CN116003210A - Preparation method of vinylidene fluoride monomer and vinylidene fluoride monomer - Google Patents
Preparation method of vinylidene fluoride monomer and vinylidene fluoride monomer Download PDFInfo
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Abstract
In order to solve the problem that the existing vinylidene fluoride preparation has carbon formation and pipeline blockage, the invention provides a vinylidene fluoride monomer preparation method and a vinylidene fluoride monomer, which comprises the following steps: obtaining carbonyl fluoride and a compound capable of easily generating ketene; mixing carbonyl fluoride and a compound capable of easily generating ketene, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product; purifying the crude vinylidene fluoride product to obtain a finished vinylidene fluoride monomer product; according to the preparation method of the vinylidene fluoride monomer, provided by the application, the carbonyl fluoride and the compound capable of easily generating ketene are adopted for the cracking reaction, the cracking reaction condition is mild, the carbon-forming blockage of reaction equipment is reduced, the equipment maintenance cost is reduced, the reaction state is stabilized, the production efficiency of the product is improved, and the productivity of the product is improved.
Description
Technical Field
The invention belongs to the technical field of fluoride engineering, and particularly relates to a preparation method of a vinylidene fluoride monomer and the vinylidene fluoride monomer.
Background
The vinylidene fluoride (VDF) monomer is mainly used for producing polyvinylidene fluoride resin, and can be copolymerized with hexachloropropene and tetrachloroethylene to produce fluororubber, and can also be copolymerized with perfluoroalkyl vinyl ether to produce oil-resistant low-temperature special rubber, etc.
Vinylidene fluoride (VDF) monomers are usually prepared from difluorochloroethane (HCFC-R142 b) by hollow tube cracking or inert gas dilution cracking, and then subjected to carbon removal, water washing, alkaline washing, compression, cold stripping and rectification to obtain vinylidene fluoride monomers (CN 102838447). The synthesis of vinylidene fluoride by using difluoro-chloroethane (HCFC-R142 b) is the most mature industrial production process at present, and most of the vinylidene fluoride is cracked in a nickel pipe at 600-700 ℃, so that the cracking temperature is high, coking and blocking of a pipeline are easy to generate, frequent shutdown and maintenance equipment are required, coke removal and carbon removal are required, the running cost of the equipment is greatly increased, and the difluoro-chloroethane (R142 b) can destroy an ozone layer and is strictly limited to be used in a production and circulation link. Therefore, it is of great importance to develop a new process for preparing vinylidene fluoride (VDF) monomers with mild reaction conditions.
In addition, US patent 3996301 uses tetrafluorocyclobutane as a raw material, adds inert gases such as helium, nitrogen and carbon tetrafluoride for dilution, and then reacts through a cracking tube at 500 ℃ to 900 ℃ to prepare vinylidene fluoride. The method has the problems of more byproducts, low selectivity, high energy consumption, easy carbon formation in the cracking tube and the like.
Disclosure of Invention
Aiming at the problem that the existing vinylidene fluoride preparation has carbon formation and pipeline blockage, the invention provides a vinylidene fluoride monomer preparation method and a vinylidene fluoride monomer.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for preparing vinylidene fluoride monomer, comprising the steps of:
obtaining carbonyl fluoride and a compound capable of easily generating ketene;
mixing carbonyl fluoride and a compound capable of easily generating ketene, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product;
purifying the crude vinylidene fluoride product to obtain a finished vinylidene fluoride monomer product;
the compounds which can easily generate the ketene comprise one or more of ketene, acetic anhydride, diketene, acetone and isopropenyl acetate.
Preferably, the cracking reaction step further includes a protective gas, and the specific cracking reaction step is as follows: mixing carbonyl fluoride, a compound which is easy to generate ketene and a protective gas, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product;
the molar ratio of the carbonyl fluoride, the compound capable of easily generating ketene and the protective gas is 1: (1.0-3): (0-2).
Preferably, the molar ratio of the carbonyl fluoride, the compound capable of easily generating ketene and the protective gas is 1: (1.1-1.5): (0.8-1.5).
Preferably, the shielding gas includes one or more of carbon dioxide, nitrogen, argon and helium.
Preferably, in the step of cracking reaction, the temperature of the cracking furnace is 380-600 ℃, and the cracking reaction time is 10-200 s.
Preferably, in the step of cracking reaction, the temperature of the cracking furnace is 400-550 ℃, and the cracking reaction time is 20-50 s.
Preferably, the steps of purification are alkali washing, water washing, drying and rectification in sequence.
Preferably, the alkaline washing comprises alkaline liquor, and the alkaline liquor comprises one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide;
the mass concentration of the alkali liquor is 0.1-50%.
Preferably, the material of the cracking tube is one or more selected from stainless steel, copper, monel alloy, hastelloy and high-nickel alloy.
On the other hand, the application provides a vinylidene fluoride monomer, which is prepared by the preparation method of the vinylidene fluoride monomer.
Advantageous effects
Compared with the prior art, the preparation method of the vinylidene fluoride monomer provided by the application adopts carbonyl fluoride and a compound capable of easily generating ketene to carry out a cracking reaction, the cracking reaction condition is mild, the carbon-forming blockage of reaction equipment is reduced, the equipment maintenance cost is reduced, the reaction state is stabilized, the production efficiency of the product is improved, the productivity of the product is improved, and the method is more suitable for high-efficiency industrial production.
Drawings
FIG. 1 is a gas chromatogram of vinylidene fluoride monomer prepared in example 1;
FIG. 2 is a mass spectrum of vinylidene fluoride monomer prepared in example 1.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a preparation method of vinylidene fluoride monomers, which comprises the following steps:
obtaining carbonyl fluoride and a compound capable of easily generating ketene;
mixing carbonyl fluoride and a compound capable of easily generating ketene, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product;
purifying the crude vinylidene fluoride product to obtain a finished vinylidene fluoride monomer product;
the compounds which can easily generate the ketene comprise one or more of ketene, acetic anhydride, diketene, acetone and isopropenyl acetate.
The existing vinylidene fluoride monomer production mostly adopts pyrolysis in a nickel pipe at 600-700 ℃, and the pyrolysis temperature is high, so that carbon formation is easy to generate and the pipeline is blocked. The inventor finds that the carbonyl fluoride and the compound which is easy to generate ketene are adopted for cracking reaction, the cracking reaction condition is mild, the coking blockage of reaction equipment can be reduced, the equipment maintenance cost is reduced, the reaction state can be stabilized, and the production efficiency and the productivity of products are improved. The preparation method of the vinylidene fluoride monomer can reduce the coking and blocking of the reaction equipment, does not need frequent shutdown maintenance equipment, does not need decoking and decarbonizing, can stabilize the reaction state, effectively improves the production capacity of the product, and is more suitable for high-efficiency industrial production.
The compounds which can easily generate the ketene comprise one or more of ketene, acetic anhydride, diketene, acetone and isopropenyl acetate.
The carbonyl fluoride and the compound which is easy to generate ketene are adopted for the cracking reaction, the cracking reaction temperature is low, the carbon-forming blockage of reaction equipment can be reduced, the equipment maintenance cost is reduced, the reaction state can be stabilized, and the production efficiency of products is improved.
In some embodiments, the cracking reaction step further includes a protective gas, and the cracking reaction step specifically includes: and mixing carbonyl fluoride, a compound capable of easily generating ketene and a protective gas, and introducing the mixture into a cracking tube for a cracking reaction to generate a crude vinylidene fluoride product.
The shielding gas is used for diluting raw materials and products, reducing the concentration of the raw materials and the products and reducing the generation of byproducts.
The molar ratio of the carbonyl fluoride, the compound capable of easily generating ketene and the protective gas is 1: (1.0-3): (0-2).
The molar ratio of the compounds which are easy to generate ketene is larger than or equal to that of carbonyl fluoride, so that the complete reaction of the carbonyl fluoride is ensured.
Specific molar ratios of carbonyl fluoride, compounds that readily produce ketene, shielding gas can be 1:1:1, 1:1.1:1, 1:1.4:1, 1:1.5:1, 1:1.8:1, 1:2.0:1, 1:2.3:1, 1:2.5:1, 1:3.0:1, 1:1.2:0.5, 1:1.2:0.8, 1:1.2:1.0, 1:1.2:1.2, 1:1.2:1.5, 1:1.2:1.7, 1:1.2:2.0, etc., provided that the molar ratio of carbonyl fluoride, compounds that readily produce ketene, shielding gas is satisfied at 1: (1.0-3): (0-2). When the content of the compound which is easy to generate ketene is more than 3mol, the material waste is caused by the adverse effect, and the purity of the prepared polyvinylidene fluoride is reduced. When the molar ratio of the shielding gas is higher than 2mol, the yield of the produced vinylidene fluoride monomer is lowered.
In some preferred embodiments, the molar ratio of carbonyl fluoride, ketene-prone compound, shielding gas is 1: (1.1-1.5): (0.8-1.5).
Carbonyl fluoride, a compound which is easy to generate ketene, and a molar ratio of a protective gas is 1: (1.1-1.5): (0.8-1.5) preferably, the method has higher yield under the condition of lower production cost, reduces side reaction and improves yield.
In some embodiments, the shielding gas comprises one or more of carbon dioxide, nitrogen, argon, and helium.
In some embodiments, in the step of cracking reaction, the temperature of the cracking furnace is 380-600 ℃, and the cracking reaction time is 10-200 s.
In some preferred embodiments, in the step of cracking reaction, the temperature of the cracking furnace is 400-550 ℃, and the cracking reaction time is 20-50 s.
According to the preparation method of the vinylidene fluoride monomer, the cracking reaction temperature is 380-600 ℃, and the preferred cracking reaction temperature is 400-550 ℃; compared with the prior art, the reaction temperature of the polyvinylidene fluoride monomer is lower than 600-700 ℃ in the prior art, equipment carbon formation blocking can be reduced, equipment maintenance running cost is reduced, and production efficiency is improved. Specifically, the cleavage reaction temperature may be 380 ℃, 400 ℃, 420 ℃, 450 ℃, 470 ℃, 490 ℃, 500 ℃, 510 ℃, 530 ℃, 560 ℃, 580 ℃, 600 ℃, or the like, as long as the cleavage reaction temperature is within the range of 380 to 600 ℃. If the cracking reaction temperature is lower than 380 ℃, the reactants do not completely react, and the yield of the prepared polyvinylidene fluoride is greatly reduced.
In some embodiments, the caustic wash comprises a caustic solution comprising one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide;
the mass concentration of the alkali liquor is 0.1% -50%;
in some embodiments, the steps of purifying are alkali washing, water washing, drying, rectifying.
Specifically, in the purification step, alkali liquor is used for alkali washing to collect carbon dioxide in the protective gas; the number of alkaline washes and the number of water washes are not limited, and may be selected according to actual conditions. The drying step is to utilize molecular sieve to dry and remove the water on the surface of the product. And then compressing the dried product to 0.5-2 Mpa by a compressor, collecting the product by-30 to-60 ℃ (negative sign represents minus) cold hydrazine to obtain a crude vinylidene fluoride product, and rectifying to obtain a finished vinylidene fluoride product. The specific rectification operation, with reference to the prior art, is not described here in detail.
In some embodiments, the material of the pyrolysis tube is selected from one or more of stainless steel, copper, monel, hastelloy, and high nickel alloy.
On the other hand, the application provides a vinylidene fluoride monomer, which is prepared by the preparation method of the vinylidene fluoride monomer.
The invention is further illustrated by the following examples.
Example 1
Acetic anhydride was vaporized by a preheater and then mixed with carbonyl fluoride and nitrogen in a molar ratio of 1.25:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), wherein the temperature of the cracking furnace is 400 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 102kg (1000 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at minus 40 ℃ to obtain a crude vinylidene fluoride product, and rectification to obtain 45.6kg of finished vinylidene fluoride product, wherein the purity of the finished vinylidene fluoride product is 99.95% in a gas chromatography test. FIG. 1 is a gas chromatogram and FIG. 2 is a mass spectrum showing a yield of 89.0% calculated as carbonyl fluoride, with no significant plugging or coking occurring for about 1200 hours of equipment operation.
Example 2
Acetic anhydride, after being vaporized by a preheater, was vaporized with carbonyl fluoride and nitrogen in a molar ratio of 1.1:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), the temperature of the cracking furnace is 400 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 89.8kg (880 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, drying by a molecular sieve, compressing to 1.2Mpa by a compressor, collecting by cold hydrazine at-40 ℃ to obtain a crude vinylidene fluoride product, rectifying to obtain 43.9kg of finished vinylidene fluoride product, wherein the gas chromatography test purity is 99.96%, calculated by carbonyl fluoride, the yield is 85.7%, and the continuous equipment operates for about 1200 hours without obvious blocking and coking phenomena.
Example 3
Example 3 is different from example 1 in that the kind of the compound that easily generates ketene is different, and the rest is the same as example 1. The method comprises the following specific steps:
after the diketene is vaporized by the preheater, the diketene is vaporized with carbonyl fluoride and nitrogen in a molar ratio of 1.25:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), wherein the temperature of the cracking furnace is 400 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 84kg (1000 mo 1) of diketene and 52.8kg (800 mol) of carbonyl fluoride are added. The crude reaction product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at-40 ℃ to obtain crude vinylidene fluoride, and rectification to obtain 46.6kg finished vinylidene fluoride with 99.89% purity. The yield was 91.1% calculated as carbonyl fluoride, and no significant plugging or coking occurred with continued equipment operation for about 1200 hours.
Example 4
After the diketene is vaporized by the preheater, the diketene is vaporized with carbonyl fluoride and nitrogen in a molar ratio of 1.5:1.0:1.5 into high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), cracking furnace temperature 550 ℃, gas residence time 30 seconds, cracking tube pressure-0.02 Mpa to 0.01Mpa, charging diketene 100.8kg (1200 mo 1) and carbonyl fluoride 52.8kg (800 mol). The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, drying by a molecular sieve, compressing to 1.2Mpa by a compressor, collecting by cold hydrazine at-40 ℃ to obtain a crude vinylidene fluoride product, rectifying to obtain 47.3kg of finished vinylidene fluoride product, wherein the purity of the gas chromatography test is 99.91%, calculated by carbonyl fluoride, the yield is 92.4%, and the continuous equipment operates for about 1500 hours without obvious blocking and coking phenomena.
Example 5
After the acetone is vaporized by the preheater, the acetone, carbonyl fluoride and nitrogen are mixed according to a molar ratio of 2.0:1.0:2.0 into high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), cracking furnace temperature of 580 deg.C, gas residence time of 30 seconds, cracking tube pressure of-0.02 Mpa to 0.01Mpa, cumulative feeding acetone 92.8kg (1600 mo 1), carbonyl fluoride 52.8kg (800 mol). The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, drying by a molecular sieve, compressing to 1.2Mpa by a compressor, collecting by cold hydrazine at-40 ℃ to obtain a crude vinylidene fluoride product, rectifying to obtain 40.3kg of finished vinylidene fluoride product, wherein the gas chromatography test purity is 99.87%, calculated by carbonyl fluoride, the yield is 78.8%, and the continuous equipment is operated for 1800 hours without obvious blocking and coking phenomena.
Example 6
Acetic anhydride, after being vaporized by a preheater, was vaporized with carbonyl fluoride, nitrogen in a molar ratio of 3.0:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), wherein the temperature of the cracking furnace is 600 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 244.8Kg (2400 mo 1) of isopropenyl acetate and 52.8Kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, drying by a molecular sieve, compressing to 1.2Mpa by a compressor, collecting by cold hydrazine at-40 ℃ to obtain a crude vinylidene fluoride product, rectifying to obtain 45.9kg of finished vinylidene fluoride product, wherein the gas chromatography test purity is 99.92%, calculated by carbonyl fluoride, the yield is 89.7%, and the continuous equipment operates for about 1800 hours, so that obvious coking phenomenon exists.
Example 7
Example 7 is the same as most of the steps of example 1 except that no nitrogen is present. The method comprises the following specific steps:
after the acetic anhydride was vaporized by the preheater, it was mixed with carbonyl fluoride in a molar ratio of 1.25:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), wherein the temperature of the cracking furnace is 400 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 102kg (1000 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at minus 40 ℃ to obtain a crude vinylidene fluoride product, and rectification to obtain 47.6kg of finished vinylidene fluoride product, wherein the purity of the finished vinylidene fluoride product is 99.81% in a gas chromatography test. The yield was 93% calculated as carbonyl fluoride and the coking was evident from the continuous equipment operation for about 800 hours.
Example 8
Acetic anhydride was vaporized by a preheater and then mixed with carbonyl fluoride and nitrogen in a molar ratio of 1.25:1.0:3.0 into high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), cracking furnace temperature 400 ℃, gas residence time 30 seconds, cracking tube pressure-0.02 Mpa to 0.01Mpa, charging 102kg (1000 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at minus 40 ℃ to obtain a crude vinylidene fluoride product, and rectification to obtain 41.6kg of finished vinylidene fluoride product, wherein the purity of the finished vinylidene fluoride product is 99.96% in a gas chromatography test. Calculated by carbonyl fluoride, the yield is 81.3 percent, and the equipment is operated for about 2000 hours without obvious blockage and coking.
Example 9
Example 9 is compared with example 1, the acetic anhydride content being 3.5mol; the rest is the same as in example 1, the specific steps are as follows:
acetic anhydride, after being vaporized by a preheater, was vaporized with carbonyl fluoride and nitrogen in a molar ratio of 3.5:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), the temperature of the cracking furnace is 400 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 285.6kg (2800 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at-40 ℃ to obtain a crude vinylidene fluoride product, and rectification to obtain 46.2kg of finished vinylidene fluoride product, wherein the purity of the finished vinylidene fluoride product is 99.93% in a gas chromatography test. The yield was 90.2% calculated as carbonyl fluoride and no significant plugging and coking occurred for about 2100 hours of continuous plant operation.
Example 10
Example 10 compared to example 1, the furnace temperature was 300 ℃, and the remainder was the same as example 1, with the following specific steps:
acetic anhydride was vaporized by a preheater and then mixed with carbonyl fluoride and nitrogen in a molar ratio of 1.25:1.0:1.0 into a high nickel alloy cracking tube (diameter: 20mm, tube length 2 m), wherein the temperature of the cracking furnace is 300 ℃, the gas residence time is 30 seconds, the pressure of the cracking tube is-0.02 Mpa to 0.01Mpa, 102kg (1000 mo 1) of acetic anhydride and 52.8kg (800 mol) of carbonyl fluoride are added. The reaction crude product is subjected to alkali washing by 30% sodium hydroxide aqueous solution with mass concentration, water washing, molecular sieve drying, compression to 1.2Mpa by a compressor, cold hydrazine collection at minus 40 ℃ to obtain a crude vinylidene fluoride product, rectification to obtain 16.6kg of finished vinylidene fluoride product, and gas chromatography test purity of 99.87%. The yield was 32.5% calculated as carbonyl fluoride, and no significant plugging or coking occurred for about 1200 hours of continuous equipment operation.
Examples 1, 2, 6 and 9 are compared, the molar content of the ketene-easily-generating compound in example 9 is higher than 3mol,
when the molar ratio of carbonyl fluoride, a compound capable of easily generating ketene and a protective gas is 1: (1.1-1.5): in the range of (0.8-1.5), the prepared vinylidene fluoride monomer product has higher purity.
In comparison with example 7, example 1 shows that no shielding gas is used in the reaction of example 7, the yield of example 7 is increased, and the product purity is reduced, but the running time of the equipment is greatly reduced, which means that adding shielding gas in the reaction can reduce byproducts, improve the product purity, improve the yield and increase the running time of the equipment. Example 1 compared with example 8, the run time of the apparatus and the product purity were increased, but the yield of the product was decreased, indicating that the molar ratio of carbonyl fluoride, compounds liable to generate ketene, and shielding gas added during the reaction was not excessive, at 1: (1.0-3): in the range of (0-2), the method has higher yield and better equipment operation time and purity. Example 1 is compared with example 9, and the reduced purity of vinylidene fluoride produced in example 9 indicates that the molar ratio of carbonyl fluoride to the compounds liable to form ketene is higher than 1: (1-3) decreasing the purity of the resulting polyvinylidene fluoride, it is presumed that the side reaction increases, and the purity of the resulting product decreases. In example 1 versus example 10, the cracking temperature of example 10 was lower than 380 ℃, although no significant plugging or coking occurred during the continuous operation of the apparatus for about 1200 hours, the product yield was greatly reduced, indicating that the reaction temperature was lower than 380 ℃, the reactants did not fully react, and the production efficiency was reduced. Examples 1, 2 and 6 comparative examples, the molar ratio of carbonyl fluoride, compounds liable to generate ketene, and protective gas is 1: (1.1-1.5): when the ratio is in the range of (0.8 to 1.5), the purity of polyvinylidene fluoride produced by the reaction is higher. In comparison of examples 1 and 3, the compounds which are easy to generate ketene are different in type, the purity and the yield of polyvinylidene fluoride are not greatly different, no obvious blocking or coking phenomenon occurs in the operation of equipment, and the compounds which are included in the compounds which are easy to generate ketene are suitable for the preparation of the application. Comparison of examples 3 and 4 shows that the purity and the yield of the prepared polyvinylidene fluoride are increased by improving the content of the compound which is used for protecting gas and generating ketene easily, and the equipment is operated for 1500 hours without obvious blocking and coking phenomena.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. A method for preparing vinylidene fluoride monomer, comprising the steps of:
obtaining carbonyl fluoride and a compound capable of easily generating ketene;
mixing carbonyl fluoride and a compound capable of easily generating ketene, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product;
purifying the crude vinylidene fluoride product to obtain a finished vinylidene fluoride monomer product;
the compounds which can easily generate the ketene comprise one or more of ketene, acetic anhydride, diketene, acetone and isopropenyl acetate.
2. The method for preparing vinylidene fluoride monomer according to claim 1, wherein the step of cracking reaction further comprises a protective gas, and the step of cracking reaction comprises: mixing carbonyl fluoride, a compound which is easy to generate ketene and a protective gas, and introducing the mixture into a cracking tube for cracking reaction to generate a crude vinylidene fluoride product;
the molar ratio of the carbonyl fluoride, the compound capable of easily generating ketene and the protective gas is 1: (1.0-3): (0-2).
3. The method for producing vinylidene fluoride monomer according to claim 2, wherein the molar ratio of carbonyl fluoride, a compound liable to generate ketene, and a shielding gas is 1: (1.1-1.5): (0.8-1.5).
4. The method for producing vinylidene fluoride monomer according to claim 2, wherein the shielding gas comprises one or more of carbon dioxide, nitrogen, argon and helium.
5. The method for preparing vinylidene fluoride monomer according to claim 1, wherein in the step of cracking reaction, the temperature of the cracking furnace is 380-600 ℃ and the cracking reaction time is 10-200 s.
6. The method for producing vinylidene fluoride monomer according to claim 5, wherein in the step of cracking reaction, the temperature of the cracking furnace is 400 to 550 ℃ and the cracking reaction time is 20 to 50s.
7. The method for producing vinylidene fluoride monomer according to claim 1, wherein the purification steps are alkali washing, water washing, drying and rectification in this order.
8. The method for preparing vinylidene fluoride monomer according to claim 7, wherein the alkali washing comprises alkali liquor comprising one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide;
the mass concentration of the alkali liquor is 0.1-50%.
9. A vinylidene fluoride monomer prepared by the method of any one of claims 1 to 8.
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