Method for halogen-mediated diaphragm-free electro-synthesis of cyclic carbonates and use thereof

Abstract

The application discloses a halogen-mediated diaphragm-free electro-synthesis method of cyclic carbonates and application thereof. The method comprises the following steps: using a diaphragm-free flow reactor to carry out electrochemical reaction, adding a halogen salt, a carbonate and an optional inorganic passivator as a supporting electrolyte in a water and N,N-dimethylformamide solvent, and preparing cyclic carbonates by one-pot method at room temperature under a constant current condition with olefins and carbon dioxide as raw materials. The application is the first report of the one-pot electrochemical preparation of ethylene to ethylene carbonate, and the faradic efficiency of ethylene carbonate is high, the productivity is high, the current density is large, and the stable operation time is 350 hours, so that the application has an industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic electrochemical synthesis, in particular to a halogen-mediated membrane-free electrochemical synthesis method of cyclic carbonates and its application. BACKGROUND

[0002] Ethylene carbonate (EC) is an excellent solvent widely used in the field of lithium-ion batteries. The existing industrial route for EC production involves a high-temperature (100-200 °C) and high-pressure (3.5-10 MPa) thermal catalytic reaction between epoxide and carbon dioxide (CO2). In addition, the process requires a large amount of halogen-containing homogeneous catalyst, further increasing the downstream separation cost, while the corresponding raw material ethylene oxide is extracted from fossil fuels through an energy-intensive aerobic silver catalytic epoxidation process. Although there have been electrochemical studies that successfully convert alkenes to the corresponding epoxides (intermediates of cyclic carbonates) using various oxidation or reduction mechanisms, further reactions are still needed from epoxides to cyclic carbonates. Given the growing market demand for cyclic carbonates and the high demand for green production, direct electrochemical synthesis of cyclic carbonates is a simple and energy-saving method, and it is imperative to develop a sustainable and mild alternative synthesis method.

[0003] Zhang et al. studied the electrochemical addition of epoxide and CO2 in an acetonitrile system, assisted by BMIMBr as a co-catalyst, and obtained the cyclic carbonate of styrene (90.7%) at 50 °C with high yield, but the gaseous epoxide (propylene oxide) did not react well, and only propylene carbonate was obtained with a yield of 48.3% (Green Chem. 2013, 15(8), 2086-2090).

[0004] Jiang et al. used an electrochemical method to successfully convert aromatic and aliphatic alkenes to iodoalcohol intermediates using iodide as a medium, and reacted with CO2 to obtain the corresponding cyclic carbonate with high yield, but experiments found that gaseous alkenes such as ethylene and propylene could not obtain the corresponding cyclic carbonate (Electrochem. Commun. 2013, 34, 242-245).

[0005] In 2024, Nam et al. reported a succinimide and bromine-mediated EC tandem preparation strategy, which was driven by electrochemistry for the generation of initial bromine and base. However, this strategy involves four independent reaction steps for the final synthesis of EC, highlighting the need for a simplified one-pot EC electrochemical synthesis method (Nat. Synth 2024, 3, 846-857).

[0006] Electrochemical conversion of liquid olefins to cyclic carbonates has a good one-pot system, but the study of gaseous olefins to the corresponding cyclic carbonates is still challenging due to the inertness of gaseous olefins, and it is necessary to design an efficient electro-synthesis system and one-pot preparation of high value-added gaseous olefins under mild conditions. SUMMARY

[0007] In view of the above technical problems and the deficiencies in the field, the present application provides a halogen-mediated membraneless electro-synthesis of cyclic carbonates and its application, which can overcome the problems of high energy consumption, poor electrochemical method compatibility or complex reaction steps in the preparation of gaseous olefins to cyclic carbonates in the prior art.

[0008] The present application uses a membraneless flow reactor to prepare high value-added cyclic carbonates such as ethylene carbonate and propylene carbonate by one-pot method, which greatly reduces the cost of the reactor and simplifies the electrochemical operation; and the Faraday efficiency of olefins to cyclic carbonates is high, the current density is large, and the reaction time is short.

[0009] [1] A halogen-mediated membraneless electro-synthesis of cyclic carbonates, comprising: using a membraneless flow reactor to carry out an electrochemical reaction, adding halide salt, carbonate salt and optionally adding inorganic passivation agent (i.e. inorganic passivation agent can be added or not) as supporting electrolyte in water and N,N-dimethylformamide (DMF) solvent, and one-pot preparation of cyclic carbonates from olefins and carbon dioxide as raw materials at room temperature under constant current conditions.

[0010] The halide salt can include at least one of potassium chloride, ammonium bromide, potassium bromide, cesium bromide, lithium bromide, potassium iodide, etc., and preferably includes at least one of potassium bromide and cesium bromide.

[0011] The carbonate salt can include at least one of sodium carbonate, potassium carbonate, cesium carbonate, etc., and preferably includes at least one of potassium carbonate and cesium carbonate.

[0012] The inorganic passivation agent can include at least one of potassium dichromate, potassium molybdate, potassium ferrate, etc., and preferably includes potassium dichromate.

[0013] The olefin can include at least one of gaseous olefin, liquid olefin, etc.

[0014] The gaseous olefin can include at least one of ethylene and propylene.

[0015] The liquid olefin can include at least one of styrene and allyl benzene.

[0016] [1] The method, wherein the anode material can include at least one of iridium dioxide-insoluble anode (IrO2-DSA), platinum, carbon paper, graphite, etc., and preferably is IrO2-DSA.

[0017] [1] The method, wherein the cathode material can include at least one of foamed nickel, nickel sheet, etc., and preferably is foamed nickel.

[0018] The concentration of the halide salt in the supporting electrolyte can be 0.1-0.5 M, preferably 0.15-0.5 M, for example 0.3-0.5 M, etc., the concentration of the carbonate salt can be 0.1-0.4 M, for example 0.2 M, etc., the concentration of the inorganic passivator can be 0-10 mM, preferably (1 / 400)-0.01 M, further preferably (1 / 400)-(1 / 150) M, and the volume ratio of water and N,N-dimethylformamide is not less than 1:1, preferably (8:2)-(6:4), for example 7:3, etc.

[0019] [1] The method, wherein the supporting electrolyte is adjusted in pH by the carbonate salt. The pH of the supporting electrolyte is preferably 7.5-8.5, further preferably 8.0-8.4.

[0020] The current density in the constant current condition can be 5-250 mA / cm 2 , further can be 10-250 mA / cm 2 , for example 20 mA / cm 2 , etc.

[0021] The molar ratio of the halide salt and the inorganic passivator can be 1:0-200, preferably 1:50-200.

[0022] In some embodiments, [1] the method, wherein carbon dioxide is bubbled into the supporting electrolyte to saturation, the circulation of the supporting electrolyte is started, gaseous olefin is bubbled into the flow reactor without diaphragm and / or liquid olefin is added during the constant current electrolysis, and carbon dioxide is bubbled into the supporting electrolyte. Further, after the electrolysis time is over, the bubbling of carbon dioxide is continued, while gaseous olefin is bubbled or not, until the active halogen is completely consumed, which is the reaction stop, and a cyclic carbonate is obtained in one pot.

[0023] [2] The use of the method according to [1] in the preparation of cyclic carbonates.

[0024] The application successfully realizes one-pot preparation of high value-added product cyclic carbonate by halogen-mediated electrochemical method, the participation of halogen avoids the addition of additional oxidant, and the halogen alcohol produced by gaseous olefin and active halogen has high reactivity, thereby successfully realizing high faradaic efficiency, high productivity and large current density production of corresponding cyclic carbonate; the addition of carbonate makes the system present bicarbonate buffer system under carbon dioxide condition, avoids the strong acid environment caused by halogen electrolysis, makes halogen alcohol can be ring-added with carbon dioxide to prepare corresponding cyclic carbonate, and further ensures the environment matching of multi-step reaction kinetics under membrane-free system; the system uses membrane-free flow reactor, avoids the use of expensive ion exchange membrane, and reduces the production cost; the electrochemical oxidation of halogen in the system, the conversion of olefin to halogen alcohol and the production of halogen alcohol to cyclic carbonate are carried out in the same reactor at the same time, which simplifies the electrochemical preparation process of cyclic carbonate.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] The application is the first report of one-pot electrochemical preparation of ethylene to ethylene carbonate, and the faradaic efficiency of ethylene carbonate is high, the productivity is high, the current density is large, and the system can be stably operated for 350 hours, which has industrial application prospect.

[0027] The application uses inorganic passivation agent to inhibit halogen reduction and further avoids the use of ion exchange membrane, which greatly reduces the production cost.

[0028] The application uses carbonate to construct bicarbonate buffer system (pH is about 8), and the weak alkaline environment provides an ideal environment for electrolysis of halogen, addition reaction of olefin and active halogen, and ring addition of halogen alcohol and carbon dioxide, which is an effective guarantee for electrochemical one-pot preparation of cyclic carbonate.

[0029] The application is suitable for production of other olefins to cyclic carbonates, and can provide a new idea for preparation of propylene carbonate and phenylpropylene cyclic carbonate from propylene, allyl benzene and CO2 under electrochemical conditions. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is a schematic diagram of the halogen-mediated electrochemical synthesis system of ethylene carbonate of the application.

[0031] Figure 2 It is a stability test data result graph of the halogen-mediated electrochemical synthesis process of ethylene carbonate of the application. DETAILED DESCRIPTION

[0032] The application will be further described below in combination with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the application and not to limit the scope of the application.

[0033] The flow rates of CO2 and gaseous olefins in the present application were controlled by mass flow controllers (CS200-A, Beijing Sevenstarflow), which were set at 80 sccm and 30 sccm, respectively, unless otherwise specified. The mass flow controllers and flow rates were not limited.

[0034] A peristaltic pump (L100-1S-2, Longer) was used to pass through the flow cell at a flow rate of 10 mL / min, and the peristaltic pump and flow rate were not limited.

[0035] Example 1

[0036] Combination Figure 1 A 0.2 M Cs2CO3, 0.5 M KBr and 3 mM K2Cr2O7 solution was dissolved in 30 mL of a mixed solution of DMF-water (volume ratio of 3:7) as the electrolyte for the electrochemical synthesis of ethylene carbonate. Before electrolysis, CO2 was bubbled until the solution was saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, a current density of 20 mA / cm2was applied at room temperature for 13 h, with an IrO2-DSA anode (2 cm2, 1 mm thick) as the anode and a nickel foam cathode (2 cm2, 1 mm thick) as the cathode. During the electrolysis, a three-way valve was used to bubble ethylene directly into the flow reactor without a diaphragm, and CO2 was bubbled in the solvent bottle, while the pH of the system was monitored using an online pH meter, and the pH of the electrolyte was measured to be 8.05-8.27. After the reaction was completed, ethylene and carbon dioxide were continued to be bubbled until the active halogen was completely consumed, and the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 77.3%, and the productivity was 0.58 mmol / h. 2 2 2

[0037] Comparative Examples 1-3 studied the effect of anode materials on the electrochemical synthesis performance of ethylene to ethylene carbonate.

[0038] Comparative Example 4 studied the effect of cathode materials on the electrochemical synthesis performance of ethylene to ethylene carbonate.

[0039] Comparative Examples 5-6 studied the effect of inorganic passivators on the electrochemical synthesis performance of ethylene to ethylene carbonate.

[0040] Comparative Examples 7-8 studied the effect of the volume ratio of water and N,N-dimethylformamide on the electrochemical synthesis performance of ethylene to ethylene carbonate.

[0041] Comparative Example 1

[0042] In a similar manner to Example 1, except that carbon paper was used as the anode material.​​​

[0043] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 59.2% and the productivity was 0.44 mmol / h.

[0044] Comparative Example 2

[0045] The procedure of Example 1 was followed except that platinum sheet was used as the anode material.

[0046] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 37.9% and the productivity was 0.28 mmol / h.

[0047] Comparative Example 3

[0048] The procedure of Example 1 was followed except that graphite was used as the anode material.

[0049] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 36.7% and the productivity was 0.31 mmol / h.

[0050] Comparative Example 4

[0051] The procedure of Example 1 was followed except that nickel sheet was used as the cathode material.

[0052] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 41.0% and the productivity was 0.20 mmol / h.

[0053] Comparative Example 5

[0054] The procedure of Example 1 was followed except that potassium molybdate was used as the inorganic passivating agent.

[0055] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 67.4% and the productivity was 0.50 mmol / h.

[0056] Comparative Example 6

[0057] The procedure of Example 1 was followed except that potassium ferrate was used as the inorganic passivating agent.

[0058] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 50.2% and the productivity was 0.37 mmol / h.

[0059] Comparative Example 7

[0060] The procedure of Example 1 was followed except that the volume ratio of DMF-water was 2:8.

[0061] Gas phase analysis, the faradaic efficiency of ethylene carbonate was 65.2% and the productivity was 0.49 mmol / h.

[0062] Comparative Example 8

[0063] The method is similar to that in Example 1, except that the volume ratio of DMF to water is 5:5.

[0064] Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 55.4%, and its productivity was 0.41 mmol / h.

[0065] Example 2

[0066] 0.2 M Cs₂CO₃, 0.5 M CsBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 The cathode was a 1 mm thick electrode. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. Simultaneously, an online pH meter was used to monitor the pH changes of the system, and the electrolyte pH was measured to be 8.13-8.39. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 77.8%, and its productivity was 0.58 mmol / h.

[0067] Example 3

[0068] 0.2 M K₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 26.9%, and its productivity was 0.20 mmol / h.

[0069] Example 4

[0070] A 0.2 M Li2CO3, 0.5 M LiBr and 3 mM K2Cr2O7 solution was dissolved in 30 mL of a DMF-water (3:7 by volume) mixture as the electrolyte for the electro-synthesis of vinyl carbonate. Prior to electrolysis, CO2 was bubbled through the solution until saturation was achieved, and then circulated through the flow cell using a peristaltic pump (L100-1S-2, Longer) at a flow rate of 10 mL / min. Subsequently, the cell was polarized at a current density of 20 mA / cm2for 13 h at room temperature with an IrO2-DSA anode as the anode (2 cm2, 1 mm thick) and a nickel foam cathode (2 cm2, 1 mm thick) as the cathode. During the polarization, ethylene was bubbled directly into the flow reactor using a three-way valve, and CO2 was bubbled in the solvent bottle. After the reaction was completed, the bubbling of ethylene and carbon dioxide was continued until the active halide was completely consumed. Gas phase analysis showed that the faradaic efficiency of the vinyl carbonate was 17.8%, and the productivity was 0.13 mmol / h. 2 2 2 2 2 2

[0071] Example 5

[0072] A 0.2 M K2CO3, 0.1 M KBr, 0.4 M CsBr and 3 mM K2Cr2O7 solution was dissolved in 30 mL of a DMF-water (3:7 by volume) mixture as the electrolyte for the electro-synthesis of vinyl carbonate. Prior to electrolysis, CO2 was bubbled through the solution until saturation was achieved, and then circulated through the flow cell using a peristaltic pump (L100-1S-2, Longer) at a flow rate of 10 mL / min. Subsequently, the cell was polarized at a current density of 20 mA / cm2for 13 h at room temperature with an IrO2-DSA anode as the anode (2 cm2, 1 mm thick) and a nickel foam cathode (2 cm2, 1 mm thick) as the cathode. During the polarization, ethylene was bubbled directly into the flow reactor using a three-way valve, and CO2 was bubbled in the solvent bottle. After the reaction was completed, the bubbling of ethylene and carbon dioxide was continued until the active halide was completely consumed. Gas phase analysis showed that the faradaic efficiency of the vinyl carbonate was 71.1%, and the productivity was 0.53 mmol / h.

[0073] Example 6

[0074] ​​​​​​0.2 M Cs₂CO₃, 0.5 M LiBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 The cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. Simultaneously, an online pH meter was used to monitor the pH changes of the system, and the electrolyte pH was measured to be 8.07-8.48. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 41.7%, with a productivity of 0.31 mmol / h.

[0075] Example 7

[0076] 0.2 M Cs₂CO₃, 0.5 M KCl, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 The cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragm-free flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. Simultaneously, an online pH meter was used to monitor the pH changes of the system, and the electrolyte pH was measured to be 7.86-8.05. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 24.5%, with a productivity of 0.183 mmol / h.

[0077] Example 8

[0078] A 0.2 M Cs2CO3, 0.5 M KBr and 3 mM K2Cr2O7solution in 30 mL of a DMF-water (3:7 by volume) mixture was used as the electrolyte for the electro-synthesis of vinyl carbonate. Prior to electrolysis, the solution was saturated with CO2bubbling and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). The cell was then powered at a current density of 10 mA / cm2 2 for 26 h at room temperature with an IrO2-DSA anode as the anode (2 cm 2 , 1 mm thick) and a nickel foam cathode (2 cm 2 , 1 mm thick) as the cathode. During the power on period, ethylene was bubbled directly into the flow reactor using a three-way valve, while CO2was bubbled in the solvent bottle. After the reaction was complete, bubbling of ethylene and carbon dioxide was continued until the active halogen was completely consumed. Gas phase analysis showed a Faraday efficiency of 78.0% for vinyl carbonate with a productivity of 0.29 mmol / h.

[0079] Example 9

[0080] A 0.2 M Cs2CO3, 0.5 M KBr and 3 mM K2Cr2O7solution in 30 mL of a DMF-water (3:7 by volume) mixture was used as the electrolyte for the electro-synthesis of vinyl carbonate. Prior to electrolysis, the solution was saturated with CO2bubbling and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). The cell was then powered at a current density of 30 mA / cm2 2 for 8.67 h at room temperature with an IrO2-DSA anode as the anode (2 cm 2 , 1 mm thick) and a nickel foam cathode (2 cm 2 , 1 mm thick) as the cathode. During the power on period, ethylene was bubbled directly into the flow reactor using a three-way valve, while CO2was bubbled in the solvent bottle. After the reaction was complete, bubbling of ethylene and carbon dioxide was continued until the active halogen was completely consumed. Gas phase analysis showed a Faraday efficiency of 57.5% for vinyl carbonate with a productivity of 0.64 mmol / h.

[0081] Example 10

[0082] A 0.2 M Cs2CO3, 0.5 M KBr and 3 mM K2Cr2O7solution in 30 mL of a DMF-water (3:7 by volume) mixture was used as the electrolyte for the electro-synthesis of vinyl carbonate. Prior to electrolysis, the solution was saturated with CO2bubbling and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). The cell was then powered at a current density of 60 mA / cm2 2The current density was applied at room temperature for 4.33 hours, and the IrO2-DSA anode was the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 49.2%, and its productivity was 1.10 mmol / h.

[0083] Example 11

[0084] 0.2 M Cs₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 100 mA / cm². 2 The current density was applied at room temperature for 2.6 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 46.7%, and its productivity was 1.74 mmol / h.

[0085] Example 12

[0086] 0.2 M Cs₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 150 mA / cm². 2 The current density was such that energizing was performed at room temperature for 1.73 hours, and the IrO2-DSA anode was the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 46.5%, and its productivity was 2.61 mmol / h.

[0087] Example 13

[0088] 0.2 M Cs₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 250 mA / cm². 2 The current density was applied at room temperature for 1.04 h, and the IrO2-DSA anode was the anode (2 cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 46.8%, and its productivity was 4.37 mmol / h.

[0089] Example 14

[0090] 0.2 M Cs₂CO₃, 0.5 M KBr, and 0 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 55.3%, and its productivity was 0.41 mmol / h.

[0091] Example 15

[0092] 0.2 M Cs₂CO₃, 0.5 M KBr, and (1 / 150) M K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 68.6%, and its productivity was 0.51 mmol / h.

[0093] Example 16

[0094] 0.2 M Cs₂CO₃, 0.5 M KBr, and 10 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 63%, and its productivity was 0.47 mmol / h.

[0095] Example 17

[0096] 0.2 M Cs₂CO₃, 0.1 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm².2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 19.6%, and its productivity was 0.15 mmol / h.

[0097] Example 18

[0098] 0.2 M Cs₂CO₃, 0.3 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of ethylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2 The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, ethylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, ethylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of ethylene carbonate was 54.1%, and its productivity was 0.40 mmol / h.

[0099] Example 19

[0100] The stability of the system was tested according to the method in Example 1, with 30 mL of fresh electrolyte replaced after each reaction. The results showed that the Faradaic efficiency of ethylene carbonate remained stable (>75.8%) over 15 cycles exceeding 350 hours. Figure 2 ).

[0101] Example 20

[0102] 0.2 M Cs₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of propylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 20 mA / cm². 2The current density was applied at room temperature for 13 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, propylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, propylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of propylene carbonate was 57.7%, and its productivity was 0.43 mmol / h.

[0103] Example 21

[0104] 0.2 M Cs₂CO₃, 0.5 M KBr, and 3 mM K₂Cr₂O₇ were dissolved in 30 mL of a DMF-water mixture (volume ratio 3:7) as the electrolyte for the electrosynthesis of propylene carbonate. Before electrolysis, the solution was bubbled with CO₂ until saturated, and then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer). Subsequently, the solution was circulated at 100 mA / cm². 2 The current density was applied at room temperature for 2.6 hours, with the IrO2-DSA anode being the anode (2cm). 2 1mm thick), nickel foam cathode (2cm) 2 A cathode (1 mm thick) was used. During energization, propylene was directly bubbled into the diaphragmless flow reactor using a three-way valve, while CO2 was bubbled in a solvent bottle. After the reaction was complete, propylene and carbon dioxide continued to be bubbled until the active halogen was completely consumed, at which point the reaction stopped. Gas phase analysis showed that the Faraday efficiency of propylene carbonate was 45.1%, and its productivity was 1.68 mmol / h.

[0105] Example 22

[0106] 0.2 M Cs₂CO₃, 0.15 M KBr, and 1 mM K₂Cr₂O₇ were dissolved in 20 mL of a mixed solution of DMF and water (volume ratio 3:7) to serve as the electrolyte for the electrosynthesis of styrene cyclic carbonates. IrO₂-DSA was used as the anode (2 cm⁻¹). 2 1mm thick), nickel foam (2cm) 2 The cathode was a 1 mm thick atom. Before electrolysis, CO2 was bubbled until the solution was saturated, and then 1 mmol of allylbenzene was added to the solvent bottle. The solution was then circulated through the flow cell at a flow rate of 10 mL / min using a peristaltic pump (L100-1S-2, Longer) at a flow rate of 5 mA / cm². 2The current density was 0.1 A / dm2 at room temperature until 3 F / mol of electricity was supplied. During the passage of electricity, CO2 was bubbled through the solvent bottle, and the bubbling of carbon dioxide was continued after the end of the reaction until the active halogen was completely consumed. The reaction was stopped. Gas phase analysis gave a yield of 82% of allyl phenyl cyclic carbonate.

[0107] It is to be understood that while the application has been described above with reference to particular embodiments, the application can be implemented differently. It is therefore desired that the present application be limited only by the scope of the appended claims, each example given above is exemplary and not intended to be limiting, and that numerous other modifications and embodiments can be possible.

Claims

1. A method for halogen-mediated diaphragm-free electro-synthesis of cyclic carbonates, characterized in that, The application relates to a method for preparing cyclic carbonates by using a diaphragmless flow reactor to carry out an electrochemical reaction, adding halide salt, carbonate and inorganic passivator as a supporting electrolyte in water and N, N-dimethylformamide solvent, and preparing cyclic carbonates by using olefins and carbon dioxide as raw materials in one pot at room temperature under constant current conditions. The halide salt comprises at least one of potassium chloride, ammonium bromide, potassium bromide, cesium bromide, lithium bromide and potassium iodide. The carbonate comprises at least one of sodium carbonate, potassium carbonate and cesium carbonate. The inorganic passivator comprises at least one of potassium dichromate, potassium molybdate and potassium ferrate. The olefin comprises at least one of gaseous olefin and liquid olefin. The gaseous olefin comprises at least one of ethylene and propylene. The liquid olefin comprises at least one of styrene and allyl benzene. The anode material comprises at least one of iridium dioxide-insoluble anode, platinum, carbon paper and graphite. The cathode material comprises at least one of foamed nickel and nickel sheet. In the supporting electrolyte, the concentration of the halide salt is 0.1-0.5 M, the concentration of the carbonate is 0.1-0.4 M, the concentration of the inorganic passivator is 0-10 mM, and the volume ratio of water to N, N-dimethylformamide is not less than 1:

1.

2. The method of claim 1, wherein, The pH of the supporting electrolyte is 7.5-8.

5. In the supporting electrolyte, the concentration of the halide salt is 0.15-0.5 M, the concentration of the carbonate is 0.2 M, the concentration of the inorganic passivator is (1 / 400)-(1 / 150) M, and the volume ratio of water to N, N-dimethylformamide is (8:2)-(6:4). The current density of the constant current condition is 5-250 mA / cm 2 .

3. The method of claim 2, wherein, The pH of the supporting electrolyte is 8.0-8.

4. In the supporting electrolyte, the concentration of the halide salt is 0.3-0.5 M, the concentration of the inorganic passivator is (1 / 400)-(1 / 150) M, and the volume ratio of water to N, N-dimethylformamide is 7:

3. The current density of the constant current condition is 10-250 mA / cm 2 .

4. The method of claim 3, wherein, The molar ratio of the halide salt to the inorganic passivator is 1:0-200.

5. The method of claim 1, wherein, The molar ratio of the halide salt to the inorganic passivator is 1:50-200.

6. The method of claim 1, wherein, Carbon dioxide is introduced into the supporting electrolyte until saturation, and the supporting electrolyte circulation is started; during the constant current electrolysis, gaseous olefin is introduced into the diaphragmless flow reactor and / or liquid olefin is added, and carbon dioxide is introduced into the supporting electrolyte.

7. The method of claim 1, wherein, After the electrolysis time ends, carbon dioxide is continuously introduced, and gaseous olefin is introduced or not introduced; when the active halogen is completely consumed, the reaction stops, and cyclic carbonates are obtained in one pot.

8. The method according to any one of claims 1-7 in the preparation of cyclic carbonates. ​

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