Process for the one-step synthesis of hexafluorobutadiene

Abstract

The application relates to a one-step method for synthesizing hexafluorobutadiene, which comprises the following steps: adding newly pressed sodium filaments, anhydrous and oxygen-free treated toluene into a reactor respectively, heating to 80-120 DEG C, stirring until the sodium filaments are completely converted into sodium sand, passing in ammonia, activating the sodium sand for 1 h, passing in trifluorochloroethylene into the reaction liquid at a flow rate of 20-60 mL / min, and the mass ratio of sodium and trifluorochloroethylene is 1:1.2-2; after the aeration is completed, the temperature is kept, constant-temperature reaction is carried out for 1-4 h, the gas generated in the reaction is collected to obtain hexafluorobutadiene, and the remaining liquid is subjected to subsequent recovery treatment. The method of sodium dechlorination coupling can realize the preparation of hexafluorobutadiene from cheap and easily obtained trifluorochloroethylene in one step, and the preparation process route of the product is shortened.

Description

Technical Field

[0001] This invention relates to a method for synthesizing hexafluorobutadiene, belonging to the field of chemical technology. Background Technology

[0002] Hexafluoro-1,3-butadiene (hereinafter referred to as hexafluorobutadiene) has replaced CF4 in the dry etching process of KF laser-etched single-cell capacitor patterns. It offers significant etching advantages at the 0.13μm technical level, exhibiting excellent etching selectivity. It can rapidly form a low-density, thin-thickness fluorocarbon polymer protective film on the material surface while achieving moderate etching intensity, resulting in superior anisotropic etching effects and enabling near-vertical deep trench structure processing. This makes it the best-performing etching gas for electronic circuits currently available. Furthermore, its GWP value is only 290, its atmospheric lifetime is less than 2 days, its degradation rate is rapid, and its molecules do not contain chlorine. In summary, hexafluorobutadiene is currently almost the only electronic specialty gas that can simultaneously meet the requirements of high etching precision and high selectivity while posing relatively low risks to the ozone layer and the greenhouse effect.

[0003] Currently, the synthesis of hexafluorobutadiene involves diverse raw materials, numerous processes, complex steps, and stringent conditions. A summary analysis reveals three main approaches: 1. Organometallic reagent coupling method: Using trifluorovinyl metal halides as raw materials, hexafluorobutadiene is generated through a coupling reaction under iron and copper salt conditions. This process has a relatively short synthetic route and high reaction selectivity, but the reactive reagents are highly hazardous, and the high cost of some raw materials, such as dibromotetrafluoroethane, limits its large-scale industrial application. 2. Saturated haloalkanes dehalogenation method: Hexafluorobutadiene is prepared by dehalogenating saturated butane halides under zinc powder conditions. This step has a high conversion rate and relatively pure product, but the synthesis of saturated butane halides involves multiple steps. Although this method is currently the most officially used in industry, its stringent conditions, numerous impurities, and waste issues keep the cost of this process high. 3. Grignard reagent defluorination method: Hexafluorobutadiene is prepared by defluorination of 1,4-dihaloperfluorobutane as a raw material under Grignard reagent conditions. This step has mild process conditions and is relatively safe. However, a certain amount of hexafluorocyclobutene byproduct is generated during the process. The boiling point of this byproduct is only 0.8 ppm different from that of hexafluorobutadiene. ℃ It is difficult to separate them effectively using ordinary distillation methods.

[0004] In summary, the synthesis of hexafluorobutadiene is currently limited in industrial production due to factors such as expensive and reactive raw materials, long reaction steps, harsh reaction conditions, numerous impurities, and serious waste problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a production process route for the one-step efficient synthesis of hexafluorobutadiene from trifluorochloroethylene as raw material. The design of this production process route shortens the synthesis steps of the target product, simplifies the production process, saves equipment investment, and helps to improve productivity.

[0006] To achieve the purpose of this invention, the technical solution adopted is as follows:

[0007] A one-step method for synthesizing hexafluorobutadiene includes the following steps: adding freshly pressed sodium wire and anhydrous and oxygen-free toluene to a reactor, heating to 80–120°C, stirring until the sodium wire is completely converted into sodium sand, introducing ammonia gas to activate the sodium sand for 1 hour, introducing trifluorochloroethylene into the reaction solution at a flow rate of 20–60 mL / min, with a molar ratio of sodium to trifluorochloroethylene of 1:1.2–2; after the gas introduction is completed, maintaining the temperature, reacting at a constant temperature for 1–4 hours, collecting the gas produced in the reaction to obtain hexafluorobutadiene, and performing subsequent recovery treatment on the remaining liquid.

[0008] Preferably, the reactor is equipped with a condenser reflux and a platinum resistance thermometer. Before adding freshly pressed sodium wire and anhydrous and oxygen-free toluene, the reactor is subjected to vacuum-nitrogen purging to remove moisture and oxygen from the reactor.

[0009] Preferably, the mass ratio of newly pressed sodium wire to anhydrous and oxygen-free toluene is 1:10-20, and the mass of ammonia gas introduced is 1-5% of the mass of sodium wire.

[0010] Preferably, the method for treating toluene with anhydrous and oxygen-free fluid includes the following steps:

[0011] Add a desiccant to analytical grade toluene or recycled toluene, stir at room temperature for 1 hour, then distill, collecting the fraction at 108-112℃ to achieve pre-drying of toluene; add sodium wire and benzophenone to the pre-dried toluene, wherein the mass ratio of sodium wire, benzophenone and pre-dried toluene is 1:4:10-20, reflux at 115℃ until the solution turns deep blue, then distill off the toluene, and transfer the distillate to a bottle containing 3A molecular sieve activated at 500℃, seal and store, wherein the volume ratio of distillate to molecular sieve is 20:1.

[0012] Preferably, the desiccant includes one or more of phosphorus pentoxide, calcium oxide, etc., and the amount of desiccant added is such that after stirring evenly, there is a powdery solid residue remaining.

[0013] Preferably, the method for subsequent recovery and treatment of the remaining liquid includes the following steps: after the reaction has cooled to room temperature, anhydrous ethanol is added dropwise to the reaction apparatus until excess, stirred for 1 hour, the unreacted sodium wire is removed, and the toluene solvent is recovered.

[0014] Preferably, the method for recovering toluene solvent is as follows: water is added to the reaction system after quenching with ethanol until the precipitate is completely dissolved, and then the liquid is separated; the upper organic phase solution is dried with magnesium sulfate and distilled to obtain recovered toluene, with a toluene recovery rate of greater than 85%. Preferably, the amount of magnesium sulfate used is such that after stirring evenly, there is a powdery solid residue remaining.

[0015] Preferably, the gas produced by the reaction is collected to obtain hexafluorobutadiene, which is then purified by distillation.

[0016] Advantages of this invention:

[0017] 1) By using sodium dechlorination coupling, the preparation of trifluorochloroethylene, a cheap and readily available raw material, into hexafluorobutadiene can be achieved in one step, shortening the product preparation process route.

[0018] 2) This method helps to reduce the generation of waste in the reaction system by recycling toluene, thereby reducing production costs and environmental pressure.

[0019] The process of this invention is simple, the reaction conditions are controllable, the product yield is high, and the waste output is small. It has a good effect on reducing the cost of hexafluorobutadiene production and the environmental pressure. Detailed Implementation

[0020] The following examples are only used to further explain the present invention and do not limit the scope of protection of the present invention.

[0021] Example 1:

[0022] (1) Preparation of anhydrous and oxygen-free toluene

[0023] Take analytical grade toluene solvent, add an appropriate amount of desiccant, stir at room temperature for 1 hour, then distill, collecting the fraction at approximately 110℃ to achieve pre-drying of toluene. Add sodium wire and benzophenone (mass ratio approximately 1:4) to the pre-dried toluene, reflux until the solution turns deep blue, then distill off the toluene, and transfer the distillate to a reagent bottle containing 3A molecular sieve activated at 500℃, then seal and store.

[0024] (2) Synthesis of hexafluorobutadiene

[0025] A 1L three-necked flask was connected to a reflux condenser, a platinum resistance thermometer, and a venting line. The apparatus was evacuated and purged with nitrogen three times to remove moisture and oxygen. 13.8g of freshly pressed sodium wire and 300mL of anhydrous and oxygen-free toluene were added. The mixture was heated to 80℃ and stirred for 2 hours until the sodium wire was completely converted into sodium sand. 0.69g of 5% ammonia gas was introduced to activate the sodium sand. Trifluorochloroethylene was then introduced into the reaction solution at a flow rate of 20mL / min, with a total gas mass of 139.2g. The molar ratio of sodium to trifluorochloroethylene was 1:2. After the gas introduction was complete, the reaction was maintained at 80℃ for 1 hour. 37.1g of the gas produced was collected. The purity of hexafluorobutadiene was 95.3%, and the yield was 72.7%. After distillation using a common distillation method, the product purity can reach 99.91%. After the reaction is cooled to room temperature, ethanol is added dropwise to the reaction apparatus until excess, and the mixture is stirred for 1 hour. Unreacted sodium wire is removed, and toluene solvent is recovered.

[0026] (3) Recovery of toluene solvent

[0027] Water was added to the reaction system after quenching with ethanol until the precipitate was completely dissolved, and the mixture was separated. The upper organic phase solution was dried over magnesium sulfate, filtered, and then recovered.

[0028] Example 2:

[0029] (1) Preparation of anhydrous and oxygen-free toluene

[0030] Take analytical grade toluene solvent, add an appropriate amount of desiccant, stir at room temperature for 1 hour, then distill, collecting the fraction at approximately 110℃ to achieve pre-drying of toluene. Add sodium wire and benzophenone (mass ratio approximately 1:4) to the pre-dried toluene, reflux until the solution turns deep blue, then distill off the toluene, and transfer the distillate to a reagent bottle containing 3A molecular sieve activated at 500℃, then seal and store.

[0031] (2) Synthesis of hexafluorobutadiene

[0032] A 10L reactor connected to a reflux condenser, a platinum resistance thermometer, and a venting line was used. The reactor was evacuated and purged with nitrogen three times to remove moisture and oxygen. 138.0g of freshly pressed sodium wire and 3L of anhydrous and oxygen-free toluene were added. The mixture was heated to 120℃ and stirred for 0.5h until the sodium wire was completely converted into sodium sand. 1.38g of ammonia (1%) was introduced to activate the sodium sand. Trichlorofluoroethylene was then introduced into the reaction mixture at a flow rate of 60mL / min, with a total gas flow of 835.2g. The molar ratio of sodium to trichlorofluoroethylene was 1:1.2. After the gas flow was complete, the reaction was maintained at 120℃ for 2h. 413.3g of the gas produced was collected. The purity of hexafluorobutadiene was 94.1%, and the yield was 80.0%. After distillation using standard methods, the product purity reached 99.90%.

[0033] After the reaction has cooled to room temperature, ethanol is added dropwise to the reaction apparatus until excess, and the mixture is stirred for 1 hour. The unreacted sodium wire is then removed and the toluene solvent is recovered.

[0034] (3) Recovery of toluene solvent

[0035] Water was added to the reaction system after quenching with ethanol until the precipitate was completely dissolved, and the mixture was separated. The upper organic phase solution was dried over magnesium sulfate, filtered, and then recovered.

[0036] Example 3:

[0037] (1) Preparation of anhydrous and oxygen-free toluene

[0038] Take analytical grade toluene solvent, add an appropriate amount of desiccant, stir at room temperature for 1 hour, then distill, collecting the fraction at approximately 110℃ to achieve pre-drying of toluene. Add sodium wire and benzophenone (mass ratio approximately 1:4) to the pre-dried toluene, reflux until the solution turns deep blue, then distill off the toluene, and transfer the distillate to a reagent bottle containing 3A molecular sieve activated at 500℃, then seal and store.

[0039] (2) Synthesis of hexafluorobutadiene

[0040] A 5L reactor connected to a reflux condenser, a platinum resistance thermometer, and a venting line was used. The reactor was evacuated and purged with nitrogen three times to remove moisture and oxygen. 92.0g of freshly pressed sodium wire and 2L of anhydrous and oxygen-free toluene were added. The mixture was heated to 100℃ and stirred for 1 hour until the sodium wire was completely converted into sodium sand. 2.76g of ammonia (3%) was introduced to activate the sodium sand. Trifluorochloroethylene was then introduced into the reaction mixture at a flow rate of 40mL / min, with a total gas flow of 696.0g. The molar ratio of sodium to trifluorochloroethylene was 1:1.5. After the gas flow was complete, the reaction was maintained at 100℃ for 4 hours. 298.5g of the gas produced was collected. The purity of hexafluorobutadiene was 96.2%, and the yield was 88.6%. After distillation using a common distillation method, the product purity can reach 99.92%. After the reaction is cooled to room temperature, ethanol is added dropwise to the reaction apparatus until excess, and the mixture is stirred for 1 hour. Unreacted sodium wire is removed, and toluene solvent is recovered.

[0041] (3) Recovery of toluene solvent

[0042] Water was added to the reaction system after quenching with ethanol until the precipitate was completely dissolved, and the mixture was separated. The upper organic phase solution was dried over magnesium sulfate, filtered, and then recovered.

[0043] The above are merely specific implementation examples of the present invention. However, the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the technical protection scope of the present invention.

Claims

1. A one-step method for synthesizing hexafluorobutadiene, characterized in that, The process includes the following steps: adding freshly pressed sodium wire and anhydrous and oxygen-free toluene to the reactor, heating to 80-120°C, stirring until the sodium wire is completely converted into sodium sand, introducing ammonia gas to activate the sodium sand for 1 hour, and introducing trifluorochloroethylene into the reaction solution at a flow rate of 20-60 mL / min, with a molar ratio of sodium to trifluorochloroethylene of 1:1.2-2; after the gas introduction is completed, maintaining the temperature and reacting at a constant temperature for 1-4 hours, collecting the gas produced in the reaction to obtain hexafluorobutadiene, and the remaining liquid undergoing subsequent recovery treatment; the mass ratio of freshly pressed sodium wire to anhydrous and oxygen-free toluene is 1:10-20, and the mass of ammonia gas introduced is 1-5% of the mass of sodium wire.

2. The method for one-step synthesis of hexafluorobutadiene according to claim 1, characterized in that, The reactor is equipped with a condenser reflux and a platinum resistance thermometer. Before adding freshly pressed sodium wire and anhydrous and oxygen-free toluene, the reactor is subjected to vacuum-nitrogen purging to remove moisture and oxygen from the reactor.

3. The method for one-step synthesis of hexafluorobutadiene according to claim 1, characterized in that, The method for treating toluene in anhydrous and oxygen-free conditions includes the following steps: Add a desiccant to analytical grade toluene or recycled toluene, stir at room temperature for 1 h, then distill, collecting the fraction at 108-112℃ to achieve pre-drying of toluene; add sodium wire and benzophenone to the pre-dried toluene, wherein the mass ratio of sodium wire, benzophenone and pre-dried toluene is 1:4:10~20, reflux at 115℃ until the solution turns deep blue, then distill off the toluene, and transfer the distillate to a bottle containing 3A molecular sieve activated at 500℃, seal and store, wherein the volume ratio of distillate to molecular sieve is 20:

1.

4. The method for one-step synthesis of hexafluorobutadiene according to claim 3, characterized in that, The desiccant includes one or more of phosphorus pentoxide and calcium oxide, and the amount of desiccant added is based on the amount of powdery solid remaining after stirring evenly.

5. The method for one-step synthesis of hexafluorobutadiene according to claim 1, characterized in that, The method for subsequent recovery and treatment of the remaining liquid includes the following steps: after the reaction has cooled to room temperature, anhydrous ethanol is added dropwise to the reaction apparatus until excess, and the mixture is stirred for 1 hour to remove the unreacted sodium wire and recover the toluene solvent.

6. The method for one-step synthesis of hexafluorobutadiene according to claim 5, characterized in that, The method for recovering toluene solvent is as follows: water is added to the reaction system after quenching with ethanol until the precipitate is completely dissolved, and then the liquid is separated; the upper organic phase solution is dried with magnesium sulfate and distilled to obtain recovered toluene, with a toluene recovery rate of more than 85%.

7. The method for one-step synthesis of hexafluorobutadiene according to claim 6, characterized in that, The amount of magnesium sulfate used should be such that after adding and stirring evenly, there is a powdery solid residue remaining.

8. The method for one-step synthesis of hexafluorobutadiene according to claim 1, characterized in that, The gas produced by the reaction is collected to obtain hexafluorobutadiene, which is then purified by distillation.