Recycle methanol separation apparatus and method in glycolysis intermediate production process

Abstract

The application discloses a methanol separation device in a production process of alcoholysis intermediates, which comprises a methanol refining unit, an aniline recovery unit and a vacuum unit. The methanol separation device is used for returning crude methanol obtained by rectifying product liquid in a production process of alcoholysis intermediates to a reaction system after removing ammonia and water by rectification, and recovering aniline, so that effective purification of methanol meeting process requirements is realized, the problem of low yield of heat-sensitive products caused by low methanol purity is solved, the problem of overpressure of a reactor is solved, long-time continuous and stable operation of the methanol separation device meeting separation of heat-sensitive product liquid in the production process of alcoholysis intermediates is realized, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic synthesis separation, and particularly relates to a circulating methanol separation device in an alcoholysis intermediate production process and a circulating methanol separation method in the alcoholysis intermediate production process. BACKGROUND

[0002] As a common chemical synthesis method, alcoholysis requires a large amount of methanol as a reactant and a solvent. Organic synthesis reactions are often affected by impurities and by-products in raw materials, resulting in a decrease in product yield and even overpressure of a reactor, thereby affecting the safe and continuous production of a device.

[0003] For the production of isocyanate by a non-phosgene method, N,N-diphenylurea (DPU) generates aniline and an important intermediate N-phenyl coumaric methyl ester in an alcoholysis step. N,N-diphenylurea (DPU) has a high melting point (≥220℃) and a melting point almost the same as a decomposition temperature. In order to solve the problem of continuous transportation of N,N-diphenylurea (DPU), an excess of aniline and urea are reacted, and unreacted aniline is used as a solvent under the condition of not less than 200℃. In the transportation process, aniline can dissolve part of ammonia, and this part of ammonia can be dissolved in methanol after the alcoholysis reaction. After the accumulation of high-concentration ammonia in methanol, the yield of the alcoholysis intermediate N-phenyl coumaric methyl ester is reduced. At the same time, methanol and aniline can slowly generate a small amount of water and N-methylaniline under the alcoholysis reaction condition, and the accumulation of water in methanol also reduces the yield of the alcoholysis intermediate N-phenyl coumaric methyl ester. Since the existing flash separation methanol technology can ensure that the content of methanol in the product liquid is qualified, but does not purify after the separation of methanol, the dissolved ammonia, water and aniline in methanol are accumulated, thereby causing the yield of N-phenyl coumaric methyl ester to be too low. At the same time, the accumulation of a large amount of ammonia in methanol can cause the reactor pressure to rise and even overpressure, thereby affecting the safe and stable operation of the device.

[0004] In summary, in the alcoholysis production process, for the treatment of a large amount of methanol liquid containing ammonia and water, appropriate equipment and operation should be selected according to the characteristics of the material, so that the methanol can be effectively separated and purified, thereby avoiding product loss and reactor damage as much as possible. SUMMARY

[0005] The present application aims to provide a circulating methanol separation device in an alcoholysis intermediate production process, which solves the problems of low yield of heat-sensitive products and easy overpressure of a reactor caused by low methanol purity in the existing alcoholysis production process.

[0006] The present application also aims to provide a circulating methanol separation method in an alcoholysis intermediate production process.

[0007] The first technical solution of the present application is: a circulating methanol separation device in an alcoholysis intermediate production process, comprising a methanol refining unit, an aniline recovery unit and a vacuum unit;

[0008] The methanol refining unit comprises a crude methanol tank, the crude methanol tank is connected to a middle part feed inlet of a methanol refining column, a gas phase outlet at the top of the methanol refining column is connected to a methanol refining column top condenser, a liquid phase outlet of the methanol refining column top condenser is connected to a methanol refining column top condensate tank, the liquid phase outlet of the methanol refining column top condensate tank is connected to a reflux inlet at the top of the methanol refining column, a gas phase outlet of the methanol refining column top condenser is connected to an ammonia recovery system, a middle part outlet of the methanol refining column is connected to a refined methanol buffer tank, the refined methanol buffer tank is sequentially connected to a refined methanol cooler and a refined methanol tank, a liquid phase outlet of the refined methanol tank is connected to an alcoholysis reaction kettle, the liquid phase outlet of the methanol refining column is divided into two paths, one path is connected to a methanol refining column kettle reboiler through a pump to form a liquid phase circulation loop, and the other path is sent to the aniline recovery unit.

[0009] The aniline recovery unit comprises an aniline recovery column, a middle part feed inlet of the aniline recovery column is connected to the methanol refining column, a gas phase outlet at the top of the aniline recovery column is connected to an aniline recovery column top condenser, a liquid phase outlet of the aniline recovery column top condenser is connected to an aniline recovery column top condensate tank, a gas phase outlet of the aniline recovery column top condenser is connected to a vacuum unit, a liquid phase outlet of the aniline recovery column top condensate tank is connected to a reflux inlet at the top of the aniline recovery column, the liquid phase outlet of the aniline recovery column is divided into two paths, one path is connected to an aniline recovery column kettle reboiler through a pump to form a liquid phase circulation loop, and the other path is sent to an aniline tank area.

[0010] The present application is characterized in that,

[0011] The methanol refining column is provided with three packing layers, liquid collectors and liquid distributors are arranged between the packing layers, the liquid distributors are arranged close to a liquid inlet of the methanol refining column, a wire mesh demister is arranged at the gas phase outlet of the methanol refining column, and an anti-vortex baffle is arranged at the liquid phase outlet of the methanol refining column kettle.

[0012] The cooling medium of the methanol refining column top condenser, the refined methanol cooler and the aniline recovery column top condenser is circulating water or chilled water, and the temperature of the chilled water is-10-5 DEG C.

[0013] The heating medium of the methanol refining column kettle reboiler and the aniline recovery column kettle reboiler is steam or heat conducting oil.

[0014] The vacuum unit is any one of a liquid ring type vacuum unit, a Roots blower, a rotary vane vacuum machine, a screw vacuum pump and an ejector pump.

[0015] The second solution of the present application is a circulating methanol separation method in an alcoholysis intermediate production process, and the specific operation steps are as follows:

[0016] Step 1: crude methanol in the crude methanol tank is pumped into the methanol refining tower by the mechanical pump, and pressure rectification is carried out, non-condensable ammonia gas is obtained at the top of the tower and is sent to the ammonia gas recovery system, refined methanol is obtained in the middle part of the tower and is cooled by the refined methanol cooler and then is sent into the refined methanol tank and is pumped into the methanol reaction kettle by the mechanical pump, and part of the liquid phase of the methanol refining tower is pumped into the methanol refining tower reboiler by the mechanical pump and is heated and then is returned to the tower, and the other part is sent to the middle part of the aniline recovery tower, and the liquid phase includes aniline and water;

[0017] Step 2: aniline and water obtained in step 1 are subjected to pressure rectification in the aniline recovery tower, and gaseous aniline is obtained at the top of the tower and is condensed by the aniline recovery tower top condenser and is stored in the aniline recovery tower top condensate tank, and at the same time, the obtained waste water is pumped out of the boundary area by the mechanical pump, and part of the liquid phase aniline obtained in the aniline recovery tower top condensate tank is pumped into the aniline recovery tower top reflux port by the mechanical pump, and the other part is discharged as waste water out of the boundary area, and part of the liquid phase in the aniline recovery tower kettle is pumped into the aniline recovery tower kettle reboiler by the mechanical pump and is heated and then is returned to the kettle, and the other part is sent to the aniline tank area.

[0018] The application also has the characteristics that

[0019] As a preferred technical scheme of the application, the source of the crude methanol in step 1 includes a carbonylation intermediate production process, preferably a process for producing N-phenyl coumaric methyl ester product by taking methanol and N, N-diphenylurea as raw materials, and the crude methanol is obtained by crude separation after reaction, and the crude methanol is subjected to pressure rectification in the methanol refining unit.

[0020] Preferably, the composition of the crude methanol in step 1 includes ammonia, methanol, water and aniline.

[0021] Preferably, the temperature of the crude methanol in step 1 is 30-60℃, for example, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0022] Preferably, the pressure of the crude methanol tank in step 1 is normal pressure.

[0023] Preferably, the top pressure of the methanol refining tower in step 1 is 0-0.3 MPa (A), for example, 0 MPa (A), 0.05 MPa (A), 0.1 MPa (A), 0.15 MPa (A), 0.2 MPa (A), 0.25 MPa (A), 0.3 MPa (A) or the like, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] Preferably, the temperature at the top of the methanol refining tower in step 1 is 50-90°C; for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the temperature of the methanol refining tower top reflux material in step 1 is 40~80°C; for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the extraction temperature in the middle of the methanol refining tower in step 1 is 70-100°C; for example, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the methanol outlet temperature of the refined methanol cooler in step 1 is not higher than 20°C; for example, 0°C, 5°C, 10°C, 15°C, 20°C, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0028] Preferably, the temperature of the methanol refining tower bottom in step 1 is 110-140°C; for example, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C or 140°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] Preferably, the ammonia content in the refined methanol in step 1 is not higher than 100 PPM, and the water content is not higher than 250 PPM.

[0030] Preferably, the pressure of the aniline recovery tower in step 2 is 15 to 40 KPa (A); for example, 15 KPa (A), 20 KPa (A), 25 KPa (A), 30 KPa (A), 35 KPa (A), 40 KPa (A), etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] Preferably, the temperature of the top of the aniline recovery tower in step 2 is 50-75°C; for example, 50°C, 55°C, 60°C, 67°C, 70°C, 75°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the aniline recovery tower top reflux temperature in step 2 is 30-50°C; for example, 30°C, 35°C, 40°C, 45°C, 50°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the aniline recovery column temperature in step 2 is 125-150℃; for example 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0034] Preferably, the water content in the recovered aniline in step 2 is close to 0.

[0035] Preferably, the methanol refining column overhead condenser in step 1 has a heat tracing line, which can use steam heat tracing and electric heat tracing; the heat tracing temperature is 80-130℃.

[0036] Preferably, the heating medium for the methanol refining column reboiler and the aniline recovery column reboiler is 0.5MPa steam, with a steam temperature of about 150℃.

[0037] Preferably, the refined methanol tank is provided with a spray system, and the spray medium is circulating water, which is cooled to 10℃ by chilled water heat exchange to ensure that the refined methanol tank temperature is 20℃.

[0038] Preferably, the methanol outlet temperature of the refined methanol cooler is not higher than 20℃.

[0039] In the present application, for the production process of alcoholysis intermediates, especially the intermediates for producing isocyanate, such as N-phenyl coumarin methyl ester, the present application realizes effective purification of the circulating methanol to meet the process requirements, improves the yield of heat-sensitive products, and solves the problem of easy overpressure of the reactor, and the device has simple structure, meets long-term continuous and stable operation, is low in cost and good in effect. The device separates the methanol containing ammonia, water and a small amount of aniline through deamination, dehydration and aniline recovery, realizes methanol purification, and effectively solves the problems of product yield reduction and reactor pressure fluctuation.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] (1) The device of the present application is provided with two-stage distillation devices, which first purifies the methanol in the crude methanol through primary pressurized distillation, and then separates water and a small amount of aniline through primary decompression distillation. The separated refined methanol and aniline have high purity and can be returned to the synthesis reaction system. The device realizes efficient purification of the circulating methanol for synthesizing heat-sensitive intermediates, the methanol purity reaches more than 99.5%, and the recovery rate reaches more than 99%.

[0042] (2) The device can effectively solve the problem of the yield reduction of the heat-sensitive intermediate caused by the accumulation of ammonia and water in the circulating methanol during the reaction process, and the overpressure problem of the reaction kettle caused thereby, and the continuous and stable operation can reach more than 3000h, and the production efficiency is high.

[0043] (3) By the operation of the middle extraction and the middle reflux in the methanol refining tower, the operation of ammonia removal and water removal is realized by one device. Compared with the scheme of setting two towers in the ordinary rectification, the operation difficulty is increased, but the equipment cost is low, and it is more economical. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 It is a structure schematic diagram of the circulating methanol separation device in the alcoholysis intermediate production process of the application.

[0045] Figure 2 It is a structure schematic diagram of the methanol refining tower of the application.

[0046] In the figure: 1-coarse methanol tank, 2-methanol refining tower, 3-methanol refining tower top condenser, 4-methanol refining tower top condensate tank, 5-fine methanol buffer tank, 6-fine methanol cooler, 7-fine methanol tank, 8-methanol refining tower kettle reboiler, 9-aniline recovery tower, 10-aniline recovery tower top condenser, 11-aniline recovery tower top condensate tank, 12-aniline recovery tower kettle reboiler, 13-vacuum unit;

[0047] 21-liquid distributor, 22-packed layer, 23-liquid collector; 24-wire mesh demister; 25-anti-vortex baffle. DETAILED DESCRIPTION

[0048] The application will be further described in detail below in combination with the drawings and examples.

[0049] Example 1

[0050] The application provides a circulating methanol separation device in the alcoholysis intermediate production process, like Figure 1As shown, including methanol refining unit and aniline recovery unit and vacuum unit; methanol refining unit includes crude methanol tank 1, crude methanol tank 1 is connected to the middle part of methanol refining column 2 feed inlet; methanol refining column 2 top gas phase outlet is connected to methanol refining column top condenser 3, methanol refining column top condenser 3 liquid phase outlet is connected to methanol refining column top condensate tank 4; methanol refining column top condensate tank 4 liquid phase outlet is connected with methanol refining column 2 top reflux port, methanol refining column top condenser 3 gas phase outlet is connected with ammonia recovery system; methanol refining column 2 middle part is connected to refined methanol buffer tank 5, refined methanol buffer tank 5 is connected with refined methanol cooler 6, refined methanol tank 7 in turn; refined methanol tank 7 liquid phase outlet is connected to alcoholysis reactor; methanol refining column 2 liquid phase outlet is divided into two ways, one way is connected with methanol refining column reboiler 8 through pump to form liquid phase circulation loop, the other way is sent to aniline recovery unit;

[0051] Aniline recovery unit includes aniline recovery column 9, the middle part of aniline recovery column 9 is connected with methanol refining column 2; aniline recovery column 9 top gas phase outlet is connected to aniline recovery column top condenser 10, aniline recovery column top condenser 10 liquid phase outlet is connected to aniline recovery column top condensate tank 11, aniline recovery column top condenser 10 gas phase outlet is connected to vacuum unit, aniline recovery column top condensate tank 11 liquid phase outlet is connected with aniline recovery column 9 top reflux port, aniline recovery column 9 liquid phase outlet is divided into two ways, one way is connected with aniline recovery column reboiler 12 through pump to form liquid phase circulation loop, the other way is sent to aniline tank area.

[0052] As shown in the figure, Figure 2 Methanol refining column 2 is provided with three packing layers 22; liquid collector 23 and liquid distributor 21 are arranged between packing layers 22, and liquid distributor 21 is arranged close to the liquid inlet of methanol refining column 2; there is a wire mesh demister 24 at the gas phase outlet of methanol refining column; there is an anti-vortex baffle 25 at the liquid phase outlet of methanol refining column.

[0053] Methanol refining column top is full reflux, and the non-condensed gas pipeline of methanol refining column top condenser is heated (the composition of non-condensed gas is ammonia and a small amount of water and carbon dioxide, which will form ammonium carbonate to block the pipeline at low temperature, so heating is needed), 0.3 MPa (A) steam heating mode is adopted, and the heating steam temperature is about 130 DEG C;

[0054] The cooling medium of methanol refining column top condenser 3 and aniline recovery column top condenser 10 is circulating water, and the cooling medium of refined methanol cooler 6 is refrigerated water with a temperature of 0 DEG C.

[0055] A spraying system is arranged in refined methanol tank 7, and the spraying medium is circulating water, which is cooled to 10 DEG C through refrigerated water heat exchange, so that the temperature in refined methanol tank is 20 DEG C.

[0056] The vacuum unit is a liquid ring type vacuum unit, and the working liquid used is aniline.

[0057] Example 2

[0058] Based on Example 1, the difference from Example 1 is that,

[0059] The methanol refining tower top is full reflux, the methanol refining tower top condenser does not condense gas pipeline has heat tracing, adopts electric heat tracing mode, sets the heat tracing temperature to 100℃;

[0060] The cooling medium of the methanol refining tower top condenser 3, the refined methanol cooler 6 and the aniline recovery tower top condenser 10 is chilled water, and the chilled water temperature is 5℃.

[0061] The heating medium of the methanol refining tower kettle reboiler 8 and the aniline recovery tower kettle reboiler 12 is steam or conductive oil.

[0062] The refined methanol tank 7 is provided with cooling coils, the medium in the coils is chilled water, and the refined methanol tank temperature is 15℃.

[0063] The vacuum unit is a rotary vane vacuum machine.

[0064] Example 3

[0065] The circulating methanol separation method in the production process of the alcoholysis intermediate is carried out by using the device in Example 1, and the specific operation steps are as follows:

[0066] (1) The crude methanol obtained by alcoholysis intermediate production is composed of 90wt% methanol, 5wt% ammonia, 1wt% water and 4wt% aniline, and the temperature of the material is 30℃.

[0067] (2) The crude methanol is transported into the methanol refining tower by a mechanical pump, the methanol refining tower pressure is normal pressure, the tower top temperature is 55℃, the tower top reflux temperature is 45℃, the non-condensed ammonia gas at the top of the methanol refining tower is sent to an ammonia gas recovery device; the middle part of the tower is extracted at a temperature of 70℃, half of the methanol extracted from the middle part is returned, and the other half is cooled to 20℃ by a refined methanol cooler and then enters a refined methanol tank, and the refined methanol is sent to a reaction kettle by a mechanical pump; the kettle temperature is 115℃, most of the liquid phase in the kettle is heated by a reboiler and returned to the kettle, and a small part enters an aniline recovery tower.

[0068] (3) The aniline recovery tower pressure is 20KPa (A), the tower top temperature is 60℃, the reflux temperature is 40℃, the reflux ratio is set to 0.5, and the kettle temperature is 130℃; the wastewater obtained at the top of the tower is sent to a boundary area, and the aniline obtained at the kettle is returned to a tank area.

[0069] (4) The ammonia gas is pressurized, cooled and purified in the recovery device, and finally recovered in the form of liquid ammonia.

[0070] (5) In this embodiment, the device and method are used for methanol purification. According to the content of methanol in step 1, the methanol separation rate reaches 99.95%, the pure methanol purity is 99.9%, the ammonia content is 80 PPM, and the water content is 150 PPM.

[0071] (6) In this embodiment, the device and method are used for aniline recovery. According to the content of aniline in step 2, the aniline separation rate reaches 99.0%, the aniline purity is 99.5%, and the water content is extremely low.

[0072] (7) The device in this embodiment has a continuous stable operation time of 3000h.

[0073] Example 4

[0074] The circulating methanol separation method in the production process of alcoholysis intermediates is carried out by using the device in Example 2, and the specific operation steps are as follows:

[0075] (1) The crude methanol obtained by alcoholysis intermediate production is composed of 85wt% methanol, 8wt% ammonia, 2wt% water, and 5wt% aniline, and the temperature of the material is 40℃.

[0076] (2) The crude methanol is transported into the methanol refining tower by the mechanical pump, the methanol refining tower pressure is 0.2 MPa (A), the tower top temperature is 75℃, the tower top reflux temperature is 60℃, the non-condensable ammonia gas at the top of the methanol refining tower is sent to the ammonia gas recovery device; the middle part of the tower is extracted at a temperature of 85℃, one third of the methanol extracted from the middle part of the tower is returned, one third is cooled to 15℃ by the refined methanol cooler and then enters the refined methanol tank, and the refined methanol is sent to the reaction kettle by the mechanical pump; the tower kettle temperature is 125℃, most of the liquid phase in the tower kettle is heated by the reboiler and returned to the tower kettle, and a small part enters the aniline recovery tower.

[0077] (3) The aniline recovery tower pressure is 30KPa (A), the tower top temperature is 70℃, the reflux temperature is 55℃, the reflux ratio is set to 0.8, and the tower kettle temperature is 148℃; the wastewater obtained at the top of the tower is sent to the boundary area, and the aniline obtained at the tower kettle is returned to the tank area.

[0078] (4) The ammonia gas is pressurized, cooled and purified in the recovery device, and finally recovered in the form of liquid ammonia.

[0079] (5) In this embodiment, the device and method are used for methanol purification. According to the content of methanol in step 1, the methanol separation rate reaches 99.9%, the pure methanol purity is 99.95%, the ammonia content is 50 PPM, and the water content is 200 PPM.

[0080] (6) In this embodiment, the device and method are used for aniline recovery. According to the content of aniline in step 2, the aniline separation rate reaches 99.5%, the aniline purity is 99.0%, and the water content is extremely low.

[0081] (7) The device described in this embodiment has a continuous stable operation time of 3300 hours.

[0082] The present application is described in detail by the above embodiments, but the present application is not limited to the above detailed devices and methods, that is, it does not mean that the present application must be implemented in the above detailed devices and methods. Those skilled in the art should understand that any improvement of the present application, equivalent replacement of the devices of the present application, addition of auxiliary devices, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A process for the separation of recycled methanol in the production of alcoholysis intermediates, characterized in that, The application discloses a methanol separation device for recycling methanol in the production process of alcoholysis intermediates; the methanol separation device comprises a methanol refining unit, an aniline recovery unit and a vacuum unit; The methanol refining unit comprises a crude methanol tank (1) connected to a middle feeding port of a methanol refining tower (2); a gas phase outlet at the top of the methanol refining tower (2) is connected to a methanol refining tower top condenser (3), a liquid phase outlet of the methanol refining tower top condenser (3) is connected to a methanol refining tower top condensate tank (4); a liquid phase outlet of the methanol refining tower top condensate tank (4) is connected to a top reflux port of the methanol refining tower (2), a gas phase outlet of the methanol refining tower top condenser (3) is connected to an ammonia recovery system; a middle part of the methanol refining tower (2) is connected to a refined methanol buffer tank (5), the refined methanol buffer tank (5) is sequentially connected to a refined methanol cooler (6) and a refined methanol tank (7); a liquid phase outlet of the refined methanol tank (7) is connected to an alcoholysis reaction kettle; a liquid phase outlet of the methanol refining tower (2) is divided into two paths, one path is connected to a methanol refining tower kettle reboiler (8) through a pump to form a liquid phase circulation loop, and the other path is sent to the aniline recovery unit; The aniline recovery unit comprises an aniline recovery tower (9), a middle feeding port of the aniline recovery tower (9) is connected to the methanol refining tower (2); a gas phase outlet at the top of the aniline recovery tower (9) is connected to an aniline recovery tower top condenser (10), a liquid phase outlet of the aniline recovery tower top condenser (10) is connected to an aniline recovery tower top condensate tank (11), a gas phase outlet of the aniline recovery tower top condenser (10) is connected to a vacuum unit, a liquid phase outlet of the aniline recovery tower top condensate tank (11) is connected to a top reflux port of the aniline recovery tower (9), a liquid phase outlet of the aniline recovery tower (9) is divided into two paths, one path is connected to an aniline recovery tower kettle reboiler (12) through a pump to form a liquid phase circulation loop, and the other path is sent to an aniline tank area; The specific operation steps are as follows: Step 1: crude methanol in the crude methanol tank is sent into the methanol refining tower through a pump, pressure rectification is carried out, non-condensed ammonia gas is obtained at the top of the tower, the non-condensed ammonia gas is sent to an ammonia recovery system, refined methanol obtained from the middle part of the tower is cooled by a refined methanol cooler and then sent into a refined methanol tank, and then the refined methanol is sent to a methanol reaction kettle through a pump; a part of the liquid phase of the methanol refining tower is sent to a methanol refining tower kettle reboiler through a pump to be heated and then returned to the tower, and the other part is sent to a middle feeding port of an aniline recovery tower, wherein the liquid phase comprises aniline and water; Step 2: aniline and water obtained in step 1 are subjected to pressure rectification in the aniline recovery tower, gas phase aniline obtained at the top of the tower is condensed by an aniline recovery tower top condenser and then stored in an aniline recovery tower top condensate tank; meanwhile, the obtained waste water is sent to an area outside the system through a pump; a part of the liquid phase aniline obtained from the aniline recovery tower top condensate tank is sent to a top reflux port of the aniline recovery tower through a pump, the other part is discharged as waste water, a part of the liquid phase of the aniline recovery tower kettle is sent to an aniline recovery tower kettle reboiler through a pump to be heated and then returned to the kettle, and the other part is sent to an aniline tank area.

2. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The methanol refining tower (2) is internally provided with three packing layers (22); the packing layers (22) are all provided with liquid collectors (23) and liquid distributors (21), the liquid distributor (21) is arranged close to the liquid phase inlet of the methanol refining tower (2); the gas phase outlet of the methanol refining tower is provided with a wire mesh demister (24); the liquid phase outlet of the methanol refining tower kettle is provided with an anti-vortex baffle (25).

3. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The cooling medium of the methanol refining tower overhead condenser (3), the refined methanol cooler (6) and the aniline recovery tower overhead condenser (10) is circulating water or refrigerated water, and the temperature of the refrigerated water is -10~5℃.

4. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The heating medium of the methanol refining tower kettle reboiler (8) and the aniline recovery tower kettle reboiler (12) is steam or conductive oil.

5. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The vacuum unit is any one of a liquid ring type vacuum unit, a Roots blower, a rotary vane vacuum machine, a screw vacuum pump and a jet pump.

6. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The non-condensable gas pipeline of the methanol refining tower overhead condenser (3) in step 1 is provided with heat tracing, and steam heat tracing or electric heat tracing is adopted, and the temperature of the steam heat tracing is 130℃.

7. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The heating medium of the methanol refining tower kettle reboiler (8) and the aniline recovery tower kettle reboiler (12) is 0.5MPa steam, and the steam temperature is 150℃.

8. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The refined methanol tank is provided with a spraying system, and the spraying medium is circulating water, which is cooled to 10℃ by refrigerated water heat exchange to ensure that the temperature of the refined methanol tank is 20℃. The composition of the crude methanol in step 1 includes ammonia, methanol, water and aniline, and the temperature of the crude methanol is 30~60℃; the pressure of the crude methanol tank (1) is normal pressure. The pressure at the top of the methanol refining tower is 0~0.3 MPa (A), the temperature at the top of the methanol refining tower is 50~90℃, and the temperature of the methanol refining tower kettle is 110~140℃. The temperature of the methanol outlet of the refined methanol cooler (6) is not higher than 20℃.

9. The process for separating methanol recycled in the process for producing alcoholysis intermediates according to claim 1, characterized in that, The pressure of the aniline recovery tower in step 2 is 15~40 kPa (A); the temperature at the top of the aniline recovery tower is 50~75℃, the reflux temperature at the top of the aniline recovery tower is 30~50℃, and the temperature of the aniline recovery tower kettle is 125~150℃.

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