JPH0558924A - Method for purifying 2,2-dichloro-1,1,1-trifluoroethane - Google Patents

Abstract

PURPOSE:To simplify a production process of 2,2-dichloro-1,1,1-trifluoroethane, especially a purifying process for reducing 1,2dichloro-1,1,2-trifluoroethane carried by 2,2-dichloro-1,1,1-trifluoroethane. CONSTITUTION:In a method of purification for reducing 1,2-dichloro-1,1,2- trifluoroethane contained in 2,2-dichloro-1,1,1-trifluoroethane by isomerizing 1,2-dichloro-1,1,2-trifluoroethane in a vapor phase, fluorinated and chlorinated alumina obtained by fluorinating and chlorinating active alumina with 1,2- dichloro-1,1,2-trifluoroethane in a vapor phase is used as the catalyst.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is useful as a refrigerant, a foaming agent for urethane foam, a cleaning agent for removing oils and fluxes, a solvent for dry cleaning, etc.
-A method of purifying dichloro-1,1,1-trifluoroethane.

[0002]

2. Description of the Related Art 2,2-Dichloro-1,1,1-trifluoroethane (hereinafter referred to as HCF)
Abbreviated as C-123. Conventionally, various methods have been proposed for the manufacturing method (1). For example, USP-4,76
According to the description in the specification of US Pat. No. 6,260, fluorination of tetrachloroethylene with hydrogen fluoride in the presence of an alumina catalyst supporting chromium, cobalt, nickel, manganese, etc. in a gas phase results in a high yield of H 2
I have obtained CFC-123. However, HCFC-123 synthesized by such a method contains 5 to 15% of 1,2-dichloro-1,1,2-trifluoroethane (hereinafter abbreviated as HCFC-123a) which is an isomer. It is known that Usually, such products are generally separated and purified by a distillation operation. The boiling points of these substances are 27.1 ° C. for HCFC-123 and HCF.
C-123a is extremely close to 28.2 ° C. and there is a problem that it cannot be easily separated.

Although the toxicity and toxicity of HCFC-123a are not clear, it is a product, HCFC-123.
Considering that it is intended to be used for a wide range of general purposes, it is not preferable to incorporate impurities that are doubtful in terms of safety, and it is extremely important to reduce its content as much as possible. It can be said to be important.

In order to separate such a mixture of liquid isomers, in addition to distillation, a method utilizing the adsorption property of a solid substance or a dissolution property in a liquid substance, and the difference in chemical properties are used to separate only one of them. In many cases, a method in which a reaction is performed and then a separation operation is performed is adopted. There are various improvements in these methods depending on the target substance, but the most desirable form is to convert the isomer to be removed to the target isomer by an isomerization reaction. There is no end.

For example, it is known that a catalyst obtained by partially fluorinating alumina has an excellent effect on isomerization of perchlorofluorohydrocarbon. However, when such a means is applied to a substance such as HCFC-123 or HCFC-123a having a hydrogen atom in its molecule, the life of the catalyst is short and it is difficult to put it into practical use.
Therefore, some proposals have been made for the purpose of solving this problem. For example, Japanese Patent Publication No. 61-2737
According to the gas phase isomerization method described in No. 5, perchlorofluorohydrocarbon is added to HCFC-123 containing HCFC-123a by using alumina fluorinated and chlorinated in advance in the gas phase with perchlorofluorohydrocarbon as a catalyst. It is proposed that the reaction be carried out in the state of coexisting with each other to extend the catalyst life. Further, according to the description in JP-A-2-108639, a similar effect is obtained by allowing a hydrogen-containing halogenated hydrocarbon to coexist by the same method and catalyst.

However, although the above-mentioned isomerization method has succeeded in achieving the intended longevity of the catalyst, perchlorfluorocarbonization which should not be mixed into the product by such a method. Hydrogen or hydrogen-containing halogenated hydrocarbons and their decomposition products are entrained in the isomerization reaction product, which complicates the subsequent production process more than necessary, which is a very disadvantageous process. I have no choice. Furthermore, in these methods, perchlorofluorohydrocarbon is used as a reactant for fluorinated chlorination of the catalyst, but perchlorofluorohydrocarbon is a substance regulated worldwide as a causative agent of ozone layer depletion. Yes, it is an obligation for science and technology to avoid the use of these substances.

[0007]

SUMMARY OF THE INVENTION In view of the problems of the prior art, the inventors of the present invention have taken into consideration the manufacturing process of HCFC-123, particularly HCFC-
The present invention has been achieved through intensive studies for the purpose of simplifying the refining process for reducing 123a.
That is, the present invention provides H contained in HCFC-123 by isomerizing HCFC-123a in the gas phase.
In a purification method for reducing CFC-123a, activated alumina is used as a catalyst in a gas phase of HCFC-123.
It relates to a purification method characterized by using fluorinated chlorinated alumina fluorinated and chlorinated by a.

More specifically, substantially HCFC-12
3 and HCFC-123a, HCFC-123
a / HCFC-123 + HCFC-123a is not more than 0.2, the crude HCFC-123 is isomerized in the presence of a catalyst in the gas phase at an elevated temperature to isomerize the crude HCFC-123 to reduce HCFC-123a, thereby reducing HCFC-123a. , A fluorinated chlorinated alumina obtained by fluorinating activated alumina at a temperature elevated in a gas phase with a gas containing HCFC-123a is used. In the method of the present invention, it is possible to maintain a sufficiently long catalyst life without intentionally adding any component to the crude HCFC-123 during the isomerization reaction.

The isomerization process of the present invention comprises HCFC-12
Although it is not necessary to insert it at a specific position in the manufacturing process of No. 3, it is substantially purified by distilling and purifying HCFC-123 and HC.
It is preferable to operate on a product free of components other than FC-123a, or a product obtained by removing the acid gas from the reaction product gas.

The composition of the reaction product referred to here is HCFC
Naturally, it will vary significantly depending on the catalyst, raw material, and reaction conditions in the method for synthesizing -123, but in general, 2-chloro-1,1,1,2-terachloroethane (hereinafter referred to as HCFC
Abbreviated as -124. ) 0-40% by weight, HCFC-123
40-99 wt%, HCFC-123a 0-20 wt%, 1,2,2-trichloro-1,1-difluoroethane (hereinafter abbreviated as HCFC-122) 0-50 wt%
Is.

Crude HCFC-1 which can be purified in the present invention
The composition of 23 is not particularly limited, but HCFC-1
23 and HCFC-123a in total is preferably 50% by weight or more, and HCFC-123a / HCFC-
123 + HCFC-123a is preferably 0.2 or less.

The reaction temperature of the isomerization reaction of the present invention is 250 to
Perform at 350 ° C. At 250 ° C or lower, sufficient isomerization activity cannot be obtained, and at 350 ° C or higher, a decomposition reaction of HCFC-123 occurs, which causes problems such as a decrease in HCFC-123 yield and inclusion of by-products in the purification system. Will result.
The pressure of the reactor can be selected so as to satisfy the temperature and pressure conditions at which the crude HCFC-123 can maintain a gaseous state, but is selected from a gauge pressure of 0 to 1 kg / cm ² .

The contact time required to complete the isomerization reaction depends on the reaction temperature, reaction pressure, etc., but is usually 2 to
180 seconds are preferable and 5 to 60 seconds are more preferable. The HCFC-123a used for the preparation of the catalyst may be a pure substance, but it is not always necessary and a substance diluted with other components to an arbitrary concentration can be used, and for example, HCFC-123a in distillation purification can be used. Although low-boiling components containing the same can be used, in practice, it is most rational to use an object to be treated in the isomerization reaction from the viewpoint of simplification of the apparatus.

The temperature for fluorinating and chlorinating activated alumina is preferably 200 to 400 ° C, more preferably 250 to 380 ° C. At 200 ° C or lower, fluorinated chlorination does not sufficiently occur and a satisfactory isomerization activity cannot be obtained. On the other hand, fluorinated chlorination at 400 ° C or higher does not eliminate this, but is particularly effective. No results are obtained.

The apparatus used for preparing the catalyst and the apparatus for the isomerization reaction may be prepared separately, but it is generally preferable to use the same apparatus from the viewpoint of the construction and operation of the apparatus.
The reaction is carried out in a fluidized bed or a fixed bed, and the material of the reaction tube is Monel, Inconel, iron, stainless steel or the like.

[0016]

The present invention will be described below with reference to examples.
The embodiment is not limited to these. Adjustment Example 1 Molded spherical activated alumina (KHA3-, manufactured by Sumitomo Chemical Co., Ltd.)
24, diameter 3 mm) inner diameter 22 mm filled with 60 cc,
A 300 mm long SUS316 reaction tube was placed in an electric furnace and the maximum temperature part of alumina was kept at 350 ° C.
HCFC-123 containing 10% of CFC-123a was flowed, and fluorinated and chlorinated in a gas phase to prepare a catalyst. The end point of the fluorinated chlorination of alumina was the time when the hot spot resulting from this treatment reached the end of the reaction tube on the gas outflow side. Adjustment Example 2 A catalyst was adjusted in the same manner as in Adjustment Example 1 except that the highest temperature part of alumina was kept at 250 ° C. Adjustment Example 3 Instead of HCFC-123 containing 10% HCFC-123a, HCFC-124 7.6 wt%, HCFC-
123 60.8% by weight, HCFC-123a 9.1% by weight, HCFC-122 15.6% by weight, others
A catalyst was prepared in the same manner as in Preparation Example 1 except that the reaction product of 6.9% by weight was used. Adjustment Example 4 A catalyst was adjusted in the same manner as in Adjustment Example 1 except that dichlorodifluoroethane was used instead of HCFC-123 containing 10% of HCFC-123a. Example 1 HCFC-123a gasified after completion of catalyst preparation according to Preparation Example 1 and lowering the temperature of the reaction tube to 300 ° C.
Crude HCFC-123 containing 10% was supplied at 80 cc / min for reaction. The reaction product was collected in a trap cooled to -50 ° C. One hour after the start of the reaction, the collected matter was analyzed by gas chromatography. As a result, it was confirmed that HCFC-123a was isomerized into HCFC-123. After continuing the reaction for a further 100 hours, the same analysis was carried out, and as a result, it was confirmed that the isomerization activity was maintained. Example 2 The same reaction as in Example 1 was carried out except that the temperature of the reaction tube was lowered to 250 ° C. After 1 hour from the start of the reaction, the collected matter was analyzed by gas chromatography to find that HCFC-123a
The isomerization rate was 55%. Example 3 The same reaction as in Example 1 was carried out except that the catalyst of Preparation Example 2 was used instead of the catalyst of Preparation Example 1 and the temperature of the reaction tube was 250 ° C. When the collected matter was analyzed by gas chromatography one hour after the start of the reaction, the isomerization ratio of HCFC-123a was 13%. Example 4 After the preparation of the catalyst was completed according to Preparation Example 3 and the temperature of the reaction tube was lowered to 300 ° C., the same reaction product as that used in Preparation Example 3 which had been gasified was supplied at 80 cc / min for reaction. Let The reaction product was collected in a trap cooled to -50 ° C. When the collected material was analyzed by gas chromatography, it was confirmed that all HCFC-123a was isomerized to HCFC-123. After continuing the reaction for a further 100 hours, the same analysis was carried out, and as a result, it was confirmed that the isomerization activity was maintained. Comparative Example A reaction product was analyzed in the same manner as in Example 1 except that the catalyst of Preparation Example 4 was used instead of the catalyst of Preparation Example 1. As a result, after 20 hours, HCFC-123
It was confirmed that the entire amount of a was isomerized to HCFC-123, but it was confirmed that the isomerization rate decreased to 90% after 30 hours.

[0017]

According to the method of the present invention, HCFC-12
In the isomerization reaction of 3a, it is possible to maintain the high activity of the catalyst for a long time without requiring any additional component, and moreover, as a fluorinated chlorinating agent used for activating the catalyst, it is substantially the same as the object to be treated. Because the same substance can be selected,
Adjustment of the catalyst can be achieved only by adjusting the operating conditions in the reactor, and it is not necessary to install special equipment,
The manufacturing apparatus of the HCFC-123 can be greatly simplified, and at the same time, the manufacturing operation can be prevented from becoming complicated.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // C07B 61/00 300

Claims (1)

[Claims] 1. By isomerizing 1,2-dichloro-1,1,2-trifluoroethane in the gas phase,
In a purification method for reducing 1,2-dichloro-1,1,2-trifluoroethane contained in 2-dichloro-1,1,1-trifluoroethane, activated alumina is used as a catalyst in the gas phase in the gas phase of 1,2-dichloro-1,1,2-trifluoroethane. -Dichloro-1,1,2-
A purification method characterized by using fluorinated chlorinated alumina fluorinated and chlorinated with trifluoroethane.