A process for the synthesis of trans-1,2-dichloro-3,3,3-trifluoropropene

Abstract

This invention provides a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropene, comprising: isomerizing a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene in the presence of a Lewis catalyst or an ionic salt catalyst to obtain trans-1,2-dichloro-3,3,3-trifluoropropene. The synthesis method of this invention features mild and controllable reaction conditions. Under preferred conditions, the Lewis acid reaction system used in this invention achieves a conversion rate of approximately 100% for cis-1,2-dichloro-3,3,3-trifluoropropene and a selectivity of 99.6% for trans-1,2-dichloro-3,3,3-trifluoropropene.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and relates to hydrofluoroolefins, specifically to a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene. Background Technology

[0002] Hydrofluoroolefins (HFOs), with zero ozone depletion potential and low greenhouse gas potential, have become a research hotspot in the fluorocarbon industry worldwide. 2,3,3,3-Tetrafluoropropylene (HFO-1234yf) and 1,3,3,3-Tetrafluoropropylene (HFO-1234ze), due to their excellent physicochemical and environmental properties, have become effective refrigerants, foaming agents, fire extinguishing agents, heat transfer media, propellants, gaseous dielectrics, sterilizing agent carriers, power circulation working fluids, polymer monomers, and pharmaceutical and pesticide intermediates, with wide applications. 1,2-Dichloro-3,3,3-trifluoropropylene (HCFO-1223xd) is an important intermediate in the production of HFO-1234yf and HFO-1234ze, and is one of the key technologies for their industrial synthesis.

[0003] WO9745388 discloses a method for synthesizing HFC-245fa by reacting chlorofluoropropane with antimony fluorochloride. HCFO-1223xd is a product with a content varying in the range of 0.2% to 13.3%, exhibiting low selectivity and low conversion rate.

[0004] US2009043118 discloses a method for reacting 1,1,1-trifluoropropene (HFO-1243zf) with hydrogen fluoride and chlorine in the presence of a gas-phase fluorination catalyst to generate a composition comprising HFO-1234yf, 2,3-dichloro-1,1,1-trifluoropropane (HCFC-243db), 2-chloro-1,1,1-trifluoropropene (HCFO-1233xf), 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), and HCFO-1223xd, which can serve as a heat transfer composition. In this reaction, the content of HCFO-1223xd generated varies in the range of 0–20.2%, exhibiting low selectivity and low conversion. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene, thereby solving the technical problems of insufficiently mild reaction conditions and low selectivity in existing synthesis methods.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropene, the method comprising the following steps:

[0008] In the presence of a Lewis catalyst or an ionic salt catalyst, a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene undergoes an isomerization reaction to yield trans-1,2-dichloro-3,3,3-trifluoropropene.

[0009] The method for synthesizing the 1,2-dichloro-3,3,3-trifluoropropylene mixture includes the following steps:

[0010] Step 1: 2-Chloro-3,3,3-trifluoropropene is synthesized by reacting chlorine gas with 2-chloro-3,3,3-trifluoropropane in the presence of a Lewis catalyst.

[0011] Step 2: Under the action of a phase transfer catalyst, 1,2,2-trichloro-3,3,3-trifluoropropane is dehydrochlorinated in an alkaline solution to synthesize a mixture of 1,2-dichloro-3,3,3-trifluoropropene.

[0012] The phase transfer catalyst is a crown ether or polyethylene glycol.

[0013] The alkaline solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

[0014] The present invention also has the following technical features:

[0015] Specifically, the isomerization reaction is carried out at a temperature of 20–100°C, and the amount of Lewis catalyst or ionic salt catalyst used is 0.5 wt%–10 wt% of the mass of a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene, with a reaction time of 1–24 h.

[0016] Preferably, the isomerization reaction is carried out at a temperature of 40–60°C, and the amount of Lewis catalyst or ionic salt catalyst used is 2 wt%–5 wt% of the mass of a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene, and the reaction time is 2–10 h.

[0017] Specifically, in the isomerization reaction, the Lewis catalyst is ferric chloride, aluminum chloride, aluminum trifluoride, aluminum fluorochloride, aluminum trifluoromethanesulfonate, or boron trifluoride.

[0018] Specifically, in the isomerization reaction, the ionic salt catalyst is a fluorinated tin salt catalyst with the general formula Q. + [Sn x Cl y F 4x-y+1 ]- Cation Q + It is a quaternary ammonium cation, 1≤x≤2, 0≤y≤2.

[0019] Preferably, in the isomerization reaction, the quaternary ammonium cation is a tetraalkylammonium cation, a trialkylimidazolium cation, an N-alkylpyridinium cation, or an N-alkyl-N-methylpiperidinium cation.

[0020] More preferably, in the isomerization reaction, the quaternary ammonium cation is dodecyltrimethylammonium cation, phenyltrimethylammonium cation, 1-butyl-2,3-dimethylimidazolium cation, N-butylpyridinium cation, N-benzylmethylpyridinium cation, or N-butyl-N-methylpiperidinium cation.

[0021] Specifically, in step 1, the reaction temperature is 40℃~80℃ and the reaction time is 2h~5h; in step 2, the reaction temperature is 50℃~80℃ and the reaction time is 2h~4h.

[0022] Specifically, in step 1, the Lewis catalyst is ferric chloride, ferric bromide, aluminum chloride, or boron trifluoride.

[0023] Specifically, in step 2, the crown ether is 15-crown-5, dicyclohexano-18-crown-6, or dibenzo-18-crown-6; the polyethylene glycol is polyethylene glycol-4000, polyethylene glycol-6000, or polyethylene glycol-8000.

[0024] Specifically, in step 1, the amount of Lewis catalyst used is 1 wt% to 2 wt% of the mass of 2-chloro-3,3,3-trifluoropropene; the molar ratio of chlorine gas to 2-chloro-3,3,3-trifluoropropene is 1.5 to 2:1.

[0025] Specifically, in step 2, the amount of phase transfer catalyst used is 1 wt% to 3 wt% of the mass of 1,2,2-trichloro-3,3,3-trifluoropropane; the molar ratio of the base to 1,2,2-trichloro-3,3,3-trifluoropropane is 1.5 to 2:1.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] (I) The synthesis method of the present invention has mild and controllable reaction conditions.

[0028] (II) The Lewis acid reaction system used in this invention, under preferred conditions, achieves a conversion rate of ~100% for cis-1,2-dichloro-3,3,3-trifluoropropene and a selectivity of 99.6% for trans-1,2-dichloro-3,3,3-trifluoropropene.

[0029] (III) This invention provides a simple and efficient method for synthesizing a mixture of raw materials 1,2-dichloro-3,3,3-trifluoropropylene, which is easy to implement industrially. Attached Figure Description

[0030] Figure 1 The image shows the GC-MS spectrum of trans-1,2-dichloro-3,3,3-trifluoropropene synthesized in Example 1.

[0031] Figure 2 The image shows the GC-MS spectrum of 1,2,2-trichloro-3,3,3-trifluoropropane synthesized in Example 21 of this invention.

[0032] Figure 3 This is the GC-MS spectrum of the 1,2-dichloro-3,3,3-trifluoropropylene mixture synthesized in Example 31 of this invention.

[0033] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the prior art.

[0035] Unless otherwise specified, the scientific and technical terms used herein are intended to be understood by one of ordinary skill in the art. It should also be understood that temperatures and concentrations used herein are approximate and for illustrative purposes. While similar or equivalent methods and materials may be used in the implementation of this disclosure, some suitable methods and materials are described below. Publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in part, and in case of conflict, this document shall prevail. Furthermore, the materials, methods, solution concentrations, and examples described are exemplary only and are not intended to be limiting. In specific embodiments, those skilled in the art can optimize the proportions, concentrations, and operating parameters of the substances involved in the method using conventional experimental periods based on the disclosure of this invention to achieve the objectives of this invention.

[0036] In this invention, the operating pressure of the reaction is mainly controlled by the saturated vapor pressure of the reactants at the reaction temperature, and is generally not strictly controlled. It can be carried out at pressures below, equal to, or above atmospheric pressure, preferably above atmospheric pressure. Furthermore, the reaction of this invention can be operated intermittently or continuously, and the reaction itself has no significant requirements regarding the reaction mode.

[0037] The present invention will be further described in detail below with reference to the embodiments, but this does not limit the scope of the invention. In the following embodiments, the conversion rate and selectivity of the reactants were detected using GC-MS.

[0038] It should be noted that the 1,2-dichloro-3,3,3-trifluoropropene mixture is a mixture of cis-1,2-dichloro-3,3,3-trifluoropropene and trans-1,2-dichloro-3,3,3-trifluoropropene.

[0039] The mixture of raw material 1,2-dichloro-3,3,3-trifluoropropene can be replaced with pure raw material cis-1,2-dichloro-3,3,3-trifluoropropene during the reaction with basically the same effect. In the following examples, only the mixture of raw material 1,2-dichloro-3,3,3-trifluoropropene is used. Examples of raw material cis-1,2-dichloro-3,3,3-trifluoropropene will not be repeated.

[0040] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0041] Example 1:

[0042] This embodiment provides a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene, which includes the following steps:

[0043] 82.5 g of a mixture of 1,2-dichloro-3,3,3-trifluoropropene and 1.65 g of aluminum trichloride were added to a 250 mL stainless steel high-pressure reactor with a stirrer. The temperature was raised to 40 °C, and the reaction was carried out for 10 h. The reaction was then stopped by cooling. Samples were taken for GC analysis. The conversion rate of cis-1,2-dichloro-3,3,3-trifluoropropene was 100%, and the selectivity of trans-1,2-dichloro-3,3,3-trifluoropropene was 99.3%.

[0044] The GC-MS detection of the above product, trans-1,2-dichloro-3,3,3-trifluoropropene, yielded the following mass spectrometry results: Figure 1 As shown, the relevant peak assignments are as follows: m / z 164 is the molecular ion peak, m / z 145 is the ion peak after F removal from CF3CCl=CHCl, m / z 129 is the ion peak after Cl removal from CF3CCl=CHCl, m / z 95 is the ion peak after CF3CCl=CHCl after CF3 removal, and m / z 69 is the CF3 ion peak.

[0045] The reaction products were detected by gas chromatography. The chromatographic conditions were as follows: vaporization chamber 200℃, detector 200℃, GasPro column (30m × 0.25mm) was used, initial column temperature 50℃, held for 5 minutes, then programmed to 200℃ at 15℃ / min, held for 10 minutes. The peak position of the product trans-1,2-dichloro-3,3,3-trifluoropropene was 10.7 min, and the peak position of the raw material mixture cis-1,2-dichloro-3,3,3-trifluoropropene was 11.4 min.

[0046] The above data proves that the product obtained is trans-1,2-dichloro-3,3,3-trifluoropropene.

[0047] Example 2:

[0048] This embodiment provides a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene, which includes the following steps:

[0049] Add 82.5 g of 1,2-dichloro-3,3,3-trifluoropropylene mixture and 2.48 g of [NPhMe3][Sn] to a 250 mL stainless steel high-pressure reactor with a stirrer. 1.5 Cl 0.5 F 6.5 The temperature was raised to 60℃ and reacted for 5 hours. The reaction was then stopped by cooling. Samples were taken for GC analysis. The conversion rate of cis-1,2-dichloro-3,3,3-trifluoropropene was 100%, and the selectivity of trans-1,2-dichloro-3,3,3-trifluoropropene was 99.6%.

[0050] The characterization results of the product trans-1,2-dichloro-3,3,3-trifluoropropylene in this embodiment are basically the same as those in Example 1.

[0051] Examples 3-15:

[0052] This embodiment provides a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene, which is basically the same as the synthesis method given in Example 1, except that the catalyst and its amount are changed in Examples 3 to 15. The reaction results are shown in Table 1.

[0053] Table 1. Reaction results of Examples 3 to 15

[0054]

[0055]

[0056] The characterization results of the product trans-1,2-dichloro-3,3,3-trifluoropropylene in Examples 3 to 15 were basically the same as those in Example 1.

[0057] Examples 16-20:

[0058] This embodiment provides a method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene, which is basically the same as the synthesis method given in Example 2, except that the reaction temperature and reaction time are different in Examples 3 to 11. The reaction results are shown in Table 2.

[0059] Table 2 Reaction results of Examples 16 to 20

[0060] Example Reaction temperature (°C) Reaction time (h) Raw material conversion rate (%) Product selectivity (%) 16 100 1 97.2 95.3 17 80 2 99.8 98.4 18 60 5 100 99.1 19 40 12 100 98.5 20 20 24 98.6 95.1

[0061] The characterization results of the product trans-1,2-dichloro-3,3,3-trifluoropropylene in Examples 16 to 20 were basically the same as those in Example 1.

[0062] Example 21:

[0063] This embodiment provides a method for synthesizing 1,2,2-trichloro-3,3,3-trifluoropropane, which includes the following steps:

[0064] 65.25 g of 2-chloro-3,3,3-trifluoropropene and 1.31 g of aluminum trichloride were added to a 250 mL stainless steel high-pressure reactor with a stirrer. The temperature was raised to 40 °C, and after stirring was started, 71 g of chlorine gas was introduced to maintain the reaction pressure at 0.3 MPa. The reaction was carried out for 5 h. The temperature was then lowered to stop the reaction. A sample was taken for GC analysis. The conversion rate of 2-chloro-3,3,3-trifluoropropene was 100%, and the selectivity of 1,2,2-trichloro-3,3,3-trifluoropropane was 98.5%.

[0065] The GC-MS analysis of the above product 1,2,2-trichloro-3,3,3-trifluoropropane yielded the following mass spectrometry results: Figure 2 As shown, the relevant peak values ​​are attributed as follows:

[0066] m / z 200 is the molecular ion peak, m / z 165 is the ion peak after Cl removal from CF3CCl2CH2Cl, m / z 151 is the ion peak after CH2Cl removal from CF3CCl2CH2Cl, m / z 131 is the ion peak after CF3CCl2CH2Cl removal from CF3, m / z 95 is the CCl2CH ion peak, m / z 69 is the CF3 ion peak, and m / z 49 is the CH2Cl ion peak.

[0067] The above data proves that the product obtained is 1,2,2-trichloro-3,3,3-trifluoropropane.

[0068] Examples 22-25:

[0069] This embodiment provides a method for synthesizing 1,2,2-trichloro-3,3,3-trifluoropropane, which is basically the same as the synthesis method in Example 21, except that the catalyst and its amount are changed in Examples 22 to 25. The reaction results are shown in Table 3.

[0070] Table 3 Reaction results of Examples 22 to 25

[0071] Example catalyst Catalyst dosage (%) Raw material conversion rate (%) Product selectivity (%) 22 - - 56.5 96.4 23 Ferric chloride 2 100 97.6 24 Ferric tribromide 5 100 92.0 25 Boron trifluoride 0.5 100 98.5

[0072] The characterization results of the product 1,2,2-trichloro-3,3,3-trifluoropropane in Examples 22 to 25 were basically the same as those in Example 21.

[0073] Examples 26-30:

[0074] This embodiment provides a method for synthesizing 1,2,2-trichloro-3,3,3-trifluoropropane, which is basically the same as the synthesis method in Example 21. The only difference is that the molar ratio of chlorine to 2-chloro-3,3,3-trifluoropropene, the reaction temperature and the reaction time are changed in Examples 26 to 30. The reaction results are shown in Table 4.

[0075] Table 4. Reaction results of Examples 26 to 30

[0076]

[0077] The characterization results of the product 1,2,2-trichloro-3,3,3-trifluoropropane in Examples 26 to 30 were basically the same as those in Example 21.

[0078] Example 31:

[0079] This embodiment provides a method for synthesizing a mixture of 1,2-dichloro-3,3,3-trifluoropropylene by dehydrochlorination in an alkaline solution. The method includes the following steps:

[0080] 42 g of 40% (w / w) KOH aqueous solution, 40.3 g of 1,2,2-trichloro-3,3,3-trifluoropropane, and 0.4 g of polyethylene glycol-4000 (1 wt%) were sequentially added to a reactor equipped with a stirrer. The stirring was started, and the reaction temperature was controlled at 80 °C. After reacting for 4 h, the reactants were cooled to room temperature, and the organic matter was collected after phase separation for gas chromatography analysis. The results showed that the conversion rate of 1,2,2-trichloro-3,3,3-trifluoropropane was 100%, and the conversion rate of the (cis + trans) 1,2-dichloro-3,3,3-trifluoropropene mixture was 99.5%.

[0081] The GC-MS analysis of the above-mentioned product, 1,2-dichloro-3,3,3-trifluoropropylene mixture, yielded the following mass spectrometry results: Figure 3As shown, the relevant peak assignments are as follows: m / z 164 is the molecular ion peak, m / z 145 is the ion peak after F removal from CF3CCl=CHCl, m / z 129 is the ion peak after Cl removal from CF3CCl=CHCl, m / z 95 is the ion peak after CF3CCl=CHCl after CF3 removal, and m / z 69 is the CF3 ion peak.

[0082] 1 H NMR (500MHz, CDCl3) δ7.16 (d, J = 1.2Hz, 1H);

[0083] 13 C NMR (126MHz, CDCl3) δ125.65 (q, J = 5.6Hz), 124.68 (q, J = 38.0Hz), 119.87 (q, J = 272.5Hz);

[0084] 19 F NMR (471MHz, CDCl3) δ-68.31.

[0085] The reaction products were detected by gas chromatography. The chromatographic conditions were as follows: vaporization chamber 200℃, detector 200℃, gaspro column with specifications of 30m×0.25mm, initial column temperature of 50℃, constant temperature for 5 minutes, temperature increased to 200℃ at a programmed rate of 15℃ / min, and constant temperature for 10 minutes.

[0086] In the mixture of 1,2-dichloro-3,3,3-trifluoropropene, the peak position of trans-1,2-dichloro-3,3,3-trifluoropropene is 10.7 min, and the peak position of cis-1,2-dichloro-3,3,3-trifluoropropene is 11.4 min.

[0087] The above data proves that the product obtained is a mixture of 1,2-dichloro-3,3,3-trifluoropropylene.

[0088] Example 32:

[0089] This embodiment provides a method for synthesizing a mixture of 1,2-dichloro-3,3,3-trifluoropropylene by dehydrochlorination in an alkaline solution. The method includes the following steps:

[0090] 40 g of NaOH (40 wt%) aqueous solution, 40.3 g of 1,2,2-trichloro-3,3,3-trifluoropropane, and 0.2 g of dicyclohexano-18-crown-6 (0.5 wt%) were sequentially added to a stirrer-equipped reactor. The stirring was started, and the reaction temperature was controlled at 120 °C. After reacting for 4 h, the reactants were cooled to room temperature, and the organic matter was collected after phase separation for gas chromatography analysis. The results showed that the conversion rate of 1,2,2-trichloro-3,3,3-trifluoropropane was 100%, and the (cis + trans) 1,2-dichloro-3,3,3-trifluoropropene mixture was 98.5%.

[0091] The characterization results of the product 1,2-dichloro-3,3,3-trifluoropropylene mixture in Example 32 were basically the same as those in Example 31.

[0092] Examples 33-36:

[0093] This embodiment provides a method for synthesizing a mixture of 1,2-dichloro-3,3,3-trifluoropropylene by dehydrochlorination in an alkaline solution. This method is basically the same as the synthesis method in Example 31, except that the catalyst and its amount are changed in Examples 33 to 36. The reaction results are shown in Table 5.

[0094] Table 5 Reaction results of Examples 33 to 36

[0095] Example catalyst Catalyst dosage (%) Raw material conversion rate (%) Product selectivity (%) 33 15-crown-5 1 100 98.9 34 Dibenzo-18-crown-6 3 100 99.1 35 Polyethylene glycol-6000 3 100 99.3 36 Polyethylene glycol-8000 10 100 97.2

[0096] The characterization results of the product 1,2-dichloro-3,3,3-trifluoropropylene mixture in Examples 33 to 36 were basically the same as those in Example 31.

[0097] Examples 37-41:

[0098] This embodiment provides a method for synthesizing a mixture of 1,2-dichloro-3,3,3-trifluoropropene by dehydrochlorination in an alkaline solution. This method is basically the same as the synthesis method in Example 31, except that the molar ratio of alkali to 1,2,2-trichloro-3,3,3-trifluoropropane, the reaction temperature, and the reaction time are changed in Examples 37 to 41. The reaction results are shown in Table 6.

[0099] Table 6 shows the reaction results of Examples 37 to 41.

[0100]

[0101] The characterization results of the product 1,2-dichloro-3,3,3-trifluoropropylene mixture in Examples 37 to 41 were basically the same as those in Example 31.

[0102] The above description is only a partial embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropene, characterized in that, The method includes the following steps: In the presence of an ionic salt catalyst, a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene undergoes an isomerization reaction to give trans-1,2-dichloro-3,3,3-trifluoropropene. In the isomerization reaction, the ionic salt catalyst is a fluorinated tin salt catalyst with the general formula Q. + [Sn x Cl y F 4x-y+1 ] - Cation Q + It is a quaternary ammonium cation, 1≤x≤2, 0≤y≤2; The isomerization reaction is carried out at a temperature of 20–100°C, the amount of ionic salt catalyst is 0.5 wt%–10 wt% of the mass of a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene, and the reaction time is 1–24 h. The method for synthesizing the 1,2-dichloro-3,3,3-trifluoropropylene mixture includes the following steps: Step 1: 2-Chloro-3,3,3-trifluoropropene is synthesized by reacting with chlorine gas in the presence of a Lewis catalyst to synthesize 1,2,2-trichloro-3,3,3-trifluoropropane; Step 2: Under the action of a phase transfer catalyst, 1,2,2-trichloro-3,3,3-trifluoropropane is dehydrochlorinated in an alkaline solution to synthesize a mixture of 1,2-dichloro-3,3,3-trifluoropropene. The phase transfer catalyst is polyethylene glycol; The alkaline solution is an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

2. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, The isomerization reaction is carried out at a temperature of 40–60°C, the amount of ionic salt catalyst used is 2 wt%–5 wt% of the mass of a mixture of 1,2-dichloro-3,3,3-trifluoropropene or cis-1,2-dichloro-3,3,3-trifluoropropene, and the reaction time is 2–10 h.

3. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, In the isomerization reaction, the quaternary ammonium cation is a tetraalkylammonium cation, a trialkylimidazolium cation, an N-alkylpyridinium cation, or an N-alkyl-N-methylpiperidinium cation.

4. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 3, characterized in that, In the isomerization reaction, the quaternary ammonium cation is dodecyltrimethylammonium cation, phenyltrimethylammonium cation, 1-butyl-2,3-dimethylimidazolium cation, N-butylpyridinium cation, N-benzylmethylpyridinium cation, or N-butyl-N-methylpiperidinium cation.

5. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, In step 1, the reaction temperature is 40℃~80℃ and the reaction time is 2h~5h; in step 2, the reaction temperature is 50℃~80℃ and the reaction time is 2h~4h.

6. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, In step 1, the Lewis catalyst is ferric chloride, ferric bromide, aluminum chloride, or boron trifluoride.

7. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, In step 2, the polyethylene glycol is polyethylene glycol-4000, polyethylene glycol-6000, or polyethylene glycol-8000.

8. The method for synthesizing trans-1,2-dichloro-3,3,3-trifluoropropylene as described in claim 1, characterized in that, In step 1, the amount of Lewis catalyst used is 1 wt% to 2 wt% of the mass of 2-chloro-3,3,3-trifluoropropene; the molar ratio of chlorine gas to 2-chloro-3,3,3-trifluoropropene is 1.5 to 2:

1. In step 2, the amount of phase transfer catalyst used is 1 wt% to 3 wt% of the mass of 1,2,2-trichloro-3,3,3-trifluoropropane; the molar ratio of the base to 1,2,2-trichloro-3,3,3-trifluoropropane is 1.5 to 2:1.

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