Preparation method for diamines and polyamines of diphenylmethane series that improve 2,4-MDA selectivity

Abstract

A preparation method for diamines and polyamines of the diphenylmethane series that improve 2,4-MDA selectivity. Formaldehyde and aniline come into contact and react in the presence of an acid catalyst to produce the diamines and polyamines of the diphenylmethane series, and based on the total amount of the acid catalyst, the acid catalyst is added to the reaction system in multiple steps.

Description

Preparation method of diphenylmethane series diamines and polyamines with improved 2,4-MDA selectivity Technical Field

[0001] The present invention relates to the technical field of preparation of diphenylmethane series diamines and polyamines, and in particular to a method for preparing diphenylmethane series diamines and polyamines with improved 2,4-MDA selectivity. Background Art

[0002] Diamines and polyamines of the diphenylmethane series (DAM) are understood as meaning amines and amine mixtures of the following types:

[0003] Here, n represents a natural number ≥ 0. When n = 0, it is called diaminodiphenylmethane, referred to as diamine; when n > 0, it is called polyaminopolyphenylmethane, referred to as polyamine. Mixtures of these two types are referred to as diphenylmethane series diamines and polyamines. The products derived from the replacement of all NH2 groups in DAM with NCO groups are diisocyanates of the diaminodiphenylmethane series, polyisocyanates of the diaminodiphenylmethane series, or polyiminopolyphenylenepolymethylene polyisocyanates, or diisocyanates and polyisocyanates of the diaminodiphenylmethane series (hereinafter referred to as MDI), which are used to produce polyurethane.

[0004] In the art, the preparation method of DAM is generally well known and described in many open patents and publications, such as US-A 2009 / 0240077, EP-A-451442, and WO-A-99 / 40059. DAM is prepared by a continuous, semi-continuous, or discontinuous reaction process. Typically, aniline is reacted with hydrochloric acid to form aniline hydrochloride, and then formaldehyde is added to a reactor to form DAM hydrochloride. Crude DAM is obtained through neutralization, water washing, and separation of the organic and inorganic phases. DAM is then purified and phosgenated to produce monomeric or polymeric MDI.

[0005] In conventional large-scale industrial production processes, the goal is to prepare 4,4-methylenedianiline (4,4-MDA) with high selectivity. For example, 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, wherein 4,4-MDA can be obtained with high selectivity; and CN 114829000A provides a method for the heterogeneous synthesis of methylenedianiline, which involves a catalytic material that can achieve a high molar ratio of 4,4-MDA isomers.

[0006] Since 2,4-MDA is the primary ingredient in the preparation of MDI-50, the proportion of its isomers in DAM directly affects MDI-50 production. However, existing technologies, such as those disclosed in the aforementioned literature, are unable to effectively produce DAM with high selectivity for 2,4-MDA, nor are they able to regulate the 2,4-MDA isomer content based on downstream product requirements.

[0007] Summary of the Invention

[0008] The present invention provides a method for preparing diphenylmethane series diamines and polyamines for improving the selectivity of 2,4-MDA. The preparation method of the present invention can improve the selectivity of 2,4-MDA.

[0009] To achieve its purpose, the present invention provides the following technical solutions:

[0010] The present invention provides a method for preparing diphenylmethane series diamines and polyamines with improved 2,4-MDA selectivity. Formaldehyde and aniline are subjected to a contact reaction in the presence of an acid catalyst to prepare the diphenylmethane series diamines and polyamines. The acid catalyst is added to the reaction system in multiple steps based on the total amount of the acid catalyst.

[0011] The present invention improves a process for preparing diphenylmethane series diamines and polyamines using formaldehyde, aniline and an acid catalyst as 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, the acid catalyst is added to the reaction system in multiple steps. Compared with a process in which the entire acid catalyst is added to the reaction system in one step, the selectivity of 2,4-MDA can be significantly improved.

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

[0013] S1) formaldehyde and aniline are reacted in the first stage in the presence of the first portion of the acid catalyst; the first portion of the acid catalyst is added to the reaction system in a single step or in multiple steps;

[0014] S2) subjecting the reaction material obtained in step S1) to a second-stage reaction in the presence of the second portion of the acid catalyst; the second portion of the acid catalyst is added to the reaction system in a single step or in multiple steps;

[0015] S3) performing a transposition rearrangement reaction on the reaction material obtained in step S2) to obtain a reaction product of a diamine and a polyamine containing a diphenylmethane series;

[0016] S4) neutralizing the reaction product obtained in step S3), and then separating and refining it to obtain diphenylmethane series diamine and polyamine products.

[0017] Using the above preferred method, formaldehyde, aniline, and part of the acid catalyst are pre-processed into a first-stage reaction, and then the remaining acid catalyst is added to carry out a second-stage reaction, and then a transposition rearrangement reaction is carried out, which is conducive to further improving the selectivity of 2,4-MDA. Among them, 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 conducive to further improving 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 conducive to further improving the selectivity of 2,4-MDA. At the same time, the inventors have discovered that by adjusting the addition method of the first part of the acid catalyst and / or the second part of the acid catalyst, for example, using a single-step addition or using a multi-step addition and adjusting the specific number of additions, it is possible to change the generation of different proportions of o- and p-aminobenzylaniline salts at different stages, and then generate different proportions of 2,4-MDA isomers during the rearrangement process, which can achieve the adjustment of 2,4-MDA selectivity, thereby easily and flexibly meeting the specific requirements of 2,4-MDA content in different DAM products and achieving refined product control.

[0018] In a preferred embodiment, in step S1), the reaction temperature of the first stage reaction is 20-150°C, for example, 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, for example, 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 to 200°C, for example, 55°C, 80°C, 100°C, 103°C, 105°C, 120°C, 140°C, 150°C, 170°C, 180°C, 200°C, etc.;

[0021] 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.

[0022] The inventors have found that in the preparation method of the present invention, the above-mentioned reaction temperature is used to carry out steps S1) to S3), and the reaction temperature of the transposition rearrangement reaction is higher than the reaction temperature of the second stage, and the reaction temperature of the second stage is higher than the reaction temperature of the first stage reaction, which is conducive to further improving 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. Using the preferred reaction temperature for the first stage reaction is beneficial to further significantly improve 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. The use of the preferred reaction temperature for the transposition rearrangement reaction is conducive to further significantly improving the selectivity of 2,4-MDA.

[0026] The present inventors have discovered 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 flexibly meeting the specific requirements of 2,4-MDA content in different DAM products and achieving refined product control.

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

[0028] In some embodiments, the weight percentage of the first portion of the acid catalyst, based on the total amount of the acid catalyst, is 5-99%, for example, 5%, 8%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99%, etc., preferably 10-60%. The preferred weight percentage of the first portion of the acid catalyst facilitates achieving higher 2,4-MDA selectivity. Furthermore, by adjusting the addition ratio of the first portion of the acid catalyst, the preparation method of the present invention can adjust the production of different ratios of o- and p-aminobenzylaniline salts at different stages, thereby producing different ratios of 2,4-MDA isomers during the rearrangement process. This allows for adjustment of 2,4-MDA selectivity, making it easy to flexibly meet the specific requirements for 2,4-MDA content in different DAM products and achieve refined product control.

[0029] In some embodiments, in step S1), before the formaldehyde is added to the reaction system, the aniline is contacted with at least a portion of the first portion of the acid catalyst for a pre-reaction, and then the formaldehyde is added to continue the reaction. In this method, the first portion of the acid catalyst can be added to the reaction system in one step or in multiple steps to contact and react with the aniline before the formaldehyde is added to the reaction system; alternatively, before the formaldehyde is added, a portion of the first portion of the acid catalyst can be added in one step or in multiple steps to contact and react with the aniline, and the remaining first portion of the acid catalyst can be added to the reaction system during or after the addition of the formaldehyde, and the addition method can also be one step or multiple steps. Preferably, in this method, the reaction temperature after adding the formaldehyde in step S1) is higher than the reaction temperature of the pre-reaction before adding the formaldehyde. Preferably, the reaction temperature after adding the formaldehyde is 30-150°C, for example, 30°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 150°C, etc., preferably 35-95°C, further preferably 55-95°C, more preferably 70-95°C. 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, and more preferably 70-95°C; in step S2), the reaction temperature of the second-stage reaction is controlled to be higher than the reaction temperature of the first-stage reaction, preferably 35-95°C; and in step S3), the reaction temperature of the metathesis rearrangement reaction is controlled to be 70-150°C, preferably 105-150°C, and higher than the reaction temperature of the second-stage reaction. This preferred embodiment facilitates further improved 2,4-MDA selectivity.

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

[0032] Specifically, step S1), step S2), and / or step S3) can be performed in one or more reactors. For example, step S1), step S2), and / or step S3) can be performed in the same reactor or transferred to different reactors. When multiple reactors are involved, the multiple reactors can be connected in series. Those skilled in the art can reasonably select and determine the specific number of reactors required based on the actual reaction requirements.

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

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

[0035] Furthermore, the separation and purification comprises: subjecting the mixed liquid obtained by the neutralization reaction to two-phase separation to obtain a salty water phase and an organic phase containing diamines and polyamines of the diphenylmethane series, and washing the organic phase with water and removing aniline to obtain the diamines and polyamines products of the diphenylmethane series. The two-phase separation can be carried out in a two-phase separator (preferably a static stratifier). Specifically, the salty water phase can be extracted and stripped to obtain waste brine, which is then sent to downstream electrolysis for alkali production and chlorine production. This treatment process can be carried out using the corresponding conventional processes in the art, which will not be described in detail. The organic phase can be subjected to aniline removal treatment by vacuum distillation (which also removes water), and a refined DAM product is obtained by vacuum distillation.

[0036] Furthermore, the acid catalyst is selected from one or more of an organic acid, an inorganic acid, and a solid acid, wherein the organic acid is, for example, one or more of methanesulfonic acid, ethanesulfonic acid, and benzenesulfonic 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 + The molar ratio of the total acid catalyst to the aniline 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 catalytic solid acid catalyst such as a molecular sieve, an ion exchange resin, or a natural clay mineral. Those skilled in the art can adjust the amount of the 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] Furthermore, the molar ratio of the amount of formaldehyde to the amount of aniline is 0.20 to 0.85, for example, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.85, etc., preferably 0.30 to 0.60. Preferably, 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 15-55%, preferably 30-50%. For example, formaldehyde can be obtained by absorbing gaseous formaldehyde with an absorbent. For example, gaseous formaldehyde is absorbed into a formaldehyde solution using pure water, brine (with a brine concentration of, for example, 0.1-26 wt%), etc. as an absorbent. The brine is, for example, a sodium salt aqueous solution, specifically 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 a single step or multiple steps. Preferably, the formaldehyde is added to the reaction system in a combination of multi-point dropwise addition, injection, and direct flow.

[0039] In this article, "direct current" means that compared with methods such as dripping and spraying, the inflow method of materials is not interfered with and they enter the reaction system through natural direct flow.

[0040] As used herein, the term "multiple" in "multiple steps" or "multiple types" means two or more.

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

[0042] Compared with a process in which all the acid catalyst is added to the reaction system in one step, the preparation method of the present invention can significantly improve the selectivity and yield of 2,4-MDA.

[0043] The preparation method of the present invention, through multi-step addition of an acid catalyst, can easily and flexibly adjust the generation ratio of o- and p-aminobenzylaniline salts at different reaction stages, thereby generating 2,4-MDA isomers in different ratios during the rearrangement process. This can flexibly meet the proportion requirements of MDI-50 and MDI-100 in downstream products, and easily achieve refined product control. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention 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 skilled in the art to which this invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items. The terms "first," "second," etc., are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

[0046] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

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

[0048] In the Examples and Comparative Examples, the isomers of the purified DAM were analyzed using high performance liquid chromatography.

[0049] Example 1:

[0050] The steps for preparing DAM are as follows:

[0051] 1) Aniline (200 g, 94 wt%) and 33 wt% hydrochloric acid (13.5 g, accounting for 28.7% of the total amount of hydrochloric acid) were added to a reactor and reacted at a constant temperature of 50° C. for 5 min;

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

[0053] 3) After the reaction is completed, 33 wt % hydrochloric acid (33.5 g, accounting for 71.3% of the total amount of hydrochloric acid used) is added by direct current injection, the temperature is maintained at 95° C., and the reaction is carried out for 1 hour; then the temperature is further increased to 103° C. and the rearrangement reaction is carried out for 1 hour;

[0054] 4) After the reaction is completed, add sodium hydroxide aqueous solution (40 g, concentration is 50 wt%), the reaction temperature is 90 ° C, and stir to react for 30 minutes;

[0055] 5) After the neutralization reaction is completed, the reaction solution is transferred to a separatory funnel to separate the aqueous phase and the organic phase. The upper organic phase is washed with pure water and passed through a distillation tower to remove water and aniline to obtain refined DAM.

[0056] The isomers of purified DAM were analyzed by high performance liquid chromatography, and the results are shown in Table 1.

[0057] Example 2: (Compared with Example 1, the ratio of hydrochloric acid added in step 1) and step 3) was changed)

[0058] The steps for preparing DAM are as follows:

[0059] 1) Aniline (200 g, 94 wt%) and 33 wt% hydrochloric acid (18.0 g, accounting for 38.3% of the total amount of hydrochloric acid) were added to a reactor and reacted at a constant temperature of 50° C. for 5 min;

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

[0061] 3) After the reaction is completed, 33 wt% hydrochloric acid (29 g, accounting for 61.7% of the total amount of hydrochloric acid used) is added by direct current injection, the temperature is maintained at 95°C, and the reaction is carried out for 1 hour; then the temperature is further increased to 103°C, and the transposition rearrangement reaction is carried out for 1 hour;

[0062] 4) After the reaction is completed, add sodium hydroxide aqueous solution (40 g, concentration is 50 wt%), the reaction temperature is 90 ° C, and stir to react for 30 minutes;

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

[0064] The isomers of purified DAM were analyzed by high performance liquid chromatography, and the results are shown in Table 1.

[0065] Example 3

[0066] The same method as in Example 2 was used, except that the reaction temperature in step 2) was increased to 85° C. The other preparation steps and conditions were the same as in Example 2.

[0067] The isomers of the purified DAM obtained in Example 3 were analyzed using high performance liquid chromatography. The results are shown in Table 1.

[0068] Example 4:

[0069] The process was carried out in accordance with Example 2, except that the reaction temperature in step 2) was increased to 85° C., and the temperature for the transposition rearrangement reaction in step 3) was increased to 120° C. The other preparation steps and conditions were the same as those in Example 2.

[0070] The isomers of the purified DAM obtained in Example 4 were analyzed using high performance liquid chromatography. The results are shown in Table 1.

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

[0072] The steps for preparing DAM are as follows:

[0073] 1) Aniline (200 g, 94 wt%) and 33 wt% hydrochloric acid (9.0 g, accounting for approximately 19.15% of the total amount of hydrochloric acid) were added to a reactor and reacted at a constant temperature of 50° C. for 5 min;

[0074] 2) After the reaction was completed, a formaldehyde solution (69 g, 37% formaldehyde concentration) was added dropwise, and 33 wt % hydrochloric acid (9 g, 19.15% by mass of the total amount of hydrochloric acid used) was added by direct current injection. The temperature was maintained at 85° C. and the reaction was allowed to proceed for 2 hours.

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

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

[0077] 5) After the neutralization reaction is completed, the reaction solution is transferred to a separatory funnel to separate the aqueous phase and the organic phase. The upper organic phase is washed with pure water and passed through a distillation tower to remove water and aniline to obtain refined DAM.

[0078] The isomers of purified DAM were analyzed by high performance liquid chromatography, and the results are shown in Table 1.

[0079] Example 6

[0080] The steps for preparing DAM are as follows:

[0081] 1) Add aniline (200 g, 94 wt%) and 37 wt% hydrochloric acid (31.91 g, 20% by mass of the total amount of hydrochloric acid) to a reactor and react at a constant temperature of 20° C. for 5 min;

[0082] 2) After the reaction was completed, a formaldehyde aqueous solution (76.82 g, formaldehyde concentration of 30%) was added dropwise, the temperature was maintained at 30° C., and the reaction was carried out for 2 hours;

[0083] 3) After the reaction is completed, 37 wt% hydrochloric acid (127.63 g, accounting for 80% by mass of the total amount of hydrochloric acid used) is added by direct current injection, the temperature is maintained at 95°C, and the reaction is carried out for 1 hour; then the temperature is further increased to 150°C, and the transposition rearrangement reaction is carried out for 1 hour;

[0084] 4) After the reaction was completed, sodium hydroxide aqueous solution (139.73 g, concentration 50 wt%) was added at 90°C and stirred for 30 minutes;

[0085] 5) After the neutralization reaction is completed, the reaction solution is transferred to a separatory funnel to separate the aqueous phase and the organic phase. The upper organic phase is washed with pure water and passed through a distillation tower to remove water and aniline to obtain refined DAM.

[0086] The isomers of purified DAM were analyzed by high performance liquid chromatography, and the results are shown in Table 1.

[0087] Example 7

[0088] The steps for preparing DAM are as follows:

[0089] 1) Aniline (200 g, 94 wt%) and 37 wt% hydrochloric acid (2.03 g, accounting for 33.7% of the total amount of hydrochloric acid) were added to a reactor and reacted at 95° C. for 5 min.

[0090] 2) After the reaction was completed, a formaldehyde aqueous solution (171.83 g, formaldehyde 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 is completed, 37 wt% hydrochloric acid (3.99 g, accounting for 66.3% of the total amount of hydrochloric acid used) is added by direct current injection, the temperature is maintained at 125°C, and the reaction is carried out for 1 hour; then the temperature is further increased to 150°C, and the transposition rearrangement reaction is carried out for 1 hour;

[0092] 4) After the reaction was completed, sodium hydroxide aqueous solution (5.27 g, concentration 50 wt%) was added at 90°C and stirred for 30 minutes;

[0093] 5) After the neutralization reaction is completed, the reaction solution is transferred to a separatory funnel to separate the aqueous phase and the organic phase. The upper organic phase is washed with pure water and passed through a distillation tower to remove water and aniline to obtain refined DAM.

[0094] The isomers of purified DAM were analyzed by high performance liquid chromatography, and the results are shown in Table 1.

[0095] Comparative Example 1:

[0096] The same preparation steps and conditions as in Example 1 were followed, except that all hydrochloric acid (47 g in total) was added in step 1) and the addition of hydrochloric acid was omitted in step 3).

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

[0098] Comparative Example 2:

[0099] The same preparation steps and conditions as in Example 3 were followed, except that all hydrochloric acid (47 g in total) was added in step 1), and the addition of hydrochloric acid was omitted in step 3).

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

[0101] Table 1 Experimental results of the embodiments and comparative examples

[0102] In Table 1, the percentages are the mass percentages of 2,2-MDA, 2,4-MDA and 4,4-MDA in DAM.

[0103] From the comparison between Example 1 and Comparative Example 1, and between Example 3 and Comparative Example 2, it can be seen that adding the acid catalyst in multiple stages can significantly improve the selectivity of 2,4-MDA in the process of preparing DAM.

[0104] As can be seen from Examples 1-5, the method of the present invention can adjust the selectivity of 2,4-MDA by changing the addition ratio of the acid catalyst in multiple stages, changing the number of acid catalyst additions and / or adjusting the reaction temperature, thereby flexibly adapting to different product requirements.

[0105] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing diphenylmethane series diamines and polyamines with improved 2,4-MDA selectivity, wherein formaldehyde and aniline are contacted and reacted in the presence of an acid catalyst to prepare the diphenylmethane series 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.

2. The preparation method according to claim 1, characterized in that: Based on the total amount of the acid catalyst, the acid catalyst is divided into a first part of acid catalyst and a second part of acid catalyst; The preparation method comprises the following steps: S1) formaldehyde and aniline are reacted in the first stage 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; S2) carrying out a second stage reaction on the reaction material obtained in step S1) in the presence of the second portion of the acid catalyst; the second portion of the acid catalyst is added to the reaction system in one step or in multiple steps; S3) performing a transposition rearrangement reaction on the reaction material obtained in step S2) to obtain a reaction product containing diamines and polyamines of the diphenylmethane series; S4) neutralizing the reaction product obtained in step S3), and then separating and refining it to obtain diphenylmethane series diamine and polyamine products.

3. The preparation method according to claim 2, characterized in that: In step S1), the reaction temperature of the first stage reaction is 20-150°C, preferably 35-95°C, more preferably 55-95°C; In step S2), the reaction temperature of the second stage reaction is 20 to 180°C, preferably 35 to 95°C; In step S3), the reaction temperature of the transposition rearrangement reaction is 55-200°C, preferably 70-150°C, more preferably 105-150°C; 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.

4. The preparation method according to claim 3, characterized in that: The reaction time of step S1) is 1.5 to 500 minutes, preferably 30 to 300 minutes; And / or, the reaction time of step S2) is 1.5 to 500 minutes; preferably 5 to 300 minutes; And / or, the reaction time of step S3) is 1 to 10 hours; preferably 2 to 5 hours.

5. The preparation method according to any one of claims 2 to 4, characterized in that: Based on the total amount of the acid catalyst, the mass proportion of the first part of the acid catalyst is 5-99%, preferably 10-60%.

6. The preparation method according to any one of claims 2 to 5, characterized in that: In step S1), before the formaldehyde is added to the reaction system, the aniline is contacted with at least part of the first acid catalyst for pre-reaction, and then the formaldehyde is added to continue the reaction; preferably, the reaction temperature after the formaldehyde is added in step S1) is higher than the reaction temperature of the pre-reaction before the formaldehyde is added, and preferably the reaction temperature after the formaldehyde is added is 30-150°C, more preferably 35-95°C, and more preferably 70-95°C; Alternatively, in step S1), the aniline is contacted and reacted with at least a portion of the first acid catalyst initially added to the reaction system in the presence of formaldehyde.

7. The preparation method according to any one of claims 2 to 6, characterized in that: The steps S1), S2) and / or S3) are carried out in one or more reactors; And / or, the reaction process of step S1), step S2) and step S3) is carried out in an intermittent manner or a continuous manner.

8. The preparation method according to any one of claims 2 to 7, characterized in that: In step S4), the neutralization reaction is carried out by adding an alkali solution, wherein the alkali solution is one or more of an alkali metal hydroxide solution and an alkaline earth metal hydroxide solution, preferably a sodium hydroxide solution and / or a potassium hydroxide solution; the mass concentration of the alkali solution is preferably 20-55%, more preferably 32-50%; when the acid catalyst is an organic acid and / or an inorganic acid, the alkali solution is OH - The acid catalyst is based on H + The molar ratio of the alkali solution to the acid catalyst is 1.0 to 3.0, preferably 1.02 to 1.30; And / or, the separation and purification comprises: performing two-phase separation on the mixed liquid obtained by the neutralization reaction to obtain a salt water phase and an organic phase containing diphenylmethane series diamines and polyamines, washing the organic phase with water and removing aniline to obtain the diphenylmethane series diamines and polyamines. Amine products.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The acid catalyst is selected from one or more of an organic acid, an inorganic acid, and a solid acid, preferably hydrochloric acid, more preferably 30 to 37 wt % hydrochloric acid; Preferably, when the acid catalyst is an organic acid and / or an inorganic acid, the H + The molar ratio of all the acid catalysts to the aniline is 0.01 to 0.80, more preferably 0.05 to 0.40; Preferably, the solid acid is selected from one or more of molecular sieves, ion exchange resins, and natural clay minerals having catalytic effects.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The molar ratio of the formaldehyde to the aniline is 0.20-0.85, preferably 0.30-0.60; preferably, the formaldehyde is added to the reaction system in the form of formaldehyde solution, and the formaldehyde mass fraction of the formaldehyde solution is 15-55%, preferably 30-50%.

11. The preparation method according to any one of claims 1 to 10, characterized in that: The formaldehyde is added into the reaction system in a one-step or multi-step manner; Preferably, the formaldehyde is added to the reaction system by one or more combinations of multi-point dripping, spraying and direct flow.

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