JP3175286B2 - An azeotropic mixture of hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane and a method for purifying 1,1,1-trifluoro-2-chloroethane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to hydrogen fluoride (hereinafter referred to as H).
Called F. ) And 1,1,1-trifluoro-2-chloroethane (hereinafter, referred to as R-133a) and an azeotropic mixture of HF and R-133a to remove HF and remove R-
133a. R-133a is receiving attention as an alternative refrigerant to dichlorodifluoromethane. Further, R-133a is HFC-134a (1,
It is useful as a raw material for (1,1,2-tetrafluoroethane) and as a raw material for trifluoroethanol.

[0002]

2. Description of the Related Art R-133a is usually produced by reacting a chlorinated hydrocarbon such as trichloroethylene with HF. Until now, a method of removing HF by washing a mixture formed by the reaction, which is mainly composed of HF and R-133a, with an aqueous phase has been used. However, a large amount of alkali is used to neutralize the washing solution. It is not an effective method because it requires.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted research on a method for removing HF from a mixture containing HF and R-133a as a main component. As a result, when the mixture is cooled to 7 ° C. or less,
Separation into an upper liquid phase rich in HF and a lower liquid phase rich in R-133a (that is, the ratio of HF / R-133a in the lower liquid phase is smaller than that before the phase separation). And R-133a formed the lowest azeotrope, and completed the present invention. This azeotrope is H
HF and / or R from the mixture of F and R-133a
-133a can be used as a reflux in a distillation operation when separating, thereby enabling an effective separation.

[0004] Therefore, the present invention provides a first gist of the present invention.
An azeotropic mixture of F and R-133a is provided. The boiling point of this azeotrope is about -2 ° C under atmospheric pressure. Further, the present invention provides, in a second aspect, HF and R-133
a) and the upper liquid phase rich in HF and R-133
a) to separate at least one component and preferably substantially separate it from the other component by a suitable treatment method that preferentially removes HF or R-133a. A method for purifying any of the above components is provided. As used herein, the term “concentration and purification” means that the concentration of any one component of the mixture is relatively increased and the concentration of the other component is relatively reduced.

In a third aspect of the present invention, HF
And preferably a mixture of R-133a (preferably according to the second aspect of the present invention, after cooling and phase separation).
a) as a lower liquid phase rich in a or a mixture as an upper liquid phase rich in HF)
-133a as an azeotrope and substantially HF
Or R-133a or HF not containing R-133a
And a method for purifying R-133a or HF.

[0006] As mentioned above, there is a (minimum) azeotrope in the binary system of HF and R-133a. This azeotrope was first discovered by the present inventors. HF and R-133
The mixture with HF / R-13 is distilled under atmospheric pressure.
It has been found that R-133a cannot be concentrated above about 65/35 at a molar ratio of 3a. In other words,
The liquid phase having this composition ratio is the same as the composition ratio of the gas phase in an equilibrium state. The azeotropic composition of HF and R-133a changes its molar ratio depending on the pressure, and the HF / R-133a HF / 1.5 kg / cm ² G
The molar ratio of R-133a is about 60/40, 4.0 kg / cm ² G
Is about 55/45, and the molar ratio at 15 kg / cm ² G is about 45/55. Further, HF / R-133
When attention is paid to the a ratio, the ratio of R-133a in the lower liquid phase is increased by cooling phase separation compared to before the phase separation. In this case, the concentration of R-133a in the lower liquid phase is azeotropic. It has been clarified that the composition shifts in a direction rich in R-133a.

By cooling the mixture of HF and R-133a, a lower liquid phase rich in R-133a and an upper liquid phase rich in HF are obtained. That is, by simply cooling, it is possible to obtain an upper liquid phase and a lower liquid phase which are richer in either concentration as compared with the concentration of the original mixture. From the resulting lower liquid phase, a suitable treatment (eg, distillation, extraction, absorption, adsorption,
By removing HF by a treatment such as a reaction such as neutralization with an alkali, the concentration of R-133a can be further increased, that is, R-133a can be concentrated and purified. vice versa,
Since the upper liquid phase is rich in HF, it can be purified by increasing the concentration of HF by performing an appropriate treatment for mainly removing R-133a.
Thus, simply cooling allows the first stage separation to be easily achieved.

[0008] A temperature of 7 ° C or less is used as the temperature for performing the cooling phase separation. Above 7 ° C, no phase separation phenomenon is observed regardless of the HF / R-133a ratio. A preferred range is 5 ° C or less. Above 5 ° C., the composition difference between the upper and lower liquid phases is small, and the difference in specific gravity is also close, so that separation may not be sufficient. The lower limit of the temperature is the freezing point of R-133a (about-
The temperature is not particularly limited as long as it is 100 ° C. or higher, but is approximately −5.
It is about 0 ° C. or higher. Below this temperature, cooling requires a lot of energy and is not economically efficient. Particularly preferred temperatures are in the range of -20C to 0C.

[0009] The mixture of R-133a and HF can be directly distilled using a distillation apparatus to remove HF. In this case, it has been found that R-133a and HF form an azeotrope, so that R-1
When the composition of 33a is larger than the azeotropic composition, R-133
When an azeotropic mixture of a and HF is used as reflux, R-133a substantially free of HF can be effectively obtained from the bottom of the column. As the azeotropic distillation apparatus, any apparatus having a function necessary for distillation can be used. Particularly favorable results are obtained in the case of a rectifying device such as a tray column or a packed column. Further, either batch distillation or continuous distillation can be performed.

In a particularly preferred embodiment of the present invention, R-13
After cooling the mixture of 3a and HF, it is separated into a lower liquid phase rich in R-133a and an upper liquid phase rich in HF, and each liquid phase is separately azeotropically distilled in a distillation column. Therefore, when the composition of the mixture of R-133a and HF is richer in HF than the azeotropic composition, the azeotropic mixture of R-133a and HF is extracted from the upper part (column top) of the distillation apparatus. (Distilled), substantially R-13 remaining in the lower part (tower bottom)
HF not containing 3a can be extracted (canned). Further, since the lower liquid phase is richer in R-133a than the azeotropic composition as described above, an azeotropic mixture of R-133a and HF is extracted from the upper part of the distillation apparatus, and substantially remains in the lower part. R-133a containing no HF can be extracted.

The present invention is most effective for removing HF from a mixture containing R-133a and HF obtained by fluorinating trichloroethylene with HF in the gas phase or liquid phase in the presence of a catalyst. The most preferred embodiments of the present invention are shown below.

FIG. 1 is a flow sheet showing an example of the separation apparatus used in the present invention. Usually, in the above-mentioned reaction, a product is extracted in a gas phase. R-133 in the resulting mixture.
It contains a small amount of organic matter in addition to a, HF and hydrogen chloride. R- is obtained by removing hydrogen chloride from the mixture by distillation.
The mixture of 133a and HF is cooled to + 7 ° C. or lower through a cooler, and guided to the liquid phase separation device 1 (liquid-liquid separation device, for example, a liquid separation device such as a decanter). The lower liquid phase rich in R-133a separated in the separation device is
And distills off HF from the top to form an azeotrope 5 with R-133a. At this time, the distilled HF
And a portion of the azeotrope of R-133a was returned to the top of the distillation apparatus as reflux 7 and the remaining azeotrope
After cooling to + 7 ° C. or lower at, it is sent to the liquid phase separation device 1 and the above processing is repeated. R-133a substantially free of HF is present at the bottom of the distillation apparatus 3 and is withdrawn as bottom product 9.

On the other hand, the HF-rich upper liquid phase can be recycled to the reaction system if this is possible. If this is not possible, another distillation device is required. The upper liquid phase led to the distillation apparatus 23 in FIG.
It is separated into an azeotrope of 3a and HF and HF substantially free of R-133a. In the distillation apparatus 23, a part of the azeotropic mixture 25 of HF and R-133a which is similarly distilled is returned to the top of the distillation apparatus as reflux 27. The remaining azeotropic mixture is cooled again to + 7 ° C. or lower in the cooler 31 and then returned to the liquid / liquid separation device 1. Substantially R-133a
Are not reused. In this manner, R-133a can be separated while effectively using all HF. Such a series of operations can be performed in a batch manner, but is preferably performed by a continuous operation.

[0014]

The present invention will be described in more detail with reference to the following examples. Example 1 40 g (2.0 mol) of HF and 592.5 g of R-133a were placed in a vacuum packed SUS distillation column (diameter: 25 mm, packing: McMahon, effective packing height: 1500 mm).
(5.0 mol), distillation was started at full reflux, and the still temperature was gradually increased. The reflux liquid was sampled when the overhead pressure was 1.5 kg / cm ² G and the overhead temperature was 19 ° C. Analysis of this sample showed a HF / R-133a molar ratio of 58/42.

Again, the still temperature was raised at the total reflux, and the refluxed liquid was sampled when the pressure at the top reached 4.0 kg / cm ² G and the temperature at the top reached 40 ° C. Analysis of this sample showed a HF / R-133a molar ratio of 55/45. From these analysis results, it is clear that HF having a boiling point higher than that of R-133a (normal pressure boiling point of R-133a <7 ° C. <normal pressure boiling point of HF of 19 ° C.) is concentrated at the top of the column. HF was found to form an azeotrope.

Example 2 Vacuum SUS vapor-liquid equilibrium measuring apparatus (capacity: 75 ml)
A mixture (60 g) of R-133a and HF having the same composition as the liquid (reflux) sampled in Example 1 was placed in
The entire apparatus was heated so that the pressure of the system was 1.5 kg / cm ² G. After the state of the system was equilibrated, the gas phase and the liquid phase were sampled. Similarly, the gas-liquid equilibrium was measured by changing the pressure of the system. The sampled gas phase and liquid phase HF concentrations are shown in Table 1 below (thus R-133a is the balance):

[0017]

Table 1 Sampling Liquid phase composition Gas phase composition Pressure Temperature mol% mol% Kg / cm ² G ℃ 158 59 1.5 20 25 55 55 4.0 41 As is clear from these results, gas phase and liquid The composition of the phases was approximately equal within experimental error, indicating that HF and R-133a formed an azeotrope.

Example 3 HF and R-133a were charged and mixed in a vacuum fluorinated resin container at a molar ratio of 60/40, respectively, and the mixture was allowed to stand still at a temperature of 0 ° C. Separated. In this state, the molar ratio between HF and R-133a in the lower liquid phase was measured. As a result, the molar ratio of HF / R-133a was 3
0/70. The molar ratio between HF and R-133a in the upper liquid phase was 84/16.

Examples 4 to 6 Experiments and measurements were performed in the same manner as in Example 3 except that the phase separation temperature was changed. Table 2 shows the conditions and the results of the lower liquid phase together with Example 3.

[0020]

Table 2 Example Phase separation temperature Lower liquid phase composition (molar ratio) ° C HF / R-133a 30 30/704 4-5 20/80 5 -10 10/90 65 50/50

However, the composition before phase separation is HF and R-133a
Of 60/40. As can be seen from Examples 3 to 6, the lower liquid phase HF / R-
133a is significantly reduced.

Example 7 HF was added to a vacuumed fluororesin 1000 ml container.
0 g (7.5 mol) and 592.5 g (5.
0 mol) Charged and cooled to -20 ° C. As the cooling progressed, HF and R-133a became in a phase separated state, and the entire lower liquid phase was recovered. In the lower liquid phase, 1 g of HF (0.
53 mol) and 435.5 g (3.68 mol) of R-133a.
l) included. Therefore, the molar ratio of HF / R-133a is 1.34 / 98.66, which indicates that the ratio is greatly shifted to the R-133a side from the azeotropic composition of the binary system of HF and R-133a.

Further, 400 g of the recovered lower liquid phase was charged into the same SUS distillation column as that used in Example 1, and the still temperature was gradually increased at all reflux conditions, and the top pressure was 1.5 kg / kg. Sampling was performed when the temperature reached 20 ° C. and cm ² G (2 g). When the sample was analyzed, H
The molar ratio of F / R-133a was 60.8 / 39.2. Again, the still temperature was increased in the total reflux state, the overhead pressure was 4.0 kg / cm ² G, the overhead temperature was 41 ° C., and sampling was performed at this time (2 g). When the sample was analyzed, the molar ratio of HF / R-133a was 56.6 / 43.4.

The pressure was returned to 1.5 kg / cm ² G again to stabilize the distillation column at full reflux. After the stabilization, the effluent from the top was gradually extracted, and the temperature of the top gradually increased. When the temperature of the top became the same as the still temperature, heating was stopped. The amount of liquid withdrawn from the top is about 20 g (including sampling on the way), and about 10 ppm of HF from still
About 380 g of R-133a containing was obtained.

Example 8 HF was placed in a vacuum-applied 1000 ml container made of fluororesin.
0 g (7.5 mol) and 592.5 g (5.
0 mol) Charged and cooled to -20 ° C. As the cooling progressed, HF and R-133a became in a phase separated state, and the entire upper liquid phase was recovered. 149 g of HF was contained in the upper liquid phase.
(7.45 mol) and 157 g (1.32) of R-133a.
mol) was included. Therefore, the molar ratio of HF / R-133a is 84.95 / 15.05, and HF and R-13
It can be seen that the ratio is greatly shifted to the HF side from the azeotropic composition of the binary system of 3a.

Further, 300 g of the recovered upper liquid phase was charged into the same SUS distillation column as in Example 1, and the still temperature was gradually increased in the total reflux state, and the overhead pressure was 1.5 kg / cm.
Sampling was performed when the temperature at the top of the column reached 20 ° C. at ² G (2 g). Analysis of the sample showed that HF / R-13
The molar ratio of 3a was 59.5 / 40.5. Again, the still temperature was raised in the total reflux state, and the overhead pressure was 4.0 kg / cm.
^{At 2} G, the top temperature became 40 ° C., and sampling was performed at this time (2 g). When the sample was analyzed, HF / R
The molar ratio of -133a was 57.5 / 42.5.

The pressure was returned to 1.5 kg / cm ² G again, and the distillation column was stabilized at the total reflux. After the stabilization, the effluent from the top was gradually extracted, and the temperature of the top gradually increased. When the temperature of the top became the same as the still temperature, heating was stopped. The amount of liquid withdrawn from the top of the column was about 240 g (including sampling on the way), and R-133a was obtained from the still.
Of HF containing only traces of HF was obtained.

[Brief description of the drawings]

FIG. 1 shows a flow sheet of an example of an apparatus for purifying 1,1,1-trifluoro-2-chloroethane used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Liquid separation apparatus, 3 ... Distillation apparatus, 5 ... Distillate, 7 ... Reflux, 9 ... Boiler, 11 ... Cooler, 23 ... Distillation apparatus, 25
... distillate, 27 ... reflux, 29 ... can, 31 ... cooler.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Satoshi Koyama 1-1, Nishiichitsuya, Settsu-shi, Osaka Daikin Industries, Ltd. Yodogawa Works (56) References JP-A-5-78267 (JP, A) JP JP-A-5-255144 (JP, A) JP-A-6-135867 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 17/38 C01B 7/19 C07C 17/383 C07C 19 / 08 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (6)

(57) [Claims] 1. A mixture comprising at least hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane is cooled to 7 ° C. or lower, and the upper liquid phase rich in hydrogen fluoride is mixed with 1,1,1-trifluoroethane. Separating a lower liquid phase rich in fluoro-2-chloroethane and recovering 1,1,1-trifluoro-2-chloroethane containing less hydrogen fluoride from the lower liquid phase; A method for purifying fluoro-2-chloroethane. 2. A method comprising distilling a mixture comprising at least hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane to form hydrogen fluoride and 1,1,1-trifluoro-2. A method for purifying 1,1,1-trifluoro-2-chloroethane, characterized in that the chloroethane is removed as an azeotrope. 3. A mixture comprising at least hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane at 7 ° C.
Cooled below, the upper liquid phase rich in hydrogen fluoride and 1,1,1-
Hydrogen fluoride is separated into hydrogen fluoride and 1,1,1-trifluoro-2 by separating into a lower liquid phase rich in trifluoro-2-chloroethane and distilling the lower liquid phase with less hydrogen fluoride.
A method for purifying 1,1,1-trifluoro-2-chloroethane, characterized in that the chloroethane is removed as an azeotrope. 4. The method according to claim 4, wherein an azeotropic mixture of hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane obtained by distilling the lower liquid phase is returned to the cooling phase separation step. A method for purifying 1,1-trifluoro-2-chloroethane. 5. Cooling a mixture comprising hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane to below 7 ° C., wherein the upper liquid phase rich in hydrogen fluoride and 1,1,1- Trifluoro-
Separating the lower liquid phase enriched in 2-chloroethane, distilling the upper liquid phase to convert 1,1,1-trifluoro-2-chloroethane to 1,1,1-trifluoro-2-
A first distillation step of recovering an azeotrope of chloroethane and hydrogen fluoride, and distilling the lower liquid phase to convert hydrogen fluoride into hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane; A second distillation step of recovering a boiling mixture, and a step of recycling an azeotrope obtained by both distillation steps to a cooling step, wherein the first distillation step is substantially free of hydrogen fluoride. A method for purifying 1,1,1-trifluoro-2-chloroethane, comprising obtaining 1,1-trifluoro-2-chloroethane. 6. A mixture comprising at least hydrogen fluoride and 1,1,1-trifluoro-2-chloroethane at 5 ° C.
The cooling method according to claim 1, 3, 4, or 5, wherein
A method for purifying 1-trifluoro-2-chloroethane.