A method and apparatus for removing pentafluoro-chloroethane from crude pentafluoroethane

Abstract

The present application relates to the technical field of fluorine-containing fine chemical separation, and in particular to a method and device for removing pentafluoro-chloroethane from crude pentafluoroethane. The method comprises: adding an azeotrope agent to crude pentafluoroethane containing pentafluoro-chloroethane impurities, azeotrope rectification, condensing the mixed gas obtained by azeotrope rectification, returning the liquefied pentafluoroethane to the azeotrope rectification step, and collecting the unliquefied mixed gas crude product; detecting the impurity content, and collecting the gas to obtain high-purity pentafluoroethane after the detection is qualified. The present application also provides a device for removing pentafluoro-chloroethane from crude pentafluoroethane. The method steps and operation of the present application are simple, and high-purity pentafluoroethane products can be obtained by only azeotrope rectification and condensation, while the remaining crude product is returned to the raw material tank to continue azeotrope rectification and purification. In addition, the device of the present application is simple and does not require complex multi-stage rectification equipment, thereby reducing the production cost of the product.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorine-containing fine chemical separation, and particularly relates to a method and device for removing pentafluoro-chloroethane from pentafluoroethane crude. BACKGROUND

[0002] Pentafluoroethane (HFC-125) is an electronic gas widely used in the field of ultra-large-scale circuit and semiconductor material. It is mainly used in plasma etching, wafer cleaning agent, and CVD precursor. The existing production process of HFC-125 is mainly prepared by fluorination of tetrachloroethylene, and the by-product includes pentafluoro-chloroethane (CFC-115), which has a close boiling point with the target product. Due to the extremely high purity requirement of HFC-125 in the semiconductor field, the purity of most gases is required to be more than 99.99%, which puts forward higher requirements on the impurity content of HFC-125. However, it is difficult to remove the impurity CFC-115 because its boiling point is extremely close to that of the target product HFC-125 (the boiling point of CFC-115 is -39℃, and the boiling point of HFC-125 is -48℃).

[0003] Chinese patent CN103396289A discloses a method for removing CFC-115 by using extraction distillation. The method first obtains high-purity pentafluoroethane and a mixture containing pentafluoroethane and monochloro-pentafluoroethane by multi-stage extraction distillation, and then performs azeotropic distillation on the mixture to further purify the pentafluoroethane in the mixture to obtain high-purity pentafluoroethane product. The method has complex steps, large equipment and device investment, and low separation purity.

[0004] Chinese patent CN107188779B discloses a method for removing the by-product pentafluoro-chloroethane from pentafluoroethane by extraction distillation and then distillation. The method has complex steps and many devices.

[0005] In summary, there is an urgent need for a method and device with simpler steps to remove the impurity pentafluoro-chloroethane from pentafluoroethane crude. SUMMARY

[0006] To solve the technical problems of complex steps and many devices for removing the impurity pentafluoro-chloroethane from pentafluoroethane crude in the prior art, the present application provides a method and device for removing pentafluoro-chloroethane from pentafluoroethane crude, which has simple steps and requires fewer devices.

[0007] In the summary, pentafluoroethane is also known as HFC-125, and pentafluoro-chloroethane is also known as CFC-115. In the subsequent specific embodiments, HFC-125 refers to pentafluoroethane, and CFC-115 refers to pentafluoro-chloroethane.

[0008] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0009] In the first aspect, the present application provides a method for removing pentafluoro-chloroethane from crude pentafluoroethane, characterized in that the method comprises the following steps:

[0010] S1: adding an azeotrope agent into crude pentafluoroethane containing pentafluoro-chloroethane impurities, and performing azeotropic distillation to form an azeotrope of the impurity pentafluoro-chloroethane and the azeotrope agent, wherein the mass ratio of the azeotrope agent to the crude pentafluoroethane is 1:(1.5-3);

[0011] S2: condensing the mixed gas obtained by azeotropic distillation, returning the liquefied pentafluoroethane to the azeotropic distillation step, and collecting the unliquefied mixed gas crude product;

[0012] S3: detecting the impurity content of the mixed gas crude product, collecting the gas to obtain high-purity pentafluoroethane free of impurities after the detection is qualified, and recycling the mixed gas crude product if the detection is unqualified.

[0013] Preferably, in S1, the azeotrope agent is one of toluene, isoamyl acetate, difluoromethane, propane, and isobutane.

[0014] Preferably, in S1, the volume percentage of the impurity pentafluoro-chloroethane in the crude pentafluoroethane is 0.1%-10%.

[0015] Preferably, in S1, when the azeotrope agent is liquid toluene or isoamyl acetate, the azeotrope agent is first heated to a gas phase and then added to the crude pentafluoroethane; more preferably, the heating temperature of toluene is 120-150°C, and the heating temperature of isoamyl acetate is 150-200°C.

[0016] Preferably, in S1, the operating conditions of the azeotropic distillation are: pressure 0.6-0.9 MPa and temperature 0-20°C.

[0017] Preferably, in S2, the condensing temperature is -30- -20°C.

[0018] Preferably, the detection of the impurity content of the mixed gas crude product refers to the detection of the contents of pentafluoro-chloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, and water in the gas components; the detection qualification refers to that the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%; more preferably, the contents of pentafluoro-chloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide, and methane are detected by gas chromatography, the content of hydrogen fluoride is detected by Fourier infrared spectroscopy, and the content of water is detected by a mirror surface dew point instrument.

[0019] Preferably, in S3, when the impurity content of the mixed gas crude product is detected to be unqualified, i.e. the purity of pentafluoroethane in the mixed gas crude product is less than 99.9999%, the mixed gas crude product is recovered and the recovered mixed gas crude product is used as pentafluoroethane crude product for azeotropic rectification.

[0020] In a second aspect, the present application provides a device for removing pentafluoro-chloroethane from pentafluoroethane crude product, comprising a raw material tank and an azeotrope tank, the top of the raw material tank and the top of the azeotrope tank are respectively connected with the feed inlet of a rectification tower through pipelines, the top of the rectification tower is connected with the feed inlet of a condenser through a pipeline, the condenser is further provided with a top discharge port and a bottom discharge port, the bottom discharge port is connected with the rectification tower through a pipeline, the top discharge port is connected with a crude product tank and a fine product tank through pipelines, and the top of the crude product tank is connected with the raw material tank through a pipeline.

[0021] Preferably, the raw material tank is filled with pentafluoroethane crude product containing pentafluoro-chloroethane impurities;

[0022] The azeotrope tank is filled with an azeotrope, and the azeotrope tank is externally provided with a heater;

[0023] The rectification tower is externally provided with a heater;

[0024] The top discharge port of the condenser is connected with an analytical instrument; the top discharge port of the condenser continuously discharges mixed gas crude product, which is collected into the fine product tank after detection, and the mixed gas crude product that is unqualified after detection is collected into the crude product tank, and the mixed gas crude product collected in the crude product tank is re-entered into the raw material tank through a pipeline, the amount of mixed gas crude product discharged is 1-5 kg / h, and the amount of fine product discharged is 10-30 kg / h.

[0025] More preferably, the diameter of the rectification column in the rectification tower is 50-200 mm, the height of the rectification column is 20,000-30,000 mm, the packing of the rectification column is bulk Paul ring packing, the equivalent diameter of the packing is 5-10 mm, and the packing height is 18,000-27,000 mm.

[0026] More preferably, the materials of the rectification tower, the condenser, the fine product tank, the crude product tank, the pipelines and the packing are S31603, S30408 or hastelloy.

[0027] In combination of the above technical solutions, the present application has the following beneficial effects:

[0028] The present application adopts the method of azeotropic rectification to purify the crude product HFC-125 with impurity CFC-115 content of 0.1%-10%, and can obtain high-purity HFC-125 with purity of 99.999% and impurity CFC-115 volume percentage ≤0.3×10 -6 .

[0029] Compared with the prior art which needs multi-stage extractive rectification, the method for removing pentafluoro-chloroethane from crude pentafluoroethane product has simple steps and operation, and high-purity pentafluoroethane product can be obtained only through azeotropic rectification and condensation, while the remaining crude product is returned to the raw material tank to continue azeotropic rectification and purification. In addition, the device of the method is simple, and complex multi-stage rectification equipment is not needed, thereby reducing the production cost of the product. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced as follows.

[0031] Figure 1 is a process flow diagram of the method for removing pentafluoro-chloroethane from crude pentafluoroethane product in the present application;

[0032] Figure 2 is a structural schematic diagram of the device for removing pentafluoro-chloroethane from crude pentafluoroethane product in the present application.

[0033] The drawings show that: 1 is a raw material tank; 2 is a co-solvent tank; 3 is a rectification tower; 4 is a condenser; 5 is a crude product tank; 6 is a fine product tank; 7 is a heater; and 8 is an analysis instrument. DETAILED DESCRIPTION

[0034] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined application purposes, the following clearly and completely describes and illustrates the present application by combining the preferred embodiments with the accompanying drawings. Figures 1-2 and the preferred embodiments.

[0035] The prior art has a method for removing other fluorinated impurities from metal fluorides by azeotropic distillation, specifically removing molybdenum hexafluoride from tungsten hexafluoride by azeotropic distillation. The boiling point of tungsten hexafluoride is 17.5℃, which is gaseous at room temperature. The boiling point of molybdenum hexafluoride is 34℃ and is solid at room temperature. The boiling point difference is nearly 17℃. In the present application, the boiling points of pentafluoroethane and pentafluoro-chloroethane are -48℃ and -39℃, respectively. Both of them are gaseous at room temperature and have a boiling point difference of 9℃. Compared with the boiling point difference between tungsten hexafluoride and molybdenum hexafluoride, the boiling points of pentafluoroethane and pentafluoro-chloroethane are more similar and more difficult to separate. Therefore, the method for removing other fluorinated impurities from metal fluorides by azeotropic distillation in the prior art is not completely applicable to the present application. Therefore, we have conducted a large number of experiments to explore the optimal scheme for removing pentafluoro-chloroethane from pentafluoroethane by azeotropic distillation and have screened a suitable azeotropic agent from a large number of chemical reagents for the present application. It is found that the present application can achieve the purpose of removing the impurity pentafluoro-chloroethane from pentafluoroethane by azeotropic distillation at 0℃-20℃, and the purity of the final pentafluoroethane is greater than or equal to 99.9999%. Compared with the distillation temperature of 30℃-42℃ used in the prior art to remove molybdenum hexafluoride from tungsten hexafluoride, the present application reduces the distillation temperature and greatly reduces the energy consumption for impurity removal, saving the cost.

[0036] A method for removing pentafluoro-chloroethane from pentafluoroethane crude, as shown in Figure 1 , comprising the following steps:

[0037] S1: adding an azeotropic agent to pentafluoroethane crude containing 0.1%-10% pentafluoro-chloroethane impurities, and performing azeotropic distillation under the operating conditions of a pressure of 0.6MPa-0.9MPa and a temperature of 0℃-20℃ to form an azeotrope of the impurity pentafluoro-chloroethane and the azeotropic agent, wherein the azeotropic agent is one of toluene, isopentyl acetate, difluoromethane, propane, and isobutane, and the mass ratio of the azeotropic agent to the pentafluoroethane crude is 1:(1.5-3);

[0038] S2: condensing the mixed gas obtained by azeotropic distillation at -30℃- -20℃, liquefying the pentafluoroethane in the mixed gas and returning it to the azeotropic distillation step, and collecting the unliquefied mixed gas crude;

[0039] S3: Every 30 minutes, the content of impurities pentafluorochloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, and water in the crude mixed gas is detected. If the purity of pentafluoroethane in the mixed gas is less than 99.9999%, the test is unqualified, the unqualified crude mixed gas is collected and returned to S1 for azeotropic distillation; if the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%, the test is qualified, the gas is collected to obtain high-purity pentafluoroethane with impurities removed.

[0040] An apparatus for removing pentafluorochloroethane from crude pentafluoroethane, such as... Figure 2 As shown, the system includes a raw material tank 1 and an azeotropic agent tank 2. The raw material tank 1 contains crude pentafluoroethane containing pentafluorochloroethane impurities, and the azeotropic agent tank 2 contains an azeotropic agent. A heater 7 is installed outside the azeotropic agent tank 2 to heat the liquid-phase azeotropic agent inside. The tops of the raw material tank 1 and the azeotropic agent tank 2 are respectively connected to the feed inlet of a distillation column 3 through pipes. The heater 7 is installed outside the distillation column 3 to heat the mixture of crude pentafluoroethane and azeotropic agent inside the distillation column 3. The top of the distillation column 3 is connected to the feed inlet of a condenser 4 through a pipe. The condenser 4 is also provided with a top outlet and a bottom outlet. The bottom outlet is connected to the distillation column 3 through a pipe, and the top outlet is connected to a crude product tank 5 and a refined product tank 6 through pipes respectively. The top of the crude product tank 5 is connected to the raw material tank 1 through a pipe, and the crude pentafluoroethane collected in the crude product tank 5 is reintroduced into the raw material tank 1 through a pipe. The crude product yield of the unliquefied mixed gas is 1–5 kg / h, and the refined product yield of pentafluoroethane is 10–20 kg / h.

[0041] The diameter of the distillation column in distillation column 3 is 50-200 mm, the height of the distillation column is 20000-30000 mm, the distillation column packing is bulk Pall ring packing, the equivalent diameter of the packing is 5-10 mm, and the packing height is 18000-27000 mm.

[0042] The materials of the distillation column 3, condenser 4, refined product tank 6, crude product tank 5, pipelines and packing are S31603, S30408 ​​or Hastelloy.

[0043] The top outlet of the condenser 4 is connected to an analytical instrument 8 for detecting the gas at the outlet. The analytical instrument 8 includes a gas chromatograph for detecting pentafluorochloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide, and methane, a Fourier transform infrared spectrometer for detecting hydrogen fluoride, and a mirror dew point meter for detecting water.

[0044] The top outlet of the condenser 4 continuously discharges the mixed gas crude product, which is detected. When the purity of the pentafluoroethane is detected to be greater than or equal to 99.9999%, the discharged gas is collected into the fine product tank 6; when the purity of the pentafluoroethane is detected to be less than 99.9999%, the discharged gas is collected into the crude product tank 5, and the gas collected into the crude product tank 5 is returned to the raw material tank 1 through a pipeline, and the subsequent azeotropic distillation step is continued.

[0045] The HFC-125 gas collected into the fine product tank 6 should meet the following impurity control indicators, and the following control indicators are all volume percentages.

[0046] Table 1 Impurity control indicators (unit: × 10 -6 )

[0047]

[0048]

[0049] Example 1

[0050] A method for removing pentafluoro-chloroethane in pentafluoroethane crude product, specifically comprising the following steps: respectively adding 15 kg of HFC-125 crude product containing 5.3% CFC-115 impurities in the raw material tank 1 and 7.5 kg of azeotrope propane in the azeotrope tank 2 into the distillation column 3 through the feed inlet of the distillation column 3, wherein the mass ratio of the azeotrope propane to the HFC-125 crude product is 1:2, and since the azeotrope propane is in gas phase, the azeotrope tank 2 does not need to be heated, and the impurity components and contents in the HFC-125 crude product are shown in Table 2.

[0051] Table 2 Volume content of impurity components in HFC-125 crude product

[0052] Impurity composition CFC-115 O2 [N2] CO CO2 CH4 H2O HF Content / % 5.3 0.08 0.02 0.03 0.03 0.05 0.22 0.10

[0053] The diameter of the distillation column is 100 mm, the height of the distillation column is 25000 mm, the packing of the distillation column is bulk packing, the equivalent diameter of the packing is 7.5 mm, and the packing height is 22000 mm. The materials of the distillation column 3, the condenser 4, the fine product tank 6, the crude product tank 5, the pipeline and the packing are hastelloy.

[0054] The azeotrope of propane and CFC-115 is formed in the rectification column 3, the pressure of the rectification column is 0.8 MPa, the temperature is 10°C, the azeotrope is vaporized with HFC-125; then the HFC-125 is liquefied by the condenser 4 under the condition of -25°C, the mixed gas crude product which is not liquefied is continuously taken out and stored in the crude product tank 5, the taking-out amount is 3 kg / h, the time interval is 0.5 h, the mixed gas crude product taken out by the condenser is analyzed for impurities, the contents of pentafluoro-chloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide and methane are detected by a gas chromatograph, the content of hydrogen fluoride is detected by a Fourier infrared spectrometer, and the content of water is detected by a mirror surface dew point meter, and the contents of each impurity detected are shown in Table 3. After the purity meets the standard, the fine HFC-125 is taken out and stored in the fine product tank 6, the taking-out amount of the fine HFC-125 is 20 kg / h, the content of the impurity CFC-115 in the taken-out HFC-125 is ≤0.3×10 -6 , and the purity of the taken-out HFC-125 can reach 99.999%.

[0055] Table 3: Component and volume content of impurities in the rectification process

[0056]

[0057] Example 2

[0058] A method for removing pentafluoro-chloroethane from the crude pentafluoroethane, specifically comprising the following steps: the HFC-125 crude product 15 kg containing 0.12% CFC-115 impurities in the raw material tank 1 and the azeotrope toluene 10 kg in the azeotrope tank 2 are respectively added to the rectification column 3 from the feed inlet of the rectification column, wherein the mass ratio of the azeotrope toluene to the HFC-125 crude product is 1:1.5; the impurity components and contents in the HFC-125 crude product are shown in Table 4; since the toluene is in liquid phase, the toluene is heated to gas phase at 120°C by the heater 7 connected to the azeotrope tank 2 before being introduced into the rectification column 3.

[0059] Table 4: Volume content of impurity components in the HFC-125 crude product

[0060] Impurity composition CFC-115 O2 [N2] CO CO2 CH4 H2O HF Content / % 0.12 0.01 0.02 0.02 0.01 0.06 0.15 0.13

[0061] The diameter of the rectification column in the rectification column 3 is 50 mm, the height of the rectification column is 20000 mm, the rectification column is filled with bulk Pall ring packing, the equivalent diameter of the packing is 5 mm, and the packing height is 18000 mm. The materials of the rectification column 3, the condenser 4, the fine product tank 6, the crude product tank 5, the pipeline and the packing are S30408.

[0062] The azeotrope of toluene and CFC-115 is vaporized in the rectification column 3 under the pressure of 0.9 MPa and the temperature of 0°C, and then the HFC-125 is liquefied by the condenser 4 under the temperature of -30°C. The unliquefied mixed gas crude product is continuously taken out and stored in the crude product tank 5 at the rate of 1 kg / h and the time interval of 0.5 h. The impurity analysis of the mixed gas crude product taken out from the condenser 4 is performed, and the contents of pentafluoro-chloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide and methane are detected by the gas chromatograph, the content of hydrogen fluoride is detected by the Fourier infrared spectrometer, and the content of water is detected by the mirror surface dew point meter. The detected contents of each impurity are shown in Table 5. After the purity meets the standard, the fine HFC-125 is taken out and stored in the fine product tank 6 at the rate of 10 kg / h. The content of the impurity CFC-115 in the taken-out fine HFC-125 is ≤0.3×10 -6 , and the purity of HFC-125 is 99.999%.

[0063] Table 5: Components and volume contents of impurities in the rectification process

[0064]

[0065]

[0066] Example 3

[0067] A method for removing pentafluoro-chloroethane from the crude pentafluoroethane, specifically comprising the following steps: the HFC-125 crude product 15 kg containing 10.25% of the impurity CFC-115 in the raw material tank 1 and the azeotrope isopentyl acetate 5 kg in the azeotrope tank 2 are added into the rectification column 3 through the feed inlet of the rectification column 3, wherein the mass ratio of the azeotrope isopentyl acetate to the HFC-125 crude product is 1:3; the impurity components and contents in the HFC-125 crude product are shown in Table 6; since the isopentyl acetate is in the liquid phase, the isopentyl acetate is heated to the gas phase at 200°C by the heater 7 connected to the azeotrope tank 2 before being introduced into the rectification column 3.

[0068] Table 6: Volume contents of impurity components in the HFC-125 crude product

[0069] Impurity composition CFC-115 O2 [N2] CO CO2 CH4 H2O HF Content / % 10.25 0.05 0.01 0.04 0.04 0.02 0.18 0.07

[0070] The diameter of the rectification column is 200 mm, the height of the rectification column is 30000 mm, the packing of the rectification column is bulk Pall ring packing, the equivalent diameter of the packing is 10 mm, and the packing height is 27000 mm. The materials of the rectification column 3, the condenser 4, the fine product tank 6, the crude product tank 5, the pipeline and the packing are S31603.

[0071] The isopentyl acetate and CFC-115 form an azeotrope in the rectification column 3, the pressure of the rectification column 3 is 0.6 MPa, the temperature is 20°C, the azeotrope is vaporized with HFC-125; then the HFC-125 is liquefied by the condenser 4 under the condition of -20°C, the mixed gas crude product which is not liquefied is continuously taken out and stored in the crude product tank 5, the taking-out amount is 5 kg / h, the time interval is 0.5 h, the mixed gas crude product taken out by the condenser 4 is analyzed by gas chromatography, Fourier infrared spectrum and water content, wherein the content of each impurity is shown in Table 7. After the purity meets the standard, the fine HFC-125 is taken out and stored in the fine product tank 6, the taking-out amount of the fine product is 30 kg / h, the content of the impurity CFC-115 in the fine HFC-125 taken out is ≤0.3×10 -6 , and the purity of the HFC-125 taken out can reach 99.999%.

[0072] Table 7 Composition and volume content of impurities in the rectification process

[0073]

[0074] Example 4

[0075] The difference between this example and Example 1 is that the azeotrope agent is difluoromethane, and other experimental conditions are the same.

[0076] The content of each impurity in the mixed gas crude product taken out is shown in Table 8. In the fine product taken out, the content of the impurity CFC-115 in the HFC-125 is ≤0.3×10 -6 , and the purity of the HFC-125 taken out can reach 99.999%.

[0077] Table 8 Composition and volume content of impurities in the rectification process

[0078]

[0079]

[0080] Example 5

[0081] The difference between this example and Example 1 is that the azeotrope agent is isobutane, and other experimental conditions are the same.

[0082] The content of each impurity in the mixed gas crude product taken out is shown in Table 9. In the fine product taken out, the content of the impurity CFC-115 in the HFC-125 is ≤0.3×10 -6 , and the purity of the HFC-125 taken out can reach 99.999%.

[0083] Table 9 Composition and volume content of impurities in the rectification process

[0084]

[0085] Comparative Example 1

[0086] The comparative example selects the embodiment 1 in a patent CN103396289A as a comparative example, and a technical scheme of the comparative example is as follows:

[0087] In the mixture of chloropentafluoroethane and pentafluoroethane to be separated: the content of chloropentafluoroethane is 1wt%, the content of pentafluoroethane is 98.5wt%, and the content of tetrafluoroethane and its homologues is <0.02wt%.

[0088] The mixture of chloropentafluoroethane and pentafluoroethane is sequentially subjected to a multi-stage extraction rectification system and an azeotropic rectification system to obtain high-purity pentafluoroethane and high-purity chloropentafluoroethane. Specifically, the mixture is sequentially subjected to one extraction rectification, one flash evaporation, two extraction rectifications, two flash evaporations, and pentafluoroethane extraction rectification five steps to obtain high-purity pentafluoroethane product, and the purity is 99.9%.

[0089] Compared with the embodiment 1-5 in the application, the separation process adopted by the comparative example 1 is complicated, and the purity of the pentafluoroethane product obtained by purification is 99.9%, which is lower than the purity in the embodiment of the application. In addition, the comparative example also uses a large amount of extractant petroleum hydrocarbon (the ratio of the amount of the extractant to the mixture to be separated is 2-5:1), and the consumption of the organic solvent is large and the cost is high. It is further illustrated that the method of the application not only has simple steps, but also has higher product purity and less amount of azeotropic agent.

[0090] Comparative Example 2

[0091] The difference between the comparative example and the embodiment 1 is that the comparative example uses sulfur dioxide as the azeotropic agent.

[0092] In the process of azeotropic rectification for purifying HFC-125, when the mixed gas crude product collected from the condenser 4 is analyzed for impurities, the volume percentage content of the impurity CFC-115 is reduced to 0.13%, and then no longer continues to decrease with the experiment, so it is directly collected into the fine product tank 6, and the purity of the finally collected HFC-125 is 98.85%.

[0093] Compared with the embodiment 1, the purity of the fine product of HFC-125 finally collected in the comparative example is 98.85%, which is much lower than 99.999% in the embodiment 1, which shows that the azeotropic rectification purification effect of the azeotropic agent sulfur dioxide in the comparative example is poor.

[0094] Comparative Example 3

[0095] The difference between the comparative example and the embodiment 1 is that the comparative example uses isobutene as the azeotropic agent.

[0096] In the process of azeotropic distillation for purifying HFC-125, the volume percentage of impurity CFC-115 in the mixed gas crude product collected from the condenser 4 is reduced to 0.34%, and then no longer continues to decrease with the experiment, so the impurity is directly collected into the fine product tank 6, and the purity of the finally collected HFC-125 is 97.15%.

[0097] Compared with Example 1, the purity of the finally collected HFC-125 fine product in the present comparative example is 97.15%, which is far lower than 99.999% in Example 1, indicating that the azeotropic distillation purifying effect of the azeotropic agent isobutene in the present comparative example is poor.

[0098] In summary, the method for removing pentafluoro-chloroethane from the crude pentafluoroethane product according to the present application has simple steps and operation, and high-purity pentafluoroethane product can be collected only by azeotropic distillation and condensation, while the remaining crude product is returned to the raw material tank for further azeotropic distillation and purification. In addition, the device of the present application is simple, and does not need complex multi-stage distillation equipment, thereby reducing the production cost of the product.

[0099] The above description is only the preferred embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any modification, change, equivalent change and modification of the above embodiments, which does not depart from the technical solution of the present application, and is based on the technical essence of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A method for removing pentafluoro-chloroethane from crude pentafluoroethane, characterized in that, The method comprises the following steps: S1: adding azeotrope agent into crude pentafluoroethane containing pentafluoro-monochloroethane impurities, and azeotrope distillation is performed to form azeotrope of the impurity pentafluoro-monochloroethane and the azeotrope agent, and the mass ratio of the azeotrope agent to the crude pentafluoroethane is 1:(1.5-3); in S1, the azeotrope agent is one of toluene, isoamyl acetate, difluoromethane, propane and isobutane; in S1, the operation condition of the azeotrope distillation is that the pressure is 0.6-0.9 MPa, and the temperature is 0-20℃; S2: condensing the mixed gas obtained by the azeotrope distillation, returning the liquefied pentafluoroethane to the azeotrope distillation step, and collecting the unliquefied mixed gas crude product; the operation condition of the condensation is -30--20℃; S3: detecting the impurity content of the mixed gas crude product, collecting the gas to obtain high-purity pentafluoroethane after the detection is qualified, and recycling the mixed gas crude product if the detection is unqualified.

2. The method for removing pentafluoro-chloroethane from crude pentafluoroethane according to claim 1, characterized in that, In S1, the volume percentage of the impurity pentafluoro-monochloroethane in the crude pentafluoroethane is 0.1%-10%.

3. The method for removing pentafluoro-chloroethane from crude pentafluoroethane according to claim 1, characterized by, In S1, when the azeotrope agent is liquid toluene or isoamyl acetate, the azeotrope agent is heated to gas phase first and then added into the crude pentafluoroethane.

4. The method for removing pentafluoro-chloroethane from crude pentafluoroethane according to claim 1, characterized by, In S3, the detection of the impurity content of the mixed gas crude product refers to the detection of the contents of pentafluoro-monochloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane and water in the mixed gas crude product; the detection qualification refers to that the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%.

5. The method of claim 1, wherein the method is characterized by, In S3, when the impurity content of the mixed gas crude product is unqualified, i.e., the purity of pentafluoroethane in the mixed gas is less than 99.9999%, the mixed gas crude product is recycled, and the recycled mixed gas crude product is continuously used as the crude pentafluoroethane for azeotrope distillation.

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