Method and device for removing pentafluoromonochloroethane in pentafluoroethane crude product

Abstract

The invention relates to the technical field of fluorine-containing fine chemical separation, in particular to a method and a device for removing chloropentafluoroethane in a pentafluoroethane crude product. The method comprises the following steps: adding an entrainer into a pentafluoroethane crude product containing pentafluoromonochloroethane impurities, carrying out azeotropic distillation, condensing mixed gas obtained by azeotropic distillation, returning liquefied pentafluoroethane to the step of azeotropic distillation, and collecting an unliquefied mixed gas crude product; and detecting the content of impurities, and collecting the gas to obtain the impurity-removed high-purity pentafluoroethane after the impurity content is detected to be qualified. The invention further provides a device for removing the pentafluoromonochloroethane in the pentafluoroethane crude product. The method disclosed by the invention is simple in steps and operation, a high-purity pentafluoroethane product can be extracted only through azeotropic distillation and condensation, and meanwhile, the residual crude product is returned to the raw material tank to be continuously subjected to azeotropic distillation purification. In addition, the device is simple, complex multi-stage rectification equipment is not needed, and the production cost of the product is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine-containing fine chemical separation, and in particular relates to a method and a device for removing monochloropentafluoroethane from crude pentafluoroethane. Background Art

[0002] Pentafluoroethane (HFC-125) is an electronic gas widely used in the field of ultra-large-scale circuits and semiconductor materials. It is mainly used in plasma etching, wafer cleaning agents, and chemical vapor deposition (CVD) precursors. The existing production process of HFC-125 is mainly to prepare tetrachloroethylene through a fluorination method, and the by-product includes pentafluoromonochloroethane (CFC-115), which has a boiling point close to that of the target product. Since the semiconductor field has extremely high requirements for the purity of HFC-125, the purity of most gases is required to reach more than 99.99%, which puts higher requirements on the impurity content in HFC-125. However, because the boiling point of the impurity CFC-115 is extremely close to that of the target product HFC-125 (the boiling point of CFC-115 is -39°C, and the boiling point of HFC-125 is -48°C), it is difficult to remove.

[0003] Chinese patent CN103396289A discloses a method for separating chloropentafluoroethane and pentafluoroethane, and discloses a method for removing CFC-115 by extractive distillation. The patent first obtains high-purity pentafluoroethane and a mixture containing pentafluoroethane and chlorofluoroethane by multi-stage extractive distillation, and then performs azeotropic distillation on the mixture to further purify the pentafluoroethane in the mixture to obtain a high-purity pentafluoroethane product. The method is through multi-stage extractive distillation and azeotropic distillation, with complex steps, large investment in equipment and devices, and low separation purity.

[0004] Chinese patent CN107188779B discloses a method for purifying pentafluoroethane, which discloses a method of first extracting and rectifying and then distilling to remove the byproduct monochloropentafluoroethane in pentafluoroethane. The method has complex steps and requires many equipments.

[0005] In summary, a method and apparatus with simpler steps are urgently needed to remove the impurity pentafluoromonochloroethane in crude pentafluoroethane. Summary of the invention

[0006] In order to solve the technical problem that the prior art has complicated steps and many equipments for removing the impurity monochloropentafluoroethane in crude pentafluoroethane, the present invention provides a method and a device for removing monochloropentafluoroethane in crude pentafluoroethane, which has simple steps and requires few equipments.

[0007] In the present invention, pentafluoroethane is also known as HFC-125; pentafluoromonochloroethane is also known as CFC-115. In the subsequent specific embodiments, HFC-125 mentioned refers to pentafluoroethane, and CFC-115 mentioned refers to pentafluoromonochloroethane.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a method for removing monochloropentafluoroethane from a crude pentafluoroethane product, characterized in that it comprises the following steps:

[0010] S1: adding an azeotropic agent to a crude pentafluoroethane product containing pentafluoromonochloroethane as an impurity, and subjecting the impurity pentafluoromonochloroethane and the azeotropic agent to azeotropy by azeotropic distillation, wherein the mass ratio of the azeotropic agent to the crude pentafluoroethane product 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 crude mixed gas;

[0012] S3: detecting the impurity content of the crude mixed gas product. If the detection is qualified, collecting the gas to obtain high-purity pentafluoroethane with impurities removed; if the detection is unqualified, recovering the crude mixed gas product.

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

[0014] Preferably, in S1, the volume percentage of the impurity monochloropentafluoroethane in the crude pentafluoroethane is 0.1% to 10%.

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

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

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

[0018] Preferably, the impurity content of the crude mixed gas is detected by detecting the contents of pentafluoromonochloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane and water in the gas components; the qualified detection means that the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%; more preferably, the contents of pentafluoromonochloroethane, 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 water content is detected by a mirror dew point meter.

[0019] Preferably, in S3, when the impurity content of the crude mixed gas fails to meet the test requirements, that is, the purity of pentafluoroethane in the crude mixed gas is less than 99.9999%, the crude mixed gas is recovered and further used as crude pentafluoroethane for azeotropic distillation.

[0020] In a second aspect, the present invention provides a device for removing monochloropentafluoroethane from a crude pentafluoroethane product, comprising a raw material tank and an entrainer tank, wherein the tops of the raw material tank and the entrainer tank are respectively connected to a feed port of a distillation tower through pipelines, the top of the distillation tower is connected to a feed port 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 to the distillation tower through a pipeline, the top discharge port is respectively connected to a crude product tank and a fine product tank through pipelines, and the top of the crude product tank is connected to the raw material tank through a pipeline.

[0021] Preferably, the raw material tank contains crude pentafluoroethane containing pentafluoromonochloroethane impurities;

[0022] The entrainer tank is filled with an entrainer, and a heater is arranged outside the entrainer tank;

[0023] A heater is provided outside the distillation tower;

[0024] The top discharge port of the condenser is connected to an analytical instrument; and the top discharge port of the condenser continuously produces a crude mixed gas product, which is collected into a fine product tank after being tested qualified, and the crude mixed gas product that fails the test is collected into a crude product tank, and the crude mixed gas collected in the crude product tank re-enters the raw material tank through a pipeline, the production volume of the crude mixed gas is 1 to 5 kg / h, and the production volume of the fine product is 10 to 30 kg / h.

[0025] More preferably, the diameter of the distillation column in the distillation tower is 50-200 mm, the height of the distillation column is 20000-30000 mm, the distillation column filler is bulk ball ring filler, the filler equivalent diameter is 5-10 mm, and the filling height of the filler is 18000-27000 mm.

[0026] More preferably, the distillation tower, condenser, fine product tank, crude product tank, pipeline and filler are made of S31603, S30408 ​​or Hastelloy.

[0027] Based on the above technical solutions, the present invention has the following beneficial effects:

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

[0029] Compared with the prior art which requires multi-stage extractive distillation, the method for removing monochloropentafluoroethane from crude pentafluoroethane of the present invention has simple steps and operation, and can produce high-purity pentafluoroethane products only through 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 invention is simple, does not require complex multi-stage distillation equipment, and reduces the production cost of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art are briefly introduced below.

[0031] Figure 1 It is a process flow chart of a method for removing monochloropentafluoroethane from crude pentafluoroethane in the present invention;

[0032] Figure 2 The present invention is a schematic structural diagram of a device for removing monochloropentafluoroethane from crude pentafluoroethane.

[0033] Figure numerals: 1-raw material tank; 2-entrainer tank; 3-distillation tower; 4-condenser; 5-crude product tank; 6-fine product tank; 7-heater; 8-analytical instrument. DETAILED DESCRIPTION

[0034] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined application purpose, the following is combined with the attached Figure 1-2 And the preferred embodiments are clearly and completely described.

[0035] The prior art has a method of removing other fluoride impurities in metal fluorides by azeotropic distillation, specifically, removing molybdenum hexafluoride from tungsten hexafluoride by azeotropic distillation. The boiling point of tungsten hexafluoride is 17.5°C, and it is gaseous at room temperature. The boiling point of molybdenum hexafluoride is 34°C and it is solid at room temperature. The difference in boiling points is nearly 17°C. In the present application, the boiling points of pentafluoroethane and pentafluoromonochloroethane are -48°C and -39°C, respectively. Both of them have low boiling points, are gaseous at room temperature, and the difference in boiling points is 9°C. Compared with the difference in boiling points of tungsten hexafluoride and molybdenum hexafluoride, the boiling points of pentafluoroethane and pentafluoromonochloroethane are closer, and it is more difficult to separate them. Therefore, the prior art method of removing other fluoride impurities in metal fluorides by azeotropic distillation is not completely applicable to the present application. Therefore, we have done a lot of experiments to explore the optimal solution for removing pentafluoromonochloroethane from pentafluoroethane by azeotropic distillation and screened out azeotropes suitable for this application from a large number of chemical reagents. At the same time, we found that this application can achieve the purpose of removing the impurity pentafluoromonochloroethane from pentafluoroethane by azeotropic distillation under 0℃~20℃, and the purity of the pentafluoroethane finally obtained 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 invention reduces the distillation temperature, greatly reduces the energy consumption of impurity removal, and saves cost expenditure. The following content will introduce in detail the method and device for removing pentafluoromonochloroethane from crude pentafluoroethane in this application.

[0036] A method for removing monochloropentafluoroethane from crude pentafluoroethane, such as Figure 1 As shown, the following steps are included:

[0037] S1: adding an entrainer to a crude pentafluoroethane product having a pentafluorochloroethane impurity content of 0.1% to 10% by volume, and performing azeotropic distillation under the operating conditions of a pressure of 0.6 MPa to 0.9 MPa and a temperature of 0° C. to form an azeotrope with the impurity pentafluorochloroethane and the entrainer, wherein the entrainer is one of toluene, isoamyl acetate, difluoromethane, propane, and isobutane, and the mass ratio of the entrainer to the crude pentafluoroethane product is 1:(1.5 to 3);

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

[0039] S3: every 30 minutes, the contents of impurities such as pentafluoromonochloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane and water in the crude mixed gas are detected. When the purity of pentafluoroethane in the mixed gas is less than 99.9999%, the detection is unqualified, and the unqualified crude mixed gas is collected and returned to S1 for further azeotropic distillation; when the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%, the detection is qualified, and the gas is collected to obtain high-purity pentafluoroethane with impurities removed.

[0040] A device for removing monochloropentafluoroethane from crude pentafluoroethane, such as Figure 2 As shown, it includes a raw material tank 1 and an entrainer tank 2, the raw material tank 1 is filled with crude pentafluoroethane containing pentafluoromonochloroethane impurities, the entrainer tank 2 is filled with an entrainer, and a heater 7 is arranged outside the entrainer tank 2 to heat the liquid phase entrainer inside it; the tops of the raw material tank 1 and the entrainer tank 2 are respectively connected to the feed port of the distillation tower 3 through pipelines, the distillation tower 3 is provided with a heater 7 outside for heating the mixture of crude pentafluoroethane and entrainer in the distillation tower 3, the top of the distillation tower 3 is connected to the feed port of the condenser 4 through a pipeline, the condenser 4 is also provided with a top discharge port and a bottom discharge port, the bottom discharge port is connected to the distillation tower 3 through a pipeline, and the top discharge port is respectively connected to the crude product tank 5 and the fine product tank 6 through pipelines; the top of the crude product tank 5 is connected to the raw material tank 1 through a pipeline, and the crude pentafluoroethane collected in the crude product tank 5 re-enters the raw material tank 1 through the pipeline. The production rate of crude unliquefied mixed gas is 1-5 kg / h, and the production rate of fine pentafluoroethane is 10-20 kg / h.

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

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

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

[0044] The top discharge port of the condenser 4 continuously produces a crude mixed gas product, which is tested. When the purity of pentafluoroethane is detected to be greater than or equal to 99.9999%, the produced gas is collected into the fine product tank 6; when the purity of pentafluoroethane is detected to be lower than 99.9999%, the produced gas is recovered into the crude product tank 5, and the gas recovered into the crude product tank 5 is returned to the raw material tank 1 through a pipeline, and the azeotropic distillation step is subsequently continued.

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

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

[0047]

[0048]

[0049] Example 1

[0050] A method for removing monochloropentafluoroethane from a crude pentafluoroethane product comprises the following steps: 15 kg of a crude HFC-125 product containing 5.3% of CFC-115 impurities in a raw material tank 1 and 7.5 kg of an entrainer propane in an entrainer tank 2 are respectively added into a distillation tower 3 through a feed port of the distillation tower 3, wherein the mass ratio of the entrainer propane to the crude HFC-125 product is 1:2, and since the entrainer propane is in a gas phase, the entrainer tank 2 does not need to be heated. The impurity components and contents in the crude HFC-125 product are shown in Table 2.

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

[0052] Impurity ingredients CFC-115 <![CDATA[O2]]> <![CDATA[N2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> <![CDATA[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 filler of the distillation column is bulk filler, the filler equivalent diameter is 7.5 mm, and the filling height of the filler is 22000 mm. The distillation tower 3, condenser 4, fine product tank 6, crude product tank 5, pipeline and filler are made of Hastelloy.

[0054] In the distillation tower 3, propane and CFC-115 form an azeotrope, the distillation tower pressure is 0.8MPa, the temperature is 10°C, and the azeotrope and HFC-125 are gasified; then HFC-125 is liquefied and refluxed through the condenser 4 at -25°C, and the unliquefied crude mixed gas is continuously produced and stored in the crude product tank 5, the production volume is 3kg / h, and the time interval is 0.5h. The crude mixed gas produced by the condenser is analyzed for impurities, and the contents of pentafluoromonochloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide, and methane are detected by gas chromatograph, the content of hydrogen fluoride is detected by Fourier infrared spectrometer, and the content of water is detected by mirror dew point meter. The detected impurity contents are shown in Table 3. After the purity reaches the standard, the fine HFC-125 is produced and stored in the fine product tank 6, the fine production volume is 20kg / h, and the content of CFC-115 impurity in the produced HFC-125 is ≤0.3×10 -6 The purity of HFC-125 produced can reach 99.999%.

[0055] Table 3 Composition and volume content of impurities during distillation

[0056]

[0057] Example 2

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

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

[0060] Impurity ingredients CFC-115 <![CDATA[O2]]> <![CDATA[N2]]> CO <![CDATA[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 distillation column in the distillation tower 3 is 50 mm, the height of the distillation column is 20000 mm, the distillation column filler is bulk ball ring filler, the filler equivalent diameter is 5 mm, and the filling height of the filler is 18000 mm. The material of the distillation tower 3, condenser 4, fine product tank 6, crude product tank 5, pipeline and filler is S30408.

[0062] Toluene and CFC-115 form an azeotrope in the distillation tower 3. The pressure in the distillation tower 3 is 0.9 MPa and the temperature is 0°C. The azeotrope and HFC-125 are vaporized. Then, HFC-125 is liquefied and refluxed at -30°C through the condenser 4. The unliquefied crude mixed gas is continuously extracted and stored in the crude product tank 5. The extraction rate is 1 kg / h. The crude mixed gas extracted from the condenser 4 is analyzed for impurities at a time interval of 0.5 h. The contents of pentafluoromonochloroethane, oxygen, nitrogen, carbon monoxide, carbon dioxide, and methane are detected by gas chromatograph, the content of hydrogen fluoride is detected by Fourier infrared spectrometer, and the content of water is detected by mirror dew point meter. The detected impurity contents are shown in Table 5. After the purity reaches the standard, the fine HFC-125 is extracted and stored in the fine product tank 6. The fine production rate is 10 kg / h. The impurity CFC-115 content in the extracted fine HFC-125 is ≤0.3×10 -6 , the purity of HFC-125 is 99.999%.

[0063] Table 5 Composition and volume content of impurities during distillation

[0064]

[0065]

[0066] Example 3

[0067] A method for removing monochloropentafluoroethane from a crude pentafluoroethane product comprises the following steps: 15 kg of a crude HFC-125 product containing 10.25% of a CFC-115 impurity in a raw material tank 1 and 5 kg of an entrainer isoamyl acetate in an entrainer tank 2 are respectively added into a distillation tower 3 through a feed port of the distillation tower 3, wherein the mass ratio of the entrainer isoamyl acetate to the crude HFC-125 product is 1:3; the impurity components and contents in the crude HFC-125 product are shown in Table 6; and since the isoamyl acetate is in a liquid phase, before being introduced into the distillation tower 3, the isoamyl acetate is first heated to a gas phase at 200°C by a heater 7 connected to the entrainer tank 2.

[0068] Table 6 Volume content of impurity components in crude HFC-125

[0069] Impurity ingredients CFC-115 <![CDATA[O2]]> <![CDATA[N2]]> CO <![CDATA[CO2]]> <![CDATA[CH4]]> <![CDATA[H2O]]> HF content / % 10.25 0.05 0.01 0.04 0.04 0.02 0.18 0.07

[0070] The diameter of the distillation column is 200 mm, the height of the distillation column is 30000 mm, the distillation column filler is bulk ball ring filler, the filler equivalent diameter is 10 mm, and the filling height of the filler is 27000 mm. The material of the distillation tower 3, condenser 4, fine product tank 6, crude product tank 5, pipeline and filler is S31603.

[0071] In the distillation tower 3, isoamyl acetate and CFC-115 form an azeotrope, the pressure of the distillation tower 3 is 0.6MPa, the temperature is 20°C, and the azeotrope and HFC-125 are vaporized; then the HFC-125 is liquefied and refluxed at -20°C through the condenser 4, and the unliquefied crude mixed gas is continuously extracted and stored in the crude product tank 5, the extraction rate is 5kg / h, and the time interval is 0.5h. The crude mixed gas extracted from the condenser 4 is subjected to gas chromatography analysis, Fourier infrared spectroscopy analysis and moisture analysis, and the impurity content is shown in Table 7. After the purity reaches the standard, the fine HFC-125 is extracted and stored in the fine tank 6, the fine extraction rate is 30kg / h, and the impurity CFC-115 content in the extracted fine HFC-125 is ≤0.3×10 -6 The purity of HFC-125 produced can reach 99.999%.

[0072] Table 7 Composition and volume content of impurities during distillation

[0073]

[0074] Example 4

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

[0076] The impurity contents of the crude mixed gas are shown in Table 8. The impurity content of HFC-125 and CFC-115 in the fine gas is ≤0.3×10 -6 The purity of HFC-125 produced can reach 99.999%.

[0077] Table 8 Composition and volume content of impurities during distillation

[0078]

[0079]

[0080] Example 5

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

[0082] The impurity contents of the crude mixed gas are shown in Table 9. The impurity content of HFC-125 and CFC-115 in the fine gas is ≤0.3×10 -6 The purity of HFC-125 produced can reach 99.999%.

[0083] Table 9 Composition and volume content of impurities during distillation

[0084]

[0085] Comparative Example 1

[0086] This comparative example uses Example 1 in the method for separating chloropentafluoroethane and pentafluoroethane in patent CN103396289A as a comparative example. The technical scheme of this 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 less than 0.02wt%.

[0088] The mixture of chloropentafluoroethane and pentafluoroethane is sequentially subjected to a multi-stage extraction distillation system and an azeotropic distillation system to obtain high-purity pentafluoroethane and high-purity chloropentafluoroethane. Specifically, the mixture is sequentially subjected to five steps of primary extraction distillation, primary flash distillation, secondary extraction distillation, secondary flash distillation and pentafluoroethane extraction distillation to obtain a high-purity pentafluoroethane product with a purity of 99.9%.

[0089] Compared with Examples 1-5 of the present invention, the separation process used in Comparative Example 1 is cumbersome and complicated, and the purity of the pentafluoroethane product obtained by purification is 99.9%, which is lower than the purity in the examples of the present invention. In addition, the comparative example also uses a large amount of extractant petroleum hydrocarbon (the ratio of its amount to the mixture to be separated is 2 to 5:1), the organic solvent consumption is large, and the cost is high. It further illustrates that the method of the present invention is not only simple in steps, but also has a higher product purity and a small amount of entrainer.

[0090] Comparative Example 2

[0091] The difference between this comparative example and Example 1 is that sulfur dioxide is used as the azeotropic agent in this comparative example.

[0092] During the azeotropic distillation process for purifying HFC-125, when the crude mixed gas extracted from condenser 4 was analyzed for impurities, the volume percentage of the impurity CFC-115 decreased to 0.13% and then stopped decreasing as the experiment progressed. Therefore, it was directly collected in the fine product tank 6. The purity of the final extracted HFC-125 was 98.85%.

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

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that this comparative example uses isobutylene as the azeotropic agent.

[0096] During the azeotropic distillation process for purifying HFC-125, when the crude mixed gas extracted from condenser 4 was analyzed for impurities, the volume percentage of the impurity CFC-115 decreased to 0.34% and then stopped decreasing as the experiment progressed. Therefore, it was directly collected in the fine product tank 6. The purity of the final extracted HFC-125 was 97.15%.

[0097] Compared with Example 1, the purity of the HFC-125 fine product finally extracted in this comparative example is 97.15%, which is much lower than 99.999% in Example 1, indicating that the azeotropic distillation purification effect of the co-azeotropic agent isobutylene in this comparative example is poor.

[0098] In summary, the method for removing monochloropentafluoroethane from crude pentafluoroethane has simple steps and operations, and can produce a high-purity pentafluoroethane product only through 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 invention is simple, does not require complex multi-stage distillation equipment, and reduces the production cost of the product.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for removing monochloropentafluoroethane from crude pentafluoroethane, characterized in that: The steps include: S1: adding an azeotropic agent to a crude pentafluoroethane product containing pentafluoromonochloroethane as an impurity, and subjecting the impurity pentafluoromonochloroethane and the azeotropic agent to azeotropy by azeotropic distillation, wherein the mass ratio of the azeotropic agent to the crude pentafluoroethane product is 1:(1.5-3); S2: condensing the mixed gas obtained by azeotropic distillation, returning the liquefied pentafluoroethane to the azeotropic distillation step, and collecting the unliquefied crude mixed gas; S3: detecting the impurity content of the crude mixed gas product. If the detection is qualified, collecting the gas to obtain high-purity pentafluoroethane with impurities removed; if the detection is unqualified, recovering the crude mixed gas product.

2. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S1, the azeotropic agent is one of toluene, isoamyl acetate, difluoromethane, propane and isobutane.

3. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S1, the volume percentage of impurity monochloropentafluoroethane in the crude pentafluoroethane is 0.1% to 10%.

4. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S1, when the azeotropic agent is liquid toluene or isoamyl acetate, the azeotropic agent is first heated to a gas phase and then added to the crude pentafluoroethane.

5. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S1, the operating conditions of the azeotropic distillation are: pressure 0.6MPa-0.9MPa, temperature 0°C-20°C.

6. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S2, the operating conditions of the condensation are -30°C to -20°C.

7. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S3, the detection of impurity content of the crude mixed gas refers to the detection of the content of pentafluoromonochloroethane, hydrogen fluoride, oxygen, nitrogen, carbon monoxide, carbon dioxide, methane and water in the crude mixed gas; the qualified detection means that the purity of pentafluoroethane in the mixed gas is greater than or equal to 99.9999%.

8. The method for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 1, characterized in that: In S3, when the impurity content of the crude mixed gas fails to meet the requirements, that is, the purity of pentafluoroethane in the mixed gas is less than 99.9999%, the crude mixed gas is recovered and further used as crude pentafluoroethane for azeotropic distillation.

9. A device for removing monochloropentafluoroethane from crude pentafluoroethane, characterized in that: The invention comprises a raw material tank (1) and an entrainer tank (2), wherein the tops of the raw material tank (1) and the entrainer tank (2) are respectively connected to the feed port of a distillation tower (3) through pipelines, the top of the distillation tower (3) is connected to the feed port of a condenser (4) through a pipeline, the condenser (4) is also provided with a top discharge port and a bottom discharge port, the bottom discharge port is connected to the distillation tower (3) through a pipeline, the top discharge port is respectively connected to a crude product tank (5) and a fine product tank (6) through pipelines, and the top of the crude product tank (5) is connected to the raw material tank (1) through a pipeline.

10. The device for removing monochloropentafluoroethane from crude pentafluoroethane according to claim 9, characterized in that: The raw material tank (1) contains crude pentafluoroethane containing pentafluoromonochloroethane impurities; The entrainer tank (2) contains an entrainer, and a heater (7) is arranged outside the entrainer tank (2); A heater (7) is provided outside the distillation tower (3); The top discharge port of the condenser (4) is connected to an analysis instrument (8); and the top discharge port of the condenser (4) continuously produces a crude mixed gas product, and the gas components that pass the test are collected into a fine product tank (6), and the crude mixed gas products that fail the test are recovered into a crude product tank (5), and the crude mixed gas products collected in the crude product tank (5) re-enter the raw material tank (1) through a pipeline.

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