Method and system for continuously synthesizing triphosgene by taking silicon tetrachloride as solvent

Abstract

The invention discloses a method and a system for continuously synthesizing triphosgene by taking silicon tetrachloride as a solvent, and belongs to the technical field of fine chemical production. The triphosgene continuous synthesis method comprises the following steps: S1, mixing dimethyl carbonate and liquid silicon tetrachloride according to a preset proportion, and continuously conveying the mixture to the lower part of a reactor; s2, chlorine is introduced from the bottom of the reactor according to a preset proportion; s3, initiating a chlorination reaction in the reactor through irradiation of an ultraviolet light source; s4, conveying a mixed solution of the reaction product triphosgene and silicon tetrachloride to a normal-pressure flash tank, gasifying and separating the silicon tetrachloride, condensing and recovering the silicon tetrachloride to a solvent recovery tank, and outputting a molten triphosgene product. Silicon tetrachloride is used as a reaction solvent, so that on one hand, the effects of dispersing and diluting materials and reducing the reaction intensity can be achieved, on the other hand, silicon tetrachloride can be used as a heat removal agent, reaction heat is removed out of a reaction system in a mode of absorbing the reaction heat to gasify the silicon tetrachloride, and the safety and controllability of the continuous synthesis reaction process of triphosgene are achieved.

Description

Technical Field

[0001] This application belongs to the field of fine chemical production technology, and in particular relates to a continuous synthesis method and system of triphosgene using silicon tetrachloride as a solvent. Background Technology

[0002] Triphosgene, also known as di(trichloromethyl)carbonate, is an organic compound with the chemical formula C3Cl6O3. It is a white crystalline powder with a phosgene-like odor. It has a molecular weight of 296.75, a melting point of 78–81°C, a boiling point of 203–206°C, a solid density of 1.78 g / cm³, and a melt density of 1.629 g / cm³. It is soluble in organic solvents such as diethyl ether, tetrahydrofuran, benzene, ethane, and chloroform. It is mainly used in the synthesis of chloroformates, isocyanates, polycarbonates, and acyl chlorides, and is widely used as an intermediate in plastics, pharmaceuticals, herbicides, and pesticides.

[0003] Currently, triphosgene is generally synthesized using a bulk method. In a reactor, dimethyl carbonate (C3H6O3, DMC) and chlorine undergo a chlorination reaction under the initiation of a specific wavelength of ultraviolet light to produce triphosgene and hydrogen chloride. Triphosgene production is currently done in a batch process. This reaction is highly exothermic, and dimethyl carbonate is a Class A hazardous material. Therefore, the reaction process is extremely dangerous, posing a high risk of fire or explosion, and resulting in a very high safety hazard.

[0004] Silicon tetrachloride (SiCl4) is one of the most important inorganic silicon compounds. It is a colorless, transparent, flowing, fuming liquid with a boiling point of 57.6°C. It has a suffocating odor and is soluble in most organic solvents such as benzene, ether, and chloroform.

[0005] Chinese patent application CN119874523A discloses a method for preparing triphosgene, specifically stating that in some embodiments, an inert gas is introduced simultaneously with chlorine in the first stage. The introduction of the inert gas further removes the heat of reaction between dimethyl carbonate and chlorine. In some embodiments, the combination of inert gas introduction and dimethyl carbonate vaporization better controls the reaction temperature and ensures reaction safety; furthermore, the yield and purity of triphosgene are further improved. In some embodiments, the inert gas may include any one or more of nitrogen, hydrogen chloride, etc. In some embodiments, the mass ratio of chlorine to inert gas introduced in the first stage is 1:4-5. It is evident that this patent application controls the reaction temperature of triphosgene synthesis by introducing an inert gas. However, this method, due to the introduction of the inert gas, results in a mixture of the inert gas with unreacted chlorine and the byproduct HCl, leading to a complex tail gas composition and increasing the tail gas treatment load.

[0006] Therefore, there is an urgent need for a continuous synthesis method of triphosgene to ensure the safety and controllability of the continuous synthesis reaction process of triphosgene, while also effectively realizing solvent recycling and tail gas treatment. Summary of the Invention

[0007] This application aims to at least partially solve one of the technical problems in the related art. To this end, this application provides a method and system for the continuous synthesis of triphosgene using silicon tetrachloride as a solvent. By using silicon tetrachloride as a reaction solvent, it can both disperse and dilute the materials and reduce the intensity of the reaction, and also act as a heat remover, absorbing the heat of reaction and vaporizing itself to remove the heat of reaction from the reaction system, thus achieving a safe and controllable continuous synthesis reaction process of triphosgene.

[0008] To achieve the above objectives, in a first aspect, this application provides a continuous synthesis method for triphosgene using silicon tetrachloride as a solvent, comprising the following steps:

[0009] S1. Dimethyl carbonate and liquid silicon tetrachloride are mixed in a preset ratio and then continuously transported to the bottom of the reactor;

[0010] S2. Chlorine gas is introduced from the bottom of the reactor in a preset ratio;

[0011] S3. A chlorination reaction is initiated in the reactor by irradiation with an ultraviolet light source.

[0012] S4. The mixture of triphosgene and silicon tetrachloride, the reaction products, is transported to an atmospheric pressure flash tank. After the silicon tetrachloride is vaporized and separated, it is condensed and recovered to a solvent recovery tank, and the molten triphosgene product is output.

[0013] Preferably, step S4 further includes: condensing the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction and then conveying it to a reflux tank; condensing and liquefying silicon tetrachloride and then refluxing it back to the reactor for heat recovery; and conveying the hydrogen chloride gas to the tail gas treatment section.

[0014] Preferably, the mixing of dimethyl carbonate and silicon tetrachloride in step S1 according to a preset ratio includes: the mass ratio of dimethyl carbonate to silicon tetrachloride feed is 1:1.001 to 30.

[0015] Preferably, the ratio of chlorine gas introduced in step S2 is: the mass ratio of dimethyl carbonate to chlorine gas is 1:4.72 to 9.50.

[0016] Preferably, in step S3, the operating temperature of the reactor is higher than the boiling point of silicon tetrachloride, so as to vaporize the liquid silicon tetrachloride to absorb the heat of reaction.

[0017] Preferably, in step S3, the operating temperature of the reactor is 80–110°C and the operating pressure of the reactor is 0.1–0.5 MPaG.

[0018] Preferably, in step S3, the operating temperature of the reactor is 90–100°C and the operating pressure of the reactor is 0.2–0.4 MPaG.

[0019] Preferably, the reaction formula for the chlorination reaction in step S3 is: C3H6O3+Cl2→C3Cl6O3+6HCl.

[0020] Secondly, this application provides a continuous triphosgene synthesis system for implementing the above-described continuous triphosgene synthesis method, the system comprising:

[0021] The reactor has a mixture of dimethyl carbonate and liquid silicon tetrachloride introduced into the lower part and chlorine gas introduced into the bottom for chlorination under ultraviolet light irradiation, wherein the silicon tetrachloride is used as a solvent and heat extractor.

[0022] A reflux condenser, connected to the top of the reactor, is used to condense the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction.

[0023] The reflux tank is connected at one end to the reflux condenser and at the other end to the lower part of the reactor. It is used to reflux the condensed and liquefied silicon tetrachloride back to the reactor for heat recovery. The other end is used to transport the remaining hydrogen chloride gas to the tail gas treatment section.

[0024] A flash evaporator, connected to the upper part of the reactor, receives the mixture of reaction products triphosgene and silicon tetrachloride and performs flash evaporation treatment, and outputs molten triphosgene product after vaporization and separation of silicon tetrachloride.

[0025] A flash condenser, connected to the flash tank, is used to condense the silicon tetrachloride gas flashed out of the flash tank and then recover it to the solvent recovery tank.

[0026] Preferably, the flash tank operates at atmospheric pressure.

[0027] Based on the above technical solution, it can be seen that the continuous synthesis method of triphosgene in this application has at least one of the following beneficial effects compared with the prior art:

[0028] 1. The continuous synthesis method of triphosgene in this application uses silicon tetrachloride as a reaction solvent, which can disperse and dilute the materials and reduce the intensity of the reaction. On the other hand, it can also act as a heat remover, removing the heat of reaction from the reaction system by absorbing the heat of reaction and vaporizing itself. This makes the continuous synthesis reaction process of triphosgene safe and controllable.

[0029] 2. The continuous synthesis method of triphosgene in this application uses silicon tetrachloride as a solvent. Since silicon tetrachloride has excellent chemical stability, it does not participate in side reactions under ultraviolet / chlorine radical environment, thus avoiding the generation of impurities and effectively ensuring product purity.

[0030] 3. The continuous synthesis method of triphosgene in this application has achieved a breakthrough in continuous production. By using solvent recycling and flash separation, the safety bottleneck of traditional batch processes has been solved, and continuous synthesis of triphosgene has been realized. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart of the continuous synthesis method of triphosgene provided in this application;

[0033] Figure 2 This is a connection diagram of the triphosgene continuous synthesis system provided in this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0035] The terms “first,” “second,” “third,” “fourth,” “fifth,” “sixth,” “seventh,” and “eighth,” etc. (if present), in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0036] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0037] Example 1

[0038] like Figure 1 As shown in the embodiments of this application, a continuous synthesis method for triphosgene using silicon tetrachloride as a solvent is provided, comprising the following steps:

[0039] S1. Dimethyl carbonate and liquid silicon tetrachloride are mixed in a preset ratio and then continuously transported to the bottom of the reactor;

[0040] S2. Chlorine gas is introduced from the bottom of the reactor in a preset ratio;

[0041] S3. A chlorination reaction is initiated in the reactor by irradiation with an ultraviolet light source.

[0042] S4. The mixture of triphosgene and silicon tetrachloride, the reaction products, is transported to an atmospheric pressure flash tank. After the silicon tetrachloride is vaporized and separated, it is condensed and recovered to a solvent recovery tank, and the molten triphosgene product is output. The flash tank operates at atmospheric pressure.

[0043] Preferably, step S4 further includes: condensing the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction and then conveying it to a reflux tank; condensing and liquefying silicon tetrachloride and then refluxing it back to the reactor for heat recovery; and conveying the hydrogen chloride gas to the tail gas treatment section.

[0044] This application presents a continuous synthesis method for triphosgene using silicon tetrachloride as a solvent. A mixture of dimethyl carbonate and silicon tetrachloride, along with chlorine gas, is continuously fed into a reactor. Irradiation with an ultraviolet light source installed inside the reactor initiates the reaction, resulting in a vigorous, exothermic reaction that releases hydrogen chloride and silicon tetrachloride gases. The generated gases enter a condenser at the top of the reactor. After condensation, the gas-liquid two-phase mixture enters a reflux tank. The condensed and liquefied silicon tetrachloride is returned to the reactor for heat recovery. The remaining hydrogen chloride gas is pipelined to a tail gas treatment section. The qualified product and silicon tetrachloride are then pipelined from the top of the reactor to a flash tank. During flash evaporation, the silicon tetrachloride in the product is vaporized and separated, then condensed again and sent to a solvent buffer tank for reuse. The remaining molten product enters downstream processes. This method serves to disperse and dilute the materials, reducing the intensity of the reaction, and also acts as a heat extractor, absorbing the heat of reaction and vaporizing itself to remove the heat from the reaction system, thus ensuring a safe and controllable reaction process.

[0045] Preferably, in step S1, the mixing of dimethyl carbonate and silicon tetrachloride in a preset ratio includes a feed mass ratio of dimethyl carbonate to silicon tetrachloride of 1:1.001 to 30. In step S2, the ratio of chlorine gas introduced is 1:1:4.72 to 9.50.

[0046] Optionally, the mass ratio of dimethyl carbonate to silicon tetrachloride in step S1 can be 1:10 to 20. The ratio of chlorine gas introduced in step S2 is 1:4.80 to 5.20.

[0047] Preferably, in step S3, the operating temperature of the reactor is higher than the boiling point of silicon tetrachloride, so as to vaporize the liquid silicon tetrachloride to absorb the heat of reaction and remove the heat of reaction from the reaction system, thereby achieving a safe and controllable reaction process.

[0048] Preferably, in step S3, the reactor operating temperature is 80–110°C, and the reactor operating pressure is 0.1–0.5 MPaG. The lower limit of the reactor operating temperature must be higher than the boiling point of silicon tetrachloride to achieve vaporization and heat extraction, while also ensuring a certain reaction rate; the upper limit of the reactor operating temperature must be lower than the triphosgene decomposition temperature and the equipment's temperature tolerance limit. The reactor operating pressure directly affects the boiling point of the silicon tetrachloride solvent.

[0049] Further optimized, in step S3, the reactor operating temperature is 90–100°C, and the reactor operating pressure is 0.2–0.4 MPaG. This operating temperature and pressure range ensures a suitable reaction rate.

[0050] In the optimal approach, the reactor operating temperature in step S3 is 95°C, and the reactor operating pressure is 0.3 MPaG. At these operating temperatures and pressures, a suitable reaction rate can be achieved, side reactions can be minimized, and the silicon tetrachloride solvent can be fully vaporized for heat extraction.

[0051] Preferably, the chlorination reaction in step S3 is: C3H6O3 + Cl2 → C3Cl6O3 + 6HCl. This reaction releases a large amount of heat, and dimethyl carbonate is a Class A hazardous material. Therefore, the reaction process is extremely dangerous, with a high risk of fire or explosion, posing a very high safety hazard. The solution proposed in this invention uses silicon tetrachloride as the solvent for this reaction. This not only disperses and dilutes the materials, reducing the intensity of the reaction, but also acts as a heat remover, absorbing the heat of reaction and vaporizing itself to remove the heat from the reaction system, thus achieving a safe and controllable reaction process. Silicon tetrachloride is used as the solvent because, unlike toluene and other solvents, it does not undergo a substitution reaction with chlorine free radicals in the reaction system during the reaction, remaining stable and not generating impurities.

[0052] Example 2

[0053] like Figure 2 As shown in the embodiments of this application, a continuous triphosgene synthesis system for implementing the above-described continuous triphosgene synthesis method is provided. The system includes:

[0054] The reactor has a mixture of dimethyl carbonate and liquid silicon tetrachloride introduced into its lower part, and chlorine gas introduced into its bottom for chlorination under ultraviolet light irradiation. The silicon tetrachloride serves as both a solvent and a heat extractor. Several ultraviolet light sources are installed inside the reactor.

[0055] A reflux condenser, connected to the top of the reactor, is used to condense the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction.

[0056] The reflux tank is connected at one end to the reflux condenser and at the other end to the lower part of the reactor. It is used to reflux the condensed and liquefied silicon tetrachloride back to the reactor for heat recovery. The other end is used to transport the remaining hydrogen chloride gas to the tail gas treatment section.

[0057] A flash evaporator, connected to the upper part of the reactor, receives the mixture of reaction products triphosgene and silicon tetrachloride and performs flash evaporation treatment, and outputs molten triphosgene product after vaporization and separation of silicon tetrachloride.

[0058] A flash condenser, connected to the flash tank, is used to condense the silicon tetrachloride gas flashed out of the flash tank and then recover it to the solvent recovery tank.

[0059] A certain amount of dimethyl carbonate and silicon tetrachloride mixture is continuously fed to the bottom of the reactor. The mass ratio of dimethyl carbonate to silicon tetrachloride feed is 1:1.001–30. A certain amount of chlorine gas is introduced from the bottom of the reactor through a pipeline. The mass ratio of dimethyl carbonate to chlorine gas feed is 1:4.75–5.30. After the two raw materials are mixed in the reactor, they are irradiated by an ultraviolet light source installed in the reactor to initiate the reaction, which is violently exothermic and releases hydrogen chloride and silicon tetrachloride gas. The generated gas enters a reflux condenser at the top of the tower. After condensation, the gas and liquid phases enter a reflux tank. The condensed and liquefied silicon tetrachloride is returned to the reactor for heat recovery. The remaining hydrogen chloride gas is transported to the tail gas treatment section through a pipeline. The reactor operating temperature is 95℃, and the reactor operating pressure is 0.3 MPaG. The qualified product and silicon tetrachloride after the reaction are transported from the top of the reactor to the flash tank via pipeline. The flash tank operates at atmospheric pressure. After flash evaporation, the silicon tetrachloride in the product is vaporized and separated, then condensed by a condenser and sent to the solvent buffer tank for reuse. The remaining molten product, phosgene, enters the downstream process.

[0060] Implementation Plan 1:

[0061] Taking a plant with a production capacity of 80 t / a of triphosgene and an annual operating time of 7200 h as an example, the flow rates of dimethyl carbonate, chlorine, and silicon tetrachloride are 3.37, 17.31, and 6.75 kg / h, respectively. The feed mass ratio of dimethyl carbonate to silicon tetrachloride is 1:2, and the feed mass ratio of dimethyl carbonate to chlorine is 1:5.14. The flow rate of the liquid phase product after flash evaporation is 13.33 kg / h, the acid gas flow rate at the outlet of the reflux tank is 7.35 kg / h, and the solvent recovery rate in the solvent reflux tank is 6.75 kg / h, achieving a solvent recovery rate of 100%.

[0062] Implementation Plan 2:

[0063] Based on the apparatus of Example 1, the flow rate of silicon tetrachloride was adjusted, the mass ratio of dimethyl carbonate to silicon tetrachloride feed was 1:1.5, the flow rate of liquid phase product after flash evaporation was 13.33 kg / h, the flow rate of acid gas at the outlet of the reflux tank was 7.35 kg / h, and the solvent recovery rate in the solvent reflux tank was 5.06 kg / h, with the solvent recovery rate still reaching 100%.

[0064] Both implementation schemes achieved a solvent recovery rate of 100%, fully demonstrating the high efficiency and process stability of the solvent recycling system.

[0065] The triphosgene continuous synthesis system of this application uses silicon tetrachloride as a solvent. Due to the excellent chemical stability of silicon tetrachloride, it does not participate in side reactions under ultraviolet / chlorine radical environment, avoiding the generation of impurities and effectively ensuring product purity. In addition, the triphosgene continuous synthesis system achieves a breakthrough in continuous production. Through solvent circulation and flash evaporation separation, it solves the safety bottleneck of traditional batch processes and realizes the continuous synthesis of triphosgene.

[0066] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0067] The foregoing has described specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0068] In the description of the embodiments of the present invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in the embodiments of the present invention, as well as the features of different embodiments or examples.

[0069] The above embodiments are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A continuous synthesis method for triphosgene using silicon tetrachloride as a solvent, characterized in that, Includes the following steps: S1. Dimethyl carbonate and liquid silicon tetrachloride are mixed in a preset ratio and then continuously transported to the bottom of the reactor; S2. Chlorine gas is introduced from the bottom of the reactor in a preset ratio; S3. A chlorination reaction is initiated in the reactor by irradiation with an ultraviolet light source. S4. The mixture of triphosgene and silicon tetrachloride, the reaction products, is transported to an atmospheric pressure flash tank. After the silicon tetrachloride is vaporized and separated, it is condensed and recovered to a solvent recovery tank, and the molten triphosgene product is output.

2. The method for continuous synthesis of triphosgene according to claim 1, characterized in that, Step S4 further includes: condensing the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction and then sending it to a reflux tank; condensing and liquefying silicon tetrachloride and sending it back to the reactor for heat recovery; and sending hydrogen chloride gas to the tail gas treatment section.

3. The method for continuous synthesis of triphosgene according to claim 1, characterized in that, The mixing of dimethyl carbonate and silicon tetrachloride in step S1 according to a preset ratio includes: the mass ratio of dimethyl carbonate to silicon tetrachloride feed is 1:1.001 to 30.

4. The method for continuous synthesis of triphosgene according to claim 1, characterized in that, The ratio of chlorine gas introduced in step S2 is: the mass ratio of dimethyl carbonate to chlorine gas is 1:4.72 to 9.

50.

5. The method for continuous synthesis of triphosgene according to claim 1, characterized in that, In step S3, the reactor operates at a temperature higher than the boiling point of silicon tetrachloride, which is used to vaporize the liquid silicon tetrachloride to absorb the heat of reaction.

6. The method for continuous synthesis of triphosgene according to claim 5, characterized in that, In step S3, the reactor operating temperature is 80–110°C and the reactor operating pressure is 0.1–0.5 MPaG.

7. The method for continuous synthesis of triphosgene according to claim 5, characterized in that, In step S3, the reactor operating temperature is 90–100°C and the reactor operating pressure is 0.2–0.4 MPaG.

8. The method for continuous synthesis of triphosgene according to claim 1, characterized in that, The reaction equation for the chlorination reaction in step S3 is: C3H6O3 + Cl2 → C3Cl6O3 + 6HCl.

9. A continuous triphosgene synthesis system for implementing the continuous triphosgene synthesis method according to any one of claims 1-8, characterized in that, The system includes: The reactor has a mixture of dimethyl carbonate and liquid silicon tetrachloride introduced into the lower part and chlorine gas introduced into the bottom for chlorination under ultraviolet light irradiation, wherein the silicon tetrachloride is used as a solvent and heat extractor. A reflux condenser, connected to the top of the reactor, is used to condense the mixed gas of hydrogen chloride and silicon tetrachloride produced by the chlorination reaction. The reflux tank is connected at one end to the reflux condenser and at the other end to the lower part of the reactor. It is used to reflux the condensed and liquefied silicon tetrachloride back to the reactor for heat recovery. The other end is used to transport the remaining hydrogen chloride gas to the tail gas treatment section. A flash evaporator, connected to the upper part of the reactor, receives the mixture of reaction products triphosgene and silicon tetrachloride and performs flash evaporation treatment, and outputs molten triphosgene product after vaporization and separation of silicon tetrachloride. A flash condenser, connected to the flash tank, is used to condense the silicon tetrachloride gas flashed out of the flash tank and then recover it to the solvent recovery tank.

10. The continuous synthesis system of triphosgene according to claim 9, characterized in that, The flash tank operates at atmospheric pressure.

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