Method for separating bis (trifluoromethyl) sulfide and 1, 1, 1, 2-tetrafluoroethane

Abstract

The invention provides a method for separating bis (trifluoromethyl) sulfide and 1, 1, 1, 2-tetrafluoroethane, which is characterized in that the 1, 1, 1, 2-tetrafluoroethane and the bis (trifluoromethyl) sulfide are separated from a mixture of the 1, 1, 1, 2-tetrafluoroethane and the bis (trifluoromethyl) sulfide through extractive distillation, and the 1, 1, 1, 2-tetrafluoroethane and the bis (trifluoromethyl) sulfide are separated from the mixture of the 1, 1, 1, 2-tetrafluoroethane and the bis (trifluoromethyl) sulfide. An extracting agent used in the extractive distillation is one or a combination of more than one of a ketone compound and an anhydride compound. According to the method, the characteristic that the relative volatility of 1, 1, 1, 2-tetrafluoroethane and bis (trifluoromethyl) sulfide can be obviously changed by adding the selected extracting agent is utilized, and the mixture of 1, 1, 1, 2-tetrafluoroethane and bis (trifluoromethyl) sulfide is separated by adopting two devices, namely the extractive distillation tower and the extracting agent recovery tower, so that 1, 1, 1, 2-tetrafluoroethane and bis (trifluoromethyl) sulfide can be efficiently separated out; the purity of the bis (trifluoromethyl) sulfide and the purity of the 1, 1, 1, 2-tetrafluoroethane are both 99.5 wt% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, relates to polyfluoroalkanes, and specifically relates to a method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane. Background Art

[0002] As a fluorinated sulfide, bis(trifluoromethyl) sulfide has the properties of high dielectric strength, low boiling point, and low greenhouse effect potential (GWP), showing good environmental and safety characteristics. It has good application potential in electrical insulation and arc extinguishing media, and is expected to become a practical SF6 alternative gas. Bis(trifluoromethyl) sulfide (boiling point is -22℃) and 1,1,1,2-tetrafluoroethane (boiling point is -26.2℃) have similar boiling points and are easy to form azeotropes. Conventional separation technology is difficult to separate the two. Summary of the invention

[0003] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane, so as to solve the technical problem that the amount of extractant used in the separation method in the prior art needs to be further reduced.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane, wherein the method separates 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide from a mixture of 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide by extractive distillation, wherein the extractant used in the extractive distillation is one or a combination of more than one of ketone compounds and acid anhydride compounds.

[0006] The present invention also has the following technical features:

[0007] Preferably, the ketone compound is a ketone compound containing 3 to 6 carbon atoms.

[0008] More preferably, the ketone compound containing 3 to 6 carbon atoms is acetone, 3-pentanone, 3-hexanone, cyclopentanone or cyclohexanone.

[0009] Preferably, the acid anhydride compound is an acid anhydride compound containing 3 to 8 carbon atoms.

[0010] More preferably, the acid anhydride compound containing 3 to 8 carbon atoms is acetic anhydride, propionic anhydride, methacrylic anhydride or isobutyric anhydride.

[0011] Further preferably, the method comprises the following steps:

[0012] Step 1, using a mixture of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl)sulfide as a raw material, wherein the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 20-30%; adding the raw material and the extractant into an extractive distillation tower (T1), wherein the mass ratio of the extractant to the raw material is (12-14):1, the top fraction of the extractive distillation tower (T1) is a 1,1,1,2-tetrafluoroethane product, the bottom fraction of the extractive distillation tower (T1) is bis(trifluoromethyl)sulfide and the extractant, and the operating conditions of the extractive distillation tower (T1) are: a tower operating pressure of 170-180 kPa, a tower top temperature of -14.0--12.2° C., a bottom temperature of 69.4-163.2° C., and a reflux ratio of 0.1-3;

[0013] Step 2, the bottom fraction of the extractive distillation tower (T1) enters the extractant recovery tower (T2), the bottom fraction of the extractive distillation tower (T2) is the extractant, which is circulated to the extractive distillation tower (T1); the top fraction of the extractive distillation tower (T2) is bistrifluoromethyl sulfide; the operating conditions of the extractive distillation tower (T2) are: the operating pressure in the tower is 160-170 kPa, the top temperature is -10.5--9.1°C, the bottom temperature is 70.5-178.5°C, and the reflux ratio is 0.7-13.

[0014] More preferably, in step 1, the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 20% to 24%.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] (I) The present invention utilizes the characteristic that the addition of the selected extractant can significantly change the relative volatility of 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide, and uses two devices, namely an extractive distillation tower and an extractant recovery tower, to separate the mixture of 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide, so that 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide can be separated efficiently, and the purity of bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane is both above 99.5wt%.

[0017] (II) There is a strong hydrogen bonding effect between the carbonyl structure in the extractant used in the present invention and 1,1,1,2-tetrafluoroethane, which can improve the solubility of 1,1,1,2-tetrafluoroethane in the above-mentioned extractant, so that under the same conditions, the difficulty of 1,1,1,2-tetrafluoroethane escaping is lower, so as to achieve the purpose of significantly improving the relative volatility of the azeotropic system of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl) sulfide.

[0018] (III) The separation and purification process of the present invention adopts industrially mature distillation technology, the operation process is simple, and the extractant used is a conventional, non-corrosive organic solvent, and the purification process is green and safe. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a process flow chart for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane.

[0020] Figure 1 In the embodiment, T1 is an extractive distillation tower; T2 is an extractant recovery tower; the feed is a mixture of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl) sulfide; the overhead distillate of the extractive distillation tower is 1,1,1,2-tetrafluoroethane; the bottom effluent of the extractive distillation tower is an extractant containing bis(trifluoromethyl) sulfide; the overhead distillate of the extractant recovery tower is bis(trifluoromethyl) sulfide; and the bottom effluent of the extractant recovery tower is an extractant.

[0021] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0022] It should be noted that, unless otherwise specified, all equipment, raw materials and reagents in the present invention are those known in the prior art and can be obtained from commercial sources.

[0023] The extractant used in the present invention is a ketone compound or an acid anhydride compound with a boiling point in the range of 50 to 150°C.

[0024] The principle of extractive distillation is to change the relative volatility of bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane by adding the extractant, so that the relative volatility of 1,1,1,2-tetrafluoroethane relative to bis(trifluoromethyl) sulfide is greater than 1, thereby separating the two. Here, the relative volatility (α) of 1,1,1,2-tetrafluoroethane relative to bis(trifluoromethyl) sulfide is defined as follows:

[0025]

[0026] To determine the relative volatility α of 1,1,1,2-tetrafluoroethane relative to bis(trifluoromethyl)sulfide after the addition of the extractant. The inventors used a 300mL stainless steel reactor with gas and liquid sampling valves. 50g of extractant and 32g of 1,1,1,2-tetrafluoroethane / bis(trifluoromethyl)sulfide mixture (wherein the content of 1,1,1,2-tetrafluoroethane is 25wt%) were added to the reactor. The reactor was immersed in a -30°C constant temperature oil bath, and the materials were stirred magnetically to fully mix the materials. When the materials in the reactor reached gas-liquid equilibrium, gas phase samples and liquid phase samples were taken, and the composition content of each phase was determined by gas chromatography. According to the above relative volatility definition formula, the relative volatility α value of each experiment was calculated, and the relevant experimental results are shown in Table 1.

[0027] Table 1 α value after adding extractant

[0028] Extraction agent Boiling point / ℃ α none - 0.98 acetone 56.13 2.35 3-Pentanone 101 1.96 3-Hexanone 123 1.68 Cyclopentanone 130.5 1.86 Cyclohexanone 155 1.92 Acetic anhydride 141.2 2.04 Propionic anhydride 168 1.96 Methacrylic Anhydride 87 1.85 Isobutyric anhydride 182 1.60 Cyclopentanone and acetic anhydride in a mass ratio of 1:1 - 2.57 Acetone and methacrylic anhydride in a mass ratio of 3:1 - 2.68 Cyclohexanone and acetic anhydride in a mass ratio of 1:1 - 2.81

[0029] As shown in Table 1, after adding ketone compounds or acid anhydride compounds with a boiling point in the range of 50 to 150°C, the relative volatility of 1,1,1,2-tetrafluoroethane relative to bistrifluoromethyl sulfide is changed, and α changes from close to 1 when no extractant is added to significantly greater than 1, making the relatively non-volatile 1,1,1,2-tetrafluoroethane more volatile, that is, the 1,1,1,2-tetrafluoroethane product can be obtained from the top of the tower through extractive distillation.

[0030] From the extractants tested in Table 1, it can be seen that the preferred extractant is acetone. In addition, the above extractants can be used alone or in combination of two or more.

[0031] The invention uses quantum chemical calculation and gas-liquid equilibrium experimental verification to find that in the extractant, a strong hydrogen bond exists between the carbonyl structure and 1,1,1,2-tetrafluoroethane, which can improve the solubility of 1,1,1,2-tetrafluoroethane in the extractant, thereby making it easier for 1,1,1,2-tetrafluoroethane to escape under the same conditions, thereby achieving the purpose of significantly improving the relative volatility of the azeotropic system of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl) sulfide.

[0032] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0033] Embodiment 1:

[0034] This embodiment provides a method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane. The method separates 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide from a mixture of 1,1,1,2-tetrafluoroethane and bistrifluoromethyl sulfide by extractive distillation, and the extractant used in the extractive distillation is acetic anhydride.

[0035] like Figure 1 As shown, the method comprises the following steps:

[0036] Step 1, using a mixture of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl)sulfide as a raw material, wherein the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 24%; adding the raw material and the extractant into an extractive distillation tower T1, the flow rate of the raw material is 146 g / h, the mass ratio of the extractant to the raw material is 13:1, the top fraction of the extractive distillation tower T1 is a 1,1,1,2-tetrafluoroethane product, the bottom fraction of the extractive distillation tower T1 is bis(trifluoromethyl)sulfide and the extractant, and the operating conditions of the extractive distillation tower T1 are shown in Table 2.

[0037] In this embodiment, the extractive distillation tower T1 is a packed tower with a tower diameter of Φ25 mm, and is filled with Φ3*3θ ring stainless steel packing, and the height of the packing layer is 0.8 m.

[0038] Step 2: The bottom fraction of the extractive distillation tower T1 enters the extractant recovery tower T2; the bottom fraction of the extractant recovery tower T2 is the extractant, which is circulated to the extractive distillation tower T1; the top fraction of the extractant recovery tower T2 is bistrifluoromethyl sulfide; the operating conditions of the extractant recovery tower T2 are shown in Table 2.

[0039] Table 2 Tower operating conditions in Example 1

[0040] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 147.5 Tower temperature / ℃ 157.66 Reflux ratio 2.6 Reflux ratio 2.7

[0041] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.8 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.5 wt %.

[0042] Embodiment 2:

[0043] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 1, except that:

[0044] In this embodiment, the extractant used in the extractive distillation is cyclopentanone:

[0045] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 3.

[0046] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 3.

[0047] Table 3 Tower operating conditions in Example 2

[0048] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 128.1 Tower temperature / ℃ 157.9 Reflux ratio 0.1 Reflux ratio 13

[0049] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.6 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.6 wt %.

[0050] Embodiment 3:

[0051] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 1, except that:

[0052] In this embodiment, the extractant used in the extractive distillation is acetone:

[0053] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 4.

[0054] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 4.

[0055] Table 4 Tower operating conditions in Example 3

[0056] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 70.1 Tower temperature / ℃ 70.5 Reflux ratio 3.0 Reflux ratio 10

[0057] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.6 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.5 wt %.

[0058] Embodiment 4:

[0059] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 2, except that:

[0060] In this embodiment, the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 20%.

[0061] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 5.

[0062] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 5.

[0063] Table 5 Tower operating conditions in Example 4

[0064] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 115.8 Tower temperature / ℃ 161.4 Reflux ratio 0.5 Reflux ratio 1.1

[0065] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.7 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.6 wt %.

[0066] Embodiment 5:

[0067] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 1, except that:

[0068] In this embodiment, the extractant used in the extractive distillation is a mixture of cyclopentanone and acetic anhydride in a mass ratio of 1:1.

[0069] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 6.

[0070] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 6.

[0071] Table 6 Tower operating conditions in Example 5

[0072] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 155.2 Tower temperature / ℃ 167.5 Reflux ratio 3.0 Reflux ratio 0.7

[0073] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.8 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.7 wt %.

[0074] Embodiment 6:

[0075] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 4, except that:

[0076] In this embodiment, the extractant used in the extractive distillation is a mixture of acetone and methacrylic anhydride in a mass ratio of 3:1.

[0077] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 7.

[0078] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 7.

[0079] Table 7 Tower operating conditions in Example 6

[0080] Extractive distillation tower T1 Extractant recovery tower T2 Operating pressure / kPa(A) 180 Operating pressure / kPa(A) 170 Tower top temperature / ℃ -12.2 Tower top temperature / ℃ -9.1 Tower temperature / ℃ 69.4 Tower temperature / ℃ 79.3 Reflux ratio 1.5 Reflux ratio 5.5

[0081] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.8 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.8 wt %.

[0082] Embodiment 7:

[0083] This example provides a method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane. The method is basically the same as that in Example 4, except that:

[0084] In this embodiment, the extractant used in the extractive distillation is a mixture of cyclohexanone and acetic anhydride in a mass ratio of 1:1.

[0085] In this embodiment, the operating conditions of the extractive distillation tower T1 in step 1 are shown in Table 8.

[0086] In this embodiment, the operating conditions of the extractant recovery tower T2 in step 2 are shown in Table 8.

[0087] Table 8 Tower operating conditions in Example 7

[0088]

[0089]

[0090] In this embodiment, the purity of 1,1,1,2-tetrafluoroethane in the overhead product of the extractive distillation tower T1 was 99.9 wt % as determined by gas chromatography, and the purity of bistrifluoromethyl sulfide in the overhead product of the extractant recovery tower T2 was 99.9 wt %.

Claims

1. A method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane, wherein the method separates 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl) sulfide from a mixture of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl) sulfide by extractive distillation, characterized in that: The extractant used in the extractive distillation is one or a combination of more than one of ketone compounds and acid anhydride compounds.

2. The method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane according to claim 1, characterized in that: The ketone compound is a ketone compound containing 3 to 6 carbon atoms.

3. The method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane according to claim 2, characterized in that: The ketone compound containing 3 to 6 carbon atoms is acetone, 3-pentanone, 3-hexanone, cyclopentanone or cyclohexanone.

4. The method for separating bis(trifluoromethyl) sulfide and 1,1,1,2-tetrafluoroethane according to claim 1, characterized in that: The acid anhydride compound is an acid anhydride compound containing 3 to 8 carbon atoms.

5. The method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane according to claim 4, characterized in that: The acid anhydride compound containing 3 to 8 carbon atoms is acetic anhydride, propionic anhydride, methacrylic anhydride or isobutyric anhydride.

6. The method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane according to claim 1, characterized in that: The method comprises the following steps: Step 1, using a mixture of 1,1,1,2-tetrafluoroethane and bis(trifluoromethyl)sulfide as a raw material, wherein the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 20-30%; adding the raw material and the extractant into an extractive distillation tower (T1), wherein the mass ratio of the extractant to the raw material is (12-14):1, the top fraction of the extractive distillation tower (T1) is a 1,1,1,2-tetrafluoroethane product, the bottom fraction of the extractive distillation tower (T1) is bis(trifluoromethyl)sulfide and the extractant, and the operating conditions of the extractive distillation tower (T1) are: a tower operating pressure of 170-180 kPa, a tower top temperature of -14.0--12.2° C., a bottom temperature of 69.4-163.2° C., and a reflux ratio of 0.1-3; Step 2, the bottom fraction of the extractive distillation tower (T1) enters the extractant recovery tower (T2), the bottom fraction of the extractive distillation tower (T2) is the extractant, which is circulated to the extractive distillation tower (T1); the top fraction of the extractive distillation tower (T2) is bistrifluoromethyl sulfide; the operating conditions of the extractive distillation tower (T2) are: the operating pressure in the tower is 160-170 kPa, the top temperature is -10.5--9.1°C, the bottom temperature is 70.5-178.5°C, and the reflux ratio is 0.7-13.

7. The method for separating bistrifluoromethyl sulfide and 1,1,1,2-tetrafluoroethane according to claim 6, characterized in that: In step 1, the mass percentage of 1,1,1,2-tetrafluoroethane in the raw material is 20% to 24%.

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