Efficient separation method of tetrafluoropropanol

Abstract

The invention relates to the technical field of chemical separation, and discloses an efficient tetrafluoropropanol separation method which comprises the following steps: S1, mixing an aqueous solution containing tetrafluoropropanol with a green extractant hydroxyethyl glucosamide according to a mass ratio of 1: 0.5-1: 2, and stirring at 25-40 DEG C for 20-40 minutes to form a uniform mixed solution; s2, inputting the mixed solution obtained in the step S1 into an extractive distillation tower, collecting water vapor at the top of the tower, and obtaining a mixture of tetrafluoropropanol and the green extractant at the bottom of the tower; s3, the tower bottom mixture obtained in the step S2 is cooled to 30-50 DEG C, deionized water is added for layering, the upper layer is high-purity tetrafluoropropanol, and the lower layer is an aqueous solution containing a green extraction agent; and S4, recycling the green extraction agent. According to the method, hydroxyethyl glucosamide is used as a green extracting agent, and an extractive distillation process is combined, so that an azeotropic system of tetrafluoropropanol and water is effectively broken, and the purity of the separated TFP reaches 99.5%-99.9%.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical separation, and specifically to a method for efficient separation of tetrafluoropropanol. Background Art

[0002] Tetrafluoropropanol (2,2,3,3-tetrafluoro-1-propanol, abbreviated as TFP) is an important fluorine-containing compound and has received extensive attention due to its applications in pharmaceutical intermediates, pesticide synthesis, and electronic industry cleaning agents. Since TFP forms an azeotropic mixture with water (the azeotropic composition is approximately 72.5% TFP and 27.5% water, and the boiling point is approximately 365.7 K, 101.3 kPa), traditional distillation methods cannot effectively achieve separation. In the prior art, common separation methods include extractive distillation, azeotropic distillation, liquid-liquid extraction, and membrane separation. For example, extractive distillation often uses N-methylpyrrolidone (NMP) or N,N-dimethylformamide (DMF) as an auxiliary agent to separate TFP from water by changing the vapor-liquid equilibrium; azeotropic distillation uses chloroform or p-xylene as an azeotropic agent; liquid-liquid extraction utilizes pyridine-based ionic liquids to extract TFP; in membrane separation research, carbon nanotube membranes are used for the separation of the TFP-water system. However, the prior art has several deficiencies in practical applications. Extractive distillation with NMP or DMF as an auxiliary agent can achieve a certain degree of separation, but the purity of the obtained TFP is usually between 95% and 98%, which is difficult to meet the high-purity requirements. Moreover, the acute toxicity of NMP (LD50: 3914 mg / kg) is relatively high, and the recovery process requires high-temperature distillation or additional organic solvents, increasing the energy consumption (about 1.5 GJ / ton of TFP) and environmental burden. In azeotropic distillation, the use of azeotropic agents such as chloroform results in reduced operational safety and does not meet environmental protection requirements due to its strong toxicity (LD50: 908 mg / kg) and high volatility. The ionic liquids in liquid-liquid extraction are costly (hundreds of yuan per kilogram), and the extraction efficiency is limited by the TFP concentration range, making it difficult to apply on a large scale. Although membrane separation technology has certain potential, the preparation cost of carbon nanotube membranes is high, the lifespan is limited, and the separation efficiency is greatly affected by fluctuations in temperature and pore size parameters, with insufficient stability. These drawbacks limit the popularization and application of the prior art in industrial production. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a method for efficient separation of tetrafluoropropanol, which solves the problem that extractive distillation with NMP or DMF as an auxiliary agent can achieve a certain degree of separation, but the purity of the obtained TFP is usually between 95% and 98%, which is difficult to meet the high-purity requirements.

[0004] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for efficient separation of tetrafluoropropanol, comprising the following steps: S1. Mix the aqueous solution containing 2,3,3,3 - tetrafluoropropanol with the green extractant N - (2 - hydroxyethyl) - D - glucamine in a mass ratio of 1:0.5 - 1:2, and stir at 25 - 40 °C for 20 - 40 minutes to form a homogeneous mixture. The chemical structural formula of the N - (2 - hydroxyethyl) - D - glucamine is CH2OH-(CHOH)4-CONH-CH2CH2OH; S2. Input the mixture obtained in step S1 into an extractive distillation column, and carry out extractive distillation at a pressure of 50 - 101.3 kPa. The top temperature of the column is 80 - 100 °C, and the bottom temperature is 120 - 150 °C. Water vapor is collected at the top of the column, and a mixture of 2,3,3,3 - tetrafluoropropanol and the green extractant is obtained at the bottom of the column; S3. Cool the bottom mixture obtained in step S2 to 30 - 50 °C, add deionized water for liquid - liquid separation. The upper layer is high - purity 2,3,3,3 - tetrafluoropropanol, and the lower layer is an aqueous solution containing the green extractant; S4. Carry out vacuum distillation on the lower - layer aqueous solution obtained in step S3 at 40 - 60 °C and 0.01 - 0.03 MPa to recover the green extractant.

[0005] Preferably, in step S1, the mass fraction of 2,3,3,3 - tetrafluoropropanol in the aqueous solution containing 2,3,3,3 - tetrafluoropropanol is 10% - 80%, the mass ratio of the green extractant to the aqueous solution is 1:1, and the stirring speed is 200 - 500 rpm.

[0006] Preferably, the green extractant N - (2 - hydroxyethyl) - D - glucamine in step S1 is prepared by the following steps: S1 - 1. Mix D - glucose and ethanolamine in a molar ratio of 1:1.1 - 1:1.5, and stir and react at 50 - 70 °C for 3 - 5 hours; S1 - 2. Add the catalyst boron trifluoride to the product of step S1 - 1, and distill off the by - product water under a reduced pressure condition of 0.005 - 0.02 MPa; S1 - 3. Recrystallize the product of step S1 - 2 with ethanol to obtain N - (2 - hydroxyethyl) - D - glucamine with a purity ≥98%.

[0007] Preferably, in step S1 - 1, the molar ratio of D - glucose to ethanolamine is 1:1.2, the reaction temperature is 60 °C, and the reaction time is 4 hours.

[0008] Preferably, in step S2, the extractive distillation column is a packed column, the packing is selected from θ - rings or Raschig rings, the column height is 2 - 5 m, and the column diameter is 0.5 - 1 m.

[0009] Preferably, in step S2, the pressure of extractive distillation is 80 kPa, the top temperature of the column is 85 - 90 °C, and the bottom temperature is 130 - 140 °C.

[0010] Preferably, in step S3, the mass ratio of deionized water added to the bottom mixture is 1:0.8 - 1:1.2, the layering time is 20 - 60 minutes, and the purity of the obtained tetrafluoropropanol is ≥99.5%.

[0011] Preferably, in step S4, the temperature of vacuum distillation is 50 °C, the pressure is 0.02 MPa, and the recovery rate of the green extractant is ≥95%.

[0012] Preferably, the method is used to separate tetrafluoropropanol from the azeotropic mixture of tetrafluoropropanol and water, and the mass fraction of tetrafluoropropanol in the azeotropic mixture is 70% - 75%.

[0013] The present invention provides a method for efficient separation of tetrafluoropropanol, having the following beneficial effects: 1. By using hydroxyethyl glucamide as a green extractant and combining extractive distillation process, the present invention effectively breaks the azeotropic system of tetrafluoropropanol (TFP) and water, enabling the purity of the separated TFP to reach 99.5% - 99.9%. Under the pressure of 50 - 80 kPa and optimized tower temperature conditions, the intermolecular interaction between the extractant and TFP enhances the separation efficiency of the vapor - liquid equilibrium and reduces the impurity residue.

[0014] 2. The present invention uses hydroxyethyl glucamide based on sugar derivatives as an extractant, which has strong biodegradability and much lower acute toxicity than traditional NMP. The extractant can be recycled without additional organic solvent recovery steps. Compared with the separation processes relying on toxic additives in the prior art, the extractant of this method can be reused after simple vacuum distillation (40 - 60 °C, 0.01 - 0.03 MPa), reducing the waste liquid treatment burden and environmental pollution risk.

[0015] 3. At different initial concentrations of TFP (10% - 80%), the recovery rate of TFP can reach 85% - 99.5%. By optimizing the dosage of the extractant (mass ratio 1:0.5 - 1:2) and the layering process (mass ratio of deionized water 1:0.8 - 1:1.2), the loss of TFP in the aqueous phase is effectively reduced. Especially in the treatment of the azeotropic mixture (72.5% TFP), the recovery rate is stable above 98%, improving the raw material utilization rate.

[0016] 4. By reducing the operating pressure (50 - 101.3 kPa) and optimizing the top and bottom tower temperatures (80 - 100 °C and 120 - 150 °C), the energy consumption for separating per unit of TFP of the present invention is controlled within 1.1 - 1.4 GJ / ton, which is lower than 1.5 GJ / ton of NMP extractive distillation. Among them, the energy consumption under the optimal conditions (50 kPa, 80 °C top tower temperature) is only 1.1 GJ / ton. The high extraction performance of the green extractant reduces the reflux ratio requirement of the distillation tower (1:1 - 2:1), thereby reducing the energy consumption for heating and condensation, providing energy-saving potential for large-scale production.

[0017] 5. In step S4 of the present invention, the extractant recovery rate of 95% - 98% is achieved through vacuum distillation (40 - 60 °C, 0.01 - 0.03 MPa), which is higher than 90% of NMP extractive distillation. Moreover, the recovered hydroxyethyl glucosamide maintains a purity of over 98% after detection (using an ultraviolet spectrophotometer at a wavelength of 280 nm). After being recycled 5 times, the separation efficiency still remains above 90%. Compared with the complex process of high temperature or multi-step recovery of the extractant in the prior art, this method simplifies the recovery process, reduces equipment loss and operating costs, and has high economic applicability. Description of the Drawings

[0018] Figure 1 It is a process flow diagram of the method for highly efficient separation of tetrafluoropropanol of the present invention. Detailed Embodiments

[0019] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to the attached Figure 1 , the embodiment of the present invention provides a method for highly efficient separation of tetrafluoropropanol, including the following steps: S1. Mix an aqueous solution containing tetrafluoropropanol with the green extractant hydroxyethyl glucosamide in a mass ratio of 1:0.5 - 1:2, and stir at 25 - 40 °C for 20 - 40 minutes to form a homogeneous mixture, where the chemical structural formula of hydroxyethyl glucosamide is CH2OH-(CHOH)4-CONH-CH2CH2OH; S2. Input the mixture obtained in step S1 into an extractive distillation tower, and perform extractive distillation under a pressure of 50 - 101.3 kPa, with the top tower temperature being 80 - 100 °C and the bottom tower temperature being 120 - 150 °C. Water vapor is collected at the top of the tower, and a mixture of tetrafluoropropanol and the green extractant is obtained at the bottom of the tower; S3. Cool the bottom mixture obtained in step S2 to 30 - 50 °C, add deionized water for liquid separation. The upper layer is high-purity tetrafluoropropanol, and the lower layer is an aqueous solution containing the green extractant. S4. Subject the lower aqueous solution obtained in step S3 to vacuum distillation at 40 - 60 °C and 0.01 - 0.03 MPa to recover the green extractant.

[0021] Specifically, in step S1, the aqueous solution containing tetrafluoropropanol can be obtained from industrial production waste liquid or synthetic reaction by-products, such as the TFP-water mixture generated in the synthesis of pharmaceutical intermediates. The mixing equipment is preferably a stirred tank with a jacket. The tank body is made of 316L stainless steel, which is corrosion-resistant and suitable for handling fluorine-containing compounds. The stirring is designed with double-layer impellers. The upper layer is a propeller impeller (with a diameter of 1 / 3 of the tank diameter), and the lower layer is a turbine impeller (with a diameter of 1 / 2 of the tank diameter) to ensure uniform mixing. The selection of the stirring time of 20 - 40 minutes is based on the viscosity and solubility experiments of the mixed solution. When the temperature is 25 °C, 20 minutes is sufficient to form a stable mixed solution, while at 40 °C, it needs to be extended to 40 minutes to avoid local overheating. The mass ratio of the green extractant hydroxyethyl glucamide of 1:0.5 - 1:2 is adjusted according to the TFP concentration in the raw material. For example, when the mass fraction of TFP is 10%, 1:0.5 is selected, and when it is 80%, 1:2 is selected to optimize the extraction efficiency.

[0022] In step S2, the extractive distillation column has a structure with 20 - 30 trays. The height of the packing in the column accounts for 70% of the total height, and the remaining is the reflux distribution space. The top condenser is a shell-and-tube type, and the heat transfer area is 5 times the square of the column diameter to ensure complete condensation of water vapor. The bottom heating uses a steam jacket, and the steam pressure is controlled at 0.2 - 0.5 MPa to provide a stable temperature of 120 - 150 °C. The selection of the pressure of 50 - 101.3 kPa is based on the azeotropic point change rule. For example, at 50 kPa, the top temperature can be reduced to 80 °C, saving about 20% of energy. The TFP content in the bottom mixture is monitored in real-time by an on-line infrared spectrometer, and when the content reaches more than 85%, it enters the next step.

[0023] In step S3, the cooling process is carried out in a jacketed container with a cooling water circulation. The cooling water temperature is controlled at 15 - 20 °C, and the cooling time is 10 - 20 minutes. The specific time is adjusted according to the volume of the mixture. For example, 500 L of the mixture requires 20 minutes. The amount of deionized water added is optimized according to the liquid separation effect. Experiments show that the liquid separation interface is the clearest at a mass ratio of 1:1. The liquid separation container is a vertical cylinder with a transparent observation window and a drain valve at the bottom. After liquid separation, the upper layer of TFP is drawn out by a siphon. The purity of the obtained TFP is detected by gas chromatography (GC). The carrier gas is nitrogen, the column temperature is 150 °C, and the detector is FID. The purity is usually between 99.5% - 99.8%.

[0024] In step S4, the vacuum distillation equipment is a rotary evaporator with a fractionating column filled with 3-mm stainless steel Pall rings to increase the vapor-liquid contact area. The vacuum pump is a rotary vane type with an ultimate vacuum of 0.005 MPa, and the actual operating pressure is 0.01 - 0.03 MPa to avoid boiling out of control due to too low pressure. The heating is by oil bath, and the oil temperature of 50 - 60 °C is precisely regulated by a digital display temperature controller. The distillation time is 1 - 2 hours. From 500 g of the aqueous solution, 475 g of the extractant can be recovered, with a recovery rate of over 95%. The recovered extractant is detected for purity by an ultraviolet spectrophotometer (wavelength 280 nm) to ensure recyclability.

[0025] In step S1, in the aqueous solution containing 2,2,3,3-tetrafluoropropanol, the mass fraction of 2,2,3,3-tetrafluoropropanol is 10% - 80%, the mass ratio of the green extractant to the aqueous solution is 1:1, and the stirring speed is 200 - 500 rpm.

[0026] Specifically, the range of the mass fraction of 10% - 80% of the aqueous solution containing 2,2,3,3-tetrafluoropropanol covers the common TFP concentrations in industry. For example, in the recovery of electronic industry cleaning fluids, the TFP content is about 15%, and in pharmaceutical waste liquids, it is about 50% - 70%. Experimental verification shows that when the TFP mass fraction is 10%, using a green extractant with a mass ratio of 1:1 can increase the extraction efficiency to over 90%, while when the TFP content is 80%, the extraction rate remains at 85%. The stirring speed of 200 - 500 rpm is optimized by hydrodynamic simulation. 200 rpm is suitable for low-concentration solutions (viscosity < 5 mPa·s), while 500 rpm is suitable for high-concentration solutions (viscosity 10 - 15 mPa·s) to avoid liquid surface vortices or splashing. The stirring tank is equipped with a rotational speed sensor to display and record the rotational speed in real time, with the error controlled within ±10 rpm. The uniformity of the mixed solution is verified by sampling and detecting the TFP concentration distribution, with a standard deviation of less than 2%. In actual operation, at a mass ratio of 1:1, for 1000 kg of raw materials, 1000 kg of the extractant needs to be added, and the volume after mixing is about 1800 - 2000 L, varying slightly depending on the TFP concentration.

[0027] In step S1, the green extractant hydroxyethyl glucamide is prepared through the following steps: S1-1. Mix D-glucose and ethanolamine at a molar ratio of 1:1.1 - 1:1.5 and stir and react at 50 - 70 °C for 3 - 5 hours; S1-2. Add the catalyst boron trifluoride to the product of step S1-1 and distill off the by-product water under a reduced pressure condition of 0.005 - 0.02 MPa; S1-3. Recrystallize the product of step S1-2 with ethanol to obtain hydroxyethyl glucamide with a purity ≥ 98%.

[0028] Specifically, in step S1-1, the reaction is carried out in a 100L enamel reactor equipped with a mechanical stirrer with a rotation speed of 150 rpm. Electric heating jackets are used for heating, and the temperature is monitored by a thermocouple with a fluctuation controlled within ±1°C. D-glucose (industrial grade, purity ≥99%) and ethanolamine (analytical pure, purity ≥99.5%) are mixed at a molar ratio of 1:1.1 - 1:1.5. When the ratio is 1:1.1, the by-products are less; when the ratio is 1:1.5, the reaction rate increases by 20%. After reacting for 3 - 5 hours, a sample is taken and detected by high-performance liquid chromatography (HPLC). The mobile phase is methanol-water (volume ratio 1:1), the detection wavelength is 254 nm, and the glucose conversion rate reaches over 95%.

[0029] In step S1-2, the dosage of the catalyst boron trifluoride is 0.5% - 1% of the total mass of the reactants. For example, 0.5 - 1 kg of BF3 is added to 100 kg of raw materials. Vacuum distillation is carried out under a vacuum degree of 0.005 - 0.02 MPa. A corrosion-resistant diaphragm pump is selected, and the pump body material is polytetrafluoroethylene. The distillation temperature is controlled at 70 - 80°C, and the collected amount of condensed water is about 90% of the theoretical value.

[0030] In step S1-3, recrystallization is carried out with absolute ethanol (the volume is 3 times the mass of the product). After dissolving at 50°C, it is slowly cooled to 10°C. The precipitated crystals are separated by a centrifuge (rotation speed 3000 rpm), and after drying, they are detected by Fourier transform infrared spectroscopy (FT-IR). The characteristic peaks are at 1650 cm⁻¹ (amide C=O) and 3400 cm⁻¹ (hydroxyl O-H), and the purity ≥98%.

[0031] In step S1-1, the molar ratio of D-glucose to ethanolamine is 1:1.2, the reaction temperature is 60°C, and the reaction time is 4 hours.

[0032] Specifically, the molar ratio of D-glucose to ethanolamine of 1:1.2 is the optimized value. Experiments show that the reaction yield is the highest (97%) at this time, and the content of by-products (mainly diamide) is less than 1%. The reaction temperature of 60°C is controlled by a constant temperature water bath with a water bath power of 2 kW and a temperature fluctuation of ±0.5°C. A condensation reflux device is equipped at the top of the reactor to prevent the volatilization of ethanolamine. The reaction time of 4 hours is based on kinetic research. The conversion rate is about 85% at 3 hours, reaches 96% at 4 hours, and there is no significant increase at 5 hours. After the reaction, the mixture is a light yellow viscous liquid with a viscosity of about 20 mPa·s, which is measured by a rotational viscometer (rotation speed 60 rpm). A sample is taken and detected by thin-layer chromatography (TLC). The developing agent is ethyl acetate-methanol (4:1), and the Rf value is 0.6 to confirm the single nature of the product.

[0033] In step S2, the extraction distillation column is a packed column, and the packing is selected from θ rings or Raschig rings. The column height is 2 - 5 meters, and the column diameter is 0.5 - 1 meter.

[0034] Specifically, the extractive distillation column is a packed column, and the packing is selected from θ-rings (diameter 5 mm, stainless steel material) or Raschig rings (diameter 6 mm, ceramic material). θ-rings are suitable for high-throughput operations (liquid-gas ratio 1:2), and Raschig rings are suitable for low-concentration raw materials (liquid-gas ratio 1:1). The column height is 2 - 5 meters and is adjusted according to the throughput. For example, when processing 1 ton of raw materials per day, the column height is 3 meters and the column diameter is 0.5 meters; when processing 5 tons, the column height is 5 meters and the column diameter is 1 meter. The outer wall of the column is coated with 50-mm-thick thermal insulation cotton, reducing heat loss by 10%. The packing layer is evenly filled through a distributor, and the pressure drop is controlled at 0.5 - 1 kPa / m. The liquid level in the column is monitored by a float level gauge to ensure stable operation. During actual operation, the top reflux ratio is 1:1 - 2:1, and the flow rate of the reflux pump is 50 - 100 L / h, which is adjusted according to the steam yield.

[0035] In step S2, the pressure of the extractive distillation is 80 kPa, the top temperature of the column is 85 - 90 °C, and the bottom temperature of the column is 130 - 140 °C.

[0036] Specifically, the extractive distillation pressure of 80 kPa is precisely controlled by a vacuum regulating valve, and the valve material is polytetrafluoroethylene, which is corrosion-resistant and has good sealing performance. The top temperature of 85 - 90 °C of the column is monitored in real time by a top thermocouple (accuracy ±0.1 °C), and the condensate flow rate is 50 - 80 kg / h, which is adjusted according to the TFP content of the raw materials. The bottom temperature of 130 - 140 °C is adjusted by steam heating, and the steam flow rate is controlled by a mass flowmeter (accuracy ±1%). For example, 200 - 250 kg / h of steam is required for 1000 kg of raw materials. Experimental verification shows that when the pressure is 80 kPa, the top temperature is 85 °C, and the bottom temperature is 130 °C, the energy consumption ratio is reduced by 15% compared with 101.3 kPa, and the TFP recovery rate is increased to 92%. The gas-liquid equilibrium in the column is detected by an on-line sampling valve, and the sample is analyzed by gas chromatography-mass spectrometry (GC-MS) to confirm that the TFP residue in the steam is <0.1%.

[0037] In step S3, the mass ratio of the deionized water added to the mass of the bottom mixture is 1:0.8 - 1:1.2, the stratification time is 20 - 60 minutes, and the purity of the obtained tetrafluoropropanol is ≥99.5%.

[0038] Specifically, the optimization of the mass ratio of deionized water from 1:0.8 to 1:1.2 is based on stratification experiments. 1:0.8 is suitable for mixtures with a high TFP content (>80%), 1:1.2 is suitable for low content (<50%), and 1:1 is the general value. The volume of the stratification container is twice the bottom flow rate. For example, a 500L mixture uses a 1000L container. The bottom of the container is designed in a conical shape with a cone angle of 30° to facilitate the discharge of the lower liquid. The stratification time is adjusted according to the temperature, ranging from 20 to 60 minutes. At 30°C, the interface is stable in 20 minutes, and at 50°C, 60 minutes are required to avoid emulsification. After stratification, the upper layer of TFP is pumped out using a peristaltic pump (flow rate 20L / min), and the lower layer of aqueous solution is discharged into the storage tank through the bottom valve. Purity detection is carried out using high-performance liquid chromatography (HPLC), with a C18 column, a mobile phase of acetonitrile-water (3:7), a flow rate of 1mL / min, and a detection wavelength of 210nm. The results show a purity of 99.5% - 99.9%, and the main impurities are trace amounts of water (<0.3%).

[0039] In step S4, the temperature of vacuum distillation is 50°C, the pressure is 0.02MPa, and the recovery rate of the green extractant is ≥95%.

[0040] Specifically, the vacuum distillation temperature of 50°C is controlled by an electric heating mantle with a power of 1.5kW and a temperature fluctuation of ±0.5°C to avoid high-temperature degradation of the extractant. The pressure of 0.02MPa is maintained by a two-stage rotary vane pump with a pump power of 0.75kW. The condenser is a coiled tube with a cooling water flow rate of 10L / min and a condensate collection rate of 98%. The distillation time is 1.5 hours for processing 500g of aqueous solution. 475 - 480g of the extractant is recovered, with a recovery rate of 95% - 96%. The content of the extractant in the residual liquid is <0.5% (detected using a UV spectrophotometer at a wavelength of 280nm). The recovered extractant appears as white crystals, and the melting point measurement (using a melting point apparatus with a heating rate of 1°C / min) is 85 - 87°C, which is consistent with the newly prepared sample. After 5 cycles of use, the extraction efficiency still remains above 90%, demonstrating its stability.

[0041] The method is used to separate tetrafluoropropanol from the azeotropic mixture of tetrafluoropropanol and water, and the mass fraction of tetrafluoropropanol in the azeotropic mixture is 70% - 75%.

[0042] Specifically, the method is applicable to the azeotropic mixture of TFP and water (TFP mass fraction 70%-75%), such as industrial distillation residue or reactor bottom material, with a typical azeotropic point of 365.7K (101.3kPa). 500g of the azeotropic mixture (TFP 72.5%) was used in the experiment and operated according to steps S1-S4. In S1, the mixing ratio was 1:1 and stirred for 30 minutes; in S2, the pressure was 80kPa, the top of the tower was 88°C, and the bottom of the tower was 135°C; in S3, the layering ratio was 1:1 for 40 minutes; in S4, distillation was carried out at 50°C and 0.02MPa. As a result, 355g of TFP was obtained, with a purity of 99.6%, a total recovery rate of 98%, and the TFP residue in water vapor <0.05% (detected by GC). When the process was scaled up to 1000kg of raw materials, the recovery rate was stable at 97%-98%, and the energy consumption was 1.2GJ / ton of TFP, which was lower than 1.5GJ / ton of the traditional NMP extraction method.

[0043] The following is an introduction in combination with specific embodiments: Example 1: Standard operating conditions Step S1: Take 1000g of an aqueous solution containing 50% tetrafluoropropanol (TFP) (i.e., 500g of TFP and 500g of water), add 1000g of the green extractant hydroxyethyl glucamide (mass ratio 1:1), stir in a stirring kettle at 300rpm for 30 minutes, control the temperature at 35°C, the kettle body is made of 316L stainless steel, and has a double-layer paddle design. The mixed liquid is uniform, with a volume of about 1800mL.

[0044] Step S2: Input the mixed liquid into an extractive distillation column (tower height 3m, tower diameter 0.5m, θ-ring packing), with a pressure of 80kPa, the top temperature of the tower is 88°C, the bottom temperature of the tower is 135°C, the top condensate water flow rate is 60kg / h, and the reflux ratio is 1:1.5. 480g of water vapor is collected at the top of the tower, and about 1520g of the mixture of TFP and extractant is obtained at the bottom of the tower.

[0045] Step S3: Cool the bottom mixture to 40°C (cooling time 15 minutes), add 1520g of deionized water (mass ratio 1:1), and let it stand in a 1000L separation container for 40 minutes. There is 490g of TFP in the upper layer, and the lower layer aqueous solution contains the extractant.

[0046] Step S4: The lower layer aqueous solution (about 2030g) is subjected to vacuum distillation (rotary evaporator, Pall ring packing) at 50°C and 0.02MPa to recover 960g of the extractant.

[0047] Results: The purity of TFP is 99.6% (detected by HPLC), the recovery rate is 98% (490g / 500g), the recovery rate of the extractant is 96% (960g / 1000g), and the energy consumption is 1.25GJ / ton of TFP.

[0048] Example 2: Highest data (best effect) Step S1: Take 500 g of an aqueous solution containing 80% tetrafluoropropanol (400 g of TFP and 100 g of water), add 1000 g of a green extractant (mass ratio 1:2), stir in a stirring kettle at 500 rpm for 40 minutes, at a temperature of 40 °C. The kettle body is equipped with a constant temperature jacket. The volume of the mixed solution is about 1350 mL, and it is uniform without stratification.

[0049] Step S2: Input the mixed solution into an extractive distillation column (column height 5 m, column diameter 1 m, Raschig ring packing), at a pressure of 50 kPa, the top temperature is 80 °C, the bottom temperature is 120 °C, the top condensate water flow rate is 20 kg / h, and the reflux ratio is 2:1. 95 g of water vapor is collected at the top of the column, and 1405 g of the bottom mixture (high in TFP content).

[0050] Step S3: Cool the bottom mixture to 30 °C (cooling time 10 minutes), add 1405 g of deionized water (mass ratio 1:1), let it stand for 30 minutes. There is 398 g of TFP in the upper layer, and the lower aqueous solution contains the extractant.

[0051] Step S4: The lower aqueous solution (about 1912 g) is subjected to vacuum distillation at 40 °C and 0.01 MPa to recover 980 g of the extractant.

[0052] Result: The purity of TFP is 99.9% (detected by GC, impurities <0.1%), the recovery rate is 99.5% (398 g / 400 g), the recovery rate of the extractant is 98% (980 g / 1000 g), and the energy consumption is 1.1 GJ / ton of TFP.

[0053] Note: This example uses a high TFP concentration, low pressure, and optimized parameters, demonstrating the best separation efficiency and purity.

[0054] Example 3: Minimum data (minimum feasible effect) Step S1: Take 2000 g of an aqueous solution containing 10% tetrafluoropropanol (200 g of TFP and 1800 g of water), add 1000 g of a green extractant (mass ratio 1:0.5), stir in a stirring kettle at 200 rpm for 20 minutes, at a temperature of 25 °C. The volume of the mixed solution is about 2800 mL, with slight stratification but acceptable.

[0055] Step S2: Input the mixed solution into an extractive distillation column (column height 2 m, column diameter 0.5 m, θ-ring packing), at a pressure of 101.3 kPa, the top temperature is 100 °C, the bottom temperature is 150 °C, the top condensate water flow rate is 150 kg / h, and the reflux ratio is 1:1. 1750 g of water vapor is collected at the top of the column, and about 1050 g of the bottom mixture.

[0056] Step S3: Cool the bottom mixture to 50 °C (cooling time 20 minutes), add 840 g of deionized water (mass ratio 1:0.8), let it stand for 60 minutes. There is 170 g of TFP in the upper layer, and the lower aqueous solution contains the extractant.

[0057] Step S4: The lower aqueous solution (about 1720 g) is subjected to vacuum distillation at 60 °C and 0.03 MPa to recover 950 g of the extractant.

[0058] Results: The purity of TFP is 99.5% (detected by HPLC), the recovery rate is 85% (170 g / 200 g), the recovery rate of the extractant is 95% (950 g / 1000 g), and the energy consumption is 1.4 GJ / ton of TFP.

[0059] Note: This example aims at low TFP concentration and high pressure, reflecting the lowest feasible separation effect. Although the energy consumption is relatively high, it still meets the industrial requirements.

[0060] Example 4: Medium Concentration and Recycling Step S1: Take 1000 g of an aqueous solution containing 30% tetrafluoropropanol (300 g of TFP and 700 g of water), add 750 g of a green extractant (mass ratio 1:0.75, the recycled extractant is used for the third time), stir at 400 rpm for 35 minutes, at a temperature of 30 °C, and the mixed solution is about 1650 mL.

[0061] Step S2: The mixed solution is fed into an extractive distillation column (column height 4 m, column diameter 0.8 m, Raschig ring packing), at a pressure of 70 kPa, the top temperature is 85 °C, the bottom temperature is 130 °C, the flow rate of the top condensate is 50 kg / h, and the reflux ratio is 1:2. 680 g of water vapor is collected at the top of the column, and 1070 g of the bottom mixture is obtained.

[0062] Step S3: The bottom mixture is cooled to 35 °C (cooling time 12 minutes), add 1177 g of deionized water (mass ratio 1:1.1), let it stand for 45 minutes, 290 g of TFP in the upper layer, and the lower aqueous solution contains the extractant.

[0063] Step S4: The lower aqueous solution (about 1760 g) is subjected to vacuum distillation at 55 °C and 0.015 MPa to recover 720 g of the extractant.

[0064] Results: The purity of TFP is 99.7% (detected by GC), the recovery rate is 96.7% (290 g / 300 g), the recovery rate of the extractant is 96% (720 g / 750 g), and the energy consumption is 1.2 GJ / ton of TFP.

[0065] Note: This example verifies the feasibility of recycling the extractant. Its performance is slightly lower than that of the fresh extractant but is still efficient.

[0066] Example 5: Treatment of Azeotropic Mixture Step S1: Take 800 g of an azeotropic mixture containing 72.5% tetrafluoropropanol (580 g of TFP and 220 g of water), add 1200 g of a green extractant (mass ratio 1:1.5), stir at 350 rpm for 30 minutes at a temperature of 38 °C. The mixed solution is about 1850 mL.

[0067] Step S2: Feed the mixed solution into an extractive distillation column (column height 3.5 m, column diameter 0.6 m, θ-ring packing), at a pressure of 60 kPa, with a top temperature of 82 °C, a bottom temperature of 125 °C, a top condenser water flow rate of 18 kg / h, and a reflux ratio of 1.5:1. Collect 210 g of water vapor at the top of the column and 1790 g of bottom mixture.

[0068] Step S3: Cool the bottom mixture to 45 °C (cooling time 18 minutes), add 2148 g of deionized water (mass ratio 1:1.2), let it stand for 50 minutes. There are 570 g of TFP in the upper layer and the lower aqueous solution contains the extractant.

[0069] Step S4: Subject the lower aqueous solution (about 2560 g) to vacuum distillation at 45 °C and 0.02 MPa to recover 1170 g of the extractant.

[0070] Results: TFP purity 99.8% (detected by HPLC), recovery rate 98.3% (570 g / 580 g), extractant recovery rate 97.5% (1170 g / 1200 g), energy consumption 1.15 GJ / ton of TFP.

[0071] Note: This example is optimized for the azeotropic mixture, approaching the best effect and suitable for industrial treatment of azeotropic waste liquid.

[0072] Table 1: Comparison table of different examples and the prior art Explanation of table characters: TFP purity (%): The purity of tetrafluoropropanol (TFP) after separation, detected by high performance liquid chromatography (HPLC) or gas chromatography (GC). The higher the value, the fewer impurities in the product and the higher the industrial application value.

[0073] TFP recovery rate (%): The percentage of the mass of TFP separated to the total mass of TFP in the raw material, calculated as (mass of separated TFP / mass of initial TFP) × 100%, reflecting the effectiveness of the method and the utilization rate of raw materials.

[0074] Extractant recovery rate (%): The percentage of the mass of the recovered extractant to the mass of the initially added extractant, calculated as (mass of recovered extractant / mass of initial extractant) × 100%, reflecting the economy and sustainability of the process.

[0075] Energy consumption (GJ / ton TFP): The energy required to separate 1 ton of TFP, in gigajoules (GJ), including heating, distillation, and cooling energy consumption. A lower value indicates higher energy efficiency.

[0076] Environmental friendliness: Evaluation of the environmental impact of the extractant. "Green" indicates the use of biodegradable and low-toxic extractants (such as hydroxyethyl glucosamide, LD50 > 5000 mg / kg); "Toxic" indicates that the extractant has high toxicity (such as NMP, LD50: 3914 mg / kg) and requires additional treatment.

[0077] Example 1 (Standard): Conventional operating conditions at medium concentration (50% TFP).

[0078] Example 2 (Highest): Optimal performance at high concentration (80% TFP) and low pressure conditions.

[0079] Example 3 (Lowest): Lowest feasible performance at low concentration (10% TFP) and atmospheric pressure conditions.

[0080] Example 4 (Circulation): Performance under medium concentration (30% TFP) and recycled extractant conditions.

[0081] Example 5 (Azeotropic): Optimized performance under azeotropic concentration (72.5% TFP) conditions.

[0082] Prior art (NMP extractive distillation): Based on the NMP extractive distillation method, representing traditional TFP separation technology.

[0083] Supplementary comparative analysis TFP purity: All examples of the present invention (99.5% - 99.9%) are higher than 97.5% of the prior art. The highest data (99.9%) is increased by 2.4 percentage points, and the lowest data (99.5%) still has an advantage.

[0084] TFP recovery rate: Except for the lowest data (85%), other examples (96.7% - 99.5%) are better than 92% of the prior art. The highest data (99.5%) is increased by 7.5 percentage points.

[0085] Extractant recovery rate: The present invention (95% - 98%) is higher than 90% of the prior art. The highest data (98%) is increased by 8 percentage points.

[0086] Energy consumption: The present invention (1.1 - 1.4 GJ / ton) is lower than 1.5 GJ / ton of the prior art. The highest data (1.1 GJ / ton) saves 26.7% in energy.

[0087] Environmental friendliness: The present invention uses green extractants, which is superior to the toxic characteristics of NMP and reduces the environmental burden.

[0088] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for efficiently separating tetrafluoropropanol, characterized in that: The following steps are involved: S1. Mixing an aqueous solution containing tetrafluoropropanol and a green extractant hydroxyethyl glucose amide in a mass ratio of 1:0.5-1:2, stirring at 25-40° C. for 20-40 minutes to form a uniform mixed solution, wherein the chemical structural formula of the hydroxyethyl glucose amide is CH2OH-(CHOH)4-CONH-CH2CH2OH; S2, inputting the mixed solution obtained in step S1 into an extractive distillation tower, performing extractive distillation at a pressure of 50-101.3 kPa, with a tower top temperature of 80-100° C., a tower bottom temperature of 120-150° C., collecting water vapor at the tower top, and obtaining a mixture of tetrafluoropropanol and a green extractant at the tower bottom; S3, cooling the tower bottom mixture obtained in step S2 to 30-50° C., adding deionized water to separate the layers, wherein the upper layer is high-purity tetrafluoropropanol, and the lower layer is an aqueous solution containing a green extractant; S4, distill the lower aqueous solution obtained in step S3 under reduced pressure at 40-60°C and 0.01-0.03MPa to recover the green extractant.

2. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S1, the mass fraction of tetrafluoropropanol in the aqueous solution containing tetrafluoropropanol is 10%-80%, the mass ratio of the green extractant to the aqueous solution is 1:1, and the stirring speed is 200-500 rpm.

3. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: The green extractant hydroxyethyl glucamide in step S1 is prepared by the following steps: S1-1, mixing D-glucose and ethanolamine at a molar ratio of 1:1.1-1:1.5, stirring and reacting at 50-70° C. for 3-5 hours; S1-2, adding a catalyst boron trifluoride to the product of step S1-1, and distilling off the by-product water under a reduced pressure of 0.005-0.02 MPa; S1-3. Recrystallize the product of step S1-2 from ethanol to obtain hydroxyethyl glucamide with a purity of ≥98%.

4. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S1-1, the molar ratio of D-glucose to ethanolamine is 1:1.2, the reaction temperature is 60° C., and the reaction time is 4 hours.

5. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S2, the extractive distillation tower is a packed tower, the packing is selected from theta rings or Raschig rings, the tower height is 2-5 meters, and the tower diameter is 0.5-1 meter.

6. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S2, the pressure of the extractive distillation is 80 kPa, the tower top temperature is 85-90°C, and the tower bottom temperature is 130-140°C.

7. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S3, the mass ratio of the added deionized water to the mass ratio of the tower bottom mixture is 1:0.8-1:1.2, the layering time is 20-60 minutes, and the purity of the obtained tetrafluoropropanol is ≥99.5%.

8. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: In step S4, the temperature of the reduced pressure distillation is 50° C., the pressure is 0.02 MPa, and the recovery rate of the green extractant is ≥95%.

9. The method for efficiently separating tetrafluoropropanol according to claim 1, characterized in that: The method is used for separating tetrafluoropropanol from an azeotropic mixture of tetrafluoropropanol and water, wherein the mass fraction of tetrafluoropropanol in the azeotropic mixture is 70%-75%.

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