Method and system for purifying and recovering trifluoroiodomethane and trifluoromethane

Abstract

The application discloses a method and system for purifying and recycling trifluoroiodomethane and trifluoromethane, wherein the method comprises the following steps: (1) pretreatment: removing acid from the crude CF3I by alkali washing and drying the crude CF3I by using a molecular sieve; (2) initial distillation: removing light components and heavy components by vacuum rectification, and collecting a first mixture in the middle part; (3) extractive rectification: performing extractive rectification on the first mixture in a solvent to separate a first CHF3 material with high purity, first impurities and a recovered solvent; (4) solvent recovery: performing reflux distillation on the recovered solvent to obtain a recycled solvent and a crude CF3I; (5) deep refining: performing vacuum rectification on the crude CF3I and / or the first CHF3 material to obtain a product with a purity of CF3I of greater than or equal to 99.99%; and (6) tail gas treatment: performing alkali washing on the light components and / or the first impurities, and discharging the alkali washing tail gas. The application has the advantages of stability, good product quality, less impurity residues, efficient separation and purification of trifluoroiodomethane and efficient recovery of trifluoromethane.

Description

Technical Field

[0001] This invention belongs to the field of electronic-grade gas technology, specifically relating to a method and system for purifying and recovering trifluoroiodomethane and trifluoromethane. Background Technology

[0002] Trifluoroiodomethane (CF3I) is an environmentally friendly compound with low ozone depletion and global warming potential. It is widely used in refrigerants, fire extinguishing agents, semiconductor etching agents, and the synthesis of fluorine-containing intermediates, and has irreplaceable advantages, especially in replacing traditional highly polluting Freon and halon products. CHF3 (trifluoromethane) is also an important fluorine-containing chemical raw material, used in refrigerants, foaming agents, and etching gases in semiconductor manufacturing, and has high recycling value.

[0003] Currently, the purity of crude trifluoroiodomethane prepared industrially is typically only around 20%. The main impurity is CHF3 (approximately 60%), and it also contains small amounts of hydrogen fluoride (HF), hydrogen iodide (HI), iodomethane (CH3I), carbon monoxide (CO), nitrogen (N2), oxygen (O2), carbon dioxide (CO2), tetrafluoromethane (CF4), hexafluoroethane (C2F6), octafluoropropane (C3F8), pentafluoroethane (C2HF5), pentafluoroiodomethane (C2F5I), 1,1,2,2-tetrafluoroethane (CHF2CHF2), and decafluorobutane (C4F4). 10 Impurities such as octafluorobutene (C4F8) and others (totaling approximately 20%) severely limit the application of CF3I, especially in fields such as semiconductors and high-end refrigeration where extremely high purity (above 99.99%) is required. Deep purification of crude CF3I is necessary, and the high CHF3 content would result in significant resource waste if not recovered.

[0004] In existing technologies, the purification methods for trifluoroiodomethane mainly include distillation, adsorption, and washing, but these methods have many drawbacks: Distillation alone is insufficient to achieve a breakthrough from low-purity crude to 99.99% high purity, and it cannot effectively separate CF3I and CHF3 (the two have similar boiling points; CF3I boils at -22.5℃ under normal pressure, while CHF3 boils at -82.1℃. Conventional distillation easily leads to CHF3 volatilizing or remaining with CF3I, making effective recovery impossible, especially when the CHF3 content is as high as about 60%, significantly increasing the separation difficulty); Adsorption alone can only remove some acidic impurities (HF, HI) and trace organic matter (CH3I, etc.), making it difficult to reduce the content of the main impurity CHF3, and also unable to effectively remove inert or low-boiling-point impurities such as CO, N2, O2, and CF4; Traditional washing methods can remove acidic impurities (HF, HI), but they cause CF3I loss and cannot achieve the recovery and utilization of CHF3 and other recyclable impurities, leading to resource waste and increased costs.

[0005] Furthermore, existing technologies lack an integrated solution for purifying 20% ​​pure CF3I (containing approximately 60% CHF3) to 99.99% purity while simultaneously recovering CHF3. Separation and recovery at high CHF3 content presents a significant technical challenge, and it is difficult to simultaneously remove multiple impurities such as CO, N2, O2, and CF4. This results in either low purification efficiency and substandard purity, or low-purity recovered CHF3 that cannot be directly utilized, failing to meet the demands of large-scale industrial production and contradicting the development trends of energy conservation, environmental protection, and resource recycling. Therefore, developing a highly efficient, energy-saving, scalable method that simultaneously achieves deep purification of CF3I and efficient recovery of CHF3 while removing multiple impurities such as CO, N2, and O2 at a CHF3 content of approximately 60% has become a pressing technical problem in this field.

[0006] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a method and system for the purification and recovery of trifluoroiodomethane and trifluoromethane. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for purifying and recovering trifluoroiodomethane and trifluoromethane.

[0008] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0009] The purification and recovery method of trifluoroiodomethane and trifluoromethane includes the following steps: (1) Pretreatment: crude CF3I is washed with alkali to remove acid and dried with molecular sieve; (2) Initial distillation: light components and heavy components are removed by vacuum distillation, and the first mixture is collected from the middle; (3) Extractive distillation: the first mixture is extracted and distilled in a solvent to separate the first CHF3 material with high purity CHF3, the first impurity and the recovered solvent; (4) Solvent recovery: the recovered solvent is refluxed and distilled to obtain the solvent for recycling and crude CF3I; (5) Deep purification: the crude CF3I and / or the first CHF3 material are distilled under vacuum to obtain ≥99.99% CF3I finished product; (6) Tail gas treatment: light components and / or the first impurity are washed with alkali and discharged after alkali washing meets the standards.

[0010] In one or more embodiments of the present invention, the alkaline solution used for alkaline washing is an alkali metal carbonate, an alkali metal bicarbonate, or an alkali metal hydroxide, and the concentration of the alkaline solution is 0.05-10 wt.%.

[0011] In one or more embodiments of the present invention, the alkali metal is sodium or potassium.

[0012] In one or more embodiments of the present invention, the conditions for drying the molecular sieve are: temperature 20-30°C, space velocity 100-300 / h, and the molecular sieve used is 3A molecular sieve or 4A molecular sieve.

[0013] In one or more embodiments of the present invention, the initial distillation conditions are: pressure 0.05-0.1 MPa, reflux ratio (2-5):1.

[0014] In one or more embodiments of the present invention, the solvent / material mass ratio during extractive distillation is (2-4):1.

[0015] In one or more embodiments of the present invention, the solvent is at least one of ketones and acetates. Preferably, the solvent is a mixture of acetone and ethyl acetate in a volume ratio of (0.5-1.8):1.

[0016] In one or more embodiments of the present invention, the conditions for extractive distillation are: pressure 0.1-0.2 MPaA, reflux ratio (3-6):1.

[0017] In one or more embodiments of the present invention, the conditions for vacuum distillation are: pressure 0.02-0.05 MPaA, reflux ratio (5-8):1.

[0018] In one or more embodiments of the present invention, the system used for the aforementioned method includes: a raw material tank, a pretreatment tower, a drying tower, a primary distillation tower, an extractive distillation tower, a solvent recovery tower, a refining distillation tower, a CHF3 recovery tank, a CF3I finished product tank, a solvent circulation tank, and a tail gas treatment tower. The purity of the CF3I finished product is ≥99.99%, and the total recovery rate is ≥98%. The purity of CHF3 is ≥99.5%, and the recovery rate is ≥95%.

[0019] Compared with the prior art, the method and system for purifying and recovering trifluoroiodomethane and trifluoromethane of the present invention have stable process, good product quality, and low impurity residue, achieving efficient separation and purification of trifluoroiodomethane and efficient recovery of trifluoromethane. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic flowchart of a method for purifying and recovering trifluoroiodomethane and trifluoromethane in one embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments disclosed herein. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0023] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for purifying trifluoroiodomethane and recovering CHF3 from it. This method solves the problems in the prior art, such as the difficulty in achieving a purity of 99.99% for crude CF3I (containing about 60% CHF3), the inability to effectively recover CHF3 at high content, the difficulty in simultaneously removing multiple impurities such as CO, N2, and O2, resource waste, and high cost. This invention improves the purity of CF3I from 20% to 99.99%, while efficiently recovering high-purity CHF3, simultaneously removing various impurities, improving resource utilization, reducing production costs, and meeting the needs of large-scale industrial applications.

[0024] To achieve the above objectives, this invention discloses a method for purifying and recovering trifluoroiodomethane and CHF3 therefrom, specifically comprising the following steps:

[0025] 1. Pretreatment process

[0026] Crude trifluoroiodomethyl 20% purity (CF3I) raw material (containing approximately 60% CHF3, and CO, N2, O2, CO2, CF4, C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F) 10 Impurities such as C4F8, HF, HI, and CH3I, totaling approximately 20%, are introduced into a pretreatment tower. An alkaline aqueous solution is then introduced into the pretreatment tower for washing to remove acidic impurities (HF, HI, etc.) from the raw material. The alkaline aqueous solution is an aqueous solution of alkali metal carbonates or alkali metal hydroxides with a concentration of 0.05-10% (mass fraction), preferably a potassium hydroxide aqueous solution with a concentration of 1-5% (mass fraction). After washing, the material is sent to a dryer and dried by molecular sieve adsorption to remove moisture from the material. After drying, the moisture content in the material is ≤10ppm, resulting in pretreated material (CF3I purity maintained at 18-22%, CHF3 content maintained at 58-62%, removing acidic impurities and trace amounts of moisture; inert impurities such as CO, N2, and O2, as well as low-boiling-point impurities such as CF4, are temporarily retained in the material).

[0027] The preferred molecular sieve is 3A or 4A, with an adsorption temperature of 20-30℃ and a space velocity of 100-300 / h to ensure sufficient removal of moisture and avoid corrosion or affecting the separation effect during subsequent vacuum distillation. It can also adsorb some trace amounts of CH3I impurities.

[0028] 2. Primary distillation and separation process

[0029] The pretreated material is fed into a primary distillation column for vacuum distillation to separate and remove low-boiling-point light component impurities (other light components besides CHF3, such as CO, N2, O2, CO2, CF4, etc.) and high-boiling-point heavy component impurities (such as C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F). 10 The operating conditions for the primary distillation column are: top pressure 0.05-0.1 MPa, top temperature -85-75℃, bottom temperature 20-40℃, and reflux ratio 2-5:1. The primary distillation column discharges low-boiling-point light component impurities (CO, N2, O2, CO2, CF4, etc.) from the top and high-boiling-point heavy component impurities (C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F4, etc.) from the bottom. 10 (C4F8, etc.), a mixture rich in CF3I and CHF3 is collected from the middle of the column (CF3I purity increased to 35-45%, CHF3 content adjusted to 55-65%, trace amounts of CH3I residue). Heavy components and impurities in the bottom of the column can be further processed to recover CF3I, reducing losses.

[0030] 3. Extractive distillation separation of CHF3

[0031] The mixture collected from the middle of the primary distillation column (containing 55-65% CHF3) is fed into an extractive distillation column. Extraction solvent is continuously added to the top of the column. By altering the relative volatility of CF3I and CHF3 through the extractant, the separation problem at high CHF3 content is solved, achieving efficient separation of the two. The extraction solvent is selected from ketone or acetate solvents, preferably acetone or ethyl acetate. The mass ratio of extraction solvent to the mixture is adjusted to 2-4:1 (to meet the separation requirements of high CHF3 content). The operating conditions of the extractive distillation column are: top pressure 0.1-0.2 MPaA, top temperature -45 to 35℃, bottom temperature 40-60℃, and reflux ratio 3-6:1.

[0032] High-purity CHF3 (purity ≥99.5%) is collected from the top of the extractive distillation column, condensed, and then sent to the CHF3 recovery tank for storage, with a CHF3 recovery rate ≥95%. The mixture rich in CF3I, extraction solvent, and trace amounts of CH3I is collected from the bottom of the column and sent to the solvent recovery column.

[0033] The operating conditions of the solvent recovery tower are as follows: top pressure 0.1 MPaA, top temperature 50-70℃, bottom temperature 80-100℃, reflux ratio 1-2:1; the recovered extraction solvent collected from the top of the tower is cooled and recycled to the extractive distillation tower for reuse; crude CF3I (purity ≥99.5%, trace CH3I residue) is collected from the bottom of the tower.

[0034] 4. Deep purification process

[0035] The crude CF3I product collected from the bottom of the solvent recovery tower is fed into a refining distillation tower for deep vacuum distillation to remove trace residual impurities (such as trace amounts of CHF3, CH3I, etc.). The operating conditions of the refining distillation tower are: top pressure 0.02-0.05 MPaA, top temperature -35 to 25℃, bottom temperature 30-50℃, and reflux ratio 5-8:1.

[0036] Trace amounts of residual impurities (trace amounts of CHF3, CH3I, etc.) are collected from the top of the refining distillation column, while high-purity CF3I product (purity ≥99.99%) is collected from the bottom of the column. After condensation, it is sent to the CF3I finished product tank for storage, and the total recovery rate of CF3I is ≥98%.

[0037] Trace impurities at the top of the column can be returned to the primary distillation column for reprocessing, thereby improving the CF3I recovery rate.

[0038] 5. Exhaust gas treatment process

[0039] The low-boiling-point light component impurities (CO, N2, O2, CO2, CF4, etc.) discharged from the top of the primary distillation column and the trace residual impurities (trace amounts of CHF3, CH3I, etc.) discharged from the top of the refining distillation column are fed into the tail gas treatment column and washed again with alkaline aqueous solution to remove acidic impurities and trace amounts of CF3I and CHF3. The treated tail gas (mainly inert gases such as CO, N2, and O2) meets the emission standards. The washing liquid can be returned to the pretreatment process for reuse, reducing wastewater discharge.

[0040] Example 1

[0041] The method for purifying trifluoroiodomethane and recovering CHF3 from it in this embodiment includes the following specific steps:

[0042] 1. Pretreatment process: Crude CF3I raw material with a purity of 20% (containing CHF3 60%, HF 50ppm, HI 30ppm, CH3I 20ppm, and CO, N2, O2, CO2, CF4, C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F) is processed. 10Impurities such as C4F8 (totaling approximately 19.99%) were introduced into a pretreatment tower, into which a 2% potassium hydroxide aqueous solution was introduced. The washing temperature was 15℃ and the pressure was 0.2MPaA. After washing, the material was sent to a dryer and dried by adsorption using 3A molecular sieves at an adsorption temperature of 25℃ and a space velocity of 100 / h. After drying, the material had a moisture content of 8ppm, a CF3I purity of 20%, and a CHF3 content of 59.8%. HF and HI impurities were removed, while inert impurities such as CO, N2, and O2, as well as other fluorine-containing impurities, were temporarily retained.

[0043] 2. Preliminary Distillation Separation Process: The pretreated material is fed into the preliminary distillation column. Operating conditions are: top pressure 0.08 MPa, top temperature -80℃, bottom temperature 30℃, reflux ratio 3:1. Light component impurities such as CO, N2, O2, CO2, and CF4 are discharged from the top, while C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, and C4F4 are discharged from the bottom. 10 High-boiling-point heavy component impurities such as C4F8 were removed, and a mixture was collected from the middle of the tower (CF3I purity 40%, CHF3 content 60%, trace CH3I residue).

[0044] 3. Extractive distillation separation of CHF3: The mixture is fed into an extractive distillation column. Acetone is added at the top of the column as the extraction solvent, with a solvent-to-mixture mass ratio of 3:1. The operating conditions of the extractive distillation column are: top pressure 0.15 MPaA, top temperature -40℃, bottom temperature 50℃, and reflux ratio 4:1. CHF3 (99.6% purity) is collected at the top of the column, condensed, and sent to a CHF3 recovery tank. The mixture at the bottom of the column is sent to a solvent recovery column. The operating conditions of the solvent recovery column are: top pressure 0.1 MPaA, top temperature 60℃, bottom temperature 90℃, and reflux ratio 1.5:1. The acetone solvent is recovered at the top of the column and recycled to the extractive distillation column. Crude CF3I (99.6% purity, with trace amounts of CH3I residue) is collected at the bottom of the column.

[0045] 4. Deep purification process: The crude CF3I is fed into a refining distillation column. Operating conditions: top pressure 0.03 MPaA, top temperature -30℃, bottom temperature 40℃, reflux ratio 6:1; trace residual impurities (trace amounts of CHF3 and CH3I) are discharged from the top of the column, and the CF3I product collected from the bottom of the column is tested to have a purity of 99.992% and sent to the finished product tank.

[0046] 5. Tail gas treatment process: The tail gas from the primary distillation column and the refining distillation column is fed into the tail gas treatment column and washed with a 2% potassium hydroxide aqueous solution. After treatment, the tail gas (mainly CO, N2, and O2) meets the emission standards, and the washing liquid is returned to the pretreatment column for reuse.

[0047] In this embodiment, the total recovery rate of CF3I was 98.2%, the recovery rate of CHF3 was 95.3%, the recycling rate of the extraction solvent acetone was 99%, and the removal rate of various impurities was ≥99.9%.

[0048] Example 2

[0049] The method for purifying trifluoroiodomethane and recovering CHF3 from it in this embodiment includes the following specific steps:

[0050] 1. Pretreatment process: Crude CF3I raw material with a purity of 20% (containing CHF3 58%, HF 40ppm, HI 25ppm, CH3I 15ppm, and CO, N2, O2, CO2, CF4, C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F) is processed. 10 Impurities such as C4F8 (totaling approximately 21.9348%) were introduced into a pretreatment tower, into which a 3% sodium hydroxide aqueous solution was introduced. The washing temperature was 10℃ and the pressure was 0.15MPaA. After washing, the material was sent to a dryer and dried by adsorption using 4A molecular sieves at an adsorption temperature of 22℃ and a space velocity of 200 / h. After drying, the material had a moisture content of 7ppm, a CF3I purity of 20.1%, and a CHF3 content of 57.8%. HF and HI impurities were removed, while other impurities were temporarily retained.

[0051] 2. Preliminary Distillation Separation Process: The pretreated material is fed into the preliminary distillation column. Operating conditions are: top pressure 0.06 MPaA, top temperature -78℃, bottom temperature 25℃, reflux ratio 4:1. Light component impurities such as CO, N2, O2, CO2, and CF4 are discharged from the top, while C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, and C4F4 are discharged from the bottom. 10 High-boiling-point heavy component impurities such as C4F8 were removed, and the mixture was collected from the middle of the tower (CF3I purity 42%, CHF3 content 58%, trace CH3I residue).

[0052] 3. Extractive distillation separation of CHF3: The mixture is fed into an extractive distillation column, with ethyl acetate added at the top as the extraction solvent. The mass ratio of extraction solvent to mixture is 2.5:1. The operating conditions of the extractive distillation column are: top pressure 0.12 MPaA, top temperature -38℃, bottom temperature 45℃, and reflux ratio 5:1. CHF3 (99.7% purity) is collected at the top of the column, condensed, and sent to the CHF3 recovery tank. The mixture at the bottom of the column is sent to the solvent recovery column. The operating conditions of the solvent recovery column are: top pressure 0.1 MPaA, top temperature 55℃, bottom temperature 85℃, and reflux ratio 1.2:1. The ethyl acetate solvent is recovered at the top of the column and recycled to the extractive distillation column. Crude CF3I (99.7% purity, with trace amounts of CH3I residue) is collected at the bottom of the column.

[0053] 4. Deep purification process: The crude CF3I is fed into a refining distillation column. Operating conditions: top pressure 0.04 MPaA, top temperature -28℃, bottom temperature 45℃, reflux ratio 7:1; trace residual impurities (trace amounts of CHF3 and CH3I) are discharged from the top of the column, and the CF3I product collected from the bottom of the column is tested to have a purity of 99.993% and sent to the finished product tank.

[0054] 5. Tail gas treatment process: The tail gas from the primary distillation column and the refining distillation column is fed into the tail gas treatment column and washed with a 3% sodium hydroxide aqueous solution. After treatment, the tail gas meets the emission standards, and the washing liquid is returned to the pretreatment column for reuse.

[0055] In this embodiment, the total recovery rate of CF3I was 98.5%, the recovery rate of CHF3 was 95.8%, the recycling rate of the extraction solvent ethyl acetate was 98.8%, and the removal rate of various impurities was ≥99.9%.

[0056] Example 3

[0057] The method for purifying trifluoroiodomethane and recovering CHF3 from it in this embodiment includes the following specific steps:

[0058] 1. Pretreatment process: Crude CF3I raw material with a purity of 20% (containing CHF3 62%, HF 60ppm, HI 35ppm, CH3I 25ppm, and CO, N2, O2, CO2, CF4, C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, C4F) is processed. 10 Impurities such as C4F8 (totaling approximately 17.9049%) were introduced into a pretreatment tower, into which a 4% sodium carbonate aqueous solution was introduced. The washing temperature was 20℃ and the pressure was 0.25MPaA. After washing, the material was sent to a dryer and dried by adsorption using 3A molecular sieves at an adsorption temperature of 28℃ and a space velocity of 300 / h. After drying, the material had a moisture content of 9ppm, a CF3I purity of 19.8%, and a CHF3 content of 61.8%. HF and HI impurities were removed, while other impurities were temporarily retained.

[0059] 2. Preliminary Distillation Separation Process: The pretreated material is fed into the preliminary distillation column. Operating conditions are: top pressure 0.09 MPaA, top temperature -82℃, bottom temperature 35℃, reflux ratio 2.5:1. Light component impurities such as CO, N2, O2, CO2, and CF4 are discharged from the top, while C2F6, C3F8, C2HF5, C2F5I, CHF2CHF2, and C4F4 are discharged from the bottom. 10 High-boiling-point heavy component impurities such as C4F8 were removed, and the mixture was collected from the middle of the tower (CF3I purity 38%, CHF3 content 62%, trace CH3I residue).

[0060] 3. Extractive distillation separation of CHF3: The mixture is fed into an extractive distillation column. Butanone (MEK) is added at the top of the column as the extraction solvent, with a solvent-to-mixture mass ratio of 3.5:1. The operating conditions of the extractive distillation column are: top pressure 0.18 MPaA, top temperature -42℃, bottom temperature 55℃, and reflux ratio 4.5:1. CHF3 (99.5% purity) is collected at the top of the column, condensed, and sent to a CHF3 recovery tank. The mixture from the bottom of the column is sent to a solvent recovery column. The operating conditions of the solvent recovery column are: top pressure 0.1 MPaA, top temperature 65℃, bottom temperature 95℃, and reflux ratio 1.8:1. The MEK solvent is recovered at the top of the column and recycled to the extractive distillation column. Crude CF3I (99.5% purity, with trace amounts of CH3I residue) is collected from the bottom of the column.

[0061] 4. Deep purification process: The crude CF3I is fed into a refining distillation column. Operating conditions: top pressure 0.035 MPaA, top temperature -32℃, bottom temperature 38℃, reflux ratio 6.5:1; trace residual impurities (trace amounts of CHF3 and CH3I) are discharged from the top of the column, and the CF3I product collected from the bottom of the column is tested to have a purity of 99.991% and sent to the finished product tank.

[0062] 5. Tail gas treatment process: The tail gas from the primary distillation column and the refining distillation column is fed into the tail gas treatment column and washed with a 4% sodium carbonate aqueous solution. After treatment, the tail gas meets the emission standards, and the washing liquid is returned to the pretreatment column for reuse.

[0063] In this embodiment, the total recovery rate of CF3I was 98.1%, the recovery rate of CHF3 was 95.1%, the recycling rate of the extraction solvent methyl ethyl ketone was 99.2%, and the removal rate of various impurities was ≥99.9%.

[0064] Example 4

[0065] The only difference between this embodiment and Example 2 is that the extraction solvent in the extractive distillation separation of CHF3 is a mixture of acetone and ethyl acetate with a volume ratio of 0.5:1.

[0066] In this embodiment, the total recovery rate of CF3I was 98.6%, the recovery rate of CHF3 was 95.7%, the recycling rate of the extraction solvent ethyl acetate was 98.9%, and the removal rate of various impurities was ≥99.9%.

[0067] Example 5

[0068] The only difference between this embodiment and Example 2 is that the extraction solvent in the extractive distillation separation of CHF3 is a mixture of acetone and ethyl acetate with a volume ratio of 1.8:1.

[0069] In this embodiment, the total recovery rate of CF3I was 98.4%, the recovery rate of CHF3 was 95.6%, the recycling rate of the extraction solvent ethyl acetate was 98.7%, and the removal rate of various impurities was ≥99.9%.

[0070] Example 6

[0071] The only difference between this embodiment and Embodiment 2 is that the extraction solvent in the extractive distillation separation of CHF3 is a mixture of acetone and ethyl acetate with a volume ratio of 1.1:1.

[0072] In this embodiment, the total recovery rate of CF3I was 99.3%, the recovery rate of CHF3 was 96.1%, the recycling rate of the extraction solvent ethyl acetate was 99.9%, and the removal rate of various impurities was ≥99.9%.

[0073] In summary, the methods and systems for the purification and recovery of trifluoroiodomethane and trifluoromethane have the following advantages:

[0074] 1) Significant purification effect: Targeting the characteristics of crude CF3I (purity 20%, containing about 60% CHF3, and various impurities such as CO, N2, and O2), the four-stage process of "pretreatment-initial distillation-extractive distillation-deep purification" works synergistically to not only break through the technical bottleneck of purifying low-purity CF3I with high CHF3 content to 99.99% high purity, but also simultaneously and efficiently remove various impurities such as CO, N2, O2, and CF4, solving the problems of insufficient purification purity, difficulty in CHF3 separation, and incomplete impurity removal in existing technologies.

[0075] 2) Achieve efficient recovery of CHF3: Optimize extraction distillation process parameters and extraction solvent ratio to meet the high content separation requirements of approximately 60% CHF3, accurately separate CF3I and CHF3, and recover CHF3 products with a purity of ≥99.5%, realize the recycling of resources, avoid the problem of waste of high-content CHF3, significantly improve the comprehensive utilization rate of raw materials, and reduce production costs.

[0076] 3) Low loss and high efficiency: The total recovery rate of CF3I is ≥98% and the recovery rate of CHF3 is ≥95% throughout the process; the extraction solvent can be recycled, reducing solvent consumption; the operating conditions of each process are mild, and the vacuum distillation method is suitable for the separation of high CHF3 content and the removal of various impurities, which is easy to control and suitable for industrial-scale production.

[0077] 4) Environmental protection and energy saving: The pretreatment and tail gas treatment processes use alkaline aqueous solutions for washing, which can effectively remove acidic impurities and reduce equipment corrosion. At the same time, the washing liquid can be recycled to reduce wastewater discharge. The entire distillation process adopts reduced pressure operation to reduce energy consumption. The tail gas is treated to meet emission standards, which is in line with the development trend of energy conservation and environmental protection.

[0078] 5) Stable and reliable process: The processes are closely linked, and the operating parameters are optimized for scenarios with high CHF3 content and many impurities, making them highly controllable. Multi-stage separation ensures stable product purity and recovery rate, solving the problems of unstable process, large fluctuations in product quality, and incomplete removal of impurities in existing technologies.

[0079] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0080] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for purifying and recovering trifluoroiodomethane and trifluoromethane, characterized in that, Includes the following steps: (1) Pretreatment: Crude CF3I is washed with alkali to remove acid and dried by molecular sieve; (2) Initial distillation: light and heavy components are removed by vacuum distillation, and the first mixture is collected from the middle section; (3) Extractive distillation: The first mixture is extracted and distilled in a solvent to separate the first CHF3 material with high purity, the first impurity and the recovered solvent; (4) Solvent recovery: The recovered solvent is refluxed and distilled to obtain the solvent to be recycled and crude CF3I; (5) Deep refining: vacuum distillation of crude CF3I and / or the first CHF3 feedstock to obtain ≥99.99% CF3I finished product; (6) Exhaust gas treatment: Alkali washing is performed on light components and / or the first impurity, and the emissions are discharged after alkali washing meets the standards.

2. The method according to claim 1, characterized in that, The alkaline solution used in the alkaline washing is an alkali metal carbonate, alkali metal bicarbonate, or alkali metal hydroxide, and the concentration of the alkaline solution is 0.05-10 wt.%.

3. The method according to claim 2, characterized in that, The alkali metal is sodium or potassium.

4. The method according to claim 1, characterized in that, The conditions for drying the molecular sieve are: temperature 20-30℃, space velocity 100-300 / h, and the molecular sieve used is 3A or 4A molecular sieve.

5. The method according to claim 1, characterized in that, The initial distillation conditions are: pressure 0.05-0.1 MPa, reflux ratio (2-5):

1.

6. The method according to claim 1, characterized in that, The solvent / material mass ratio during the extractive distillation is (2-4):

1.

7. The method according to claim 6, characterized in that, The solvent is at least one of ketones and acetates.

8. The method according to claim 1, characterized in that, The conditions for the extractive distillation are: pressure 0.1-0.2 MPaA, reflux ratio (3-6):

1.

9. The method according to claim 1, characterized in that, The conditions for vacuum distillation are: pressure 0.02-0.05 MPaA, reflux ratio (5-8):

1.

10. A system for use in the method of any one of claims 1-9, characterized in that, include: Raw material tank, pretreatment tower, drying tower, primary distillation tower, extractive distillation tower, solvent recovery tower, refining distillation tower, CHF3 recovery tank, CF3I finished product tank, solvent circulation tank, and tail gas treatment tower.

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