WO2018090507A1 - Method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene - Google Patents

Abstract

Provided is an efficient method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene, having a green and safe operation process. The method uses a halogenated hydrocarbon, an alcohol, an ether, a nitrile, a ketone, an amide or a sulfoxide with a boiling point within the range of 50ºC - 250ºC as an extraction agent, and a mixture of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene is separated by extraction and rectification, wherein the mass ratio of the extraction agent to the mixture of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene is 4:1 - 10:1.

Description

Method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene Technical field

The present invention relates to a process for the separation of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene, and more particularly to the extraction of 2-chloro-1 by extractive distillation. A method of separating 2-chloro-1,1,1,2-tetrafluoropropane from a mixture of 1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene.

Background technique

2-Chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) is a raw material for the synthesis of 2,3,3,3-tetrafluoropropene (HFO-1234yf). HFO-1234yf, which has zero ozone depletion potential and a greenhouse effect potential of 4, has excellent environmental performance and is considered to be an ideal substitute for 1,1,1,2-tetrafluoroethane (HFC-134a).

2-Chloro-1,1,1,2-tetrafluoropropane is mainly prepared by liquid phase fluorination of hydrogen fluoride and 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf), which is supported by the catalyst and the reaction itself. Characteristic effect, the reaction product is a mixture of HCFO-1233xf and HCFC-244bb, and the composition is usually 85-99% (mass%) of HCFC-244bb and 1%-15% of HCFO-1233xf. HCFO-1233xf (boiling point 12.1 ° C) is close to the boiling point of HCFC-244bb (boiling point 13.2 ° C), and it is difficult to separate the two by conventional rectification techniques. However, as a raw material for the synthesis of HFO-1234yf, when HCFC-244bb contains olefin HCFO-1233xf, it will lead to the rapid carbon deposition deactivation of HFC-1234yf catalyst for dehydrochlorination of HCFC-244bb, reducing the yield of product HFO-1234yf and Product purity. Therefore, it is necessary to effectively separate HCFC-244bb and HCFO-1233xf to meet the raw material requirements for preparation of HFO-1234yf.

Chinese patent CN102933535A reports a method for enriching HCFC-244bb in a column reactor by adding HF to a mixture of HCFO-1233xf and HCFC-244bb to form a ternary azeotrope. Since the method obtained ternary azeotropy of HF, HCFO-1233xf and HCFC-244bb at the top of the column (the concentration of HCFC-244b in the azeotrope is about 10.0-18.0% by weight), HCFO-1233xf is not truly realized. The effective separation of HCFC-244bb, HCFC-244bb exists in both the top of the tower and the tower. In addition, introduced The azeotrope HF is a highly corrosive medium that increases the risk to equipment, operators and the environment.

Summary of the invention

The object of the present invention is to overcome the deficiencies in the prior art and to provide a green safe and efficient operation process of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-tride. A method of separating fluoropropene.

For the purpose of the present invention, the present invention separates 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene by extractive rectification in the presence of an extractant. a mixture wherein the extracting agent is a halogenated hydrocarbon, an alcohol, an ether, a nitrile, a ketone, an amide or a sulfoxide having a boiling point of from 50 ° C to 250 ° C, 2-chloro-1,1,1,2-tetra The mass ratio of the mixture of fluoropropane and 2-chloro-3,3,3-trifluoropropene to the extractant is 1:4 to 10. The extracting agent of the present invention is specifically selected from the group consisting of 1,1,2-trichloroethane, chlorobenzene, isoamyl alcohol, ethylene glycol monomethyl ether, dibutyl ether, ethylene glycol diethyl ether, phenylethyl ether, acetonitrile, and 4- Methyl-2-pentanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

The principle of extractive rectification is to significantly change the relative volatility of HCFC-244bb and HCFO-1233xf by adding the extractant, thereby separating the two. Here, the relative volatility (α) of HCFC-244bb relative to HCFO-1233xf is defined as follows:

To determine the relative volatility α of HCFC-244bb relative to HCFO-1233xf after the addition of the extractant. The inventors used a 300 ml stainless steel reactor with a gas phase and liquid phase sampling valve. A certain mass of extractant and a mixture of HCFC-244bb/HCFO-1233xf (wherein the mass percentage of HCFC-244bb was 90%) was added to the autoclave. The reaction kettle was immersed in a 50 ° C constant temperature oil bath, and the materials were magnetically stirred to mix the materials thoroughly. The materials in the reaction kettle were equilibrated in the gas-liquid phase, and the gas phase and liquid phase samples were taken. The composition of each phase was determined by gas chromatography. . Defined according to the above relative volatility Formula, calculate the relative volatility α value of each experiment, the relevant experimental results are shown in Table 1.

Table 1 α value after adding extractant

Note: Solute ratio = extractant mass / quality of HCFC-244bb and HCFO-1233xf mixture

It can be seen from Table 1 that the addition of halogenated hydrocarbons, alcohols, ethers, nitriles, ketones, amides or sulfoxide extractants having a boiling point in the range of 50 ° C to 250 ° C changes the HCFC-244bb relative to The relative volatility of HCFO-1233xf, α becomes significantly greater than 1 when no extractant is added, and the relatively less volatile HCFC-244bb becomes more volatile, that is, it can be obtained by extractive distillation from the top of the column. HCFC-244bb product.

From the extractants tested in Table 1, it is understood that the preferred extractants are amides and ethers, and a particularly preferred extractant is N,N-dimethylformamide or ethylene glycol diethyl ether. Further, the extracting agent may be used singly or in combination of two or more.

In order to better verify the effect of the extractant of the present invention, the HCFC-244bb+HCFO-1233xf y-x pattern at 50 ° C was determined (see Figures 2 and 3). Figure 2 shows that the relative volatility of HCFC-244bb relative to HCFO-1233xf is close to 1 when no extractant is added, and HCFC-244bb is a relatively less volatile component. Figure 3 shows that when the extractant N,N-dimethylformamide (solute ratio 5) is added, the relative volatility of HCFC-244bb relative to HCFO-1233xf is reversed and becomes significantly greater than 1, ie, the extractant The relatively less volatile HCFC-244bb becomes a relatively volatile component. Therefore, it is possible to extract 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene by extractive rectification using the extracting agent of the present invention.

Using the extracting agent of the present invention, an extractive rectification operation can be carried out by using a conventional rectification column such as a plate column, a sieve column or a packed column. The design parameters and operating conditions of the rectification column vary with the choice of the extractant and the composition of the raw materials, and can be appropriately selected for the purpose of separation. When the extracting agent of the present invention is used for the extractive rectification operation, the two columns of the extractive rectification column and the extraction recovery column can be operated: (1) the HCFC-244bb/HCFO-1233xf mixture is fed from the middle of the extractive distillation column, and is extracted. The agent is fed from the upper part of the extractive distillation column, and the extractant in the extractive distillation column is used to extract HCFO-1233xf into the column kettle to form an extract enriched in HCFO-1233xf as a column distillation fraction, and enters the extraction recovery tower to extract the extract. The top of the distillation column is HCFC-244bb fraction, which is charged into the product storage tank as a product; (2) The HCFO-1233xf is separated from the extractant by the extraction recovery tower, HCFO-1233xf is obtained at the top of the column, and the extractant is obtained from the column to be recycled to the extract. Distillation tower.

A preferred method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene Using N,N-dimethylformamide (DMF) as the extractant, the extractive rectification operation comprises the following steps: (1) separating crude 2-chloro-1,1,1,2-tetrafluoropropane as a raw material for separation , wherein the mass percentage of 2-chloro-1,1,1,2-tetrafluoropropane is 85% to 99%, and the mass percentage of 2-chloro-3,3,3-trifluoropropene is 1% to 15%. %. The extractant is fed from the upper part of the extractive rectification column, and the raw material is fed from the middle of the extractive rectification column, the mass ratio of the raw material to the extracting agent is 1:4-10, and the extractive distillation column top fraction is divided into 2-chloro-1. 1,1,2-tetrafluoropropane, the column is divided into 2-chloro-3,3,3-trifluoropropene and an extractant, and enters an extraction recovery column. Operating conditions of the extractive distillation column: the operating pressure of the column is 100-200 kPa, the temperature at the top of the column is 12-35 ° C, the temperature of the column is 130-180 ° C, and the reflux ratio is 0.5-5; (2) Extraction and recovery tower top The fraction is 2-chloro-3,3,3-trifluoropropene, and the column is divided into an extractant and recycled to the extractive distillation column. The operating conditions of the extraction recovery column are: the operating pressure of the column is 100-200 kPa, the temperature at the top of the column is 12-35 ° C, the temperature of the column is 150-180 ° C, and the reflux ratio is 5-20.

The invention utilizes the addition of the selected extractant to significantly change the relative volatility of HCFC-244bb and HCFO-1233xf, and separates the HCFC-244bb/HCFO-1233xf mixture by using two rectification columns, an extractive rectification column and an extraction recovery tower. HCFC-244bb and HCFO-1233xf can be efficiently separated. The whole purification process adopts the industrially mature rectification technology, and the operation process is simple and easy to realize. At the same time, the extractant used is a conventional organic solvent without high corrosivity, and the separation process is green and safe.

DRAWINGS

Figure 1 is a flow chart showing the separation process of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene. The meanings of the symbols in Figure 1 are as follows: T1 - extractive distillation column; T2 - extraction recovery column; - 1 - mixture of HCFC-244bb and HCFO-1233xf; 2 - T1 overhead; 3 - T1 column distillation 4 - T2 overhead distillate; 5 - T2 tower distillate.

Figure 2 is a y-x diagram of HCFC-244bb(1)-HCFO-1233xf(2).

Figure 3 is the y-x of HCFC-244bb(1)-HCFO-1233xf(2) when N,N-dimethylformamide is used as the extractant. Figure.

detailed description

The invention is further described in detail below with reference to the examples, but without limiting the scope of the invention.

Example 1

The extractive distillation column T1 and the extraction and recovery tower T2 are packed towers with a diameter of Φ25 mm, a Φ3×3θ ring stainless steel filler inside, and a packing layer height of 4 m. The rectified material 1 is a crude product of synthetic 2-chloro-1,1,1,2-tetrafluoropropane, wherein the mass percentage of HCFC-244bb is 90%, and the mass percentage of HCFO-1233xf is 10%. Feed 1 is fed from the middle of the extractive distillation column T1 at a flow rate of 100 g/h, and T2 column distillate 5 (ie, a cyclic extractant, N,N-dimethylformamide) is fed from the upper portion of the T1 column. The flow rate is 400 g/h, the T1 overhead product 2 is the HCFC-244bb product, the T1 column distillate 3 is the HCFO-1233xf and the extractant, and enters the T2 column of the extraction recovery column. The T2 overhead product 4 is a HCFO-1233xf product, and the T2 overhead distillation product 5 is an extractant and is returned to T1. The operating conditions of the tower are shown in Table 1, and the composition of the logistics is shown in Table 2.

Table 1 operating conditions in the column of Example 1

Distillation tower	T1	T2
Operating pressure / kPa (A)	100	200
Tower top temperature / °C	13.3	33.4
Tower kettle temperature / °C	139	179.1
Reflux ratio	0.5	5

Table 2 The composition of the stream in Example 1

Example 2

The operation procedure of Example 2 is similar to that of Example 1, except that the operating parameters of the distillation columns T1 and T2 are different, the operating parameters are shown in Table 3, and the logistics composition of Example 2 is shown in Table 4.

Table 3 column operating conditions in Example 2

Distillation tower	T1	T2
Operating pressure / kPa (A)	200	100
Tower top temperature / °C	34.1	12.2
Tower kettle temperature / °C	168	152.2
Reflux ratio	5	20

Table 4 The composition of the stream in Example 2

Example 3

The operation procedure of Example 3 is similar to that of Example 1, except that the composition of the material (1) is changed to HCFC-244bb 85%, HCFO-1233xf 5%, and the extractant is adjusted to 1000 g/h. The operating parameters are shown in Table 5. The composition of the stream of Example 3 is shown in Table 6.

Table 5 operating conditions of the column in Example 3

Distillation tower	T1	T2
Operating pressure / kPa (A)	200	100
Tower top temperature / °C	34.1	12.1
Tower kettle temperature / °C	174.4	152.2
Reflux ratio	5	20

Table 6 Logistics composition in Example 3

Example 4

The operation procedure of Example 4 is similar to that of Example 1, except that the composition of the material (1) becomes HCFC-244bb 99%, HCFO-1233xf 1%, the operating parameters are shown in Table 7, and the flow composition of Example 4 is shown in the table. 8.

Table 7 column operating conditions in Example 4

Distillation tower	T1	T2
Operating pressure / kPa (A)	200	100
Tower top temperature / °C	34.1	12.1
Tower kettle temperature / °C	168.1	152.2
Reflux ratio	1	10

Table 8 The composition of the stream in Example 4

Industrial applicability

The invention utilizes the addition of the selected extractant to significantly change the relative volatility of HCFC-244bb and HCFO-1233xf, and separates the HCFC-244bb/HCFO-1233xf mixture by using two rectification columns, an extractive rectification column and an extraction recovery tower. HCFC-244bb and HCFO-1233xf can be efficiently separated. The whole purification process adopts the industrially mature rectification technology, and the operation process is simple and easy to realize. At the same time, the extractant used is a conventional organic solvent without high corrosivity, and the separation process is green and safe.

Claims (4)

1. A method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene, characterized in that it is separated by extractive distillation in the presence of an extractant 2 a mixture of -chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene, wherein the extracting agent is a halogenated hydrocarbon having an boiling point of from 50 ° C to 250 ° C, an alcohol, Ethers, nitriles, ketones, amides or sulfoxides, mixtures of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene with extractants The mass ratio is 1:4 to 10.
2. The method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene according to claim 1, wherein the extracting agent is 1, 1,2-trichloroethane, chlorobenzene, isoamyl alcohol, ethylene glycol monomethyl ether, dibutyl ether, ethylene glycol diethyl ether, phenyl ether, acetonitrile, 4-methyl-2-pentanone, N, N - dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.
3. The method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene according to claim 1, wherein the extracting agent is N , N-dimethylformamide or ethylene glycol diethyl ether.
4. A method for separating 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene according to claim 1, wherein said extractive distillation comprises The following steps: (1) The crude product of 2-chloro-1,1,1,2-tetrafluoropropane is used as a separation raw material, wherein the mass percentage of 2-chloro-1,1,1,2-tetrafluoropropane is 85%～99%, 2-chloro-3,3,3-trifluoropropene is 1%-15% by mass, N,N-dimethylformamide is used as extractant; extractant is extracted from extract The upper part of the distillation column is fed, and the raw material is fed from the middle of the extractive distillation column, the mass ratio of the raw material to the extracting agent is 1:4 to 10, and the extractive distillation column top fraction is divided into 2-chloro-1, 1, 1, 2 -tetrafluoropropane, the column is divided into 2-chloro-3,3,3-trifluoropropene and an extractant, and enters the extraction and recovery tower; the operating conditions of the extractive distillation column: the operating pressure of the column is 100-200 kPa, the top of the column The temperature is 12-35 ° C, the temperature of the column is 130-180 ° C, and the reflux ratio is 0.5-5; (2) The extraction and recovery column is divided into 2-chloro-3,3,3-trifluoropropene, and the column is divided into fractions. For the extractant, it is recycled to the extractive distillation column; the operating conditions of the extraction and recovery tower: the operating pressure of the column is 100-200 kPa, the temperature of the top of the tower Is 12 ~ 35 ℃, tower bottom temperature is 150 ~ 180 ℃, a reflux ratio of from 5 to 20.

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