Synthetic method of acetic acid 2, 2-difluoroethyl ester

Abstract

The invention belongs to the technical field of chemical synthesis, and particularly relates to a synthesis method of acetic acid 2, 2-difluoroethyl ester, which specifically comprises the following steps: under the catalysis of a reaction catalyst, continuously reacting 2-chloro-1, 1-difluoroethane, alkali metal acetate and a solvent at the reaction temperature of 140-200 DEG C, and carrying out solid-liquid separation and rectification treatment on a crude product after the reaction to obtain the acetic acid 2, 2-difluoroethyl ester. The synthesis method is simple in technological process and easy to operate, the synthesized acetic acid 2, 2-difluoroethyl ester is high in purity, the conversion rate of the reaction raw material alkali metal acetate is high, meanwhile, the solvent, the unreacted alkali metal acetate and the 2-chloro-1, 1-difluoroethane in the synthesis method can be repeatedly used, and the synthesis method is suitable for industrial production. The high conversion rate of the alkali metal acetate and the high selectivity of the acetic acid 2, 2-difluoroethyl ester are not influenced, the recovery cost and the reaction cost are greatly reduced, and large-scale chemical application is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis and more specifically relates to a method for synthesizing 2,2-difluoroethyl acetate. Background Art

[0002] With the rapid development of electric vehicles, higher energy density, wider operating temperature, better safety, higher rate performance and lower price are the main development directions of lithium batteries in the future. Fluorinated solvents are excellent battery electrolyte additives. They form a thin and flexible solid electrolyte interface film (SEI film) in lithium batteries, which can better withstand the battery shrinkage and expansion caused by lithium deposition and lithium extraction during battery cycling. In addition, the SEI surface film formed by fluorinated solvents ensures uniform, dendrite-free lithium deposition, thereby ensuring the reversible behavior of the lithium negative electrode and improving the lithium dendrite growth that pierces the diaphragm and causes battery short circuit. 2,2-Difluoroethyl acetate is a fluorinated solvent that can be used as an additive for battery electrolytes to improve the high temperature, room temperature and low temperature cycle performance of the battery, while improving the battery safety performance.

[0003] There are few methods for synthesizing 2,2-difluoroethyl acetate disclosed so far, and it generally appears as an intermediate product in the production of 2,2-difluoroethanol. For example, Chinese patent application CN112645796A provides a method for synthesizing 2,2-difluoroethanol. In the patent application, 2-chloro-1,1-difluoroethane (R142) and alkali metal acetate are used as reaction raw materials to react in a solvent to generate 2,2-difluoroethyl acetate. To activate 2-chloro-1,1-difluoroethane, a catalyst (sodium iodide, potassium iodide, sodium bromide or potassium bromide, NR4 + The quaternary ammonium salt in the form of X) is added to the mixture of the alkali metal salt of acetic acid and the solvent for catalytic reaction. The catalyst added in the above reaction is dissolved in the solvent, so the reaction can only be carried out by an intermittent method, that is, R142, alkali metal acetate, catalyst, and solvent are put into the reactor in a certain proportion. After the reaction is completed, the reaction is stopped, and the materials in the reactor are transferred out for separation. After the by-products and 2,2-difluoroethyl acetate are separated, the remaining raw materials and catalyst are returned to the reactor for the next reaction.

[0004] Therefore, the following disadvantages exist: the reaction time of the intermittent reaction is long, the production efficiency is not high, the energy consumption per unit product is high, and the process route is complicated; the reaction raw materials, reaction products and catalysts are all dissolved in the solvent DMF, and the subsequent separation of the reaction is difficult, and the production cost is high; there is loss of the catalyst, and the production cost becomes high; due to the low boiling point of R142, the reaction pressure is high, which increases the equipment investment cost and the danger of employee operation; the subsequent separation of the reaction is difficult, resulting in the inability to accurately control the material ratio during recycling, and the batch reaction is unstable, which ultimately leads to lower and lower product output and alkali metal acetate conversion rate, increasing energy consumption, and increasing production costs. It is difficult to achieve precise control of the production process. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the existing 2,2-difluoroethyl ester synthesis method and the backward status of the existing synthesis process, and provide a new synthesis method of 2,2-difluoroethyl acetate.

[0006] Another object of the present invention is to provide an application of the reaction catalyst in improving the conversion rate of alkali metal acetate and / or the selectivity of 2,2-difluoroethyl acetate.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A method for synthesizing 2,2-difluoroethyl acetate, comprising the steps of: reacting 2-chloro-1,1-difluoroethane, alkali metal acetate and a solvent continuously at 140-200° C. under the catalysis of a reaction catalyst, and performing post-treatment to obtain 2,2-difluoroethyl acetate;

[0009] The preparation method of the reaction catalyst is as follows: chromium salt, or chromium salt and other metal salts contained in the system are mixed, an alkaline solution is added for co-precipitation, and the pH is controlled to be 9-10, the precipitate is washed, dried, and calcined in an inert gas atmosphere at 300-400°C;

[0010] The other metal salts are one or more of aluminum salts, cobalt salts, magnesium salts, zinc salts, and indium salts.

[0011] The invention provides a method for synthesizing 2,2-difluoroethyl acetate, which can carry out continuous reaction under normal pressure, and significantly improves the conversion rate of alkali metal acetate by adopting a special reaction catalyst to catalyze the esterification reaction of R142 (2-chloro-1,1-difluoroethane) and alkali metal acetate.

[0012] The present invention utilizes a coprecipitation reaction and calcination under the protection of a high-purity inert gas to prevent the pore size collapse of the reaction catalyst caused by deep oxidation of the metal oxide, which leads to a decrease in specific surface area, pore volume, and average pore size, and ultimately leads to a decrease in catalytic performance. The metal oxide reaction catalyst finally obtained by the present invention has a large specific surface area, pore volume, and average pore size, which can effectively increase the contact area between the reaction raw materials and the catalyst, improve the reaction catalytic efficiency, and the purity of the metal oxide can reach more than 99.9%, reduce the occurrence of side reactions, and improve the selectivity of 2,2-difluoroethyl acetate.

[0013] In addition, the esterification reaction of the present invention has almost no side reactions, and the incompletely reacted R142, alkali metal acetate and solvent can be reused to continue to participate in the reaction without affecting the conversion rate of alkali metal acetate and the selectivity of 2,2-difluoroethyl acetate, thereby greatly improving the reaction efficiency, achieving high raw material utilization and reducing the industrial production cost.

[0014] The synthesis method provided by the present invention can carry out continuous reaction under normal pressure, has high safety, stable process control, simple device flow, low product unit consumption, low energy consumption, and is very suitable for industrial production. Compared with the existing batch reaction synthesis of 2,2-difluoroethyl acetate, under the same volume reactor, the average daily output of 2,2-difluoroethyl acetate can be increased by more than 5 times.

[0015] Preferably, 2-chloro-1,1-difluoroethane, alkali metal acetate and solvent are continuously reacted through a fixed bed reactor filled with a catalyst.

[0016] Preferably, the reactor temperature rise rate is ≤10°C to prevent the catalyst in the fixed bed reactor from being damaged due to thermal expansion and contraction.

[0017] Preferably, the specific surface area of ​​the reaction catalyst is ≥400m 2 / g, pore volume ≥ 0.5mL / g, average pore diameter ≥ 5.2nm. More preferably, the specific surface area of ​​the reaction catalyst is 400-600m 2 Specifically, the specific surface area of ​​the reaction catalyst is 400, 425, 450, 475, 500, 525, 550, 575, 600 m 2 / g, or any range formed by the above values, such as 400~425m 2 / g, 400~475m 2 / g, 425~525m 2 / g, etc., but the present invention is not limited thereto.

[0018] The reaction catalyst of the present invention is a metal oxide catalyst, which is composed of a main catalyst and an auxiliary catalyst. The main catalyst contains metal chromium; the auxiliary catalyst contains one or more of metals selected from aluminum, cobalt, magnesium, zinc and indium.

[0019] Preferably, the other metal salts are aluminum salts, cobalt salts, magnesium salts, zinc salts and indium salts.

[0020] More preferably, the mass ratio of chromium atoms, aluminum atoms, cobalt atoms, magnesium atoms, zinc atoms, and indium atoms in the reaction catalyst is 21.7: 0.67-0.74: 1.66-1.84: 1.00-1.11: 1.37-1.51: 0.95-1.05. The inventors have found through a large number of experiments that when the reaction catalyst contains chromium oxide, aluminum oxide, cobalt oxide, magnesium oxide, zinc oxide, and indium oxide, and the mass ratio of metal atoms meets the above ratio, the conversion rate of alkali metal acetate is above 98%, and the purity of the prepared 2,2-difluoroethyl acetate is above 98.9%.

[0021] Specifically, the mass ratio of chromium atoms, aluminum atoms, cobalt atoms, magnesium atoms, zinc atoms, and indium atoms in the reaction catalyst is 21.7: 0.7-0.74: 1.75-1.84: 1.06-1.11: 1.44-1.51: 1-1.05. Studies have found that when the mass ratio of each metal atom in the reaction catalyst is within this range, the conversion rate of alkali metal acetate is above 99.4%, and the purity of the prepared 2,2-difluoroethyl acetate is ≥99.99%.

[0022] Preferably, the purity of the 2-chloro-1,1-difluoroethane is ≥99.5%, and the water content is ≤10 PPM. Controlling the purity and water content of the reaction raw materials can increase the reaction speed and prevent the alkali metal chloride generated by the reaction from causing salt corrosion to the equipment when the water content is high.

[0023] Preferably, the solvent purity is ≥99.5% and the water content is ≤10PPM.

[0024] Preferably, the reaction temperature is 150-180°C.

[0025] Preferably, the alkali metal acetate is sodium acetate or potassium acetate.

[0026] Preferably, the solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide (DMF), N,N-dimethylacetamide, and N,N-dibutylformamide.

[0027] Preferably, the molar ratio of the alkali metal acetate to 2-chloro-1,1-difluoroethane is 1:(1.5-2.5).

[0028] Preferably, the molar ratio of the alkali metal acetate to the solvent is 1:(2-3).

[0029] Preferably, the post-treatment is condensation, filtration, collection of filtrate, distillation, and drying.

[0030] More preferably, the distillation is divided into two times, and the process parameters of the first distillation are: heating at normal pressure to a temperature greater than or equal to the boiling point of 2-chloro-2,1-difluoroethane and less than the boiling point of 2,2-difluoroethyl acetate; specifically, heating to 35-37° C. in the present invention (at this temperature, 2-chloro-1,1-difluoroethane will not be decomposed by high temperature and can be effectively recovered), so that the unreacted 2-chloro-1,1-difluoroethane in the filtrate is first distilled out; then the remaining filtrate is distilled twice, heated to a temperature greater than or equal to 98° C., which is the boiling point of 2,2-difluoroethyl acetate, and less than the boiling point of the solvent; specifically, heating to 98-110° C. in the present invention (at this temperature, 2,2-difluoroethyl acetate will not be decomposed by high temperature), so that the 2,2-difluoroethyl acetate in the filtrate is distilled out.

[0031] The condensation, filtration, collection of filtrate, distillation, and drying of the present invention are conventional operations in the art. Specifically, the post-treatment is condensation to crystallize the reaction by-product alkali metal chloride, and then filtering and collecting the filtrate for primary distillation, recycling the unreacted liquid phase R142 for reuse, and then performing secondary distillation on the remaining solution after the primary distillation, and then drying to obtain 2,2-difluoroethyl acetate.

[0032] Preferably, the chromium salt is one or more of CrCl3·6H2O, Cr(NO3)3·9H2O, and Cr2(SO4)3; the aluminum salt is one or more of Al(NO3)3·9H2O, AlCl3, and Al2(SO4)3; the cobalt salt is one or more of CoCl2·6H2O, Co(NO3)2·9H2O, and CoSO4; the magnesium salt is one or more of MgCl2, Mg(NO3)2·6H2O, and MgSO4; the zinc salt is one or more of ZnCl2, Zn(NO3)2, and ZnSO4; and the indium salt is one or both of In(NO3)3·H2O and In2(SO4)3.

[0033] Preferably, the calcination is followed by crushing, sieving and granulation to finally obtain a reaction catalyst with a compressive strength of >100 N. The strength of the reaction catalyst granulation must be ensured, and the catalyst compressive strength of >100 N can prevent the catalyst from being damaged during long-term use and extend the service life of the catalyst.

[0034] Preferably, the alkaline solution is a solution of adding chemically pure ammonia water with a mass concentration of 20-25% to pure water.

[0035] More preferably, the calcination time is 2 to 4 hours.

[0036] Preferably, the calcination temperature is 350-370°C.

[0037] Preferably, the inert gas is one of nitrogen, argon or helium.

[0038] Furthermore, the present invention provides the use of a reaction catalyst in improving the conversion rate of alkali metal acetate and / or the selectivity of 2,2-difluoroethyl acetate.

[0039] The preparation method of the reaction catalyst is as follows: chromium salt, or chromium salt and other metal salts contained in the system are mixed, an alkaline solution is added to a pH of 9 to 10, a precipitation reaction is performed, the precipitate is washed, dried, and calcined in an inert gas atmosphere at 300 to 400°C;

[0040] The other metal salts are one or more of aluminum salts, cobalt salts, magnesium salts, zinc salts, and indium salts.

[0041] The present invention has the following beneficial effects:

[0042] 1. The present invention provides a method for synthesizing 2,2-difluoroethyl acetate, which can perform continuous reaction under normal pressure. By adopting a specific reaction catalyst R142 and an esterification reaction of an alkali metal acetate, the conversion rate of the alkali metal acetate and the selectivity of 2,2-difluoroethyl acetate are both very high.

[0043] 2. The synthesis method of the present invention is simple to operate, can be continuously reacted under normal pressure, is green and safe, and compared with the conventional intermittent reaction in the prior art to synthesize 2,2-difluoroethyl acetate, with the same volume of reactor, the daily product output of the present invention can be increased by more than 5 times.

[0044] 3. The solvent, unreacted alkali metal acetate and 2-chloro-1,1-difluoroethane in the synthesis method of the present invention can be recovered and reused to synthesize 2,2-difluoroethyl acetate without affecting the conversion rate of alkali metal acetate and the selectivity of 2,2-difluoroethyl acetate. At the same time, sodium chloride produced as a by-product in the synthesis process can be sold to the chlor-alkali industry for use as a raw material, which greatly reduces production energy consumption and unit product cost, has significant economic efficiency, and is conducive to a wide range of chemical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of a reaction device for preparing 2,2-difluoroethyl acetate in an embodiment of the present invention.

[0046] The markings in the figure are as follows:

[0047] 1-R142 storage tank; 2-mixing tank A; 3-mixing tank B; 4-metering pump A; 5-metering pump B; 6-mass flowmeter A; 7-mass flowmeter B; 8-static mixer; 9-shell-and-tube reactor; 91-spray distributor; 92-stainless steel spring; 93-shell-and-tube; 94-jacket; 95-temperature monitoring device; 96-pressure detection device; 97, 98-temperature monitoring device; 10-shell-and-tube condenser; 11-filter-dryer-conveyor integrated machine; 12-filtrate collecting tank; 13-centrifugal pump; 14-distillation tower A; 15-distillation tower B; 16-drying tower; 17-product storage tank. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0049] In the present invention, "2-chloro-1,1-difluoroethane" is abbreviated as "R142".

[0050] Figure 1 The present invention is a reaction device in actual production: the mixing tank A2 and the mixing tank B3 are connected in parallel, and then connected to the metering pump A4, the mass flowmeter A6 and the static mixer 8 in sequence; the R142 storage tank 1 is connected to the metering pump B5, the mass flowmeter B7 and the static mixer 8 in sequence; the static mixer 8 mixes the raw materials from the mixing tank A2, the mixing tank B3 and the R142 storage tank 1, the static mixer 8 is connected to one end of the shell-and-tube reactor 9, and the other end of the shell-and-tube reactor 9 is connected to the shell-and-tube condenser 10, the filtering, drying and conveying integrated machine 11, the filtrate collecting tank 12, the centrifugal pump 13, and the distillation tower A14 in sequence; the upper end of the distillation tower A14 is connected to the R142 storage tank 1, and the lower end is connected to the distillation tower B15; the upper end of the distillation tower B15 is connected to the drying tower 16 and the product storage tank 17 in sequence, and the lower end is connected to the mixing tank A2 and the mixing tank B3.

[0051] Among them, there are multiple tubes 93 in the tube-in-tube reactor 9, and a stainless steel spring 92 is installed at the lower end of each tube 93, and then a spherical reaction catalyst is added from the upper end until the tubes 93 are filled; a spray distributor 91 is also provided in the tube-in-tube reactor 9 to allow the mixed liquid flowing in through the static mixer 8 to be evenly distributed to the tubes 93 containing reaction catalysts inside the tube-in-tube reactor 9; the tube-in-tube reactor 9 is also provided with a jacket 94, and heat transfer oil is passed into the jacket 94 to control the temperature inside the tube-in-tube reactor 9; at the same time, a plurality of temperature monitoring devices 95, 97, 98 and a pressure detection device 96 are also provided in the tube-in-tube reactor 9.

[0052] The tube-in-tube condenser 10 is connected to the tube-in-tube reactor 9 , and a temperature monitoring device 101 is arranged in the middle; the tube-in-tube condenser 10 is connected to the filtering, drying and conveying integrated machine 11 , and a temperature monitoring device 102 is also arranged in the middle.

[0053] In a specific embodiment of the present invention, the lower end of the shell-and-tube reactor 9 may not be connected to the shell-and-tube condenser 10, and the mixed liquid after the reaction flowing out of the lower end of the shell-and-tube reactor 9 is directly collected in a clean container.

[0054] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0055] Example 1

[0056] Preparation of reaction catalyst: Take CrCL3·6H2O, Al(NO3)3·9H2O, CoCl2·6H2O, MgCl2, Zn(NO3)2, In(NO3)3·H2O according to the mass ratio of Cr:Al:Co:Mg:Zn:In of 21.7:0.7:1.75:1.06:1.44:1, add to water and dissolve completely, stir, and drop 25% chemically pure ammonia water, control the pH of the final solution to 9-10, stir and react for 15 minutes, take the precipitate, wash with pure water until the pH of the filtered water is 7, dry at 110℃ for 24 hours, and then roast at 360℃ for 3 hours in a nitrogen atmosphere (the roasting temperature rate is 10℃ / min), crush, pass through an 80-mesh sieve, granulate, and obtain spherical particles with a diameter of 5mm, i.e., the reaction catalyst. After testing, the specific surface area of ​​the reaction catalyst is 402m 2 / g, the pore volume is 0.52mL / g, and the average pore diameter is 5.23nm.

[0057] Synthesis of 2,2-difluoroethyl acetate:

[0058] 1. After the tubular reactor 9 is cleaned, the prepared reaction catalyst is loaded into the tubular reactor 93 to fill each tubular reactor 93;

[0059] 2. Hot heat transfer oil is introduced into the jacket 94 of the tubular reactor 9, and the heating rate of the heat transfer oil is controlled to be ≤10°C until the temperature of the reactor reaches 180°C. High-purity nitrogen is then replaced and vacuumized to make the water content in the reactor ≤10PPM and O2 ≤30PPM;

[0060] 3. Add 30 kg of sodium acetate and 75 kg of DMF into the mixing tank A2; add 58.8 kg of R142 into the R142 storage tank 1; start stirring the mixing tank A2 for 30 minutes;

[0061] 4. Start metering pump A4 and metering pump B5, and add the raw materials sodium acetate: R142: DMF into the static mixer 8 in a substance ratio of 1:1.6:2.8 according to mass flow meter A6 and mass flow meter B7, and the mixed liquid is evenly mixed in the static mixer 8;

[0062] 5. The mixed liquid from the static mixer 8 passes through the tubular reactor 9 at a liquid flow rate of 5.46 kg / min, and undergoes an esterification reaction under normal pressure to generate 2,2-difluoroethyl acetate and sodium chloride;

[0063] 6. The reaction lasts for about 10 minutes (the time is from the time when the mixed liquid flows into the reactor at a flow rate of 5.46 kg / min to the time when it finally flows out of the reactor). The mixed liquid after the reaction flows out from the lower end outlet of the tubular reactor 9 (start timing), and is collected in a clean container for 30 minutes, and then the collection is stopped.

[0064] Result analysis:

[0065] The mixed liquid collected after the reaction was weighed, and the weight was 163.8 kg. Since the collection time was 30 minutes, the amount of raw materials added before the reaction was: 30 × 5.46 = 163.8 kg, so the law of conservation of mass was observed before and after the reaction;

[0066] The mixed liquid collected above is first condensed through a condenser, and then the condensate is sealed and filtered to separate sodium chloride, which is weighed to be 20.286 kg after drying; the filtrate obtained after removing the sodium chloride is distilled, and the specific method is as follows: the filtrate is placed in a distillation tower, heated under normal pressure, and the fraction at 35-37° C. at the top of the distillation tower is collected to obtain 11.5422 kg of unreacted R142; the filtrate after the above distillation is distilled again, and the fraction at 98-105° C. at the top of the distillation tower is collected, that is, the product 2,2-difluoroethyl acetate is 45.63 kg; the remaining filtrate after the above distillation is heated to 155° C. (the temperature is higher than the boiling point of DMF) for condensation and evaporation, and the steam is collected to condense to obtain 84.936 kg of DMF and residual solids, and then the residual solids are analyzed to finally obtain 1.248 kg of sodium chloride, 0.1536 kg of sodium acetate, and 0.0042 kg of impurities in the solid.

[0067] Table 1 Changes in mass of each material before and after the reaction

[0068]

[0069]

[0070] The conversion rate of sodium acetate calculated from Table 1 is: (30-0.1536) / 30=99.49%; Agilent chromatograph analysis shows that the purity of the recovered R142 after the reaction is 99.95%; the purity of 2,2-difluoroethyl acetate after drying with 3A molecular sieve is 99.99%, and the moisture content is ≤10PPM; the selectivity of 2,2-difluoroethyl acetate is 99.99% (the actual weight of 2,2-difluoroethyl acetate obtained / theoretical weight of 2,2-difluoroethyl acetate should be obtained=45.63 / (45.63+0.0042)=99.99%). R142 and sodium acetate have a high sodium acetate conversion rate and 2,2-difluoroethyl acetate selectivity under the action of a reaction catalyst when the mass content ratio is appropriate.

[0071] In order to verify whether the reaction of the recovered sodium acetate, sodium chloride, R142, and DMF again would affect the purity of the product 2,2-difluoroethyl acetate and the conversion rate of sodium acetate, the above unreacted R142 and the mixed solution (containing the solvent DMF, unreacted sodium acetate and a trace amount of byproduct sodium chloride) were recovered, and the molar ratio of DMF: sodium acetate: R142 was prepared as 1:1.6:2.8, and then reacted again. The final conversion rate of sodium acetate was still as high as 99.42%; Agilent chromatograph analysis showed that the purity of the product 2,2-difluoroethyl acetate obtained by the reaction was ≥99.99%, and the water content of 2,2-difluoroethyl acetate was ≤10PPM using Karl Fischer titrator. The experimental results show that the recovered DMF, the solution containing a small amount of sodium acetate and a small amount of byproduct NaCl, re-participated in the reaction, and the byproduct NaCl and a small amount of sodium acetate did not affect the second reaction, and the conversion rate of sodium acetate and the purity of 2,2-difluoroethyl acetate were still very high.

[0072] Embodiments 2 to 9

[0073] Compared with Example 1, the difference is that in the preparation process of the reaction catalyst, the metals and their mass ratios in the catalysts used in each embodiment, as well as the final purity of sodium acetate and 2,2-difluoroethyl acetate are shown in Table 2, and the specific surface area, pore volume, and average pore diameter of the reaction catalysts prepared in Examples 2-9 are basically the same as those of the reaction catalyst prepared in Example 1.

[0074] Table 2 Metal mass ratio in reaction catalyst and related reaction results

[0075]

[0076]

[0077] In Examples 2 and 3, based on Example 1, the Cr metal content in the main catalyst remains unchanged, and the mass content of metal atoms (Al, Co, Mg, Zn and In) of each component of the co-catalyst increases or decreases by 5%. As can be seen from Table 2, further increasing or reducing the content of metal atoms in the co-catalyst within a certain range has no significant effect on the improvement of sodium acetate conversion rate and 2,2-difluoroethyl acetate purity.

[0078] Examples 4 to 8 all reduce one co-catalyst component on the basis of Example 1. As can be seen from Table 2, the metal indium in the co-catalyst can improve the purity of the product 2,2-difluoroethyl acetate; and other metals in the co-catalyst, such as aluminum, cobalt, magnesium, and zinc, can improve the conversion rate of sodium acetate.

[0079] Example 9 is a reaction catalyst containing only chromium oxide as the main catalyst, and also has a good sodium acetate conversion rate and a high purity of 2,2-difluoroethyl acetate.

[0080] From the data difference in Table 2, it can be seen that adding a specific type of auxiliary catalyst component on the basis of the main catalyst has a synergistic effect, which can further improve the conversion rate of sodium acetate and the purity of 2,2-difluoroethyl acetate.

[0081] Example 10

[0082] This embodiment is to use Figure 1 Medium and large-scale continuous uninterrupted reaction equipment is used to prepare 2,2-difluoroethyl acetate. The specific process is as follows:

[0083] S1. After the shell-and-tube reactor 9 is cleaned, the reaction catalyst prepared above is loaded into the shell-and-tube 93 to fill each reactor shell-and-tube;

[0084] S2. Pass heat transfer oil to the jacket 94 of the shell-and-tube reactor, control the heating rate of the heat transfer oil to ≤10°C, until the temperature in the shell-and-tube reactor is 180°C, replace with high-purity nitrogen, evacuate, so that the water content in the reactor is ≤10PPM; O2≤30PPM;

[0085] S3. DMF and sodium acetate (sodium acetate: DMF = 1:2.8) were added to the mixing tank A2 according to the ratio, and stirring was started and mixed for 30 minutes; at the same time, liquid R142 was added to the R142 storage tank 1;

[0086] S4. Start metering pump A4 and metering pump B 5, add raw material sodium acetate: R142: DMF in a molar ratio of 1:1.6:2.8 to the static mixer 8 according to mass flow meter A6 and mass flow meter B 7, and mix the mixed liquid evenly in the static mixer 8;

[0087] S5. The mixed liquid from the static mixer 8 enters the tubular reactor 9 at a liquid flow rate of 5.46kg / min, and the esterification reaction is carried out at normal pressure;

[0088] S6. After the reaction, the material flows out from the lower part of the tubular reactor, and enters the filtering, drying and conveying integrated machine 11 after condensation by the tubular condenser 10. In the device, the sodium chloride generated after the reaction is separated from the solution (trace sodium acetate, R142, 2,2-difluoroethyl acetate, DMF), and the separated sodium chloride is vacuum dried in the filtering, drying and conveying integrated machine 11. After drying, the sodium chloride is discharged through the spiral in the device;

[0089] S7. The solution from the filtering, drying and conveying integrated machine 11 enters the filtrate collection tank 12 and is conveyed to the distillation tower A14 (reaction conditions: the distillation tower A is heated to 35-37° C. at normal pressure) by the centrifugal pump 13. The unreacted R142 obtained by distillation is collected from the top of the tower and returned to the R142 storage tank 1 to continue the reaction by taking advantage of the relatively low boiling point of R142.

[0090] S8. The solution from the distillation tower A14 enters the distillation tower B15 (reaction conditions: the distillation tower B is heated to 155° C. at normal pressure). The distilled 2,2-difluoroethyl acetate is collected from the top of the tower by using the relatively low boiling point of 2,2-difluoroethyl acetate. After drying in the molecular sieve drying tower 16, the 2,2-difluoroethyl acetate is collected in the product storage tank 17.

[0091] S9. The mixed solution (a small amount of sodium chloride, DMF, and a trace amount of sodium acetate) coming out from the lower end of the distillation tower B15 is returned to the mixing tank A2 and / or the mixing tank B3 to continue to participate in the reaction.

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is that, during the synthesis process, after the tubular reactor of step 1 is cleaned, no substance is added into the tubular reactor, that is, no reaction catalyst is added, and the remaining experimental operations and steps are consistent with Example 1.

[0094] Result analysis: The purity of 2,2-difluoroethyl acetate was 95.1% when analyzed by Agilent chromatograph; the water content of 2,2-difluoroethyl acetate was ≤10PPM when analyzed by Karl Fischer titrator. The conversion rate of sodium acetate was 12.2%.

[0095] From the reaction results, it can be seen that if the metal oxide reaction catalyst of the present invention is not added and the sodium acetate conversion rate is extremely low, the reaction raw materials cannot be completely reacted, the production efficiency is low, the unit consumption of the product is very large, and the purity of the product is significantly reduced compared with Example 1.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that the preparation method of the reaction catalyst is different. The reaction catalyst in this comparative example is directly purchased from the market, and chromium oxide, aluminum oxide, cobalt oxide, magnesium oxide, zinc oxide, and indium oxide are crushed, passed through an 80-mesh sieve, and then mixed in a mass ratio of Cr:Al:Co:Mg:Zn:In of 21.7:0.74:1.84:1.11:1.44:1.05, and granulated to obtain the reaction catalyst.

[0098] Result analysis: The purity of 2,2-difluoroethyl acetate was 74.2% when analyzed by Agilent chromatograph; the moisture content of 2,2-difluoroethyl acetate was ≤10PPM when analyzed by Karl Fischer titrator, and the conversion rate of sodium acetate was 45.4%.

[0099] From the reaction results, it can be seen that the metal atoms in the reaction catalyst prepared by directly purchasing metal oxides and mixing them in proportion cannot be evenly distributed in the catalyst, and a uniform metal atom network structure cannot be formed, resulting in different active metal contents in each φ5 catalyst, and the synergistic catalytic effect of each active metal element cannot be exerted. In addition, the reaction catalyst prepared in Example 2 has a specific surface area of ​​92m 2 / g, the pore volume is 0.2mL / g, and the average pore size is only 2.3nm. The catalyst has a very small pore size, a very small specific surface area, and a very small average pore size, which does not create a sufficient contact reaction opportunity between the reaction raw materials, ultimately resulting in poor catalyst performance, extremely low sodium acetate conversion rate, inability to completely react the reaction raw materials, low production efficiency, and significantly reduced product purity compared with Example 1.

[0100] Comparative Example 3

[0101] 2.5 kg DMF, 1 kg sodium acetate, 1.96 kg liquid R142 and 3 kg potassium iodide were added to the reactor, and the reaction was carried out at 0.3 MPa and 180° C. for 3 h. After the reaction was completed, the reaction liquid was collected and separated by condensation through a condenser, and distilled to finally obtain the reaction product 2,2-difluoroethyl acetate.

[0102] The purity of 2,2-difluoroethyl acetate was 96.1% by Agilent chromatograph analysis; the water content of 2,2-difluoroethyl acetate was ≤10PPM by Karl Fischer titrator analysis. The conversion rate of sodium acetate was 75.6%.

[0103] The difference between this comparative example and Example 1 is that the reaction catalyst added during the reaction of this comparative example is potassium iodide, while the catalyst in this comparative example is dissolved in a solvent, and only intermittent reaction can be carried out, and the reaction time is long. The conversion rate of sodium acetate in this comparative example is low, resulting in low yield of 2,2-difluoroethyl acetate, low purity of 2,2-difluoroethyl acetate, and high energy consumption per unit product.

[0104] Comparative Example 4

[0105] 2.5 kg DMF, 1 kg sodium acetate, 1.96 kg liquid R142, 9 kg potassium iodide and 1.5 kg benzyltriethylammonium chloride (TEBA) were added to the reactor, and the mixture was reacted at 0.3 MPa and 180° C. for 3 h. After the reaction, the reaction liquid was collected and separated by condensation through a condenser, and then distilled to finally obtain the reaction product 2,2-difluoroethyl acetate.

[0106] The purity of 2,2-difluoroethyl acetate was 97.4% when analyzed by Agilent chromatograph, and the water content of 2,2-difluoroethyl acetate was ≤10PPM when analyzed by Karl Fischer titrator. The conversion rate of sodium acetate was 82.5%.

[0107] The difference between this comparative example and Example 1 is that the reaction catalysts added during the reaction of this comparative example are potassium iodide and TEBA, while the reaction catalyst in this comparative example is dissolved in a solvent, and only intermittent reactions can be carried out, and the reaction time is long. This comparative example adds a phase conversion catalyst, and although the conversion rate of sodium acetate and the purity of 2,2-difluoroethyl acetate are slightly improved compared with Comparative Example 3, there is a significant difference compared with the example (the purity of the prepared 2,2-difluoroethyl acetate is 99.99%, and the conversion rate of sodium acetate is 99.49%).

[0108] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for synthesizing 2,2-difluoroethyl acetate, characterized in that: Under the catalysis of a reaction catalyst, 2-chloro-1,1-difluoroethane, an alkali metal acetate and a solvent are continuously reacted at 140-200° C., and then post-treated to obtain 2,2-difluoroethyl acetate; The preparation method of the reaction catalyst is as follows: chromium salt, or chromium salt and other metal salts contained in the system are mixed, an alkaline solution is added for co-precipitation, and the pH is controlled to be 9-10, and the precipitate is washed, dried, and calcined in an inert gas atmosphere at 300-400°C; The other metal salts are one or more of aluminum salts, cobalt salts, magnesium salts, zinc salts, and indium salts.

2. The synthesis method according to claim 1, characterized in that: The other metal salts are aluminum salts, cobalt salts, magnesium salts, zinc salts and indium salts.

3. The synthesis method according to claim 2, characterized in that: The mass ratio of chromium atoms, aluminum atoms, cobalt atoms, magnesium atoms, zinc atoms and indium atoms in the reaction catalyst is 21.7: 0.67-0.74: 1.66-1.84: 1.00-1.11: 1.37-1.51: 0.95-1.

05.

4. The synthesis method according to claim 1, characterized in that: The specific surface area of ​​the reaction catalyst is ≥400m 2 / g, pore volume ≥0.5mL / g, average pore diameter ≥5.2nm.

5. The synthesis method according to claim 1, characterized in that: The alkali metal acetate is sodium acetate or potassium acetate.

6. The synthesis method according to claim 1, characterized in that: The molar ratio of the alkali metal acetate to 2-chloro-1,1-difluoroethane is 1:(1.5-2.5).

7. The synthesis method according to claim 1, characterized in that: The molar ratio of the alkali metal acetate to the solvent is 1:(2-3).

8. The synthesis method according to claim 1, characterized in that: The solvent is one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dibutylformamide.

9. The synthesis method according to claim 1, characterized in that: The post-treatment includes condensation, filtration, collection of filtrate, distillation and product drying.

10. Use of a reaction catalyst in improving the conversion rate of alkali metal acetate and / or the selectivity of 2,2-difluoroethyl acetate, characterized in that: The preparation method of the reaction catalyst is as follows: chromium salt, or chromium salt and other metal salts contained in the system are mixed, an alkaline solution is added to a pH of 9 to 10, a precipitation reaction is performed, the precipitate is washed, dried, and calcined in an inert gas atmosphere at 300 to 400°C; The other metal salts are one or more of aluminum salts, cobalt salts, magnesium salts, zinc salts, and indium salts.

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