Toluene recovery device in organic synthesis

Abstract

The utility model provides a toluene recovery device in organic synthesis. The toluene recovery device comprises a reaction kettle, a desolventizing kettle, a first heat exchanger, a second heat exchanger and a tail gas treatment device which are sequentially connected in series, the desolventizing kettle is also connected with a crude product collecting tank; the second heat exchanger is sequentially connected with the solvent storage tank, the first heat exchanger and the reaction kettle. According to the device, the first heat exchanger is arranged, methylbenzene condensed by the second heat exchanger serves as a heat exchange medium, methylbenzene steam distilled out of the desolventizing kettle is cooled, and meanwhile liquid methylbenzene is preheated through the methylbenzene steam. Heat of methylbenzene steam in the methylbenzene desolventizing and recycling process is utilized, and the defect that energy is wasted due to the fact that methylbenzene steam is directly condensed when reaction liquid is desolventized traditionally is overcome.

Description

Technical Field

[0001] The present application relates to the technical field of chemical synthesis solvent recovery, and in particular to a toluene recovery device in organic synthesis. Background Art

[0002] Toluene is an organic compound with the chemical formula C7H8. It is a colorless, volatile liquid with a special aromatic smell and belongs to the aromatic hydrocarbon family. Toluene is an important chemical raw material and can be used to make spray paint, explosives, pesticides, benzoic acid, dyes, synthetic resins and polyester. Toluene can also be used as a solvent and is also a component of gasoline.

[0003] In chemical synthesis reactions, toluene is often used as a solvent. After the reaction is completed, the toluene in the reaction solution needs to be separated from the reaction product to recover the toluene. The existing method for recovering toluene in the reaction solution is mainly a distillation method, that is, the reaction solution is heated to the boiling point of toluene, the toluene is boiled and vaporized to form toluene vapor which is evaporated from the reaction solution, and then the toluene vapor is condensed to achieve toluene recovery.

[0004] However, the existing method of recovering toluene is to directly condense the toluene vapor using circulating water heat exchange for recovery. Although this method can recover toluene, it fails to utilize the heat in the toluene vapor, thus resulting in a waste of energy. Utility Model Content

[0005] The present application provides a toluene recovery device in organic synthesis, which is used to solve the problem of energy waste caused by failure to utilize the heat in toluene vapor when separating and recovering toluene by distillation.

[0006] The present application provides a toluene recovery device in organic synthesis, comprising a reaction kettle, a desolventizing kettle, a first heat exchanger, a second heat exchanger and a tail gas treatment device connected in series in sequence;

[0007] The desolventizing kettle is also connected to the crude product collecting tank;

[0008] The second heat exchanger is also connected to the solvent storage tank, the first heat exchanger and the reactor in sequence;

[0009] The desolventizing kettle is connected to the gas input end of the shell side of the first heat exchanger, the gas output end of the shell side of the first heat exchanger is connected to the shell side input end of the second heat exchanger, and the shell side output end of the second heat exchanger is connected to the tail gas treatment device;

[0010] The solvent storage tank is connected to the tube side input end of the first heat exchanger, and the tube side output end of the first heat exchanger and the shell side liquid output end of the first heat exchanger are connected to the material input end of the reactor.

[0011] Optionally, a first valve is provided between the second heat exchanger and the tail gas treatment device;

[0012] The second heat exchanger is connected to the suction end of the vacuum pump through the second valve; the exhaust end of the vacuum pump is connected to the tail gas treatment device.

[0013] Optionally, the reactor comprises a reactor body and an upper head, and the reactor body and the upper head are connected via a heat exchange cylinder;

[0014] A first stirring paddle is arranged in the kettle body and passes through the upper head;

[0015] The upper head is provided with a feeding port, which is connected to the shell side output end of the first heat exchanger.

[0016] Optionally, a first heat exchange tube is provided in the heat exchange cylinder;

[0017] The first heat exchange tube penetrates from a position of the heat exchange cylinder close to the kettle body, and after being coiled and folded in multiple layers in the heat exchange cylinder, passes out from a position of the heat exchange cylinder close to the upper head.

[0018] Optionally, the desolventizing kettle comprises a desolventizing kettle body;

[0019] A second stirring paddle is arranged in the desolventizing kettle body;

[0020] The second stirring paddle includes a rotating shaft and a paddle, and the paddle is provided with a plurality of through holes;

[0021] The rotating shaft is also connected to a plurality of scrapers through a plurality of connecting rods, and one side of the scrapers is in contact with the inner wall of the desolventizing kettle body;

[0022] The scraper is arranged at an acute angle to the vertical surface.

[0023] Optionally, the first heat exchanger is arranged horizontally and comprises a cylinder; the cylinder comprises a heat exchange shell and a material receiving shell;

[0024] The heat exchange shell is closed by the heads at both ends, and the heat exchange shell and the heads are separated by a tube sheet. A second heat exchange tube is arranged in the heat exchange shell, and the second heat exchange tube passes through the tube sheet to connect the heads at both ends of the heat exchange shell;

[0025] The material receiving shell is arranged on the lower side of the heat exchange shell and is communicated with the heat exchange shell;

[0026] An air inlet is provided on the side of the material receiving shell, a condensate outlet is provided on the bottom, an air outlet is provided on the upper side of the heat exchange shell, and the condensate outlet is also connected to the material input end of the reactor.

[0027] Optionally, the tail gas treatment device is an absorption tower or an incinerator.

[0028] The present application provides a toluene recovery device in organic synthesis, which cools the toluene vapor distilled from the desolventizing kettle by setting a first heat exchanger and using the toluene condensed by the second heat exchanger as the heat exchange medium, and preheats the liquid toluene by using the toluene vapor. The device of the present application utilizes the heat of the toluene vapor in the toluene desolventizing recovery process through the coordinated use of the above-mentioned equipment, thereby overcoming the drawback of energy waste caused by the traditional direct condensation of toluene vapor. In addition, the amount of condensed water can be saved, which has the beneficial effect of reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 A schematic diagram of a toluene recovery device in organic synthesis provided in one embodiment of the present application;

[0031] Figure 2 A schematic diagram of a toluene recovery device in organic synthesis provided in another embodiment of the present application;

[0032] Figure 3 A schematic diagram of the structure of a reactor provided in one embodiment of the present application;

[0033] Figure 4 A schematic diagram of the structure of a heat exchange cylinder provided in one embodiment of the present application;

[0034] Figure 5 A schematic diagram of the structure of a desolventizing kettle provided in one embodiment of the present application;

[0035] Figure 6 A schematic structural diagram of a first heat exchanger provided in one embodiment of the present application.

[0036] Description of reference numerals:

[0037] 1. Reactor; 2. Desolventizing kettle; 3. First heat exchanger; 4. Second heat exchanger; 5. Tail gas treatment device; 6. Vacuum pump; 11. Kettle body; 12. Upper head; 13. Heat exchange cylinder; 14. First stirring paddle; 20. Crude product collection tank; 21. Desolventizing kettle body; 22. Second stirring paddle; 23. Scraper; 31. Cylinder body; 32. Head; 33. Tube sheet; 34. Second heat exchange tube; 40. Solvent storage tank; 100. First valve; 101. Feeding port; 131. First heat exchange tube; 200. Second valve; 221. Rotating shaft; 222. Paddle; 231. Connecting rod; 301. Air inlet; 302. Condensate outlet; 303. Air outlet. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0039] like Figure 1 As shown, the present application provides a toluene recovery device in organic synthesis, comprising a reaction kettle 1, a desolventizing kettle 2, a first heat exchanger 3, a second heat exchanger 4 and a tail gas treatment device 5 connected in series in sequence;

[0040] The desolventizing kettle 2 is also connected to the crude product collecting tank 20;

[0041] The second heat exchanger 4 is also connected to the solvent storage tank 40, the first heat exchanger 3 and the reactor 1 in sequence;

[0042] The desolventizing kettle 2 is connected to the gas input end of the shell side of the first heat exchanger 3, the gas output end of the shell side of the first heat exchanger 3 is connected to the shell side input end of the second heat exchanger 4, and the shell side output end of the second heat exchanger 4 is connected to the tail gas treatment device 5;

[0043] The solvent storage tank 40 is connected to the tube side input end of the first heat exchanger 3 , and the tube side output end of the first heat exchanger 3 and the shell side liquid output end of the first heat exchanger 3 are connected to the material input end of the reactor 1 .

[0044] The present application takes the process of producing the pesticide propanil (chemical name 3,4-dichlorophenylpropionamide) as an example. Propanil is synthesized using 3,4-dichloroaniline as a starting material. The first step of the reaction is to use 3,4-dichloroaniline and propionyl chloride as substrates and toluene as a solvent for propionylation at 100-110°C. After the reaction is completed, the toluene in the reaction needs to be desolventized and evaporated and then recycled. The traditional method is to directly recover the evaporated toluene by condensing it through circulating water heat exchange. Although toluene is recovered in this method, the heat in the toluene vapor is not fully recovered, which will lead to energy waste.

[0045] When in use, the synthesis reaction using toluene as the reaction solvent is carried out in the reactor 1. During the reaction, the reaction system in the reactor is heated by a heat exchange device (such as a heat exchange jacket) in the reactor 1 to allow the reaction to proceed.

[0046] After the reaction is completed, the reaction liquid is transferred from the reactor 1 to the desolventizing kettle 2 for normal pressure desolventizing (distillation). The reaction liquid is further heated in the desolventizing kettle 2 so that the reaction liquid reaches the boiling point of toluene, and the toluene in the reaction liquid is evaporated out of the desolventizing kettle 2. The toluene vapor evaporated in the desolventizing kettle 2 enters the first heat exchanger 3 for condensation.

[0047] The toluene vapor evaporated from the desolventizing kettle 2 exchanges heat with the liquid toluene from the solvent storage tank 40 in the tube side from the shell side of the first heat exchanger 3. The toluene in the tube side is preheated and then transferred to the reactor 1 (in actual use, multiple reactors 1 are arranged in parallel, and the preheated toluene can be input into other reactors 1 that need a solvent) for use as a solvent; and the toluene vapor is condensed and input into the reactor 1 that needs a solvent from the liquid output end of the first heat exchanger 3 for use.

[0048] The steam and gas that cannot be condensed in the first heat exchanger 3 are output from the shell side gas output end of the first heat exchanger 3, and then enter the tube side of the second heat exchanger 4 for further condensation. The heat exchange medium flowing in the shell side of the second heat exchanger 4 is circulating water or 0-5°C frozen brine. The condensed liquid, that is, toluene, will be transferred to the solvent storage tank 40 for subsequent use. For example, it is input into the first heat exchanger 3 for use as a heat exchange medium.

[0049] The gas that cannot be condensed in the second heat exchanger 4 (ie, the non-condensable gas) will enter the tail gas treatment device 5 for treatment (it can be absorbed or directly incinerated as a harmless treatment depending on whether the tail gas needs to be recovered).

[0050] The present application provides a toluene recovery device in organic synthesis, which cools the toluene vapor distilled from the desolventizing kettle 2 by setting a first heat exchanger 3 and using the toluene condensed by the second heat exchanger 4 as a heat exchange medium, and preheats the liquid toluene by using the toluene vapor. The device of the present application utilizes the heat of the toluene vapor in the toluene desolventizing recovery process through the coordinated use of the above-mentioned equipment, thereby overcoming the drawback of energy waste caused by the traditional direct condensation of toluene vapor. In addition, the amount of condensed water can be saved, which has the beneficial effect of reducing production costs.

[0051] like Figure 2 As shown, optionally, a first valve 100 is provided between the second heat exchanger 4 and the exhaust gas treatment device 5;

[0052] The second heat exchanger 4 is connected to the suction end of the vacuum pump 6 through the second valve 200 ; the exhaust end of the vacuum pump 6 is connected to the exhaust gas treatment device 5 .

[0053] In actual production, when no more toluene evaporates at a temperature under normal pressure conditions (to avoid the reaction product being destroyed by heat, the temperature cannot be further increased), since some toluene still remains in the system, decompression desolventizing (distillation) should be performed at this time. During decompression desolventizing, close the first valve 100, open the second valve 200 and turn on the vacuum pump 6 to suction and decompress the pipe side of the second heat exchanger 4. The toluene vapor evaporated during the decompression desolventizing process is the same as the processing path of the toluene vapor during the normal pressure desolventizing process, which will not be repeated here. The non-condensable gas output from the second heat exchanger 4 during the decompression desolventizing process enters the tail gas treatment device 5 from the vacuum pump 6 for treatment.

[0054] When no more toluene evaporates during the reduced pressure desolventizing, continue to ensure vacuum for a period of time (for example, 10 to 15 minutes), then close the second valve 200 and the vacuum pump 6, and then break the vacuum. After the air pressure inside and outside the desolventizing kettle 2 is balanced, the product in the desolventizing kettle 2 is output to the crude product collection tank 20 for subsequent purification treatment.

[0055] like Figure 3 As shown, optionally, the reactor 1 includes a reactor body 11 and an upper head 12, and the reactor body 11 and the upper head 12 are connected via a heat exchange cylinder 13;

[0056] A first stirring paddle 14 is disposed in the kettle body 11, and the first stirring paddle 14 is disposed through the upper head 12;

[0057] The upper head 12 is provided with a feed port 101 , and the feed port 101 is connected to the liquid output end of the shell side of the first heat exchanger 3 .

[0058] In the present application, the heat exchange cylinder 13 is provided to condense the solvent vapor generated by heating during the reaction process, thereby playing a role of reflux.

[0059] like Figure 4 As shown, optionally, a first heat exchange tube 131 is provided in the heat exchange cylinder 13;

[0060] The first heat exchange tube 131 penetrates into the heat exchange cylinder 13 from a position close to the kettle body 11 , and after being twisted and folded in multiple layers inside the heat exchange cylinder 13 , passes out from a position close to the upper head 12 of the heat exchange cylinder 13 .

[0061] In the present application, the reaction system in the reactor is heated by a heat exchange device (such as a heat exchange jacket) in the reactor 1 during the reaction, and the first stirring paddle 14 is turned on to stir the reaction. During the reaction, circulating cooling water is introduced into the first heat exchange tube 131, and toluene is evaporated during the heating process. The toluene condenses on the first heat exchange tube 131 and falls into the reaction system, thereby preventing the solvent from escaping due to the reaction heating and affecting the reaction process.

[0062] In the present application, in one feasible manner, a plurality of first heat exchange tubes 131 may be arranged in the heat exchange cylinder 13 to ensure the condensation effect. In one feasible manner, heat exchange fins may be arranged outside the first heat exchange tubes 131 to improve the heat exchange effect.

[0063] like Figure 5 As shown, optionally, the desolventizing kettle 2 includes a desolventizing kettle body 21;

[0064] A second stirring paddle 22 is provided in the desolventizing kettle body 21;

[0065] The second stirring paddle 22 includes a rotating shaft 221 and a paddle 222, and a plurality of through holes are formed on the paddle 222;

[0066] The rotating shaft 221 is also connected to a plurality of scrapers 23 via a plurality of connecting rods 231, and one side of the scraper 23 abuts against the inner wall of the desolventizing kettle body 21;

[0067] The scraper 23 is arranged at an acute angle to the vertical surface.

[0068] In the present application, when in use, the reaction liquid is transferred from the reactor 1 to the desolventizing kettle 2. The reaction liquid is further heated in the desolventizing kettle 2, so that the reaction liquid reaches the boiling point of toluene, and the toluene in the reaction liquid is evaporated out of the desolventizing kettle 2. During the desolventizing process, the second stirring paddle 22 is operated to stir the reaction liquid. When the multiple through holes on the blade 222 rotate with the blade 222, the stirring of the blade 222 will stir up small bubbles in the reaction liquid, thereby preventing the occurrence of the undesirable phenomenon of bumping during the desolventizing process. And the scraper 23 connected by the connecting rod 231 on the rotating shaft 221, during the rotation of the rotating shaft 221, scrapes off the residual reaction liquid on the inner wall of the desolventizing kettle body 21 to reduce the residue of the reaction liquid (especially when the solvent in the reaction liquid is gradually reduced, the amount of the product adhering to the inner wall of the kettle will increase, and the scraper 23 can scrape off these substances to reduce the waste of materials), and the toluene vapor evaporated in the desolventizing kettle 2 enters the first heat exchanger 3 and condenses.

[0069] like Figure 6 As shown, optionally, the first heat exchanger 3 is arranged horizontally and includes a cylinder 31; the cylinder 31 includes a heat exchange shell and a material receiving shell;

[0070] The heat exchange shell is closed by the heads 32 at both ends. The heat exchange shell and the heads 32 are separated by a tube sheet 33. A second heat exchange tube 34 is arranged in the heat exchange shell. The second heat exchange tube 34 passes through the tube sheet 33 to connect the heads 32 at both ends of the heat exchange shell.

[0071] The material receiving shell is arranged on the lower side of the heat exchange shell and is communicated with the heat exchange shell;

[0072] An air inlet 301 is provided on the side of the material receiving shell, a condensate outlet 302 is provided on the bottom, an air outlet 303 is provided on the upper side of the heat exchange shell, and the condensate outlet 302 is also connected to the material input end of the reactor 1 .

[0073] The toluene vapor evaporated from the desolventizing kettle 2 enters the shell side of the first heat exchanger 3 from the air inlet 301 of the barrel 31 of the first heat exchanger 3, and exchanges heat with the toluene from the solvent storage tank 40 in the second heat exchange tube 34. The toluene in the second heat exchange tube 34 is preheated and then transferred to the reactor 1 (in actual use, multiple reactors 1 are arranged in parallel, and the preheated toluene can be input into other reactors 1 that need solvents) for use as a solvent; while the toluene vapor is condensed and falls into the receiving shell of the barrel 31, and the condensed toluene is input into the reactor 1 that needs solvents from the condensate outlet 302 at the bottom of the receiving shell for use. The steam and gas that failed to condense in the first heat exchanger 3 are output from the air outlet 303 on the heat exchange shell, and then enter the tube side of the second heat exchanger 4 for further condensation.

[0074] Optionally, the tail gas treatment device 5 is an absorption tower or an incinerator.

[0075] In the present application, the tail gas treatment device 5 can be provided with an absorption tower or an incinerator according to actual needs. When it contains substances that need to be recycled or substances that are not suitable for incineration, such as hydrogen chloride produced during the propionylation process of 3,4-dichloroaniline in the present application, an absorption tower can be provided as the tail gas treatment device 5 to absorb hydrogen chloride and produce hydrochloric acid as a by-product. When the treated tail gas does not need to be recycled, an incinerator can be provided as the tail gas treatment device 5, and the tail gas can be passed into the incinerator for incineration for harmless treatment.

[0076] A toluene recovery device in organic synthesis, the working process of which is as follows:

[0077] When in use, the synthesis reaction using toluene as the reaction solvent is carried out in the reactor 1. During the reaction, the reaction system in the reactor is heated by the heat exchange device (such as a heat exchange jacket) in the reactor 1, and the first stirring paddle 14 is turned on to stir the reaction. During the reaction, circulating cooling water is introduced into the first heat exchange tube 131. During the heating process, toluene is evaporated, and the toluene condenses on the first heat exchange tube 131 when it goes up and encounters the winding and folded first heat exchange tube 131, and then falls into the reaction system, thereby preventing the solvent from escaping due to the reaction heating and affecting the reaction process.

[0078] After the reaction, the reaction liquid is transferred from the reactor 1 to the desolventizing reactor 2, and desolventizing (distillation) is first performed at normal pressure. During the desolventizing at normal pressure, the second valve 200 is closed and the first valve 100 is opened. The reaction liquid is further heated in the desolventizing reactor 2, so that the reaction liquid reaches the boiling point of toluene, and the toluene in the reaction liquid is evaporated out of the desolventizing reactor 2. During the desolventizing process, the second stirring paddle 22 is operated to stir the reaction liquid. When the multiple through holes on the paddle 222 rotate with the paddle 222, the stirring of the paddle 222 will stir up fine bubbles in the reaction liquid, thereby preventing the occurrence of adverse phenomena such as violent boiling during the desolventizing process. In addition, the scraper 23 connected to the rotating shaft 221 by the connecting rod 231 scrapes off the residual reaction liquid on the inner wall of the desolventizing kettle body 21 to reduce the residual reaction liquid during the rotation of the rotating shaft 221 (especially when the solvent in the reaction liquid gradually decreases, the amount of product adhering to the inner wall of the kettle will increase, and the scraper 23 can scrape off these substances to reduce material waste). The toluene vapor evaporated in the desolventizing kettle 2 enters the first heat exchanger 3 for condensation.

[0079] The toluene vapor evaporated from the desolventizing kettle 2 enters the shell side of the first heat exchanger 3 from the air inlet 301 of the cylinder 31 of the first heat exchanger 3, exchanges heat with the toluene from the solvent storage tank 40 in the second heat exchange tube 34, and the toluene in the second heat exchange tube 34 is preheated, and then transferred to the reactor 1 (in actual use, multiple reactors 1 are arranged in parallel, and the preheated toluene can be input into other reactors 1 that need a solvent) for use as a solvent; while the toluene vapor is condensed and falls into the receiving shell of the cylinder 31, and the condensed toluene is input into the reactor 1 that needs a solvent from the condensate outlet 302 at the bottom of the receiving shell for use.

[0080] The steam and gas that cannot be condensed in the first heat exchanger 3 are output from the gas outlet 303 on the heat exchange shell, and then enter the tube side of the second heat exchanger 4 for further condensation. The heat exchange medium flowing in the shell side of the second heat exchanger 4 is circulating water or 0-5°C frozen brine. The condensed liquid, that is, toluene, will be transferred to the solvent storage tank 40 for subsequent use. For example, it is input into the first heat exchanger 3 for use as a heat exchange medium.

[0081] The gas that fails to condense in the second heat exchanger 4 (ie, the non-condensable gas) will enter the tail gas treatment device 5 through the first valve 100 for treatment (it can be absorbed or directly incinerated as a harmless treatment depending on whether the tail gas needs to be recovered).

[0082] When no more toluene evaporates at the above-mentioned normal pressure condition (to avoid the reaction product being destroyed by heat, the temperature cannot be further increased), decompression desolventizing (distillation) should be performed at this time. During decompression desolventizing, close the first valve 100, open the second valve 200 and turn on the vacuum pump 6 to suction and decompress the pipe side of the second heat exchanger 4. The treatment path of the toluene vapor evaporated during the decompression desolventizing process is the same as that of the toluene vapor during the normal pressure desolventizing process, which will not be repeated here. The non-condensable gas output from the second heat exchanger 4 during the decompression desolventizing process enters the tail gas treatment device 5 from the vacuum pump 6 for treatment.

[0083] When no more toluene evaporates during the reduced pressure desolventizing, continue to ensure vacuum for a period of time (for example, 10 to 15 minutes), then close the second valve 200 and the vacuum pump 6, and then break the vacuum. After the air pressure inside and outside the desolventizing kettle 2 is balanced, the product in the desolventizing kettle 2 is output to the crude product collection tank 20 for subsequent purification treatment.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A toluene recovery device in organic synthesis, characterized in that: It comprises a reaction kettle (1), a desolventizing kettle (2), a first heat exchanger (3), a second heat exchanger (4) and an exhaust gas treatment device (5) which are connected in series in sequence; The desolventizing kettle (2) is also connected to a crude product collecting tank (20); The second heat exchanger (4) is also connected to the solvent storage tank (40), the first heat exchanger (3) and the reaction kettle (1) in sequence; The desolventizing kettle (2) is connected to the gas input end of the shell side of the first heat exchanger (3), the gas output end of the shell side of the first heat exchanger (3) is connected to the shell side input end of the second heat exchanger (4), and the shell side output end of the second heat exchanger (4) is connected to the tail gas treatment device (5); The solvent storage tank (40) is connected to the tube side input end of the first heat exchanger (3), and the tube side output end of the first heat exchanger (3) and the shell side liquid output end of the first heat exchanger (3) are connected to the material input end of the reactor (1).

2. The toluene recovery device in organic synthesis according to claim 1, characterized in that: A first valve (100) is provided between the second heat exchanger (4) and the tail gas treatment device (5); The second heat exchanger (4) is connected to the suction end of the vacuum pump (6) via a second valve (200); the exhaust end of the vacuum pump (6) is connected to the tail gas treatment device (5).

3. The toluene recovery device in organic synthesis according to claim 1, characterized in that: The reaction kettle (1) comprises a kettle body (11) and an upper head (12), wherein the kettle body (11) and the upper head (12) are connected via a heat exchange cylinder (13); A first stirring paddle (14) is arranged in the kettle body (11), and the first stirring paddle (14) passes through the upper head (12); The upper head (12) is provided with a feeding port (101), and the feeding port (101) is connected to the shell side output end of the first heat exchanger (3).

4. The toluene recovery device in organic synthesis according to claim 3, characterized in that: A first heat exchange tube (131) is arranged in the heat exchange cylinder (13); The first heat exchange tube (131) penetrates from a position of the heat exchange cylinder (13) close to the kettle body (11), is coiled and folded in multiple layers inside the heat exchange cylinder (13), and then passes out from a position of the heat exchange cylinder (13) close to the upper head (12).

5. The toluene recovery device in organic synthesis according to claim 1, characterized in that: The desolventizing kettle (2) comprises a desolventizing kettle body (21); A second stirring paddle (22) is arranged in the desolventizing kettle body (21); The second stirring paddle (22) comprises a rotating shaft (221) and a paddle (222), and the paddle (222) is provided with a plurality of through holes; The rotating shaft (221) is also connected to a plurality of scrapers (23) via a plurality of connecting rods (231), and one side of the scraper (23) contacts the inner wall of the desolventizing kettle body (21); The scraper (23) is arranged at an acute angle with the vertical plane.

6. The toluene recovery device in organic synthesis according to claim 1, characterized in that: The first heat exchanger (3) is arranged horizontally and comprises a cylinder (31); the cylinder (31) comprises a heat exchange shell and a material receiving shell; The heat exchange shell is closed by end caps (32) at both ends, the heat exchange shell and the end caps (32) are separated by a tube sheet (33), a second heat exchange tube (34) is arranged in the heat exchange shell, and the second heat exchange tube (34) passes through the tube sheet (33) to connect the end caps (32) at both ends of the heat exchange shell; The material receiving shell is arranged on the lower side of the heat exchange shell and is communicated with the heat exchange shell; The side of the material receiving shell is provided with an air inlet (301), the bottom is provided with a condensate outlet (302), the upper side of the heat exchange shell is provided with an air outlet (303), and the condensate outlet (302) is also connected to the material input end of the reactor (1).

7. The toluene recovery device in organic synthesis according to any one of claims 1 to 6, characterized in that: The tail gas treatment device (5) is an absorption tower or an incinerator.

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