Preparation method and equipment of 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane

Abstract

The invention relates to a preparation method of 3, 4-difluorobenzene. The invention relates to a preparation method and equipment of 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane, o-ethylaniline, hydrochloric acid and water pass through a first static mixer to form hydrochloride of o-ethylaniline, the hydrochloride of o-ethylaniline and a formaldehyde solution are condensed in a second static mixer, and then high-temperature rearrangement, alkali neutralization, water washing, dehydration, free amine removal and filtration are performed to obtain the 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane. The purity of the 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane prepared by the process is about 95%, the polymer content is 4%-5%, the free amine content is lower than 0.2%, the appearance of the 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane is transparent yellow, and the viscosity of the 3, 3 '-diethyl-4, 4'-diaminodiphenylmethane is 1400-2000cps.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals, and relates to a method and equipment for preparing a high-performance polyurethane and epoxy resin curing agent, and in particular to a method and equipment for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane. Background Art

[0002] 3,3'-Diethyl-4,4'-diaminodiphenylmethane is an important liquid aromatic diamine. It can be used as a chain extender for polyurea spray elastomers, used in anti-corrosion projects for marine ships, drilling platforms and large steel structures, coating materials for aerospace equipment, and the production of energy-containing hidden parts for national defense. It can also be used as a curing agent for epoxy resins, giving the products good tensile strength, tear strength, electrical insulation properties and heat resistance.

[0003] The synthesis principle of 3,3'-diethyl-4,4'-diaminodiphenylmethane is as follows: ; Regarding the synthesis of 3,3'-diethyl-4,4'-diaminodiphenylmethane; CN1288128C introduces a method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane: sulfuric acid is dripped into a mixed solution of o-ethylaniline, an alcohol solvent and water at a reflux temperature of 40°C to 80°C and stirred at a constant temperature for 1 to 3 hours. After the mixture is salted, formaldehyde solution is dripped into the mixed solution at a reflux temperature of 40°C to 80°C for condensation reaction, and the mixture is kept warm for 1 to 2 hours. Then, alkali is added for neutralization, the solvent is removed at a constant pressure, water is washed, and the mixture is distilled under reduced pressure for dehydration. The mixture is distilled at a critical temperature of 160°C to 200°C for 4 to 8 hours to remove the free amine and obtain a brown product with a viscosity of 2000 to 5000 cps (25°C). This process uses ethanol as a solvent during the synthesis process and promotes the reaction. The rearrangement reaction temperature after the condensation of the sulfate of o-ethylaniline and formaldehyde is limited by the boiling point of ethanol, which is a maximum of 80°C, which is not conducive to the rearrangement reaction and limits the improvement of product purity. In addition, the alcohol solvent needs to be recovered later, and there are many operation steps. The reaction of o-ethylaniline is slow, the removal time of free amine is long, and the high-temperature vacuum distillation time of free amine is long. The final product is dark in color, which is not conducive to the application of 3,3'-diethyl-4,4'-diaminodiphenylmethane in light-colored products.

[0004] Xu Zhen pointed out in the journal "Research on the Synthesis of 3,3'-Diethyl-4,4'-Diaminodiphenylmethane": The presence of polar solvents can promote rapid reaction. The stronger the polarity of the solvent, the more polymers produced by side reactions, the worse the product quality and the lower the yield. When hydrochloric acid is used as a catalyst, since o-ethylaniline hydrochloride is in liquid form in the system and forms a phase of its own, obvious stratification occurs, which ultimately leads to a significantly low raw material conversion rate and more side reactions. According to this method, under laboratory conditions, the yield is only 60.6% and the purity is only 88.8%, which also contains 8.9% polymers. See Table 3 of "Research on the Synthesis of 3,3'-Diethyl-4,4'-Diaminodiphenylmethane".

[0005] The prior art urgently needs a method and special equipment for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane with high purity and light color. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to overcome the above-mentioned gaps in the prior art and provide a method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane and an apparatus thereof.

[0007] In order to solve the above technical problems, the technical solution of the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention is: (1) o-ethylaniline, hydrochloric acid and water are passed through a first static mixer to form o-ethylaniline hydrochloride; (2) Then condense with formaldehyde solution in a second static mixer; (3) After high temperature rearrangement, alkali neutralization, water washing, dehydration and removal of free amine, and filtration, 3,3'-diethyl-4,4'-diaminodiphenylmethane is obtained.

[0008] The preferred technical solution is: the mass concentration of hydrochloric acid is 25-36%; the molar ratio of o-ethylaniline to hydrochloric acid is 1:1-1:2.

[0009] The preferred technical solution is: the formaldehyde solution is a formaldehyde solution with a mass concentration of 20-37%; the molar ratio of o-ethylaniline hydrochloride to formaldehyde is 1.9:1-3:1, and the condensation temperature is 30°C-60°C.

[0010] The preferred technical solution is: the temperature of the reactor during rearrangement is 80°C to 110°C, and the rearrangement time is 2 to 6 hours.

[0011] The preferred technical solution is: the temperature of the reactor during rearrangement is 90°C to 110°C, and the rearrangement time is preferably 2 to 4 hours.

[0012] The preferred technical solution is: in step (1), the first static mixer is also equipped with a preheating mixing tank, a first buffer tank, a first circulation pump and a first circulation valve, wherein the preheating mixing tank is provided with an electric stirrer, a thermometer and a circulation jacket, the circulation jacket is provided with a heating water or heating oil circulation system, a feeding hopper is provided at the top of the preheating mixing tank, a feeding pipe with a feeding valve is connected to the bottom of the feeding hopper, and the feeding pipe is communicated with the preheating mixing tank, and the three feeding hoppers are used to add o-ethylaniline, hydrochloric acid and water respectively, the first static mixer is connected to the first buffer tank, the first circulation pump and the first circulation valve through pipelines to form a first circulation reaction device, a discharge pipe with a discharge valve is provided at the bottom of the preheating mixing tank, and the discharge pipe is communicated with the first circulation reaction device, the outlet of the first circulation pump is also connected to an amine salt discharge pipe, and the amine salt discharge pipe is provided with an amine salt discharge valve, and the first buffer tank is provided with an electric stirrer.

[0013] In step (1), open the feeding valve on the feeding pipe of the preheating mixing tank, take corresponding amounts of o-ethylaniline, hydrochloric acid and water, add them into the preheating mixing tank through the feeding hopper and its feeding pipe, mix them in the preheating mixing tank, and heat them to a temperature in the range of 20-52° C., then open the discharge valve at the bottom of the preheating mixing tank, and enter the first circulation reaction device through the discharge pipe at the bottom of the preheating mixing tank, and most of them enter the first buffer tank, then start the electric stirring of the first buffer tank, close the discharge valve and amine salt discharge valve at the bottom of the preheating mixing tank, start the first circulation pump, open the first circulation valve and other valves on the pipeline of the first circulation reaction device, and o-ethylaniline, hydrochloric acid and water circulate in the first circulation reaction device. When o-ethylaniline and hydrochloric acid pass through the first static mixer, they mix and react to form o-ethylaniline hydrochloride. After 40 to 60 minutes of such circulation, the reaction is completed and step (2) can be entered.

[0014] In step (2), the second static mixer is also equipped with a second buffer tank, a second circulation pump and a second circulation valve. The second static mixer, the second buffer tank, the second circulation pump and the second circulation valve are connected to form a second circulation reaction device through a pipeline. The pipeline of the second circulation reaction device is also provided with a vertical formaldehyde feeding pipe, the formaldehyde feeding pipe is provided with a formaldehyde feeding valve, and the top of the formaldehyde feeding pipe is also connected to a formaldehyde feeding hopper. The amine salt discharge pipe is communicated with the pipeline of the second circulation reaction device. The pipeline of the second circulation reaction device is also provided with a condensation product discharge pipe, the condensation product discharge pipe is provided with a condensation product discharge valve, and the second buffer tank is provided with an electric stirrer.

[0015] Before the reaction of step (1) is completed, the formaldehyde feeding valve is opened in advance, and a proper amount of formaldehyde is added to the second circulation reaction device through the formaldehyde feeding hopper and the formaldehyde feeding pipe, and then the formaldehyde feeding valve is closed. After the reaction of step (1) is completed, the amine salt discharge valve is opened, the first circulation valve is closed, and all the materials in the first circulation reaction device are pumped into the second circulation reaction device, and then the electric stirring of the second buffer tank is turned on, and the amine salt discharge valve and the first circulation pump are closed.

[0016] Then, the second circulation pump is turned on, and the second circulation valve and other valves on the pipeline of the second circulation reaction device are opened. The o-ethylaniline hydrochloride and formaldehyde generated in step (1) are circulated in the second circulation reaction device. The o-ethylaniline hydrochloride and formaldehyde are fully mixed when passing through the second static mixer to generate a condensation product. After 40 to 60 minutes of circulation, the reaction is completed and the process can proceed to step (3).

[0017] o-Ethylaniline is insoluble in water and hydrochloric acid solution. o-Ethylaniline hydrochloride is liquid and forms a phase of its own, with obvious stratification. The existing technology is to add organic solvents, mainly alcohols. For example, "Study on the Synthesis of 3,3'-Diethyl-4,4'-Diaminodiphenylmethane" clearly points out that ethanol is the best reaction solvent. However, adding organic solvents dilutes the raw material concentration on the one hand, and on the other hand, it is necessary to design a method to remove these organic solvents at the end, which is cumbersome, has low yield, and takes a long time to form salts.

[0018] The present invention creatively connects a first static mixer with a first buffer tank, a first circulation pump and a first circulation valve through a pipeline to form a first circulation reaction device for the salt-forming reaction of o-ethylaniline hydrochloride; and a second static mixer with a second buffer tank, a second circulation pump and a second circulation valve through a pipeline to form a second circulation reaction device for the condensation reaction of o-ethylaniline hydrochloride and formaldehyde.

[0019] With this design, the raw material concentration is not diluted, which greatly shortens the salt-forming reaction time and the condensation reaction time. At the same time, the subsequent organic solvent removal process is omitted, the synthesis process is simplified, the rearrangement temperature is increased, and the target product content is increased.

[0020] The preferred technical solution is: the equipment required for step (3) includes a rearrangement reactor, a neutralization separation tank, a first water washing tank, a second water washing tank, a vacuum distillation kettle, a filter, a condenser, a vacuum pump, a wastewater tank, a dehydration tank, a free amine removal tank and a finished product tank.

[0021] The rearrangement reactor, the neutralization separation tank, the first water washing tank and the second water washing tank are connected in sequence through a discharge pipe with a discharge valve, and all discharge from the bottom and feed from the top or upper part. The condensation product discharge pipe leads into the rearrangement reactor. The discharge pipes at the bottom of the neutralization separation tank, the first water washing tank and the second water washing tank are also provided with a pipeline sight glass, and are connected with a wastewater discharge pipe with a wastewater valve. The wastewater discharge pipes all lead to the wastewater tank. A sodium hydroxide solution feeding pipe is provided on the top of the neutralization separation tank. Water injection pipes are respectively provided on the first water washing tank and the second water washing tank. The water injection pipes are provided with a water injection valve. The discharge pipe at the bottom of the second water washing tank leads to the vacuum distillation kettle. A nitrogen pressurizing pipe with a pressurizing valve is provided on the vacuum distillation kettle. The nitrogen pressurizing pipe is communicated with a high-pressure nitrogen source. The rearrangement reactor and the vacuum distillation kettle are both provided with a thermometer and a circulation jacket. The circulation jacket is equipped with a steam heating system or a heating oil circulation system. The system comprises a liquid discharge pipe and an evaporation gas discharge pipe, wherein one end of the liquid discharge pipe extends into the bottom of the vacuum distillation kettle, and the other end is connected to the finished product tank. The filter is connected in series to the liquid discharge pipe, and a finished product discharge valve is provided on the liquid discharge pipe between the filter and the vacuum distillation kettle. The evaporation gas discharge pipe is provided with a valve and is connected to the condenser. The bottom of the condenser is provided with a discharge pipe with a pipeline sight glass, and the discharge pipe is connected to two discharge branches, and valves are provided on the two discharge branches, and are respectively connected to the dehydration tank and the free amine removal tank. The dehydration tank and the free amine removal tank are respectively provided with vacuum branches, and valves are provided on the vacuum branches, and are commonly connected to the suction port of the vacuum pump. The rearrangement reactor, the neutralization separation tank, the first water washing tank, the second water washing tank, and the vacuum distillation kettle are all provided with electric stirring, and the condenser is equipped with a circulating water condensation system. Rearrangement reaction: After step (2), the condensation product discharge valve is opened to allow the condensation product in the second circulation reaction device to enter the rearrangement reaction kettle, and then the electric stirring and steam heating system or heating oil circulation system of the rearrangement reaction kettle is turned on to increase the temperature in the rearrangement reaction kettle and maintain it in the range of 90°C to 110°C. After 2 to 4 hours of reaction, the rearrangement reaction is completed. Neutralization: open the discharge valve on the discharge pipe at the bottom of the rearrangement reactor, put the material in the rearrangement reactor into or pump it into the neutralization separation tank, then turn on the electric stirring of the neutralization separation tank, and meet the sodium hydroxide solution added through the sodium hydroxide solution feeding pipe in the neutralization separation tank. After fully mixing and neutralizing, turn off the electric stirring of the neutralization separation tank, let the liquid in the neutralization separation tank stand and stratify, then open the wastewater valve at the bottom of the neutralization separation tank, and discharge the brine in the lower layer of the neutralization separation tank into the wastewater tank through the wastewater discharge pipe. After finding that the brine has been discharged through the pipeline sight glass at the bottom of the neutralization separation tank, close the wastewater valve at the bottom of the neutralization separation tank, then open the discharge valve on the discharge pipe at the bottom of the neutralization separation tank, put the crude MOEA in the neutralization separation tank into the first water washing tank, and then close the discharge valve on the discharge pipe at the bottom of the neutralization separation tank.

[0022] First water washing: open the water injection valve on the first water washing tank, inject an appropriate amount of hot water at 80℃~100℃ into the first water washing tank through the water injection pipe, turn on the electric stirring of the first water washing tank for 20-40 minutes, then turn off the electric stirring of the first water washing tank, let the liquid in the first water washing tank stand and stratify, then open the discharge valve on the discharge pipe at the bottom of the first water washing tank, put the crude MOEA in the lower layer of the first water washing tank into the second water washing tank, and after finding that the crude MOEA has been discharged through the pipeline sight glass at the bottom of the first water washing tank, close the discharge valve on the discharge pipe at the bottom of the first water washing tank, open the wastewater valve at the bottom of the first water washing tank, and discharge all the remaining wastewater in the first water washing tank into the wastewater tank through the wastewater discharge pipe, completing the first water washing; Second water washing: open the water injection valve on the second water washing tank, inject an appropriate amount of hot water at 80℃~100℃ into the second water washing tank through the water injection pipe, turn on the electric stirring of the second water washing tank for 20-40 minutes, then turn off the electric stirring of the second water washing tank, let the liquid in the second water washing tank stand and stratify, then open the discharge valve on the discharge pipe at the bottom of the second water washing tank, put the crude MOEA in the lower layer of the second water washing tank into the vacuum distillation kettle, and after finding that the crude MOEA has been discharged through the pipeline sight glass at the bottom of the second water washing tank, close the discharge valve on the discharge pipe at the bottom of the second water washing tank, open the wastewater valve at the bottom of the second water washing tank, and discharge all the remaining wastewater in the second water washing tank into the wastewater tank through the wastewater discharge pipe, completing the second water washing; Dehydration: Open the circulating water system and vacuum pump of the condenser, then open the valve on the evaporation gas discharge pipe, the valve on the discharge branch pipe connected to the dehydration tank at the bottom of the condenser, and the valve on the vacuum branch pipe connected to the dehydration tank, and open the electric stirring and steam heating system or heating oil circulation system of the vacuum distillation kettle, raise the temperature in the vacuum distillation kettle, and keep it in the range of 102℃~105℃. After the water in the rearrangement reactor evaporates, it enters the condenser, and after condensing into water in the condenser, it enters the dehydration tank through the bottom discharge pipe of the condenser. The gas that cannot be condensed is discharged through the vacuum pump. Observe the pipeline sight glass at the bottom of the condenser. When no liquid flows down the condenser, the dehydration is over; Removal of free amine: open the valve on the discharge branch pipe connected to the free amine tank at the bottom of the condenser and the valve on the vacuum branch pipe connected to the free amine tank, close the valve on the discharge branch pipe connected to the dehydration tank at the bottom of the condenser and the valve on the vacuum branch pipe connected to the dehydration tank, adjust the steam heating system or heating oil circulation system of the vacuum distillation kettle, increase the temperature in the vacuum distillation kettle, and keep it in the range of 180℃~200℃, after the free amine in the rearrangement reactor evaporates, it enters the condenser, and after condensing into liquid in the condenser, it enters the free amine tank through the bottom discharge pipe of the condenser, and the gas that cannot be condensed is discharged through the vacuum pump, observe the pipeline sight glass at the bottom of the condenser, when there is no more liquid flowing down the condenser, the free amine is finished, close the steam heating system or heating oil circulation system and vacuum pump of the vacuum distillation kettle, and close the valve on the discharge pipe of the evaporated gas; Finished product discharge: Open the pressure valve on the nitrogen pressure pipe, introduce high-pressure nitrogen into the vacuum distillation kettle, open the finished product discharge valve, and press the liquid in the vacuum distillation kettle into the filter through the liquid discharge pipe. The liquid filtered by the filter is the finished product MOEA, and the finished product MOEA is injected into the finished product tank through the liquid discharge pipe.

[0023] The special equipment for the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention comprises a rearrangement reactor, which is characterized by comprising a first static mixer and a second static mixer, wherein the first static mixer is equipped with a preheating mixing tank, a first buffer tank, a first circulation pump and a first circulation valve, wherein the preheating mixing tank is provided with an electric stirrer, a thermometer and a circulation jacket, the circulation jacket is provided with a heating water or heating oil circulation system, a feeding hopper is provided at the top of the preheating mixing tank, a feeding pipe with a feeding valve is connected to the bottom of the feeding hopper, and the feeding pipe is communicated with the preheating mixing tank, and the three feeding hoppers are respectively used for filling o-ethylaniline, hydrochloric acid and water, the first static mixer is connected with the first buffer tank, the first circulation pump and the first circulation valve through pipelines to form a first circulation reaction device, a discharge pipe with a discharge valve is provided at the bottom of the preheating mixing tank, and the discharge pipe is communicated with the first circulation reaction device, the outlet of the first circulation pump is also connected with an amine salt discharge pipe, and the amine salt discharge pipe is provided with an amine salt discharge valve, The second static mixer is equipped with a second buffer tank, a second circulation pump and a second circulation valve. The second static mixer is connected to the second buffer tank, the second circulation pump and the second circulation valve through a pipeline to form a second circulation reaction device. The pipeline of the second circulation reaction device is also provided with a vertical formaldehyde feeding pipe, the formaldehyde feeding pipe is provided with a formaldehyde feeding valve, and the top of the formaldehyde feeding pipe is also connected to a formaldehyde feeding hopper. The amine salt discharge pipe is connected to the pipeline of the second circulation reaction device. The pipeline of the second circulation reaction device is also provided with a condensation product discharge pipe, and the condensation product discharge pipe is provided with a condensation product discharge valve. The first buffer tank and the second buffer tank are both provided with electric stirring.

[0024] With such a design, the salt-forming reaction of the hydrochloride of o-ethylaniline without an external solvent and the condensation reaction of the hydrochloride of o-ethylaniline with formaldehyde without an external solvent are realized through a simple equipment combination, and the process is simple and the reaction time is short.

[0025] The preferred technical solution is: the aforementioned special equipment also includes a neutralization separation tank, a first water washing tank, a second water washing tank, a vacuum distillation kettle, a filter, a condenser, a vacuum pump, a wastewater tank, a dehydration tank, a free amine removal tank and a finished product tank, the rearrangement reactor, the neutralization separation tank, the first water washing tank and the second water washing tank are connected in sequence through a discharge pipe with a discharge valve, and all are discharged from the bottom and fed from the top or upper part, the condensation product discharge pipe is connected to the rearrangement reactor, the neutralization separation tank, the first water washing tank and the second water washing tank are connected to the rearrangement reactor, and the neutralization separation tank, the first water washing tank and the second water washing tank are connected to the rearrangement reactor. The discharge pipe at the bottom of the washing tank is also provided with a pipeline sight glass, and is connected to a wastewater discharge pipe with a wastewater valve, the wastewater discharge pipes are all connected to the wastewater tank, the top of the neutralization separation tank is provided with a sodium hydroxide solution feeding pipe, the first water washing tank and the second water washing tank are respectively provided with water injection pipes, the water injection pipes are provided with water injection valves, the discharge pipe at the bottom of the second water washing tank is connected to the vacuum distillation kettle, the vacuum distillation kettle is provided with a nitrogen pressurizing pipe with a pressurizing valve, the nitrogen pressurizing pipe is connected to the high-pressure nitrogen source, the rearrangement reaction The kettle and the vacuum distillation kettle are provided with a thermometer and a circulation jacket, the circulation jacket is equipped with a steam heating system or a heating oil circulation system, the vacuum distillation kettle is also provided with a liquid discharge pipe and an evaporation gas discharge pipe, wherein one end of the liquid discharge pipe extends into the bottom of the vacuum distillation kettle, and the other end is communicated with the finished product tank, the filter is serially connected to the liquid discharge pipe, and the liquid discharge pipe between the filter and the vacuum distillation kettle is also provided with a finished product discharge valve, the evaporation gas discharge pipe is provided with a valve and is passed into the condenser, the bottom of the condenser is provided with a discharge pipe with a pipeline sight glass, the discharge pipe is communicated with two discharge branch pipes, the two discharge branch pipes are respectively provided with valves, and are respectively passed into the dehydration tank and the free amine removal tank, the dehydration tank and the free amine removal tank are respectively provided with vacuum branches, and the vacuum branches are all provided with valves, and are commonly communicated with the suction port of the vacuum pump, the rearrangement reactor, the neutralization separation tank, the first water washing tank, the second water washing tank, and the vacuum distillation kettle are all provided with motor stirring, and the condenser is equipped with a circulating water condensation system.

[0026] Such a design omits the complicated process and equipment of removing organic solvent (commonly used methanol or ethanol) compared with the prior art.

[0027] The preferred technical solution is: rectangular sight glasses are also provided on the side walls of the neutralization separation tank, the first water washing tank and the second water washing tank, and a rearrangement reactor discharge pump is also provided on the discharge pipe of the rearrangement reactor. With such a design, the addition of rectangular sight glasses facilitates the observation of the liquid stratification of the corresponding tanks; the addition of a rearrangement reactor discharge pump on the discharge pipe of the rearrangement reactor facilitates the pumping of the kettle liquid of the low-position rearrangement reactor into the high-position neutralization separation liquid tank, without having to place the rearrangement reactor above the neutralization separation liquid tank, and facilitates the arrangement of on-site equipment.

[0028] The preparation method and equipment of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention have short salt formation and condensation reaction time, high yield and high purity, and the finished product has light color, and is suitable for the production of 3,3'-diethyl-4,4'-diaminodiphenylmethane, and is particularly suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The preparation method and equipment of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention are further described below in conjunction with the accompanying drawings: Figure 1 It is a flow chart of the equipment of the present invention; Figure 2 It is a process flow chart of the present invention.

[0030] In the figure: 1 is a rearrangement reactor, 2 is a first static mixer, 3 is a second static mixer, 4 is a preheating mixing tank, 5 is a first buffer tank, 6 is a first circulation pump, 7 is a first circulation valve, 8 is an electric stirrer, 9 is a thermometer, 10 is a circulation jacket, 11 is a feeding hopper, 12 is a feeding valve, 13 is a feeding pipe, 14 is a discharge valve, 15 is a discharge pipe, 16 is an amine salt discharge pipe, 17 is an amine salt discharge valve, 18 is a second buffer tank, 19 is a second circulation pump, 20 is a second circulation valve, 21 is a formaldehyde feeding pipe, 22 is a formaldehyde feeding valve, 23 is a formaldehyde feeding hopper, 24 is a condensation product discharge pipe, 25 is a condensation product discharge valve, 26 is a neutralization separator The separation tank is 27, the first water washing tank, 28, the second water washing tank, 29, the vacuum distillation kettle, 30, the filter, 31, the condenser, 32, the vacuum pump, 33, the waste water tank, 34, the dehydration tank, 35, the free amine removal tank, 36, the finished product tank, 37, the pipeline sight glass, 38, the waste water valve, 39, the waste water discharge pipe, 40, the sodium hydroxide solution feeding pipe, 41, the water injection pipe, 42, the water injection valve, 43, the pressure valve, 44, the nitrogen pressure pipe, 45, the liquid discharge pipe, 46, the evaporated gas discharge pipe, 47, the finished product discharge valve, 48, the valve, 49, the discharge branch pipe, 50, the vacuum branch pipe, 51, the rectangular sight glass, and 52, the rearrangement kettle discharge pump. DETAILED DESCRIPTION

[0031] Example 1: Figure 1As shown, the special equipment for the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention comprises a rearrangement reactor 1, characterized in that it also comprises a first static mixer 2 and a second static mixer 3, wherein the first static mixer 2 is equipped with a preheating mixing tank 4, a first buffer tank 5, a first circulation pump 6 and a first circulation valve 7, wherein the preheating mixing tank 4 is provided with an electric stirrer 8, a thermometer 9 and a circulation jacket 10, the circulation jacket 10 is provided with a heating water or heating oil circulation system, a feeding hopper 11 is provided on the top of the preheating mixing tank 4, a feeding pipe 13 with a feeding valve 12 is connected to the bottom of the feeding hopper 11, and the feeding pipe 13 is communicated with the preheating mixing tank 4, and the three feeding hoppers 11 are respectively used for adding o-ethylaniline, hydrochloric acid and water.

[0032] The first static mixer 2 is connected to the first buffer tank 5, the first circulation pump 6 and the first circulation valve 7 through pipelines to form a first circulation reaction device. A discharge pipe 15 with a discharge valve 14 is provided at the bottom of the preheating mixing tank 4, and the discharge pipe 15 is communicated with the first circulation reaction device. The outlet of the first circulation pump 6 is also connected to an amine salt discharge pipe 16, and an amine salt discharge valve 17 is provided on the amine salt discharge pipe 16.

[0033] The second static mixer 3 is equipped with a second buffer tank 18, a second circulation pump 19 and a second circulation valve 20. The second static mixer 3 is connected with the second buffer tank 18, the second circulation pump 19 and the second circulation valve 20 through a pipeline to form a second circulation reaction device. A vertical formaldehyde feeding pipe 21 is also provided on the pipeline of the second circulation reaction device. A formaldehyde feeding valve 22 is provided on the formaldehyde feeding pipe 21. A formaldehyde feeding hopper 23 is also connected to the top of the formaldehyde feeding pipe 21. The amine salt discharge pipe 16 is communicated with the pipeline of the second circulation reaction device. A condensation product discharge pipe 24 is also provided on the pipeline of the second circulation reaction device. A condensation product discharge pipe 24 is provided on the condensation product discharge valve 25. The first buffer tank 5 and the second buffer tank 18 are both provided with an electric stirrer 8.

[0034] It includes a neutralization separation tank 26, a first water washing tank 27, a second water washing tank 28, a vacuum distillation kettle 29, a filter 30, a condenser 31, a vacuum pump 32, a waste water tank 33, a dehydration tank 34, a free amine removal tank 35 and a finished product tank 36. The rearrangement reactor 1, the neutralization separation tank 26, the first water washing tank 27 and the second water washing tank 28 are connected in sequence through a discharge pipe 15 with a discharge valve 14, and all are discharged from the bottom and fed from the top or upper part. The combined product discharge pipe 24 leads to the rearrangement reactor 1. The discharge pipes 15 at the bottom of the neutralization separation tank 26, the first water washing tank 27 and the second water washing tank 28 are also provided with a pipeline sight glass 37, and are connected to a wastewater discharge pipe 39 with a wastewater valve 38. The wastewater discharge pipes 39 all lead to the wastewater tank 33. A sodium hydroxide solution feeding pipe 40 is provided on the top of the neutralization separation tank 26, and a feeding valve 12 and a feeding hopper 11 are provided on the sodium hydroxide solution feeding pipe 40.

[0035] The first water washing tank 27 and the second water washing tank 28 are respectively provided with a water injection pipe 41, and the water injection pipe 41 is provided with a water injection valve 42. The bottom discharge pipe 15 of the second water washing tank 28 is connected to the vacuum distillation kettle 29. The vacuum distillation kettle 29 is provided with a nitrogen pressurizing pipe 44 with a pressurizing valve 43, and the nitrogen pressurizing pipe 44 is communicated with the matched high-pressure nitrogen source (not shown in the figure). The rearrangement reaction kettle 1 and the vacuum distillation kettle 29 are provided with a thermometer 9 and a circulation jacket 10, and the circulation jacket 10 is equipped with a steam heating system or a heating oil circulation system. The vacuum distillation kettle 29 is also provided with a liquid discharge pipe 45 and an evaporation gas discharge pipe 46, wherein one end of the liquid discharge pipe 45 extends into the bottom of the vacuum distillation kettle 29, and the other end is communicated with the finished product tank 36. The filter 30 is connected in series to the liquid discharge pipe 45, and the filter 30 is connected to the vacuum distillation kettle 29. A finished product discharge valve 47 is also provided on the liquid discharge pipe 45 between the distillation kettles 29, a valve 48 is provided on the evaporated gas discharge pipe 46, and the evaporation gas discharge pipe 46 is connected to the condenser 31, and a discharge pipe 15 with a pipeline sight glass 37 is provided at the bottom of the condenser 31, and the discharge pipe 15 is communicated with two discharge branches 49, and the two discharge branches 49 are respectively provided with valves 48, and are respectively connected to the dehydration tank 34 and the free amine removal tank 35, and the dehydration tank 34 and the free amine removal tank 35 are respectively provided with vacuum branches 50, and the vacuum branches 50 are all provided with valves 48, and are commonly connected to the suction port of the vacuum pump 32, the rearrangement reactor 1, the neutralization separation tank 26, the first water washing tank 27, the second water washing tank 28, and the vacuum distillation kettle 29 are all provided with motor stirring 8, and the condenser 31 is equipped with a circulating water condensation system.

[0036] A rectangular sight glass 51 is also provided on the side walls of the neutralization separation tank 26 , the first water washing tank 27 and the second water washing tank 28 , and a rearrangement reactor discharge pump 52 is also provided on the discharge pipe 15 of the rearrangement reactor 1 .

[0037] like Figure 2 As shown, the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention comprises the following steps: (1) o-ethylaniline, hydrochloric acid and water are passed through a first static mixer 2 to form o-ethylaniline hydrochloride; (2) and then condensed with formaldehyde solution in a second static mixer 3; (3) After high temperature rearrangement, alkali neutralization, water washing, dehydration and removal of free amine, and filtration, 3,3'-diethyl-4,4'-diaminodiphenylmethane is obtained.

[0038] The mass concentration of the hydrochloric acid is 31%; the molar ratio of o-ethylaniline to hydrochloric acid is 1:1.3.

[0039] The formaldehyde solution is a formaldehyde solution with a mass concentration of 37%; the molar ratio of o-ethylaniline hydrochloride to formaldehyde is 2.3:1, the mass flow ratio is 12.8:1, and the condensation temperature is 30° C. to 60° C.

[0040] The temperature of the reactor during rearrangement is 90°C to 110°C, and the rearrangement time is preferably 3 to 3.5 hours.

[0041] In step (1), the feed valve 12 on the feed pipe 13 of the preheating mixing tank 4 is opened, and corresponding amounts of o-ethylaniline 1580 kg, hydrochloric acid 2000 kg and water 2200 kg are taken and added into the preheating mixing tank 4 through the feed hopper 11 and its feed pipe 13. After the mixture is mixed in the preheating mixing tank 4 and heated to a temperature in the range of 20-52° C., the discharge valve 14 at the bottom of the preheating mixing tank 4 is opened, and the mixture enters the first circulation reaction device through the discharge pipe 15 at the bottom of the preheating mixing tank 4, and most of the mixture enters the first buffer tank 5. Then, the electric stirring 8 of the first buffer tank 5 is opened, the discharge valve 14 at the bottom of the preheating mixing tank 4 and the amine salt discharge valve 17 are closed, the first circulation pump 6 is opened, the first circulation valve 7 and other valves on the pipeline of the first circulation reaction device are opened, and the o-ethylaniline, hydrochloric acid and water are circulated in the first circulation reaction device. When the o-ethylaniline and hydrochloric acid pass through the first static mixer 2, they are mixed and reacted to form o-ethylaniline hydrochloride. After 40 to 60 minutes of this cycle, the reaction is complete and the process can proceed to step (2). Before the reaction of step (1) is completed, the formaldehyde feeding valve 22 is opened in advance, and 460 kg of formaldehyde is added to the second circulation reaction device through the formaldehyde feeding hopper 23 and the formaldehyde feeding pipe 21, and then the formaldehyde feeding valve 22 is closed. After the reaction of step (1) is completed, the amine salt discharge valve 17 is opened, the first circulation valve 7 is closed, and all the materials in the first circulation reaction device are pumped into the second circulation reaction device, and then the electric stirring 8 of the second buffer tank 28 is turned on, and the amine salt discharge valve 17 and the first circulation pump 6 are closed.

[0042] Then, the second circulation pump 19 is turned on, the second circulation valve 20 and other valves on the pipeline of the second circulation reaction device are opened, and the o-ethylaniline hydrochloride and formaldehyde generated in step (1) are circulated in the second circulation reaction device. The o-ethylaniline hydrochloride and formaldehyde are fully mixed when passing through the second static mixer 3 to generate a condensation product. After 40 to 60 minutes of circulation, the reaction is completed and the process can proceed to step (3).

[0043] Rearrangement reaction: After step (2) is completed, the condensation product discharge valve 25 is opened to allow the condensation product in the second circulation reaction device to enter the rearrangement reactor 1, and then the electric stirring 8 and the steam heating system or the heating oil circulation system of the rearrangement reactor 1 are turned on to increase the temperature in the rearrangement reactor 1 and maintain it in the range of 90°C to 110°C. After reacting for 3 to 3.5 hours, the rearrangement reaction is completed.

[0044] Neutralization: open the discharge valve 14 on the discharge pipe 15 at the bottom of the rearrangement reactor 1, put or pump the materials in the rearrangement reactor 1 into the neutralization separation tank 26, and then turn on the electric stirring 8 of the neutralization separation tank 26, so that the materials meet with 2490 kg of sodium hydroxide solution added through the sodium hydroxide solution feeding pipe 40 in the neutralization separation tank 26, and are fully mixed and neutralized. Then, the electric stirring 8 of the neutralization separation tank 26 is turned off, and the liquid in the neutralization separation tank 26 is allowed to stand and stratify. Then, the waste water valve 38 at the bottom of the neutralization separation tank 26 is opened, and the brine in the lower layer of the neutralization separation tank 26 is discharged into the waste water tank 33 through the waste water discharge pipe 39. After the brine is found to be discharged through the pipeline sight glass 37 at the bottom of the neutralization separation tank 26, the waste water valve 38 at the bottom of the neutralization separation tank 26 is closed, and then the discharge valve 14 on the discharge pipe 15 at the bottom of the neutralization separation tank 26 is opened. After the crude MOEA in the neutralization separation tank 26 is placed in the first water washing tank 27, the discharge valve 15 on the discharge pipe 15 at the bottom of the neutralization separation tank 26 is closed.

[0045] First water washing: open the water injection valve 42 on the first water washing tank 27, inject an appropriate amount of 2600 kg of hot water at 80℃~100℃ into the first water washing tank 27 through the water injection pipe 41, turn on the electric stirring 8 of the first water washing tank 27, and after 20-40 minutes, turn off the electric stirring 8 of the first water washing tank 27 to allow the liquid in the first water washing tank 27 to stand and stratify, then open the discharge valve 14 on the discharge pipe 15 at the bottom of the first water washing tank 27, and put the crude MOEA in the lower layer of the first water washing tank 27 into the second water washing tank 28. After the crude MOEA is discharged through the pipeline sight glass 37 at the bottom of the first water washing tank 27, close the discharge valve 14 on the discharge pipe 15 at the bottom of the first water washing tank 27, open the wastewater valve 38 at the bottom of the first water washing tank 27, and discharge all the remaining wastewater in the first water washing tank 27 into the wastewater tank 33 through the wastewater discharge pipe 39, completing the first water washing. Second water washing: open the water injection valve 42 on the second water washing tank 28, inject an appropriate amount of 2400 kg of hot water at 80°C to 100°C into the second water washing tank 28 through the water injection pipe 41, turn on the electric stirring 8 of the second water washing tank 28, and after 20-40 minutes, turn off the electric stirring 8 of the second water washing tank 28, let the liquid in the second water washing tank 18 stand and stratify, then open the discharge valve 14 on the discharge pipe 15 at the bottom of the second water washing tank 28, put the crude MOEA in the lower layer of the second water washing tank 28 into the vacuum distillation kettle 29, and after finding that the crude MOEA has been discharged through the pipeline sight glass 37 at the bottom of the second water washing tank 28, close the discharge valve 14 on the discharge pipe 15 at the bottom of the second water washing tank 28, open the wastewater valve 38 at the bottom of the second water washing tank 28, and discharge all the remaining wastewater in the second water washing tank 28 into the wastewater tank 33 through the wastewater discharge pipe 39, and complete the second water washing.

[0046] Dehydration: Open the circulating water system and vacuum pump 32 of condenser 31, then open valve 48 on evaporation gas discharge pipe 46, valve 48 on discharge branch pipe 49 at the bottom of condenser 31 communicating with dehydration tank 34, and valve 48 on vacuum branch pipe 50 communicating with dehydration tank 34, and open electric stirring 8 and steam heating system or heating oil circulation system of vacuum distillation kettle 29, raise the temperature in vacuum distillation kettle 29, and keep it in the range of 102℃~105℃, after water in rearrangement reactor 1 evaporates, enter condenser 31, condense into water in condenser 31, enter dehydration tank 34 through discharge pipe 15 at the bottom of condenser 31, gas that cannot be condensed is discharged through vacuum pump 32, observe pipeline sight glass 37 at the bottom of condenser 31, when no more liquid flows down from condenser 31, dehydration is finished; De-free amine: open the valve 48 on the discharge branch pipe 49 at the bottom of the condenser 31 connected to the de-free amine tank 35 and the valve 48 on the vacuum branch pipe 50 connected to the de-free amine tank 35, close the valve 48 on the discharge branch pipe 49 at the bottom of the condenser 31 connected to the dehydration tank 34 and the valve 48 on the vacuum branch pipe 50 connected to the dehydration tank 34, adjust the steam heating system or heating oil circulation system of the vacuum distillation kettle 29, increase the temperature in the vacuum distillation kettle 29, and maintain it at 180°C~ Within the range of 200°C, after the free amine in the rearrangement reactor 1 evaporates, it enters the condenser 31, and after being condensed into liquid in the condenser 31, it enters the free amine removal tank 35 through the bottom discharge pipe 15 of the condenser 31, and the gas that cannot be condensed is discharged through the vacuum pump 32. Observe the pipeline sight glass 37 at the bottom of the condenser 31. When no more liquid flows down the condenser, the free amine removal is completed, and the steam heating system or heating oil circulation system of the vacuum distillation reactor 29 and the vacuum pump 32 are turned off, and the valve 48 on the evaporation gas discharge pipe 46 is closed; Finished product discharge: open the pressure valve 43 on the nitrogen pressure pipe 44, introduce high-pressure nitrogen into the vacuum distillation kettle 29, open the finished product discharge valve 47, and press the liquid in the vacuum distillation kettle 29 into the filter 30 through the liquid discharge pipe 45. The liquid filtered by the filter 30 is the finished product MOEA, and the finished product MOEA is injected into the finished product tank 36 through the liquid discharge pipe 45. The obtained MOEA is a yellow clear liquid, totaling 1300kg, with a purity of 93.8% after chromatographic detection, 5.5% polynuclear body, 99.3% effective substance content, 0.15% free amine, and a viscosity of 1760cps@25℃. 193.4kg (purity 99%) of o-ethylaniline is recovered, and the effective yield is 89.6% in terms of o-ethylaniline and after deducting the unreacted free amine in terms of MOEA.

[0047] The following is the laboratory preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane of the present invention: Example 2: 2000 g of hydrochloric acid with a mass fraction of 31%, 2200 g of water, and 1580 g of o-ethylaniline were added to a closed mixing tank equipped with a stirring paddle, a thermometer, and a jacket, and stirred evenly while maintaining the temperature of the mixed solution at about 50°C. The mixture was pumped into the first static mixer at a flow rate of 48.5 g / s using a peristaltic pump. The o-ethylaniline hydrochloride solution and 37% formaldehyde solution flowing out of the first static mixer were pumped into the second static mixer at a flow rate of 48.5 g / s and 3.8 g / s, respectively, to maintain the temperature of the mixed solution at about 50°C.

[0048] The condensation liquid flowing out of the static mixer 2 was pumped into a 10-liter rearrangement reactor at a temperature of 95°C, and the rearrangement was completed after stirring and keeping warm for 2 hours.

[0049] The hydrochloric acid solution of aromatic amine is neutralized with a sodium hydroxide solution with a mass fraction of 30%, and the molar ratio of sodium hydroxide to hydrochloric acid is 1.1:1. After alkali neutralization, the upper organic phase after standing and stratification is washed with pure water for at least 2 times. The washed organic phase is vacuum dehydrated and free amine is removed. The vacuum degree during dehydration is 0.07-0.08 MPa and the temperature is 102°C-105°C. The vacuum degree for removing free amine is 0.08-0.1 MPa and the temperature is 180°C-200°C. 1320 g of yellow and clear MOEA is obtained. The purity is 94.7% after chromatographic detection, the polynuclear body is 4.4%, the effective substance content is 99.1%, the free amine is 0.12%, the viscosity is 1760 cps@25°C, 192.4 g of o-ethylaniline (purity 99%) is recovered, and the effective substance yield based on MOEA is 90.7%.

[0050] Example 3: A method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane The experimental operation was the same as in Example 2. The feed flow rates of o-ethylaniline hydrochloride and formaldehyde entering the second static mixer were adjusted to 45 g / s and 4.4 g / s, respectively. After high-temperature rearrangement, alkali washing, water washing, water / free amine removal, and filtration, 1503 g of dark yellow MOEA was obtained. The purity was 90.1% by chromatographic detection, the polynuclear body was 9.3%, the effective substance content was 99.4%, the free amine was 0.11%, and the viscosity was 1870 cps@25°C. 32.1 g of o-ethylaniline (purity 99%) was recovered, and the effective substance yield based on MOEA was 92.9%.

[0051] Example 4: A method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane The experimental operation was the same as in Example 2, except that the rearrangement temperature was lowered to 75°C, and after alkali washing, water washing, water / free amine removal and filtration, 1270 g of yellow clear MOEA was obtained. The purity was 92.6% by chromatographic detection, the polynuclear body was 6.5%, the effective substance content was 99.1%, the free amine was 0.55%, and the viscosity was 1920 cps@25°C. 191.2 g of o-ethylaniline was recovered, and the effective substance yield based on MOEA was 87.2%.

[0052] Comparative Examples 1-4 show that: by eliminating the alcohol solvent in the original 3,3'-diethyl-4,4'-diaminodiphenylmethane synthesis process and using a static mixer for the condensation step, the purity of the target product not only does not decrease significantly, but is improved. At the same time, the use of a static mixer can also shorten the original condensation time, and the production efficiency is improved. It can be seen from Example 3 that when the formaldehyde content in the raw material ratio is increased, the polymer content in the product will increase and the color will deepen. It can be seen from Example 4 that the increase in the rearrangement reaction temperature is conducive to the rearrangement of the condensate to form a dinuclear body, reducing the content of the polynuclear body.

[0053] The purity of the o-ethylaniline used above is 99%.

[0054] The above description is only used to explain the preferred embodiments of the present invention, and is not intended to limit the present invention in any form. Any modifications or changes made to the present invention under the same inventive spirit should still be included in the scope of protection intended by the present invention.

Claims

1. A method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane, characterized in that: (1) o-ethylaniline, hydrochloric acid and water are passed through a first static mixer to form o-ethylaniline hydrochloride; (2) Then condense with formaldehyde solution in a second static mixer; (3) After high temperature rearrangement, alkali neutralization, water washing, dehydration and removal of free amine, and filtration, 3,3'-diethyl-4,4'-diaminodiphenylmethane is obtained.

2. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 1, characterized in that: The mass concentration of hydrochloric acid is 25-36%; the molar ratio of o-ethylaniline to hydrochloric acid is 1:1-1:

2.

3. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 1, characterized in that: The formaldehyde solution has a mass concentration of 20-37%; the molar ratio of o-ethylaniline hydrochloride to formaldehyde is 1.9:1-3:1, and the condensation temperature is 30°C-60°C.

4. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 1, characterized in that: During rearrangement, the temperature of the reactor is 80°C to 110°C, and the rearrangement time is 2 to 6 hours.

5. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 1, characterized in that: The temperature of the reactor during rearrangement is 90°C to 110°C, and the rearrangement time is preferably 2 to 4 hours.

6. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 1, characterized in that: Step (1) The first static mixer is also equipped with a preheating mixing tank, a first buffer tank, a first circulation pump and a first circulation valve, wherein the preheating mixing tank is provided with an electric stirrer, a thermometer and a circulation jacket, the circulation jacket is provided with a heating water or heating oil circulation system, a feeding hopper is provided on the top of the preheating mixing tank, a feeding pipe with a feeding valve is connected to the bottom of the feeding hopper, and the feeding pipe is communicated with the preheating mixing tank, and the three feeding hoppers are used to add o-ethylaniline, hydrochloric acid and water respectively, the first static mixer is connected to the first buffer tank, the first circulation pump and the first circulation valve through pipelines to form a first circulation reaction device, a discharge pipe with a discharge valve is provided at the bottom of the preheating mixing tank, and the discharge pipe is communicated with the first circulation reaction device, the outlet of the first circulation pump is also connected to an amine salt discharge pipe, and the amine salt discharge pipe is provided with an amine salt discharge valve, the first buffer tank is provided with an electric stirrer, In step (1), open the feeding valve on the feeding pipe of the preheating mixing tank, take corresponding amounts of o-ethylaniline, hydrochloric acid and water, add them into the preheating mixing tank through the feeding hopper and its feeding pipe, mix them in the preheating mixing tank, and heat them to a temperature in the range of 20-52° C., then open the discharge valve at the bottom of the preheating mixing tank, and enter the first circulation reaction device through the discharge pipe at the bottom of the preheating mixing tank, and most of them enter the first buffer tank, then start the electric stirring of the first buffer tank, close the discharge valve and amine salt discharge valve at the bottom of the preheating mixing tank, start the first circulation pump, open the first circulation valve and other valves on the pipeline of the first circulation reaction device, and o-ethylaniline, hydrochloric acid and water circulate in the first circulation reaction device, and o-ethylaniline and hydrochloric acid mix and react to form o-ethylaniline hydrochloride when passing through the first static mixer. After 40 to 60 minutes of such circulation, the reaction is completed and step (2) can be entered; In step (2), the second static mixer is also equipped with a second buffer tank, a second circulation pump and a second circulation valve. The second static mixer, the second buffer tank, the second circulation pump and the second circulation valve are connected to form a second circulation reaction device through a pipeline. The pipeline of the second circulation reaction device is also equipped with a vertical formaldehyde feeding pipe, the formaldehyde feeding pipe is equipped with a formaldehyde feeding valve, and the top of the formaldehyde feeding pipe is also connected to a formaldehyde feeding hopper. The amine salt discharge pipe is connected to the pipeline of the second circulation reaction device. The pipeline of the second circulation reaction device is also equipped with a condensation product discharge pipe, the condensation product discharge pipe is equipped with a condensation product discharge valve, and the second buffer tank is equipped with an electric stirring device. Before the reaction of step (1) is completed, the formaldehyde feeding valve is opened in advance, and a proper amount of formaldehyde is added to the second circulation reaction device through the formaldehyde feeding hopper and the formaldehyde feeding pipe, and then the formaldehyde feeding valve is closed. After the reaction of step (1) is completed, the amine salt discharge valve is opened, the first circulation valve is closed, and all the materials in the first circulation reaction device are pumped into the second circulation reaction device, and then the electric stirring of the second buffer tank is turned on, and the amine salt discharge valve and the first circulation pump are closed. Then, the second circulation pump is turned on, and the second circulation valve and other valves on the pipeline of the second circulation reaction device are opened. The o-ethylaniline hydrochloride and formaldehyde generated in step (1) are circulated in the second circulation reaction device. The o-ethylaniline hydrochloride and formaldehyde are fully mixed when passing through the second static mixer to generate a condensation product. After 40 to 60 minutes of circulation, the reaction is completed and the process can proceed to step (3).

7. The method for preparing 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 6, characterized in that: The equipment required for step (3) includes a rearrangement reactor, a neutralization separation tank, a first water washing tank, a second water washing tank, a vacuum distillation kettle, a filter, a condenser, a vacuum pump, a waste water tank, a dehydration tank, a free amine removal tank and a finished product tank. The rearrangement reactor, the neutralization separation tank, the first water washing tank and the second water washing tank are connected in sequence through a discharge pipe with a discharge valve, and all discharge from the bottom and feed from the top or upper part. The condensation product discharge pipe leads into the rearrangement reactor. The discharge pipes at the bottom of the neutralization separation tank, the first water washing tank and the second water washing tank are also provided with a pipeline sight glass, and are connected with a wastewater discharge pipe with a wastewater valve. The wastewater discharge pipes all lead to the wastewater tank. A sodium hydroxide solution feeding pipe is provided on the top of the neutralization separation tank. Water injection pipes are respectively provided on the first water washing tank and the second water washing tank. The water injection pipes are provided with a water injection valve. The discharge pipe at the bottom of the second water washing tank leads to the vacuum distillation kettle. A nitrogen pressurizing pipe with a pressurizing valve is provided on the vacuum distillation kettle. The nitrogen pressurizing pipe is communicated with a high-pressure nitrogen source. The rearrangement reactor and the vacuum distillation kettle are both provided with a thermometer and a circulation jacket. The circulation jacket is equipped with a steam heating system or a heating oil circulation system. The system comprises a liquid discharge pipe and an evaporation gas discharge pipe, wherein one end of the liquid discharge pipe extends into the bottom of the vacuum distillation kettle, and the other end is connected to the finished product tank. The filter is connected in series to the liquid discharge pipe, and a finished product discharge valve is provided on the liquid discharge pipe between the filter and the vacuum distillation kettle. The evaporation gas discharge pipe is provided with a valve and is connected to the condenser. The bottom of the condenser is provided with a discharge pipe with a pipeline sight glass, and the discharge pipe is connected to two discharge branches, and valves are provided on the two discharge branches, and are respectively connected to the dehydration tank and the free amine removal tank. The dehydration tank and the free amine removal tank are respectively provided with vacuum branches, and valves are provided on the vacuum branches, and are commonly connected to the suction port of the vacuum pump. The rearrangement reactor, the neutralization separation tank, the first water washing tank, the second water washing tank, and the vacuum distillation kettle are all provided with electric stirring, and the condenser is equipped with a circulating water condensation system. Rearrangement reaction: After step (2), the condensation product discharge valve is opened to allow the condensation product in the second circulation reaction device to enter the rearrangement reaction kettle, and then the electric stirring and steam heating system or heating oil circulation system of the rearrangement reaction kettle is turned on to increase the temperature in the rearrangement reaction kettle and maintain it in the range of 90°C to 110°C. After 2 to 4 hours of reaction, the rearrangement reaction is completed. Neutralization: open the discharge valve on the discharge pipe at the bottom of the rearrangement reactor, put the material in the rearrangement reactor into or pump it into the neutralization separation tank, then turn on the electric stirring of the neutralization separation tank, and meet the sodium hydroxide solution added through the sodium hydroxide solution feeding pipe in the neutralization separation tank. After fully mixing and neutralizing, turn off the electric stirring of the neutralization separation tank, let the liquid in the neutralization separation tank stand and stratify, then open the wastewater valve at the bottom of the neutralization separation tank, and discharge the brine in the lower layer of the neutralization separation tank into the wastewater tank through the wastewater discharge pipe. After finding that the brine has been discharged through the pipeline sight glass at the bottom of the neutralization separation tank, close the wastewater valve at the bottom of the neutralization separation tank, then open the discharge valve on the discharge pipe at the bottom of the neutralization separation tank, put the crude MOEA in the neutralization separation tank into the first water washing tank, and then close the discharge valve on the discharge pipe at the bottom of the neutralization separation tank. First water washing: open the water injection valve on the first water washing tank, inject an appropriate amount of hot water at 80℃~100℃ into the first water washing tank through the water injection pipe, turn on the electric stirring of the first water washing tank for 20-40 minutes, then turn off the electric stirring of the first water washing tank, let the liquid in the first water washing tank stand and stratify, then open the discharge valve on the discharge pipe at the bottom of the first water washing tank, put the crude MOEA in the lower layer of the first water washing tank into the second water washing tank, and after finding that the crude MOEA has been discharged through the pipeline sight glass at the bottom of the first water washing tank, close the discharge valve on the discharge pipe at the bottom of the first water washing tank, open the wastewater valve at the bottom of the first water washing tank, and discharge all the remaining wastewater in the first water washing tank into the wastewater tank through the wastewater discharge pipe, completing the first water washing; Second water washing: open the water injection valve on the second water washing tank, inject an appropriate amount of hot water at 80℃~100℃ into the second water washing tank through the water injection pipe, turn on the electric stirring of the second water washing tank for 20-40 minutes, then turn off the electric stirring of the second water washing tank, let the liquid in the second water washing tank stand and stratify, then open the discharge valve on the discharge pipe at the bottom of the second water washing tank, put the crude MOEA in the lower layer of the second water washing tank into the vacuum distillation kettle, and after finding that the crude MOEA has been discharged through the pipeline sight glass at the bottom of the second water washing tank, close the discharge valve on the discharge pipe at the bottom of the second water washing tank, open the wastewater valve at the bottom of the second water washing tank, and discharge all the remaining wastewater in the second water washing tank into the wastewater tank through the wastewater discharge pipe, completing the second water washing; Dehydration: Open the circulating water system and vacuum pump of the condenser, then open the valve on the evaporation gas discharge pipe, the valve on the discharge branch pipe connected to the dehydration tank at the bottom of the condenser, and the valve on the vacuum branch pipe connected to the dehydration tank, and open the electric stirring and steam heating system or heating oil circulation system of the vacuum distillation kettle, raise the temperature in the vacuum distillation kettle, and keep it in the range of 102℃~105℃. After the water in the rearrangement reactor evaporates, it enters the condenser, and after condensing into water in the condenser, it enters the dehydration tank through the bottom discharge pipe of the condenser. The gas that cannot be condensed is discharged through the vacuum pump. Observe the pipeline sight glass at the bottom of the condenser. When no liquid flows down the condenser, the dehydration is over; Removal of free amine: open the valve on the discharge branch pipe connected to the free amine tank at the bottom of the condenser and the valve on the vacuum branch pipe connected to the free amine tank, close the valve on the discharge branch pipe connected to the dehydration tank at the bottom of the condenser and the valve on the vacuum branch pipe connected to the dehydration tank, adjust the steam heating system or heating oil circulation system of the vacuum distillation kettle, increase the temperature in the vacuum distillation kettle, and keep it in the range of 180℃~200℃, after the free amine in the rearrangement reactor evaporates, it enters the condenser, and after condensing into liquid in the condenser, it enters the free amine tank through the bottom discharge pipe of the condenser, and the gas that cannot be condensed is discharged through the vacuum pump, observe the pipeline sight glass at the bottom of the condenser, when there is no more liquid flowing down the condenser, the free amine is finished, close the steam heating system or heating oil circulation system and vacuum pump of the vacuum distillation kettle, and close the valve on the discharge pipe of the evaporated gas; Finished product discharge: Open the pressure valve on the nitrogen pressure pipe, introduce high-pressure nitrogen into the vacuum distillation kettle, open the finished product discharge valve, and press the liquid in the vacuum distillation kettle into the filter through the liquid discharge pipe. The liquid filtered by the filter is the finished product MOEA, and the finished product MOEA is injected into the finished product tank through the liquid discharge pipe.

8. A special equipment for the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 7, comprising a rearrangement reaction kettle, characterized in that: The invention comprises a first static mixer and a second static mixer, wherein the first static mixer is provided with a preheating mixing tank, a first buffer tank, a first circulation pump and a first circulation valve, wherein the preheating mixing tank is provided with an electric stirrer, a thermometer and a circulation jacket, the circulation jacket is provided with a heating water or heating oil circulation system, a feeding hopper is provided at the top of the preheating mixing tank, a feeding pipe with a feeding valve is connected to the bottom of the feeding hopper, and the feeding pipe is communicated with the preheating mixing tank, and the three feeding hoppers are used for adding o-ethylaniline, hydrochloric acid and water respectively, the first static mixer is connected with the first buffer tank, the first circulation pump and the first circulation valve through pipelines to form a first circulation reaction device, a discharge pipe with a discharge valve is provided at the bottom of the preheating mixing tank, and the discharge pipe is communicated with the first circulation reaction device, the outlet of the first circulation pump is also connected with an amine salt discharge pipe, and the amine salt discharge pipe is provided with an amine salt discharge valve, The second static mixer is equipped with a second buffer tank, a second circulation pump and a second circulation valve. The second static mixer is connected to the second buffer tank, the second circulation pump and the second circulation valve through a pipeline to form a second circulation reaction device. The pipeline of the second circulation reaction device is also provided with a vertical formaldehyde feeding pipe, the formaldehyde feeding pipe is provided with a formaldehyde feeding valve, and the top of the formaldehyde feeding pipe is also connected to a formaldehyde feeding hopper. The amine salt discharge pipe is connected to the pipeline of the second circulation reaction device. The pipeline of the second circulation reaction device is also provided with a condensation product discharge pipe, and the condensation product discharge pipe is provided with a condensation product discharge valve. The first buffer tank and the second buffer tank are both provided with electric stirring.

9. The special equipment for the preparation method of 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 8, characterized in that: The rearrangement reactor comprises a neutralization separation tank, a first water washing tank, a second water washing tank, a vacuum distillation kettle, a filter, a condenser, a vacuum pump, a waste water tank, a dehydration tank, a free amine removal tank and a finished product tank. The rearrangement reactor, the neutralization separation tank, the first water washing tank and the second water washing tank are connected in sequence through a discharge pipe with a discharge valve, and are all discharged from the bottom and fed from the top or upper part. The condensation product discharge pipe is connected to the rearrangement reactor. The discharge pipes at the bottom of the neutralization separation tank, the first water washing tank and the second water washing tank are also provided with The pipeline sight glass is connected to a wastewater discharge pipe with a wastewater valve, and the wastewater discharge pipes are all connected to the wastewater tank. A sodium hydroxide solution feeding pipe is provided on the top of the neutralization separation tank. A water injection pipe is provided on the first water washing tank and the second water washing tank respectively. The water injection pipe is provided with a water injection valve. The discharge pipe at the bottom of the second water washing tank is connected to the vacuum distillation kettle. A nitrogen pressurizing pipe with a pressurizing valve is provided on the vacuum distillation kettle. The nitrogen pressurizing pipe is connected to the high-pressure nitrogen source. The rearrangement reactor and the vacuum distillation kettle are connected to the rearrangement reactor and the vacuum distillation kettle. A thermometer and a circulation jacket are provided, and the circulation jacket is equipped with a steam heating system or a heating oil circulation system. A liquid discharge pipe and an evaporation gas discharge pipe are also provided on the vacuum distillation kettle, wherein one end of the liquid discharge pipe extends into the bottom of the vacuum distillation kettle, and the other end is communicated with the finished product tank. The filter is connected in series to the liquid discharge pipe, and a finished product discharge valve is also provided on the liquid discharge pipe between the filter and the vacuum distillation kettle. A valve is provided on the evaporation gas discharge pipe and leads to the condenser. A discharge pipe with a pipeline sight glass is provided at the bottom of the condenser, and the discharge pipe is communicated with two discharge branches, and valves are respectively provided on the two discharge branches, and respectively lead to the dehydration tank and the free amine removal tank. The dehydration tank and the free amine removal tank are respectively provided with vacuum branches, and valves are provided on the vacuum branches, and are commonly communicated with the suction port of the vacuum pump. The rearrangement reactor, the neutralization separation tank, the first water washing tank, the second water washing tank, and the vacuum distillation kettle are all provided with motor stirring, and the condenser is equipped with a circulating water condensation system.

10. The special equipment for the preparation of 3,3'-diethyl-4,4'-diaminodiphenylmethane according to claim 8 or 9, characterized in that: The side walls of the neutralization separation tank, the first water washing tank and the second water washing tank are also provided with rectangular sight glasses, and the discharge pipe of the rearrangement reactor is also provided with a rearrangement reactor discharge pump.

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