawn from the reaction tank A and supplied to the middle stage of the low-boiling separation column B1.
Distillation is carried out at normal pressure and at a bottom temperature of 60 to 120 ° C. The low-boiling fraction (4) containing methanol as a main component is removed from the column by distillation outside the system and incinerated or sent to a methanol recovery system. A liquid containing formamide as a main component (low-boiling liquid 1) (5) was taken out from the bottom of the column, and the next product distillation column C
To the middle stage.

At this time, a low-boiling separation column B2 may be further added between the low-boiling separation column B1 and the product distillation column C. In the low-boiling separation column B2, preferably, the pressure is from 133 to 2
6,660 Pa, tower top temperature 5-40 ° C, tower bottom temperature 90-
The mixture is distilled under a condition of 130 ° C., and a low-boiling fraction (6) containing methanol as a main component is removed from the top of the system by distillation and sent to an incineration or methanol recovery system. A liquid containing formamide as a main component (low-boiling liquid 2) (7) is taken out from the bottom of the column and supplied to the middle stage of the product distillation column C. In the product distillation column C, the pressure is 13 to 6,665 Pa, and the top temperature is 90 to 1,
Distillation is performed under the conditions of 10 ° C. and a bottom temperature of 100 to 140 ° C. to obtain a product formamide (8) from the top of the column.

In the method of the present invention, the following operation is performed for the purpose of reducing diformamide and improving the yield of formamide. The bottom liquid (9) withdrawn from the bottom of the product distillation column C is divided into a 1/20 to 19/20 volume high-boiling liquid (10) and the remaining bottom liquid (11). The separation liquid (10) is circulated and supplied to the reaction tank A. Alternatively, the high-boiling liquid (10) is treated with 0.1 to 2 free ammonia.
% Together with the reaction product liquid (3). At this time, an intermediate tank may be provided between the reaction tank A and the low-boiling distillation column B1, and the reaction product liquid (3) and the high-boiling separation liquid (10) may be mixed and then supplied to the low-boiling separation tower B1. Good. After adding ammonia to the high-boiling separation liquid (10), the reaction product liquid (3) may be mixed, and the mixture may be supplied to the low-boiling separation tower B1. At this time, the addition amount of ammonia is equal to or more than 1 mole, preferably 2 to 30 moles relative to diformamide.

The addition of ammonia may be performed in the following steps. Ammonia is added to the liquid (low-boiling liquid 1) (5) taken out from the bottom of the low-boiling separation tower B1 or the liquid (low-boiling liquid 2) (7) taken out of the bottom of the low-boiling separation tower B2. The mixture is added in an equimolar amount or more, preferably 2 to 30 times by mol, based on diformamide, and the resulting mixture is supplied to the next step.

[0016]

As described above, methyl formate and ammonia are simultaneously fed and continuously reacted under an excessive amount of ammonia, and distillation is performed by adding ammonia.
By circulating and supplying the bottom liquid of the product distillation column, formamide having a low impurity content such as diformamide can be obtained in high yield.

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to only these Examples.

Example 1 Formamide was produced by the production process shown in FIG. 200 kg of formamide is charged into reaction vessel A, and methyl formate (1) 120 kg / H and ammonia gas (2) 3
5 kg / H and ammonia / methyl formate = 1.03 mol / 1 mol were simultaneously supplied, and a continuous reaction was carried out at a temperature of 40 to 45 ° C. and normal pressure. When the reaction was stabilized after about 2 hours, the reaction product (3) withdrawn from the reaction tank was 155 kg /
The composition of H was 57.4% formamide and 40.000 methanol.
9%, 0.9% ammonia, 0.8% methyl formate, and below the lower detection limit of diformamide (about 10 ppm);
The reaction conversion was 99.0% (vs. methyl formate). This reaction product liquid (3) and a bottom liquid extracted from the bottom of the product distillation column C (formamide 94%, water 0.01%, ammonia formate 0.15%, and diformamide 4.3%)
3/4 of the high-boiling liquid (10) 31 kg / H of (9) was mixed and supplied to the middle stage of the low-boiling separation tower B1 at 186 kg / H, normal pressure, top temperature 56 ° C, bottom Maintaining a steady state at a temperature of 110 ° C., the low-boiling component (4) mainly composed of methanol was removed from the top of the column by distillation, and the low-boiling separated liquid 1 (5) mainly composed of formamide 132 kg / H was collected from the bottom of the column. Was taken out. This low-boiling liquid 1 (5) is supplied to the middle stage of the low-boiling separation tower B2 at 132 kg / H, and the pressure is 10,664P.
a, Distillation is performed at a top temperature of 13 ° C. and a bottom temperature of 110 ° C., a low-boiling component (6) containing methanol as a main component is removed from the top of the column by distillation, and a low-boiling separation containing formamide as a main component from the bottom of the column. Liquid 2 (7) was taken out at 115 kg / H. Further, the low boiling separated liquid 2 (7) is added to the middle stage of the product distillation column C by 1
The mixture was fed at 15 kg / H and distilled at a pressure of 1,333 Pa, a top temperature of 110 ° C., and a bottom temperature of 120 ° C., to obtain 84 kg / H of a formamide product from the top of the column. The product formamide yield is 93%, and the composition is formamide 99.9.
%, Methanol 0.005%, methyl formate, formic acid and diformamide were below the lower detection limit (about 10 ppm).

Example 2 Ammonia was added to 3/4 of the high boiling separated liquid (10) of the bottom liquid (containing 4.3% diformamide) (9) extracted from the bottom of the product distillation column C. .8kg / H blow,
Except that this solution and the reaction solution (3) were mixed and supplied to the middle stage of the low-boiling separation column B1, the same operation as in Example 1 was performed to obtain a product formamide. The product formamide yield is 93
%, Formamide 99.9%, methanol 0.005%, methyl formate, formic acid and diformamide were below the lower detection limit (about 10 ppm).

Example 3 A liquid (low-boiling liquid 1) (5) (containing 0.3% diformamide) taken out from the bottom of the low-boiling separation tower B1 was blown with 0.37 kg / H of ammonia. The same operation as in Example 1 was performed to obtain a product formamide. The yield of product formamide is 93%, its composition is formamide 9
9.9%, methanol 0.005%, methyl formate, formic acid and diformamide were below the lower detection limit (about 10 ppm).

Comparative Example 1 Example 1 was repeated except that methyl formate (1) 120.6 kg / H and ammonia gas (2) 33.4 kg / H were supplied at a ratio of ammonia / methyl formate = 0.97 mol / 1 mol. A continuous reaction was performed under the same conditions as described above. About 30 hours after the start of the reaction, the reaction product liquid (3) withdrawn from the reaction vessel A was analyzed. As a result, 56.1% of formamide, 40.0% of methanol,
The content was 0.3% of ammonia, 3.2% of methyl formate, and 2,500 ppm of diformamide.

Comparative Example 2 A continuous reaction was carried out under the same conditions as in Example 1 except that the high-boiling liquid (10) was not circulated. The yield of product formamide was 88%.

Comparative Example 3 A continuous reaction was carried out under the same conditions as in Example 1 except that 200 kg of methanol was charged into the reactor A. About 2 hours later, the reaction product liquid (3) withdrawn from the reaction vessel A was analyzed. As a result, formamide 37.3%, methanol 61.2%,
The reaction conversion was 97.5% (vs. methyl formate) with 0.09% ammonia and 1.3% methyl formate.

[0024]

[Brief description of the drawings]

FIG. 1 shows an embodiment of a manufacturing process for performing the present invention.

[Explanation of symbols]

 1; methyl formate 2; ammonia 3; reaction liquid 5; low-boiling liquid 17; low-boiling liquid 28; product formamide 9; bottom liquid 10; high-boiling liquid A; reaction vessel B1; B2: Low boiling separation column C: Product distillation column

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mikiyoshi Kawaraki 10-1 Ogurocho, Tsurumi-ku, Yokohama Nitto Chemical Industry Co., Ltd. Chemical Industry Co., Ltd.

Claims (3)

[Claims] 1. A method for producing formamide by reacting methyl formate with ammonia, comprising: 1) reacting methyl formate with ammonia in a reaction vessel in the presence of formamide in a molar ratio of ammonia / methyl formate>1; The reaction solution was supplied to a low-boiling separation column to remove low-boiling components from the top by distillation,
3) Take out the low boiling separated liquid from the bottom of the column and supply it to the product distillation column, 4) Take out formamide from the top of the product distillation column,
5) A method for producing formamide, which comprises circulating and supplying a high-boiling separated liquid taken out from the bottom of the column to a reaction tank or a low-boiling separating tower. 2. The method according to claim 1, further comprising adding ammonia to the high-boiling liquid. 3. The method according to claim 1, wherein ammonia is further added to the low-boiling liquid.