Process for the preparation of diamines and polyamines of the diphenylmethane series with improved 2,4-mda selectivity

Abstract

The application relates to the technical field of preparation of diamines and polyamines in a diphenylmethane series, and provides a preparation method of diamines and polyamines in a diphenylmethane series with improved 2,4-MDA selectivity; through the preparation method, the selectivity of 2,4-MDA can be improved. In the preparation method, formaldehyde and aniline are contacted and reacted in the presence of an acid catalyst to prepare the diamines and polyamines in the diphenylmethane series, and the acid catalyst is added into a reaction system in multiple steps based on the total amount of the acid catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diamines and polyamines of diphenylmethane series, in particular to a preparation method of diamines and polyamines of diphenylmethane series with improved 2,4-MDA selectivity BACKGROUND

[0002] Diamines and polyamines of diphenylmethane series (DAM) are understood to mean amines and mixtures of amines of the following type:

[0003]

[0004] Here, n denotes a natural number > 0, n = 0 is called diamino diphenylmethane, for short diamine; n > 0 is called polyamine-based polyphenylmethane, for short polyamine, and mixtures of the two types are called diamines and polyamines of diphenylmethane series. The derived products of the NH2 groups in DAM, which are all replaced by NCO groups, are diaminodiphenylmethane series diisocyanates, diaminodiphenylmethane series polyisocyanates or polyimino polyphenylene polymethylene polyisocyanates or diaminodiphenylmethane series diisocyanates and polyisocyanates (hereinafter referred to as MDI), which are used to produce polyurethanes.

[0005] In the art, the preparation methods of DAM are generally well known and described in many published patents and publications, such as US-A 2009 / 0240077, EP-A-451442 and WO-A-99 / 40059, DAM is prepared by continuous, semi-continuous or discontinuous reaction processes, usually using aniline and hydrochloric acid to generate aniline hydrochloride, and then adding formaldehyde in the reactor to generate DAM hydrochloride, through neutralization, water washing process and separation of organic and inorganic phases to obtain crude DAM, through refining process to obtain DAM, and then through phosgenation reaction to generate monomer or polymeric MDI.

[0006] In the traditional large-scale industrial production process, the preparation of high-selectivity 4,4-methylenedianiline (4,4-MDA) is the goal, such as JP 2012 131720A relates to a method for preparing methylenedianiline derivatives (MDA derivatives) in the presence of a zeolite catalyst with high yield and high selectivity for 4,4 MDA; JP 2013 095724A relates to a method for preparing aromatic polyamines in the presence of a zeolite catalyst with high yield, in which 4,4 MDA can be obtained with high selectivity; CN114829000A provides a method for heterogeneous synthesis of methylenedianiline, which involves a catalytic material that can achieve a high 4,4-MDA isomer molar ratio.

[0007] Since 2,4-MDA is the main component in the preparation of MDI-50, the proportion of its isomers in DAM directly affects the yield of MDI-50. However, existing technologies, such as the technical solutions disclosed in the aforementioned literature, cannot effectively prepare DAM with high selectivity of 2,4-MDA, nor can they control the content of 2,4-MDA isomers according to the needs of downstream products. Summary of the Invention

[0008] This invention provides a method for preparing diphenylmethane-based diamines and polyamines with improved 2,4-MDA selectivity. The preparation method of this invention can improve the selectivity of 2,4-MDA.

[0009] To achieve its objective, the present invention provides the following technical solution:

[0010] This invention provides a method for preparing diphenylmethane-based diamines and polyamines with improved selectivity for 2,4-MDA. The method involves reacting formaldehyde and aniline in the presence of an acid catalyst to prepare the diphenylmethane-based diamines and polyamines, wherein the acid catalyst is added to the reaction system in multiple steps based on the total amount of the acid catalyst.

[0011] This invention improves the process for preparing diphenylmethane series diamines and polyamines using formaldehyde, aniline, and an acid catalyst as the basic reaction raw materials. The inventors have discovered that in the process of preparing diphenylmethane series diamines and polyamines (DAM) by reacting formaldehyde and aniline in the presence of an acid catalyst, adding the acid catalyst in multiple steps to the reaction system can significantly improve the selectivity of 2,4-MDA compared to adding all the acid catalyst to the reaction system in one step.

[0012] In a preferred embodiment, based on the total amount of the acid catalyst, the acid catalyst is divided into a first part of the acid catalyst and a second part of the acid catalyst; the preparation method includes the following steps:

[0013] S1) Formaldehyde and aniline undergo a first-stage reaction in the presence of the first part of the acid catalyst; the first part of the acid catalyst is added to the reaction system in one step or in multiple steps;

[0014] S2) The reactants obtained in step S1) are subjected to a second-stage reaction in the presence of the second part of the acid catalyst; the second part of the acid catalyst is added to the reaction system in one step or in multiple steps;

[0015] S3) The reactants obtained in step S2) are subjected to a transposition rearrangement reaction to obtain reaction products containing diamines and polyamines of the diphenylmethane series;

[0016] S4) subjecting the reaction product obtained in step S3) to a neutralization reaction, followed by separation and purification, to obtain a diphenylmethane series diamine and polyamine product.

[0017] By using the above preferred mode, the formaldehyde, aniline and part of the acid catalyst are subjected to a first stage reaction in advance, and then the remaining acid catalyst is added to perform a second stage reaction, and then a transposition rearrangement reaction, which is beneficial to further improve the selectivity of 2,4-MDA. In the first stage reaction, the first part of the acid catalyst can be added in one step or in multiple steps, preferably in multiple steps, which is beneficial to further improve the selectivity of 2,4-MDA. The second part of the acid catalyst can also be added in one step or in multiple steps, preferably in multiple steps, which is beneficial to further improve the selectivity of 2,4-MDA. At the same time, the inventors have found that by adjusting the addition mode of the first part of the acid catalyst and / or the second part of the acid catalyst, such as using one-step addition or using multiple-step addition and adjusting the specific number of addition steps, different proportions of o- and p-aminobenzyl aniline acid salts can be generated in different stages, and then different proportions of 2,4-MDA isomers can be generated in the rearrangement process, which can realize the adjustment of the selectivity of 2,4-MDA, so as to easily and flexibly meet the specific needs of the content of 2,4-MDA in different DAM products, and realize the fine control of the product.

[0018] In the preferred embodiment, in step S1), the reaction temperature of the first stage reaction is 20-150°C, such as 20°C, 40°C, 50°C, 60°C, 80°C, 100°C, 120°C, 140°C, 150°C, etc.

[0019] In step S2), the reaction temperature of the second stage reaction is 20-180°C, such as 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 150°C, 170°C, 180°C, etc., preferably 35-95°C.

[0020] In step S3), the reaction temperature of the transposition rearrangement reaction is 55-200°C, such as 55°C, 80°C, 100°C, 103°C, 105°C, 120°C, 140°C, 150°C, 170°C, 180°C, 200°C, etc.

[0021] Moreover, the reaction temperature of the transposition rearrangement reaction is higher than the reaction temperature of the second stage reaction, and the reaction temperature of the second stage reaction is higher than the reaction temperature of the first stage reaction.

[0022] The inventors have found that by using the above reaction temperatures for steps S1)-S3) in the preparation method of the present application, and by making the reaction temperature of the transposition rearrangement reaction higher than the reaction temperature of the second stage reaction, and the reaction temperature of the second stage reaction higher than the reaction temperature of the first stage reaction, it is beneficial to further improve the selectivity of 2,4-MDA.

[0023] More preferably, in step S1), the reaction temperature of the first stage reaction is 35-95°C, preferably 50-95°C, more preferably 55-95°C, and the first stage reaction is carried out at the preferred reaction temperature, which is conducive to further significantly improving the selectivity of 2,4-MDA.

[0024] More preferably, in step S2), the reaction temperature of the second stage reaction is 35-95°C, which is conducive to further improving the selectivity of 2,4-MDA.

[0025] More preferably, in step S3), the reaction temperature of the transposition rearrangement reaction is preferably 70-150°C, more preferably 105-150°C, and the transposition rearrangement reaction is carried out at the preferred reaction temperature, which is conducive to further significantly improving the selectivity of 2,4-MDA.

[0026] The present inventors have found that by adjusting the reaction temperature of step S1), step S2) and / or step S3), the selectivity of 2,4-MDA can be adjusted, thereby facilitating flexible satisfaction of the specific requirements for the content of 2,4-MDA in different DAM products, and realizing fine control of the products.

[0027] In some embodiments, the reaction time of step S1) is 1.5-500 minutes, such as 1.5 minutes, 5 minutes, 20 minutes, 50 minutes, 100 minutes, 150 minutes, 300 minutes, 400 minutes, 500 minutes, etc., and is preferably 30-300 minutes. In some embodiments, the reaction time of step S2) is 1.5-500 minutes, such as 1.5 minutes, 5 minutes, 20 minutes, 50 minutes, 100 minutes, 150 minutes, 300 minutes, 400 minutes, 500 minutes, etc., and is preferably 5-300 minutes. In some embodiments, the reaction time of step S3) is 1-10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 7 hours, 8 hours, 10 hours, etc., and is preferably 2-5 hours.

[0028] In some embodiments, based on the total amount of the acid catalyst, the mass percentage of the first portion of the acid catalyst is 5% to 99%, for example, 5%, 8%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, etc., preferably 10% to 60%. Using the preferred percentage of the first portion of the acid catalyst is beneficial for obtaining higher 2,4-MDA selectivity. Furthermore, the preparation method of the present invention, by adjusting the addition ratio of the first portion of the acid catalyst, can change the proportion of o- and p-aminobenzylaniline salts generated at different stages, thereby producing different proportions of 2,4-MDA isomers during the rearrangement process. This enables the adjustment of 2,4-MDA selectivity, thus easily and flexibly meeting the specific requirements of 2,4-MDA content in different DAM products, achieving refined product control.

[0029] In some embodiments, in step S1), before the formaldehyde is added to the reaction system, the aniline is pre-reacted by contacting at least a portion of the first partial acid catalyst, and then the formaldehyde is added to continue the reaction. In this method, before the formaldehyde is added to the reaction system, the first partial acid catalyst can be added to the reaction system in one step or in multiple steps to react with the aniline; or, before the formaldehyde is added, a portion of the first partial acid catalyst can be added to the reaction system in one step or in multiple steps to react with the aniline, and the remaining first partial acid catalyst is added to the reaction system during or after the formaldehyde is added, and the addition method can also be one step or in multiple steps. Preferably, in this method, the reaction temperature after adding formaldehyde in step S1) is higher than the reaction temperature of the pre-reaction before adding formaldehyde. Preferably, the reaction temperature after adding formaldehyde is 30-150℃, such as 30℃, 40℃, 60℃, 80℃, 100℃, 120℃, 140℃, 150℃, etc., preferably 35-95℃, more preferably 55-95℃, and even more preferably 70-95℃. Using the preferred reaction temperature is beneficial to further improve the selectivity of 2,4-MDA.

[0030] Furthermore, in some preferred embodiments, in step S1), the reaction temperature after the addition of formaldehyde in the first stage reaction is controlled to be 35-95°C, preferably 55-95°C, more preferably 70-95°C; in step S2), the reaction temperature of the second stage reaction is controlled to be higher than that of the first stage reaction, preferably 35-95°C; in step S3), the reaction temperature of the transposition rearrangement reaction is controlled to be 70-150°C, preferably 105-150°C, and higher than that of the second stage reaction. This preferred approach facilitates obtaining further improved 2,4-MDA selectivity.

[0031] In some embodiments, in step S1), the aniline is contacted with at least part of the first portion of the acid catalyst initially added to the reaction system in the presence of formaldehyde. That is, the acid catalyst initially added to the reaction system is contacted with the aniline in the presence of formaldehyde. In step S1), the acid catalyst initially added to the reaction system can be part of or all of the first portion of the acid catalyst. In this embodiment, the first portion of the acid catalyst can be added to the reaction system in one step or in multiple steps.

[0032] Specifically, the step S1), the step S2) and / or the step S3) can be carried out in one or more reactors. For example, the step S1), the step S2) and / or the step S3) are carried out in the same reactor or transferred to different reactors. When multiple reactors are involved, the multiple reactors can be connected in series, and the number of reactors can be determined by the actual needs of the reaction.

[0033] Specifically, the reaction process of the step S1), the step S2) and the step S3) can be carried out in a batch mode or a continuous mode. When a continuous mode is used, there is continuous feeding and continuous discharging during the reaction.

[0034] Further, in step S4), the neutralization reaction is carried out by adding a lye, which is one or more of an alkali metal hydroxide solution and an alkaline earth metal hydroxide solution. The lye used in the neutralization reaction can be conventional in the art. Preferably, the lye is a sodium hydroxide solution and / or a potassium hydroxide solution, and specifically, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution. The mass concentration of the lye is preferably 20-55%, and more preferably 32-50%. When the acid catalyst is an organic acid and / or an inorganic acid, the lye is OH - When the acid catalyst is an organic acid and / or an inorganic acid, the lye is OH + The molar ratio of the lye to the acid catalyst is 1.0-3.0, and preferably 1.02-1.30. The neutralization reaction can be carried out in a neutralization reactor, preferably a stirred reactor.

[0035] Further, the separation and purification include: performing two-phase separation on the mixture obtained from the neutralization reaction to obtain a saline phase and an organic phase containing diphenylmethane-based diamines and polyamines; and then washing the organic phase with water and removing aniline to obtain the diphenylmethane-based diamines and polyamines. The two-phase separation can be carried out in a two-phase separator (preferably a static separator). Specifically, the saline phase can be extracted and stripped to obtain waste brine, which is then sent downstream for alkali production and chlorine production. This process can be carried out using conventional processes in the art, and will not be elaborated further. The aniline removal treatment of the organic phase can be carried out by vacuum distillation (which also removes water), yielding purified DAM products.

[0036] Further, the acid catalyst is selected from one or more of organic acids, inorganic acids, and solid acids, wherein the organic acid is, for example, one or more of methanesulfonic acid, ethanesulfonic acid, and benzylsulfonic acid, and the inorganic acid is, for example, one or more of hydrochloric acid, sulfuric acid, and phosphoric acid. The acid catalyst is preferably hydrochloric acid, more preferably 30-37 wt% hydrochloric acid; preferably, when the acid catalyst is an organic acid and / or an inorganic acid, the H+ of the acid catalyst is used as the concentration of the acid catalyst. + The molar ratio of all the acid catalysts and aniline used is 0.01 to 0.80, for example, 0.01, 0.05, 0.10, 0.30, 0.40, 0.60, 0.80, etc., more preferably 0.05 to 0.40. The solid acid can be a solid acid catalyst with catalytic activity, such as a molecular sieve, ion exchange resin, or natural clay mineral. Those skilled in the art can adjust the amount of solid acid catalyst used, as well as the amount of alkali solution required for the subsequent neutralization reaction, according to the type and form of the solid acid catalyst.

[0037] Further, the molar ratio of formaldehyde to aniline is 0.20–0.85, for example, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.85, etc., preferably 0.30–0.60. Preferably, the formaldehyde is added to the reaction system in the form of a formaldehyde solution, and the formaldehyde mass fraction of the formaldehyde solution is 15–55%, preferably 30–50%. Formaldehyde can be obtained, for example, by absorbing gaseous formaldehyde with an absorbent, such as pure water or salt water (salt water concentration, for example, 0.1–26 wt%), etc., to form a formaldehyde solution. The salt water is, for example, an aqueous solution of sodium salt, such as an aqueous solution of sodium sulfate or sodium chloride.

[0038] Furthermore, in the preparation method of the present invention, the formaldehyde is added to the reaction system in one step or in multiple steps. Preferably, the formaldehyde is added to the reaction system by one or more combinations of multi-point droplet addition, spraying, and direct current addition.

[0039] In the present disclosure, "direct current" refers to a flow-in mode of a material into a reaction system without intervention, i.e., a natural direct flow-in mode, as compared with a dropwise addition or a spray.

[0040] In the present disclosure, "more" in "more steps" or "more kinds" refers to two or more.

[0041] The technical solution provided by the present disclosure has the following beneficial effects:

[0042] Compared with a process of adding all acid catalysts to a reaction system in one step, the preparation method can significantly improve the selectivity and yield of 2,4-MDA.

[0043] The preparation method can easily adjust the generation ratio of o- and p-aminobenzylphenylamine acid salts at different reaction stages by adding acid catalysts in multiple steps, thereby producing different proportions of 2,4-MDA isomers in the rearrangement process, and meeting the proportioning requirements of MDI-50 and MDI-100 in downstream products, and easily realizing fine control of products. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the present disclosure, the present disclosure will be further described below in combination with examples. It should be understood that the following examples are only for better understanding of the present disclosure, and do not mean that the present disclosure is limited to the following examples.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The term "and / or" as can be used herein includes any and all combinations of one or more of the associated listed items. The terms "first", "second", etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance.

[0046] If the specific experimental steps or conditions are not specified in the examples, the operations or conditions can be performed according to the corresponding conventional experimental steps in the technical field. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0047] Aniline: 94wt%, Wanhua Chemical (Fujian) Co., Ltd. Industrial Park.

[0048] In the examples and comparative examples, a high-performance liquid chromatograph was used to analyze the isomers of refined DAM.

[0049] Example 1:

[0050] The preparation steps of DAM are as follows:

[0051] 1) To the reactor, aniline (200 g, 94wt%) and 33wt% concentration of hydrochloric acid (13.5 g, mass ratio in total amount of hydrochloric acid is 28.7%) were added, and the reaction was carried out at 50°C for 5 min under constant temperature condition;

[0052] 2) After the reaction was completed, formaldehyde aqueous solution (69 g, formaldehyde mass concentration is 37%) was added in a dropwise manner, the temperature was maintained at 65°C, and the reaction was carried out for 2 h;

[0053] 3) After the reaction was completed, 33wt% concentration of hydrochloric acid (33.5 g, mass ratio in total amount of hydrochloric acid is 71.3%) was added in a direct current injection manner, the temperature was maintained at 95°C, and the reaction was carried out for 1 h; then the temperature was continuously increased to 103°C, and the reaction was carried out for 1 h;

[0054] 4) After the reaction was completed, sodium hydroxide aqueous solution (40 g, concentration is 50wt%) was added, the reaction temperature was 90°C, and the neutralization reaction was carried out for 30 min under stirring;

[0055] 5) After the neutralization reaction was completed, the reaction liquid was transferred to a separatory funnel, the water phase and the organic phase were separated, the upper organic phase was washed with pure water, and the water and aniline were removed through a rectifying column to obtain refined DAM.

[0056] The isomers of the refined DAM were analyzed by using a high performance liquid chromatograph, and the results are shown in Table 1.

[0057] Example 2: (compared with Example 1, the addition proportion of hydrochloric acid in step 1) and step 3) is changed)

[0058] The preparation steps of DAM are as follows:

[0059] 1) To the reactor, aniline (200 g, 94wt%) and 33wt% concentration of hydrochloric acid (18.0 g, mass ratio in total amount of hydrochloric acid is 38.3%) were added, and the reaction was carried out at 50°C for 5 min under constant temperature condition;

[0060] 2) After the reaction was completed, formaldehyde aqueous solution (69 g, formaldehyde mass concentration is 37%) was added in a dropwise manner, the temperature was maintained at 65°C, and the reaction was carried out for 2 h;

[0061] 3) After the reaction was completed, 33wt% concentration of hydrochloric acid (29 g, mass ratio in total amount of hydrochloric acid is 61.7%) was added in a direct current injection manner, the temperature was maintained at 95°C, and the reaction was carried out for 1 h; then the temperature was continuously increased to 103°C, and the reaction was carried out for 1 h;

[0062] 4) After the reaction was completed, sodium hydroxide aqueous solution (40 g, concentration is 50wt%) was added, the reaction temperature was 90°C, and the neutralization reaction was carried out for 30 min under stirring;

[0063] 5) After the neutralization reaction is completed, the reaction solution is transferred to a separatory funnel to separate the water phase and the organic phase, the upper organic phase is washed with pure water, and the water and aniline are removed through a rectification tower to obtain refined DAM.

[0064] The isomers of the refined DAM obtained in Example 3 are analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0065] Example 3

[0066] Reference is made to Example 2, except that the reaction temperature of step 2) is increased to 85°C. The other preparation steps and conditions are consistent with Example 2.

[0067] The isomers of the refined DAM obtained in Example 3 are analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0068] Example 4:

[0069] Reference is made to Example 2, except that the reaction temperature of step 2) is increased to 85°C, and the temperature of step 3) for the rearrangement reaction is increased to 120°C. The other preparation steps and conditions are consistent with Example 2.

[0070] The isomers of the refined DAM obtained in Example 4 are analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0071] Example 5: (compared with Example 4, part of the hydrochloric acid in step 1) is added in step 2)

[0072] The preparation steps of DAM are as follows:

[0073] 1) Aniline (200 g, 94 wt%) and 33 wt% hydrochloric acid (9.0 g, the mass ratio in the total amount of hydrochloric acid is about 19.15%) are added to a reactor, and the reaction is carried out at 50°C for 5 min;

[0074] 2) After the reaction is completed, formaldehyde aqueous solution (69 g, the mass concentration of formaldehyde is 37%) is added by dropwise addition, and 33 wt% hydrochloric acid (9 g, the mass ratio in the total amount of hydrochloric acid is 19.15%) is added by direct injection, and the temperature is maintained at 85°C for 2 hours;

[0075] 3) After the reaction is completed, 33 wt% hydrochloric acid (29 g, the mass ratio in the total amount of hydrochloric acid is about 61.7%) is added by direct injection, and the temperature is maintained at 95°C for 1 hour; then the temperature is increased to 120°C, and the rearrangement reaction is carried out for 1 hour;

[0076] 4) After the reaction is completed, add sodium hydroxide aqueous solution (40 g, 50 wt% concentration), the reaction temperature is 90°C, and the neutralization reaction is stirred for 30 min;

[0077] 5) After the neutralization reaction is completed, transfer the reaction liquid to a separatory funnel, separate the water phase and the organic phase, take the upper organic phase, wash it with pure water, and remove water and aniline through a rectification tower to obtain refined DAM.

[0078] The isomers of the refined DAM are analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0079] Example 6

[0080] The preparation steps of DAM are as follows:

[0081] 1) Add aniline (200 g, 94 wt%) and 37 wt% hydrochloric acid (31.91 g, the mass ratio in the total amount of hydrochloric acid is 20%) into a reactor, and react for 5 min under the condition of constant temperature of 20°C;

[0082] 2) After the reaction is completed, add formaldehyde aqueous solution (76.82 g, the mass concentration of formaldehyde is 30%) in a dropwise manner, the temperature is maintained at 30°C, and the reaction is performed for 2 hours;

[0083] 3) After the reaction is completed, add 37 wt% hydrochloric acid (127.63 g, the mass ratio in the total amount of hydrochloric acid is 80%) in a direct current injection manner, the temperature is maintained at 95°C, and the reaction is performed for 1 hour; then continue to heat to 150°C, and perform a rearrangement reaction for 1 hour;

[0084] 4) After the reaction is completed, add sodium hydroxide aqueous solution (139.73 g, 50 wt% concentration), the reaction temperature is 90°C, and the neutralization reaction is stirred for 30 min;

[0085] 5) After the neutralization reaction is completed, transfer the reaction liquid to a separatory funnel, separate the water phase and the organic phase, take the upper organic phase, wash it with pure water, and remove water and aniline through a rectification tower to obtain refined DAM.

[0086] The isomers of the refined DAM are analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0087] Example 7

[0088] The preparation steps of DAM are as follows:

[0089] 1) Add aniline (200 g, 94 wt%) and 37 wt% hydrochloric acid (2.03 g, the mass ratio in the total amount of hydrochloric acid is 33.7%) into a reactor, and react for 5 min under the condition of constant temperature of 95°C;

[0090] 2) After the reaction was completed, formaldehyde aqueous solution (171.83 g, formaldehyde mass concentration of 30%) was added dropwise, the temperature was maintained at 120°C, and the reaction was carried out for 2 hours;

[0091] 3) After the reaction was completed, 37wt% concentrated hydrochloric acid (3.99 g, mass ratio in the total amount of hydrochloric acid was 66.3%) was added by direct injection, the temperature was maintained at 125°C, and the reaction was carried out for 1 hour; then the temperature was increased to 150°C, and the rearrangement reaction was carried out for 1 hour;

[0092] 4) After the reaction was completed, sodium hydroxide aqueous solution (5.27 g, concentration of 50wt%) was added, the reaction temperature was 90°C, and the neutralization reaction was carried out for 30 min under stirring;

[0093] 5) After the neutralization reaction was completed, the reaction liquid was transferred to a separatory funnel, the water phase and the organic phase were separated, the upper organic phase was washed with pure water, and the water and aniline were removed through a rectification tower to obtain refined DAM.

[0094] The isomers of the refined DAM were analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0095] Comparative Example 1:

[0096] Reference was made to Example 1, except that all the hydrochloric acid (a total of 47 g) was added in step 1), and the step of adding hydrochloric acid in step 3) was omitted. The remaining preparation steps and conditions were consistent with Example 1.

[0097] The isomers of the refined DAM obtained in Comparative Example 1 were analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0098] Comparative Example 2:

[0099] Reference was made to Example 3, except that all the hydrochloric acid (a total of 47 g) was added in step 1), and the step of adding hydrochloric acid in step 3) was omitted. The remaining preparation steps and conditions were consistent with Example 3.

[0100] The isomers of the refined DAM in Comparative Example 2 were analyzed by using a high-performance liquid chromatograph, and the results are shown in Table 1.

[0101] Table 1: Experimental results of examples and comparative examples

[0102]

[0103] In Table 1: The percentages are the mass percentages of 2,2-MDA, 2,4-MDA and 4,4-MDA in DAM, respectively.

[0104] From the comparison of Example 1 and Comparative Example 1, and Example 3 and Comparative Example 2, it can be seen that the addition of the acid catalyst in multiple stages can significantly improve the 2,4-MDA selectivity in the preparation of DAM.

[0105] From Examples 1-5, it can be seen that the method of the present application can be used to adjust the 2,4-MDA selectivity by changing the ratio of the addition of the acid catalyst in multiple stages, the number of times of the addition of the acid catalyst, and / or the adjustment of the reaction temperature, etc., so as to be able to flexibly adapt to different product requirements.

[0106] It is easily understood that the above examples are merely examples for the purpose of clear illustration, and are not meant to limit the present application. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and also impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing diphenylmethane-based diamines and polyamines with improved 2,4'-MDA selectivity, wherein formaldehyde and aniline are reacted in the presence of an acid catalyst to prepare the diphenylmethane-based diamines and polyamines, characterized in that, Based on the total amount of the acid catalyst, the acid catalyst is added to the reaction system in multiple steps; Based on the total amount of the acid catalyst used, the acid catalyst is divided into a first part of the acid catalyst and a second part of the acid catalyst. The preparation method includes the following steps: S1) Formaldehyde and aniline undergo a first-stage reaction in the presence of the first-part acid catalyst; the first-part acid catalyst is added to the reaction system in one step or in multiple steps; the reaction temperature of the first-stage reaction is 20~150℃; S2) The reactants obtained in step S1) are subjected to a second-stage reaction in the presence of the second part of the acid catalyst; the second part of the acid catalyst is added to the reaction system in one step or in multiple steps; the reaction temperature of the second-stage reaction is 20~180℃; S3) The reactants obtained in step S2) are subjected to a transposition rearrangement reaction to obtain reaction products containing diphenylmethane series diamines and polyamines; the reaction temperature of the transposition rearrangement reaction is 55~200℃; S4) The reaction product obtained in step S3) is neutralized, then separated and purified to obtain diphenylmethane series diamine and polyamine products; Furthermore, the reaction temperature of the transposition rearrangement reaction is higher than the reaction temperature of the second stage reaction, and the reaction temperature of the second stage reaction is higher than the reaction temperature of the first stage reaction.

2. The preparation method according to claim 1, characterized in that, In step S1), the reaction temperature of the first stage reaction is 35-95℃; In step S2), the reaction temperature of the second stage reaction is 35~95℃; In step S3), the reaction temperature of the transposition rearrangement reaction is 70~150℃.

3. The preparation method according to claim 2, characterized in that, In step S1), the reaction temperature of the first stage reaction is 55-95℃; In step S3), the reaction temperature of the transposition rearrangement reaction is 105-150℃.

4. The preparation method according to claim 1, characterized in that, The reaction time for step S1) is 1.5 to 500 minutes; And / or, the reaction time in step S2) is 1.5 to 500 minutes; And / or, the reaction time for step S3) is 1 to 10 hours.

5. The preparation method according to claim 4, characterized in that, The reaction time for step S1) is 30-300 minutes; And / or, the reaction time for step S2) is 5 to 300 minutes; And / or, the reaction time for step S3) is 2 to 5 hours.

6. The preparation method according to any one of claims 1-5, characterized in that, Based on the total amount of the acid catalyst used, the mass percentage of the first portion of the acid catalyst is 5-99%.

7. The preparation method according to claim 6, characterized in that, Based on the total amount of the acid catalyst used, the first portion of the acid catalyst accounts for 10-60% of the total mass.

8. The preparation method according to any one of claims 1-5, characterized in that, In step S1), before the formaldehyde is added to the reaction system, the aniline is pre-reacted by contacting at least a portion of the first portion of the acid catalyst, and then the formaldehyde is added to continue the reaction. Alternatively, in step S1), the aniline reacts with at least a portion of the first portion of the acid catalyst initially added to the reaction system in the presence of formaldehyde.

9. The preparation method according to claim 8, characterized in that, The reaction temperature after adding formaldehyde in step S1) is higher than the reaction temperature of the pre-reaction before adding formaldehyde.

10. The preparation method according to claim 9, characterized in that, In step S1), the reaction temperature after adding the formaldehyde is 30-150℃.

11. The preparation method according to claim 10, characterized in that, In step S1), the reaction temperature after adding the formaldehyde is 35-95℃.

12. The preparation method according to claim 11, characterized in that, In step S1), the reaction temperature after adding the formaldehyde is 70-95℃.

13. The preparation method according to any one of claims 1-5, characterized in that, Steps S1), S2), and / or S3) are carried out in one or more reactors; And / or, the reaction processes of steps S1), S2), and S3) are carried out in an intermittent or continuous manner.

14. The preparation method according to any one of claims 1-5, characterized in that, In step S4), the neutralization reaction is carried out by adding an alkaline solution, wherein the alkaline solution is one or more of an alkali metal hydroxide solution and an alkaline earth metal hydroxide solution; the mass concentration of the alkaline solution is 20-55%; when the acid catalyst is an organic acid and / or an inorganic acid, the alkaline solution is in the form of OH... - The acid catalyst is calculated to be H + The molar ratio of the alkaline solution to the acid catalyst is calculated to be 1.0 to 3.

0. And / or, the separation and purification includes: performing two-phase separation on the mixture obtained from the neutralization reaction to obtain a saline phase and an organic phase containing diphenylmethane series diamines and polyamines, and then washing the organic phase with water and removing aniline to obtain the diphenylmethane series diamine and polyamine products.

15. The preparation method according to claim 14, characterized in that, The alkaline solution is a sodium hydroxide solution and / or a potassium hydroxide solution; The mass concentration of the alkaline solution is 32-50%; When the acid catalyst is an organic acid and / or an inorganic acid, the alkaline solution is in the form of OH-. - The acid catalyst is calculated to be H + The molar ratio of the alkaline solution to the acid catalyst is 1.02 to 1.

30.

16. The preparation method according to any one of claims 1-5, characterized in that, The acid catalyst is selected from one or more of organic acids, inorganic acids, and solid acids.

17. The preparation method according to claim 16, characterized in that, The acid catalyst is hydrochloric acid; And / or, when the acid catalyst is an organic acid and / or an inorganic acid, the H+ of the acid catalyst is used. + The molar ratio of all the acid catalysts used to the aniline is calculated to be 0.01 to 0.

80. And / or, the solid acid is selected from one or more of molecular sieves, ion exchange resins, and natural clay minerals that have catalytic activity.

18. The preparation method according to claim 17, characterized in that, The acid catalyst is 30-37 wt% hydrochloric acid; And / or, when the acid catalyst is an organic acid and / or an inorganic acid, the H+ of the acid catalyst is used. + The molar ratio of all the acid catalysts used to the aniline is 0.05 to 0.

40.

19. The preparation method according to any one of claims 1-5, characterized in that, The molar ratio of formaldehyde to aniline is 0.20 to 0.85; the formaldehyde is added to the reaction system in the form of a formaldehyde solution, and the formaldehyde mass fraction of the formaldehyde solution is 15-55%.

20. The preparation method according to claim 19, characterized in that, The molar ratio of formaldehyde to aniline is 0.30 to 0.

60. And / or, the formaldehyde is added to the reaction system in the form of a formaldehyde solution, wherein the formaldehyde mass fraction of the formaldehyde solution is 30-50%.

21. The preparation method according to any one of claims 1-5, characterized in that, The formaldehyde is added to the reaction system in one step or in multiple steps.

22. The preparation method according to claim 21, characterized in that, The formaldehyde is added to the reaction system using one or more of the following methods: multi-point dripping, spraying, and direct current.

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