JPH0236584B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently hydrolyzing trifluoroacetic acid chloride to obtain substantially anhydrous trifluoroacetic acid in good yield. Trifluoroacetic acid chloride (hereinafter abbreviated as TFAC) is used as a raw material for the production of agricultural medicines, and trifluoroacetic acid (hereinafter abbreviated as TFA) is used as a raw material for the production of agricultural medicines, as well as as a reaction solvent, as an esterification catalyst,
It is a compound useful as various catalysts such as condensation catalysts. Japanese Patent Publication No. 58-24416 and Japanese Patent Publication No. 58-159440
The publication discloses that TFA and TFAC are co-produced through the oxidation reaction of 1,1-dichloro-2,2,2-trifluoroethane (hereinafter abbreviated as R-123). Furthermore, Patent Application Publication No. 56-501649 discloses a method for producing TFAC by reacting 1,1,1-trifluoro-2,2,2-trichloroethane with sulfur trioxide in the presence of a mercury salt. . On the other hand, it is known that TFAC is easily hydrolyzed to become TFA. Therefore, if you want to obtain only TFA in a good yield, all you need to do is to supply water in the reaction mixture containing TFAC in an amount greater than the amount required for hydrolysis of TFAC, and convert all of the TFAC to TFA. become. However, TFA and water have an azeotropic composition, making distillation separation difficult.
The above-mentioned operation in which water from the final reaction remains after hydrolysis is not preferred. Recognizing these problems, the present inventors have conducted intensive research into methods for efficiently converting TFAC to TFA, and as a result, have obtained the following interesting findings () and (). did it. () Although it is difficult to remove water from TFA containing water by distillation separation, it is difficult to remove water from TFA containing water.
Substantially water-free TFA can be obtained by contacting TFAC and consuming water as hydrolysis of TFAC. TFAC undergoes hydrolysis
It changes to TFA, and excess TFAC can be easily separated from TFA based on the difference in boiling point. () Because TFA containing water can be easily converted into TFA that does not substantially contain water in () above,
React TFAC with excess water to remove all TFAC
Operation to convert to TFA, i.e. containing water
TFA-generated operations are not penalized. The present invention was completed based on these findings, and includes the use of TFAC to remove water from TFA, and the use of TFA containing water.
The basic configuration is to use what is obtained by converting all TFAC to TFA. The method of bringing TFAC into contact with TFA containing water is not limited at all, but operation at room temperature and normal pressure is preferred;
It is possible to adopt a method in which gaseous TFAC is injected into a TFA liquid containing water while stirring, a method in which the two are brought into continuous contact in a packed tower, or a method in which these methods are combined and operated in a continuous circulation manner. .
The lower the amount of water in the TFA solution, the more
Since the hydrolysis reaction between TFAC and water is slow, it is preferable to increase the chances of contact between TFAC and water by continuous cyclic operation. Figure 1 shows that TFAC is completely absorbed by excess water.
TFA including the process of converting to TFA and the resulting water
A flow sheet consisting of the process of removing and dehydrating the water inside with TFAC is shown. The feed from FIG. 1 10 may be a reaction mixture containing TFAC,
TFAC can be used alone, and ultimately all TFAC
It is converted to TFA and discharged from 28. A reaction mixture obtained by reacting R-123, oxygen, and water will be explained as an example of a reaction mixture containing TFAC. The composition of this reaction mixture is mainly TFA,
TFAC, hydrochloric acid and unreacted oxygen. All operations according to the flow sheet shown in FIG. 1 may be performed at room temperature and normal pressure, and the hydrochloric acid and oxygen supplied from 10 are in a gaseous state through the first acetic acid tower 11, the first separation tank 12, the conduit 16, and the first It passes through the cooling tower 13, the conduit 19, the second acetation tower 21, the second separation tank 22, the conduit 26, and the second cooling tower 23, and is discharged to the abatement system 29, and the target TFA
It is separated from Components that are gaseous at room temperature and pressure in the reaction mixture containing TFAC obtained by a method other than the oxidation reaction of R-123 will be similarly discharged via the above-mentioned route. The rate of hydrolysis of TFAC is faster than the rate at which these gases react with water, and there is no risk that these gases to be removed will remain after being liquefied or hydrolyzed. TFAC to be hydrolyzed also passes through the same route as the hydrochloric acid and the like in a gaseous state, but by the time it passes through the second cooling tower 23, it has been completely hydrolyzed and converted into a TFA liquid. Water for hydrolysis is continuously supplied through the conduit 30 in an excess amount to the TFAC accompanying the hydrochloric acid, and is hydrolyzed in the second separation tank 22 and converted into a TFA liquid. This converted TFA liquid and excess unreacted water are circulated via conduits 24 and 25. The one passing through the conduit 24 is the second cooling tower 2
3, and in the second separation tank 22, a trace amount of TFAC that is not hydrolyzed and may be entrained in hydrochloric acid etc. is removed.
After conversion to TFA by water in TFA solution, conduit 2
7 and is returned to the second separation tank 22. Since TFA is a liquid at room temperature and normal pressure, there is a small possibility that it will accompany hydrochloric acid etc. and rise up the conduit 26, but if it does, it will liquefy when passing through the second cooling tower 23 and pass through the second conduit 27. TFA is returned to the separation tank 22.
There is no loss such as discharge into the abatement system. conduit 2
5 is introduced into the second acetation tower 21,
TFAC is hydrolyzed and returned to the second separation tank. By continuously performing such a circulation operation, 1 to 10% by weight is contained in the second separation tank 22.
TFA solution containing water accumulates. The flow connecting the second acetation tower 21, the second separation tank 22, and the second cooling tower 23, which occupy the right half of FIG. 1, has been described above, and these will be collectively referred to as the B process. Contains a small amount of water filled in the second separation tank 22
The TFA liquid is intermittently transferred to the first separation tank 12. The TFA liquid containing a trace amount of water in the first separation tank 12 is circulated through conduits 14 and 15. conduit 1
4 is introduced into the first cooling tower 13, and the TFAC that does not undergo hydrolysis in the first acetation tower 11 or the first separation tank 12 and accompanies hydrochloric acid etc. is treated with water in the TFA liquid.
After being converted to TFA, it is returned to the first separation tank 12 via a conduit 17. The TFAC in the reaction mixture 10 is introduced through the conduit 15 into the first acetation column 11.
is hydrolyzed and returned to the first separation tank 12. The first cooling tower also has the role of liquefying TFA and returning it to the first separation tank 12, similar to the second cooling tower during the B process. By continuously performing such a circulation operation, the amount of water in the first separation tank 12 is approximately
TFA liquid with a concentration of around 0.01% by weight accumulates.
As mentioned above, the first acetation tower 11 occupies the left half of Figure 1,
Although the flow connecting the first separation tank 12 and the first cooling tower 13 has been described, the entire flow will be referred to as the A process. TFAC that has not undergone hydrolysis is transferred via conduit 19 to second acetation tower 21 in the step B, and finally all of it is converted into TFA by excess water entering from conduit 30. Not only such TFAC but also TFAC or the reaction mixture supplied from FIG. 10 may be introduced into the second acetation column.
The TFA liquid containing about 1 to 10% by weight of water accumulated in the second separation tank 22 is transferred to the first separation tank 12 with a water content of about 0.01% by weight through a distillation process through a conduit 28. It is preferable to fill it into the first separation tank 12 after extracting it from the tank. Contains about 1-10% water by weight
The amount of TFA liquid filled into the first separation tank 12 is
The amount may be determined depending on the amount of TFA accumulated by hydrolysis of TFAC or TFA as a reaction product (hereinafter referred to as newly accumulated amount of TFA). That is, when the water content of the TFA liquid in the first separation tank 12 changes from, for example, 5% by weight to 0.01% by weight, the amount of TFA newly accumulated in the first separation tank 12 increases.
The amount of filling is such that 2 is filled. of course,
It is not necessary to operate until the first separation tank is 100% full of the liquid, and it is preferable to perform an operation that allows the liquid to be discharged to the distillation system after the first separation tank is about 80% full. The reaction mixture containing TFAC or TFAC is continuously introduced into the first acetation column. When the amount of water in the TFA liquid is large, it is thought that hydrolysis of TFAC occurs mainly in the first acetation tower. Hydrolysis of TFAC is thought to occur in the first separation tank as the amount of water becomes very small. When the temperature of the reaction mixture containing TFAC supplied from No. 10 or TFAC is high, it is meaningful to pass the TFA liquid to the first acetation tower to play a role of cooling as well as hydrolysis. That is, there is a possibility that the TFA in the first separation tank will be vaporized by the supplied TFAC or its mixture and will be discharged from the A process. The amount of water supplied from conduit 30 is the amount necessary to ensure that all of the TFAC sent from step A is converted to TFA. The water supply position does not have to be between the second acetation tower and the second separation tank as shown in FIG. 1, but may be from the upper part of the second acetation tower. In any case, with a minimum water supply
An operation that converts all TFAC to TFA is preferred.
TFA necessary to prevent TFAC from escaping into the abatement system
The water content in the liquid is 1 to 10% by weight or more. TFAC flowing from the acetation tower to the separation tank is introduced deeply into the TFA liquid so that it comes into good contact with the water in the TFA liquid.
It is recommended to perform operations such as stirring the liquid. It is preferable to use a packed tower as the acetic acid tower or cooling tower so that sufficient gas-liquid contact can be carried out. Examples of the present invention will be described in more detail below. Example TFAC was hydrolyzed according to the flow sheet shown in the attached FIG. 1 under the operating conditions shown in Table 1 below.
The 1620 moles of TFA containing 5% by weight water supplied into the first separation tank 12 was dehydrated and the water content became 100 ppm or less after 24 hours. On the other hand, the second separation tank 2
2,160 moles of water supplied in 2 was subjected to hydrolysis by TFAC supplied from FIG. There is TFA in the gas discharged from Figure 1 29.
and TFAC were not included.

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a flow sheet showing one aspect of the TFAC hydrolysis process. 11...first acetation tower, 12...first separation tank,
13...first cooling tower, 30...water supply conduit.

Claims (1)

[Scope of Claims] 1. In producing trifluoroacetic acid substantially free of water by hydrolyzing trifluoroacetic acid chloride, hydrolysis is carried out in two steps A and B,
In step B, trifluoroacetic acid chloride is brought into contact with trifluoroacetic acid containing water to obtain trifluoroacetic acid that is substantially free of water, and in step B, trifluoroacetic acid chloride is reacted with excess water to obtain trifluoroacetic acid containing water. A method for producing trifluoroacetic acid, which comprises obtaining acetic acid and using it in step A. 2 In step A, trifluoroacetic acid chloride and the following trifluoroacetic acid solution (a) are brought into contact to perform hydrolysis, and trifluoroacetic acid chloride is separated and sent to step B, and the water in the solution (a) is After being consumed by hydrolysis, the substantially water-free trifluoroacetic acid solution (b) is extracted, and in step B, the trifluoroacetic acid chloride sent from step A and an excess amount of water relative to the chloride are removed. Claim 1, characterized in that a trifluoroacetic acid solution (a) containing water is produced by the reaction, and the solution (a) is sent to step A after the solution (b) is extracted. The method for producing trifluoroacetic acid described in Section 1. 3. The method for producing trifluoroacetic acid according to claim 2, wherein the water content in the trifluoroacetic acid solution (a) containing water is 1 to 10% by weight.