A method for the photo-thermal preparation of 2-bromoheptafluoropropane
The photothermal synergistic method for preparing 2-bromoheptafluoropropane solves the problems of insufficient purity and equipment corrosion in traditional methods, and achieves the preparation of high-purity products, which are suitable for drug synthesis and semiconductor cleaning.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG HAIHUA GRP CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies make it difficult to prepare high-purity 2-bromoheptafluoropropane, and traditional methods suffer from problems such as high-temperature reactions, equipment corrosion, environmental pressure, and insufficient purity, which affect drug synthesis and semiconductor cleaning effects.
2-Bromoheptafluoropropane was prepared by a photothermal synergistic method. The CH bond was broken by ultraviolet light, and the reaction temperature was reduced and the purity was improved by combining silica defluorination, water washing, alkali washing and distillation.
It achieves a purity of 99.91-99.98% for 2-bromoheptafluoropropane, reducing energy consumption and equipment corrosion, improving economic efficiency, and is suitable for drug synthesis and semiconductor cleaning.
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Figure CN121698718B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluorine-containing organic intermediate preparation technology, specifically to a method for photothermal preparation of 2-bromoheptafluoropropane. Background Technology
[0002] 2-Bromoheptafluoropropane is an important bromine-based fine chemical, currently mainly used to replace 2-iodoheptafluoropropane in the synthesis of pharmaceutical and pesticide intermediates. 2-Bromoheptafluoropropane plays a crucial role as a raw material intermediate in the synthesis of bromofenofibrate. As pharmaceutical and pesticide companies attempt to introduce heptafluoroisopropyl groups into pharmaceutical and pesticide molecular formulas using 2-Bromoheptafluoropropane, and to replace 2-iodoheptafluoropropane in reactions as much as possible, they aim to synthesize more key pharmaceutical and pesticide intermediates.
[0003] The production and storage conditions for 2-bromoheptafluoropropane are demanding, resulting in a very limited number of manufacturers worldwide. There are two main synthetic routes for 2-bromoheptafluoropropane: the hexafluoropropene method and the heptafluoropropane method. The hexafluoropropene method uses hexafluoropropene as a raw material, first reacting it with bromine to produce 1,2-dibromohexafluoropropane; 1,2-dibromohexafluoropropane then undergoes a fluorination reaction with fluorinating agents such as potassium fluoride to produce 2-bromoheptafluoropropane. However, this method is complex, KF is susceptible to moisture and toxic, and requires a large amount of solvent, posing significant environmental pressure. For example, Chinese patent document CN117986079A discloses a high-throughput microchannel continuous process for preparing 2-bromoheptafluoropropane, achieving a purity of 99.5%.
[0004] The heptafluoropropane process uses heptafluoropropane as a raw material, which undergoes a direct bromination reaction with bromine at high temperature to produce 2-bromoheptafluoropropane. For example, Chinese patent document CN101768047A discloses a method for producing 2-bromoheptafluoropropane. This method has a short process flow, does not require solvents, and has great industrialization potential. When the reaction temperature is between 450 and 500 degrees Celsius, the conversion rate of the raw material heptafluoropropane is 52.7%. This patent does not describe the post-treatment process of the reaction solution.
[0005] When 2-bromoheptafluoropropane is used as a raw material in drug synthesis, if its purity does not reach 99.9% or higher, potentially toxic impurities may be introduced during the synthesis process due to residual byproducts or incompletely reacted intermediates. These impurities may affect the purity of the final product through mechanisms such as co-crystallization and complexation, thereby posing a risk to the safety and efficacy of the drug formulation and potentially causing adverse reactions. Furthermore, 2-bromoheptafluoropropane with a purity below 99.9% cannot be used in surface cleaning processes for semiconductor wafers and electronic components. Low-purity substances may leave chemical residues during cleaning, leading to surface corrosion or functional damage to precision devices. 2-bromoheptafluoropropane products prepared using the traditional hexafluoropropylene and heptafluoropropane methods both have a purity below 99.9%, making them unsuitable as raw materials for drug synthesis and unsuitable for surface cleaning processes for semiconductor wafers and electronic components. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing high-purity 2-bromoheptafluoropropane by photothermal reaction. This method can not only reduce the bromination reaction temperature and improve the conversion rate of heptafluoropropane, but also increase the purity of 2-bromoheptafluoropropane product to 99.91~99.98%. It can be used as a raw material for drug synthesis and as a surface cleaning process for semiconductor wafers and electronic components.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A method for photothermal preparation of 2-bromoheptafluoropropane, the specific steps of which are as follows:
[0009] Heptafluoropropane and bromine are vaporized separately, mixed and preheated, and then passed into a pipeline photothermal reactor. Under light and heating conditions, a bromination reaction is carried out to obtain a mixed gas containing 2-bromoheptafluoropropane. The mixed gas containing 2-bromoheptafluoropropane is then passed into a defluorinator containing silica for defluorination. After washing with water, alkali washing, dehydration, compression, and condensation, a condensate is obtained. Unreacted heptafluoropropane is then recovered by primary distillation, and impurities are removed by secondary distillation. After drying and dehydration, high-purity 2-bromoheptafluoropropane is obtained.
[0010] Preferably, the mass ratio of heptafluoropropane to bromine is 0.6–1.2:1; the preheating temperature is 100–150°C; the bromination reaction temperature is 200–300°C; the bromination reaction time is 10–50 s; and the illumination power is 400–600 W with a wavelength of 380–400 nm.
[0011] Preferably, the alkaline washing involves washing the mixed gas after water washing with a sodium hydroxide solution or potassium hydroxide solution with a concentration of 10-32 wt%.
[0012] Preferably, the compression pressure is 0.2 to 1 MPa and the condensation temperature is -20 to 0°C.
[0013] Preferably, the first-stage distillation involves passing the condensate into a first-stage distillation column to distill and obtain heptafluoropropane condensate and first-stage heavy component condensate. The heptafluoropropane condensate is collected from the top of the distillation column, a portion of which is refluxed back into the first-stage distillation column, while the remainder is recycled. The reflux ratio is controlled at 2–5:1. More preferably, the bottom temperature of the first-stage distillation column is 50–120°C, the temperature of the top condenser is -20–10°C, and the pressure inside the column is 0.2–1 MPa.
[0014] Preferably, the secondary distillation involves passing the condensate of the primary heavy components into a secondary distillation column, distilling to obtain 2-bromoheptafluoropropane condensate and distillation residue. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column, a portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is dried and dehydrated to prepare high-purity 2-bromoheptafluoropropane, with the reflux ratio controlled at 3–5:1. More preferably, the bottom temperature of the secondary distillation column is 90–150°C, the temperature of the top condenser is 0–30°C, and the pressure inside the column is 0.2–1 MPa.
[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0016] (1) The traditional heptafluoropropane method requires a high bromination reaction temperature, mainly because the CH bond of heptafluoropropane has a high valence energy, requiring a very high temperature to break it and generate heptafluoropropane radicals. This invention utilizes a photothermal synergistic effect to generate bromine radicals through heat, and then uses ultraviolet light to induce the breaking of CH to generate heptafluoropropane radicals. The heptafluoropropane radicals combine with the bromine radicals to obtain the target product 2-bromoheptafluoropropane. This technology reduces the reaction temperature from the previous 450℃ to below 300℃, and increases the single-pass conversion rate of heptafluoropropane to over 80%. This not only reduces the corrosion resistance requirements of the equipment materials and lowers the investment cost, but also reduces the energy consumption, material consumption, and operating costs required for the reaction.
[0017] (2) The inventors found that a small number of side reactions occurred when 2-bromoheptafluoropropane was prepared by photothermal bromination, resulting in a small amount of hydrogen fluoride and dibromoheptafluoropropane in the reaction material after the reaction was completed.
[0018] Therefore, the impurities in the 2-bromoheptafluoropropane mixture prepared by the technical solution of this invention are hydrogen fluoride, hydrogen bromide, bromine, heptafluoropropane, and dibromohexafluoropropane. This invention removes hydrogen fluoride by reacting the obtained 2-bromoheptafluoropropane mixture with silica for defluorination. Hydrogen bromide and bromine are removed through water washing, alkali washing, and dehydration. Unreacted heptafluoropropane is recovered by primary distillation, and dibromohexafluoropropane is removed by secondary distillation. Finally, the mixture is dried and dehydrated to obtain a high-purity 2-bromoheptafluoropropane product with a purity of 99.91% to 99.98%.
[0019] (3) The present invention first removes low concentrations of hydrogen fluoride from the mixed gas through a defluorination reaction, thus avoiding corrosion of subsequent process equipment by hydrogen fluoride. At the same time, it solves the problem that it is difficult to separate hydrogen bromide and hydrogen fluoride by water washing and alkaline washing. After separating hydrogen bromide and hydrogen fluoride, they can be used to produce bromine, realize the recycling of bromine, and improve economic benefits.
[0020] (4) The present invention uses a water washing plus alkali washing process to remove hydrogen bromide from the mixed gas. Compared with the water washing process for removing hydrogen bromide, the present invention has a higher hydrogen bromide removal efficiency. Compared with the alkali washing process for removing hydrogen bromide, the present invention reduces alkali consumption and has higher economic benefits.
[0021] (5) The process of this invention will generate byproducts hydrogen fluoride and dibromohexafluoropropane. Currently, there is no literature reporting on the post-treatment process for the byproducts generated by this preparation process. This invention uses a two-stage distillation process to remove impurities from the mixed gas. The inventors found that the bottom temperature of the first-stage distillation column should be controlled between 50 and 120°C. If the bottom temperature is below 50°C, some heptafluoropropane will flow from the bottom of the first-stage distillation column to the second-stage distillation column, resulting in a decrease in the conversion rate and gas phase purity of heptafluoropropane. If the bottom temperature is above 120°C, some 2-bromoheptafluoropropane will flow out from the top of the first-stage distillation column, resulting in a decrease in the conversion rate and selectivity of heptafluoropropane. The bottom temperature of the second-stage distillation column should be controlled between 90 and 150°C. If the bottom temperature is below 90°C, some 2-bromoheptafluoropropane will flow out from the bottom of the second-stage distillation column, resulting in a decrease in the conversion rate of heptafluoropropane. If the bottom temperature is above 150°C, some heavy components will come out from the top of the column, resulting in a decrease in the purity of 2-bromoheptafluoropropane.
[0022] (6) Compared with the hexafluoropropylene method, the process of the present invention is simple, requiring only one bromination reaction to obtain the target compound, and does not require solvent or KF, thus having high atom economy. Attached Figure Description
[0023] Figure 1 This is a process flow diagram of a specific embodiment of the photothermal preparation method for 2-bromoheptafluoropropane according to the present invention;
[0024] Figure 2 This is a schematic diagram of a pipeline-type photothermal reactor structure used in a specific embodiment of the present invention. Detailed Implementation
[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.
[0026] See attached document Figure 1 One specific embodiment of the present invention includes the following steps: heptafluoropropane and bromine are vaporized in a vaporizer through a buffer tank and a metering tank, respectively, then mixed in a mixing vessel, preheated in a preheater, and then reacted in a photothermal reactor to generate a mixed gas containing 2-bromoheptafluoropropane. The mixed gas is cooled in a cooling water tank, hydrogen fluoride is removed by a defluorinator containing silica, then washed in a water washing spray tower, then washed in an alkaline washing tower to remove residual hydrogen bromide, then dehydrated in a cyclone dehydrator, then compressed by a compressor and condensed in a condenser. The generated condensate is then purified by distillation in a primary distillation tower and a secondary distillation tower, and finally dried in a drying tower and bottled to obtain a high-purity 2-bromoheptafluoropropane product.
[0027] In the following embodiments of the present invention, the tubular photothermal reactor comprises a tubular reactor, a light source, a heating source, and peripheral structures. The reaction tube uses a quartz tube as the reaction layer, the heat source uses electric heating to heat the reaction layer from within, an insulation layer is provided outside the reaction layer, and the light source irradiates inward from an external viewing window on the reaction shell. (Refer to the attached diagram.) Figure 2 . Example 1
[0028] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then passed into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 0.6:1, the preheating temperature is 100℃, the bromination reaction temperature is 200℃, the light source is an LED lamp with a power of 400W and a wavelength of 380nm, and the reaction residence time is 50s to obtain the first mixed gas.
[0029] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0030] (3) The second mixed gas is washed with water, washed with alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of the washing water to heptafluoropropane is 5:1, and the alkali solution is a 10wt% sodium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 1:1. The bromine water mixture is recovered for the production of bromine and recycled.
[0031] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 0.2 MPa and the condensation temperature is controlled at -20℃. The condensate is sent to the first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 50℃, the top condenser temperature is -20℃, and the pressure inside the column is 0.2 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 2:1.
[0032] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 90°C, the temperature of the top condenser is 0°C, and the pressure inside the column is 0.2 MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 3:1.
[0033] Based on sampling and testing, the conversion rate of heptafluoropropane was 84.5%, and the selectivity was 99.4%.
[0034] The purity of 2-bromoheptafluoropropane was 99.98% as determined by gas chromatography, and the water content was 32 ppm as determined by a moisture analyzer. Example 2
[0035] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then passed into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 1.2:1, the preheating temperature is 150℃, the bromination reaction temperature is 300℃, the light source is an LED lamp with a power of 600W and a wavelength of 400nm, and the reaction residence time is 10s to obtain the first mixed gas.
[0036] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0037] (3) The second mixed gas is washed with water, washed with alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of the washing water to heptafluoropropane is 5:1, and the alkali solution is a 10wt% sodium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 1:1. The bromine water mixture is recovered for the production of bromine and recycled.
[0038] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 1 MPa and the condensation temperature is controlled at 0℃. The condensate is sent to the first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 120℃, the top condenser temperature is 10℃, and the pressure inside the column is 1 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 5:1.
[0039] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 150°C, the temperature of the top condenser is 30°C, and the pressure inside the column is 1MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed back into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 5:1.
[0040] Based on sampling and testing, the conversion rate of heptafluoropropane was 80.3%, and the selectivity was 99.3%.
[0041] The purity of 2-bromoheptafluoropropane was 99.91% as determined by gas chromatography, and the water content was 35 ppm as determined by a moisture analyzer. Example 3
[0042] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then passed into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 1:1, the preheating temperature is 120℃, the reaction temperature is 250℃, the light source is an LED lamp with a power of 500W and a wavelength of 390nm, and the reaction residence time is 30s to obtain the first mixed gas.
[0043] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0044] (3) The second mixed gas is washed with water, alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of water to heptafluoropropane is 5:1, and the alkali solution is a 20wt% potassium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 0.5:1. The bromine water mixture is oxidized with chlorine to oxidize bromide ions to bromine. Then, it is blown out with air, distilled, and condensed to obtain bromine for recycling.
[0045] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 0.5 MPa and the condensation temperature is controlled at -10℃. The condensate is sent to the first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 70℃, the top condenser temperature is 0℃, and the pressure inside the column is 0.5 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 3:1.
[0046] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 120°C, the temperature of the top condenser is 20°C, and the pressure inside the column is 0.5 MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 4:1.
[0047] Based on sampling and testing, the conversion rate of heptafluoropropane was 83.2%, and the selectivity was 99.1%.
[0048] The purity of 2-bromoheptafluoropropane was 99.94% as determined by gas chromatography, and the water content was 37 ppm as determined by a moisture analyzer. Example 4
[0049] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then introduced into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 0.8:1, the preheating temperature is 130℃, the reaction temperature is 280℃, the light source is an LED lamp with a power of 450W and a wavelength of 395nm, and the reaction residence time is 40s to obtain the first mixed gas.
[0050] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0051] (3) The second mixed gas is washed with water, alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of water to heptafluoropropane is 5:1, and the alkali solution is a 32wt% sodium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 0.2:1. The bromine water mixture is oxidized with chlorine to oxidize bromide ions to bromine, and then blown out with air, distilled, and condensed to obtain bromine for recycling.
[0052] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 0.3 MPa and the condensation temperature is controlled at -15℃. The condensate is sent to a first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 100℃, the top condenser temperature is -10℃, and the pressure inside the column is 0.3 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 4:1.
[0053] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 130°C, the temperature of the top condenser is 20°C, and the pressure inside the column is 0.3 MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 3:1.
[0054] Based on sampling and testing, the conversion rate of heptafluoropropane was 83.6%, and the selectivity was 99.1%.
[0055] The purity of 2-bromoheptafluoropropane was 99.95% as determined by gas chromatography, and the water content was 33 ppm as determined by a moisture analyzer. Example 5
[0056] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then passed into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 0.9:1, the preheating temperature is 120℃, the reaction temperature is 300℃, the light source is an LED lamp with a power of 400W and a wavelength of 390nm, and the reaction residence time is 30s to obtain the first mixed gas.
[0057] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0058] (3) The second mixed gas is washed with water, alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of water to heptafluoropropane is 5:1, and the alkali solution is a 32wt% sodium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 0.2:1. The bromine water mixture is oxidized with chlorine to oxidize bromide ions to bromine, and then blown out with air, distilled, and condensed to obtain bromine for recycling.
[0059] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 0.4 MPa and the condensation temperature is controlled at -10℃. The condensate is sent to a first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 110℃, the top condenser temperature is -5℃, and the pressure inside the column is 0.4 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 3:1.
[0060] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 110°C, the temperature of the top condenser is 15°C, and the pressure inside the column is 0.4 MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 3:1.
[0061] Based on sampling and testing, the conversion rate of heptafluoropropane was 81.3%, and the selectivity was 99.5%.
[0062] The purity of 2-bromoheptafluoropropane was 99.96% as determined by gas chromatography, and the water content was 38 ppm as determined by a moisture analyzer. Example 6
[0063] (1) Heptafluoropropane and bromine are vaporized separately, then mixed and preheated, and then passed into a pipeline photothermal reactor for bromination reaction. The mass ratio of heptafluoropropane to bromine is 1:1, the preheating temperature is 130℃, the reaction temperature is 280℃, the light source is an LED lamp with a power of 450W and a wavelength of 390nm, and the reaction residence time is 30s to obtain the first mixed gas.
[0064] (2) The first mixed gas is passed into a defluorinator containing silicon dioxide to carry out a defluorination reaction and obtain the second mixed gas;
[0065] (3) The second mixed gas is washed with water, alkali, and dehydrated to obtain a third mixed gas and a bromine water mixture. The mass ratio of water to heptafluoropropane is 5:1, and the alkali solution is a 32wt% sodium hydroxide aqueous solution with a mass ratio of alkali solution to heptafluoropropane of 0.2:1. The bromine water mixture is oxidized with chlorine to oxidize bromide ions to bromine, and then blown out with air, distilled, and condensed to obtain bromine for recycling.
[0066] (4) After the third mixed gas is compressed and condensed, a condensate is obtained. The compressor pressure is controlled at 0.5 MPa and the condensation temperature is controlled at -5℃. The condensate is sent to the first-stage distillation column for distillation. The bottom temperature of the first-stage distillation column is 120℃, the top condenser temperature is 0℃, and the pressure inside the column is 0.5 MPa. Heptafluoropropane condensate and first-stage heavy component condensate are obtained. The heptafluoropropane condensate is collected from the top of the distillation column. A portion of the heptafluoropropane condensate is returned to the first-stage distillation column, and the remaining heptafluoropropane condensate is recovered for the production of heptafluoropropane and recycled. The reflux ratio is controlled at 3:1.
[0067] (5) The condensate of the primary heavy component is fed into a secondary distillation column for distillation. The temperature of the bottom of the secondary distillation column is 140°C, the temperature of the top condenser is 25°C, and the pressure inside the column is 0.5 MPa. 2-bromoheptafluoropropane condensate and distillation residue are obtained. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column. A portion of the 2-bromoheptafluoropropane condensate is refluxed into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is sent to a drying column for drying and dehydration to obtain high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 3:1.
[0068] Based on sampling and testing, the conversion rate of heptafluoropropane was 80.7%, and the selectivity was 99.4%.
[0069] The purity of 2-bromoheptafluoropropane was 99.93% as determined by gas chromatography, and the water content was 36 ppm as determined by a moisture analyzer. Comparative Example 1
[0070] The difference from Example 1 is that the light source is an LED lamp with a power of 400W and a wavelength of 420nm, a heptafluoropropane conversion rate of 68.3%, and a selectivity of 99.4%. Comparative Example 2
[0071] The difference from Example 1 is that the light source is an LED lamp with a power of 400W, a wavelength of 360nm, a heptafluoropropane conversion rate of 81.2%, and a selectivity of 98.1%. Comparative Example 3
[0072] The difference from Example 1 is that the bromination reaction temperature is 150°C, the heptafluoropropane conversion rate is 61.4%, and the selectivity is 99.3%. Comparative Example 4
[0073] The difference from Example 1 is that the bromination reaction temperature is 350°C, the heptafluoropropane conversion rate is 85.4%, and the selectivity is 97.7%.
[0074]
[0075] As can be seen from Table 1, the conversion rate of heptafluoropropane obtained in the examples is 80.3-84.5%, and the selectivity is 99.1-99.5%.
[0076] In Comparative Example 1, increasing the wavelength of the light source leads to a decrease in the energy of the light source, which affects the generation of bromine free radicals and thus reduces the conversion rate of heptafluoropropane.
[0077] In Comparative Example 2, reducing the wavelength of the light source leads to an increase in the energy of the light source, causing the product 2-bromoheptafluoropropane to decompose, thereby reducing the selectivity of 2-bromoheptafluoropropane.
[0078] Similarly, decreasing the reaction temperature leads to a decrease in the conversion rate of heptafluoropropane. Increasing the reaction temperature leads to a slight increase in the conversion rate of heptafluoropropane, but a decrease in selectivity.
[0079] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.
Claims
1. A method for the photo-thermal preparation of 2-bromoheptafluoropropane, characterized in that, Includes the following steps: Heptafluoropropane and bromine are vaporized separately, mixed and preheated, and then passed into a pipeline photothermal reactor. Under light and heating conditions, a bromination reaction is carried out to obtain a mixed gas containing 2-bromoheptafluoropropane. The mixed gas containing 2-bromoheptafluoropropane is then passed into a defluorinator containing silica for defluorination reaction. After washing with water, alkali washing, dehydration, compression, and condensation, a condensate is obtained. Unreacted heptafluoropropane is then recovered by primary distillation, and impurities are removed by secondary distillation. After drying and dehydration, high-purity 2-bromoheptafluoropropane is obtained. The mass ratio of heptafluoropropane to bromine is 0.6–1.2:1; the preheating temperature is 100–150°C; the bromination reaction temperature is 200–300°C; the bromination reaction time is 10–50 s; and the illumination power is 400–600 W with a wavelength of 380–400 nm.
2. The method of photo-thermal preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The alkaline washing involves washing the mixed gas after water washing with a sodium hydroxide solution or potassium hydroxide solution with a concentration of 10-32 wt%.
3. The method for photothermal preparation of 2-bromoheptafluoropropane according to claim 1, characterized in that, The compression pressure is 0.2 to 1 MPa, and the condensation temperature is -20 to 0℃.
4. The method of photo-thermal production of 2-bromoheptafluoropropane according to claim 1, wherein, The first-stage distillation involves passing the condensate into a first-stage distillation column to distill and obtain heptafluoropropane condensate and first-stage heavy component condensate. The heptafluoropropane condensate is collected from the top of the distillation column, a portion of the heptafluoropropane condensate is refluxed back into the first-stage distillation column, and the remaining heptafluoropropane condensate is recycled. The reflux ratio is controlled at 2 to 5:
1.
5. The method for photothermal preparation of 2-bromoheptafluoropropane according to claim 4, characterized in that, The secondary distillation involves passing the condensate of the primary heavy components into a secondary distillation column to obtain 2-bromoheptafluoropropane condensate and distillation residue. The 2-bromoheptafluoropropane condensate is collected from the top of the secondary distillation column, a portion of which is refluxed back into the secondary distillation column, and the remaining 2-bromoheptafluoropropane condensate is dried and dehydrated to prepare high-purity 2-bromoheptafluoropropane. The reflux ratio is controlled at 3 to 5:
1.
6. The method of photo-thermal production of 2-bromoheptafluoropropane according to claim 4, wherein, The temperature of the reboiler in the first-stage distillation column is 50–120°C, the temperature of the top condenser is -20–10°C, and the pressure inside the column is 0.2–1 MPa.
7. The method of photo-thermal production of 2-bromoheptafluoropropane according to claim 5, wherein, The temperature of the bottom of the secondary distillation column is 90–150°C, the temperature of the top condenser is 0–30°C, and the pressure inside the column is 0.2–1 MPa.