Preparation method of triphosgene

Abstract

The invention relates to the field of chemical preparation, and discloses a triphosgene preparation method, which comprises: S1, introducing dimethyl carbonate into a reaction device in a liquid state, and maintaining the temperature in the reaction device to be lower than the boiling point of the dimethyl carbonate; in the step S2, chlorine is introduced into the reaction device, the liquid dimethyl carbonate and the chlorine react under illumination, and the gasified dimethyl carbonate in the reaction process is condensed and then flows back into the reaction device. In the step S3, the reaction is finished, and triphosgene is obtained.

Description

Technical Field

[0001] The present disclosure relates to the field of chemical preparation, and in particular to a method for preparing triphosgene. Background Art

[0002] Triphosgene, also known as bis(trichloromethyl) carbonate or solid phosgene. Triphosgene is low in toxicity, safe and convenient to use, and is an ideal substitute for phosgene. Triphosgene can be used to synthesize chloroformate, isocyanate, polycarbonate and acyl chloride, and is widely used as an intermediate in plastics, medicines, herbicides and pesticides.

[0003] The preparation methods of triphosgene mainly include the dissolution method and the bulk method. The solvent method refers to using carbon tetrachloride as a solvent, dissolving dimethyl carbonate in the solvent, and placing it in a quartz reactor with a jacketed heat exchange device, irradiating it with ultraviolet light from the inside or outside, and continuously passing chlorine to react and obtain triphosgene. The bulk method does not use carbon tetrachloride solvent, directly uses dimethyl carbonate as a bulk for photocatalytic chlorination reaction, and adds a photoinitiator for chlorination. The existing preparation methods of triphosgene have problems such as long reaction time. Summary of the invention

[0004] The present disclosure provides a method for preparing triphosgene, comprising the following steps:

[0005] S1. dimethyl carbonate is introduced into the reaction apparatus in liquid form, wherein the temperature within the reaction apparatus is maintained below the boiling point of dimethyl carbonate;

[0006] S2. Chlorine is introduced into the reaction device, and the liquid dimethyl carbonate reacts with the chlorine under light, and the gasified dimethyl carbonate is condensed during the reaction and then refluxed into the reaction device;

[0007] S3. The reaction is completed and triphosgene is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0009] Figure 1 A flow chart showing a method for preparing triphosgene according to some embodiments of the present disclosure is shown.

[0010] Figure 2 The detailed operation steps in step S2 according to some embodiments of the present disclosure are shown.

[0011] Figure 3 A schematic structural diagram of a reaction device according to some embodiments of the present disclosure is shown.

[0012] Markings in the accompanying drawings:

[0013] 100-Reaction device

[0014] 110-first stage reactor, 111-first stage reactor liquid inlet, 112-first stage reactor gas inlet, 113-first stage reactor liquid outlet, 114-first stage reactor gas outlet, 115-condensing reflux device

[0015] 120-second stage reactor, 121-second stage reactor liquid inlet, 122-second stage reactor gas inlet, 123-second stage reactor liquid outlet, 124-second stage reactor gas outlet

[0016] 130-third-stage reactor, 131-third-stage reactor liquid inlet, 132-third-stage reactor gas inlet, 133-third-stage reactor liquid outlet, 134-third-stage reactor gas outlet DETAILED DESCRIPTION

[0017] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0018] Figure 1 A flow chart showing a method for preparing triphosgene according to some embodiments of the present disclosure is shown.

[0019] like Figure 1 As shown, in some embodiments of the present disclosure, the method for preparing triphosgene may include the following steps: In step S1, dimethyl carbonate is introduced into a reaction device in liquid form, and the temperature in the reaction device is maintained below the boiling point of dimethyl carbonate. In step S2, chlorine is introduced into the reaction device, and the liquid dimethyl carbonate reacts with the chlorine under light, and the gasified dimethyl carbonate condenses during the reaction and then flows back into the reaction device. In step S3, the reaction ends and triphosgene is obtained.

[0020] In some embodiments of the present disclosure, in step S1, dimethyl carbonate is introduced into the reaction unit in liquid form, which can prevent dimethyl carbonate from being immediately gasified when entering the reaction unit, and helps to ensure the safe conduct of the reaction. In step S2, part of the dimethyl carbonate in the reaction unit is gasified by controlling the reaction conditions, and the gasified dimethyl carbonate can continue to react with the unreacted chlorine in the gas phase in the reaction unit, thereby accelerating the reaction rate. The gasification of dimethyl carbonate can remove the heat of reaction, help ensure the safe conduct of the reaction, and help reduce by-products in the reaction process.

[0021] In some embodiments of the present disclosure, in step S2, the wavelength of the illumination light is 200nm-450nm, and the illumination intensity is 5000Lux-150000Lux.

[0022] In some embodiments of the present disclosure, in step S2, the wavelength of the irradiated light is 200-400 nm.

[0023] In some preferred embodiments of the present disclosure, in step S2, the wavelength of the irradiated light is 300-400 nm.

[0024] In some embodiments of the present disclosure, in step S2, the illuminance is 15000 Lux-70000 Lux.

[0025] In some preferred embodiments of the present disclosure, in step S2, the illuminance is 30000 Lux-60000 Lux.

[0026] In some embodiments of the present disclosure, in step S2, while introducing chlorine gas, the reaction device will gradually increase in temperature to at least 50°C, and ensure that the temperature does not exceed 130°C.

[0027] In some embodiments of the present disclosure, the molar ratio of the total amount of dimethyl carbonate to the total amount of chlorine introduced into the reaction device is 1:6.05-6.20.

[0028] Figure 2 The detailed operation steps in step S2 according to some embodiments of the present disclosure are shown.

[0029] like Figure 2 As shown, in some embodiments of the present disclosure, in step S2, the reaction can be divided into at least two stages, including: S21. The first stage: while introducing chlorine, the reaction device will gradually heat up to at least 50°C, ensuring that the temperature does not exceed 90°C, the light wavelength is 200nm-450nm, the illuminance is 5000Lux-90000Lux, the amount of chlorine introduced accounts for 1 / 2-2 / 3 of the total amount of chlorine, and the dimethyl carbonate vaporized during the reaction is condensed and then refluxed into the reaction device; S22. Subsequent stage: control the reaction temperature to 70-130°C, the light wavelength is 200nm-450nm, the illuminance is 15000Lux-150000Lux, and introduce the remaining chlorine.

[0030] In some preferred embodiments, the reaction temperature of the subsequent stage is controlled to be higher than the reaction temperature of the first stage.

[0031] In some embodiments of the present disclosure, the subsequent stage S22 may include: S221: controlling the reaction temperature to 70-100°C, the light wavelength to 200nm-450nm, the illuminance to 15000Lux-80000Lux, and the amount of chlorine introduced to account for 1 / 5-1 / 4 of the total amount of chlorine; S222. Remaining stage: controlling the reaction temperature to 90-130°C, the light wavelength to 200nm-450nm, the illuminance to 30000Lux-150000Lux, and introducing the remaining amount of chlorine.

[0032] In some embodiments of the present disclosure, by dividing the specific reaction process into multiple stages, the reaction rate can be better improved, and the purity and yield of the final product can be improved. Specifically, in some embodiments of the present disclosure, in the first stage of S21, the reaction temperature is controlled to be 50-90 ° C, the light wavelength is 200nm-450nm, and the illuminance is 5000Lux-90000Lux, and the amount of chlorine introduced accounts for 1 / 2-2 / 3 of the total amount of chlorine, which can not only accelerate the light chlorination reaction rate, but also quickly remove the reaction heat by dimethyl carbonate gasification, and the gas phase dimethyl carbonate after gasification can further react with the chlorine overflowing from the liquid phase dimethyl carbonate, and the free radical reaction is easier to carry out in the gas phase reaction, so as to further accelerate the reaction rate. In the subsequent stage, due to the introduction of chlorine atoms, the substitution reactivity is reduced, and further increased by the reaction temperature, etc., the reactivity of chlorine atoms to further replace hydrogen atoms is improved.

[0033] In some embodiments of the present disclosure, an inert gas is introduced at the same time as the chlorine introduced in the first stage. The introduction of the inert gas can further remove the reaction heat of dimethyl carbonate and chlorine. In some embodiments of the present disclosure, the introduction of the inert gas is combined with the gasification of dimethyl carbonate to better control the reaction temperature and ensure the safety of the reaction. In addition, the yield and purity of triphosgene are further improved.

[0034] In some embodiments of the present disclosure, the inert gas may include any one or more of nitrogen, hydrogen chloride, etc.

[0035] In some embodiments of the present disclosure, the mass ratio of the chlorine gas introduced in the first stage to the inert gas introduced is 1:4-5.

[0036] In some embodiments of the present disclosure, while introducing chlorine gas, the reaction device will gradually increase in temperature to at least 70°C, and ensure that the temperature does not exceed 100°C.

[0037] In some embodiments of the present disclosure, in the first stage, the reaction temperature is controlled to be 70-100° C. and the light wavelength is 200nm-400nm.

[0038] In some preferred embodiments of the present disclosure, in the first stage, the wavelength of light is 300nm-400nm.

[0039] In some embodiments of the present disclosure, the wavelength of the light in the second stage is 200nm-400nm. In some embodiments of the present disclosure, the wavelength of the light in the second stage is 300nm-400nm.

[0040] In some embodiments of the present disclosure, the wavelength of the light in the third stage is 200nm-400nm. In some embodiments of the present disclosure, in the third stage, the wavelength of the light is 300nm-400nm.

[0041] The inventors have found in their research that in some embodiments of the present disclosure, controlling the wavelength of light in each reaction stage to be 200nm-400nm, especially when the wavelength of light is controlled to be 300nm-400nm, can further improve the purity and yield of the final product.

[0042] In some embodiments of the present disclosure, the reaction device includes a multi-stage reactor connected in sequence, dimethyl carbonate is introduced from the first-stage reactor, and chlorine is introduced into the first-stage reactor at the same time. After the reaction of dimethyl carbonate and chlorine in the first-stage reactor, the product enters the second-stage reactor and reacts with the chlorine introduced into the second-stage reactor. Similarly, the material reacted in the previous reactor enters the next reactor and reacts with the introduced chlorine, and triphosgene is obtained from the discharge of the last reactor.

[0043] In some embodiments of the present disclosure, the multi-stage reactors connected in sequence include a second-stage reactor connected in sequence, a third-stage reactor connected in sequence, a fourth-stage reactor connected in sequence, a fifth-stage reactor connected in sequence, or a sixth-stage reactor connected in sequence.

[0044] In some embodiments of the present disclosure, the first-stage reactor in the multiple-stage reactors connected in sequence comprises a condensation reflux device.

[0045] In some embodiments of the present disclosure, in the multiple-stage reactors connected in sequence, each stage of the reactor includes a condensation reflux device.

[0046] Figure 3 A schematic structural diagram of a reaction device 100 according to some embodiments of the present disclosure is shown.

[0047] like Figure 3 As shown, in some embodiments of the present disclosure, the multi-stage reactors connected in sequence include three-stage reactors connected in sequence, wherein:

[0048] The first-stage reactor 110 includes a first-stage reactor liquid inlet 111, a first-stage reactor gas inlet 112, a first-stage reactor liquid outlet 113, a first-stage reactor gas outlet 114 and a condensation reflux device 115. Dimethyl carbonate is introduced into the first-stage reactor 110 in liquid form through the first-stage reactor liquid inlet 111. At this time, the temperature in the first-stage reactor 110 is maintained below the boiling point of dimethyl carbonate. Chlorine gas is then introduced through the first-stage reactor gas inlet 112. While introducing chlorine gas, the first-stage reactor 110 will gradually heat up to at least 50° C. to ensure that the temperature does not exceed 90° C. The light wavelength is controlled to be 200nm-450nm, the illumination is 5000Lux-90000Lux, and the amount of chlorine gas introduced accounts for 1 / 2-2 / 3 of the total amount of chlorine gas. During the reaction, the vaporized dimethyl carbonate is condensed by the condensation reflux device 115 and then refluxed into the first-stage reactor 110;

[0049] The second-stage reactor 120 includes a second-stage reactor liquid inlet 121, a second-stage reactor gas inlet 122, a second-stage reactor liquid outlet 123, and a second-stage reactor gas outlet 124. The liquid material of the first-stage reactor enters the second-stage reactor 120 from the first-stage reactor liquid outlet 113 through the second-stage reactor liquid inlet 121. At the same time, chlorine gas is introduced from the second-stage reactor gas inlet 122. The reaction temperature is controlled to be 70-100° C., the light wavelength is 200nm-450nm, the illumination is 15000Lux-80000Lux, and the amount of chlorine gas introduced accounts for 1 / 5-1 / 4 of the total amount of chlorine gas.

[0050] The third-stage reactor 130 includes a third-stage reactor liquid inlet 131, a third-stage reactor gas inlet 132, a third-stage reactor liquid outlet 133, and a third-stage reactor gas outlet 134. The liquid material of the second-stage reactor enters the third-stage reactor 130 from the second-stage reactor liquid outlet 123 through the third-stage reactor liquid inlet 131. At the same time, chlorine gas is introduced from the third-stage reactor gas inlet 132. The reaction temperature is controlled to be 90-130°C, the light wavelength is 200nm-450nm, the illumination is 30000Lux-150000Lux, and the residual chlorine gas is introduced.

[0051] In some embodiments of the present disclosure, in step S1, the temperature in the reaction device is maintained at 20-40°C.

[0052] In some embodiments of the present disclosure, after the reaction in step S3 is completed, the reaction solution is freed of residual gas, and the triphosgene product is obtained after cooling and crystallization.

[0053] In some embodiments of the present disclosure, the reaction is terminated when the tail gas discharged from the reaction device substantially does not contain hydrogen chloride.

[0054] The present invention will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents and materials used in the examples are, unless otherwise stated, conventional methods, reagents and materials in the art. The raw materials in the examples can all be purchased through commercial sources.

[0055] In the following examples, the purity of triphosgene is determined by utilizing the hydrolysis reaction of triphosgene. Triphosgene is completely dissolved at a certain temperature (e.g., 40° C.) to generate carbon dioxide and hydrogen chloride. The dissolved hydrogen chloride is titrated with an excess of a standard sodium hydroxide solution, and the remaining sodium hydroxide is titrated with a standard hydrochloric acid solution to calculate the percentage of triphosgene.

[0056] Example 1

[0057] 200g of dimethyl carbonate was introduced into a reaction unit with a condensation reflux device in liquid form, and the temperature in the reaction unit was maintained at 25°C. Chlorine was introduced into the reaction unit, and while introducing the chlorine, the reaction unit was gradually heated to 70°C and maintained at this temperature, and the liquid dimethyl carbonate and the chlorine reacted under illumination, the wavelength of the illumination was 420nm, and the illumination was 100000Lux. The gasified dimethyl carbonate in the reaction process was condensed and then refluxed into the reaction unit, and the reaction consumed a total of 968g of chlorine. After 23 hours and 25 minutes, the reaction was terminated, and the reaction solution was freed of residual gas. After cooling and crystallization, 654g of triphosgene product was obtained with a purity of 95.8%.

[0058] Example 2

[0059] 200g of dimethyl carbonate was introduced into a reaction unit with a condensation reflux device in liquid form, and the temperature in the reaction unit was maintained at 25°C. Chlorine was introduced into the reaction unit, and while introducing the chlorine, the reaction unit was gradually heated to 80°C and maintained at this temperature, and the liquid dimethyl carbonate and the chlorine reacted under illumination, the wavelength of the illumination was 360nm, and the illumination was 120000Lux. The gasified dimethyl carbonate in the reaction process was condensed and then refluxed into the reaction unit, and the reaction consumed a total of 975g of chlorine. After about 18 hours, the reaction was terminated, and the reaction solution was freed of residual gas. After cooling and crystallization, 643g of triphosgene product was obtained with a purity of 97.2%.

[0060] Example 3

[0061] 200g of dimethyl carbonate was introduced into a reaction unit with a condensation reflux device in liquid form, and the temperature in the reaction unit was maintained at 25°C. Chlorine was introduced into the reaction unit, and while introducing the chlorine, the reaction unit was gradually heated to 50°C and maintained at this temperature, and the liquid dimethyl carbonate and the chlorine reacted under illumination, the wavelength of the illumination was 240nm, and the illumination was 50000Lux. The gasified dimethyl carbonate in the reaction process was condensed and then refluxed into the reaction unit, and the reaction consumed a total of 972g of chlorine. After about 17 hours, the reaction was terminated, and the reaction solution was freed of residual gas. After cooling and crystallization, 655g of triphosgene product was obtained with a purity of 96.3%.

[0062] Example 4

[0063] 200g dimethyl carbonate is introduced into the reaction unit with condensation reflux device in liquid form, and the temperature in the reaction unit is maintained at 25 ℃. 479g of chlorine is introduced into the reaction unit, and while introducing chlorine, the reaction unit is gradually heated to 60 ℃ and maintained at this temperature, the wavelength of light is 240nm, and the illumination is 5000Lux. Liquid dimethyl carbonate reacts with chlorine under illumination, and the first stage reaction takes about 2 hours. After the first stage reaction ends, the temperature is raised to 80 ℃, 192g of chlorine is introduced, and the light wavelength is 440nm, and the illumination is 40000Lux, and the photochlorination reaction is continued, and the second stage reaction takes about 2 hours. After the second stage reaction ends, the temperature is continued to be raised to 90 ℃, 287g of chlorine is introduced, the wavelength of light is 220nm, and the illumination is 50000Lux, and the photochlorination reaction is continued, and the third stage reaction takes about 6 hours. After the reaction was completed, the reaction solution was freed of residual gas and cooled and crystallized to obtain 652 g of triphosgene product with a purity of 97.7%.

[0064] This embodiment can use Figure 3 The reaction device shown, wherein the first stage reaction can be carried out in the first stage reactor 110, the second stage reaction can be carried out in the second stage reactor 120, and the third stage reaction can be carried out in the third stage reactor 130.

[0065] Example 5

[0066] 200g dimethyl carbonate is introduced into the reaction unit with condensation reflux device in liquid form, and the temperature in the reaction unit is maintained at 25 ℃. 582.6g of chlorine is introduced into the reaction unit, and while introducing chlorine, the reaction unit is gradually heated to 70 ℃ and maintained at this temperature, the wavelength of light is 360nm, and the illumination is 70000Lux. Liquid dimethyl carbonate reacts with chlorine under illumination, and the first stage reaction takes about 2 hours. After the first stage reaction ends, the temperature is raised to 90 ℃, 223g of chlorine is introduced, the wavelength of light is 410nm, and the illumination is 80000Lux, and photochlorination reaction is carried out, and the second stage reaction takes 3 hours. After the second stage reaction ends, the temperature continues to be raised to 110 ℃, 165g of chlorine is introduced, the wavelength of light is 250nm, and the illumination is 100000Lux, and the reaction is carried out, and the third stage reaction takes 4 hours. After the reaction was completed, the reaction solution was freed of residual gas and cooled for crystallization to obtain 656 g of triphosgene product with a purity of 98%.

[0067] Example 6

[0068] 200g of dimethyl carbonate is introduced into a reaction device with a condensation reflux device in liquid form, and the temperature in the reaction device is maintained at 25°C. 642.8g of chlorine is introduced into the reaction device. While introducing chlorine, the reaction device is gradually heated to 75°C and maintained at this temperature. The wavelength of light is 350nm, the illumination is 70000Lux, and liquid dimethyl carbonate reacts with chlorine under illumination. The first stage reaction takes 1.5 hours. After the first stage reaction is completed, the temperature is raised to 100°C, 244g of chlorine is introduced, the wavelength of light is 450nm, the illumination is 80000Lux, and liquid dimethyl carbonate reacts with chlorine under illumination. The second stage reaction takes 2 hours. After the second stage reaction is completed, the temperature is continued to be raised to 120°C, 88g of chlorine is introduced, the wavelength of light is 410nm, the illumination is 150000Lux, and liquid dimethyl carbonate reacts with chlorine under illumination. The third stage reaction takes 3 hours. After the reaction was completed, the reaction solution was freed of residual gas and cooled and crystallized to obtain 654 g of triphosgene product with a purity of 98.4%.

[0069] Example 7

[0070] The same as Example 5, except that 2331 g of nitrogen was introduced in the first stage, and the reaction took a total of 8.7 hours. After the reaction was completed, the reaction solution was freed of residual gas, cooled and crystallized to obtain 650 g of triphosgene product with a purity of 99.5%.

[0071] Example 8

[0072] The same as Example 6, except that 3214 g of nitrogen was introduced in the first stage, and the reaction took a total of 6.3 hours. After the reaction was completed, the reaction solution was freed of residual gas, cooled and crystallized, and 651 g of triphosgene product was obtained with a purity of 99.7%.

[0073] Example 9

[0074] The same as Example 7, except that the wavelength of light in the first stage, the second stage and the third stage is 390 nm, and the reaction takes about 8.9 hours in total. After the reaction, the reaction solution is freed of residual gas, cooled and crystallized to obtain 649 g of triphosgene product with a purity of 99.8%.

[0075] Example 10

[0076] The same as Example 8, except that the wavelength of the light in the second stage is 390 nm, the wavelength of the light in the third stage is 320 nm, and the total reaction time is about 6.1 hours. After the reaction is completed, the reaction solution is freed of residual gas, cooled and crystallized to obtain 652 g of triphosgene product with a purity of 99.9%.

[0077] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing triphosgene, characterized in that: The following steps are involved: S1. dimethyl carbonate is introduced into the reaction apparatus in liquid form, wherein the temperature within the reaction apparatus is maintained below the boiling point of dimethyl carbonate; S2. Chlorine is introduced into the reaction device, and the liquid dimethyl carbonate reacts with the chlorine under light, and the gasified dimethyl carbonate is condensed during the reaction and then refluxed into the reaction device; S3. The reaction is completed and triphosgene is obtained.

2. The method for preparing triphosgene according to claim 1, characterized in that: In step S2, the wavelength of the illumination light is 200nm-450nm, and the illumination intensity is 5000Lux-150000Lux.

3. The method for preparing triphosgene according to claim 2, characterized in that: In step S2, the wavelength of the light irradiated is 200-400nm; and / or In step S2, the illumination is 15000 Lux-70000 Lux.

4. The method for preparing triphosgene according to claim 2, characterized in that: In step S2, the wavelength of the light irradiated is 300-400nm; and / or In step S2, the illumination is 30000Lux-60000Lux.

5. The method for preparing triphosgene according to claim 1, characterized in that: In step S2, while introducing chlorine gas, the reaction device will gradually heat up to at least 50°C, and ensure that the temperature does not exceed 130°C.

6. The method for preparing triphosgene according to claim 1, characterized in that: The molar ratio of the total amount of dimethyl carbonate to the total amount of chlorine introduced into the reaction device is 1:6.05-6.

20.

7. The method for preparing triphosgene according to claim 1, characterized in that: In step S2, the reaction is divided into at least two stages, including: S21. The first stage: while introducing chlorine, the reaction device will gradually heat up to at least 50°C, ensuring that the temperature does not exceed 90°C, the wavelength of light is 200nm-450nm, the illumination is 5000Lux-90000Lux, the amount of chlorine introduced accounts for 1 / 2-2 / 3 of the total amount of chlorine, and the dimethyl carbonate vaporized during the reaction is condensed and then refluxed into the reaction device; S22. Subsequent stage: control the reaction temperature to 70-130°C, the light wavelength to 200nm-450nm, the illumination to 15000Lux-150000Lux, and introduce the residual chlorine gas.

8. The method for preparing triphosgene according to claim 7, characterized in that: The S22 subsequent stage includes: S221: Control the reaction temperature to 70-100°C, the light wavelength to 200nm-450nm, the illumination to 15000Lux-80000Lux, and the amount of chlorine introduced to account for 1 / 5-1 / 4 of the total amount of chlorine; S222. Remaining stage: control the reaction temperature to 90-130°C, the light wavelength to 200nm-450nm, the illumination to 30000Lux-150000Lux, and introduce the remaining chlorine gas.

9. The method for preparing triphosgene according to claim 7, characterized in that: The chlorine gas introduced in the first stage is simultaneously introduced with the inert gas.

10. The method for preparing triphosgene according to claim 9, characterized in that: The mass ratio of the chlorine gas introduced in the first stage to the inert gas introduced is 1:4-5.

11. The method for preparing triphosgene according to claim 5, characterized in that: While the chlorine gas is being introduced, the temperature of the reaction unit will be gradually raised to at least 70°C, ensuring that the temperature does not exceed 100°C.

12. The method for preparing triphosgene according to claim 1, characterized in that: The reaction device comprises a plurality of reactors connected in sequence, wherein dimethyl carbonate is introduced from a first-stage reactor, and then chlorine is introduced into the first-stage reactor. After the dimethyl carbonate and chlorine react in the first-stage reactor, the product enters a second-stage reactor and reacts with the chlorine introduced into the second-stage reactor. Similarly, the material reacted in the previous-stage reactor enters a next-stage reactor and reacts with the introduced chlorine, and triphosgene is obtained from the discharge of the last-stage reactor.

13. The method for preparing triphosgene according to claim 12, characterized in that: The multi-stage reactors connected in sequence include a second-stage reactor connected in sequence, a third-stage reactor connected in sequence, a fourth-stage reactor connected in sequence, a fifth-stage reactor connected in sequence, or a sixth-stage reactor connected in sequence.

14. The method for preparing triphosgene according to claim 12, characterized in that: Among the multi-stage reactors connected in sequence, at least the first-stage reactor includes a condensation reflux device.

15. The method for preparing triphosgene according to claim 12, characterized in that: The multi-stage reactors connected in sequence include three-stage reactors connected in sequence, wherein: The first stage reactor: including a condensation reflux device, the reaction temperature is controlled to be 50-90°C, the light wavelength is 200nm-450nm, the illumination is 5000Lux-90000Lux, and the amount of chlorine introduced accounts for 1 / 2-2 / 3 of the total amount of chlorine; Second stage reactor: control the reaction temperature to 70-100℃, the light wavelength to 200nm-450nm, the illumination to 15000Lux-80000Lux, and the amount of chlorine introduced to account for 1 / 5-1 / 4 of the total amount of chlorine; The third-stage reactor: control the reaction temperature to 90-130°C, the light wavelength to 200nm-450nm, the illumination to 30000Lux-150000Lux, and introduce the residual chlorine gas.

16. The method for preparing triphosgene according to claim 1, characterized in that: In step S1, the temperature in the reaction device is maintained at 20-40°C.

17. The method for preparing triphosgene according to claim 1, characterized in that: After the reaction is completed, the reaction solution is freed of residual gas and cooled and crystallized to obtain triphosgene product.

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