A method for purifying perfluoroalkyl vinyl ethers

Abstract

The present application relates to rectification technical field, especially to a kind of purification method of perfluoroalkyl vinyl ether.The purification method includes: perfluoroalkyl vinyl ether crude product is mixed with purifying agent, and then rectification is carried out;Purifying agent includes one or several of inorganic base, organic base, strong base weak acid salt, basic salt, metal oxide, metal, hydride and drier;Wherein, the acid value of perfluoroalkyl vinyl ether crude product is 0.03~5.00mg NaOH / g, and water content is 0.010~0.100wt%.The present application can effectively remove acidic components in perfluoroalkyl vinyl ether crude product by optimizing rectification system, avoid abnormal subsequent polymerization reaction caused by product acidification;Also can greatly reduce the possibility of product acidification by removing moisture in perfluoroalkyl vinyl ether crude product;So that the purity of the perfluoroalkyl vinyl ether is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of distillation technology, and more particularly to a method for purifying perfluoroalkyl vinyl ethers. Background Technology

[0002] Perfluoroalkyl vinyl ethers are fluorinated vinyl ethers used as comonomers in the synthesis of fluoroplastics. They can participate in polymerization as comonomers or modifiers to improve certain properties of fluoropolymers, such as low-temperature resistance, solvent resistance, toughness, tear resistance, and adhesion to substrates, without altering the polymer's original corrosion resistance and aging resistance. Perfluoropropyl vinyl ether (PPVE) is a widely used fluorinated monomer, extensively used in the synthesis of fluoropolymers (such as PFA and PTFE) and fluorinated low-temperature rubbers. As an important comonomer, PPVE, due to its molecular characteristics, can effectively disrupt the crystallinity of copolymers such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), significantly improving certain properties of fluoropolymers, such as low-temperature resistance, toughness, tear resistance, and adhesion to substrates. Furthermore, PPVE can be used to introduce fluorine functional groups into organic molecules for applications in agriculture and pharmaceuticals.

[0003] Currently, the preparation of perfluoroalkyl vinyl ethers (PPVEs) still faces purification difficulties in the final distillation stage. For example, the main method for synthesizing PPVE at present is to use hexafluoropropylene oxide (HFPO) as a raw material, prepare perfluoro-2-propoxypropionyl fluoride in a polar solvent with a metal halide as a catalyst, then prepare PPVE through thermal cracking, and finally purify it by distillation to obtain the final product PPVE (reaction route see...). Figure 1 However, conventional distillation methods cannot effectively remove unreacted 2-propoxypropionic acid, obtained from the reaction of perfluoro-2-propoxypropionyl fluoride with water, as well as acids produced during the reaction. These substances can cause acidification of the PPVE product, severely affecting subsequent polymerization reactions.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the problems of existing technologies, this invention proposes a purification method for perfluoroalkyl vinyl ethers, which can achieve simple, efficient, and high-yield purification of perfluoroalkyl vinyl ethers.

[0006] This invention provides a method for purifying perfluoroalkyl vinyl ethers, comprising: mixing crude perfluoroalkyl vinyl ether with a purifying agent, and then performing distillation;

[0007] The purifying agent includes one or more of the following: inorganic base, organic base, strong base-weak acid salt, basic salt, metal oxide, metal, hydride, and desiccant.

[0008] The crude perfluoroalkyl vinyl ether has an acid value of 0.03–5.00 mg NaOH / g and a water content of 0.010–0.100 wt% based on the total mass of the crude perfluoroalkyl vinyl ether.

[0009] This invention discovers that, for crude perfluoroalkyl vinyl ethers with the above-mentioned acid value and moisture content, adding the purifying agent during distillation not only removes residual moisture from the crude perfluoroalkyl vinyl ethers by utilizing the purifying agent's own water absorption or reaction with water properties, preventing further hydrolysis of acyl fluoride with water to generate carboxylic acids, but also reacts with acidic substances in the system to generate high-boiling-point salts, ensuring that only low-boiling-point perfluoroalkyl vinyl ethers are obtained after distillation, thereby improving product purity and yield.

[0010] Preferably, the crude perfluoroalkyl vinyl ether has an acid value of 0.10–0.20 mg NaOH / g and a water content of 0.05–0.10 wt% based on the total mass of the crude perfluoroalkyl vinyl ether.

[0011] Preferably, the inorganic base includes one or more of monobasic, dibasic, and ternary bases.

[0012] More preferably, the monobasic alkali includes one or more of lithium hydroxide (LiOH), potassium hydroxide (KOH), and sodium hydroxide (NaOH).

[0013] More preferably, the binary base includes one or more of magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), strontium hydroxide (Sr(OH)2), copper hydroxide (Cu(OH)2), and zinc hydroxide (Zn(OH)2).

[0014] More preferably, the ternary alkali includes one or more of aluminum hydroxide (Al(OH)3), iron hydroxide (Fe(OH)3), and cobalt hydroxide (Co(OH)3).

[0015] Preferably, the organic base includes sodium methoxide (NaOCH3), sodium ethoxide (NaOC2H5), potassium ethoxide (KOC2H5), and potassium tert-butoxide (KO). t One or more of the following (Bu).

[0016] Preferably, the strong base weak acid salt includes one or more of carbonates, bicarbonates, sulfites, and bisulfites.

[0017] More preferably, the carbonate includes one or more of sodium carbonate (Na2CO3), potassium carbonate (K2CO3), and cesium carbonate (Cs2CO3).

[0018] More preferably, the bicarbonate includes sodium bicarbonate (NaHCO3) and / or potassium bicarbonate (KHCO3).

[0019] More preferably, the sulfite includes one or more of sodium sulfite (Na2SO3), potassium sulfite (K2SO3), and calcium sulfite (CaSO3).

[0020] More preferably, the bisulfite includes sodium bisulfite (NaHSO3) and / or potassium bisulfite (KHSO3).

[0021] Preferably, the basic salt includes basic magnesium chloride ([Mg(OH)Cl]) and / or basic copper carbonate ([Cu2(OH)2CO3]).

[0022] Preferably, the metal oxide includes one or more of calcium oxide (CaO), aluminum oxide (Al2O3), iron oxide (Fe2O3), ferrous oxide (FeO), magnesium oxide (MgO), and barium oxide (BaO).

[0023] Preferably, the metal includes sodium (Na) and / or magnesium (Mg).

[0024] Preferably, the hydride includes one or more of sodium hydride (NaH), calcium hydride (CaH2), and lithium aluminum hydride (LiAlH4).

[0025] Preferably, the desiccant includes one or more of the following: salt desiccant, alkali desiccant, oxide desiccant, metal desiccant, hydride desiccant, and other desiccant; the other desiccant includes molecular sieve and / or silica gel.

[0026] More preferably, the salt-based desiccant includes sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), calcium sulfate (CaSO4), copper sulfate (CuSO4), potassium carbonate (K2CO3), and calcium chloride (CaCl2); the alkali-based desiccant includes potassium hydroxide (KOH) and sodium hydroxide (NaOH); the oxide-based desiccant includes barium oxide (BaO), aluminum oxide (Al2O3), and calcium oxide (CaO); the metal-based desiccant includes sodium metal (Na); and the hydride-based desiccant includes calcium hydride (CaH2) and lithium aluminum hydride (LiAlH4).

[0027] Preferably, the mass ratio of the crude perfluoroalkyl vinyl ether to the purifying agent is 20 to 500:1.

[0028] More preferably, the mass ratio of the crude perfluoroalkyl vinyl ether to the purifying agent is 50 to 200:1.

[0029] Preferably, the purification method for the perfluoroalkyl vinyl ether specifically includes:

[0030] 500 parts of the crude perfluoropropyl vinyl ether were mixed with 1 to 25 parts of the purification agent, and the mixture was first subjected to total reflux, and then the perfluoroalkyl vinyl ether was collected at a reflux ratio of 5 to 200:1 (the parts are by weight).

[0031] Preferably, the distillation column has a theoretical plate number of not less than 10.

[0032] Preferably, the reflux ratio is 10 to 20:1 when collecting perfluoroalkyl vinyl ethers; more preferably, the reflux ratio is 10 to 15:1.

[0033] Preferably, the temperature of the total reflux is 30–80°C.

[0034] More preferably, the total reflux temperature is 30–50°C.

[0035] Preferably, the total reflux time is 2 to 10 hours; more preferably, the total reflux time is 4 to 6 hours.

[0036] Preferably, the crude perfluoroalkyl vinyl ether is obtained by dimerization of hexafluoropropylene oxide and thermal cracking reaction.

[0037] Preferably, the temperature is controlled at 30–50°C when collecting perfluoroalkyl vinyl ethers.

[0038] Preferably, the perfluoroalkyl vinyl ether is perfluoropropyl vinyl ether or perfluorobutyl vinyl ether.

[0039] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0040] This invention optimizes the distillation system to effectively remove acidic components from crude perfluoroalkyl vinyl ethers, avoiding abnormalities in subsequent polymerization reactions caused by product acidification. It also removes moisture from the crude perfluoroalkyl vinyl ethers, greatly reducing the possibility of acidification in the purified product, thereby significantly improving the purity and yield of the perfluoroalkyl vinyl ethers. Attached Figure Description

[0041] Figure 1 This is the method and route for synthesizing PPVE using hexafluoropropylene oxide (HFPO) as a raw material, as mentioned in the background technology. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Unless otherwise specified, all raw materials used in the embodiments are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0044] Example 1

[0045] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0046] In a 20L distillation vessel, 20kg of crude PPVE (GC content 95.5%, acid value 0.16mg NaOH / g, water content 0.055%) and 100g of potassium hydroxide were added. The mixture was refluxed at 50℃ for 4 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, the reflux ratio for PPVE collection was 10:1, the yield was 90%, the GC purity was 99.96%, the acid value was 0.015mg NaOH / g, and the water content was 0.0046%.

[0047] Example 2

[0048] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0049] In a 20L distillation vessel, 20kg of crude PPVE (GC content 94.8%, acid value 0.13mg NaOH / g, water content 0.064%) and 200g of potassium hydroxide were added. The mixture was refluxed at 50℃ for 4 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, the reflux ratio for PPVE collection was 10:1, the yield was 88%, the GC purity was 99.94%, the acid value was 0.010mg NaOH / g, and the water content was 0.0042%.

[0050] Example 3

[0051] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0052] In a 20L distillation vessel, 20kg of crude PPVE (GC content 94.4%, acid value 0.16mg NaOH / g, water content 0.055%) and 40g of potassium hydroxide were added. The mixture was refluxed at 50℃ for 4 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, a reflux ratio of 10:1, a yield of 91%, a GC purity of 99.95%, an acid value of 0.028mg NaOH / g, and a water content of 0.0058%.

[0053] Example 4

[0054] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0055] In a 20L distillation vessel, 20kg of crude PPVE (GC content 95.3%, acid value 0.14mg NaOH / g, water content 0.063%) and 200g of calcium oxide were added. The mixture was refluxed at 50℃ for 6 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, the reflux ratio for PPVE collection was 10:1, the yield was 89%, the GC purity was 99.94%, the acid value was 0.015mg NaOH / g, and the water content was 0.0033%.

[0056] Example 5

[0057] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0058] In a 20L distillation vessel, 20kg of crude PPVE (GC content 94.7%, acid value 0.16mg NaOH / g, water content 0.071%) and 200g of sodium sulfate were added. The mixture was refluxed at 50℃ for 6 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, a reflux ratio of 15:1 during PPVE collection, a yield of 86%, a GC purity of 99.93%, an acid value of 0.035mg NaOH / g, and a water content of 0.0027%.

[0059] Example 6

[0060] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0061] In a 20L distillation vessel, 20kg of crude PPVE (GC content 94.8%, acid value 0.14mg NaOH / g, water content 0.065%) and 200g of potassium hydroxide were added. The mixture was refluxed at 70℃ for 6 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, the reflux ratio during PPVE collection was 15:1, and the yield was 83%. The GC purity was 99.95%, the acid value was 0.012mg NaOH / g, and the water content was 0.0034%.

[0062] Example 7

[0063] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0064] In a 20L distillation vessel, 20kg of crude PPVE (GC content 95.4%, acid value 0.15mg NaOH / g, water content 0.068%) and 200g of potassium hydroxide were added. The mixture was refluxed at 70℃ for 8 hours, and then the PPVE was collected in a -30℃ cold bath. The distillation column had 12 theoretical plates, a reflux ratio of 15:1 during PPVE collection, a yield of 84%, a GC purity of 99.93%, an acid value of 0.011mg NaOH / g, and a water content of 0.0028%.

[0065] In practical implementation, other perfluoroalkyl vinyl ethers besides PPVE, such as perfluoron-n-butyl vinyl ether, can also achieve improved purity and purification effects comparable to those in the above examples when the purification method described in this invention is applied.

[0066] Comparative Example 1

[0067] This embodiment provides a method for purifying PPVE, which includes the following steps:

[0068] 20 kg of crude PPVE (GC content 95.1%, acid value 0.15 mg NaOH / g, water content 0.056%) was added to a 20 L distillation vessel and refluxed at 50 °C for 4 hours. The PPVE was then collected in a -30 °C cold bath. The distillation column had 12 theoretical plates, a reflux ratio of 10:1 during PPVE collection, a yield of 93%, a GC purity of 98.48%, an acid value of 0.060 mg NaOH / g, and a water content of 0.038%.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying a perfluoroalkyl vinyl ether, characterized by, The method comprises the following steps: 500 parts of crude perfluoropropyl vinyl ether is mixed with 1-25 parts of the purification agent, full reflux is first performed, and then perfluoroalkyl vinyl ether is collected at a reflux ratio of 10-20:1; the temperature of the full reflux is 30-80℃; The purification agent comprises one or more of monobasic alkali, calcium oxide, and salt drier; The crude perfluoroalkyl vinyl ether is obtained by dimerization of hexafluoropropylene oxide and thermal cracking reaction; the acid value of the crude perfluoroalkyl vinyl ether is 0.03-5.00 mg NaOH / g, and the water content is 0.010-0.100 wt% based on the total mass of the crude perfluoroalkyl vinyl ether.

2. The method of purifying a perfluoroalkyl vinyl ether according to claim 1, wherein The monobasic alkali comprises one or more of lithium hydroxide, potassium hydroxide, and sodium hydroxide.

3. The method of purifying a perfluoroalkyl vinyl ether according to claim 1, wherein The mass ratio of the crude perfluoroalkyl vinyl ether to the purification agent is 20-500:

1.

4. The method of purifying a perfluoroalkyl vinyl ether according to claim 3, wherein The mass ratio of the crude perfluoroalkyl vinyl ether to the purification agent is 50-200:

1.

5. The method of purifying a perfluoroalkyl vinyl ether according to any one of claims 1 to 4, wherein The full reflux temperature is 30-50℃.

6. The purification method of perfluoroalkyl vinyl ether according to any one of claims 1 to 4, characterized by, The full reflux time is 2-10h.

7. The method of purifying a perfluoroalkyl vinyl ether according to claim 6, wherein The full reflux time is 4-6h.

8. The method of purifying perfluoroalkyl vinyl ethers according to any one of claims 1 to 4, wherein When collecting the perfluoroalkyl vinyl ether, the temperature is controlled to be 30-50℃.

9. The method of purifying a perfluoroalkyl vinyl ether according to any one of claims 1 to 4, wherein The perfluoroalkyl vinyl ether is perfluoropropyl vinyl ether or perfluorobutyl vinyl ether.

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