JP2023021492A - Method for producing 1-chloro-2,2-difluoroethylene - Google Patents

Abstract

To provide a method for producing 1-chloro-2,2-difluoroethylene from 1,2-dichloro-1,1-difluoroethane as a raw material, which can be performed more industrially, under relatively low temperature conditions, and show very little reduction in reaction conversion even during long-time production.SOLUTION: A method for producing 1-chloro-2,2-difluoroethylene includes subjecting 1,2-dichloro-1,1-difluoroethane to a vapor phase reaction in the presence of a solid catalyst. The solid catalyst is formed by bringing a basic substance into contact with activated carbon and then heating the activated carbon under nitrogen atmosphere.SELECTED DRAWING: None

Description

The present invention relates to a method for producing 1-chloro-2,2-difluoroethylene using 1,2-dichloro-1,1-difluoroethane as a raw material. 1-Chloro-2,2-difluoroethylene is a useful compound as an intermediate in the production of electronic materials and medicines and agricultural chemicals.

Conventionally, as a method for producing 1-chloro-2,2-difluoroethylene using 1,2-dichloro-1,1-difluoroethane as a raw material, a stoichiometric amount or more of sodium hydroxide is used in a liquid phase. A method of reacting 1,2-dichloro-1,1-difluoroethane (see, for example, Patent Documents 1 and 2), using a reaction tube made of nickel, 1,2-dichloro-1,1 at 500 ° C. to 600 ° C. - A method of circulating difluoroethane as a gas (see, for example, Patent Document 3) and a method of producing by thermal decomposition at 800° C. to 1,000° C. are known (see, for example, Patent Document 4).

The conventional method described in Patent Document 1 or 2 has a problem that a large amount of waste liquid is generated due to the reaction with sodium hydroxide in the liquid phase. On the other hand, the methods described in Patent Literatures 3 and 4 have the problem that reactions at high temperatures of 600° C. or higher are required.

On the other hand, Patent Document 5 proposes a method of reacting 1,2-dichloro-1,1-difluoroethane in a gas phase under relatively low temperature conditions of 250° C. to 550° C. using a solid catalyst. . However, in this method as well, it is desired to further extend the life of the catalyst (decrease in reaction conversion rate) when the reaction is carried out for a long time under relatively low temperature conditions. There has been a demand for an industrially practicable method in which the reaction is stable even after production.
Specifically, in Example 1 of paragraphs 0037 to 0039 of Patent Document 5, an example of producing 1-chloro-2,2-difluoroethylene using activated carbon under conditions of 0.0% by volume of oxygen in the raw material is described. there is In addition, in Example 2 of paragraphs 0049 to 0050, 1-chloro-2,2-difluoroethylene is produced using activated carbon supporting 5.0% by weight of cesium chloride under conditions of 0.0% by volume of oxygen in the raw material. Examples are given. In both Examples 1 and 2, the reaction temperature was 350° C., and although the conversion and selectivity remained unchanged from the start of the reaction until 60 minutes after the reaction was continued, the reaction was continued thereafter. It is unknown if it can be maintained if In addition, although the reaction is carried out at 350 ° C. in order to make it efficient, it is possible to maintain the catalytic action for a longer time as a practical production method on an industrial scale while reducing the equipment cost and suppressing energy consumption. It is desirable that the temperature be as low as possible for the reaction, and a catalyst that has sufficient reactivity (conversion rate) even at lower temperatures has been desired.

DE 28 46 812 A1. U.S. Pat. No. 2,709,181. U.S. Pat. No. 2,628,989. British Patent Application No. 774125. Japanese Patent Laid-Open No. 2020-125271.

In view of these prior arts, it is an object of the present invention to produce 1-chloro-2,2-difluoroethylene by a gas phase reaction using 1,2-dichloro-1,1-difluoroethane as a raw material. To provide a practical production method capable of producing 1-chloro-2,2-difluoroethylene at a sufficient rate under conditions and maintaining reaction efficiency even when the production is carried out for a long time. That's what it is.

Therefore, the present inventors have extensively studied a method for producing 1-chloro-2,2-difluoroethylene by reacting 1,2-dichloro-1,1-difluoroethane in the presence of a solid catalyst in the gas phase. After contacting with a basic substance, the activated carbon is reacted using a solid catalyst heat-treated in a nitrogen atmosphere at a relatively low temperature to produce 1-chloro-2,2-difluoroethylene. The present invention finds a more industrially practicable method for producing 1-chloro-2,2-difluoroethylene, which is possible to produce and exhibits extremely little decrease in reaction conversion even when the production is carried out for a long time. was completed. That is, the present invention relates to the following gists.

(1) 1,2-dichloro-1,1-difluoroethane is reacted in the gas phase in the presence of a solid catalyst obtained by contacting activated carbon with a basic substance and then heat-treating the activated carbon in a nitrogen atmosphere. A method for producing 1-chloro-2,2-difluoroethylene.

(2) The method for producing 1-chloro-2,2-difluoroethylene according to (1) above, wherein the basic substance is an organic amine or ammonia.
(3) The method for producing 1-chloro-2,2-difluoroethylene according to (1) above, wherein the basic substance is melamine.

(4) The method for producing 1-chloro-2,2-difluoroethylene according to any one of (1) to (3) above, wherein the reaction temperature is 250°C to 550°C.

According to the method of the present invention, 1-chloro-2,2-difluoro, which can be reacted under relatively low temperature conditions and has extremely little decrease in reaction conversion rate and selectivity even when the production is continued for a long time. A more industrially feasible production method for ethylene can be provided.

FIG. 1 is a diagram showing the results of the conversion rate and selectivity of the reaction in Comparative Examples 1 and 2 and Examples 1-1 to 1-3. The Y-axis (vertical axis) indicates conversion or selectivity numerical values (in units of %).

The present invention will be described in detail below. The present invention is not limited to the following embodiments, and can be modified in various ways as long as it does not exceed the gist of the invention.

The raw material 1,2-dichloro-1,1-difluoroethane used in the present invention is easily prepared by the reaction of 1,1,2-trichloroethylene and hydrogen fluoride.

<Activated carbon>
Types of activated carbon applicable to the present invention include activated carbon prepared from charcoal, coal, coconut shells, and the like.

The specific surface area of the activated carbon is not particularly limited, and is generally preferably 10 m ² /g to 4000 m ² /g, more preferably 50 m ² /g to 3000 m ² /g, further preferably 100 m ² /g to 2000 m ² /g. preferable. If the specific surface area of the activated carbon is less than 10 m ² /g, sufficient reaction conversion and selectivity may not be obtained. Conversely, even if it exceeds 4000 m ² /g, it is difficult to obtain a sufficient increase in reaction conversion rate and selectivity according to the specific surface area, and side reactions may easily occur. The specific surface area of activated carbon is measured by a method conforming to the BET method.

The activated carbon may be subjected to a high temperature treatment, if necessary. The high-temperature treatment method is not particularly limited, but includes heat treatment at 400° C. to 1000° C. for 1 hour to 3 hours in an inert gas.
Argon, helium, nitrogen, etc. are mentioned as an inert gas.

The solid catalyst used in the present invention can be obtained by a step of contacting the activated carbon with a basic substance and then heat-treating in a nitrogen atmosphere.

Specific examples of basic substances include thermally decomposable amine salts such as ammonium carbonate and ammonium hydrogen carbonate, and methylamine, ethylamine, propylamine, dimethylamine, diethylamine, dipropylamine, trimethylamine, triethylamine, melamine, and the like. Examples include organic amines and basic substances such as ammonia. These basic substances may be used alone or in combination of two or more such as melamine and ammonia.

The basic substance may be brought into contact using a solution dissolved in a solvent. Examples of the solvent to be used include water and alcohols such as methanol and ethanol. These solvents may be used alone or in combination of two or more.

The amount of the basic substance used is preferably 0.01 to 100 mass ratios, more preferably 0.1 to 50 mass ratios, and even more preferably 1 to 30 mass ratios relative to activated carbon. If the amount of the basic substance used is less than 0.01 mass ratio with respect to the activated carbon, sufficient reaction efficiency may not be obtained. It is difficult to obtain, and side reactions may occur easily.

The heat treatment method is not particularly limited, but for example, the activated carbon contacted with the basic substance is adjusted to a temperature in the range of 300° C. to 1200° C. in a nitrogen atmosphere, and heat treated for a treatment time of 1 minute to 5 hours. be done.

The solid catalyst used in the present invention is usually used in the form of powder or compacts of 1 mm to 30 mm, depending on the size of the reactor.

The reaction method of the present invention usually uses a reaction tube made of quartz, Pyrex (registered trademark) glass, iron, or nickel, fills the reaction tube with a solid catalyst, heats it to a predetermined temperature, and then 1,2-dichloro-1,1-difluoroethane diluted with argon is fed in gaseous state to carry out the reaction.

The concentration of diluted 1,2-dichloro-1,1-difluoroethane applicable to the present invention ranges from 5.0% by volume to 50.0% by volume.

The reaction temperature in the present invention is preferably 250° C. to 550° C., depending on the type of solid catalyst. If the reaction temperature is lower than 250°C, a sufficient reaction conversion rate may not be obtained. Even if the reaction temperature exceeds 550° C., it is difficult to obtain an increase in reaction conversion rate and selectivity, and side reactions may easily occur. In order to obtain a high selectivity, the reaction temperature is more preferably 250°C to 400°C, more preferably 250°C to 350°C.

In the present invention, the reaction time (contact time with the catalyst) is shortened when the reaction temperature is high and lengthened when the reaction temperature is low in order to control the conversion rate of the raw material and the selectivity of the product. 0.05 seconds to 20 seconds is preferred, 0.1 seconds to 10 seconds is more preferred, and 0.2 seconds to 5 seconds is even more preferred. If the reaction time is shorter than 0.05 seconds, sufficient reaction conversion and selectivity may not be obtained. A reaction may occur easily.

The post-treatment after the reaction of the present invention is not particularly limited, but in general, the product is cooled and liquefied, and then purified by distillation under normal or pressurized conditions to obtain purified 1-chloro- 2,2-difluoroethylene is obtained.

EXAMPLES The present invention will be further described below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[Catalyst Preparation Example 1]
The activated carbon was treated at 300° C. for 1 hour in a nitrogen atmosphere. After adding 0.0798 g of melamine (C ₃ H ₆ N ₆ ) and 30 mL of ethanol to 1 g of the obtained activated carbon and stirring for 1 hour, the mixture was dried under reduced pressure at 35 kPa and 65°C. This operation was performed once. Thereafter, heat treatment was performed at 700° C. for 5 hours in a nitrogen atmosphere to obtain melamine-supported activated carbon (catalyst 1-1).
After adding melamine and ethanol to the above activated carbon and stirring, the operation of drying under reduced pressure was repeated twice. Thereafter, heat treatment was performed at 700° C. for 5 hours in a nitrogen atmosphere to obtain melamine-supported activated carbon (catalyst 1-2).
After adding melamine and ethanol to the above activated carbon and stirring, the operation of drying under reduced pressure was repeated three times. Thereafter, heat treatment was performed at 700° C. for 5 hours in a nitrogen atmosphere to obtain melamine-supported activated carbon (catalyst 1-3).
Reactions for producing 1-chloro-2,2-difluoroethylene were carried out using the above catalysts 1-1, 1-2 and 1-3 (Examples 1-1 to 3-3). .

[Catalyst Preparation Example 2]
Activated carbon was treated at 300° C. for 1 hour in a nitrogen atmosphere (catalyst 2).
Catalyst 2 was directly subjected to a reaction for producing 1-chloro-2,2-difluoroethylene as shown below (Comparative Example 1).

[Examples 1-1 to 1-3] As solid catalysts, catalyst 1-1 (Example 1-1), catalyst 1-2 (Example 1-2) or catalyst 1-3 (Example 1-3 ) to produce 1-chloro-2,2-difluoroethylene at a reaction temperature of 300°C. After drying at 300° C. for 1 hour under nitrogen flow at 12 mL/min, the temperature of the catalyst layer was maintained at 300° C. and 1,2-dichloro-1 was added with nitrogen. ,1-difluoroethane concentration of 13.7% by volume was supplied to the reaction tube at a rate of 13.9 mL/min to carry out the reaction.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane and the selection of the target 1-chloro-2,2-difluoroethylene The rates were 30% and 91% for catalyst 1-1, 36% and 96% for catalyst 1-2, and 63% and 88% for catalyst 1-3, respectively.

[Comparative Example 1] Production of 1-chloro-2,2-difluoroethylene using Catalyst 2 at a reaction temperature of 300°C The reaction was carried out in the same manner as in Example 1 except that Catalyst 2 was used as the solid catalyst. gone.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane was 3%, and the desired product, 1-chloro-2,2-difluoro. Ethylene selectivity was 63%.

[Comparative Example 2] Production of 1-chloro-2,2-difluoroethylene using 5.0% by mass of cesium chloride-supported activated carbon at a reaction temperature of 300° C. Using 5.0% by mass of cesium chloride-supported activated carbon as a solid catalyst Except for this, the reaction was carried out in the same manner as in Example 1.
5.0% by mass of cesium chloride-supported activated carbon was produced as follows.
The activated carbon was treated at 300° C. for 1 hour in a nitrogen atmosphere. An aqueous solution of cesium chloride (0.1 g of CsCl, 20 ml of water) was added to 2 g of the obtained activated carbon, and the mixture was stirred for 30 minutes and then dried under reduced pressure at 35 kPa and 80°C. Thereafter, heat treatment was performed at 450° C. for 3 hours in a nitrogen atmosphere to obtain 5.0 mass % cesium chloride-supported activated carbon.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane was 22.7%, and the desired product, 1-chloro-2,2 - The selectivity for difluoroethylene was 95%.

The results of Comparative Example 1, Examples 1-1 to 1-3, and Comparative Example 2 are shown in Table 1. The above results are also shown in FIG.

From Table 1 and FIG. 1, for the case where melamine, which is one of the basic substances, is not supported on activated carbon (Comparative Example 1), from one supporting treatment (Example 1-1) to two supporting treatments ( Example 1-2), 3 times of supporting treatment (Example 1-3), and as the amount of melamine supported increased, the conversion rate indicating reactivity gradually increased under the condition of a reaction temperature of 300 ° C. I understand. This indicates that the reaction proceeds even if melamine is not supported by activated carbon alone, but the reaction is accelerated by supporting melamine, and the reaction accelerates as the supported amount increases.
On the other hand, it is generally believed that the selectivity of the reaction decreases as the reaction becomes faster, that is, as the reaction becomes more intense. According to the results in Table 1 above, comparing Examples 1-2 and 1-3, the conversion rate, that is, the reaction rate increased as the amount of melamine supported increased, but the selectivity decreased slightly. Therefore, it can be seen that a high level of selectivity can be maintained by setting an appropriate reaction rate.

Further, in Table 1 and FIG. 1, when comparing the catalytic activity of the cesium chloride-supported activated carbon of Comparative Example 2 and the melamine-supported activated carbon of Examples 1-1 to 1-3, the catalytic activity was at least 300°C. Under the reaction conditions, it can be seen that the activated carbon carrying melamine has a higher conversion rate, that is, a higher reaction rate. More specifically, when the selectivity is added to the comparison between the two, it is understood that the melamine-supported activated carbon is more efficient as a reaction catalyst than the cesium chloride-supported activated carbon when the selectivity is set to 95%. .

[Examples 2-1 to 2-3] As solid catalysts, catalyst 1-1 (Example 2-1), catalyst 1-2 (Example 2-2) or catalyst 2-3 (Example 1-3 ) was used to produce 1-chloro-2,2-difluoroethylene at a reaction temperature of 350°C.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane and the selection of the target 1-chloro-2,2-difluoroethylene The rates were 36% and 95% for catalyst 2-1, 52% and 97% for catalyst 2-2, and 95% and 55% for catalyst 2-3, respectively.

[Examples 3-1 to 3-3] As solid catalysts, catalyst 1-1 (Example 3-1), catalyst 1-2 (Example 3-2) or catalyst 2-3 (Example 3-3 ) was used to produce 1-chloro-2,2-difluoroethylene at a reaction temperature of 400°C.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane and the selection of the target 1-chloro-2,2-difluoroethylene The rates were 80% and 84% for catalyst 3-1, 88% and 92% for catalyst 3-2, and 98% and 35% for catalyst 3-3, respectively.

Table 2 shows the results of Examples 1-1 to 1-3, Examples 2-1 to 2-3, and Examples 3-1 to 3-3. The results of Examples 1-1 to 1-3 are the same as Table 1.

From Table 2, melamine, which is one of the basic substances, was supported on activated carbon once (Example 1-1), twice (Example 1-2), and three times (implementation). Example 1-3) shows that as the amount of melamine supported increases, the conversion rate, which indicates reactivity, gradually increases under all conditions of reaction temperatures of 300°C, 350°C and 400°C. This indicates that the reaction proceeds faster as the amount of melamine supported on the activated carbon increases.
On the other hand, it is generally believed that the selectivity of the reaction decreases as the reaction becomes faster, that is, as the reaction becomes more intense. According to the results in Table 2 above, the reactivity (conversion rate) increases as the reaction temperature increases from 300°C to 400°C, but the selectivity increases as the reaction temperature increases from 300°C to 400°C. It was declining when it became
From these facts, it is practically important that the reaction conditions according to the present invention are not only high in reactivity but also under conditions in which the selectivity is maintained at a high level. Therefore, high reactivity (conversion rate) even under conditions of relatively low reaction temperature and the ability to maintain that state are practical as efficient reactions.

[Example 4] 1-Chloro-2,2 was used as a solid catalyst, and catalyst 1-3 was prepared by adding melamine and ethanol to activated carbon, stirring, and then drying under reduced pressure three times. - manufacture of difluoroethylene

A reaction was carried out in the same manner as in Example 1, except that the temperature of the catalyst layer was 280°C.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane was 35%, and the desired product, 1-chloro-2,2-difluoro Ethylene selectivity was 80%.

After 360 minutes of continuing the reaction, the gas flowing out of the reaction tube was analyzed by gas chromatography. , 2-difluoroethylene selectivity was 80%.

[Comparative Example 3] Production of 1-chloro-2,2-difluoroethylene using 5.0 mass% cesium chloride-supported activated carbon at a reaction temperature of 350°C

A reaction was carried out in the same manner as in Example 1 except that the solid catalyst was 5.0 mass % cesium chloride-supported activated carbon and the reaction temperature was 350°C.

As a result of gas chromatography analysis of the gas flowing out of the reaction tube immediately after the reaction, the conversion rate of 1,2-dichloro-1,1-difluoroethane was 38%, and the desired product, 1-chloro-2,2-difluoro Ethylene selectivity was 98%.

After 360 minutes of continuing the reaction, the gas flowing out of the reaction tube was analyzed by gas chromatography. , 2-difluoroethylene selectivity was 98%.

Table 3 shows the above results.

Table 3 compares the treatment of supporting melamine, which is one of the basic substances, on activated carbon three times (Example 4) and the activated carbon supporting cesium chloride (Comparative Example 3). However, in order to set the reactivity (conversion rate) of the melamine-supported activated carbon and the cesium chloride-supported activated carbon to be about the same, the reaction temperature was set to 280° C. for the former and 350° C. for the latter.
When the reaction was continued under these conditions, as can be seen from the results in Table 3, the conversion rate and the selectivity were almost the same at the start of the reaction. After 360 minutes of continuous reaction, both the conversion rate and the selectivity were maintained without change in the melamine loading treatment (Example 4) three times. On the other hand, with activated carbon supporting cesium chloride (Comparative Example 3), the conversion rate decreased from 38% to 30%. There are various possible differences between the two, and it is conceivable that the latter, where the reaction temperature is on the high temperature side, tends to deteriorate its function as a catalyst. Alternatively, it is conceivable that cesium chloride, which functions as a catalyst during the reaction, escapes from the activated carbon. Although the cause of these problems is unknown, at least it is clear that the catalytic function of melamine-supported activated carbon can exhibit its catalytic function more stably than that of cesium chloride-supported activated carbon, and it is a practical catalyst.

According to the present invention, the reaction proceeds under relatively low temperature conditions, and even when the reaction is continued for a long time, the decrease in reaction conversion rate and selectivity is extremely small. production became possible. 1-Chloro-2,2-difluoroethylene obtained by the method of the present invention can be used as a raw material for synthesizing various medicines, agricultural chemicals, and electronic materials.

Claims (4)

1,2-dichloro-1,1-difluoroethane is brought into contact with activated carbon with a basic substance, and then the activated carbon is reacted in the gas phase in the presence of a solid catalyst obtained by heating under a nitrogen atmosphere; - A method for producing chloro-2,2-difluoroethylene. The method for producing 1-chloro-2,2-difluoroethylene according to claim 1, wherein the basic substance is an organic amine or ammonia. The method for producing 1-chloro-2,2-difluoroethylene according to claim 1, wherein the basic substance is melamine. The method for producing 1-chloro-2,2-difluoroethylene according to any one of claims 1 to 3, wherein the reaction temperature is 250 to 550°C.

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