An apparatus for the preparation of isocyanates

Abstract

This invention provides an apparatus for preparing isocyanates, comprising: a heater; a reaction vessel disposed within the heater, the reaction vessel including at least a first opening, a second opening, and a third opening, each opening connecting the inside and outside of the reaction vessel; a gas input pipeline connected to the first opening; a condenser connected to the second opening; a receiving bottle connected to the end of the condenser away from the second opening; a distillation column connected to the third opening; a condenser with its inlet connected to the end of the distillation column away from the third opening and its outlet returning to the distillation column; a vacuum pump including at least a first inlet and a second inlet, the first inlet connected to the condenser and the second inlet connected to the condenser; and a gas output pipeline connected to the outlet of the vacuum pump. The preparation apparatus provided by this invention can solve the problems of low product yield, high purification difficulty, high reaction energy consumption, and high production cost.

Description

Technical Field

[0001] This utility model relates to the field of aromatic diisocyanate synthesis technology, and in particular to an isocyanate preparation apparatus. Background Technology

[0002] Isocyanates, as raw materials, are mainly used in the production of polyurethane flexible foams, polyurethane elastomers, and adhesives. They are widely used in furniture cushions, mattresses, and vehicle seat cushions, as well as in industrial and civilian filter materials, sound insulation materials, shock-absorbing materials, decorative materials, packaging materials, and thermal insulation materials. Among these, the catalytic decomposition method for preparing isocyanates has received considerable attention due to its advantages such as low reaction temperature and the recyclability of byproducts. However, the catalytic decomposition process for preparing isocyanates suffers from problems such as low product yield, high purification difficulty, high reaction energy consumption, and high production costs, which limit the further application of the catalytic decomposition method. Utility Model Content

[0003] This invention provides an apparatus for preparing isocyanates to solve the technical problems of low product yield, high purification difficulty, high reaction energy consumption, and high production cost.

[0004] This utility model provides an isocyanate preparation apparatus, comprising at least:

[0005] heater;

[0006] A reaction vessel is disposed inside the heater, and the reaction vessel includes at least a first opening, a second opening and a third opening, each of the openings communicating with the inside and outside of the reaction vessel.

[0007] A gas inlet pipe is connected to the first opening;

[0008] The condenser tube is connected to the second opening;

[0009] A receiving bottle is connected to the end of the condenser tube furthest from the second opening;

[0010] The distillation column is connected to the third opening;

[0011] A condenser, with its inlet connected to the end of the distillation column away from the third opening, and an outlet returning to the distillation column;

[0012] A vacuum pump, comprising at least a first inlet and a second inlet, wherein the first inlet is connected to the condenser tube and the second inlet is connected to the condenser; and

[0013] The gas output pipeline is connected to the outlet of the vacuum pump.

[0014] In one embodiment of the present invention, the condenser includes at least a first outlet, a second outlet, and a third outlet, wherein the first outlet is connected to the distillation column.

[0015] In one embodiment of the present invention, the preparation device further includes a product collection tank, and the second outlet is connected to the inlet of the product collection tank.

[0016] In one embodiment of this utility model, the third outlet and the outlet of the product collection tank are connected in parallel and then connected to the second inlet.

[0017] In one embodiment of the present invention, the preparation device further includes a differential pressure gauge, which is disposed between the parallel main line between the outlet of the product collection tank and the third outlet, and between the second inlet.

[0018] In one embodiment of the present invention, the preparation apparatus further includes a switching valve disposed between the condenser tube and the second opening.

[0019] In one embodiment of the present invention, the preparation apparatus further includes a shut-off valve, which is disposed between the distillation column and the reaction vessel.

[0020] In one embodiment of the present invention, the distillation column includes at least a column body, one end of which is connected to the third opening.

[0021] In one embodiment of the present invention, the distillation column further includes a column top, which is connected to the other end of the column body.

[0022] In one embodiment of the present invention, the preparation device further includes a temperature detection unit, one end of which extends into the top of the tower and the other end extends out of the top of the tower.

[0023] This invention proposes an isocyanate preparation apparatus. By improving the apparatus, it effectively avoids the polymerization of isocyanates upon heating, thereby increasing the purity and yield of isocyanates, saving on heating processes, and reducing energy consumption. Furthermore, the apparatus incorporates a stabilizing gas, which helps control the reaction rate and mass transfer, enabling efficient decomposition and precise separation at lower temperatures and pressures, thus improving the yield and selectivity of isocyanates. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0025] In the attached diagram:

[0026] Figure 1 This is a schematic diagram of an isocyanate preparation apparatus provided in an embodiment of the present invention.

[0027] The attached figures are labeled as follows:

[0028] 11. Heater; 12. Reactor; 121. First opening; 122. Second opening; 123. Third opening; 13. Gas input pipeline; 14. Switching valve; 15. Condenser; 16. Receiving bottle; 17. Vacuum pump; 171. First inlet; 172. Second inlet; 18. Gas output pipeline; 19. Shut-off valve; 20. Distillation column; 201. Column body; 202. Packing; 203. Top of column; 21. Temperature detection unit; 22. Condenser; 221. First outlet; 222. Second outlet; 223. Third outlet; 23. Reflux regulating valve; 24. Product collection tank; 25. Differential pressure gauge. Detailed Implementation

[0029] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0032] Please see Figure 1 As shown, this utility model provides an isocyanate preparation apparatus, comprising at least: a heater 11, a reaction vessel 12, a gas input pipeline 13, a condenser 15, a receiving bottle 16, a distillation column 20, a condenser 22, a vacuum pump 17, and a gas output pipeline 18, etc. The reaction vessel 12 is disposed within the heater 11, and the reaction vessel 12 includes at least a first opening 121, a second opening 122, and a third opening 123, each opening connecting the inside and outside of the reaction vessel 12. The gas input pipeline 13 is connected to the first opening 121. The condenser 15 is connected to the second opening 122, the receiving bottle 16 is connected to the end of the condenser 15 away from the second opening 122, the distillation column 20 is connected to the third opening 123, the inlet of the condenser 22 is connected to the end of the distillation column 20 away from the third opening 123, and one outlet returns to the distillation column 20. The vacuum pump 17 includes a first inlet 171 and a second inlet 172, etc. The first inlet 171 is connected to the condenser 15, the second inlet 172 is connected to the condenser 22, and the gas output pipeline 18 is connected to the outlet of the vacuum pump 17. In the preparation apparatus provided by this utility model, by setting the gas input pipeline 13 and the gas output pipeline 18, the stable gas can circulate in the reaction vessel 12 or the distillation column 20, which helps to control the reaction rate and improve the mass transfer effect, thereby improving the yield and purity of isocyanate.

[0033] Please see Figure 1 As shown, in one embodiment of this invention, heater 11 provides a heat source for the catalytic decomposition and preparation of isocyanate. Heater 11 can be, for example, an electric heating mantle or an oil bath.

[0034] Please see Figure 1As shown, in one embodiment of this invention, the reaction vessel 12 is disposed within the heater 11 and is used to hold the reaction raw materials. The reaction raw materials include methyl dicarboxylate, a catalyst, and a solvent. The methyl dicarboxylate includes, for example, at least one of dimethyl toluene-2,4-dicarboxylate (TDC), methylene diphenyl dicarboxylate (MDC), or dimethyl-hexane-1,6-dicarboxylate (HDC). The catalyst includes, for example, at least one of zinc oxide, bismuth oxide, cerium oxide, iron oxide, or zinc powder. The solvent includes, for example, at least one of dimethyl phthalate, dibutyl phthalate, dioctyl phthalate, dioctyl sebacate, liquid paraffin, or naphthenic oil. Specifically, after the reaction raw materials are heated by the heater 11, the methyl dicarboxylate is catalytically decomposed into isocyanate products and methanol byproducts. The heating temperature is, for example, 220℃-260℃. When methyl dicarboxylate includes TDC, the isocyanate product includes toluene diisocyanate (TDI). When methyl dicarboxylate includes MDC, the isocyanate product includes methylene diphenyl diisocyanate (MDI). When methyl dicarboxylate includes HDC, the isocyanate product includes hexamethylene diisocyanate (HDI).

[0035] Please see Figure 1 As shown, in one embodiment of this utility model, the reactor 12 includes at least three openings, each opening connecting the inside and outside of the reactor 12. In this embodiment, the reactor 12 includes, for example, a first opening 121, a second opening 122, and a third opening 123.

[0036] Please see Figure 1 As shown, in one embodiment of this utility model, the gas input pipeline 13 is connected to the first opening 121 for supplying a stabilizing gas into the reaction vessel 12. The stabilizing gas includes, for example, at least one of nitrogen and an inert gas, and the inert gas includes, for example, at least one of helium and argon.

[0037] Please see Figure 1As shown, in one embodiment of this invention, the condenser 15 is connected to the second opening 122. Specifically, methanol, a byproduct generated from the catalytic decomposition reaction of the reactants in the reactor 12, enters the condenser 15 and is cooled into a liquid, while the isocyanate product remains in the reactor 12, thereby achieving the separation of the isocyanate product and the methanol byproduct. The condenser 15 can be, for example, a serpentine condenser, a spherical condenser, or a straight condenser.

[0038] Please see Figure 1 As shown, in one embodiment of this utility model, a switching valve 14 is provided between the condenser 15 and the second opening 122 to control whether the methanol by-product in the reactor 12 flows to the condenser 15.

[0039] Please see Figure 1 As shown, in one embodiment of the present invention, the receiving bottle 16 is connected to the end of the condenser tube 15 away from the second opening 122 to hold the methanol byproduct cooled by the condenser tube 15.

[0040] Please see Figure 1 As shown, in one embodiment of this utility model, a vacuum pump 17 is also provided on one side of the condenser tube 15. The vacuum pump 17 includes at least a first inlet 171, a second inlet 172, and an outlet, etc. The first inlet 171 is connected to the condenser tube 15. Specifically, the first inlet 171 is connected to the end of the condenser tube 15 near the receiving bottle 16.

[0041] Please see Figure 1As shown, in one embodiment of this invention, the outlet of the vacuum pump 17 is connected to a gas output pipe 18. Specifically, the gas input pipe 13 delivers stabilizing gas into the reactor 12, carrying away the residual heat generated by the catalytic decomposition reaction within the reactor 12. The stabilizing gas is heated and then flows out of the preparation device through the switching valve 14, condenser 15, first inlet 171, and gas output pipe 18 for reuse. This cycle repeats continuously, allowing the stabilizing gas to circulate continuously within the reactor 12, condenser 15, and vacuum pump 17. By setting up the gas input pipe 13, vacuum pump 17, and gas output pipe 18, the stabilizing gas continuously circulates within the reactor 12. The stabilizing gas can carry away the reaction heat within the reactor 12, reducing the problem of incomplete material decomposition or aggravated side reactions caused by local overheating. This improves the yield and selectivity of the isocyanate product and also allows for the recovery and reuse of reaction heat, saving energy. Simultaneously, the introduction of stabilizing gas disturbs the gas in the reaction system. This disturbance disrupts the boundary layer at the gas-liquid or gas-solid interface, reducing mass transfer resistance and accelerating the diffusion rate of reactants and products between phases, thereby improving mass transfer efficiency. It also improves the flow state of the fluid within the reaction system, resulting in a more uniform fluid distribution in the reactor 12. This facilitates sufficient contact between methyl dicarboxylate and the catalyst, enhancing mass transfer efficiency and promoting the catalytic decomposition reaction. Furthermore, the introduction of stabilizing gas dilutes the concentration of reactants within the reactor 12. A decrease in reactant concentration alters the reaction rate; therefore, by adjusting the flow rate of the stabilizing gas, the degree of concentration reduction can be precisely controlled, enabling effective control of the reaction rate. In addition, the introduction of stabilizing gas can adjust the initial vacuum level in the reactor 12 and condenser 15 to, for example, 50-100 kPa, ensuring the normal progress of the catalytic decomposition reaction.

[0042] Please see Figure 1As shown, in one embodiment of this utility model, the distillation column 20 is connected to the third opening 123. Specifically, in the reactor 12, the reactants undergo a catalytic decomposition reaction to generate isocyanate products and methanol byproducts. The methanol byproducts flow out of the reactor 12 through the condenser 15, while the isocyanate products remain in the reactor 12. However, unreacted reactants still remain in the reactor 12. Therefore, by setting up the distillation column 20, the isocyanate products and reactants in the reactor 12 are separated, thereby achieving the purpose of purifying the isocyanate products. The distillation column 20 is, for example, a packed column, including a column body 201, packing 202, and a top 203. One end of the column body 201 is connected to the third opening 123, and the other end is connected to the top 203. The packing 202 is filled inside the column body 201. Specifically, after the reactants and isocyanate products in reactor 12 are naturally cooled to, for example, 120°C-160°C, the second vacuum level in distillation column 20 is adjusted to 1KPa-10KPa. The isocyanate products are then naturally evaporated into gas and rise sequentially into column body 201 and column top 203. By directly connecting distillation column 20 to the third opening 123, the catalytic decomposition reaction and distillation process are combined. This eliminates the need to transfer the products from reactor 12 and to reheat the reactants and isocyanate products. The products are directly distilled and purified in situ through distillation column 20. This effectively prevents isocyanate polymerization during secondary heating, improving its purity and yield. Furthermore, it reduces energy consumption, further achieving energy conservation and maximizing economic benefits.

[0043] Please see Figure 1 As shown, in one embodiment of this utility model, a shut-off valve 19 is provided between the distillation column 20 and the reactor 12 to control whether the isocyanate product gas in the reactor 12 flows to the distillation column 20.

[0044] Please see Figure 1 As shown, in one embodiment of this utility model, a temperature detection unit 21 is provided inside the top 203 of the tower. One end of the temperature detection unit 21 extends into the top 203 of the tower, and the other end extends outside the top 203 of the tower. By providing the temperature detection unit 21, the temperature of the top 203 of the tower can be monitored, thereby monitoring the purity of the isocyanate extracted from the top 203 of the tower.

[0045] Please see Figure 1As shown, in one embodiment of this utility model, the inlet of the condenser 22 is connected to the end of the distillation column 20 away from the third opening 123, and the outlet includes at least three outlets, such as the first outlet 221, the second outlet 222, and the third outlet 223. The first outlet 221 returns to the distillation column 20. Specifically, the inlet of the condenser 22 is connected to the end of the column top 203 away from the column body 201, and the first outlet 221 is connected to the end of the column top 203 near the column body 201. By setting up the condenser 22, when purifying the isocyanate product, the switching valve 14 is closed and the shut-off valve 19 is opened. The isocyanate product gas rises sequentially into the column body 201, the column top 203, and the condenser 22. After the isocyanate product gas is condensed into liquid in the condenser 22, part of the liquid flows back to the column top 203 and the column body 201, where it comes into countercurrent contact with the rising isocyanate product gas in the column body 201 for mass transfer.

[0046] Please see Figure 1 As shown, in one embodiment of this invention, the inlet of the product collection tank 24 is connected to the second outlet 222. Specifically, the condenser 22 sends the condensed isocyanate product into the product collection tank 24 for storage.

[0047] Please see Figure 1 As shown, in one embodiment of this invention, a reflux regulating valve 23 is provided between the product collection tank 24, the condenser 22, and the top of the tower 203. By providing the reflux regulating valve 23, the reflux ratio can be adjusted to improve the purity of the isocyanate product in the product collection tank 24. The reflux ratio is, for example, (10-1):1.

[0048] Please see Figure 1As shown, in one embodiment of this utility model, the third outlet 223 is connected to the second inlet 172 of the vacuum pump 17. In this embodiment, the third outlet 223 and the outlet of the product collection tank 24 are connected in parallel and then connected to the second inlet 172. Specifically, the stabilizing gas enters the reactor 12 through the gas inlet pipe 13. After passing through the shut-off valve 19, distillation column 20, condenser 22, and product collection tank 24, part of it flows out of the condenser 22 from the third outlet 223 and reaches the second inlet 172, while the other part flows out of the product collection tank 24 from the outlet and reaches the second inlet 172, enters the vacuum pump 17, and then enters the gas outlet pipe 18 through the outlet of the vacuum pump 17, flowing out of the preparation device. This cycle repeats continuously, allowing the stabilizing gas to continuously circulate within the reactor 12, distillation column 20, condenser 22, product collection tank 24, and vacuum pump 17. This achieves the purpose of controlling the second vacuum degree in the mass transfer separation process within the distillation column 20, thereby lowering the boiling point of the isocyanate product. Secondary heating of the isocyanate product in the reactor 12 is unnecessary; the isocyanate product in the reactor 12 can naturally evaporate into gas for separation, thus reducing the energy consumption of mass transfer separation. The second vacuum degree is, for example, 1 kPa-10 kPa. Furthermore, during the mass transfer separation process, a stabilizing gas is introduced into the reactor 12 and the distillation column 20. On the one hand, this can blow out volatile impurities in the system. Under the action of the stabilizing gas flow, the impurities leave the system with the gas flow, thereby achieving the separation of impurities from isocyanate products. On the other hand, it will change the phase equilibrium relationship of the system, causing the distribution of impurities between the gas phase and the liquid or solid phase to change, prompting more impurities to enter the gas phase and be discharged with the stabilizing gas flow, thus achieving the purpose of separating impurities.

[0049] Please see Figure 1 As shown, in one embodiment of this utility model, the preparation device further includes a differential pressure gauge 25. The differential pressure gauge 25 is installed between the parallel main line between the outlet of the product collection tank 24 and the third outlet 223, and between the second inlet 172, to measure the vacuum degree between the reactor 12, the distillation column 20, the condenser 22 and the product collection tank 24. Based on the measured vacuum degree, the vacuum pump 17 can be adjusted to change the vacuum degree, thereby further reducing the boiling point of the isocyanate product and reducing the energy consumption of mass transfer separation.

[0050] To further illustrate the isocyanate preparation apparatus provided by this invention, the following details the steps for preparing isocyanate using the apparatus.

[0051] Please see Figure 1As shown, 10g of methyl dicarboxylate, 1g of catalyst, and 500mL of solvent are mixed and added to reactor 12. The shut-off valve 19 is closed, the switching valve 14 is opened, and N2 is introduced into reactor 12 through gas inlet pipe 13. The power of vacuum pump 17 is adjusted to achieve a first vacuum level of 50kPa-100kPa within reactor 12. N2 flows out of the preparation apparatus through gas outlet pipe 18. Next, heater 11 is started to heat reactor 12 to 220℃-260℃, and the reaction is carried out for 1-6 hours. At this time, isocyanate produced by catalytic decomposition is obtained in reactor 12, and the byproduct methanol is collected in receiving bottle 16 after cooling through condenser 15. Afterwards, open the shut-off valve 19 and close the switching valve 14. After the material in the reactor 12 cools naturally to 120℃-160℃, adjust the power of the vacuum pump 17 to make the second vacuum degree in the distillation column 20 1kPa-10kPa. The distillation column 20 purifies the isocyanate in the reactor 12. The isocyanate in the reactor 12 is evaporated into gas and enters the distillation column 20 and condenser 22. The condenser 22 condenses the gas into isocyanate liquid. The reflux ratio is controlled to be 10:1-1:1 by the reflux regulating valve 23. Part of the isocyanate liquid is refluxed back into the distillation column 20, and the other part of the isocyanate liquid is collected by the product collection tank 24.

[0052] Please see Figure 1As shown, in one embodiment of this invention, when methyl dicarboxylate is TDC, the catalyst is ZnO, the solvent is dimethyl phthalate, the first vacuum degree is 50 kPa, the temperature of the heating reactor 12 is 230°C, the reaction time is 2 h, the temperature of the material under natural cooling is 120°C, the second vacuum degree is 2 kPa, and the reflux ratio is 5:1, TDI product with a purity of 98.9 wt% is collected in the product collection tank 24. In another embodiment, when methyl dicarboxylate is MDC, the catalyst is ZnO, the solvent is dimethyl phthalate, the first vacuum degree is 50 kPa, the temperature of the heating reactor 12 is 260°C, the reaction time is 3 h, the temperature of the material under natural cooling is 150°C, the second vacuum degree is 2 kPa, and the reflux ratio is 5:1, MDI product with a purity of 99.2 wt% is collected in the product collection tank 24. In another embodiment, when the methyl dicarboxylate is HDC, the catalyst is ZnO, the solvent is dimethyl phthalate, the first vacuum degree is 50 kPa, the temperature of the heating reactor 12 is 240°C, the reaction time is 2 h, the temperature of the material after natural cooling is 120°C, the second vacuum degree is 2 kPa, and the reflux ratio is 5:1, HDI product with a purity of 99.6 wt% is collected in the product collection tank 24. In another embodiment, when the methyl dicarboxylate is TDC, the catalyst is Bi2O3, the solvent is dimethyl phthalate, the first vacuum degree is 60 kPa, the temperature of the heating reactor 12 is 240°C, the reaction time is 1 h, the temperature of the material after natural cooling is 130°C, the second vacuum degree is 2 kPa, and the reflux ratio is 10:1, TDI product with a purity of 89.2 wt% is collected in the product collection tank 24. In another embodiment, when methyl dicarboxylate is MDC, catalyst is ZnO, solvent is dioctyl sebacate, first vacuum degree is 55 kPa, heating temperature of reactor 12 is 245°C, reaction time is 2 h, natural cooling temperature of material is 160°C, second vacuum degree is 2 kPa, and reflux ratio is 9:1, MDI product is collected in product collection tank 24 with a purity of 90.3 wt%. In another embodiment, when methyl dicarboxylate is HDC, catalyst is ZnO, solvent is dioctyl phthalate, first vacuum degree is 50 kPa, heating temperature of reactor 12 is 230°C, reaction time is 3 h, natural cooling temperature of material is 130°C, second vacuum degree is 2 kPa, and reflux ratio is 8:1, HDI product is collected in product collection tank 24 with a purity of 92.1 wt%.

[0053] In summary, this invention provides an apparatus for preparing isocyanates. By improving the apparatus, polymerization of isocyanates upon heating can be effectively avoided, thereby increasing the purity and yield of isocyanates, saving on heating processes, and reducing energy consumption. Furthermore, the apparatus proposed in this invention introduces a stabilizing gas, which helps control the reaction rate and mass transfer effect, enabling efficient decomposition and precise separation at lower temperatures and pressures, thus improving the yield and selectivity of isocyanates.

[0054] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An apparatus for preparing isocyanate, characterized in that, At least including: heater; A reaction vessel is disposed inside the heater, and the reaction vessel includes at least a first opening, a second opening and a third opening, each of the openings communicating with the inside and outside of the reaction vessel. A gas inlet pipe is connected to the first opening; The condenser tube is connected to the second opening; A receiving bottle is connected to the end of the condenser tube furthest from the second opening; The distillation column is connected to the third opening; A condenser, with its inlet connected to the end of the distillation column away from the third opening, and an outlet returning to the distillation column; A vacuum pump, comprising at least a first inlet and a second inlet, wherein the first inlet is connected to the condenser tube and the second inlet is connected to the condenser; and The gas output pipeline is connected to the outlet of the vacuum pump.

2. The preparation apparatus according to claim 1, characterized in that, The condenser includes at least a first outlet, a second outlet, and a third outlet, the first outlet being connected to the distillation column.

3. The preparation apparatus according to claim 2, characterized in that, The preparation apparatus also includes a product collection tank, and the second outlet is connected to the inlet of the product collection tank.

4. The preparation apparatus according to claim 3, characterized in that, The third outlet and the outlet of the product collection tank are connected in parallel and then connected to the second inlet.

5. The preparation apparatus according to claim 4, characterized in that, The preparation apparatus further includes a differential pressure gauge, which is disposed between the parallel main line between the outlet of the product collection tank and the third outlet, and between the second inlet.

6. The preparation apparatus according to claim 1, characterized in that, The preparation apparatus further includes a switching valve disposed between the condenser and the second opening.

7. The preparation apparatus according to claim 1, characterized in that, The preparation apparatus also includes a shut-off valve, which is disposed between the distillation column and the reaction vessel.

8. The preparation apparatus according to claim 1, characterized in that, The distillation column includes at least a column body, one end of which is connected to the third opening.

9. The preparation apparatus according to claim 8, characterized in that, The distillation column also includes a column top, which is connected to the other end of the column body.

10. The preparation apparatus according to claim 9, characterized in that, The preparation apparatus further includes a temperature detection unit, one end of which extends into the top of the tower and the other end extends out of the top of the tower.

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