Method for synthesizing monochloroethylene carbonate

Abstract

The invention provides a method for synthesizing monochloroethylene carbonate. The method provided by the invention is beneficial to improving the utilization rate of raw materials and the reaction efficiency. The method is carried out according to a first scheme or a second scheme, and the first scheme comprises the following steps: (1a) carbon tetrachloride is used as a solvent, chlorine and ethylene carbonate are subjected to a chlorination reaction, and the chlorination reaction is carried out under the condition that feed liquid in a chlorination kettle is in a boiling state; (2a) enabling a gas-phase material flow generated in the chlorination kettle to enter a rectifying tower to be in countercurrent contact with a carbon tetrachloride stream; the scheme II comprises the following steps: (1b) mixing ethylene carbonate and chlorine in a pre-reactor to carry out partial chlorination reaction; (2b) carrying out a chlorination reaction on the pre-reaction feed liquid and supplemented chlorine in a chlorination kettle in the presence of carbon tetrachloride, wherein the chlorination reaction is carried out under the condition that the feed liquid in the chlorination kettle is in a boiling state under a reduced pressure condition; and (3b) enabling a gas-phase material flow generated in the chlorination kettle to enter a rectifying tower to be in countercurrent contact with the carbon tetrachloride flow.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of ethylene chlorocarbonate, and specifically relates to a method for synthesizing ethylene chlorocarbonate. Background Art

[0002] Ethylene chlorocarbonate (CEC) is a key intermediate for synthesizing important additives vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in the electrolyte of lithium-ion batteries. In recent years, the demand for FEC / VC has increased rapidly, providing an important opportunity for the development of CEC.

[0003]

[0004] The industrial synthesis process of CEC mainly obtains it by carrying out a chlorination reaction between ethylene carbonate (EC) and a chlorinating reagent, which is well-known in the industry. For example, the literature disclosed by Newman and Addor in JACS, 1953, P1263 and JACS 1955, P3789. Ethylene carbonate EC undergoes a photocatalytic chlorination reaction under the conditions of 60 - 70 °C and in the presence of a solvent using ultraviolet light irradiation. The obtained ethylene chlorocarbonate CEC is purified by high-vacuum rectification. The photocatalytic chlorination method is the mainstream production process in industry at present. From the reaction mechanism, it belongs to a free radical reaction and requires ultraviolet or visible light to excite Cl2 to generate chlorine radicals. Because the photocatalytic method is environmentally friendly, efficient, and does not introduce other chemical impurities, it is currently the method commonly used in industrial plants at home and abroad.

[0005] In the existing known published literature, such as the process disclosed by Evonik Industries AG in US8022231B2, the reaction conditions are: temperature 40 - 45 °C, reaction time = 7.8 h, reaction results: X = 79.24, Y = 76.6%, S = 96.67, and the content of the reaction liquid product w(CEC) = 80.7%. In this process, the form of N2 bubbling is used to promote the removal of HCl, strengthening the reaction and heat and mass transfer. However, judging from the data given in the examples, the reaction results are still not good and the yield is relatively low.

[0006] The process disclosed by CNOOC Tianjin Chemical Research and Design Institute in "Synthesis Research of Ethylene Chlorocarbonate" uses a kettle reactor with reaction conditions: temperature 80 - 90 °C; reaction time 4 h, and the reaction yield is 82.5%.

[0007] In summary, the yields of existing known CEC synthesis processes are relatively low, and the product cost is high. In addition, the existing domestic CEC industrial plants generally adopt batch processes, and the operation time for each batch is as long as 12 - 20 hours, resulting in low production efficiency. The fundamental reason is that the chlorination reaction is a strongly exothermic reaction, with high requirements for temperature control; moreover, this chlorination reaction is a series reaction, and the monochlorinated product in the reaction solution is prone to undergo deep chlorination reactions to produce dichlorinated or even poly - chlorinated products, reducing the reaction yield.

[0008] CN 112979607 A and CN 116550257 A disclose a process for the photo - chlorination reaction of EC using a micro - channel reactor. The micro - channel reactor itself can significantly improve the heat and mass transfer capabilities of the reaction. However, the micro - channel reactor is currently expensive in cost and has low processing capacity, which limits its application in the industrial field.

[0009] CN 115572279 A discloses a reaction process with forced external circulation heat removal outside the reaction kettle and a Venturi injection structure inside the kettle to strengthen gas - liquid mass transfer, which improves the heat removal capacity of the system. However, the forced external circulation requires a large external power and high energy consumption, and the reaction time still needs 7 - 8 hours, leaving room for improvement.

[0010] In addition, in the existing known batch process for producing CEC by photo - chlorination of EC, the utilization rate of Cl2 is low. Often, the chlorine needs to be in excess by 1.5 - 2 times. A large amount of chlorine in the tail gas needs to be absorbed by NaOH, generating a large amount of sodium hypochlorite waste liquid, which has become one of the persistent problems in the industrial CEC industry. Summary of the Invention

[0011] The present invention provides a method for synthesizing ethylene chlorocarbonate. Using the method of the present invention is conducive to improving the utilization rate of raw materials and reaction efficiency, increasing the yield of the target product, reducing by - product waste liquid, and lowering production costs.

[0012] To achieve its objectives, the present invention provides the following technical solutions:

[0013] The present invention provides a method for synthesizing ethylene chlorocarbonate, and the method is carried out according to Scheme 1 or Scheme 2. Among them, Scheme 1 includes the following steps (1a) - (2a):

[0014] (1a) Using carbon tetrachloride as a solvent, chlorine and ethylene carbonate are subjected to a chlorination reaction in a chlorination kettle, and the chlorination reaction is carried out under reduced pressure so that the liquid in the chlorination kettle is in a boiling state;

[0015] (2a) The gaseous feed stream generated in the chlorination kettle enters a distillation column and contacts a carbon tetrachloride stream in a counter - current manner. After the counter - current contact, the carbon tetrachloride stream enters the reaction system of the chlorination kettle;

[0016] The second solution includes the following steps (1b)-(3b):

[0017] (1b) Under pressurized conditions, ethylene carbonate and chlorine are mixed in a pre-reactor for a partial chlorination reaction to obtain a pre-reaction feed liquid;

[0018] (2b) The pre-reaction feed liquid and the supplementary chlorine are subjected to a chlorination reaction in a chlorination kettle in the presence of carbon tetrachloride, and the chlorination reaction is carried out under reduced pressure conditions to make the feed liquid in the chlorination kettle in a boiling state; wherein, the carbon tetrachloride is added in the pre-reactor in step (1b) and / or in the chlorination kettle in step (2b);

[0019] (3b) The gas-phase feed stream generated in the chlorination kettle enters a distillation column and contacts countercurrently with a carbon tetrachloride stream, and the carbon tetrachloride stream after the countercurrent contact enters the reaction system of the chlorination kettle.

[0020] In some embodiments, in the first solution or the second solution, the reaction pressure in the chlorination kettle is 30-100 kPaA, preferably 50-80 kPaA; the reaction temperature is 40-100 °C, preferably 50-80 °C.

[0021] In some embodiments, in step (2a) of the first solution or step (3b) of the second solution, the gas-phase feed stream after the countercurrent contact is condensed to obtain a liquid phase and a post-condensation gas phase, and the liquid phase is refluxed to the distillation column as the carbon tetrachloride stream for the countercurrent contact;

[0022] Preferably, the post-condensation gas phase is sent to a tail gas absorption tower for treatment and then discharged as tail gas.

[0023] In some embodiments, in the first solution or the second solution, the chlorination reaction is carried out under chemical catalysis or photocatalysis, and the photocatalysis is preferably visible light and / or ultraviolet light, more preferably ultraviolet light.

[0024] In some embodiments, in the second solution, the reaction pressure in step (1b) is 0.3-2 MPaA; the reaction temperature is 40-100 °C, preferably 50-80 °C, and further preferably 50-70 °C.

[0025] In some embodiments, in the second solution, in step (1b), the conversion rate of ethylene carbonate is controlled to be <40%, preferably <30%, more preferably <20%, and preferably ≥10%.

[0026] In some embodiments, in the second solution, the partial chlorination reaction is carried out in one pre-reactor or a plurality of pre-reactors connected in series;

[0027] Each of the pre-reactors is connected to a gas-liquid separation tank respectively. The reaction feed liquid output from the pre-reactor is sent into the gas-liquid separation tank for gas-liquid separation, and a liquid-phase product and a gas-phase product are obtained.

[0028] When the partial chlorination reaction is carried out in one pre-reactor, the liquid-phase product separated from the reaction feed liquid output from the pre-reactor by the gas-liquid separation tank is used as the pre-reaction feed liquid and sent into the chlorination kettle in step (2b).

[0029] When the partial chlorination reaction is carried out in multiple serially-connected pre-reactors, the liquid-phase product separated from the reaction feed liquid output from the upper-stage pre-reactor by the gas-liquid separation tank is sent into the lower-stage pre-reactor for continuous reaction. The liquid-phase product separated from the reaction feed liquid output from the last-stage pre-reactor by the gas-liquid separation tank is used as the pre-reaction feed liquid and sent into the chlorination kettle in step (2b). Preferably, chlorine gas is introduced into each pre-reactor.

[0030] Preferably, the gas-phase product separated in the gas-liquid separation tank is sent into a tail gas absorption tower for treatment and then discharged as tail gas.

[0031] Preferably, the pre-reactor is a kettle-type, tower-type or tube-type reactor, and preferably a tube-type reactor.

[0032] In some embodiments, in the second solution, when the partial chlorination reaction is carried out in multiple serially-connected pre-reactors, the reaction pressure of the upper-stage pre-reactor is equal to or higher than that of the lower-stage pre-reactor. Preferably, the reaction temperature of the upper-stage pre-reactor is higher than that of the lower-stage pre-reactor.

[0033] Preferably, the reaction pressure of each pre-reactor is higher than the pressure of the gas-liquid separation tank used to separate the reaction feed liquid of the corresponding pre-reactor.

[0034] In some embodiments, in the first solution, the liquid-phase residence time in the chlorination reaction is 0.8 - 4 h.

[0035] In the second solution, the total sum of the liquid-phase residence times for carrying out the chlorination reaction in each step is 0.8 - 4 h, such as 1 - 4 h.

[0036] In some embodiments, in the first or second solution, the operating conditions of the distillation column include:

[0037] The column bottom pressure is 30 - 100 kPaA, the column bottom temperature is 30 - 90 °C, and the reflux ratio is total liquid reflux.

[0038] In some embodiments, in the first or second solution, the molar ratio of the total amount of ethylene carbonate used to the total amount of chlorine gas used is 1:1.05 to 1.50, and the mass ratio of the total amount of ethylene carbonate used to the total amount of carbon tetrachloride used is 1:1 to 10;

[0039] Preferably, in the second solution, in step (1b), the molar ratio of the amount of chlorine gas introduced into each pre-reactor to the total amount of ethylene carbonate used is 0.105 to 0.42:1; in step (2b), the molar ratio of the additional chlorine gas to the total amount of ethylene carbonate used is 0.90 to 0.58:1.

[0040] The technical solution provided by the present invention has the following beneficial effects:

[0041] Using the method of the present invention to prepare chloroethyl carbonate can solve the problems existing in the existing batch reaction process, such as poor heat transfer capacity, poor temperature control effect, low reaction efficiency and yield, high chlorine content in the tail gas, and a large amount of by-product waste liquid. The present invention proposes an improved new process that is easy to industrialize, which can improve efficiency, reduce by-products, and lower production costs. The method disclosed by the present invention can significantly improve the heat transfer capacity of the system, reduce the residence time of the product in the system, increase the reaction rate, reduce side reactions, and significantly reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Shown is a schematic process flow diagram in one embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To facilitate the understanding of the present invention, the present invention will be further described below in conjunction with embodiments. It should be understood that the following embodiments are only for better understanding of the present invention, and do not mean that the present invention is limited only to the following embodiments.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The term "and / or" as used herein may include any and all combinations of one or more of the related listed items.

[0045] The present invention provides a method for synthesizing chloroethyl carbonate, and the method is carried out according to the first or second solution, wherein the first solution includes the following steps (1a)-(2a):

[0046] (1a) Using carbon tetrachloride as a solvent, chlorine gas and ethylene carbonate are subjected to a chlorination reaction in a chlorination kettle, and the chlorination reaction is carried out under reduced pressure so that the liquid in the chlorination kettle is in a boiling state;

[0047] (2a) The gaseous feed stream generated in the chlorination kettle enters the distillation column and contacts the carbon tetrachloride stream in a countercurrent manner. After the countercurrent contact, the carbon tetrachloride stream enters the reaction system of the chlorination kettle.

[0048] The second solution includes the following steps (1b)-(3b):

[0049] (1b) Under pressurized conditions, ethylene carbonate and chlorine are mixed in a pre-reactor to undergo a partial chlorination reaction to obtain a pre-reaction feed liquid;

[0050] (2b) The pre-reaction feed liquid and the supplemented chlorine are subjected to a chlorination reaction in the chlorination kettle in the presence of carbon tetrachloride, and the chlorination reaction is carried out under reduced pressure to keep the liquid in the chlorination kettle in a boiling state; wherein, the carbon tetrachloride is added to the reaction system in the pre-reactor in step (1b) and / or in the chlorination kettle in step (2b);

[0051] (3b) The gaseous feed stream generated in the chlorination kettle enters the distillation column and contacts the carbon tetrachloride stream in a countercurrent manner. After the countercurrent contact, the carbon tetrachloride stream enters the reaction system of the chlorination kettle.

[0052] In the method of the present invention, carbon tetrachloride is used as a solvent, and the chlorination reaction process is carried out under reduced pressure in the chlorination kettle to keep the liquid in a boiling state. The reaction heat is absorbed by the phase change heat of the carbon tetrachloride solvent. At the same time, the HCl gas generated by the chlorination reaction can be removed more thoroughly, which promotes the reaction to occur faster, reduces the residence time of the product in the system, is conducive to reducing the acidity of the system and reducing side reactions; at the same time, using carbon tetrachloride as a solvent has a high solubility for chlorine, and through the chlorination reaction carried out under the boiling state under reduced pressure, carbon tetrachloride vaporizes and enters the distillation column, and after condensation, it flows back into the distillation column and contacts the gaseous feed stream generated by the chlorination kettle in the distillation column in a countercurrent manner, which can efficiently capture the chlorine in the gaseous feed stream, so that the chlorine finally returns to the reaction system of the chlorination kettle for further utilization; the process of the present invention not only improves the utilization rate of raw materials, but also reduces the content of chlorine in the tail gas, and is conducive to reducing the excess ratio of chlorine in the chlorine feed. Using the method of the present invention is conducive to improving the utilization rate of raw materials and the reaction efficiency, is conducive to increasing the yield of the target product, reducing the by-product waste liquid and reducing the production cost.

[0053] The present invention more preferably adopts the second solution. Compared with the first solution, a pre-reaction is carried out in the pre-reactor before the main reaction to undergo partial conversion, and then the main reaction is carried out in the chlorination kettle, which is conducive to further improving the reaction efficiency, shortening the liquid phase residence time, and is conducive to further significantly reducing the production cost.

[0054] The method provided by the present invention uses carbon tetrachloride as a solvent and adopts a solvent reactive distillation process. The chlorination reaction occurs under the boiling state of the solvent, which strengthens the heat and mass transfer performance. The vaporized solvent is condensed and then recycled, and Cl2 in the gaseous feed stream generated by the reaction is trapped in the distillation column, which is conducive to significantly improving the yield and reducing the by-product waste liquid.

[0055] In the present invention, CEC is prepared with carbon tetrachloride as a solvent through the new process of the present invention. In the process of the present invention, the main reaction is carried out under a reduced-pressure boiling state, and the carbon tetrachloride vaporized and then condensed by reflux is used to trap chlorine gas. The carbon tetrachloride solvent can play the roles of a light stabilizer and a reaction promoter, achieving the effects of promoting the reaction rate and increasing the reaction yield. In the process of the present invention, carbon tetrachloride can play a dual role of a free radical stabilizer and increasing the solubility of Cl2 in the liquid phase.

[0056] Since the exotherm of the chlorination reaction is intense, the ability of the system to remove the reaction heat is very crucial. In the traditional process, there are various problems with using kettle-type, tower-type reactors with forced circulation, microchannel reactors, etc., which are not conducive to large-scale industrial applications. The inventor of the present invention found that by preparing CEC with carbon tetrachloride as a solvent under a reduced-pressure boiling state, the reaction heat can be effectively removed through the gas-liquid phase change. By controlling the reaction system to carry out at the bubble point temperature and boiling state, the reaction heat is absorbed by the phase change heat of the solvent, thereby achieving a better effect of removing heat and controlling the temperature. The process disclosed in the present invention enables the solvent uniformly distributed in the entire liquid phase system to fully play its role, with a larger and more uniform heat transfer area, and better heat removal and temperature control effects. At the same time, maintaining the boiling state of the system is also of great significance for controlling the acidity of the liquid phase system. It can more thoroughly remove the HCl gas generated by the chlorination reaction, promoting the reaction to occur faster; it can also reduce the acidity of the system, and the system acidity is one of the key factors inducing side reactions. By adopting the process disclosed in the present invention, the content of HCl in the liquid phase can be effectively controlled, further increasing the reaction rate, reducing side reactions, and increasing the reaction yield. In some embodiments, in the first or second solution, the reaction pressure in the chlorination kettle is 30 - 100 kPaA, such as 30 kPaA, 40 kPaA, 50 kPaA, 60 kPaA, 70 kPaA, 80 kPaA, 90 kPaA, 100 kPaA, etc., preferably 50 - 80 kPaA; the reaction temperature is 40 - 100 °C, such as 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, etc., more preferably the reaction temperature is 50 - 80 °C, and further preferably 50 - 70 °C; under the above reaction temperature, reaction pressure and other conditions, especially in combination with the above more preferred reaction temperature conditions, it is conducive to achieving a better effect of removing heat and controlling the temperature, further significantly increasing the reaction rate, significantly shortening the reaction time, and inhibiting side reactions.

[0057] In some preferred embodiments, in Scheme 1 or Scheme 2, the reaction pressure of the chlorination kettle is controlled to be 30-100 kPaA, preferably 50-80 kPaA, and at the same time, the reaction temperature is controlled to be 50-80 °C. Compared with a higher reaction temperature, it can balance a shorter liquid-phase residence time and a better reaction effect, which is conducive to further significantly improving the product purity and yield.

[0058] The chlorination reaction carried out in the chlorination kettle of Scheme 1 and Scheme 2 is carried out under a pressure lower than atmospheric pressure, preferably 30-100 kPaA, more preferably 50-80 kPaA, and this pressure requirement is maintained during the reaction process; on the one hand, the reaction pressure adopted belongs to an easily achievable pressure condition, and on the other hand, by reducing the pressure to this low enough range, it is conducive to the significant gasification of the solvent carbon tetrachloride, thereby promoting a large amount of HCl to enter the gas phase and leave the liquid-phase reaction system, which is conducive to further improving the reaction selectivity and further increasing the yield, and is significantly beneficial and economical for reducing costs.

[0059] Furthermore, in step (2a) of Scheme 1 or step (3b) of Scheme 2, after the countercurrent contact, the gas-phase material flow is condensed to obtain a liquid phase and a condensed gas phase. The liquid phase is refluxed to the distillation column as the carbon tetrachloride stream for the countercurrent contact. Specifically, the condensed gas phase is sent to a tail gas absorption tower for treatment and then discharged as tail gas. Specifically, the tail gas absorption tower can use, for example, NaOH as the tail gas absorbent.

[0060] In some embodiments, in Scheme 1 or Scheme 2, the chlorination reaction is carried out under chemical catalysis or photocatalysis, preferably under photocatalysis. The photocatalysis is preferably visible light and / or ultraviolet light, more preferably ultraviolet light.

[0061] In the preferred embodiment, in the second solution, in step (1b), the reaction pressure is 0.3 to 2 MPaA, such as 0.3 MPaA, 0.5 MPaA, 1 MPaA, 1.5 MPaA, 2 MPaA, etc.; the reaction temperature is 40 - 100 °C, such as 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, etc., and preferably 50 - 80 °C. In the present invention, in the pre-reaction of the second solution, making the chlorination reaction pressure higher than atmospheric pressure is beneficial to increasing the solubility of Cl2 in the liquid phase, and helps to improve the reaction rate and shorten the residence time. However, because the contributions of Cl2 and HCl in the system to the main and side reactions are different, and HCl is a product of the system, its rapid removal from the liquid-phase reaction system is of great significance for improving the reaction rate and yield. The selection of the reaction pressure must maintain a high solubility of Cl2 in the liquid phase while not affecting the removal of HCl from the liquid-phase system. The researchers of the present invention found that in the carbon tetrachloride solvent reaction system disclosed in the present invention, the pressurized reaction is preferably carried out at 0.3 - 2 MPaA to achieve more satisfactory results, which is beneficial to taking into account the high solubility of Cl2 and the better removal effect of HCl, and improving the reaction effect.

[0062] In the preferred embodiment, in the second solution, in step (1b), the conversion rate of ethylene carbonate is controlled to be < 40%, such as 10%, 13%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, 36% or 39%, etc., preferably < 30%, more preferably < 20%, preferably ≥ 10%, for example 10 - 15%.

[0063] In some preferred embodiments, in step (1b) of the second solution, the reaction pressure is controlled to be 0.3 - 2 MPaA; the reaction temperature is 40 - 100 °C, preferably 50 - 80 °C; at the same time, the conversion rate of ethylene carbonate is controlled to be < 40%, preferably < 30%, more preferably < 20%, preferably ≥ 10%, for example 10 - 15%; under the preferred reaction conditions, it is beneficial to better balance the higher reaction efficiency and good selectivity of the target product. For example, the mass ratio of CEC and DCEC in the reaction solution of the pre-reactor is higher than 99:1, preferably higher than 99.5:0.5 under the preferred conditions, and more preferably higher than 99.8:0.2 under the more preferred conditions.

[0064] In some preferred embodiments, in step (1b) of the second solution, the reaction pressure is controlled to be 0.3 - 2 MPaA, the reaction temperature is 50 - 80 °C, and at the same time, the total conversion rate of ethylene carbonate in step (1b) is controlled to be < 30% and ≥ 10%; in step (2b), the reaction pressure in the chlorination kettle is controlled to be 30 - 100 kPaA, preferably 50 - 80 kPaA, and at the same time, the reaction temperature is controlled to be 50 - 80 °C; a higher product purity and yield can be obtained at a relatively low chlorine excess ratio, while taking into account a relatively high reaction efficiency.

[0065] In a further preferred embodiment, in step (1b) of Scheme 2, the reaction pressure is controlled to be 0.3 - 2 MPaA, the reaction temperature is 50 - 70 °C, and at the same time, the total conversion rate of ethylene carbonate in step (1b) is controlled to be < 20% and ≥ 10%; in step (2b), the reaction pressure of the chlorination kettle is controlled to be 30 - 100 kPaA, preferably 50 - 80 kPaA, and at the same time, the reaction temperature is controlled to be 50 - 80 °C; the total liquid-phase residence time is 1 - 4 h; better reaction effects can be obtained, higher product purity and yield can be obtained, and relatively high reaction efficiency can be taken into account at the same time.

[0066] In some embodiments, in the said Scheme 2, the partial chlorination reaction is carried out in a pre-reactor or a plurality of pre-reactors connected in series with each other;

[0067] Each of the said pre-reactors is respectively connected to a gas-liquid separation tank, and the reaction feed liquid output from the pre-reactor is sent into the gas-liquid separation tank for gas-liquid separation, and a liquid-phase product and a gas-phase product are obtained;

[0068] When the partial chlorination reaction is carried out in a pre-reactor, the liquid-phase product separated from the reaction feed liquid output from the gas-liquid separation tank to the pre-reactor is used as the pre-reaction feed liquid and sent into the chlorination kettle of step (2b);

[0069] When the partial chlorination reaction is carried out in a plurality of pre-reactors connected in series with each other, the liquid-phase product separated from the reaction feed liquid output from the gas-liquid separation tank to the upper-stage pre-reactor is sent into the lower-stage pre-reactor for continuous reaction, and the liquid-phase product separated from the reaction feed liquid output from the gas-liquid separation tank to the last-stage pre-reactor is used as the pre-reaction feed liquid and sent into the chlorination kettle of step (2b). Preferably, chlorine gas is introduced into each pre-reactor, that is, each pre-reactor includes a mixing process of newly introduced chlorine gas and the feed liquid.

[0070] The "upper-stage pre-reactor", "lower-stage pre-reactor" and "last-stage pre-reactor" mentioned in the text are in terms of the flow direction of the reaction feed liquid. For example, the reactor located upstream is called the upper-stage pre-reactor, and the reactor located downstream is called the lower-stage pre-reactor.

[0071] Preferably, the gas-phase product separated in the gas-liquid separation tank is sent into a tail gas absorption tower for treatment and then discharged as tail gas. Specifically, the tail gas absorption tower can use NaOH as the tail gas absorbent, and mainly removes HCl and a small amount of unreacted Cl2 in the gas-phase product through the tail gas absorption tower.

[0072] For consecutive reactions such as EC / CEC and thermosensitive systems, in order to further reduce side reactions and improve product yield, the present inventor further improves the reaction efficiency and reduces the liquid phase residence time by means of process intensification. After actual comparison and separation of various routes, the present inventor found that the scheme of adding a pre-reaction process before the main chlorination reactor (i.e., adopting the second scheme of the present invention) can better achieve the above object. At a faster reaction rate, the system needs to provide stronger heat transfer and mass transfer capabilities. The reactor form of the pre-reaction process can be a kettle-type, tower-type, or tubular reactor, preferably a tubular reactor; more preferably, a microchannel reactor is used. The pre-reactor is arranged before the main chlorination reactor, corresponding to the initial stage of the chlorination reaction. In this stage, for a typical consecutive reaction such as chlorination, the dichlorination and polychlorination reactions are based on the monochlorination product, and the initial stage of the reaction is mainly the monochlorination reaction stage. By using the essence of the reaction for process intensification, the reaction rate is increased, the residence time is shortened, and at the same time, significant side reactions are avoided. Preferably, the reaction pressure of the pre-reaction is controlled to be 0.3-2 MPaA; the reaction temperature is 40-100 °C, preferably 50-80 °C, to obtain a higher reaction rate and further shorten the residence time. In some embodiments, in each stage of the pre-reactor in step (1b), the residence time is about 1-10 min.

[0073] Preferably, in the second solution, when the partial chlorination reaction is carried out in multiple pre-reactors connected in series, the reaction pressure of the upper-stage pre-reactor is equal to or higher than (preferably higher than) the reaction pressure of the lower-stage pre-reactor; preferably, the reaction pressure of each stage of the pre-reactor is higher than the pressure of the gas-liquid separation tank used to separate the reaction feed liquid of the corresponding pre-reactor. The reaction feed liquid is depressurized and gas-liquid separated in the gas-liquid separation tank, and the separated liquid-phase product enters the lower-stage pre-reactor to continue the chlorination reaction under lower pressure conditions. Using the preferred pressure requirements for the pre-reaction is beneficial to further improve the reaction effect and engineering practice. Preferably, in the second solution with two or more stages of pre-reactors, the pressure of the lower-stage pre-reactor is less than that of the upper-stage pre-reactor; each stage of the pre-reactor is connected to a gas-liquid separation tank, the liquid-phase product is sent to the lower-stage reactor, and the separated gas-phase product is sent to the tail gas absorption tower; the pressures of each stage of the pre-reactor and the downstream gas-liquid separation tank are of great significance to the reaction effect. Each stage of the pre-reactor reacts under pressure, and the increased pressure not only increases the solubility of chlorine gas in the liquid phase but also is beneficial to increasing the reaction rate. However, at the same time, the pressure relationship between each stage of the pre-reactor and between the pre-reactor and the gas-liquid separation tank, that is, the pressure of the lower-stage pre-reactor is lower than that of the upper-stage pre-reactor, and the reaction pressure of each stage of the pre-reactor is higher than the pressure of the gas-liquid separation tank used to separate the reaction feed liquid of the corresponding pre-reactor. The reduced pressure is beneficial to the faster removal of the reaction product HCl and reduces the acidity of the liquid-phase system to reduce side reactions. Therefore, it is preferred that the pressures of the gas-liquid separation tanks of the multi-stage pre-reactors decrease gradually to better balance the requirements of the reaction and degassing. Preferably, the reaction temperature of the upper-stage pre-reactor is higher than that of the lower-stage pre-reactor, which is beneficial to obtaining a better reaction effect.

[0074] In some embodiments, in the first solution, the liquid-phase residence time in the chlorination reaction is 0.8 - 4 h, such as 0.8 h, 1 h, 2 h, 3 h, 4 h, etc.; in the second solution, the total liquid-phase residence time for carrying out the chlorination reaction in each step is 0.8 - 4 h, such as 0.8 h, 0.9 h, 1 h, 2 h, 3 h, 4 h, for example 1 - 4 h.

[0075] In some embodiments, in the first solution or the second solution, the operating conditions of the distillation column include: the column bottom pressure is 30 - 100 kPaA, the column bottom temperature is 30 - 90 °C, the reflux ratio is total liquid reflux, and the gas phase is sent to the tail gas absorption tower.

[0076] In some embodiments, in the first or second solution, the molar ratio of the total amount of ethylene carbonate used to the total amount of chlorine gas used is 1:1.05 to 1.50, such as 1:1.05, 1:1.10, 1:1.15, 1:1.25, 1:1.35, 1:1.45, 1:1.50, etc.; the mass ratio of the total amount of ethylene carbonate used to the total amount of carbon tetrachloride used is 1:1 to 10, such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0077] Preferably, in the second solution, in step (1b), the molar ratio of the amount of chlorine gas introduced into each pre-reactor to the total amount of ethylene carbonate used is 0.105 to 0.42:1; in step (2b), the molar ratio of the supplementary chlorine gas to the total amount of ethylene carbonate used is 0.90 to 0.58:1.

[0078] The new process provided by the present invention using carbon tetrachloride as a light stabilizer and solvent is also of great significance for improving the utilization rate of Cl2, reducing the content of chlorine gas in the tail gas, and reducing by-products. The new process disclosed in the present invention carefully designs a reaction process with carbon tetrachloride solvent, which can significantly reduce the content of chlorine gas in the tail gas. In the first or second solution, the gas-phase stream obtained from the chlorination kettle is sent to a distillation column to remove carbon tetrachloride, and the carbon tetrachloride stream flowing back inside the distillation column and the gas-phase stream from the chlorination kettle run countercurrently. After screening and comparison, carbon tetrachloride not only has the effect of a light stabilizer to accelerate the photochlorination reaction and improve the efficiency, but also has a high solubility for chlorine gas. Through the aforementioned operation, the carbon tetrachloride liquid-phase stream contacts the chlorine gas in the gas phase countercurrently in the distillation column, and can efficiently capture the chlorine gas in the gas phase and finally return to the reaction system for further utilization. This not only improves the utilization rate of raw materials, but also reduces the content of chlorine gas in the tail gas. The Cl2 / HCl molar ratio in the tail gas < 5%, and at the same time, it is beneficial to reduce the chlorine excess ratio, for example, it can be reduced to less than 5%, and the utilization rate of raw materials is greatly improved. At the same time, the reduction of the chlorine content in the tail gas can also significantly reduce the dosage of the tail gas absorbent NaOH and reduce the amount of sodium hypochlorite waste liquid, having many advantages.

[0079] The chlorinated ethylene carbonate product prepared by the method of the present invention can be used to prepare vinylene carbonate VC and fluoroethylene carbonate FEC, and further used as an additive for high-performance lithium battery electrolytes.

[0080] In the text, the pressures are all absolute pressures.

[0081] In the text, unless otherwise specified, the % are all wt%.

[0082] The method of the present invention is used to prepare ethylene carbonate monochloride, which can solve the problems existing in the existing batch reaction process, such as poor heat transfer capacity, poor temperature control effect, low reaction efficiency and yield, high chlorine content in the tail gas, and a large amount of by-product waste liquid. The present invention proposes an improved new process that is easy to realize industrially, which can improve efficiency, reduce by-products, and lower production costs. The method disclosed in the present invention can significantly improve the heat removal capacity of the system, reduce the residence time of the product in the system, increase the reaction rate, reduce side reactions, and significantly reduce production costs.

[0083] The new process for preparing CEC provided by the present invention using carbon tetrachloride as a light stabilizer and solvent can significantly reduce side reactions and production costs compared with the currently known mainstream industrial technologies, and has outstanding economic advantages.

[0084] The following further illustrates the solution of the present invention with reference to embodiments, but the present invention is not limited thereto.

[0085] For the parts not specifying the specific experimental steps or conditions in the embodiments, the operations or conditions of the corresponding conventional experimental steps in the technical field can be followed. For the reagents or instruments not indicating the manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0086] Raw material information: The ethylene carbonate (EC) and Cl2 raw materials used in the embodiments of the present invention are produced by the Yantai Industrial Park device of Wanhua Chemical.

[0087] Pressurized photocatalytic reactor: Peshel reactor;

[0088] Tube-type photocatalytic reactor: Tianjin Caelus Co., Ltd.

[0089] Microchannel photocatalyst reactor: Corning G1 type microchannel reactor.

[0090] Some embodiments use Figure 1 the shown process flow and device to prepare ethylene carbonate monochloride. Figure 1The described process system includes a pre-reactor 1, a pre-reactor 2, a gas-liquid separation tank 3, and a gas-liquid separation tank 4. It also includes a chlorination kettle, a distillation column, and a tail gas absorption tower. The distillation column is equipped with a buffer tank and a condenser. In the pre-reactor 1, partial chlorination reaction of EC and chlorine is carried out in the presence of optional carbon tetrachloride. The resulting reaction liquid enters the gas-liquid separation tank 3 for gas-liquid separation. The separated gas-phase product enters the tail gas absorption tower for treatment, and the separated liquid-phase product enters the pre-reactor 2 to continue the partial chlorination reaction with the introduced chlorine. The reaction liquid obtained in the pre-reactor 2 enters the gas-liquid separation tank 4 for gas-liquid separation. The separated gas-phase product enters the tail gas absorption tower for treatment, and the separated liquid-phase product enters the chlorination kettle to continue the chlorination reaction with the introduced chlorine in the presence of a carbon tetrachloride solvent. The gas-phase stream generated in the chlorination kettle enters the distillation column and contacts the carbon tetrachloride stream in countercurrent, thereby absorbing the chlorine in the gas-phase stream. After the countercurrent contact, the carbon tetrachloride stream carrying the absorbed chlorine returns to the reaction system of the chlorination kettle. The gas-phase stream after the countercurrent contact is condensed by the condenser and enters the buffer tank. The condensed liquid phase is returned to the distillation column as a carbon tetrachloride stream to continue the countercurrent contact with the gas-phase stream, while the condensed gas phase enters the tail gas absorption tower for treatment, specifically using NaOH as the absorbent. The chlorination kettle and the pre-reactors 1 and 2 are all equipped with ultraviolet light sources.

[0091] Example 1 (Scheme 1)

[0092] Refer to Figure 1 the described process flow and device, except that there are no pre-reactor 1, pre-reactor 2, and the corresponding gas-liquid separation tank 3 and gas-liquid separation tank 4. The used chlorination kettle is a pressurized photocatalytic reaction kettle from Peshel Company, with a volume of 1 L and an ultraviolet light source power of 500 w. A reaction distillation column connected to the chlorination kettle is provided at the top of the chlorination kettle, with a column diameter of 30 mm. The upper part of the reaction distillation column is filled with 3*3 mm glass spring packing with a height of 1 m.

[0093] Operating conditions: EC and carbon tetrachloride are fed into the chlorination kettle according to a mass ratio of 1:1. The EC and carbon tetrachloride in the chlorination kettle are heated to 60 °C. The vacuum pump is adjusted until the liquid system in the chlorination kettle starts to boil, and then chlorine is introduced. The molar ratio of EC to chlorine is 1:1.2. The liquid residence time is calculated as 2.5 h based on the liquid holdup volume in the kettle / EC feed volume flow rate. The ultraviolet light source is turned on and the light source power is gradually increased to 500 w, while the system pressure is adjusted to maintain the temperature in the kettle stable at 60 °C. After the system is stable, the top pressure of the reaction distillation column is 50 kPaA, the top temperature is 45 °C, the bottom pressure is 52 kPaA (the same as the pressure in the chlorination kettle), and the bottom temperature is 60 °C. The liquid phase at the top of the distillation column (mainly carbon tetrachloride) is under total reflux operation, and the gas phase is sent to the NaOH absorption tank (i.e., the tail gas absorption tower) for absorption and then discharged. Continuous feeding is carried out, and after the system is stable, it continues to operate for 6 hours, and the sample is sent for GC analysis.

[0094] Reaction results: The GC purity of the CEC product is 92%, the GC normalization ratio of CEC and DCEC is 99.0:1.0, the total reaction yield is 91.2%, and the Cl2 / HCl molar ratio in the tail gas discharged from the absorption tower (mainly HCl and unreacted Cl2) is <5%, much lower than 30 - 50% of the traditional batch process technology, significantly improving the utilization rate of Cl2.

[0095] Example 2 (Scheme 1)

[0096] Adopt the Figure 1 process flow and device as described, and the equipment is the same as that in Example 1.

[0097] Operating conditions:

[0098] Other conditions are the same as those in Example 1. The following only describes the differences from Example 1:

[0099] The temperature of EC and carbon tetrachloride in the chlorination kettle is raised to 100 °C, the vacuum pump is adjusted until the liquid material system in the chlorination kettle starts to boil, and then chlorine gas is introduced; the liquid phase residence time is 0.8 h. After the system is stable, the pressure at the top of the reactive distillation column is 55 kPaA, the temperature at the top of the column is 40 °C, the pressure at the bottom of the column is 58 kPaA, and the temperature at the bottom of the column (i.e., the temperature of the chlorination kettle) is 100 °C. The liquid phase at the top of the distillation column is operated under total reflux. Continuous feeding is carried out, and after the system is stable, it continues to run for 6 hours, and the sample is sent for GC analysis.

[0100] Reaction results: The GC purity of the CEC product is 90%, the GC normalization ratio of CEC and DCEC is 99:1, the total reaction yield is 89.8%, and the Cl2 / HCl molar ratio in the tail gas discharged from the absorption tower (mainly HCl and unreacted Cl2) is <5%.

[0101] Example 3 (Scheme 2)

[0102] Adopt the Figure 1 process flow and device as described. Other equipment is the same as that in Example 1. Two-stage pre-reactors 1 and 2, and two gas-liquid separation tanks 3 and 4 are added. The pre-reactor adopts a quartz tube reactor from Tianjin Kelaiying Co., Ltd., with a pipe diameter of 8 mm.

[0103] Operating conditions:

[0104] The temperature of the pre-reactor 1 is 100 °C, the pressure is 2 MPaA, the liquid-phase residence time is 5 min, the molar ratio of EC to Cl2 is 1:0.2, the mass ratio of EC to carbon tetrachloride is 1:1, and the power of the ultraviolet light source is 100 w; the pressure of the gas-liquid separation tank 3 is 1.5 MPaA. The reaction feed liquid obtained in the pre-reactor 1 enters the gas-liquid separation tank 3 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the pre-reactor 2.

[0105] The temperature of the pre-reactor 2 is 90 °C, the pressure is 1 MPaA, the liquid-phase residence time is 5 min, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the pre-reactor 2 is 1:0.2, and the power of the ultraviolet light source is 100 w; the pressure of the gas-liquid separation tank 4 is 0.5 MPaA. The reaction feed liquid obtained in the pre-reactor 2 enters the gas-liquid separation tank 4 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the chlorination kettle. In the pre-reactor 1 and the pre-reactor 2, the total conversion rate of ethylene carbonate is 39%.

[0106] The conditions in the chlorination kettle and the reactive distillation column are basically the same as those in Example 1, except that: the liquid-phase residence time in the chlorination kettle is 1 h, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the chlorination kettle is 1:0.8, and the power of the ultraviolet light source is 300 w. After the system is stable, it continues to run for 6 hours, and the sample is sent for GC analysis.

[0107] Reaction results: The GC purity of the CEC product is 87%, the GC normalization ratio of CEC to DCEC is 98.8:1.2, the total reaction yield is 87.0%, and the Cl2 / HCl molar ratio in the tail gas discharged from the absorption tower is <5%.

[0108] Example 4 (Scheme II)

[0109] Adopt the Figure 1 process flow and device as described, other equipment is the same as that in Example 1, and two-stage pre-reactors 1 and 2, as well as two gas-liquid separation tanks 3 and 4 are added. The pre-reactor adopts a quartz tube reactor from Tianjin Kelaiying Co., Ltd., with a pipe diameter of 8 mm.

[0110] Operating conditions:

[0111] The temperature of the pre-reactor 1 is 80 °C, the pressure is 1.6 MPaA, the liquid-phase residence time is 10 min, the molar ratio of EC to Cl2 is 1:0.15, the mass ratio of EC to carbon tetrachloride is 1:1, and the power of the ultraviolet light source is 75 w; the pressure of the gas-liquid separation tank 3 is 1.2 MPaA. The reaction feed liquid obtained in the pre-reactor 1 enters the gas-liquid separation tank 3 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the pre-reactor 2.

[0112] The temperature of the pre-reactor 2 is 60 °C, the pressure is 0.8 MPaA, the liquid-phase residence time is 10 min, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the pre-reactor 2 is 1:0.15, the power of the ultraviolet light source is 75 w, and the pressure of the gas-liquid separation tank 4 is 0.4 MPaA. The reaction feed liquid obtained from the pre-reactor 2 enters the gas-liquid separation tank 4 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the chlorination kettle. In the pre-reactor 1 and the pre-reactor 2, the total conversion rate of ethylene carbonate is 29.5%.

[0113] The conditions in the chlorination kettle and the reactive distillation column are basically the same as those in Example 1, except that: the liquid-phase residence time in the chlorination kettle is 0.8 h, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the chlorination kettle is 1:0.75, and the power of the ultraviolet light source is 350 w. After the system is stable, it continues to run for 6 hours, and the sample is sent for GC analysis.

[0114] Reaction results: The GC purity of the CEC product is 91.1%, the GC normalization ratio of CEC and DCEC is 99.1:0.9, the total reaction yield is 90.5%, and the Cl2 / HCl molar ratio in the tail gas discharged from the absorption tower is <5%.

[0115] Example 5 (Scheme 2)

[0116] Adopt the process flow and device as attached Figure 1 described, other equipment is the same as that in Example 1, and two-stage pre-reactors 1 and 2, as well as two gas-liquid separation tanks 3 and 4 are added. The pre-reactor adopts a quartz tube reactor from Tianjin Kelaiying Co., Ltd., with a pipe diameter of 8 mm.

[0117] Operating conditions:

[0118] The temperature of the pre-reactor 1 is 70 °C, the pressure is 1.4 MPaA, the liquid-phase residence time is 15 min, the molar ratio of EC to Cl2 is 1:0.10, the mass ratio of EC to carbon tetrachloride is 1:1, the power of the ultraviolet light source is 50 w; the pressure of the gas-liquid separation tank 3 is 1.0 MPaA. The reaction feed liquid obtained from the pre-reactor 1 enters the gas-liquid separation tank 3 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the pre-reactor 2.

[0119] The temperature of the pre-reactor 2 is 50 °C, the pressure is 0.6 MPaA, the liquid-phase residence time is 15 min, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the pre-reactor 2 is 1:0.10, the power of the ultraviolet light source is 50 w, and the pressure of the gas-liquid separation tank 4 is 0.3 MPaA. The reaction feed liquid obtained from the pre-reactor 2 enters the gas-liquid separation tank 4 for gas-liquid separation. The gas-phase product enters the tail gas absorption tower for treatment, and the liquid-phase product enters the chlorination kettle. In the pre-reactor 1 and the pre-reactor 2, the total conversion rate of ethylene carbonate is 19.4%.

[0120] The conditions in the chlorination kettle and the reactive distillation column are basically the same as those in Example 1, except that: the liquid-phase residence time in the chlorination kettle is 1.5 h, the molar ratio of EC introduced into the pre-reactor 1 to Cl2 introduced into the chlorination kettle is 1:0.9, and the power of the ultraviolet light source is 400 w. After the system is stable, continue to operate for 6 hours, and take samples for GC analysis.

[0121] Reaction results: The GC purity of the CEC product is 92.8%, the GC normalization ratio of CEC and DCEC is 99.6:0.4, the total reaction yield is 91.5%, and the Cl2 / HCl molar ratio in the tail gas discharged from the absorption tower is <5%.

[0122] Judging from the above experimental results, by adopting the process of the present invention, high reaction efficiency, product purity and yield can be balanced, and the proportion of chlorine in the tail gas is relatively low.

[0123] Judging from Examples 1-2 adopting Scheme 1 and Examples 3-5 adopting Scheme 2, after adding a pre-reactor, the reaction efficiency is greatly improved, the total reaction residence time is significantly reduced, and at the same time, the yield of the product CEC can still reach more than 87%.

[0124] Judging from Examples 3-5, by optimizing the conditions of Scheme 2, the side reaction product DCEC can be further reduced, and the reaction yield of CEC is further improved.

[0125] Comparative Example 1

[0126] Use the reaction kettle in Example 1 and operate intermittently. The reaction temperature is 60 °C, the pressure is atmospheric pressure, chlorine is introduced for reaction, the temperature in the kettle is maintained stable and the reaction liquid phase does not boil for 4 h. The mass ratio of EC to carbon tetrachloride is 1:1, and the total molar ratio of chlorine to EC is 1.5:1. Take the reaction liquid and tail gas for analysis. The GC analysis results show that the content of CEC in the liquid phase is 82.1%, the content of DCEC is 6.8%, and there is still about 7% of unreacted EC; the molar ratio of HCl to Cl2 in the tail gas is about 1:0.42. By comparing the data of this comparative example with that of Example 1, it can be seen that the reaction liquid yield of the existing intermittent reaction process is relatively low, significant dichlorination side reactions occur, and there is still a large amount of unreacted Cl2 in the tail gas, further reducing the product yield.

[0127] It is easy to understand that the above examples are only for clear illustration and do not mean that the present invention is only limited to this. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for synthesizing ethylene chlorocarbonate, characterized in that, The method is carried out according to Scheme 1 or Scheme 2. Among them, Scheme 1 includes the following steps (1a)-(2a): (1a) Using carbon tetrachloride as a solvent, chlorine gas and ethylene carbonate are subjected to a chlorination reaction in a chlorination kettle, and the chlorination reaction is carried out under reduced pressure conditions with the liquid in the chlorination kettle in a boiling state; (2a) The gaseous feed stream generated in the chlorination kettle enters a distillation column and contacts a carbon tetrachloride stream in a countercurrent manner. After the countercurrent contact, the carbon tetrachloride stream enters the reaction system of the chlorination kettle; Scheme 2 includes the following steps (1b)-(3b): (1b) Under pressurized conditions, ethylene carbonate and chlorine gas are mixed in a pre-reactor to undergo a partial chlorination reaction to obtain a pre-reaction feed liquid; (2b) The pre-reaction feed liquid and supplementary chlorine gas are subjected to a chlorination reaction in a chlorination kettle in the presence of carbon tetrachloride, and the chlorination reaction is carried out under reduced pressure conditions with the liquid in the chlorination kettle in a boiling state; among them, the carbon tetrachloride is added in the pre-reactor in step (1b) and / or in the chlorination kettle in step (2b); (3b) The gaseous feed stream generated in the chlorination kettle enters a distillation column and contacts a carbon tetrachloride stream in a countercurrent manner. After the countercurrent contact, the carbon tetrachloride stream enters the reaction system of the chlorination kettle.

2. The method according to claim 1, characterized in that, In Scheme 1 or Scheme 2, the reaction pressure in the chlorination kettle is 30-100 kPaA, preferably 50-80 kPaA; the reaction temperature is 40-100 °C, preferably 50-80 °C.

3. The method according to claim 1 or 2, characterized in that, In step (2a) of Scheme 1 or step (3b) of Scheme 2, after the countercurrent contact, the gaseous feed stream is condensed to obtain a liquid phase and a condensed gaseous phase. The liquid phase is refluxed to the distillation column as the carbon tetrachloride stream for the countercurrent contact; Preferably, the condensed gaseous phase is sent to a tail gas absorption tower for treatment and then discharged as tail gas.

4. The method according to any one of claims 1 to 3, characterized in that, In Scheme 1 or Scheme 2, the chlorination reaction is carried out under chemical catalysis or photocatalysis. The photocatalysis is preferably visible light and / or ultraviolet light, more preferably ultraviolet light.

5. The method according to any one of claims 1-4, characterized in that, In Scheme 2, the reaction pressure in step (1b) is 0.3-2 MPaA; the reaction temperature is 40-100 °C, preferably 50-80 °C, and further preferably 50-70 °C.

6. The method according to any one of claims 1-5, characterized in that, In Scheme 2, in step (1b), the conversion rate of ethylene carbonate is controlled to be <40%, preferably <30%, more preferably <20%, and preferably ≥10%.

7. The method according to any one of claims 1-6, characterized in that In Scheme 2, the partial chlorination reaction is carried out in one pre-reactor or multiple pre-reactors connected in series; Each of the pre-reactors is respectively connected to a gas-liquid separation tank. The reaction feed liquid output from the pre-reactor is sent to the gas-liquid separation tank for gas-liquid separation, and a liquid phase product and a gaseous phase product are obtained; When the partial chlorination reaction is carried out in one pre-reactor, the liquid phase product separated from the reaction feed liquid output from the gas-liquid separation tank of the pre-reactor is used as the pre-reaction feed liquid and sent to the chlorination kettle in step (2b); When the partial chlorination reaction is carried out in multiple pre-reactors connected in series, the liquid-phase product separated from the reaction feed liquid output from the upper-stage pre-reactor by the gas-liquid separation tank is sent into the lower-stage pre-reactor for continuous reaction, and the liquid-phase product separated from the reaction feed liquid output from the last-stage pre-reactor by the gas-liquid separation tank is used as the pre-reaction feed liquid and sent into the chlorination kettle in step (2b); preferably, chlorine gas is introduced into each pre-reactor. Preferably, the gas-phase product separated in the gas-liquid separation tank is sent into the tail gas absorption tower for treatment and then discharged as tail gas. Preferably, the pre-reactor is a kettle-type, tower-type or tube-type reactor, preferably a tube-type reactor.

8. The method according to claim 7, characterized in that, In the second solution, when the partial chlorination reaction is carried out in multiple pre-reactors connected in series, the reaction pressure of the upper-stage pre-reactor is equal to or higher than that of the lower-stage pre-reactor; preferably, the reaction temperature of the upper-stage pre-reactor is higher than that of the lower-stage pre-reactor. Preferably, the reaction pressure of each pre-reactor is higher than the pressure of the gas-liquid separation tank used to separate the reaction feed liquid of the corresponding pre-reactor.

9. The method according to any one of claims 1-8, characterized in that, In the first solution, the liquid-phase residence time in the chlorination reaction is 0.8 - 4 h. In the second solution, the total sum of the liquid-phase residence times for carrying out the chlorination reaction in each step is 0.8 - 4 h, for example, 1 - 4 h.

10. The method according to any one of claims 1-9, characterized in that, In the first solution or the second solution, the operating conditions of the distillation column include: The column bottom pressure is 30 - 100 kPaA, the column bottom temperature is 30 - 90 °C, and the reflux ratio is total liquid reflux.

11. The method according to any one of claims 1-10, characterized in that, In the first solution or the second solution, the molar ratio of the total amount of ethylene carbonate used and the total amount of chlorine gas used is 1:1.05 - 1.50, and the mass ratio of the total amount of ethylene carbonate used and the total amount of carbon tetrachloride used is 1:1 - 10. Preferably, in the second solution, in step (1b), the molar ratio of the chlorine gas introduction amount in each pre-reactor and the total amount of ethylene carbonate used is 0.105 - 0.42:1; in step (2b), the molar ratio of the supplementary chlorine gas and the total amount of ethylene carbonate used is 0.90 - 0.58:1.

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