WO2024252818A1 - Method for separating vinylidene fluoride and acetylene - Google Patents

Abstract

Provided is a method for separating VdF and acetylene, the method comprising: a step for obtaining an extraction mixture by mixing a first mixture containing VdF and acetylene with an extraction solvent which is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene; and a step for distilling the extraction mixture to obtain a distillate in which the main component is VdF, and a canned article in which the main component is the extraction solvent and further contains acetylene.

Description

Method for separating vinylidene fluoride and acetylene

This disclosure relates to a method for separating vinylidene fluoride and acetylene.

Vinylidene fluoride is useful as a monomer for fluororesins.

For example, Patent Document 1 describes a method for separating vinylidene fluoride (VdF) and trifluoroethane, which includes a step of adding a first extraction solvent, which is at least one selected from the group consisting of alcohols, ketones, esters, amides, ethers, sulfoxides, and nitriles having 1 to 3 carbon atoms, to a first mixture containing VdF and trifluoroethane to obtain a second mixture, and an extractive distillation step of distilling the second mixture to obtain a distillate mainly composed of VdF and a bottoms product mainly composed of the first extraction solvent and containing trifluoroethane.

International Publication No. 2015/072305

The separation method described in Patent Document 1 is a method for separating VdF and trifluoroethane, and is not necessarily applicable to separating VdF and acetylene.

One aspect of the present disclosure aims to provide a method for efficiently separating VdF and acetylene from a mixture of VdF and acetylene.

The present disclosure includes the following aspects.
＜1＞
A step of mixing a first mixture containing vinylidene fluoride and acetylene with an extraction solvent which is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene to obtain an extraction mixture;
distilling the mixture for extraction to obtain a distillate mainly composed of vinylidene fluoride and a bottoms product mainly composed of the extraction solvent and further containing acetylene;
A method for separating vinylidene fluoride and acetylene, comprising:
＜2＞
The method for separating vinylidene fluoride and acetylene according to <1>, wherein in the mixture for extraction, the ratio of the molar amount of the extraction solvent to the molar amount of acetylene is 0.1 to 1000.
＜3＞
The method for separating vinylidene fluoride and acetylene according to <1> or <2>, further comprising a step of distilling the bottoms to recover an extraction solvent.
＜4＞
The method for separating vinylidene fluoride and acetylene according to <3>, wherein the recovered extraction solvent is reused in the step of obtaining a mixture for extraction.
＜5＞
The method for separating vinylidene fluoride and acetylene according to any one of <1> to <4>, wherein the first mixture further contains ethylene.
＜6＞
The method for separating vinylidene fluoride and acetylene according to any one of <1> to <5>, wherein the extraction solvent is chloroform.

According to one aspect of the present disclosure, a method for efficiently separating VdF and acetylene from a mixture of VdF and acetylene is provided.

In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.
In the present disclosure, combinations of two or more preferred aspects are more preferred aspects.
In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of the multiple substances, unless otherwise specified.

In this disclosure, "distillate" refers to material that is distilled from the top of a distillation column, and "bottoms" refers to material that is distilled from the bottom of a distillation column.
In the present disclosure, the term "main component" means that the molar amount of components other than the component in question is relatively small. The amount of the "main component" is preferably 50 mol % or more of the total, more preferably 60 mol % or more, even more preferably 70 mol % or more, and most preferably 80 mol % or more.
In this disclosure, unless otherwise specified, the boiling point of a compound is a value at normal pressure, which is 1.013×10 ⁵ Pa.

[Separation method]
The method for separating VdF and acetylene disclosed herein includes the steps of: mixing a first mixture containing VdF and acetylene with an extracting solvent that is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene to obtain an extraction mixture; and distilling the extraction mixture to obtain a distillate whose main component is vinylidene fluoride and a bottoms product whose main component is the extracting solvent and further contains acetylene.

The method for separating VdF and acetylene disclosed herein allows for efficient separation of VdF and acetylene.

VdF is useful as a monomer for fluororesin, but for example, when a polymerization reaction is carried out using a composition containing VdF and acetylene as an impurity, the acetylene reacts with the polymerization initiator, making it difficult for the desired polymerization reaction to proceed. This can easily result in the rate of the polymerization reaction slowing down or stopping, making it difficult to obtain the desired polymer. For this reason, it is desirable to separate VdF and acetylene to obtain high-purity VdF. However, VdF has a boiling point of -83°C, and acetylene has a boiling point of -84°C. Because VdF and acetylene have similar boiling points, it is difficult to separate and purify VdF and acetylene by normal distillation.

Patent Document 1 describes a method for separating VdF from trifluoroethane, but an extraction solvent suitable for the method for separating VdF from trifluoroethane is not necessarily a suitable extraction solvent for the method for separating VdF from acetylene.

The inventors have found that VdF and acetylene can be efficiently separated by using an extraction solvent containing at least one selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene.

The following describes each step of the disclosed method for separating VdF and acetylene.

<Mixing step>
The method for separating VdF and acetylene disclosed herein includes a step of mixing a mixture containing VdF and acetylene with a compound having a boiling point of −60 to 0° C. to obtain a mixture for extraction (hereinafter also referred to as the “mixing step”).

(First mixture containing VdF and acetylene)
The first mixture containing VdF and acetylene may contain other components other than VdF and acetylene, but from the viewpoint of efficiently obtaining high-purity VdF, it is preferable that the content of other components is small. Examples of other components include fluoroolefins other than VdF and ethylene. Among them, it is preferable that the first mixture contains ethylene, which may be mixed in during the production process of VdF.

The total content of VdF and acetylene relative to the total amount of the first mixture is, for example, 50 mol% or more, may be 80 mol% or more, may be 90 mol% or more, may be 99 mol% or more, or may be 100 mol%.

In the first mixture, the molar ratio of VdF to acetylene is not particularly limited. From the viewpoint of production efficiency, the ratio of the molar amount of acetylene to the molar amount of VdF (i.e., the molar ratio) is preferably 0.01 to 1, more preferably 0.01 to 0.5, and even more preferably 0.01 to 0.1.

The first mixture may be, for example, a reaction product containing VdF obtained by reacting various raw materials for the purpose of producing VdF.

(Extraction Solvent)
The extraction solvent is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene.

Chloroform is the preferred extraction solvent because it has excellent separation properties between VdF and acetylene. Furthermore, when chloroform is used as the extraction solvent, it also has excellent separation properties between VdF and ethylene. The boiling point of ethylene is -103.7°C, which is lower than the boiling point of VdF. Therefore, when normal distillation is performed, ethylene is accompanied by VdF, making separation difficult, but by using chloroform, which has a high affinity for ethylene, VdF and ethylene can be separated.

From the viewpoint of efficiently separating VdF and acetylene in the extraction mixture, it is preferable that the ratio of the molar amount of the extraction solvent to the molar amount of acetylene (extraction solvent/acetylene) is 0.1 to 1000.

For example, as described below, when a first mixture containing VdF and acetylene is supplied to the extractive distillation tower, and an extractive solvent is also supplied to the extractive distillation tower, "extractive solvent/acetylene" represents the molar ratio of the amount of extractive solvent supplied to the extractive distillation tower to the amount of acetylene supplied to the extractive distillation tower.

In the mixing step, from the viewpoint of separating VdF and acetylene with high efficiency, it is preferable to select the type of extraction solvent and adjust the amount of extraction solvent added so that the relative volatility Rv of the extraction mixture is greater than 1.1. The relative volatility Rv is preferably 1.2 or more, and more preferably 1.3 or more.

The relative volatility Rv of VdF to acetylene is expressed by the following formula.
Rv = (molar fraction of VdF in the gas phase / mole fraction of VdF in the liquid phase) / (molar fraction of acetylene in the gas phase / mole fraction of acetylene in the liquid phase)

The method of mixing the first mixture containing VdF and acetylene with the extraction solvent is not particularly limited. The extraction solvent may be added to the first mixture containing VdF and acetylene, or the first mixture containing VdF and acetylene may be added to the extraction solvent.

In addition, there are no particular limitations on the timing of obtaining the mixture for extraction, as long as it is obtained before the mixture for extraction is distilled.

From the viewpoint of efficiency in distilling the extraction mixture, which will be described later, it is preferable to supply an extraction solvent to the extractive distillation tower to which the first mixture containing VdF and acetylene has been supplied, prepare the extraction mixture in the extractive distillation tower, and perform distillation immediately after the preparation is completed.

The extraction mixture may contain other components other than VdF, acetylene, and the extraction solvent. Other components other than VdF, acetylene, and the extraction solvent that may be contained in the extraction mixture include other components that may be contained in the first mixture containing VdF and acetylene.

<Extractive distillation process>
The method for separating VdF and acetylene disclosed herein includes a step of distilling the extraction mixture to obtain a distillate whose main component is VdF and a bottoms product whose main component is the extraction solvent and further contains acetylene (hereinafter also referred to as the "extractive distillation step").

The extractive distillation process can be carried out using a commonly used distillation apparatus, for example, a distillation tower such as a plate tower, a packed tower, etc. Various conditions of the extractive distillation process, for example, the operating temperature, operating pressure, reflux ratio, total number of stages in the distillation tower, position of the charging stage, position of the extraction solvent supply stage, etc., are not particularly limited and can be appropriately selected to achieve the desired separation. When a distillation tower that is a plate tower is used in the extractive distillation process, the number of stages of the distillation tower can be, for example, 1 to 100, and from the viewpoint of obtaining VdF with high purity, 30 or more is preferable, and 50 or more is more preferable. Since both VdF and acetylene have low boiling points, it is preferable to carry out the extractive distillation under pressure, for example, a pressure of 0 to 5 MPaG (gauge pressure).

Furthermore, the temperatures at the top and bottom of the distillation tower are determined according to the operating pressure and the composition of the distillate and bottom products. In order to perform the distillation operation economically, taking into account the temperatures of the condensers and reheaters provided at the top and bottom of the tower, it is preferable that the temperature at the top of the tower be -60 to 100°C and the temperature at the bottom of the tower be -10 to 300°C. Extractive distillation can be performed in either a batch or continuous manner, or in a semi-continuous manner in which the distillate and bottom products are intermittently withdrawn or intermittently charged, but it is preferable to continuously supply the extraction solvent to the distillation apparatus.

The above-mentioned extraction solvent has an affinity for acetylene. Therefore, by extractively distilling an extraction mixture containing VdF, acetylene, and the extraction solvent, a distillate containing VdF as the main component is obtained from the top side of the extractive distillation tower. The composition of this distillate is not limited as long as it contains VdF as the main component, but the molar fraction of VdF in the distillate is preferably 90 mol% or more, and more preferably 99 mol% or more. In addition, the molar fraction of acetylene in the distillate is preferably 1/10 or less, and more preferably 1/100 or less, of the molar fraction of acetylene in the extraction mixture. The molar fraction of acetylene in the distillate is preferably 10 mol% or less, more preferably 1 mol% or less, and even more preferably 0.1 mol% or less.

A bottom product containing the extraction solvent as the main component and further containing acetylene is obtained from the bottom side of the extractive distillation tower. The composition of this bottom product is not limited as long as it contains the extraction solvent as the main component, but the molar fraction of the extraction solvent in the bottom product is preferably 30 mol % or more, and more preferably 50 mol % or more. The molar fraction of acetylene in the bottom product is preferably higher than the molar fraction of acetylene in the extraction mixture. Specifically, the molar fraction of acetylene in the bottom product is more preferably 1.1 or more of the molar fraction of acetylene in the extraction mixture, and even more preferably 2 or more.

<Distillation process>
The method for separating VdF and acetylene according to the present disclosure preferably further includes a step of distilling the bottoms to recover the extraction solvent (hereinafter also referred to as the "distillation step").

The distillation process can be carried out using a distillation apparatus similar to that used in the extractive distillation process. The various conditions of the distillation process, such as the operating temperature, operating pressure, reflux ratio, total number of stages in the distillation column, and the position of the feed stage, are not particularly limited and can be appropriately selected to achieve the desired separation.

The distillation process separates the extraction solvent from the VdF and acetylene, allowing the extraction solvent to be recovered.

In the distillation process, a bottom product containing the extraction solvent is obtained from the bottom side of the distillation tower. It is preferable to reuse the recovered extraction solvent in the above-mentioned extraction distillation process. In the method for separating VdF and acetylene disclosed herein, the difference in boiling points between acetylene and the extraction solvent is large, so that the separation between acetylene and the extraction solvent is excellent. Therefore, a high-purity extraction solvent can be recovered, making it suitable for reuse.

Below, the embodiments of the present disclosure will be described in detail using examples, but the embodiments of the present disclosure are not limited to these. Examples 1 to 4 are examples, and Examples 5 to 9 are comparative examples.

<Examples 1 to 9>
The following ingredients were mixed to prepare a first mixture:
VdF...0.134 mol Acetylene...0.111 mol Ethylene...1.000 mol Methane...0.0837 mol Chloromethane...0.0873 mol

As the extraction solvent, 20 g of the compound shown in Table 1 was used. In Example 5, no extraction solvent was used.
In Table 1, details of "AS-300", "AC-2000", and "AE-3000" are as follows.
AS-300: Product name "AS-300", manufactured by AGC Co., Ltd. A mixture of 1-chloro-2,3,3-trifluoro-1-propene (E) and 1-chloro-2,3,3-trifluoro-1-propene (Z).
AC-2000: Product name "ASAHIKLIN AC-2000", manufactured by AGC Co., Ltd. 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluorohexane.
AE-3000: Product name "ASAHIKLIN AE-3000", manufactured by AGC Co., Ltd. 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

The molar amounts of the extraction solvents listed in Table 1 are as follows:
Methanol: 0.625 mol Acetone: 0.345 mol Chloroform: 0.168 mol AS300: 0.135 mol Carbon tetrachloride: 0.130 mol AC2000: 0.0625 mol AE3000: 0.100 mol Cyclohexane: 0.238 mol

[Analysis conditions]
In the measurement of relative volatility, the composition of the obtained liquid was analyzed using a gas chromatograph (GC) using a DB-1 column (length 60 m × inner diameter 250 μm × thickness 1 μm, manufactured by Agilent Technologies).

[Measurement of relative volatility]
The prepared first mixture and, if necessary, an extraction solvent were poured into a pressure-resistant autoclave equipped with a pressure gauge. The temperature was adjusted so that the pressure was about 1.0 MPaG, and the mixture was held for one day to stabilize the composition inside the autoclave.

　Subsequently, samples of the liquid and gas phases were taken and analyzed by gas chromatography. Using the analysis results and the above-mentioned relative volatility formula, the relative volatility of acetylene relative to VdF and the relative volatility of ethylene relative to VdF were calculated. The calculation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 4, methanol, acetone, chloroform, or 1-chloro-2,3,3-trifluoro-1-propene was used as the extraction solvent, and therefore, it was found that the relative volatility of acetylene relative to VdF was higher than that of Example 5, in which no extraction solvent was used. Specifically, in all of Examples 1 to 4, the relative volatility of acetylene relative to VdF was 1.1 or more. Therefore, if extractive distillation is performed using these extraction solvents, a purified VdF product having a higher VdF content as the distillate from the distillation column compared to the mixture for extraction, that is, a VdF purified product containing VdF at a higher concentration, can be obtained, and efficient separation can be achieved.
In particular, in Example 3, chloroform was used as the extraction solvent, and it was found that the relative volatility of acetylene relative to VdF and the relative volatility of ethylene relative to VdF were both very high, allowing VdF and acetylene to be separated more efficiently.

On the other hand, in Examples 6 to 9, carbon tetrachloride, AC2000, AE3000, or cyclohexane were used as the extraction solvent, and it was found that the relative volatility of acetylene relative to VdF was very low and these solvents were not suitable for separating VdF and acetylene.

In the method for separating VdF and trifluoroethane described in Patent Document 1, AC2000 and AE3000 were suitable as extraction solvents, but in the method for separating vinylidene fluoride and acetylene disclosed herein, it was found that AC2000 and AE3000 were not suitable as extraction solvents.

The disclosure of Japanese Patent Application No. 2023-095061, filed on June 8, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (6)

A step of mixing a first mixture containing vinylidene fluoride and acetylene with an extraction solvent which is at least one compound selected from the group consisting of methanol, acetone, chloroform, and 1-chloro-2,3,3-trifluoro-1-propene to obtain an extraction mixture;
distilling the mixture for extraction to obtain a distillate containing vinylidene fluoride as a main component and a bottom product containing the extraction solvent as a main component and further containing acetylene;
A method for separating vinylidene fluoride and acetylene, comprising: The method for separating vinylidene fluoride and acetylene according to claim 1, wherein the ratio of the molar amount of the extraction solvent to the molar amount of acetylene in the extraction mixture is 0.1 to 1000. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, further comprising a step of distilling the bottoms to recover the extraction solvent. The method for separating vinylidene fluoride and acetylene according to claim 3, wherein the recovered extraction solvent is reused in the step of obtaining the extraction mixture. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, wherein the first mixture further contains ethylene. The method for separating vinylidene fluoride and acetylene according to claim 1 or 2, wherein the extraction solvent is chloroform.