WO1999008998A1

WO1999008998A1 - Process for producing formamide

Info

Publication number: WO1999008998A1
Application number: PCT/JP1998/003656
Authority: WO
Inventors: Tadashi Irizawa; Kazumoto Ogura; Hidetake Togawa; Mikiyoshi Kawaragi; Akira Tsunemi
Original assignee: Mitsubishi Rayon Co., Ltd.
Priority date: 1997-08-18
Filing date: 1998-08-18
Publication date: 1999-02-25
Also published as: CN1125810C; CN1267280A

Abstract

A process for producing formamide through the reaction of methyl formate with ammonia, which comprises (1) reacting methyl formate with ammonia in a reactor in the presence of formamide in an ammonia to methyl formate molar ratio higher than 1, (2) feeding the reaction mixture to a separation column for low-boiling substances to distill off a low-boiling fraction through the column top, (3) taking out the residual liquid from the column bottom and feeding it to a product distillation column, (4) taking out formamide from the top of the product distillation column, and (5) discharging the high-boiling liquid fraction from the column bottom and circulating and feeding the fraction to the reactor or the separation column for low-boiling substances.

Description

Description Manufacturing method of formamide 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 pharmaceuticals, and the like.

Background art

Several proposals have been made on a method for producing formamide from methyl formate and ammonia. For example, JP-B-38-28757 describes that adding a catalytic amount of water to methyl formate and introducing ammonia increases the reaction rate. JP-A-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 ammonium are by-produced.

The following is a method for continuously producing formamide from methyl formate and ammonia.

JP-A-5-2-14-21010 cools a part of the liquid withdrawn from the reactor and reacts it with methyl formate and gaseous ammonia sprayed from a nozzle. Is supplied to a reactor again to react methyl formate with ammonia gas at a low temperature to produce formamide. JP-A-57-1506448 describes a method for 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 generated formamide.

JP-A-6-340600 describes a method for producing formamide in the presence of at least 20% by weight of alcohol with respect to methyl formate. Methods such as the addition of alcohols are not efficient because they are reaction by-products that should be removed from the product. The present invention has been made in view of the above-mentioned problems of the prior art, and has an object to formally produce formamide by reacting methyl formate with ammonia. 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 distillation and purification of a target product.

Disclosure of the invention

The present inventors have conducted intensive studies on the above problems, and as a result, in a method for producing formamide from methyl formate and ammonia, by performing a continuous reaction in the presence of formamide and free ammonia, The by-product of diformamide is suppressed, and the liquid extracted from the bottom of the product distillation column is circulated and supplied to the reaction tank or low-boiling separation column to recover formamide in the bottom liquid, and The present inventors have found that the yield of the desired formamide is improved by changing the diformamide therein to formamide, and completed the present invention.

That is, the present invention relates to a method for producing formamide by reacting methyl formate and ammonia, comprising the following steps: 1) Methyl formate and ammonia in a reaction vessel in the presence of formamide in a molar ratio of ammonia / methyl formate> 1. 2) Supply the reaction solution to the low-boiling separation column and remove the low-boiling components by distillation from the top of the column.3) Take out the low-boiling separated solution from the bottom of the column and supply it to the product distillation column.4) The gist of the present invention is a method for producing formamide, which involves removing formamide from the top of a product distillation column and 5) circulating and supplying the high-boiling liquid separated from the bottom of the column to a reaction tank or low-boiling separation column.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view showing one embodiment of the production process of the present invention.

BEST MODE FOR CARRYING OUT THE 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 reaction vessel A in advance. A very small amount is sufficient, but it is preferably about 100 to 10% of the capacity of the reaction tank from the viewpoint of operability. 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 simultaneously supplied to reaction vessel A at a high power, and the ratio is preferably such that ammonia is excess with respect to methyl formate. Methyl formate> 1, preferably 0.1 to 5, more preferably 1.01 to 20.

The reaction temperature ranges from 10 to 60 ° C, preferably from 30 to 50 ° C.

The reaction solution ③ thus obtained is withdrawn from the reaction vessel A, fed to the middle stage of the low-boiling separation column B1, and distilled under normal pressure and a bottom temperature of 60 to 120 ° C. The low-boiling fraction mainly composed of methanol is removed from the top of the system by distillation, and incinerated or sent to a methanol recovery system. A liquid mainly composed of formamide (low-boiling liquid 1) ⑤ is taken out from the bottom of the column and supplied to the middle stage of the next product distillation column C.

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 this low-boiling separation column B2, preferably, the pressure is 133 to 26,66 Pa (l to 200 To rr), the top temperature is 5 to 40 ° C, and the bottom temperature is 90 to (1) Distill at 30 ° C, remove low-boiling fraction mainly composed of methanol from the top of the column by distillation, and send to incineration or methanol recovery system. A liquid containing formamide as the 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 preferably 13 to 6,665 Pa (0.1 to 50 To rr), the top temperature is 90 to 110 ° C, and the bottom temperature is 100. Distillation is performed under conditions of ~ 140 ° C to obtain the product formamide II 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 extracted from the bottom of the product distillation column C is divided into a high boiling separated liquid of 1/20 to 19Z20 amount and the remaining bottom liquid, and the former high boiling separated liquid is used as a reaction tank. Recirculate to A. Alternatively, this high-boiling liquid ⑩ is supplied to the low-boiling separation tower B1 together with the reaction product ③ containing about 0.1 to 2% of free ammonia. 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 distillation column B1. . After adding ammonia to the high-boiling 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 amount of ammonia added is 1 mole or more, preferably 2 to 30 moles, per mole of diformamide.

The addition of ammonia may be performed in the following steps. The liquid removed from the bottom of the low-boiling separation tower B 1 (low-boiling separation liquid 1) ⑤ or the liquid removed from the bottom of the low-boiling separation tower B 2 (low-boiling separation liquid 2) 、 Is added in an equimolar amount or more, preferably 2 to 30 times by mol, relative to diformamide, and the resulting mixture is supplied to the next step.

As described above, by simultaneously feeding methyl formate and ammonia under a condition where the ammonia is excessive and continuously reacting, by adding ammonia and distilling, and circulating and supplying the bottom liquid of the product distillation tower. Formamide having a low impurity content such as diformamide can be obtained in high yield.

Hereinafter, the present invention will be more specifically described with reference to Examples. It goes without saying that the present invention is not limited to only these Examples.

Example 1

Formamide was manufactured by the manufacturing process shown in FIG.

200 kg of formamide was charged into reaction vessel A, and methyl formate①120 kg ZH and ammonia gas②35 kg / H were simultaneously supplied with ammonia Z methyl formate = 1.03 mol 1 mol, and the temperature was increased. A continuous reaction was carried out at 40 to 45 ° C and normal pressure. After about 2 hours, when the reaction became stable, the reaction product solution withdrawn from the reaction tank (3) (155 kg / H) was composed of 57.4% formamide, 40.9% methanol, and 0.9% ammonia. , 0.8% of methyl formate, and below the lower limit of detection of diformamide (about 10 ppm), and the reaction conversion was 99.0% (vs. methyl formate).

This reaction product ③ and the bottom liquid 抜き 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 volume of the high boiling separation liquid ⑩ 3 1 kg / H and supply it to the middle stage of the low boiling separation column B 1 at 186 kg / H, normal pressure, top temperature 56 ° C, maintain a steady state at the bottom temperature of 110 ° C, remove low-boiling components mainly composed of methanol from the top of the column by distillation, and remove low-boiling separated liquid mainly composed of formamide from the bottom of the column. 1 3 2 kg / H was taken out. 1⑤ of this low-boiling liquid was supplied to the middle stage of low-boiling separation column B2 at 13 kg kgH, at a pressure of 10, 664 Pa (80 To rr) and a top temperature of 13. C, Distill at a bottom temperature of 110 ° C, remove low-boiling fraction mainly composed of methanol from the top of the column by distillation, and remove 2 mL of low-boiling separated liquid mainly composed of formamide from the bottom of the column. Removed at 15 kg / H. Further, 2⑦ of this low-boiling liquid was supplied to the middle stage of the product distillation column C at 115 kgZH, the pressure was 1,333 Pa (10 To rr), the top temperature was 110 ° C, and the bottom was Distillation at a temperature of 120 gave the product formamide at the top of the column at 84 kg ZH.

The yield of product formamide was 93%, its composition was 99.9% formamide, 0.05% methanol, and methyl formate, formic acid, and diformamide were below the lower detection limit (about 10 pm).

Example 2

2.8 kg / H was blown with ammonia into the high-boiling liquid 3/4 of the bottom liquid (containing 4.3% diformamide) extracted from the bottom of the product distillation column C. And the reaction solution ③ were mixed and supplied to the middle stage of the low-boiling separation column B1, and the same operation as in Example 1 was performed to obtain a product formamide.

The product formamide yield was 93%, its composition was 99.9% formamide, 0.05% methanol, and methyl formate, formic acid, and diformamide were below the detection limit (about 10 PPm). .

Example 3

Example 1 was repeated except that 0.37 kg_ / H of ammonia was blown into the liquid (low-boiling liquid 1) から (containing 0.3% diformamide) taken out from the bottom of low-boiling separation tower B1. By performing the same operation, a product formamide was obtained.

The product formamide yield is 93%, its composition is 99.9% formamide, 0.05% methanol, and methyl formate, formic acid and diformamide are below the detection limit (about 10 ppm). there were.

Comparative Example 1

Methyl formate 1 20.6 kg / H and ammonia gas 33.4 kg / H were supplied continuously with the same conditions as in Example 1 except that ammonium formate = 0.97 mol Z 1 mol was supplied. Was. About 30 hours after the start of the reaction, the reaction product ③ was withdrawn from the reaction tank A and analyzed. As a result, formamide 56.1%, methanol 40.0%, ammonia 0.3%, methyl formate 3.2% And diformamide was 2,500 ppm.

Comparative Example 2

A continuous reaction was carried out under the same conditions as in Example 1 except that the high-boiling liquid 分離 was not circulated.

The yield of product formamide was 88%.

Comparative Example 3

Continuous reaction was carried out under the same conditions as in Example 1 except that 200 kg of methanol was charged into reaction vessel A. Approximately 2 hours later, the reaction product ③ extracted from reaction vessel A was analyzed. As a result, 37.3% of formamide, 61.2% of methanol, 0.09% of ammonia, and 1.3% of methyl formate were reacted. The conversion was 97.5% (vs. methyl formate). Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be used for the production of industrially useful formaldehyde as a solvent, a raw material for organic synthesis, a raw material for pharmaceuticals and the like.

Claims

The scope of the claims

1. In the method of producing formamide by reacting methyl formate and ammonia, 1) reacting methyl formate and ammonia in a reaction tank in the presence of formamide in a molar ratio of <1> methyl ammonium formate> 1. 2) Supply the reaction solution to a low-boiling separation column, distill off low-boiling components from the top of the column, and 3) take out the low-boiling liquid from the bottom and supply it to a product distillation column.4) Product distillation A method for producing formamide, comprising removing formamide from the top of the column, and 5) circulating and supplying the high-boiling separated liquid removed from the bottom of the column to a reaction vessel or a low-boiling separation column.

2. The method according to claim 1, further comprising adding ammonia to the high-boiling liquid.

3. The method according to claim 1 or 2, further comprising adding water to the low-boiling liquid.