JPH04316525A - Purification of 1,1,1,2-tetrafluoroethane - Google Patents

Abstract

PURPOSE:To purify the title compound containing 2-chloro-1,1difluoroethylene of impurity in high purity by subjecting the title compound to extractive distillation by using trichloroethylene or 1,1-dichloro-2,2,2-trifluoroethane as an extractant. CONSTITUTION:2-Chloro-1,1-difluoroethylene, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 2-chloro-1,1,2,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane contained as impurities in 1,1,1,2-tetrafluoroethane are removed by extractive distillation by using trichloroethylene or 1,1-dichloro-2,2,2-trifluoroethane as an extractant to purify 1,1,1,2-tetrafluoroethane. Impurities having difficulty in removal are readily eliminated and also other high-boiling impurities are easily removed.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to the purification of 1,1,1,2-tetrafluoroethane, more specifically to trichlorethylene or 1,1-dichloro-2,2,2-tetrafluoroethane.
-1,1 by extractive distillation method using trifluoroethane
, 1,2-tetrafluoroethane.

0002

[Prior Art] Substances that do not destroy the ozone layer in the stratosphere, 1
, 1,1,2-tetrafluoroethane (hereinafter referred to as HFC-
CFC-134a) has been attracting attention as a substitute for CFC-12, which has similar physical properties, and is expected to be used as a refrigerant in car air conditioners, refrigerators, etc.

2-chloro-1,1-difluoroethane (hereinafter referred to as H
CFC-1122) is harmful to humans and must be separated. Distillation is generally considered as a method for separating a mixture into several components, but the inventors have found that the specific volatility of HCFC-1122 relative to HFC-134a is close to 1, for example 4 kg/cm2 G. In cases in the vicinity, the value is 1.2, so it cannot be said that a method of separation using only a simple distillation method is necessarily a good idea.

HCFC-1122 in HFC-134a
Although adsorption methods have been shown to be effective in removing , there are problems such as small adsorption capacity and complicated operations.

[0005]

Problem to be Solved by the Invention: As mentioned above, HCFC-11 is difficult to separate by distillation and adsorption, which are common purification methods.
The purpose of the present invention is to provide a method for purifying HFC-134a that removes HFC-134a and the like.

[0006]

[Means for solving the problem] The above problem is solved by HCFC-1
This problem can be solved by adding an extractant when distilling HFC-134a containing 122 to significantly reduce the specific volatility of HCFC-1122 relative to HFC-134a. The extractant used in the present invention is trichlorethylene or 1,1
-dichloro-2,2,2-trifluoroethane.

According to the study results of the present inventors, HFC-13
The specific volatility of HCFC-1122 relative to 4a depends on the concentration of trichlorethylene, and HCFC-1122 is treated as a high-boiling component. In addition, at this time, 1,2-dichloro-
1,1,2,2-tetrafluoroethane (hereinafter referred to as CFC)
-114), 2-chloro-1,1,2,2-tetrafluoroethane (hereinafter referred to as HCFC-124),
2-chloro-1,1,1-trifluoroethane (hereinafter referred to as
It has been found that the specific volatility of HCFC-133a) relative to HFC-134a is also lower, and that it is also useful for removing other high-boiling impurities.

The concentration of trichlorethylene is 15 mol
% to 98 mol%, but the number of plates in the distillation column,
When considering the column diameter and reflux ratio, 50 to 90 mol% is optimal. Note that when trichlorethylene is used as a raw material, its use is very beneficial when considering the entire process.

Similar results were also obtained in the case of 1,1-dichloro-2,2,2-trifluoroethane (hereinafter referred to as HCFC-123). In addition, HCFC-11
Since the isomers of 22, CFC-114 and HCFC-124 have similar boiling points and properties and exhibit the same behavior, they can be separated using the extractant of the present invention.

0010

【Example】

[Example 1] Partially purified HFC-134a was charged into a stainless steel Osmer-type vapor-liquid equilibrium measuring device, and a polar solvent such as trichlorethylene or HCFC-123 was added thereto to measure the vapor-liquid equilibrium relationship. A series of test results are shown in Table 1. HFC- in any polar solvent
The specific volatility of HCFC-1122 relative to 134a was seen to decrease, but trichlorethylene and H
In the case of FC-123, the decrease in specific volatility is large.

[0011]

[Table 1]

[Example 2] Partially purified HFC-134a was charged into a stainless steel Othmer-type vapor-liquid equilibrium measuring device, trichlorethylene was added thereto to a predetermined concentration, and the vapor-liquid equilibrium relationship was measured. Table 2 shows the test results.
Shown below.

[0013]

[Table 2]

When the trichlorethylene concentration was 60 mol %, the specific volatility of HFC-1122 to HFC-134a decreased from 1.2 when no addition was made to 0.32. C.F.C.
-114's specific volatility decreased from 0.81 to 0.25, H
The specific volatility of CFC-124 decreased from 0.69 to 0.41, and the specific volatility of HCFC-133a decreased from 0.4 to 0.21.
It dropped to .

[Example 3] In a stainless steel packed column with a diameter of 40φ and 40 theoretical plates, the pressure was 2 kg/cm2.
2 crude HFC-134a was placed at the 35th stage from the top of the column.
Trichlorethylene was supplied at 2400 g/Hr to the 10th stage position from the top of the column, and distilled at 180 g/Hr from the top at a reflux ratio of 3. The results are shown in Table 3, with HFC-1122 in the top distillate being 6 ppm, CF
C-114 is 8ppm, HCFC-124 is 10ppm
m, HCFC-133a is 25 ppm, purity 99.
996% HFC-134a was obtained.

[0016]

[Table 3]

[Example 4] In a stainless steel packed column with a diameter of 40φ and 40 theoretical plates, the pressure was 2 kg/cm2.
G, crude HFC-134a was placed at the 35th stage from the top of the column.
00g/Hr, HCFC-123 was supplied at 3240g/Hr to the 10th stage position from the top of the column, and distilled from the top at 90g/Hr at a reflux ratio of 4. The results are shown in Table 4, HFC-1122 in the tower top distillate was 8 ppm, CFC-
114 is 20ppm, HCFC-124 is 10ppm
, HCFC-133a is 50 ppm, purity 99.9
91% HFC-134a was obtained.

[0018]

[Table 4]

[0019]

[Effect of the invention] As stated above, the HF in the present invention
The C-134a purification method eliminates HC, which was previously difficult to remove.
FC-1122 with trichlorethylene or HCFC-
This is an epoch-making method that facilitates removal by extractive distillation using 123 and also facilitates the removal of other high-boiling impurities.

Claims (2)

[Claims] Claim 1: 2-chloro-1,1-difluoroethylene, an impurity in 1,1,1,2-tetrafluoroethane, is replaced with trichlorethylene or 1,1-dichloro-
A purification method characterized by removal by extractive distillation using 2,2,2-trifluoroethane as an extractant. 2. 2-chloro-1,1-difluoroethylene, 1,2-dichloro-1,1,2,2-tetrafluoroethane, which is an impurity in 1,1,1,2-tetrafluoroethane; At least one selected from 2-chloro-1,1,2,2-tetrafluoroethane and 2-chloro-1,1,1-trifluoroethane is combined with trichlorethylene or 1,1-dichloro-2,2, A purification method characterized by removal by extractive distillation using 2-trifluoroethane as an extractant.