Refining process of high-purity tetrafluoropropanol

Abstract

The invention relates to the field of chemical engineering, and discloses a high-purity tetrafluoropropanol refining process, which comprises the following steps: (1) preliminary dehydration rectification: adding crude tetrafluoropropanol into a first rectification tower, carrying out rectification under a normal pressure condition, adding an entrainer A, and collecting tower bottoms; (2) rectification under reduced pressure: feeding the tower bottoms obtained in the step (1) into a second rectification tower, performing rectification under the pressure of 10-30kPa, adding an entrainer B, and collecting the tower bottoms; and (3) high-purity rectification: feeding the tower bottoms obtained in the step (2) into a third rectification tower, performing rectification under the pressure of 5-15kPa, adding an entrainer C, and collecting the tower bottoms to obtain the high-purity tetrafluoropropanol. By adopting the entrainer B to assist the vacuum distillation, the fluorinated by-product in the tetrafluoropropanol is azeotropic along with the entrainer and is discharged from the tower top, so that the purpose of accurately separating the fluorinated by-product under the condition of lower negative pressure is achieved, and the effects of reducing the residue of the fluorinated by-product and improving the chemical stability of the tetrafluoropropanol are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, specifically to a high-purity tetrafluoropropanol refining process. Background Art

[0002] Tetrafluoropropanol is an important chemical raw material, widely used in multiple fields such as refrigerants, electronic devices, pharmaceutical and chemical industries. Due to its unique chemical properties, tetrafluoropropanol plays a key role in many industrial processes, especially in high-performance refrigeration, cleaners, and coolants for electronic devices, with irreplaceable application value. However, in the production process of tetrafluoropropanol, due to the complexity of its synthesis and separation processes, some fluorinated by-products are often generated. These by-products not only affect the purity of tetrafluoropropanol but also may cause environmental pollution and health risks.

[0003] The existing tetrafluoropropanol purification technologies mainly adopt distillation, adsorption, and extraction methods. However, these traditional technologies have limited effects in removing fluorinated by-products. Especially in the distillation process, due to the small difference in volatility between tetrafluoropropanol and impurities, the separation effect is not ideal. Further optimizing the distillation process to improve purity and removal efficiency has become a current research hotspot.

[0004] Many studies have tried to improve the separation effect by adjusting operating conditions such as temperature, pressure, and the use of azeotropes. However, in practical applications, there are still problems such as low yield, low purity, and incomplete removal of impurities. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the present invention provides a high-purity tetrafluoropropanol refining process, which solves the problems of low purity of tetrafluoropropanol and low removal efficiency of fluorinated by-products in the existing distillation process.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A high-purity tetrafluoropropanol refining process, including the following steps: (1) Preliminary dehydration distillation: Add crude tetrafluoropropanol to the first distillation column, distill under normal pressure conditions, and add azeotropic agent A, and collect the bottom liquid of the column; (2) Vacuum distillation: Feed the bottom liquid obtained in step (1) into the second distillation column, distill under a pressure of 10 - 30 kPa, add azeotropic agent B, and collect the bottom liquid of the column; (3) High-purity distillation: Feed the bottom liquid obtained in step (2) into the third distillation column, distill under a pressure of 5 - 15 kPa, add azeotropic agent C, and collect the bottom liquid of the column to obtain high-purity tetrafluoropropanol.

[0007] Preferably, the preparation method of the azeotropic agent A is prepared according to the following steps: Add methyl trifluoroacetate to the stirring reaction kettle; At a temperature of 25 - 35 °C, hexafluoroisopropanol was gradually added and stirred for 30 minutes; The solid impurities were removed by filtration to obtain a transparent liquid azeotropic agent A.

[0008] Preferably, the preparation method of the azeotropic agent B is prepared according to the following steps: Hexafluoroisopropanol was added to a stirring reaction kettle and the temperature was raised to 30 - 40 °C; Under stirring, trimethyl phosphate was added and stirred for 45 - 60 minutes; After cooling to room temperature, it was filtered to obtain azeotropic agent B.

[0009] Preferably, the preparation method of the azeotropic agent C is prepared according to the following steps: Trimethyl phosphate was added to a reaction kettle and stirred at 20 - 30 °C; Methyl trifluoroacetate was gradually added and stirred for 30 - 45 minutes; It was filtered to obtain a transparent liquid azeotropic agent C.

[0010] Preferably, the top temperature of the preliminary dehydration rectification is set at 55 - 65 °C, the bottom temperature is set at 95 - 105 °C, and the reflux ratio is controlled at 3 - 4.

[0011] Preferably, the top temperature of the vacuum rectification is maintained at 55 - 85 °C, the bottom temperature is set at 105 - 125 °C, and the negative pressure control range is 15 - 25 kPa.

[0012] Preferably, the top temperature of the high - purity rectification is set at 70 - 90 °C, the bottom temperature is maintained at 115 - 135 °C, and the negative pressure control range is 8 - 12 kPa.

[0013] Preferably, the addition ratio of the azeotropic agent A is 3 - 5% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of methyl trifluoroacetate to hexafluoroisopropanol in the azeotropic agent A is 4:6.

[0014] Preferably, the addition ratio of the azeotropic agent B is 4 - 6% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of hexafluoroisopropanol to trimethyl phosphate in the azeotropic agent B is 7:3.

[0015] Preferably, the addition ratio of the azeotropic agent C is 2 - 4% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of trimethyl phosphate to methyl trifluoroacetate in the azeotropic agent C is 5.5:4.5.

[0016] The present invention provides a high - purity tetrafluoropropanol refining process. It has the following beneficial effects: 1. The present invention adopts azeotropic agent B to assist in vacuum distillation, enabling the fluorination by-products in tetrafluoropropanol to form an azeotrope with the azeotropic agent and be discharged from the top of the column, thereby achieving the purpose of precisely separating the fluorination by-products under relatively low negative pressure conditions, obtaining the effect of reducing the residue of fluorination by-products and improving the chemical stability of tetrafluoropropanol.

[0017] 2. The present invention prepares azeotropic agent C by mixing trimethyl phosphate and methyl trifluoroacetate in a specific mass ratio, achieving the purpose of forming an azeotrope with aldehyde and ester impurities and discharging them from the top of the column during high-purity distillation, obtaining the effect of further reducing the impurity content and improving the purity of tetrafluoropropanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the preparation process steps of the present invention; Figure 2 It is a data table diagram of Experiment 1 of the present invention; Figure 3 It is a data table diagram of Experiment 2 of the present invention; Figure 4 It is a data table diagram of Experiment 3 of the present invention; Figure 5 It is a data table diagram of Experiment 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The technical solutions of the present invention will be clearly and completely described below 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 them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0020] Please refer to the attached Figure 1 , the present invention provides a high-purity tetrafluoropropanol refining process, including the following steps: (1) Preliminary dehydration distillation: Add crude tetrafluoropropanol to the first distillation column, distill under atmospheric pressure, and add azeotropic agent A, and collect the bottom liquid; Azeotropic agent A is prepared according to the following steps: Add methyl trifluoroacetate to a stirring reaction kettle; Gradually add hexafluoroisopropanol at a temperature of 25 - 35 °C, and stir for 30 minutes; Filter to remove solid impurities to obtain a transparent liquid azeotropic agent A.

[0021] (2) Vacuum distillation: Feed the bottom liquid obtained in step (1) into the second distillation column, distill under a pressure of 10 - 30 kPa, add azeotropic agent B, and collect the bottom liquid; Azeotropic agent B is prepared according to the following steps: Add hexafluoroisopropanol into a stirring reactor and heat up to 30 - 40 °C; Under stirring, add trimethyl phosphate and stir for 45 - 60 minutes; After cooling to room temperature, filter to obtain azeotropic agent B.

[0022] (3)High - purity rectification: Feed the bottom liquid obtained in step (2) into the third rectification column, rectify under a pressure of 5 - 15 kPa, add azeotropic agent C, collect the bottom liquid to obtain high - purity tetrafluoropropanol.

[0023] Azeotropic agent C is prepared according to the following steps: Add trimethyl phosphate into a reactor and stir under the condition of 20 - 30 °C; Gradually add methyl trifluoroacetate and stir for 30 - 45 minutes; Filter to obtain transparent liquid azeotropic agent C.

[0024] Based on the same inventive concept as above, the following example content is provided: Example 1: Removal of fluorination by - products in vacuum rectification Prepare raw materials: Take 100 L of tetrafluoropropanol raw material with a purity of about 98%. Add azeotropic agent B (ethanol), and its addition ratio is 4% of the total mass of tetrafluoropropanol.

[0025] Start the equipment: Feed the mixture into the vacuum rectification column. Set the operating temperature inside the column to 50 °C and control the pressure inside the column at 40 kPa.

[0026] Heating and rectification: Start the heating system to gradually increase the temperature of the rectification column to 50 °C, and tetrafluoropropanol and ethanol carry out an azeotropic reaction under low pressure.

[0027] Separate fluorination by - products: By adjusting the temperature and pressure of the rectification column, ensure that the fluorination by - products are discharged from the top of the column together with azeotropic agent B.

[0028] Collect the top liquid: The azeotropic liquid at the top of the column is condensed by a condenser to separate the fluorination by - products and remove impurities.

[0029] Secondary rectification: The remaining liquid enters the rectification column again for further separation, and finally tetrafluoropropanol with a purity of over 99% is obtained.

[0030] Example 2: Removal of impurities using trimethyl phosphate (TMP) Prepare raw materials and azeotropic agent: Take 100 L of tetrafluoropropanol and add trimethyl phosphate (TMP) with a ratio of 4% of the total mass.

[0031] Heat the mixture: Heat the mixture to 80 °C to ensure that TMP and tetrafluoropropanol are fully mixed.

[0032] Feed into the rectification column: Feed the heated mixture into a vacuum rectification column, set the top temperature at 85 °C, the bottom temperature at 130 °C, and the pressure inside the column at 40 kPa.

[0033] Azeotropic separation: Under these conditions, TMP and 2,2,3,3-tetrafluoropropanol form an azeotrope, and aldehyde and ester impurities are discharged from the top of the column along with the azeotrope.

[0034] Separate impurities: The liquid at the top of the column is condensed by a condenser and the impurities and 2,2,3,3-tetrafluoropropanol are separated.

[0035] Rectification treatment: The liquid at the bottom of the column continues for rectification treatment, and finally 2,2,3,3-tetrafluoropropanol with a purity of over 99% is obtained.

[0036] Example 3: Optimization of the ratio of three azeotropic agents Prepare raw materials and azeotropic agents: Take 100 L of 2,2,3,3-tetrafluoropropanol raw material, add 3% of azeotropic agent A (dichloromethane), 5% of azeotropic agent B (ethanol), and 2% of azeotropic agent C (TMP).

[0037] Heat the mixture: After uniformly mixing 2,2,3,3-tetrafluoropropanol and the azeotropic agents, heat it to 50 °C.

[0038] Feed into the vacuum rectification column: Feed the mixture into a vacuum rectification column, set the top temperature at 70 °C, the bottom temperature at 120 °C, and the pressure inside the column at 35 kPa.

[0039] Azeotropic separation: Through the rectification column, the three azeotropic agents and 2,2,3,3-tetrafluoropropanol form an azeotrope, and the impurities are discharged from the top of the column together with the azeotrope.

[0040] Condensation and separation: The azeotrope at the top of the column is condensed by a condenser, separated, the impurities are removed, and 2,2,3,3-tetrafluoropropanol is recovered.

[0041] Secondary rectification: The remaining liquid continues for secondary rectification, and finally 2,2,3,3-tetrafluoropropanol with a purity of over 99.5% is obtained.

[0042] Example 4: High-purity rectification process Prepare raw materials and azeotropic agents: Take 100 L of 2,2,3,3-tetrafluoropropanol raw material, add azeotropic agent B (ethanol) with a ratio of 4%.

[0043] Preheat and feed into the rectification column: After uniformly mixing 2,2,3,3-tetrafluoropropanol and ethanol, feed it into the rectification column, set the top temperature at 70 °C, and control the pressure inside the column at 40 kPa.

[0044] Vacuum rectification: Start the rectification column for vacuum rectification, and impurities are discharged from the top of the column during the azeotropic process of 2,2,3,3-tetrafluoropropanol and ethanol.

[0045] Condensation separation: The azeotrope at the top of the column is condensed by a condenser to separate the impurities from 2,2,3,3-tetrafluoropropanol.

[0046] Repeated rectification: The liquid at the bottom of the tower continues to undergo secondary rectification, and finally tetrafluoropropanol with a purity of over 99% is obtained.

[0047] Product treatment: The final tetrafluoropropanol is cooled, filtered, and stored to ensure the stability and purity of the product.

[0048] Example 5: Combined use of azeotropes A and C Prepare raw materials and azeotropes: Take 100 L of tetrafluoropropanol raw material and add 2% of azeotrope A (dichloromethane) and 3% of azeotrope C (methyl trifluoroacetate).

[0049] Heat the mixture: After mixing tetrafluoropropanol with the azeotropes, start heating to 50 °C.

[0050] Feed into the rectification column: Feed the mixture into a vacuum rectification column. Set the pressure inside the column to 30 kPa, the temperature at the top of the column to 75 °C, and the temperature at the bottom of the column to 115 °C.

[0051] Rectification process: Through the rectification column, tetrafluoropropanol forms an azeotrope with the azeotropes, and the impurities are discharged from the top of the column along with the azeotrope.

[0052] Condensation and separation: The liquid at the top of the column is condensed by a condenser to separate tetrafluoropropanol and impurities.

[0053] Secondary rectification: The remaining liquid is fed into a second rectification column for further purification, and finally tetrafluoropropanol with a purity of over 99% is obtained.

[0054] Final product: Through cooling and filtration, pure tetrafluoropropanol is finally obtained for storage.

[0055] Comparative example 1: Vacuum rectification without using azeotrope B Prepare raw materials: Take 100 L of tetrafluoropropanol raw material with a purity of 98%.

[0056] Equipment startup: Without using azeotrope B, directly feed tetrafluoropropanol into the vacuum rectification column.

[0057] Rectification conditions: Set the temperature inside the rectification column to 50 °C and control the pressure inside the column at 40 kPa.

[0058] Operation process: Tetrafluoropropanol is rectified under low-pressure conditions, but there is no azeotrope B to assist in removing fluorination by-products.

[0059] Separation result: After rectification, the impurities cannot be effectively removed, and the separation effect between the top and bottom of the column is poor.

[0060] Final treatment: The finally obtained tetrafluoropropanol has a low purity and still contains a certain amount of fluorination by-products and other impurities.

[0061] The key point in this comparative experiment is not to use the auxiliary of azeotropic agent B. Compared with the scheme of using ethanol as azeotropic agent B in Example 1, the results show that without the assistance of azeotropic agent B, the removal efficiency of fluorination by-products during the rectification process is significantly reduced, the purity of tetrafluoropropanol is relatively low, and the process efficiency is poor. Through this comparison, the importance of azeotropic agent B for the removal of fluorination by-products and the innovation of the present invention in this aspect can be highlighted.

[0062] Comparative Example 2: A rectification process without optimizing the ratio of azeotropic agents A and C Prepare raw materials and azeotropic agents: Take 100 L of tetrafluoropropanol raw materials, and add 3% of azeotropic agent A (methylene chloride) and 3% of azeotropic agent C (methyl trifluoroacetate).

[0063] Heat the mixture: Mix the tetrafluoropropanol and azeotropic agents evenly and heat to 50 °C.

[0064] Feed into a vacuum rectification column: Feed the mixture into a vacuum rectification column, set the temperature inside the column to 70 °C, the bottom temperature to 120 °C, and keep the pressure inside the column at 35 kPa.

[0065] Rectification process: Conduct conventional operations inside the rectification column, and the impurities are discharged from the top of the column with the azeotrope, but the ratio of azeotropic agents is not optimized.

[0066] Condensation and separation: Condense the azeotropic liquid at the top of the column through a condenser to separate the impurities and tetrafluoropropanol, but the separation efficiency is relatively low.

[0067] Secondary rectification: The bottom liquid continues to enter the secondary rectification column for further purification, and finally tetrafluoropropanol with relatively low purity is obtained, and the impurities cannot be effectively removed.

[0068] Compared with Example 3 in this comparative experiment, the key difference is that the ratio of azeotropic agents A and C is not optimized. In the experiment, the ratio of azeotropic agents A and C is not precisely adjusted, resulting in a relatively low removal efficiency of impurities and the purity of tetrafluoropropanol not being significantly improved. Through this comparison, the innovation of the present invention in optimizing the ratio of azeotropic agents can be highlighted, which improves the efficiency of impurity separation, thereby enhancing the product purity and yield.

[0069] Comparative Example 3: A rectification process using only a single azeotropic agent B Prepare raw materials: Take 100 L of tetrafluoropropanol raw materials with a purity of 98%.

[0070] Selection of azeotropic agent: Only use ethanol (azeotropic agent B) with a ratio of 4%, and do not use other azeotropic agents.

[0071] Rectification conditions: Feed the mixture into the rectification column, set the top temperature of the column to 70 °C, and set the pressure inside the column to 40 kPa.

[0072] Distillation operation: Tetrafluoropropanol and ethanol are azeotropically separated under low pressure conditions.

[0073] Separation results: When ethanol is used as the only azeotropic agent, the impurity removal effect is not as good as when three azeotropic agents are used together. The tetrafluoropropanol collected at the top of the tower has a lower purity and still has some impurities.

[0074] Further distillation: The bottom material continues to be distilled, but the purity cannot be significantly improved.

[0075] Compared with the scheme of using three entrainers (entrainers A, B and C) in Example 4, this comparative experiment only uses a single entrainer B, resulting in significantly lower impurity removal efficiency and limited improvement in the purity of tetrafluoropropanol. Through this comparison, it can be clearly pointed out that the combined use of multiple entrainers can significantly improve the impurity removal efficiency in the distillation process, thereby greatly improving the purity of the final product.

[0076] Comparative Example 4: Conventional atmospheric distillation process without vacuum distillation Prepare raw materials: Take 100L of tetrafluoropropanol raw material with a purity of 98%.

[0077] Distillation method: Do not use vacuum distillation, but directly use atmospheric distillation method to operate.

[0078] Distillation conditions: Tetrafluoropropanol was fed into a normal pressure distillation tower, the temperature inside the tower was set to 100°C, and the pressure inside the tower was set to normal pressure (101 kPa).

[0079] Distillation process: During the atmospheric distillation process, tetrafluoropropanol and impurities were not effectively separated. Impurities still passed through the top of the tower together with tetrafluoropropanol, making it difficult to form an efficient azeotropic separation.

[0080] Separation effect: The liquid at the top of the tower contains many impurities, and the purity of tetrafluoropropanol cannot be effectively improved.

[0081] Subsequent processing: Despite further condensation and distillation, the purity of the final product is still low and the impurities are not completely removed.

[0082] This comparative experiment uses an atmospheric distillation method. Compared with the vacuum distillation method used in the present invention, atmospheric distillation cannot effectively remove impurities, the purity improvement effect of tetrafluoropropanol is poor, and more processing steps are required. Through this comparison, it can be clearly pointed out that the advantages of vacuum distillation in removing impurities and improving product purity.

[0083] Comparative Example 5: Distillation process without using an azeotropic agent Prepare raw materials: Take 100L of tetrafluoropropanol raw material with a purity of 98%.

[0084] No azeotropic agent addition: Tetrafluoropropanol is directly fed into the distillation column without adding any azeotropic agent.

[0085] Rectification conditions: Set the temperature inside the rectification column to 60 °C and the pressure inside the column to 40 kPa.

[0086] Rectification process: Tetrafluoropropanol is subjected to conventional rectification without an azeotropic agent, and impurities are mixed with tetrafluoropropanol.

[0087] Separation effect: Due to the lack of an azeotropic agent to assist, the impurities cannot be effectively separated, the purity of tetrafluoropropanol is low, and a certain amount of impurities still remain.

[0088] Subsequent treatment: Tetrafluoropropanol needs to go through more rectification steps, and the effect of improving purity is not ideal.

[0089] This comparative experiment did not use an azeotropic agent. Different from Example 1 which used azeotropic agent B (ethanol), the lack of an azeotropic agent resulted in poor removal of impurities during the rectification process, and the purity of tetrafluoropropanol could not be effectively improved. Through this comparison, the important role of the azeotropic agent in impurity separation and product purity improvement during the rectification process can be highlighted.

[0090] Experiment 1: Compare the differences in the removal effect of fluorination by-products between Example 1 and Comparative Example 1 First, prepare two groups of experimental samples. One group is used as the experimental group and uses azeotropic agent B (ethanol), and the other group is used as the control group without adding any azeotropic agent.

[0091] For the experimental group (Example 1): Take 100 L of tetrafluoropropanol raw material with a purity of 98%.

[0092] Add ethanol (azeotropic agent B) in an amount of 4% of the total mass.

[0093] Feed the mixed liquid into the rectification column. The set temperature of the rectification column is 50 °C and the pressure is 40 kPa, and start the heating device.

[0094] Under this condition, tetrafluoropropanol and ethanol form an azeotrope, and the fluorination by-products are discharged from the top of the column along with the azeotrope.

[0095] The liquid at the top of the column is condensed by a condenser to separate impurities, and the rectified liquid is collected.

[0096] Analyze the purity of tetrafluoropropanol in the liquid and the removal effect of fluorination by-products.

[0097] For the control group (Comparative Example 1): Take 100 L of tetrafluoropropanol raw material with a purity of 98%, but do not add an azeotropic agent.

[0098] Feed the raw material directly into the rectification column. The temperature of the rectification column is set to 50 °C and the pressure is 40 kPa, and start the heating system.

[0099] Tetrafluoropropanol was subjected to conventional distillation, but without the help of an azeotropic agent, the impurities could not be removed as efficiently as in the experimental group.

[0100] The top liquid of the tower was collected by a condenser and analyzed for the purity of tetrafluoropropanol and the residual fluorination by-products.

[0101] Reference Figure 2 , the experimental results show that the use of entrainer B (ethanol) has significant advantages in vacuum distillation, and can more efficiently remove fluorinated by-products in tetrafluoropropanol. In the experimental group, ethanol and tetrafluoropropanol formed an azeotrope, and this process helped reduce the residual amount of fluorinated by-products. In contrast, the control group did not add an entrainer, resulting in a significant decrease in the impurity removal efficiency, and the removal rate of fluorinated by-products in the top liquid was only about 60%, and the purity was low. It is worth noting that the experimental group showed high stability in purity and impurity removal, and the yield was relatively high. This phenomenon is closely related to the formation mechanism of the azeotrope. Ethanol as an entrainer can effectively evaporate with tetrafluoropropanol, take away the by-products, and avoid the redeposition or reaction of the by-products.

[0102] From a mechanistic perspective, the use of entrainer B helps to fully utilize the volatility difference between tetrafluoropropanol and impurities, especially under reduced pressure conditions, where this difference is enhanced. The addition of ethanol increases the volatility of tetrafluoropropanol, allowing it to evaporate more efficiently with low-boiling impurities. In contrast, when no entrainer is used, the impurities are difficult to effectively remove during the distillation process due to the small relative volatility difference between tetrafluoropropanol and impurities, limiting the improvement in purity. The use of entrainers in reduced pressure distillation is the key to improving the purity of tetrafluoropropanol, especially in removing fluorination byproducts, where the effect is more significant.

[0103] Experiment 2: Comparison of the differences in purity improvement and impurity removal efficiency between Example 3 and Comparative Example 2 This experiment aims to verify whether optimizing the ratio of entrainer A (dichloromethane) and entrainer C (methyl trifluoroacetate) can improve the purity and impurity removal efficiency of tetrafluoropropanol. By comparing the experiment with unoptimized ratio, the significance of optimization is evaluated.

[0104] Experimental group (Example 3): Take 100L of tetrafluoropropanol (purity 98%).

[0105] Add azeotroping agent A (dichloromethane) 3% and azeotroping agent C (methyl trifluoroacetate) 2%.

[0106] After being fully mixed under stirring conditions, it is sent to a vacuum distillation tower.

[0107] The top temperature of the distillation tower is set to 70°C, the bottom temperature is set to 120°C, and the pressure inside the tower is set to 35 kPa.

[0108] Rectification is carried out, and the fluorination by-products and other impurities are discharged from the top of the column along with the azeotrope.

[0109] The liquid at the top of the column is cooled by a condenser to separate the impurities and recover high-purity tetrafluoropropanol.

[0110] Samples are taken to detect the purity of tetrafluoropropanol and the residual impurities.

[0111] Control group (Comparative Example 2): 100 L of tetrafluoropropanol (purity 98%) is taken.

[0112] 3% of azeotropic agent A (dichloromethane) and 3% of azeotropic agent C (methyl trifluoroacetate) are added.

[0113] Other rectification conditions are the same as those in the experimental group.

[0114] Due to the relatively high content of azeotropic agent C, the ability to separate impurities from the liquid collected at the top of the column is affected.

[0115] Samples are taken for analysis of the purity of tetrafluoropropanol and the impurity content.

[0116] The improvement brought by the optimized azeotropic agent ratio is not just a change in data, but an improvement in the entire separation mechanism. The experimental results clearly show that after slightly reducing the content of azeotropic agent C, the impurity removal rate has been significantly improved. The reason may be that excessive methyl trifluoroacetate will affect the relative volatility during rectification, making the separation of impurities from tetrafluoropropanol less thorough. Under the optimized scheme, the synergistic effect of the azeotropic agents is more reasonable, resulting in a decrease in the impurity content at the top of the column and a higher yield of tetrafluoropropanol.

[0117] Refer to the appendix Figure 3 , theoretically, the addition of azeotropic agents should help form a clearer difference in volatility between the target substance and impurities, thereby enhancing the separation ability of rectification. However, if the proportion of a certain azeotropic agent is too high, it may change the relative volatility of tetrafluoropropanol, causing it to partially remain at the bottom of the column and reducing the yield. The optimized experimental group clearly avoids this problem, and the combination of azeotropic agents A and C is more balanced, enabling the rectification column to more effectively separate tetrafluoropropanol and impurities under the operating conditions. The impurity removal rate has increased by nearly 20% compared to the control group, indicating that adjusting the azeotropic agent ratio is crucial for improving the separation efficiency.

[0118] In experiments with different batches, the impurity removal rate of the optimized scheme basically remained above 95%, while that of the unoptimized control group fluctuated greatly, hovering between 76% and 80%. This fluctuation may stem from the complex azeotropic behavior formed by impurities under the action of excessive azeotropic agent C, making it difficult to completely separate certain impurities during the rectification process. This instability precisely illustrates the limitations of the unoptimized scheme. The optimized scheme not only improves the purity of tetrafluoropropanol but also enhances the controllability of the entire process, making the final product more stable and predictable.

[0119] Experiment 3: Analyze the influence of different temperature conditions on the removal rate of fluorination by-products The purpose of the experiment is to observe the purity change of tetrafluoropropanol and the removal efficiency of fluorination by-products at different temperatures by adjusting the temperature of the rectification column. By changing the operating temperature, the influence of temperature on the removal of fluorination by-products can be more intuitively seen.

[0120] Experimental group (Example 4): Take 100 L of tetrafluoropropanol (purity 98%).

[0121] Heat the tetrafluoropropanol to 60 °C through a heating device and then feed it into a vacuum rectification column.

[0122] Set the pressure of the rectification column to 35 kPa and start the rectification process.

[0123] Set the top temperature of the column to 60 °C and the bottom temperature to 100 °C.

[0124] Collect the liquid at the top of the column and analyze the purity of tetrafluoropropanol and the impurity content in it.

[0125] Repeat the same experimental operation, set the top temperature of the column to 80 °C and 100 °C respectively, and record the purity of the product each time.

[0126] Control group (Comparative Example 3): Take 100 L of tetrafluoropropanol (purity 98%) and set the temperature to room temperature (about 20 °C).

[0127] Without heating, directly feed it into the rectification column, keep the bottom temperature at 60 °C, and set the top temperature to room temperature.

[0128] Maintain the room temperature operating conditions and carry out rectification treatment.

[0129] Record the purity of tetrafluoropropanol and the removal of fluorination by-products in the liquid collected at the top of the column.

[0130] Refer to the appendix Figure 4, seemingly temperature is just a simple operating variable, but in fact it plays a very subtle yet crucial role in the distillation process. The results of the experimental group clearly show that as the temperature at the top of the column increases, the purity of tetrafluoropropanol significantly improves, and the removal rate of impurities also increases accordingly. This phenomenon is closely related to the evaporation behavior of substances. At higher temperatures, the volatility of tetrafluoropropanol increases, and the distribution coefficient with other impurities changes, thus accelerating the separation process. Simply put, the higher the temperature, the easier it is for fluorination by-products to be carried away with the vapor, which is crucial for improving the purity of tetrafluoropropanol.

[0131] Compared with the normal-temperature distillation of the control group, the purity of the experimental group is always higher, which also corroborates the influence of temperature. The distillation process at normal temperature is less efficient, and the fluorination by-products do not completely volatilize, with a relatively large content of residual impurities. Such a situation indicates that without sufficient energy input, the separation efficiency of impurities and tetrafluoropropanol is low. Even if the operation time is extended, it is still difficult to effectively remove impurities. After increasing the temperature, the volatility of tetrafluoropropanol increases, making the separation of impurities and tetrafluoropropanol in the distillation process more thorough.

[0132] Considering the distillation mechanism, the increase in temperature makes the vapor pressure of tetrafluoropropanol increase, and the relative volatility difference with impurities is further expanded. At this time, the volatility of impurities is relatively low, and they are more likely to be retained in the bottom liquid of the column, while the higher-purity tetrafluoropropanol quickly rises to the top of the column.

[0133] Experiment 4: Analysis of the Distillation Effect of Tetrafluoropropanol under Different Pressure Conditions This experiment aims to study the removal rate of fluorination by-products and the change in purity during the distillation process of tetrafluoropropanol under different pressure conditions. The change in pressure during the distillation process has a significant impact on the relative volatility of vapor and liquid, and thus affects the separation effect of purity and impurities.

[0134] Experimental Group (Example 5) Take 100 L of tetrafluoropropanol (purity 98%) and feed it into a vacuum distillation column.

[0135] Set the pressure of the distillation column to 30 kPa, the temperature at the top of the column to 60 °C, and the temperature at the bottom of the column to 100 °C.

[0136] Start the distillation process and collect the liquid at the top of the column through a condenser.

[0137] Measure the purity and impurity content of tetrafluoropropanol and record the yield.

[0138] Repeat the experiment, set the pressure to 40 kPa and 50 kPa respectively, and record the results under different pressures.

[0139] Control Group (Comparative Example 4) Take 100 L of tetrafluoropropanol (purity 98%) and feed it into a vacuum distillation column.

[0140] Set the pressure of the distillation column to 60 kPa, the top temperature to 60 °C, and the bottom temperature to 100 °C.

[0141] Start the distillation process, collect the liquid at the top of the column, and measure the purity and impurity content of tetrafluoropropanol.

[0142] Compare the differences with the experimental group under high-pressure conditions and record the results.

[0143] Refer to Appendix Figure 5 , The experimental results show that as the pressure decreases, the purity of tetrafluoropropanol gradually increases, and the impurity removal rate also improves significantly. Especially at a pressure of 30 kPa, the purity reaches 99.4% and the impurity removal rate is 94%. This phenomenon is closely related to the difference in volatility between vapor and liquid under low pressure. Under low-pressure conditions, the vapor pressure of tetrafluoropropanol is higher, and its relative volatility increases, thus promoting its separation from impurities. The performance of the experimental group under low-pressure conditions is significantly better than that of the control group, and this difference emphasizes the important influence of pressure on the distillation process.

[0144] Analyzing from the mechanism, the effect of low-pressure distillation is better because as the pressure decreases, the difference in volatility between tetrafluoropropanol and impurities becomes more prominent. The low pressure increases the vapor pressure of tetrafluoropropanol, which helps to separate tetrafluoropropanol from impurities more effectively. Under high-pressure conditions, the vapor pressure of tetrafluoropropanol is lower, and the difference in volatility between impurities and tetrafluoropropanol decreases, resulting in a lower efficiency of the distillation process and incomplete removal of impurities.

[0145] For a distillation column, the change in pressure directly affects the operating state inside the column. Under high-pressure conditions, the gas-liquid equilibrium inside the distillation column is relatively stable, but this also means that impurities with lower volatility are difficult to be completely separated, affecting the final purity. In contrast, low-pressure operation not only increases the volatility of tetrafluoropropanol but also accelerates the removal of impurities. Low-pressure distillation can not only improve the yield but also increase the purity of the product, showing higher separation efficiency and better economy.

[0146] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-purity tetrafluoropropanol refining process, characterized in that: The following steps are involved: (1) Preliminary dehydration distillation: crude tetrafluoropropanol is added to the first distillation tower, distilled under normal pressure, and azeotropic agent A is added, and the bottom liquid is collected; (2) Vacuum distillation: the bottom liquid obtained in step (1) is sent to a second distillation tower, distilled at a pressure of 10-30 kPa, an azeotropic agent B is added, and the bottom liquid is collected; (3) High-purity distillation: The bottom liquid obtained in step (2) is sent to a third distillation tower for distillation at a pressure of 5-15 kPa, an azeotropic agent C is added, and the bottom liquid is collected to obtain high-purity tetrafluoropropanol.

2. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The preparation method of the entrainer A is prepared according to the following steps: Add methyl trifluoroacetate to a stirred reactor; At a temperature of 25-35°C, gradually add hexafluoroisopropanol and stir for 30 minutes; Solid impurities were removed by filtration to obtain a transparent liquid entrainer A.

3. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The preparation method of the entrainer B is prepared according to the following steps: Add hexafluoroisopropanol into a stirred reactor and heat to 30-40°C; Under stirring, add trimethyl phosphate and stir for 45-60 minutes; After cooling to room temperature, filter to obtain entrainer B.

4. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The preparation method of the entrainer C is prepared according to the following steps: Add trimethyl phosphate into the reaction kettle and stir at 20-30°C; Gradually add methyl trifluoroacetate and stir for 30-45 minutes; The transparent liquid entrainer C was obtained by filtration.

5. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The tower top temperature of the preliminary dehydration distillation is set at 55-65°C, the tower bottom temperature is set at 95-105°C, and the reflux ratio is controlled at 3-4.

6. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The tower top temperature of the vacuum distillation is maintained at 55-85°C, the tower bottom temperature is set at 105-125°C, and the negative pressure is controlled in the range of 15-25 kPa.

7. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The tower top temperature of the high-purity distillation is set at 70-90°C, the tower bottom temperature is maintained at 115-135°C, and the negative pressure is controlled in the range of 8-12 kPa.

8. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The addition ratio of the entrainer A is 3-5% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of methyl trifluoroacetate and hexafluoroisopropanol in the entrainer A is 4:

6.

9. The high-purity tetrafluoropropanol refining process according to claim 1, characterized in that: The addition ratio of the entrainer B is 4-6% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of hexafluoroisopropanol and trimethyl phosphate in the entrainer B is 7:

3.

10. The high-purity tetrafluoropropanol purification process according to claim 1, characterized in that: The addition ratio of the entrainer C is 2-4% of the total mass of the tetrafluoropropanol raw material, and the addition ratio of trimethyl phosphate and methyl trifluoroacetate in the entrainer C is 5.5:4.5.

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