JPH11158091A - Azeotropic composition of hexafluoopropylene dimer and acetonitrile and separation using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover a hexafluoropropylene dimer in a method for producing the hexafluoropropylene dimer using acetonitrile as a reaction solvent. SOLUTION: A reaction product substantially containing acetonitrile and a hexafluoropropylene dimer formed by a reaction is subjected to liquid-liquid separation to give a hexafluoropropylene dimer phase containing acetonitrile, which is subjected to distillation operation to distill an azeotropic composition substantially comprising acetonitrile and the hexafluoropropylene dimer. Then, a distillate comprising the hexafluoropropylene dimer containing substantially no acetonitrile is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an azeotropic composition of hexafluoropropylene dimer and acetonitrile, and to a method for separating the azeotropic composition by distillation using the azeotropic composition.
Hexafluoropropylene dimer can be used, for example, as a heating medium or solvent for high temperatures, or as a raw material for various industrial surfactants such as water / oil repellents.

[0002]

2. Description of the Related Art A method for producing a hexafluoropropylene dimer has been conventionally known. A method for selectively obtaining a hexafluoropropylene dimer is disclosed in
There are methods described in JP-A-34614 and JP-A-51-125307, and examples include a reaction for selectively producing hexafluoropropylene dimer using acetonitrile as a solvent. Mutual dissolution of acetonitrile and hexafluoropropylene dimer is limited, and in a reaction using acetonitrile as a solvent, an acetonitrile phase containing a small amount of hexafluoropropylene dimer and a hexafluoropropylene dimer containing a small amount of acetonitrile are used. The liquid phase separates from the monomer phase. In such a reaction, a substantial part of the generated hexafluoropropylene dimer separates from the acetonitrile phase and moves out of the reaction system, so that the generated hexafluoropropylene dimer is further converted to a hexafluoropropylene trimer. This is advantageous in that it can be suppressed. The types of hexafluoropropylene dimer produced include the following (1) and (2): (1) (CF ₃ ) ₂ CFCF = CFCF ₃ Normal boiling point 48 ° C. (hereinafter referred to as “hexafluoropropylene”) (Also referred to as "propylene dimer (1)" or simply "dimer (1).) (2) (CF ₃ ) ₂ C = CFCF ₂ CF ₃ Normal boiling point 51 ° C. (hereinafter referred to as“ hexafluoropropylene dimer Also, these two types of dimers are collectively referred to as “hexafluoropropylene dimer” or simply “dimer”. .

[0003]

In the method described above,
A small amount of acetonitrile is dissolved in the hexafluoropropylene dimer phase obtained by liquid-liquid separation, and it cannot be said that a hexafluoropropylene dimer with high purity was obtained as it is. In JP-A-49-134614, water is added to a mixture containing a hexafluoropropylene dimer and acetonitrile as main components obtained by the reaction, followed by liquid-liquid separation and distillation to obtain hexafluoropropylene. Dimer has been obtained. However, in this method, acetonitrile as a solvent contains water, so that it cannot be reused in the reaction as it is, and a separation operation from water is required, which is disadvantageous as an industrial process.

[0004]

The present inventors have studied a method for separating acetonitrile from a hexafluoropropylene dimer phase containing acetonitrile. As a result, the hexafluoropropylene dimer and acetonitrile have the lowest azeotropic composition. Is formed. Also, by utilizing this azeotropic composition, a method for efficiently separating acetonitrile or hexafluoropropylene dimer from a mixture comprising acetonitrile and hexafluoropropylene dimer with a minimum loss is provided. They have found and completed the present invention.

Accordingly, in a first aspect, the present invention provides:
An azeotropic composition (or mixture) consisting essentially of hexafluoropropylene dimer and acetonitrile is provided. That is, in the present invention, the molar ratio of hexafluoropropylene dimer (1) / acetonitrile is 78-85 / 15-
22 (pressure 0 to 20 kg / cm ² -G
(Gauge pressure), azeotropic temperature of 40 to 150 ° C. (depending on pressure)), and hexafluoropropylene dimer (2)
/ Acetonitrile molar ratio 74-81 / 19-26
(Pressure 0-20 kg / cm ² -G, azeotropic temperature 44-15
5 ° C. (varies with pressure). For the detailed data of this azeotropic composition, reference can be made to Examples described later.

[0006] Such an azeotropic composition is a mixture comprising hexafluoropropylene dimer and acetonitrile, preferably a mixture consisting essentially of hexafluoropropylene dimer and acetonitrile (eg hexafluoropropylene dimer). When a distillation operation is performed to separate one of the components from the reaction product that produces the compound (1), there is a useful use that can be used as reflux.

[0007] Such an azeotropic composition is separated in a temperature range used industrially. For example, -15
At a temperature of 45 ° C., the azeotropic composition has a relatively high concentration of hexafluoropropylene dimer (eg, 90%).
〜98.5 mol%), a hexafluoropropylene dimer phase, and an acetonitrile phase having a relatively high concentration of acetonitrile (for example, 99.0 to 99.9 mol%). At the most commonly used industrial operating temperatures (e.g., 20-40 [deg.] C.), the hexafluoropropylene dimer concentration in the hexafluoropropylene dimer phase is, for example, 91-96 mol% and the acetonitrile phase The acetonitrile concentration at
9.1 to 99.4 mol%.

In a second aspect, the present invention provides a method for preparing a mixture of acetonitrile or hexafluoropropylene dimer (1) or (2) from a mixture comprising hexafluoropropylene dimer (1) or (2) and acetonitrile. Comprising subjecting the mixture to a distillation operation to distill an azeotropic composition consisting essentially of hexafluoropropylene dimer (1) or (2) and acetonitrile. A separation method is provided. In this case, it is substantially free of hexafluoropropylene dimer (1) or (2) or acetonitrile (for example, if the concentration of such a compound is between 0.
1 mol% or less, preferably 0.001 mol% or less).

In one more specific separation method, the mixture is an acetonitrile phase in which the hexafluoropropylene dimer (1) is dissolved (for example, saturated), and the hexafluoropropylene dimer (1) is distilled. ) And acetonitrile are obtained as a distillate, and acetonitrile substantially free of hexafluoropropylene dimer (1) is obtained as a bottom product.

[0010] In one more specific separation method, the mixture is an acetonitrile phase in which hexafluoropropylene dimer (2) is dissolved, and is substantially separated from hexafluoropropylene dimer (2) and acetonitrile by a distillation operation. And acetonitrile substantially free of hexafluoropropylene dimer (2) is obtained as a bottom product.

In one more specific separation method, the mixture is a hexafluoropropylene dimer (1) phase in which acetonitrile is dissolved, and is substantially separated from the hexafluoropropylene dimer (1) and acetonitrile by a distillation operation. And a hexafluoropropylene dimer (1) substantially free of acetonitrile is obtained as a bottom product.

In one more specific separation method, the mixture is a hexafluoropropylene dimer (2) phase in which acetonitrile is dissolved, and is substantially separated from the hexafluoropropylene dimer (2) and acetonitrile by a distillation operation. And a hexafluoropropylene dimer (2) substantially free of acetonitrile is obtained as a bottom product.

In a third aspect, the present invention provides a method for converting acetonitrile or hexafluoropropylene dimers (1) and (2) from a mixture comprising hexafluoropropylene dimers (1) and (2) and acetonitrile. A method of separating, comprising the step of subjecting the mixture to a distillation operation to distill an azeotropic composition consisting essentially of hexafluoropropylene dimers (1) and (2) and acetonitrile. A separation method is provided.

In one more specific separation method, the mixture is an acetonitrile phase in which hexafluoropropylene dimers (1) and (2) are dissolved, and the hexafluoropropylene dimer (1) is distilled off. And (2) and an azeotropic composition consisting essentially of acetonitrile is obtained as a distillate, and acetonitrile substantially free of hexafluoropropylene dimers (1) and (2) is obtained as a distillate.

[0015] In one more specific separation method, the mixture is a phase of hexafluoropropylene dimer (1) and (2) in which acetonitrile is dissolved, and the hexafluoropropylene dimer (1) is subjected to a distillation operation. ) And (2) and an azeotropic composition consisting essentially of acetonitrile is obtained as a distillate, and hexafluoropropylene dimers substantially free of acetonitrile (1) and (2)
Are obtained as cans.

That is, in the above separation method of the present invention,
Subjecting a mixture comprising hexafluoropropylene dimer and acetonitrile to a distillation operation to distill an azeotropic composition, thereby removing substantially all of one of the components in the mixture as an azeotropic composition; The remainder of the mixture consisting essentially of the other components is obtained as bottoms. Which component can be obtained as a bottom product, the amount of acetonitrile is greater than the amount forming an azeotropic composition, compared to the amount of acetonitrile forming the mixture and the amount of hexafluoropropylene dimer In the case, acetonitrile is obtained as a bottom product, and when the amount is small, hexafluoropropylene dimer is obtained as a bottom product.

As described above, when both the hexafluoropropylene dimers (1) and (2) are present in the mixture, the mixture is mixed with the hexafluoropropylene dimer (1) and acetonitrile. It may be considered that the mixture is composed of a mixture of hexafluoropropylene dimer (2) and acetonitrile. Under predetermined operating conditions (particularly operating temperature and pressure), hexafluoropropylene dimer (1) The amount of acetonitrile needed to form the azeotropic composition and the amount of acetonitrile hexafluoropropylene dimer (2) needed to form the azeotropic composition are actually included in the sum of the two. By comparing the amount of acetonitrile and considering which component is higher, it is possible to determine which component can be obtained as a bottom product. That. That is, compared with the azeotropic composition, too many components are obtained as a bottom product.

If the mixture contains, in addition to the hexafluoropropylene dimer and acetonitrile, other components (for example, hexafluoropropylene trimer), such other components may include the hexafluoropropylene dimer of that component. Depending on the affinity for the product and acetonitrile, the operating conditions of the distillation step, etc., it may behave together with the azeotropic composition to be distilled off or together with the hexafluoropropylene dimer or acetonitrile to be discharged. In some cases, such other components may behave together with both distillate and bottoms.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The separation method of the present invention can be carried out by continuous or batch azeotropic distillation using a commonly used distillation apparatus. The distillation apparatus may be a commonly used packed column or plate column. The operating conditions adopted for the distillation operation can be appropriately selected by those skilled in the art in consideration of the distillation apparatus to be used, the azeotropic temperature, restrictions on utilities, and the like. As the reflux for this distillation operation, it is preferable to use the azeotropic composition to be distilled off as it is after condensation.

For example, the pressure of the distillation operation is 0 to 20 kg /
cm ² -G (top temperature of 40 to 150 ° C.), more preferably 0 to 1 kg / cm ² -G (top temperature of 40 to 64 ° C.). The number of stages of the distillation apparatus can be appropriately selected according to the composition of the mixture supplied to the apparatus, the degree of separation of distillate and bottoms (eg, impurity concentration), reflux ratio, and the like.

According to the separation method of the present invention, acetonitrile is used as a reaction solvent and KF is used as a catalyst in a reactor such as an autoclave, and hexafluoropropylene is continuously blown into the reactor to form a dimer. The reaction can be conveniently applied to the reaction. In this case, liquid-liquid separation is performed after the reaction to obtain a hexafluoropropylene dimer phase in which acetonitrile is dissolved, and this dimer phase is subjected to a distillation operation to convert acetonitrile with hexafluoropropylene dimer. The remaining dimer can be obtained as a bottom product by distilling as a boiling composition.

Accordingly, the present invention relates to a process for producing a hexafluoropropylene dimer using acetonitrile as a reaction solvent, wherein the reaction product substantially comprises acetonitrile and hexafluoropropylene dimer produced by the reaction. The hexafluoropropylene dimer phase containing acetonitrile obtained by subjecting the product to liquid-liquid separation is subjected to a distillation operation to distill an azeotropic composition substantially consisting of acetonitrile and hexafluoropropylene dimer. And obtaining a bottom product comprising hexafluoropropylene dimer substantially free of acetonitrile.

The present invention also relates to a process for producing hexafluoropropylene dimer using acetonitrile as a reaction solvent, wherein a reaction product substantially comprising acetonitrile and hexafluoropropylene dimer produced by the reaction is provided. The acetonitrile phase comprising the hexafluoropropylene dimer obtained by liquid-liquid separation is subjected to a distillation operation to distill an azeotropic composition substantially consisting of acetonitrile and hexafluoropropylene dimer, A method for recovering acetonitrile, comprising obtaining a bottom product comprising acetonitrile substantially free of fluoropropylene dimer.

In the above-mentioned method for producing a hexafluoropropylene dimer of the present invention, it is preferable to combine such a method for recovering acetonitrile. More specifically, the method for producing a hexafluoropropylene dimer of the present invention can be carried out as follows.

The reaction method for producing a hexafluoropropylene dimer from hexafluoropropylene using acetonitrile as a solvent is a known method as described above, and specifically, a method described in JP-A-49-134614. Reference can be made to JP-A-51-125307.

The hexafluoropropylene dimer phase in which acetonitrile is dissolved, which is produced by this reaction, is charged into a distillation column (preferably a rectification column) and distilled under normal pressure or pressure. When this distillation is carried out batchwise, an azeotropic composition of hexafluoropropylene dimer and acetonitrile is distilled off as a first distillation, and hexafluoropropylene dimer substantially containing no acetonitrile is obtained as a bottom product. . Alternatively, after distilling off the first fraction, hexafluoropropylene dimer is also obtained as distillate. In this case, there is an advantage that high-boiling substances are not contained in the hexafluoropropylene dimer.

The azeotropic composition, which is the first distillation, separates when condensed under ordinary operating temperature conditions. Therefore, liquid-liquid separation is performed, and the acetonitrile phase containing the hexafluoropropylene dimer is subjected to the reaction step. The hexafluoropropylene dimer containing acetonitrile can be recycled to the distillation column again. Alternatively, the entire amount of acetonitrile containing the first fraction of hexafluoropropylene dimer may be returned to the reaction vessel. Either method can separate hexafluoropropylene dimer without loss.

The above-mentioned distillation can be carried out continuously. In this case, the hexafluoropropylene dimer phase in which acetonitrile is dissolved is supplied to the first distillation column (azeotropic distillation column), and the distillation is carried out. Distilling an azeotropic composition consisting essentially of fluoropropylene dimer and acetonitrile,
Hexafluoropropylene dimer without acetonitrile is obtained as bottom product. This bottom product can be supplied to a second distillation column (refining distillation column) to distill a higher purity purified hexafluoropropylene dimer and separate it from components having a higher boiling point. Become.

In the above-mentioned reaction for producing a hexafluoropropylene dimer, the acetonitrile phase in which the hexafluoropropylene dimer is obtained by the liquid separation after the reaction is directly used as a solvent for producing the hexafluoropropylene dimer. Usually, there is no need for purification to obtain acetonitrile alone, since it can be reused in the reaction. If you want to separate acetonitrile,
For example, acetonitrile can be separated as follows.

The acetonitrile phase in which the hexafluoropropylene dimer is dissolved is charged into a distillation column, and distillation is performed under normal pressure or under pressure. Distill an azeotropic composition of hexafluoropropylene dimer and acetonitrile as the first distillation at the time of distillation, and distill acetonitrile substantially free of hexafluoropropylene dimer as a bottom product or further distillation Get as things.

As in the case of the above-mentioned treatment of the hexafluoropropylene dimer phase, the azeotropic composition which is the first distillate is subjected to liquid-liquid separation again, and the acetonitrile phase containing the hexafluoropropylene dimer is subjected to the reaction step. It may be returned or returned to the distillation column again. Similarly, the hexafluoropropylene dimer phase containing acetonitrile obtained by liquid separation may be recycled to a distillation column for treating the hexafluoropropylene dimer phase from the above reaction product. Thus, acetonitrile can be separated without loss. This distillation operation can be carried out batchwise or continuously.

[0032]

EXAMPLES Example 1 Mutual solubility (liquid-liquid equilibrium) between hexafluoropropylene dimer and acetonitrile was measured by the following method. 15 g of acetonitrile and 15 g of hexafluoropropylene dimer (1) or (2) are placed in a vial with a septum cap having an internal volume of 30 cc. Each was stirred at a predetermined temperature for about 24 hours, then allowed to stand at that temperature for 12 hours to separate the layers, and the upper and lower layers were analyzed by gas chromatography to determine the composition. The results are shown in Tables 1 and 2. The results of Table 1 are shown in FIGS. 1 and 2:

[0033]

Table 1 Hexafluoropropylene dimer (1) / acetonitrile mutual solubility Temperature (° C) Lower layer (mol%) Upper layer (mol%) Acetonitrile dimer (1) Acetonitrile dimer (1) -13 1.93 98.07 99.67 0.33 3 2.69 97.31 99.59 0.41 26 5.00 95.00 99.31 0.69 45 9.76 90.24 99.12 0.88

[0034]

Table 2 Hexafluoropropylene dimer (2) / acetonitrile mutual solubility Temperature (° C) Lower layer (mol%) Upper layer (mol%) Acetonitrile dimer (2) Acetonitrile dimer (2) -13.09 94.91 99.84 0.163 3 5.48 94.52 99.78 0.22 26 6.15 93.85 99.66 0.34 45 6.75 93.25 99.53 0.47

From these results, it is found that hexafluoropropylene dimer and acetonitrile do not dissolve indefinitely in a wide temperature range, that is, in a temperature range practically employed industrially, but have a mutual solubility in a wide range. Shows that there is a limit.

Example 2 The gas-liquid equilibrium between hexafluoropropylene dimer and acetonitrile was measured at atmospheric pressure by the following method. A mixture having a composition in which hexafluoropropylene dimer and acetonitrile are mutually dissolved is given by volume 2
The mixture was placed in a 00 cc round bottom flask (with a Dimroth condenser), and the still portion was heated with a mantle heater. After stabilization, samples of a liquid phase and a gas phase were obtained and subjected to composition analysis.

A mixture having a composition in which hexafluoropropylene dimer and acetonitrile do not dissolve in each other (that is, liquid-liquid separation) is placed in a 1-liter round bottom flask (with a Dimroth condenser), Part is heated with a mantle heater, and after stabilization, the gas phase is reduced to about 1c.
After sampling c and dissolving in a CFC solvent, the composition was analyzed by gas chromatography. Regarding the liquid phase composition, the composition was initially charged into the still because the liquid phase portion was excessively large with respect to the gas phase. The results are shown in Tables 3 and 4. It is shown in FIGS. 3 and 4.

[0038]

Table 3 Vapor-liquid equilibrium temperature of hexafluoropropylene dimer (2) / acetonitrile system Temperature (° C) Liquid phase composition (mol%) Gas phase composition (mol%) Still acetonitrile dimer (2) acetonitrile dimer (2) 50.0 0.194 99.806 2.416 97.584 49.0 1.301 98.699 5.741 94.259 49.0 1.416 98.584 9.093 90.907 46. 0 4.315 95.885 12.457 87.543 46.0 87.925 12.075 20.766 79.234 46.0 64.380 35.620 17.8000 82.200 46.0 8.832 91 .168 14.359 85.641 46.0 31.517 68.483 19.408 80.592 78.0 99.939 0.061 81.727 18.273 73.0 99.8829 0.171 69.2800.720 68.0 99.731 0.269 36.423 63.577 64.0 99.565 0.435 23.570 76.430 57.0 99.406 0.594 21.291 78.709

[0039]

Table 4 Vapor-liquid equilibrium temperature of hexafluoropropylene dimer (1) / acetonitrile system Temperature (° C) Liquid phase composition (mol%) Gas phase composition (mol%) Still acetonitrile dimer (1) acetonitrile dimer (1) 45.0 0.466 99.534 4.519 95.481 41.0 9.000 91.000 12.057 87.943 40.0 22.505 77.495 15.940 84.060 40. 0 53.981 46.019 16.112 83.888 68.0 99.272 0.728 23.184 76.816 70.0 99.699 0.301 38.995 61.005

As is clear from the obtained XY diagram,
It is clear that all hexafluoropropylene dimers azeotrope with acetonitrile. The azeotropic composition is 80 to 8 in the case of hexafluoropropylene dimer (1) / acetonitrile in a molar ratio under atmospheric pressure.
3/17 to 20%, and in the case of hexafluoropropylene dimer (2) / acetonitrile, 84 to 87/1
3-16%.

(Example 3) Vapor-liquid equilibrium was measured in the same manner as in Example 2 with various changes in the system pressure, and the azeotropic composition and azeotropic temperature at each pressure were determined. The results are shown in Tables 5 and 6, and FIGS.

[0042]

Table 5 Changes in azeotropic point and azeotropic composition with pressure (in case of dimer (1)) Pressure (kg / cm ² -G) Temperature (° C) Composition of dimer (1) (mol%) 0 40 0.0 84.6 0.5 50.8 84.0 1 59.0 83.5 3 81.1 82.1 5 95.8 81.2 10 120.3 79.8 20 149.6 78.5

[0043]

Table 6 Changes in azeotropic point and azeotropic composition with pressure (in case of dimer (2)) Pressure (kg / cm ² -G) Temperature (° C) Composition of dimer (2) (mol%) 0 44 0.0 80.6 0.5 54.9 80.0 1 63.2 79.5 3 85.7 78.2 5 100.5 77.3 10 125.3 76.0 20 155.0 74.8

Example 4 A hexafluoropropylene dimer was produced. This production will be described with reference to FIG. 7 which shows a schematic flow sheet of the method for producing a hexafluoropropylene dimer of the present invention. Solvent (acetonitrile) 55
g and 2 g of a catalyst (potassium fluoride) were charged into the autoclave (1), and hexafluoropropylene (2) was continuously supplied at a reaction temperature of 25 ° C. at a flow rate of 35 cc / min. The reaction was carried out at a reaction pressure of 2.2 kg / cm ² -G for 140 minutes. Thereafter, the supply of hexafluoropropylene was stopped to stop the reaction, and the mixture was allowed to stand still to cause liquid-liquid separation in the reactor.

As a lower layer, 31 g of a hexafluoropropylene dimer phase in which acetonitrile (concentration 9.0 mol%) is dissolved, and as an upper layer, hexafluoropropylene dimer (concentration 1.1 mol%) is dissolved. 56 g of acetonitrile phase were obtained. Only this lower layer was taken out of the reactor and stored in the dimer storage tank (3). Hexafluoropropylene was supplied again while the acetonitrile phase in the upper layer was left in the reactor, the reaction operation was performed under the same conditions, and only the lower layer was stored in the dimer tank.

The reaction was carried out intermittently as described above, and when 300 g of the accumulated lower layer was obtained, the lower layer was charged into the distillation column (4), and the operation pressure (top) was 0 kg / cm ² -G.
First, an azeotrope of hexafluoropropylene dimer and acetonitrile is first distilled (at a top temperature of 41 ° C.).
And stored in the first receiver (5). In this embodiment,
This first fraction was recycled to the reactor (1) without separation, and used for the next reaction. In addition, this first stay is 6
The lower layer was a hexafluoropropylene dimer phase in which acetonitrile was dissolved, and the upper layer was an acetonitrile phase in which hexafluoropropylene dimer was dissolved.

Following the first distillation, 200 g was distilled off as the main distillation and stored in the receiver 6, leaving 40 g of stills. This main fraction was a high-purity hexafluoropropylene dimer substantially containing no acetonitrile (0.001 mol% or less), and had a purity that can be used as a product for a predetermined purpose.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of measuring the mutual solubility (upper layer) between hexafluoropropylene dimer (1) and acetonitrile.

FIG. 2 is a graph showing the measurement results of the mutual solubility (lower layer) between hexafluoropropylene dimer (1) and acetonitrile.

FIG. 3 is a graph showing a gas-liquid equilibrium relationship (under atmospheric pressure) of acetonitrile / hexafluoropropylene dimer (2).

FIG. 4 is a graph showing a gas-liquid equilibrium relationship (under atmospheric pressure) of acetonitrile / hexafluoropropylene dimer (1).

FIG. 5 is a graph showing a change in azeotropic composition of hexafluoropropylene dimer (1) and acetonitrile with pressure.

FIG. 6 is a graph showing a change in azeotropic composition of hexafluoropropylene dimer (2) and acetonitrile with pressure.

FIG. 7 shows a schematic flow sheet of the method for producing a hexafluoropropylene dimer of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Hexafluoropropylene, 3 ... Dimer storage tank, 4 ... Distillation apparatus, 5 ... Initial distillation (azeotropic mixture) storage tank,
6 ... Main distillation (hexafluoropropylene dimer) storage tank.

Claims (7)

[Claims] An azeotropic composition of a hexafluoropropylene dimer and acetonitrile. 2. The hexafluoropropylene dimer,
(1) (CF ₃ ) ₂ CFCF = CFCF ₃ , and the molar ratio of hexafluoropropylene dimer / acetonitrile in the azeotropic composition is 78-85 / 15-22%.
An azeotropic composition as described. 3. The hexafluoropropylene dimer,
(2) (CF ₃₎ a ₂ C = CFCF ₂ CF _3, the molar ratio of hexafluoropropylene dimer / acetonitrile azeotrope is 74 to 81/19 to 26% in a claim 1 co according Boiling composition. 4. Hexafluoropropylene dimer (1)
Or separating acetonitrile or hexafluoropropylene dimer (1) or (2) from a mixture comprising (2) and acetonitrile,
A separation process comprising subjecting the mixture to a distillation operation to distill an azeotropic composition consisting essentially of hexafluoropropylene dimer (1) or (2) and acetonitrile. 5. Hexafluoropropylene dimer (1)
And (2) and a method for separating acetonitrile or hexafluoropropylene dimer (1) and (2) from a mixture comprising acetonitrile, the mixture being subjected to a distillation operation to obtain a hexafluoropropylene dimer A method comprising the steps of: (1) and (2) and a step of distilling an azeotropic composition consisting essentially of acetonitrile. 6. A method for producing hexafluoropropylene dimer using acetonitrile as a reaction solvent, wherein a reaction product substantially comprising acetonitrile and hexafluoropropylene dimer produced by the reaction is liquid-liquid The hexafluoropropylene dimer phase comprising acetonitrile obtained by separation is subjected to a distillation operation to distill an azeotropic composition substantially consisting of acetonitrile and hexafluoropropylene dimer. A method for producing a bottom product comprising a substantially free hexafluoropropylene dimer. 7. A distillation operation of an acetonitrile phase containing hexafluoropropylene dimer obtained by liquid-liquid separation of a reaction product substantially containing acetonitrile and hexafluoropropylene dimer formed by the reaction. Distilling an azeotropic composition consisting essentially of acetonitrile and hexafluoropropylene dimer,
7. The process according to claim 6, wherein a bottom product comprising acetonitrile substantially free of hexafluoropropylene dimer is obtained.