Process for the preparation of (z) / (e)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane

Abstract

The application belongs to the technical field of fluorine-containing organic chemical preparation, and particularly relates to a method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane. The method comprises the following steps: firstly, adding magnesium into a closed reaction container filled with a solvent; then, adding an initiator, replacing the air in the closed reaction container with nitrogen, and introducing 1,1,1-trifluoro-2-chloroethane for reaction; then, adding sulfuryl chloride dropwise into the obtained reaction solution for reaction at room temperature; after the reaction is completed, introducing chlorine-nitrogen mixed gas into the reaction solution cooled to 0-5 DEG C for photochlorination reaction; then, adding an inorganic alkali solution or an organic alkali for mixed reaction and heating reaction; finally, performing rectification purification on the reaction mixture to obtain (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene. The method is characterized by low cost, mild reaction conditions, no need of strong corrosive substances and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of fluorine-containing organic chemicals, specifically relating to a method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane. Background Technology

[0002] 1,1,1,4,4,4-Hexafluoro-2-butene (HFO-1336mzz, CAS No. 66711-86-2) is a promising environmentally friendly fluorinated olefin, classified into Z-HFO-1336mzz (cis) and E-HFO-1336mzz (trans) based on their spatial structures. HFO-1336mzz is considered an ideal green alternative to traditional blowing agents, refrigerants, and etching gases. Furthermore, this compound can serve as a pharmaceutical and pesticide intermediate, as well as a monomer for the synthesis of high-performance fluoropolymers. However, existing preparation methods generally suffer from bottlenecks such as high raw material costs, demanding reaction conditions, and difficulties in waste treatment, hindering its large-scale industrial production.

[0003] Currently, several technical routes have been developed for the synthesis of HFO-1336mzz. The catalytic hydrogenation route using hexafluoro-2-butyne as a raw material is one of the most direct methods. This route involves hydrogenation reduction in a noble metal catalyst such as Pt and an ethanol solvent at 25–75 °C and 1.3–6.8 atm, followed by distillation to obtain the product. Although the product selectivity is high, the synthesis cost of hexafluoro-2-butyne is high, and over-hydrogenation or catalyst deactivation due to carbon deposition is prone to occur during hydrogenation. Furthermore, the Z / E configuration ratio in the product requires an additional isomerization step for control, resulting in a relatively complex overall process.

[0004] A two-step catalytic conversion process using 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) as feedstock involves first dehydrohalogenating HCFC-123 in DMF solvent using a CuCl2 / bipyridine complex catalyst at room temperature to generate the intermediate CF3CCl=CHF. Then, catalytic reforming and dechlorination are performed at 200°C using a Pd / Al2O3 catalyst. Both steps demonstrate excellent overall yield and Z-configuration selectivity. However, the process uses toxic DMF solvent, increasing waste treatment costs, and the second-step reaction temperature of 200°C results in high system energy consumption.

[0005] The radical addition route using carbon tetrachloride and three-carbon haloolefins as raw materials utilizes the radical addition mechanism, sequentially involving anti-Markovnikov addition of CCl4 to the double bond, chlorination with chlorine, and subsequent catalytic dechlorination and hydrogenation. This multi-step reaction constructs the target molecule at extremely low cost. However, this route is lengthy, and the overall yield is limited by the cumulative losses from multiple reactions, especially the chlorination stage, which easily generates complex polychlorinated byproducts, making subsequent separation and purification extremely difficult. The telomerization conversion process using carbon tetrachloride and ethylene as raw materials utilizes the telomerization reaction of CCl4 with ethylene to generate a C6 intermediate, which is then chlorinated and fluorinated to obtain the final product, resulting in low procurement costs. However, this process generates a large amount of hydrogen chloride tail gas during chlorination, placing stringent requirements on equipment corrosion prevention and tail gas treatment systems. Furthermore, the HF fluorination reaction is a strongly exothermic process, making heat and mass transfer control difficult, and residual chlorine in the product is difficult to completely remove.

[0006] The coupling fluorination process using trifluoromethane and hexafluoropropylene as raw materials involves activating CHF3 at high temperature or plasma to generate difluorocarbene, which then undergoes cyclopropanation or insertion reaction with hexafluoropropylene. Following fluorination and ring-opening rearrangement, the target product is obtained, exhibiting high atom economy. However, the reaction conditions are extremely demanding, requiring high temperatures or strong oxidants, and placing extremely high demands on the corrosion resistance of the reactor material. Furthermore, controlling the amount of HF used in the fluorination step is difficult, easily leading to over-fluorination and the generation of perfluorinated byproducts. The regioselectivity and stereoselectivity of the target product still require further optimization.

[0007] In recent years, several new routes have been disclosed in existing technologies. For example, CN104529695A proposes using HCFO-1233zd and halomethanes (such as R22, R23, etc.) as raw materials to undergo a thermal addition reaction at 250~350℃ and 0.3~0.6MPa to generate the intermediate hydrochlorofluorobutane. The target product is then obtained through gas-phase thermal cracking, HF fluorination, or zinc powder dechlorination. However, the thermal addition temperature is high and the pressure is high. The post-processing involves HF or zinc powder, which will generate a large amount of fluorine- or chlorine-containing wastewater. Equipment corrosion is also a significant concern. CN106966856A uses hexachlorobutadiene and HF as raw materials, and involves a three-step continuous reaction of gas-phase fluorine-chlorine exchange, deHCl removal, and selective hydrogenation. This route uses industrial byproducts as raw materials, resulting in lower costs. However, all three steps require specialized catalysts, and the reaction temperatures are as high as 200-450℃. The highly corrosive HF places stringent requirements on equipment materials, and the hydrogenation step easily generates the over-hydrogenated byproduct hexafluorobutane, increasing the difficulty of separation. CN115160103A uses 1,4-diiodooctafluorobutane as raw material, which undergoes deiodination at 50-70℃ under the action of Grignard reagents to produce hexafluorobutadiene. However, the raw materials themselves are difficult to synthesize and expensive, making it difficult to meet the economic requirements of industrial production. CN119954595A uses tetrafluoroethylene and liquid bromine as raw materials, and achieves continuous production through three steps of bromination, telomerization and Grignard elimination. However, the telomerization reaction needs to be carried out at 180~350℃ and uses highly corrosive liquid bromine. Tetrafluoroethylene itself needs to be prepared by R22 cracking, resulting in high overall raw material costs and equipment investment. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the problems of high raw material cost, harsh reaction conditions, use of strong corrosive reagents or generation of a large amount of waste in the existing technology. The present invention provides a method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane. The raw materials are cheap and readily available, the reaction conditions are mild, no strong corrosive substances are required and the method is environmentally friendly.

[0009] The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) according to the present invention includes the following steps: First, magnesium metal is added to a closed reaction vessel containing solvent, an initiator is added, the air in the closed reaction vessel is replaced with nitrogen, 1,1,1-trifluoro-2-chloroethane is introduced, the temperature is raised to 40~60℃, the system pressure is controlled at 3~5 bar, after the reaction, sulfuryl chloride is added dropwise to the obtained reaction solution, the reaction is carried out at room temperature, after the reaction is completed, a chlorine-nitrogen mixture is introduced into the reaction solution after it has been cooled to 0~5℃, and then an inorganic base solution or an organic base mixture is added to control the temperature for the reaction. The reaction mixture is purified by distillation to obtain (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene.

[0010] The inorganic alkali solution is an aqueous solution of NaOH or KOH with a mass concentration of 20%~30%. The inorganic alkali solution is added and the reaction is carried out at 20~32℃. After the reaction is completed, the solution is distilled at 32~34℃, and the distillate is collected to obtain (Z)-1,1,1,4,4,4-hexafluoro-2-butene. The amount of inorganic alkali added is: the molar ratio of inorganic alkali to sulfuryl chloride is 2.1~2.3:1.

[0011] The organic base is potassium tert-butoxide (KOt-BU), sodium tert-butoxide (NaOt-BU), or DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The organic base is added and reacted at 0-5°C. After the reaction is complete, the mixture is distilled at 7-8°C, and the fraction is collected to obtain (E)-1,1,1,4,4,4-hexafluoro-2-butene. The molar ratio of the organic base to sulfuryl chloride is 1.6-1.8:1.

[0012] The solvent in the reaction vessel is tetrahydrofuran or 1,4-dioxane, and both solvents are ultra-dry solvents with a moisture content of less than 5 ppm.

[0013] The air in the sealed reaction vessel is replaced with nitrogen gas, which is high-purity nitrogen, and 1,1,1-trifluoro-2-chloroethane (R133a) with a purity ≥99% is used as a raw material for the preparation of trifluoroacetic acid.

[0014] The initiator is iodine or 1,2-dibromoethane.

[0015] The molar ratio of metallic magnesium to sulfuryl chloride is 2.2~2.6:1. The metallic magnesium is in the form of magnesium shavings.

[0016] The molar ratio of 1,1,1-trifluoro-2-chloroethane to thioyl chloride is 2.2~2.6:1.

[0017] The bubbling rate of 1,1,1-trifluoro-2-chloroethane is 195 g / h to 230 g / h.

[0018] The molar ratio of initiator to thioyl chloride is 1:20~50.

[0019] The mass percentage of chlorine in the introduced chlorine-nitrogen mixture is 40% to 60%. The photochlorination reaction controls the gas flow rate of the chlorine-nitrogen mixture to be 110 g / h to 150 g / h. The light source is a 365 nm to 405 nm ultraviolet LED lamp, and the molar ratio of chlorine to thiocyanate chloride is 1.4 to 1.8:1.

[0020] Control the system pressure at 3-5 bar and react for 6-8 hours; after the reaction, add sulfuryl chloride dropwise to the resulting reaction solution and react at room temperature for 1-2 hours; after cooling to 0-5℃, introduce a chlorine-nitrogen mixture into the reaction solution and react for 20-45 minutes; after adding an alkaline solution or organic base, stir at controlled temperature for 2-3 hours to mix and react.

[0021] The specific reaction process steps of this invention are as follows: .

[0022] Specifically, the method for preparing (Z)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: This method uses an inorganic base (NaOH / KOH) to regulate the final product, thus yielding the cis product.

[0023] Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, ultra-dry tetrahydrofuran or 1,4-dioxane (moisture <5ppm) was added to a dry, sealed reactor, followed by magnesium shavings with a metallic luster, and iodine granules or 1,2-dibromoethane as an initiator. The air inside the reactor was purged three times with high-purity nitrogen, and then R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 40-60℃, and R133a was continuously introduced while maintaining the system pressure at 3-5 bar. The reaction was stirred for 6-8 hours. After the reaction was completed, the gas supply was stopped, and the unreacted R133a was recovered. The resulting Grignard reagent solution was stored under nitrogen protection for later use.

[0024] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 0-5°C, and sulfuryl chloride was slowly added dropwise (controlling the molar ratio of magnesium to sulfuryl chloride to approximately 2.2-2.6:1). After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1-2 hours. Subsequently, the reaction system was placed in an ice bath to cool to 0-5°C, and a 40%-60% Cl2 / N2 mixed gas was introduced at a rate of 110-150 g / h. A 365-405 nm ultraviolet LED lamp was used as the light source, and the molar ratio of chlorine to sulfuryl chloride was 1.4-1.8:1. Then, a 20%-30% (w / w) NaOH or KOH aqueous solution was slowly added to the reaction solution, and the temperature was controlled at 20-32°C for 2-3 hours. After the reaction was completed, the mixture was distilled at 32-34°C, and the distillate was collected to obtain (Z)-1,1,1,4,4,4-hexafluoro-2-butene.

[0025] Specifically, the method for preparing (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: The trans product was finally obtained by using an organic base (potassium tert-butoxide) to regulate the reaction. Step 1 was exactly the same, the difference being the base added in step 2 and the subsequent treatment.

[0026] Step 1: Preparation of Grignard reagent (same as Step 1 above, completely identical).

[0027] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 0-5°C, and thioyl chloride was slowly added dropwise (controlling the molar ratio of magnesium to thioyl chloride to approximately 2.2-2.6:1). After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1-2 hours. Subsequently, the reaction system was placed in an ice bath to cool to 0-5°C, and a 40%-60% Cl2 / N2 mixed gas was introduced at a rate of 110-150 g / h. A 365-405 nm ultraviolet LED lamp was used as the light source, and the molar ratio of chlorine to thioyl chloride was 1.4-1.8:1. Then, NaOt-BU, KOt-BU, or DBU was added to the reaction solution, and the mixture was stirred at 0-5°C for 2-3 hours. After the reaction was completed, the mixture was distilled at 7-8°C, and the distillate was collected to obtain (E)-1,1,1,4,4,4-hexafluoro-2-butene.

[0028] The first step of this invention involves an oxidative insertion reaction between metallic magnesium and a haloalkane R133a in a solvent to generate a Grignard reagent, CF3CH2MgCl. The second step involves the sequential addition of sulfuryl chloride for nucleophilic substitution and cyclization. Sulfonyl chloride (SO2Cl2) is added as an electrophilic reagent, reacting with the Grignard reagent to undergo nucleophilic substitution, initially forming CF3CH2-SO2Cl. Then, the sulfonyl chloride portion of this molecule reacts with another Grignard reagent molecule, ultimately forming a sulfonate intermediate. A photochlorination reaction is then carried out by introducing Cl2 / N2. Under low temperature (0-5°C) and light irradiation conditions, chlorine reacts with the methylene group of the sulfonate intermediate, introducing a chlorine atom. This introduced chlorine atom is a leaving group, preparing for the subsequent elimination reaction. Finally, through base-induced elimination and deSO2 removal, the cyclization following chlorination is eliminated under the action of a base, removing SO2 and HCl to form a C=C double bond. The Z-configuration (cis) uses inorganic bases NaOH / KOH, while the E-configuration (trans) uses organic bases such as potassium tert-butoxide / DBU.

[0029] Compared with the prior art, the beneficial effects of the present invention are: (1) The raw materials of the present invention are inexpensive and readily available, and the reaction conditions are mild. R133a is used as the raw material, which is widely available and inexpensive, thus avoiding the use of expensive or scarce raw materials. The reaction is carried out at 40~60℃ and near normal pressure, without the need for high temperature, high pressure and strong corrosive reagents, and the equipment requirements are low, which significantly reduces production costs and energy consumption.

[0030] (2) The stereoselectivity of the present invention is highly controllable. Z or E configurations can be synthesized by simply selecting different bases: inorganic bases yield Z-type and organic bases yield E-type. No additional isomerization step is required, and products can be flexibly switched on the same production line, simplifying the process and improving production flexibility.

[0031] (3) The process of the present invention is green and environmentally friendly, the separation is simple, no toxic solvents or strong corrosive substances are used, and the by-products (SO2, HCl, etc.) are easy to handle. The boiling point of the product is very different from that of the solvent, and high-purity separation can be achieved by atmospheric distillation. The post-processing is simple and suitable for industrial production. Attached Figure Description

[0032] Figure 1 The mass spectrum of the target product (Z)-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 1.

[0033] Figure 2 The gas chromatogram of the target product (Z)-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 1.

[0034] Figure 3 The gas chromatogram of standard (Z)-1,1,1,4,4,4-hexafluoro-2-butene is shown.

[0035] Figure 4 The mass spectrum of the target product (E)-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 5.

[0036] Figure 5 The gas chromatogram of the target product (E)-1,1,1,4,4,4-hexafluoro-2-butene prepared in Example 5.

[0037] Figure 6 The gas chromatogram of standard (E)-1,1,1,4,4,4-hexafluoro-2-butene is shown. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1 A method for preparing (Z)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1510 mL of ultra-dry tetrahydrofuran (water content <5 ppm) was added to a dry, sealed reactor, followed by 172.8 g of magnesium shavings and 19.48 g of 1,2-dibromoethane. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 50 °C, and R133a was introduced at a rate of 210 g / h, maintaining the system pressure at 4 bar. A total of 842.78 g was added. After the addition was completed, stirring was continued for a total of 7 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0040] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 3°C, and 400g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature and react for 1.5h. Subsequently, the reaction system was placed in an ice bath to cool to 3°C, and a 50% Cl2 / N2 mixed gas was introduced at a rate of 130g / h. A 365nm deep ultraviolet LED was used as the light source, and a total of 325.7g of chlorine gas was added. After the addition was complete, the reaction continued for 30min. Then, 1463.2g of 25% KOH aqueous solution was slowly added to the reaction solution, and the temperature was controlled at 27°C with stirring for 2.5h. After the reaction was completed, the mixture was distilled at 32-34°C, and the distillate was collected to obtain 456g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 93.54% and a purity of 99.73%. The mass spectrum of the prepared target product (Z)-1,1,1,4,4,4-hexafluoro-2-butene is shown in the figure below. Figure 1 As shown, the gas chromatogram is as follows: Figure 2 As shown. Figure 3 The gas chromatogram of standard (Z)-1,1,1,4,4,4-hexafluoro-2-butene shows a main peak retention time of 9.947 min. Figure 3 The retention time of the main peak of the (Z)-isomer standard was 9.952 min, and the retention times of the two were highly consistent, so the product was determined to be (Z)-1,1,1,4,4,4-hexafluoro-2-butene.

[0041] Example 2 A method for preparing (Z)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1490 mL of ultra-dry tetrahydrofuran (water content <5 ppm) was added to a dry, sealed reactor, followed by 160.4 g of magnesium shavings and 15.23 g of iodine granules. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 60 °C, and R133a was introduced at a rate of 230 g / h, maintaining the system pressure at 5 bar. A total of 924.42 g was added. After the addition was completed, stirring was continued for a total of 7 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0042] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 0°C, and 405g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1 hour. Subsequently, the reaction system was placed in an ice bath to cool to 0°C, and a 40% Cl2 / N2 mixed gas was introduced at a rate of 110g / h. A 365nm deep ultraviolet LED was used as the light source, and a total of 340.4g of chlorine gas was added. After the addition was complete, the reaction continued for 20 minutes. Then, 1260.2g of 20% NaOH aqueous solution was slowly added to the reaction solution, and the temperature was controlled at 32°C with stirring for 2 hours. After the reaction was completed, the solution was distilled at 32-34°C, and the fraction was collected to obtain 457.33g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 92.45% and a purity of 99.51%.

[0043] Example 3 A method for preparing (Z)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1530 mL of ultra-dry 1,4-dioxane (moisture <5 ppm) was added to a dry, sealed reactor, followed by 188.2 g of magnesium shavings and 27.97 g of 1,2-dibromoethane. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 52 °C, and R133a was introduced at a rate of 195 g / h, maintaining the system pressure at 5 bar. A total of 776.41 g was added. After the addition was completed, stirring was continued for a total of 6 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0044] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 5°C, and 402g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 2 hours. Subsequently, the reaction system was placed in an ice bath to cool to 5°C, and a 60% Cl2 / N2 mixed gas was introduced at a rate of 150g / h. A 405nm ultraviolet LED lamp was used as the light source, and a total of 295.6g of chlorine gas was added. After the addition was complete, the reaction continued for 45 minutes. Then, 1921.7g of a 20% KOH aqueous solution was slowly added to the reaction solution, and the temperature was controlled at 20°C with stirring for 3 hours. After the reaction was completed, the solution was distilled at 32-34°C, and the fraction was collected to obtain 456.41g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 92.99% and a purity of 99.55%.

[0045] Example 4 A method for preparing (Z)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1510 mL of ultra-dry 1,4-dioxane (moisture <5 ppm) was added to a dry, sealed reactor, followed by 166.1 g of magnesium shavings and 30.16 g of iodine granules. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 40 °C, and R133a was introduced at a rate of 220 g / h, maintaining the system pressure at 3 bar. A total of 880.1 g was added. After the addition was completed, stirring was continued for a total of 8 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0046] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 4°C, and 401g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1 hour. Subsequently, the reaction system was placed in an ice bath to cool to 4°C, and a 50% Cl2 / N2 mixed gas was introduced at a rate of 150g / h. A 405nm ultraviolet LED lamp was used as the light source, and a total of 379.2g of chlorine gas was added. After the addition was complete, the reaction continued for 35 minutes. Then, 851.6g of a 30% NaOH aqueous solution was slowly added to the reaction solution, and the temperature was controlled at 24°C with stirring for 2 hours. After the reaction was completed, the solution was distilled at 32-34°C, and the fraction was collected to obtain 455.75g of (Z)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 93.21% and a purity of 99.68%.

[0047] Example 5 A method for preparing (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1520 mL of ultra-dry tetrahydrofuran (water content <5 ppm) was added to a dry, sealed reactor, followed by 174.2 g of magnesium shavings and 27.48 g of iodine granules. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 50 °C, and R133a was introduced at a rate of 208 g / h, maintaining the system pressure at 4 bar. A total of 832.24 g was added. After the addition was completed, stirring was continued for a total of 7 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0048] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 3°C, and 395g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature and react for 1.5h. Subsequently, the reaction system was placed in an ice bath to cool to 3°C, and a 50% Cl2 / N2 mixed gas was introduced at a rate of 130g / h. A 365nm deep ultraviolet LED was used as the light source, and a total of 325.8g of chlorine gas was added. After the addition was complete, the reaction continued for 30min. Then, 541.8g of potassium tert-butoxide was slowly added to the reaction solution, and the temperature was controlled at 3°C ​​with stirring for 2.5h. After the reaction was completed, the mixture was distilled at 7-8°C, and the fraction was collected to obtain 450.66g of (E)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 93.55% and a purity of 99.66%. The mass spectrum of the prepared target product (E)-1,1,1,4,4,4-hexafluoro-2-butene is shown in the figure below. Figure 4 As shown, the gas chromatogram is as follows: Figure 5 As shown. Figure 6 The gas chromatogram of standard (E)-1,1,1,4,4,4-hexafluoro-2-butene shows a main peak retention time of 3.301 min. Figure 6 The retention time of the main peak of the (E)-isomer standard was 3.307 min, and the retention times of the two were basically the same, so the product was determined to be (E)-1,1,1,4,4,4-hexafluoro-2-butene.

[0049] Example 6 A method for preparing (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1530 mL of ultra-dry tetrahydrofuran (water content <5 ppm) was added to a dry, sealed reactor, followed by 160.1 g of magnesium shavings and 22.79 g of iodine granules. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 55 °C, and R133a was introduced at a rate of 195 g / h, maintaining the system pressure at 5 bar. A total of 780.27 g was added. After the addition was completed, stirring was continued for a total of 6 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0050] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 0°C, and 404 g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1.5 h. Subsequently, the reaction system was placed in an ice bath to cool to 0°C, and a 40% Cl2 / N2 mixed gas was introduced at a rate of 150 g / h. A 405 nm ultraviolet LED lamp was used as the light source, and a total of 297.1 g of chlorine gas was added. After the addition was complete, the reaction continued for 45 min. Then, 489 g of sodium tert-butoxide was slowly added to the reaction solution, and the temperature was controlled at 5°C with stirring for 2 h. After the reaction was completed, the mixture was distilled at 7-8°C, and the fraction was collected to obtain 454.52 g of (E)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 92.11% and a purity of 99.51%.

[0051] Example 7 A method for preparing (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1520 mL of ultra-dry 1,4-dioxane (moisture <5 ppm) was added to a dry, sealed reactor, followed by 190.1 g of magnesium shavings and 11.3 g of 1,2-dibromoethane. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 60 °C, and R133a was introduced at a rate of 205 g / h, maintaining the system pressure at 5 bar. A total of 819.78 g was added. After the addition was completed, stirring was continued for a total of 8 h. The gas was then stopped, and the unreacted R133a was recovered. The resulting Grignard reagent solution was stored under nitrogen protection for later use.

[0052] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 5°C, and 406 g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 2 h. Subsequently, the reaction system was placed in an ice bath to cool to 5°C, and a 60% Cl2 / N2 mixed gas was introduced at a rate of 128 g / h. A 405 nm ultraviolet LED lamp was used as the light source, and a total of 383.9 g of chlorine gas was added. After the addition was complete, the reaction continued for 20 min. Then, 732.7 g of DBU was slowly added to the reaction solution, and the temperature was controlled at 0°C with stirring for 3 h. After the reaction was completed, the mixture was distilled at 7-8°C, and the fraction was collected to obtain 458.63 g of (E)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 92.43% and a purity of 99.45%.

[0053] Example 8 A method for preparing (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane (R133a) includes the following steps: Step 1: Preparation of Grignard reagent (anhydrous and oxygen-free operation) Under nitrogen protection, 1500 mL of ultra-dry 1,4-dioxane (moisture <5 ppm) was added to a dry, sealed reactor, followed by 164.4 g of magnesium shavings and 27.62 g of 1,2-dibromoethane. The air inside the reactor was replaced three times with high-purity nitrogen. Then, R133a gas with a purity ≥99% was introduced to replace the nitrogen. The temperature was raised to 40 °C, and R133a was introduced at a rate of 225 g / h, maintaining the system pressure at 3 bar. A total of 906.16 g was added. After the addition was completed, stirring was continued for a total of 7 h. After the reaction was completed, the unreacted R133a was recovered, and the resulting Grignard reagent solution was kept for later use under nitrogen protection.

[0054] Step 2: Chlorination, cyclization and elimination reactions Under a nitrogen atmosphere, the Grignard reagent solution was cooled to 2°C, and 397g of thioyl chloride was slowly added dropwise. After the addition was complete, the mixture was allowed to naturally warm to room temperature for 1 hour. Subsequently, the reaction system was placed in an ice bath to cool to 2°C, and a 55% Cl2 / N2 mixture was introduced at a rate of 110g / h. A 365nm deep ultraviolet LED was used as the light source, and a total of 354.5g of chlorine gas was added. After the addition was complete, the reaction continued for 25 minutes. Then, 594.1g of potassium tert-butoxide was slowly added to the reaction solution, and the temperature was controlled at 2°C with stirring for 3 hours. After the reaction was completed, the mixture was distilled at 7-8°C, and the fraction was collected to obtain 446.51g of (E)-1,1,1,4,4,4-hexafluoro-2-butene, with a yield of 92.11% and a purity of 99.54%.

Claims

1. A method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane, characterized in that, The process includes the following steps: First, magnesium shavings are added to a sealed reaction vessel containing solvent, an initiator is added, the air in the sealed reaction vessel is replaced with nitrogen, 1,1,1-trifluoro-2-chloroethane is introduced, the temperature is raised to 40~60℃, and the system pressure is controlled at 3~5 bar. After the reaction, sulfuryl chloride is added dropwise to the resulting reaction solution, and the reaction is carried out at room temperature. After the reaction is completed, a chlorine-nitrogen mixture is introduced into the reaction solution after it has been cooled to 0~5℃ to carry out a photochlorination reaction. Then, an inorganic alkali solution or an organic alkali is added and mixed at a controlled temperature. The reaction mixture is purified by distillation to obtain (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene; the initiator is iodine or 1,2-dibromoethane.

2. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to claim 1, characterized in that, The inorganic alkali solution is an aqueous solution of NaOH or KOH, and the molar ratio of inorganic alkali to sulfuryl chloride is 2.1~2.3:

1. The inorganic alkali solution is added and reacted at 20~32℃. After the reaction is completed, the mixture is distilled at 32~34℃, and the fraction is collected to obtain (Z)-1,1,1,4,4,4-hexafluoro-2-butene.

3. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to claim 1, characterized in that, The organic base is potassium tert-butoxide, sodium tert-butoxide, or DBU. The molar ratio of the organic base to sulfuryl chloride is 1.6~1.8:

1. The organic base is added and reacted at 0~5℃. After the reaction is completed, the mixture is distilled at 7~8℃, and the fraction is collected to obtain (E)-1,1,1,4,4,4-hexafluoro-2-butene.

4. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to any one of claims 1-3, characterized in that, The solvent is tetrahydrofuran or 1,4-dioxane.

5. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to any one of claims 1-3, characterized in that, The molar ratio of metallic magnesium to sulfuryl chloride is 2.2~2.6:1, the molar ratio of 1,1,1-trifluoro-2-chloroethane to sulfuryl chloride is 2.2~2.6:1, and the charging rate of 1,1,1-trifluoro-2-chloroethane is 195 g / h~230 g / h.

6. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to claim 5, characterized in that, The molar ratio of initiator to thioyl chloride is 1:20~50.

7. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to any one of claims 1-3, characterized in that, The mass percentage of chlorine in a chlorine-nitrogen mixture is 40% to 60%.

8. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to claim 7, characterized in that, The photochlorination reaction controlled the flow rate of the chlorine-nitrogen mixture at 110 g / h to 150 g / h, and the molar ratio of chlorine to sulfuryl chloride was 1.4 to 1.8:

1.

9. The method for preparing (Z) / (E)-1,1,1,4,4,4-hexafluoro-2-butene from 1,1,1-trifluoro-2-chloroethane according to any one of claims 1-3, characterized in that, Control the system pressure at 3-5 bar and react for 6-8 hours; after the reaction, add sulfuryl chloride dropwise to the resulting reaction solution and react at room temperature for 1-2 hours; after cooling to 0-5℃, introduce a chlorine-nitrogen mixture into the reaction solution and react for another 20-45 minutes; add an inorganic alkali solution or an organic alkali and stir for 2-3 hours to mix and react.

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