JPS60239435A - Production of trifluoroacetic acid - Google Patents

Abstract

PURPOSE:The oxidation of 1,1-dichloro-2,2,2-trifluoroethane with O2 is effected in the presence of a small amount of water and the product is hydrolyzed with a large amount of water to collect the titled compound formed in individual process simultaneously. CONSTITUTION:In the production of trifluoroacetic acid from 1,1-dichloro-2,2,2- trifluoroethane, oxygen and water, the reaction between CF3CHCl2 and O2 is carried out in the presence of a small amount of water, preferably 0.01-0.5mol per mol of CF3CHCl2 to form a reaction mixture containing CF3COCl as a major product and CF3COOH as a by-product, then the resultant the reaction mixture is subjected to hydrolysis with a large amount of water to convert CF3COCl into CF3COOH, which is collected together with the above-stated by- product whereby trifluoroacetic acid is obtained. EFFECT:The combination of these two reactions increases the yield of the product.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing trifluoroacetic acid, and more specifically, the present invention relates to a method for producing trifluoroacetic acid. 0F that can be manufactured smoothly and advantageously
Concerning a new manufacturing method for 3000FI.

Trifluoroacetic acid (cFxcooa) is used as a raw material for producing agricultural medicines, as a reaction solvent, or as an esterification catalyst.
It is a compound useful as various catalysts such as condensation catalysts. Conventionally, OFI C0OH has been produced by electrolytic fluorination of acetic acid fluoride (U.S. Pat. No. 4,022,824).
However, this method has drawbacks such as the high cost of separating the intermediate product and l1m. Therefore, 0FsOO13,0FJ
CHO1*.

O as a raw material such as 0FsOHx01 in the presence of mercury salt.
FN) Reaction between Olg and sulfur trioxide (Patent application published in 1972)
6-501649), a method in which QFsOHC12 containing less than 0.1% by weight of water is reacted with oxygen in the presence of active radiation such as ultraviolet rays (Japanese Patent Publication No. 5B-24416)
(U.S. Pat. No. 3,883,407) and a method of irradiating a mixture of 0F30H201, chlorine and oxygen with ultraviolet light under substantially anhydrous conditions (U.S. Pat. No. 3,15105).
A method for producing trifluoroacetic acid chloride (circscoal) has been proposed. This 0F100OI becomes CFmoo due to hydrolysis reaction.
Although it is converted to OH, the above-mentioned Japanese Patent Publication No. 5B-2441
In Publication No. 6 and the like, in order to prevent excessive hydrolysis, a material that is substantially anhydrous, that is, a raw material containing less than 0.1 weight of water is used. Further, the above-mentioned US Pat. No. 3,151,051 discloses that QFaOOOH is obtained when the above mixture is irradiated with ultraviolet rays in the presence of water.

The applicant believes that the conventional manufacturing method using mercury salts is industrially disadvantageous because the chemicals used are difficult to handle, and that the method using active radiation such as ultraviolet rays causes the source glass to devitrify due to trace amounts of hydrofluoric acid produced as a by-product. Conventional methods have various drawbacks, such as not being able to be used for a long period of time, so we have previously proposed a method that overcomes these drawbacks. That is, JP-A-58-159
0F80HO1! disclosed in Publication No. 440! was thermally oxidized in the presence of a small amount of water to form 0FIOooH and QFaC.
This is a method of co-manufacturing with OOl. In this method, if water is not present, the oxidation reaction progresses extremely slowly, and ayscooa and QysOOOO
Based on the knowledge that the selectivity to l becomes low, it is said that it is preferable to carry out the reaction in the presence of water, usually selected from the range of 0.01 to 1 mol per 1 mol of 0FaOHO'l. .

The present inventor has developed 0FIC! which uses 0FIHC12, C++ and H2O as raw materials! As a result of various studies and examinations regarding the manufacturing method of OOH, we have come to the following interesting findings. First, as pointed out in JP-A-58-159440, the reaction between 0FsOHO:Lx and 02 proceeds extremely slowly in the absence of water;
The presence of water is preferred in order to increase the conversion of OFIHOlg and advantageously maintain the selectivity of the target product. However, in this oxidation reaction, when the amount of water added is increased to increase the generation ratio of OFmOOOH, not only does the corrosion tendency of the equipment materials due to by-product HOI and HF increase, but also the reaction tank wall corrodes. As a result, metal chloride is generated, and this chloride acts as a negative catalyst and stops the oxidation reaction, reducing the reaction rate and furthermore, unreacted 0FiOH.
O1 undergoes an oxidation reaction all at once, and there is even a danger of explosion. Therefore, increasing the amount of water added alone is not sufficient to achieve high yields.
It is not possible to obtain FsooOH. On the other hand, in the presence of a large amount of water, C! FI 0HOI mushroom oxidation reaction and 0FaO
Although it is conceivable to carry out the hydrolysis reaction of OO1 at the same time, it is practically impossible due to the above-mentioned corrosion problem. Therefore, the process of carrying out the oxidation reaction of 0FIOHOIJ in the presence of a small amount of water and the CF containing the generated CFlooOH, 0
Hydrolyze 001 and convert 0F100OI to 0F8000H
It has been found that by carrying out the conversion steps separately and combining them, it is possible to carry out the process industrially smoothly and advantageously, and to obtain 0FSOOOH in a good yield.

The present invention was completed based on the above knowledge, and when producing 0FII 0OOH using 0FIOHOI, Ox and HzO as raw materials, CFIHOli and CFIHOli are added in the first stage by adding a small portion of the raw material Ego. O! ays coal as the main product
A reaction product mixture containing OFI COOH as an accompanying product was obtained, and after the reaction product mixture from the previous stage was reacted with a large portion of the raw material H20 without subjecting it to a separation operation, Cym(1001 was converted into OFmOOOH
and then convert the former accompanying product OFJ 0OO
The present invention relates to a method for producing trifluoroacetic acid, which is characterized in that H and the subsequent product ays cooH are taken out together.

The reaction of 0F30HO1x, Qx and H2O in the first stage can be expressed as follows.

207sCI(C1z +Ox +H!O→0FsOO
The OH+0FsOOffl+3HO1 reaction can be carried out in a gas phase at a reaction temperature of 250 to 400°C, preferably 260 to 320°C, usually under a pressure of 25 to as Kg/cd. If the temperature is lower than this, the reaction rate may decrease or the reaction may not occur, and if the temperature is higher than this, side reactions such as thermal decomposition reactions are likely to occur, which is not preferable. Water, which is liquid at room temperature, easily liquefies in the reaction tank, and adding more water than necessary, which would remain unreacted, must be avoided due to corrosion problems. In the above reaction, water acts as a catalyst and hydrolyzes a part of 0F30001 produced by oxidation of 0F80HO1 to 0F100O.
It is thought that it has the effect of converting into H. Therefore, it is preferable that the amount of water added is the minimum required as a catalyst, and at a level that does not liquefy and adhere to the walls of the reaction tank. Usually 0FllOHO121moA
It is preferable to select from the range of o, oi to 0.5 mol per /, and 0.1 mol or more is preferable in order to increase the selectivity of 0FBOOOH in the first stage.

Raw material 0F30HC! 12. If 02 and I(to) are incompletely mixed, unreacted 0FsOHC1 will accumulate and a large amount of oxidation reaction will occur at once, creating a risk of explosion. Therefore, it is recommended to use a stirrer, etc. to thoroughly mix the mixture. (!FI
IQ) (In order to prevent C12 from unreacting and accumulating, the reaction molar ratio of 2 to OFgOHO] and z should be
It is preferable to set it to 1 ilt or more, and from the viewpoint of explosion limit, it is preferable to set it to about 2 times the mole or less. Therefore, the reaction molar ratio of C2 is selected from the range of 0.5 to 2-11=#, preferably 1 to 2 moles per mole of ayrsaHclt.

CF3000H and C! obtained in the previous stage. FJOO
C! The reaction product mixture of No. 1 is used as the raw material H! without being subjected to any separation operation. 0FICOO by reacting with a large amount of 00
0F3000H can be obtained smoothly and advantageously by converting I into 0F100H and taking out this □FsooOH together with OF 3000H obtained in the previous step.

That is, without separating the main product QlraOOCl obtained together with (HrsOOOH) in the first stage, all of it can be converted to CF3000H in the second stage, so the main product is not wasted and Qys (
300H can be obtained.

The reaction between H10 and the reaction product mixture from the first stage in the second stage is preferably a hydrolysis operation consisting of two steps A and B described below. In other words, in the human process, ○ including Hl0
F3C! By contacting OOH with the reaction product mixture from the previous stage, 0F3C containing substantially no H10! OOH was obtained, and in step B, 0FI100 was separated without undergoing hydrolysis in a manual process.
OFI0O containing H10 by reacting OI with excess H1
This is a method in which OH is obtained and used in step A. In the human process, so to speak, 0FI100OH is determined by C7aOOOO1.
In step B, excess HffiO is used to dehydrate c
The aim is to convert all ysaoal into 0F100OH, which is essentially anhydrous CFlooO from a human process.
H can be taken out.

0F100 to 0F100OH including old 0 in human process
The method of bringing the OI into contact is not limited in any way, but operation at room temperature and normal pressure is preferred; a method in which gaseous 0F100OI is blown into the 01rsOOOH liquid containing Hgo under stirring, or a method in which the two are brought into continuous contact in a packed column; Alternatively, a method in which these methods are used in combination and operated continuously and cyclically can be adopted.

The less water content in the c'FsooOH solution,
Since the hydrolysis reaction between OFI OOO'l and ltQ is slow, it is preferable to increase the chances of contact between aysaoal and water by continuous cyclic operation.

In process B, OF is separated without undergoing hydrolysis in the human process.
To convert all I Cool to 0F100OH 1
An excessive amount of H! React with O. 0FllOOO'
The method for bringing 1 into contact with HCH is similar to the method described above for bringing 01000H containing Fr2O into contact with OF8 Cool. HIO is converted to 0F100OH by reaction with Q7*QOO1, and finally a small amount of H
It becomes 0F100OH containing xO, undergoes dehydration in a manual process, and is extracted as anhydrous 0F3000H.

OF before being dehydrated in the human process! The amount of water in 0OOH may be about 1 to 10% by weight. If the water content is too small, there is a high possibility that 0F30001 will be discharged without being hydrolyzed in step B, which is not preferable. Furthermore, if the water content is too large, the dehydration time in the manual process becomes longer, which is not preferable. Due to dehydration in the human process, the water content is approximately 0.01
Up to % by weight of substantially anhydrous OF2 COOH can be obtained. CFm C! Since OOH and Hto have an azeotropic composition and are difficult to separate by distillation, such a dehydration step is extremely effective.

Examples of the present invention will be described in more detail below.

Example 1 C! F30H0111103mol/i
, Hto 10.3 mo1/4 and 02103 mo
The first stage reaction of the present invention was carried out by continuously supplying 1/&. The reaction temperature was 300° C., the pressure was 30 Ky/evls, and the residence time was 8.4 minutes. The obtained reaction product was heated to 19F
- Analysis by NMR and gas chromatography revealed that O
The reaction rate of F+lHO]-z was 95%, the selectivity of cFsooOH was 26%, and the selectivity of 0FII Cool was 68%.

Subsequently, the obtained reaction product was hydrolyzed in two steps A and B. In the human process, in 97 mol of 0FaOOOH1 containing 5% by weight of Hto, 0F3000
H25,4mol/& and 0FaC! 00166.5
Mo1/min was continuously supplied and dehydrated, 24
After a period of time, the moisture content became less than 0.01% by weight.

On the other hand, in step B, 1596 mol of HzO is hydrolyzed in a continuous cycle by OFI Cool supplied from step A, and after 24 hours, C containing 5% by weight of Hto is
! The amount of FsOOOH was 1197 mol.

Note that the amount of 0F80001 that is not hydrolyzed in Step A and is supplied to Step B is that the water content in OF3000H in Step A is approximately 1% by weight, and the water content is 0.0%.
The amount increased rapidly as it approached 1% by weight.

Example 2 The same reaction and analysis as in Example 1 were carried out, except that the amount of Hto supplied was 20.6 mo1/circle, the reaction temperature was 260° C., and the residence time was 7.2 minutes. As a result, cFs
The reaction rate of aHc1 was 91%, the selectivity of 0FsOOOH was 28%, and the selectivity of 0F110001 was 65%. Subsequently, the obtained reaction product was hydrolyzed in two steps A and B. In human process “N%” (7) a
0FsO in 858 mol of CFsooOH containing 2o
00H26,2mol/-An, and 0F300016
0.9 m01/-A of water was supplied in a continuous circulation manner to perform dehydration, and after 24 hours, the moisture content became 0.01% by weight or less. On the other hand, in Step B, 1462 mol of HzO was subjected to hydrolysis in a continuous circulation with cFqoocl supplied from Step A, and after 24 hours, it became 858 mol of 0F3000H containing 10 weight -〇H20.

Note that, as in Example 1, the amount of chi<:to○1 that is not hydrolyzed in the human process and is supplied to the B process is determined by the amount of OF! in the human process. There was almost no water content in 000H up to about 1% by weight, and it rapidly increased as the water content approached 0.01% by weight.

Claims (1)

[Claims] (1) In producing OFI000H using 0FsOHO1, Os and HIO as raw materials, in the first stage, 0FsOHO1 and 02 are added by adding a small portion of the raw materials HIO.
is reacted to obtain a reaction product mixture containing QFiOOOl as a main product and 0F100OH as an accompanying product, and in the latter stage, the reaction product mixture from the previous stage is not subjected to a separation operation, and the raw material H! 0 to convert 0F3COO1 to 0FJOOOH, and then convert the front co-product 0FaOOOH and the post-product C! A method for producing trifluoroacetic acid, which is characterized by removing FS 0OOH at the same time. (In the first stage, the amount of HIO added is 0F30HO1
Selected from the range of 0.01 to 0.5 mol per mol *
Scope of Pestle H Seigyu @ 2. The method for producing trifluoroacetic acid described in item 2. (8) The method for producing trifluoroacetic acid according to claim 1, wherein the reaction molar ratio of 0F30HO1z and 02 in the first stage is selected from the range of 1=1 to 1:2. (1) The method for producing trifluoroacetic acid according to claim 1, wherein the reaction temperature in the first stage is selected from the range of 260 to 320°C. (6) The reaction pressure in the first stage is 25 to 35 Kf/cd.
The method for producing trifluoroacetic acid according to claim 1, which is selected from the range of: