Preparation method of diamine and polyamine of diphenylmethane series

Abstract

The invention relates to a preparation method of diphenylmethane series diamine and polyamine, which comprises the following steps: reacting formaldehyde and aniline in the presence of an acid catalyst to prepare diphenylmethane series diamine and polyamine, sequentially neutralizing and washing the polyamine, and removing excessive aniline by adopting a vacuum distillation mode to prepare a qualified product. The trioxymethylene in the recycled aniline is removed by treating the recycled aniline, so that polycyclic high-polymer blockages, N-heterocyclic polyamine and N-methylaniline impurities in the reaction process can be greatly reduced, and the operation stability and the quality of an MDI product are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of diamine and polyamine of diphenylmethane series, and mainly relates to a preparation method of diamine and polyamine of diphenylmethane series. BACKGROUND

[0002] The diamine and polyamine of diphenylmethane series (DAM) can be understood as the amine of the type shown in the following general formula and mixtures thereof:

[0003]

[0004] In the general formula, n represents a natural number greater than or equal to 0, and when n = 0, the corresponding compound is called diamino diphenylmethane, simply referred to as diamine; when n > 0, the corresponding compound is called polyamine-based polyphenylmethane, simply referred to as polyamine; and the mixture of the two types of compounds is called diamine and polyamine of the diamino diphenylmethane series. The product derived by substituting all NH2 groups in DAM with NCO groups is isocyanate of the diamino diphenylmethane series (hereinafter referred to as MDI), which can be used for producing polyurethane.

[0005] In the field, the preparation method of DAM is generally known, and is described in many published patent documents and publications. Generally, aniline is first condensed with formaldehyde in the presence of an acid catalyst to perform a shift reaction, then the crude product containing diamine and polyamine is obtained by neutralization with lye and water washing, and then the crude product is refined to remove aniline and water to obtain the diamine and polyamine DAM product of diphenylmethane.

[0006] There are two problems in the production of DAM, respectively, the blockage leads to long-term stable operation, and the by-products (such as N-methyl, Schiff base) lead to abnormal MDI series product quality and color number deepening. In terms of alleviating the generation of blockage, such as the disclosed patent CN118164859, it is mentioned that the heat transfer mode in the condensation process of formaldehyde and aniline is changed to use the phase change of low bubble point and low viscosity substances in the system to transfer heat, thereby solving the problem of heat exchanger blockage, but it cannot essentially reduce the generation of blockage. The disclosed patent CN103084134 mentions using a dynamic hole jet mixing reactor to enhance the shear mixing of high viscosity materials, avoiding the generation of high molecular weight high viscosity impurities due to local excess of formaldehyde, leading to blockage, but this scheme is only limited to solving the blockage in the pre-condensation stage, and does not pay attention to the generation of blockage in the transfer stage. The disclosed patent US3260751 provides a "L" type mixing reactor to ensure that aniline hydrochloride is in a turbulent flow state during reaction with formaldehyde, thereby avoiding the formation of high molecular weight impurities on the equipment. In terms of improving the color number of MDI, the disclosed patent US7528283 provides a production method using recycled aniline containing 0.01-1% mass MDA mixed with fresh aniline and then reacted with formaldehyde to improve the color number of MDI, but the patent describes how to accurately control the DAM content in aniline, which is difficult to operate in production. The disclosed patent CN101538204 provides a scheme for controlling the carbonyl compound in the raw material aniline to be less than 0.25% for producing MDA, which can improve the color number of MDI, but this scheme is only limited to the problem of carbonyl color number, in fact, the factors affecting the color number of MDI are more complex. These known methods can only alleviate the influence of blockage on long-term stable operation of the process, and cannot completely eliminate the generation of blockage. The above patents can delay the influence of blockage in the production process of MDA and improve the color problem of the produced MDI by changing the heat transfer form, mixing method, raw material index and intermediate product index control, etc., then, new methods are still needed to better solve the blockage influence and better improve the color. SUMMARY

[0007] In view of the problems in the prior art, the inventors of the present application have found through a large number of experimental researches that trace amounts of trioxane are generated in the precondensation reaction of aniline and formaldehyde solution, and the trioxane is depolymerized into formaldehyde in the condensation and high-temperature rearrangement process, thereby causing the local formaldehyde concentration to be too high, and generating polycyclic polymers, N-containing heterocyclic polyamine substances and N-methylaniline impurities. In the high-temperature neutralization process of the rearrangement liquid with lye, the N-containing heterocyclic polyamine substances are further hydrolyzed to form Schiff base structures, and the trioxane in the rearrangement liquid is also gradually depolymerized into formaldehyde, which then reacts with the amino groups in the polyamines to generate Schiff base impurities. The operating temperature and PH in the lye neutralization process have a great influence on the hydrolysis rate of the N-containing heterocyclic polyamine substances and the depolymerization rate of the trioxane. Once the system redundancy is exceeded, the blockages will be aggregated and blocked, or the quality and color number of the MDI product will be affected.

[0008] Further in-depth research has shown that, through in-depth research on condensation, the inventors have found that the trioxane in the condensation process system is finally enriched in the recovered aniline at the top of the DAM refining tower, and the recovered aniline is mixed with fresh aniline and then subjected to condensation and rearrangement reactions again. The trioxane in the condensation reaction system mainly comes from the recovered aniline.

[0009] Therefore, a method for removing unreacted trioxane in the condensation process and reducing the influence of trioxane is developed, which can effectively reduce the generation of blockages and improve the quality of MDI products.

[0010] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0011] The present application provides a preparation method of diphenylmethane series diamines and polyamines, comprising the step of reacting aniline with formaldehyde in the presence of an acid catalyst, wherein the aniline comprises fresh aniline and recovered aniline, and the content of trioxane in the recovered aniline is ≤100 ppm, preferably ≤1 ppm, more preferably 0.1-1 ppm, and the content of trioxane includes but is not limited to 0.2 ppm, 0.5 ppm, 2 ppm, 5 ppm, 8 ppm, 12 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 35 ppm, 40 ppm, 45 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, or a range formed by any two of them.

[0012] As a preferred scheme, the preparation method comprises the following steps:

[0013] S1: fresh aniline and recovered aniline are mixed to serve as raw aniline, and the raw aniline is reacted with an acid catalyst to obtain aniline salt;

[0014] S2: mixing the formaldehyde aqueous solution with the aniline salt of step S1 to sequentially perform condensation reaction and rearrangement reaction to obtain polyamine reaction liquid;

[0015] S3: the reaction solution obtained in step S2 is sequentially subjected to neutralization treatment and water washing treatment to obtain a water-washed polyamine liquid;

[0016] S4: the water-washed polyamine liquid obtained in step S3 is subjected to vacuum rectification to obtain product DAM, and the overhead gas phase is cooled to obtain an aniline and water organic phase, and the recovered aniline and recovered water are obtained after phase separation;

[0017] S5: the recovered aniline obtained in step S4 is subjected to rectification treatment to remove trioxane in the recovered aniline, and the content of trioxane in the refined recovered aniline is ≤100 ppm, preferably ≤1 ppm, and more preferably 0.1-1 ppm; the overhead gas phase is condensed and subjected to phase separation to obtain a waste organic phase and recovered water, and the refined recovered aniline is obtained at the bottom of the column and is sent to step S1 to be mixed with fresh aniline and then subjected to reaction again.

[0018] In the present application, the fresh aniline in step S1 is obtained from qualified aniline product produced by liquid-phase or gas-phase hydrogenation of nitrobenzene, and the recovered aniline is obtained from the refined recovered aniline in step S5. The acid catalyst includes any one or a combination of hydrochloric acid, sulfuric acid and phosphoric acid, and hydrochloric acid is preferred. The mass fraction of the solute of the acid solution is 20-37%, and preferably 30-35%. The H + The molar ratio of formaldehyde to aniline is (0.01-0.5):1.

[0019] In the present application, in step S2, the mass concentration of formaldehyde in the formaldehyde aqueous solution is 20-55%, and preferably 30-50%, and the content of trioxane is ≤10 ppm. The molar ratio of formaldehyde molecules to aniline in the formaldehyde aqueous solution is (0.3-0.8):1. The condensation reaction temperature is 30-100℃, and the condensation reaction time is 10-100 min. The rearrangement reaction temperature is 80-150℃, and the rearrangement reaction time is 1-5 h.

[0020] In the present application, in step S3, caustic soda is used for neutralization, the concentration of caustic soda is 30-50 wt%, the neutralization temperature is controlled to 60-110℃, and preferably 60-90℃, the neutralization pH is controlled to 8-12, and preferably 8-10.5. The polyamine is further subjected to water washing treatment after neutralization.

[0021] In the present application, in step S4, the polyamine after washing is removed by vacuum distillation, the polyamine feed is preheated to 100-250°C, preferably 150-200°C by a heat exchanger, steam is introduced into the distillation column to strip, the steam pressure is controlled at 50-3000kpaA, preferably 80-2000kpaA. The distillation column pressure is controlled at 1-20KpaA, preferably 5-10kpaA. The gas phase at the top of the column is condensed to obtain condensate, which is separated by a phase separator to obtain recovered aniline and recovered water, and the phase separator can be a static phase separator or a coalescence phase separator.

[0022] In the present application, in step S5, the recovered aniline is subjected to distillation treatment, the distillation pressure is controlled at 1-101KpaA, preferably 10-101KpaA, the overhead temperature is controlled at 30-120°C, preferably 60-120°C, the overhead reflux ratio is 0.1-3, preferably 0.1-1, and the overhead light component recovery ratio is 0.03-0.1, preferably 0.03-0.06. After refining treatment, the recovered aniline contains ≤100ppm, preferably ≤1ppm, more preferably 0.1-1ppm of trioxymethylene.

[0023] Compared with the prior art, the technical solution of the present application has the following beneficial effects:

[0024] (1) By removing the residual trioxymethylene in the recovered aniline through distillation treatment, the accumulation of trioxymethylene in the condensation reaction system is effectively avoided, thereby reducing the generation of polycyclic high polymer blockage and N-containing heterocyclic polyamine substances and N-methylaniline impurities in the condensation and transposition processes, which can greatly improve the operation stability of the condensation reaction and improve the quality and color number of MDI made from DAM.(2) By controlling the temperature and PH of the reaction liquid neutralization process, the generation of Schiff base impurities is effectively slowed down, which can further improve the product quality and color number of MDI made from DAM, so that the content of ketone impurities in the raw material aniline can be relaxed, and the energy consumption of the aniline production process can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The preparation process flowchart of the diphenylmethane series diamine and polyamine in the prior art.

[0026] Figure 2 The preparation process flowchart of the diphenylmethane series diamine and polyamine in the present application. DETAILED DESCRIPTION

[0027] The specific implementation of the present method will be further illustrated below in conjunction with examples. However, the present application is not limited to the listed examples, and any other known changes within the scope of the claimed rights of the present application should also be included.

[0028] The sources of raw materials in the following examples are as follows:

[0029] Aniline: Produced in Wanhua Chemical Group Co., Ltd. Industrial Park, with a mass concentration of 99.9 wt%; Hydrochloric acid: Produced in Wanhua Industrial Park, with a mass concentration of 33 wt%; Formaldehyde: Produced in Wanhua Industrial Park, with a mass concentration of 30 wt%-50 wt%; Sodium hydroxide solution: Produced in Wanhua Industrial Park, with a mass concentration of 32-50 wt%; The above four raw materials can also be commercially available products that meet national standards and the above concentrations.

[0030] The method for measuring blockage in the reaction solution involves filtering 500g of the reaction solution through a 0.22µm filter membrane, then washing and drying the solids on the filter membrane with ethanol to obtain the dry basis solids content. The dry basis solids mass / reaction solution mass is the blockage content in the reaction solution.

[0031] N-methylaniline in product DAM and paraformaldehyde in recovered aniline were analyzed using an Agilent gas chromatograph 7890A, and the methods are shown in the table.

[0032]

[0033] Comparative Example 1

[0034] like Figure 1 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 30 ppm total ketones, and recovered aniline contains 5000 ppm paraformaldehyde. The recovered and fresh aniline are mixed and reacted with 33% hydrochloric acid at a hydrochloric acid / aniline molar ratio of 0.3. Then, a pre-condensation reaction is carried out with 50% formaldehyde (10 ppm paraformaldehyde) at 60°C for 100 min at a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 110°C and pH 12. After neutralization, the polyamine is further washed with water. Following washing, the polyamine undergoes vacuum distillation (polyamine feed temperature 190°C, distillation column pressure controlled at 8 kPaA) to obtain the DAM product. The recovered aniline is separated at the top of the column and returned to the reaction unit. Under these conditions, the blockage content in the reaction solution is 100 ppm, and the DAM product contains approximately 0.4% N-methylaniline. The purified DAM and chlorobenzene were mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene were subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 30# was obtained.

[0035] Comparative Example 2

[0036] like Figure 1The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 30 ppm total ketones, and the recovered aniline contains 200 ppm paraformaldehyde (this paraformaldehyde content in the recovered aniline can be reduced by decreasing the paraformaldehyde content in 50% formaldehyde and the hydrochloric acid ratio). The recovered aniline and fresh aniline are mixed and reacted with 33% hydrochloric acid to form a salt, with a hydrochloric acid / aniline molar ratio of 0.1. Then, a pre-condensation reaction is carried out with 50% formaldehyde (paraformaldehyde content 1 ppm) at 60°C for 100 min, with a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 110°C and a pH of 12. After neutralization, the polyamine is further washed with water. Following washing, the polyamine undergoes vacuum distillation (polyamine feed temperature 190°C, distillation column pressure controlled at 8 kPaA) to obtain the DAM product. The recovered aniline is separated at the top of the column and returned to the reaction unit. Under these conditions, the blockage content in the reaction solution is 80 ppm, and the N-methylaniline in the DAM product is about 0.34%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 30# is obtained.

[0037] Example 1

[0038] like Figure 2 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 30 ppm total ketones. Purified and recovered aniline is mixed with fresh aniline and reacted with 33% hydrochloric acid to form a salt, with a hydrochloric acid / aniline molar ratio of 0.3. Then, it undergoes a pre-condensation reaction with 30% formaldehyde at 60°C for 100 min, with a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 110°C and pH 12. After neutralization, the polyamine is further washed with water. The washed polyamine is then subjected to vacuum distillation to obtain DAM product. Recovered aniline is separated at the top of the distillation column. The recovered aniline is then subjected to distillation (column pressure 20 kPaA, top temperature controlled at 60°C, top reflux ratio 1, top light component collection ratio 0.03) to remove paraformaldehyde, resulting in purified recovered aniline with 100 ppm paraformaldehyde. This purified aniline is returned to the reaction unit for further reaction. Under these conditions, the blockage content in the reaction solution is 50 ppm, and the N-methylaniline in the DAM product is about 0.2%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 20# is obtained.

[0039] Example 2

[0040] likeFigure 2 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 50 ppm total ketones. Purified and recovered aniline is mixed with fresh aniline and reacted with 33% hydrochloric acid to form a salt, with a hydrochloric acid / aniline molar ratio of 0.3. Then, it undergoes a pre-condensation reaction with 30% formaldehyde at 60°C for 100 min, with a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 110°C and pH 12. After neutralization, the polyamine is further washed with water. The washed polyamine is then subjected to vacuum distillation to obtain DAM product. Recovered aniline is separated at the top of the distillation column. The recovered aniline is then subjected to distillation (column pressure 20 kPaA, top temperature controlled at 60°C, top reflux ratio 1, top light component collection ratio 0.04) to remove paraformaldehyde, resulting in purified recovered aniline with 1 ppm paraformaldehyde. This purified aniline is returned to the reaction unit for further reaction. Under these conditions, the blockage content in the reaction solution is 9 ppm, and the N-methylaniline in the DAM product is about 0.09%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 20# is obtained.

[0041] Example 3

[0042] like Figure 2 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 50 ppm total ketones. Purified and recovered aniline is mixed with fresh aniline and reacted with 33% hydrochloric acid to form a salt, with a hydrochloric acid / aniline molar ratio of 0.3. Then, it undergoes a pre-condensation reaction with 30% formaldehyde at 60°C for 100 min, with a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 110°C and pH 8. After neutralization, the polyamine is further washed with water. The washed polyamine is then distilled under reduced pressure to obtain DAM product. Recovered aniline is separated at the top of the distillation column. The recovered aniline is then distilled again (column pressure 20 kPaA, top temperature controlled at 60°C, top reflux ratio 1, top light component collection ratio 0.04) to remove paraformaldehyde, resulting in purified recovered aniline with 1 ppm paraformaldehyde. This purified aniline is then returned to the reaction unit for further reaction. Under these conditions, the blockage content in the reaction solution is 9 ppm, and the N-methylaniline in the DAM product is about 0.09%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 15# is obtained.

[0043] Example 4

[0044] likeFigure 2 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 50 ppm total ketones. After purification and recovery, aniline is mixed with fresh aniline and reacted with 33% hydrochloric acid to form a salt. The molar ratio of hydrochloric acid to aniline is 0.3. Then, it undergoes a pre-condensation reaction with 30% formaldehyde at 60°C for 100 min, with a molar ratio of formaldehyde to aniline of 0.4. The temperature is then raised to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 90°C and pH 10. After neutralization, the polyamine is further washed with water. After washing, the polyamine is distilled under reduced pressure to obtain DAM product. The recovered aniline is separated at the top of the column and then distilled to remove paraformaldehyde. The purified recovered aniline contains 50 ppm paraformaldehyde and is returned to the reaction unit for reprocessing. Under these conditions, the blockage content in the reaction solution is 20 ppm, and the N-methylaniline in the DAM product is about 0.09%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 15# is obtained.

[0045] Example 5

[0046] like Figure 2 The process flow for preparing diamines and polyamines is shown below. Fresh aniline contains 60 ppm of total ketones. Purified and recovered aniline is mixed with fresh aniline and reacted with 33% hydrochloric acid to form a salt, with a hydrochloric acid / aniline molar ratio of 0.3. Then, it undergoes a pre-condensation reaction with 30% formaldehyde at 60°C for 100 min, with a formaldehyde / aniline molar ratio of 0.4. The mixture is then heated to 100°C for a transposition reaction for 3 h. The reaction solution is neutralized with 50% caustic soda at 60°C and pH 8. After neutralization, the polyamine is further washed with water. The washed polyamine is then subjected to vacuum distillation to obtain DAM product. Recovered aniline is separated at the top of the distillation column. The recovered aniline is then subjected to distillation (column pressure 20 kPaA, top temperature controlled at 60°C, top reflux ratio 1, top light component collection ratio 0.04) to remove paraformaldehyde, resulting in purified recovered aniline with 1 ppm paraformaldehyde. This purified aniline is returned to the reaction unit for further reaction. Under these conditions, the blockage content in the reaction solution is 9 ppm, and the N-methylaniline in the DAM product is about 0.09%. The purified DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution. Then, the mixed solution and phosgene are subjected to a two-stage phosgenation reaction at 90℃ and 145℃ at a mass ratio of 5:4 at 300 kPag. After removing chlorobenzene, MDI color number 10# is obtained.

[0047] Example 6

[0048] likeFigure 2 The preparation process of the diamine and polyamine shown. The total ketone content in fresh aniline is 100 ppm, the purified recovered aniline is mixed with 33% hydrochloric acid for salification reaction, the molar ratio of hydrochloric acid / aniline is 0.3, then pre-condensation reaction is carried out with 30% formaldehyde at 60°C for 100 min, the molar ratio of formaldehyde / aniline is 0.4, and the temperature is raised to 100°C for transposition reaction for 3 h. The reaction solution is treated by neutralization with 50% caustic soda, the neutralization temperature is 60°C, and the neutralization pH is 8. After neutralization, the polyamine is further treated by water washing. After water washing, the polyamine is subjected to reduced pressure distillation to obtain DAM product. The recovered aniline is separated at the top of the column, and after distillation treatment (column pressure 20 KpaA, top column temperature control 60°C, top column reflux ratio 1, and top column light component collection ratio 0.05), the recovered aniline is obtained, and after removal of the trimer formaldehyde, the trimer formaldehyde in the purified recovered aniline is 0.1 ppm, which is returned to the reaction unit for re-reaction. Under the above conditions, the content of the blocking material in the reaction solution is 9 ppm, and the N-methyl aniline in the DAM product is about 0.05%. The refined DAM and chlorobenzene are mixed in a dynamic mixer at a mass ratio of 1:4 to form a mixed solution, and then the mixed solution and phosgene are sequentially subjected to two-stage phosgenation reaction at 300 kpag at 90°C and 145°C at a mass ratio of 5:4, and after removal of chlorobenzene, MDI with color number 10# is obtained.

[0049] The diamines and polyamines of the diphenylmethane series prepared by the preparation methods provided in Examples 1-6 and Comparative Examples 1-2 are run, and the results of the blocking material and product quality are shown in Table 1.

[0050] Table 1

[0051]

[0052] As can be seen from Examples 1-6 in Table 1, by removing the trimer formaldehyde in the recovered aniline and adjusting the neutralization process parameters, the amount of blocking material generated during the reaction is significantly reduced, the key by-product N-methyl aniline is also significantly reduced, the color number of the prepared MDI product is significantly improved, and the total ketone content in the raw material aniline can be relaxed, so that the energy consumption of the aniline production process is greatly reduced.

[0053] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto. It should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A process for the production of diphenylmethane series diamines and polyamines, which diphenylmethane series diamines and polyamines are produced by reacting formaldehyde and aniline in the presence of an acid catalyst, characterized in that, The aniline comprises fresh aniline and recycled aniline, and the content of trioxymethylene in the recycled aniline is ≤100 ppm, preferably ≤1 ppm, and more preferably 0.1-1 ppm.

2. The method of claim 1, wherein, The preparation method comprises the following steps: S1: fresh aniline and recycled aniline are mixed to serve as raw aniline, and the raw aniline is reacted with an acidic catalyst to obtain aniline acid salt; S2: formaldehyde aqueous solution and the aniline acid salt of step S1 are mixed to sequentially perform condensation reaction and transposition reaction to obtain a polyamine reaction liquid; S3: the polyamine reaction liquid obtained in step S2 is sequentially subjected to neutralization treatment and water washing treatment to obtain a water-washed polyamine liquid; S4: the water-washed polyamine liquid obtained in step S3 is subjected to vacuum rectification to obtain product DAM, and the overhead gas phase is cooled to obtain an aniline and water organic phase, and the recycled aniline and recycled water are obtained after phase separation. S5: the recycled aniline obtained in step S4 is subjected to rectification treatment to remove impurities in the recycled aniline, so that the content of trioxymethylene in the aniline is ≤100 ppm, preferably ≤1 ppm; the overhead gas phase is condensed and separated to obtain a waste organic phase and condensate water, and the recycled aniline after rectification is obtained from the column bottom and is sent to step S1 to be mixed with fresh aniline and then be subjected to reaction again.

3. The method of claim 1 or 2, wherein, The acidic catalyst comprises one or more of hydrochloric acid, sulfuric acid, phosphoric acid, preferably hydrochloric acid; H + with aniline in a molar ratio of (0.01-0.5):

1.

4. The method of claim 2 or 3, wherein, The mass fraction of the formaldehyde aqueous solution in step S2 is 20-55 wt%, preferably 30-50 wt%, and the content of trioxymethylene in the formaldehyde aqueous solution is ≤10 ppm.

5. The method of any one of claims 2-4, wherein, The molar ratio of formaldehyde molecules to aniline in the formaldehyde aqueous solution is (0.3-0.8):1; and / or, the condensation reaction temperature is 30-100℃, and the condensation reaction time is 10-100 min.

6. The method of any one of claims 2-5, wherein, The transposition reaction temperature is 80-150℃, and the transposition reaction time is 1-5 h.

7. The method of any one of claims 2-6, wherein, In step S3, sodium hydroxide is used for neutralization, and / or the neutralization temperature is 60-110℃, preferably 60-90℃, the neutralization PH is controlled to 8-12, preferably 9-10.

5.

8. The method of any one of claims 2-7, wherein, In step S4, the water-washed polyamine is subjected to vacuum rectification, the polyamine feed temperature is 100-250℃, preferably 150-200℃, and / or the rectification column pressure is controlled to 1-20 KpaA, preferably 5-10 KpaA.

9. The method of any one of claims 2-8, wherein, In step S5, the recycled aniline is subjected to rectification treatment, the rectification pressure is controlled to 1-101 KpaA, preferably 10-101 KpaA; and / or, the overhead temperature is controlled to 30-120℃, preferably 60-120℃.

10. The method of any one of claims 2-8, wherein, In step S5, the reflux ratio of the overhead is 0.1-3, preferably 0.1-1, and the proportion of the light components collected from the overhead is 0.03-0.1, preferably 0.03-0.06.

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