Continuous synthesis method and equipment of diphenylmethane dicarbamate

Abstract

The invention relates to a continuous synthesis method and equipment for methyl diphenylmethane dicarbamate, which is characterized in that production and subsequent separation of methyl diphenylmethane dicarbamate are continuously operated on the basis of efficient microscale mixing characteristic, good mass transfer and heat transfer characteristics and accurate reaction regulation and control characteristics of a microreactor, so that the reaction efficiency is improved, and the production cost is reduced. Meanwhile, tedious separation steps are avoided, the separation efficiency is improved, and an oil phase product for pyrolysis is directly obtained. According to the multi-section continuous flow micro-reaction system disclosed by the invention, the methylenation reagent is added into the reaction system step by step, and the reaction temperature is controlled in blocks, so that the concentration of the local methylenation reagent is reduced, the side reaction is reduced, and the high-quality production of the product is realized. Based on the production process provided by the invention, 97% conversion of methyl phenylcarbamate can be realized in about 30 minutes, and the reaction selectivity of 4, 4 '-MDC is higher than 75% through subsequent separation and water washing.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical synthesis, and particularly relates to a method for continuously synthesizing diphenylmethane diaminomethyl ester in a microreactor. Background Art

[0002] MDI is an important raw material for the synthesis of polyurethane and is widely used in aerospace, shipbuilding, automobiles, construction, electronics, coatings, artificial leather, glass, shoes, fibers and other fields. It has isomers such as 2,4'-MDI, 2,2'-MDI, and 4,4'-MDI, among which 4,4'-MDI is the most widely used.

[0003] At present, the industrial production of MDI adopts the phosgene method, and its steps are as follows: aniline reacts with formaldehyde to generate diphenylmethanediamine (MDA), which then reacts with phosgene to obtain an MDI mixture, and finally separates it through distillation to obtain MDI monomer. Although this method has a simple synthesis process, mature technology, and is widely used, it has disadvantages such as highly toxic raw materials, difficult to remove residual chlorine in the product, and by-product hydrochloric acid corroding equipment and polluting the environment.

[0004] Methyl diphenylmethane dicarbamate (MDC) is an important intermediate for the non-phosgene synthesis of MDI, so the clean and efficient synthesis of MDC is of great significance. From the production process point of view, the synthesis of MDC is currently mainly synthesized by intermittent stirring tank process (for example, reference 1 and reference 2), that is, methyl phenylcarbamate is mixed with a formaldehyde solution containing an acid catalyst. In the whole production process, factors such as the ratio of formaldehyde and methyl phenylcarbamate, reactant concentration, reaction temperature and acid catalyst concentration have a great influence on the conversion rate of the product and the quality of the product, and the above-mentioned process reaction time is usually 2 to 6 hours, which is less efficient. Therefore, it is an inevitable trend to develop a highly efficient and controllable continuous synthesis process and equipment.

[0005] Reference 3 discloses a preparation device and method of diphenylmethane diamino formate, comprising dissolving phenylamino formate in a solvent to obtain an oil phase material, dissolving a methylene reagent in an inorganic acid solution to obtain an aqueous phase material, and subjecting the oil phase material and the aqueous phase material to preheating, emulsifying through a micromixer, and then conducting a condensation reaction. After the reaction is completed, the oil phase product is obtained by condensation and standing for stratification, and the obtained oil phase product is washed with water to obtain the diphenylmethane diamino formate. Although the method uses a micromixer to intensify the reaction, the reaction time is greatly shortened. However, the isomer of 4,4'-diphenylmethane diamino formate is not described, and the selectivity of the isomer is not mentioned. Moreover, the post-treatment process includes operations such as cooling the product, standing for stratification, washing with water, and phase separation, which is relatively complicated and time-consuming, and is not conducive to industrial application. In addition, the oil phase material and the aqueous phase material are also preheated by a preheater before entering the micromixer for mixing, and the preheating temperature is 150°C, which consumes a lot of energy.

[0006] References:

[0007] Reference 1: CN107434774B

[0008] Reference 2: CN117185962A

[0009] Reference 3: CN113926403A Summary of the invention

[0010] Problem that the invention aims to solve

[0011] In view of the problems existing in the prior art, such as low condensation reaction production efficiency, low target product selectivity, long reaction post-processing time, etc., the present invention first provides a continuous synthesis method of diphenylmethane dicarbamate. The method connects the synthesis process of a multi-stage continuous flow micro-reaction system and the separation process of a post-processing system in series, aiming to achieve efficient conversion and rapid separation from reaction raw materials to products.

[0012] Furthermore, the present invention also provides a device for implementing the method for synthesizing diphenylmethane diaminomethyl ester. The device has a simple structure and can ensure that the treatment method is carried out efficiently and orderly. The device has good pressure resistance and can achieve long-term stable operation.

[0013] Solutions for solving problems

[0014] The present invention finds that the above technical problems can be solved by the following technical solutions:

[0015] [1]. The present invention provides a continuous synthesis method of diphenylmethane diaminomethyl ester, which comprises the following steps:

[0016] a) delivering feed liquid A and feed liquid B to a micro mixer for mixing, and then entering microreactor No. 1 for reaction to obtain a first oil-water mixed liquid;

[0017] b) introducing the first oil-water mixture and feed liquid C1 into microreactor No. 2 and reacting to obtain a second oil-water mixture;

[0018] c) introducing the second oil-water mixture and feed liquid C2 into microreactor No. 3 and reacting to obtain a third oil-water mixture;

[0019] d) subjecting the third oil-water mixture to phase separation through a liquid-liquid membrane separator, and obtaining an oil phase;

[0020] e) post-treating the oil phase to obtain an oil phase product;

[0021] Wherein, the feed liquid C1 and the feed liquid C2 are both derived from the feed liquid C, the feed liquid A and the feed liquid C are aqueous solutions containing an inorganic acid catalyst and a methylene agent, and the feed liquid B is a methyl phenylcarbamate solution;

[0022] Furthermore, the molar ratio of the methyl phenylcarbamate to the methylene-forming agent is 2.5:1 or less.

[0023] [2] The synthesis method according to [1], wherein

[0024] The inorganic acid catalyst includes one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid;

[0025] The methylene agent includes any one of trioxymethylene, formaldehyde and dimethoxymethane.

[0026] [3] The synthesis method according to [1] or [2], wherein

[0027] The content of the inorganic acid catalyst in the feed liquid A is 15-40wt%, and the content of the methylene agent is 0.1-5wt%;

[0028] The content of methyl phenylcarbamate in liquid B is 1 to 12 wt %;

[0029] The content of the inorganic acid catalyst in the feed liquid C is 15-40wt%, and the content of the methylene-forming agent is 20-100% of the content of the methylene-forming agent in the feed liquid A.

[0030] [4] The synthesis method according to any one of [1] to [3], wherein

[0031] The molar ratio of methyl phenylcarbamate in the feed solution B to the methylene reagent in the feed solution A is (1-2.2):1;

[0032] The volume flow ratio of the feed liquid A to the feed liquid B is (0.2-2):1.

[0033] [5]. The synthesis method according to any one of [1] to [4], wherein

[0034] The micro mixer is a microchannel mixer, a membrane dispersion mixer or a micro mesh mixer;

[0035] The No. 1 microreactor, the No. 2 microreactor and the No. 3 microreactor are each independently a coil-type microreactor or a microchannel reactor.

[0036] [6]. The synthesis method according to any one of [1] to [5], wherein

[0037] The temperature in the micro mixer is 15 to 50° C., and the mixing time is 0.1 to 10 seconds;

[0038] The temperature in the No. 1 microreactor is 130-150° C., and the residence time is 0.1-30 min;

[0039] The temperature in the No. 2 microreactor is 110-130° C., and the residence time is 0.1-30 min;

[0040] The temperature in the No. 3 microreactor is 110-130° C., and the residence time is 0.1-30 min;

[0041] The pressure in the No. 1 microreactor, the No. 2 microreactor and the No. 3 microreactor is 1 to 10 bar.

[0042] [7]. The synthesis method according to any one of [1] to [6], wherein

[0043] The post-treatment comprises the steps of water washing and re-phase separation.

[0044] [8] The synthesis method according to any one of [1] to [7], wherein

[0045] The post-treatment temperature is below 50° C., and the residence time is 10 to 30 minutes.

[0046] [9]. Furthermore, the present invention also provides a device for implementing the synthesis method described in any one of [1] to [8], wherein:

[0047] The equipment comprises a micro mixer, a No. 1 microreactor, a No. 2 microreactor, a No. 3 microreactor and a liquid-liquid membrane separator which are connected in sequence.

[0048]

[10] The apparatus according to [9], wherein:

[0049] A washing liquid separator is also connected after the liquid-liquid membrane separator;

[0050] Preferably, the washing liquid separator is provided with a water washing device and a liquid-liquid separator.

[0051] Effects of the Invention

[0052] Based on the implementation of the above technical solution, the present invention can achieve the following technical effects:

[0053] 1) The present invention prepares diphenylmethane dicarbamate through a microchemical process with a micromixer and a microreactor as the core, and realizes efficient and safe conversion of the raw material phenylcarbamate by regulating factors such as the temperature, pressure, and amount of the methylene reagent added in the reaction system.

[0054] 2) Compared with the traditional autoclave production process currently used in industry, the amount of methyl phenylcarbamate is reduced, the cost of raw materials is saved, and the reaction time is greatly shortened, from several hours to less than 35 minutes. In particular, in the reaction form of microreactors connected in series with segmented temperature control, the concentration of the local methyl phenylcarbamate is reduced by adding the methyl phenyl reagent step by step into the reaction system and controlling the reaction temperature in blocks, thereby reducing the side reaction and achieving high-quality production of the product, so that the conversion rate of methyl phenylcarbamate can reach 97%, and the selectivity of 4,4'-diphenylmethane dicarbamate can reach 75%. Under the condition of improving the selectivity of the target product, the conversion rate of methyl phenylcarbamate is not reduced.

[0055] 3) The post-processing system designed by the present invention can make the product post-processing steps continuous, thereby realizing continuous production from raw materials to products, and reducing the operation time of post-processing from several hours to less than 30 minutes.

[0056] 4) The equipment and method provided by the present invention can reduce the generation of by-products, greatly reducing the cost and energy consumption of subsequent refining treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 The process flow diagram of one embodiment of the present invention. DETAILED DESCRIPTION

[0058] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0059] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0060] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0061] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0062] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0063] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0064] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.

[0065] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 23±2°C.

[0066] In this specification, the structural formula of the methyl phenylcarbamate is:

[0067] In this specification, the structural formula of the 4,4'-diphenylmethane dicarbamate (4,4'-MDC) is:

[0068]

[0069] In this specification, the structural formula of the 2,4'-diphenylmethane dicarbamate (2,4'-MDC) is:

[0070]

[0071] The present invention mainly provides a continuous synthesis method of diphenylmethane diaminomethyl ester and a device for implementing the synthesis method. The present invention is mainly based on the following insights:

[0072] The synthesis reaction of diphenylmethane dicarbamate, especially 4,4'-diphenylmethane dicarbamate, is a condensation reaction. Generally speaking, in the process of methylation, by-products such as trinuclear and polynuclear polymethylene polyphenylcarbamates are also produced, so the selectivity of 4,4'-diphenylmethane dicarbamate is usually around 60%. In order to reduce the generation of by-products, a common practice is to increase the feed ratio of methyl phenylcarbamate, and the molar ratio of methyl phenylcarbamate to methylation agent is above 4:1. This approach can effectively solve the generation of polymethylene polyphenylcarbamate, but greatly reduces the conversion rate of methyl phenylcarbamate. After the reaction, the excess methyl phenylcarbamate is miscible with diphenylmethane dicarbamate, which is difficult to recover and the separation process is complicated, resulting in increased costs, complex processes, and a long time, which is not suitable for large-scale industrial production.

[0073] Although a device and method for preparing diphenylmethane dicarbamate have been proposed in the prior art (for example, cited document 3), the device includes a material conveying unit, a reaction unit and a collection unit connected in sequence; the reaction unit includes a micro mixer and a reactor connected in sequence. Although the reaction time is greatly shortened by the specific selection of the micro mixer and the reactor, the reaction materials still need to be preheated by a preheater before mixing (the temperature is as high as 150° C.), which greatly increases the energy consumption. In addition, the post-processing process is relatively complicated and time-consuming. At the same time, such a device is still difficult to improve the selectivity of the isomer of 4,4'-diphenylmethane dicarbamate. Further, the present invention has found that when the synthesis process of the multi-stage continuous flow micro-reaction system is connected in series with the separation process of the post-processing system, and the temperature of the reaction system is controlled in blocks while the methylene reagent is added to the reaction system step by step, it is possible to reduce energy consumption and the occurrence of side reactions, improve the conversion rate of methyl phenylcarbamate, and then improve the selectivity of 4,4'-diphenylmethane dicarbamate, thereby also improving the separation efficiency of methyl phenylcarbamate, saving post-processing time. This provides feasibility for continuous and large-scale high-quality production of products. Further, the present invention has verified that the multi-stage continuous flow micro-reaction system and the post-processing system are sequentially arranged in the direction of the flow of the reaction raw materials to efficiently and reliably obtain highly selective 4,4'-diphenylmethane dicarbamate.

[0074] <First aspect>

[0075] A first aspect of the present invention provides a method for synthesizing diphenylmethane diaminomethyl ester, which comprises the following steps:

[0076] a) delivering feed liquid A and feed liquid B to a micro mixer for mixing, and then entering microreactor No. 1 for reaction to obtain a first oil-water mixed liquid;

[0077] b) introducing the first oil-water mixture and feed liquid C1 into microreactor No. 2 and reacting to obtain a second oil-water mixture;

[0078] c) introducing the second oil-water mixture and feed liquid C2 into microreactor No. 3 and reacting to obtain a third oil-water mixture;

[0079] d) subjecting the third oil-water mixture to phase separation through a liquid-liquid membrane separator, and obtaining an oil phase;

[0080] e) post-treating the oil phase to obtain an oil phase product;

[0081] Wherein, the feed liquid C1 and the feed liquid C2 are both derived from the feed liquid C, the feed liquid A and the feed liquid C are aqueous solutions containing an inorganic acid catalyst and a methylene agent, and the feed liquid B is a methyl phenylcarbamate solution.

[0082] Each step in the synthesis method of the present invention is described in detail below.

[0083] Step a)

[0084] According to the present invention, feed liquid A and feed liquid B are introduced into a micro-mixer for mixing and then enter into a No. 1 micro-reactor for reaction, so that raw materials for producing diphenylmethane dicarbamate can be liquid-liquid mixed and / or liquid-liquid dispersed in the micro-mixer. Because the micro-mixer can increase the contact specific surface area between the feed liquid A containing an inorganic acid catalyst and a methyleneization agent and the feed liquid B containing a phenylcarbamate solution, the raw materials before the reaction can be mixed and / or dispersed more uniformly, which is beneficial to the subsequent reaction.

[0085] In some specific embodiments, the inorganic acid catalyst includes one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0086] In some specific embodiments, the methyleneating agent includes any one of trioxymethylene, formaldehyde and dimethoxymethane.

[0087] In some specific embodiments, in the feed liquid A, the content of the inorganic acid catalyst is 15-40wt%, preferably 15-30wt%, more preferably 18-22wt%, for example, it can be 15wt%, 18wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt% and the like; the content of the methylene agent is 0.1-5wt%, preferably 0.5-3wt%, more preferably 0.8-2wt%, for example, it can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% and the like.

[0088] In some specific embodiments, in the feed liquid B, the content of methyl phenylcarbamate is 1-12wt%, preferably 5-10wt%, more preferably 6-10wt%, for example, it can be 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt% and the like.

[0089] In some specific embodiments, a pump (eg, a horizontal flow pump, a syringe pump, a diaphragm pump, etc.) is used to pass the feed liquid A and the feed liquid B into the micromixer.

[0090] In some specific embodiments, the molar ratio of the two feed liquids of the micro mixer, that is, the molar ratio of feed liquid A to feed liquid B, is adjusted so that the molar ratio of methyl phenylcarbamate contained in feed liquid B to the methylene reagent contained in feed liquid A is (1-2.2):1, preferably (1.2-2):1, for example, 1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, etc. By making the molar ratio of the methylene reagent to methyl phenylcarbamate within the above range, the generation of by-products can be reduced while ensuring a high conversion rate of methyl phenylcarbamate, thereby improving the selectivity of 4,4'-diphenylmethanedicarbamate.

[0091] Furthermore, the dosage ratio of feed liquid A to feed liquid B can be adjusted by adjusting the flow rate of feed liquid A and feed liquid B into the micro mixer. In some specific embodiments, the volume flow ratio of feed liquid A to feed liquid B can be (0.2-2):1.

[0092] The present invention has no particular limitation on the micromixer used, which can be any micromixer known in the art that is suitable for liquid-liquid mixing, such as a microchannel mixer, a membrane dispersion mixer or a micromesh mixer, etc. In a preferred embodiment, the micromixer is a microchannel mixer.

[0093] In some specific embodiments, the channel diameter of the micromixer is 0.1-2 mm, preferably 0.1-1.5 mm, for example, 0.2 mm, 0.25 mm, 0.5 mm, etc.

[0094] In some specific embodiments, the temperature in the micromixer is 15-50°C, preferably 20-40°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, etc.; by controlling the temperature in the micromixer within the above range, the reaction pipeline can be prevented from being blocked and the mixing efficiency can be improved.

[0095] In some specific embodiments, the mixing time of liquid A and liquid B in the micromixer is 0.1 to 10 s, for example, 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, etc.; by controlling the mixing time within the range of 0.1 to 10 s, sufficient mixing can be ensured while taking into account production efficiency.

[0096] The present invention uses a No. 1 microreactor to react methyl phenylcarbamate with a methylene reagent in the presence of an inorganic acid catalyst to obtain a first oil-water mixed solution. In the No. 1 microreactor, the methyl phenylcarbamate solution and the methylene reagent solution are in contact with each other to cause a condensation reaction.

[0097] The present invention has no particular limitation on the No. 1 microreactor used, which can be any microreactor known in the art that is suitable for liquid-liquid phase reactions, such as a coil-type microreactor or a microchannel reactor. Considering that the concentration of the inorganic acid catalyst in the condensation reaction of the present invention is high and the reaction temperature is high, in a preferred embodiment, the No. 1 microreactor is a coil-type microreactor, wherein the length of the coil can be 0.5m to 100m, and the diameter of the coil can be 0.1mm to 3mm.

[0098] In some specific embodiments, the reaction temperature in the microreactor No. 1 is 130-150°C, preferably 135-145°C, for example, 130°C, 132°C, 135°C, 138°C, 140°C, 142°C, 145°C, 148°C, 150°C, etc.; if the temperature is too low, the reaction cannot be completed, and if the temperature is too high, a large amount of polymethylene polyphenylcarbamate and other by-products will be generated. By controlling the temperature of microreactor No. 1 within the above range, the reaction efficiency can be effectively improved.

[0099] In some specific embodiments, the residence time in the microreactor No. 1 is 0.1 to 30 min, preferably 5 to 25 min, more preferably 10 to 20 min, for example, 3 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 28 min, 30 min, etc.; by controlling the residence time in microreactor No. 1 within the above range, the yield of diphenylmethane diaminomethyl ester can be guaranteed while reducing equipment size and investment.

[0100] In some specific embodiments, the pressure in the microreactor No. 1 is 1 to 10 bar, preferably 5 to 10 bar, for example, it can be 1 bar, 2 bar, 3 bar, 4 bar, 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar, etc.; by controlling the pressure in microreactor No. 1 within the above range, the yield of diphenylmethane diaminomethyl ester can be guaranteed while reducing the equipment size and investment.

[0101] Specifically, in the present invention, the solvent for dissolving methyl phenylcarbamate is not particularly limited, and can be any feasible inert organic solvent in the art, preferably an inert solvent having electron-withdrawing substituents on the benzene ring, such as chlorobenzene, nitrobenzene, o-dichlorobenzene, etc.

[0102] Step b) and step c)

[0103] To prevent the generation of excessive by-products, in the condensation reaction system, the first oil-water mixture and feed liquid C1 are introduced into microreactor No. 2 and reacted to obtain a second oil-water mixture; further, the second oil-water mixture and feed liquid C2 are introduced into microreactor No. 3 and reacted to obtain a third oil-water mixture.

[0104] In the present invention, the feed liquid C (i.e., an aqueous solution containing an inorganic acid catalyst and a methylene-forming agent) is sequentially introduced into the No. 2 microreactor and the No. 3 microreactor in steps, so that the reaction selectivity and conversion rate are improved.

[0105] In some specific embodiments, in the feed liquid C, the content of the inorganic acid catalyst is 15-40wt%, preferably 15-30wt%, more preferably 18-22wt%, for example, it can be 15wt%, 18wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, etc.; the content of the methylene agent is 20-100% of the content of the methylene agent in the feed liquid A, preferably 20-40%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 90%, etc.

[0106] In some specific embodiments, the volume flow ratio of the first oil-water mixture to the feed liquid C1 is (2-6):1, and the flow ratio of the second oil-water mixture to the feed liquid C2 is (2-6):1.

[0107] In some specific embodiments, the volume flow ratio of the slurry C1 to the slurry C2 is (0.5-2):1, preferably (0.8-1.6):1, for example, it can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc.

[0108] In the present invention, based on the total amount of the methylene reagent in the reaction system, the molar ratio of the methyl phenylcarbamate to the methylene reagent is 2.5:1 or less, preferably (0.8-2):1, for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, etc.

[0109] The present invention has no particular restrictions on the No. 2 microreactor and the No. 3 microreactor used, which can be any microreactor known in the art that is suitable for liquid-liquid phase reaction, for example, a coil microreactor or a microchannel reactor, etc. In a preferred embodiment, the No. 2 microreactor and the No. 3 microreactor are both coil microreactors, wherein the length of the coil can be 0.5m to 100m, and the diameter of the coil can be 0.1mm to 3mm.

[0110] In some specific embodiments, the reaction temperature in the microreactor No. 2 is 110-130°C, preferably 115-125°C, for example, it can be 110°C, 112°C, 115°C, 118°C, 120°C, 122°C, 125°C, 128°C, 130°C, etc.

[0111] In some specific embodiments, the residence time in the microreactor No. 2 is 0.1 to 30 min, preferably 5 to 25 min, more preferably 10 to 20 min, for example, it can be 3 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 28 min, 30 min, etc.

[0112] In some specific embodiments, the reaction temperature in the microreactor No. 3 is 110-130°C, preferably 115-125°C, for example, it can be 110°C, 112°C, 115°C, 118°C, 120°C, 122°C, 125°C, 128°C, 130°C, etc.

[0113] In some specific embodiments, the residence time in the microreactor No. 3 is 0.1 to 30 min, preferably 5 to 25 min, more preferably 10 to 20 min, for example, it can be 3 min, 5 min, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 25 min, 28 min, 30 min, etc.

[0114] In some specific embodiments, the pressure in microreactor No. 2 and microreactor No. 3 is 1-10 bar, preferably 5-10 bar, for example, it can be 1 bar, 2 bar, 3 bar, 4 bar, 5 bar, 6 bar, 7 bar, 8 bar, 9 bar, 10 bar, etc.

[0115] In some specific embodiments, a pump (eg, a syringe pump) is used to introduce feed solution C into microreactor No. 2 and microreactor No. 3, respectively.

[0116] Step d)

[0117] In step d), the oil phase and the water phase of the third oil-water mixture are separated.

[0118] In some specific embodiments, the third oil-water mixture is passed into a liquid-liquid membrane separator for phase separation, wherein the liquid-liquid membrane separator is provided with a water phase outlet and an oil phase outlet, and the oil phase outlet is connected to the inlet of the post-treatment system. Therefore, after phase separation, the water phase is discharged from one outlet of the liquid-liquid membrane separator, and the oil phase is directly transported from the other outlet of the liquid-liquid membrane separator to the post-treatment system for subsequent post-treatment.

[0119] Step e)

[0120] The present invention further comprises the step of post-treating the oil phase obtained in step d).

[0121] In some specific embodiments, the post-treatment comprises the steps of water washing and re-phase separation.

[0122] In some specific embodiments, the post-treatment temperature is below 50° C. and the time is 10 to 30 minutes.

[0123] In some preferred embodiments, the oil phase is post-treated through a washing separator to obtain an oil phase product.

[0124] Additional Steps

[0125] In one embodiment, the present invention further comprises the steps of preparing feed liquid A, feed liquid B and feed liquid C.

[0126] In one embodiment, feed liquid A and feed liquid C are prepared by mixing a methylenating agent with an aqueous solution of an inorganic acid catalyst.

[0127] In one embodiment, feed solution B is prepared by mixing methyl phenylcarbamate and an inert organic solvent (eg, o-dichlorobenzene, chlorobenzene).

[0128] Through the implementation of the above synthesis method, the conversion rate of methyl phenylcarbamate of the present invention can be 97%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate can be 75%.

[0129] <Second Aspect>

[0130] The second aspect of the present invention provides an apparatus for implementing the synthesis method described in the first aspect of the present invention, wherein the apparatus comprises a micromixer, microreactor No. 1, microreactor No. 2, microreactor No. 3, a liquid-liquid membrane separator and a washing separator connected in sequence.

[0131] Specifically, the washing liquid separator is provided with a water washing device and a liquid-liquid separator.

[0132] By using the equipment of the present invention, it is possible to ensure that the synthesis of diphenylmethane diaminomethyl ester of the present invention is carried out efficiently and orderly, and the equipment has good pressure resistance and high production efficiency.

[0133] Example

[0134] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0135] The microreactor used in the following examples is as follows:

[0136] Micro mixer No. 1 is a T-type microchannel mixer: the material is peek, and the channel diameter is 0.25 mm.

[0137] Microreactor No. 1 is a coil-type microreactor: the material is PTFE, the coil diameter is 0.8 mm, and the length is 20 m;

[0138] Microreactor No. 2 is a coil-type microreactor: the material is PTFE, the coil diameter is 0.8 mm, and the length is 20 m;

[0139] Microreactor No. 3 is a coil-type microreactor: the material is PTFE, the coil diameter is 0.8 mm, and the length is 20 m.

[0140] Pump: Use a syringe pump to transport liquid A and liquid C, and use a horizontal flow pump to transport liquid B.

[0141] The conversions and selectivities described in the following examples were determined by liquid chromatography.

[0142] Example 1

[0143] 0.5865 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid A, 360 g of o-dichlorobenzene and 28.8 g of methyl phenylcarbamate were mixed as feed liquid B, and 0.1173 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid C.

[0144] like Figure 1 As shown, feed liquid A (flow rate of 0.53 mL / min) and feed liquid B (flow rate of 0.47 mL / min) are transported to micro mixer No. 1 (temperature of 30°C, mixing time of 2s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde is 2: 1. Then, they enter microreactor No. 1 connected to the outlet of micro mixer No. 1 (temperature of 140°C, residence time of 15min, pressure of 8bar) for condensation reaction to obtain the first oil-water mixture.

[0145] The feed liquid C (flow rate of 0.2 mL / min) and the first oil-water mixture obtained from the outlet of microreactor No. 1 were transported to microreactor No. 2 (temperature of 120°C, residence time of 10 min, pressure of 8 bar) using a pump for reaction to obtain a second oil-water mixture.

[0146] The feed liquid C (flow rate of 0.2 mL / min) and the second oil-water mixture obtained from the outlet of microreactor No. 2 were transported to microreactor No. 3 (temperature of 120°C, residence time of 7 min, pressure of 8 bar) using a pump for reaction to obtain a third oil-water mixture.

[0147] The third oil-water mixed liquid obtained from the outlet of the No. 3 microreactor is transported to a liquid-liquid membrane separator for liquid separation treatment to obtain a crude oil phase product.

[0148] The crude oil phase product was treated by a washing separator for 20 min to obtain an oil phase product.

[0149] The results showed that the conversion rate of methyl phenylcarbamate was 96.2%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate was 75.1%.

[0150] Example 2

[0151] 0.8798 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid A, 360 g of o-dichlorobenzene and 28.8 g of methyl phenylcarbamate were mixed as feed liquid B, and 0.2639 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid C.

[0152] like Figure 1 As shown, feed liquid A (flow rate of 0.53 mL / min) and feed liquid B (flow rate of 0.47 mL / min) are transported to micro mixer No. 1 (temperature of 30°C, mixing time of 2s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde is 2:1.5. Then, they enter microreactor No. 1 connected to the outlet of micro mixer No. 1 (temperature of 140°C, residence time of 15min, pressure of 8bar) for condensation reaction to obtain the first oil-water mixture.

[0153] The feed liquid C (flow rate of 0.35 mL / min) and the first oil-water mixture obtained from the outlet of microreactor No. 1 were transported to microreactor No. 2 (temperature of 120°C, residence time of 10 min, pressure of 8 bar) by a pump for reaction to obtain a second oil-water mixture.

[0154] The feed liquid C (flow rate of 0.25 mL / min) and the second oil-water mixture obtained from the outlet of microreactor No. 2 were transported to microreactor No. 3 (temperature of 120°C, residence time of 7 min, pressure of 8 bar) using a pump for reaction to obtain a third oil-water mixture.

[0155] The third oil-water mixed liquid obtained from the outlet of the No. 3 microreactor is transported to a liquid-liquid membrane separator for liquid separation treatment to obtain a crude oil phase product.

[0156] The crude oil phase product was treated by a washing separator for 20 min to obtain an oil phase product.

[0157] The results showed that the conversion rate of methyl phenylcarbamate was 97.5%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate was 65.1%.

[0158] Comparative Example 1

[0159] Compared with Example 1, the difference is that this comparative example does not adopt segmented feeding.

[0160] 0.5865 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid A, and 360 g of o-dichlorobenzene and 28.8 g of methyl phenylcarbamate were mixed as feed liquid B.

[0161] The feed liquid A (flow rate of 0.53 mL / min) and the feed liquid B (flow rate of 0.47 mL / min) were transported to the No. 1 micro mixer (temperature of 30°C, mixing time of 2s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1. Then, the feed liquid entered the No. 1 micro reactor connected to the outlet of the No. 1 micro mixer (temperature of 140°C, residence time of 32 min, pressure of 8 bar) for condensation reaction to obtain an oil-water mixture.

[0162] The oil-water mixture obtained from the outlet of microreactor No. 1 is transported to a liquid-liquid membrane separator for liquid separation to obtain a crude oil phase product.

[0163] The crude oil phase product was treated by a washing separator for 20 min to obtain an oil phase product.

[0164] The results showed that the conversion rate of methyl phenylcarbamate was 83.1%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate was 58.2%.

[0165] Comparative Example 2

[0166] Compared with Example 1, the difference is that this comparative example does not use a continuous washing liquid separator.

[0167] 0.5865 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid A, 360 g of o-dichlorobenzene and 28.8 g of methyl phenylcarbamate were mixed as feed liquid B, and 0.1173 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid C.

[0168] The feed liquid A (flow rate of 0.53 mL / min) and the feed liquid B (flow rate of 0.47 mL / min) were transported to the No. 1 micro mixer (temperature of 30°C, mixing time of 2s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2: 1. Then, the feed liquid A entered the No. 1 micro reactor connected to the outlet of the No. 1 micro mixer (temperature of 140°C, residence time of 15min, pressure of 8bar) for condensation reaction to obtain the first oil-water mixed liquid.

[0169] The feed liquid C (flow rate of 0.2 mL / min) and the first oil-water mixture obtained from the outlet of microreactor No. 1 were transported to microreactor No. 2 (temperature of 120°C, residence time of 10 min, pressure of 8 bar) using a pump for reaction to obtain a second oil-water mixture.

[0170] The feed liquid C (flow rate of 0.2 mL / min) and the second oil-water mixture obtained from the outlet of microreactor No. 2 were transported to microreactor No. 3 (temperature of 120°C, residence time of 7 min, pressure of 8 bar) using a pump for reaction to obtain a third oil-water mixture.

[0171] The third oil-water mixture obtained from the outlet of microreactor No. 3 was phase-separated, cooled and allowed to stand for 1 hour, and washed with water for 30 minutes, for a total of three times.

[0172] The results showed that the conversion rate of methyl phenylcarbamate was 96.4%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate was 74.1%.

[0173] Comparative Example 3

[0174] Compared with Example 1, the difference is that this comparative example does not use microreactor No. 3.

[0175] 0.5865 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid A, 360 g of o-dichlorobenzene and 28.8 g of methyl phenylcarbamate were mixed as feed liquid B, and 0.1173 g of paraformaldehyde and 56.25 g of 20 wt % hydrochloric acid were mixed as feed liquid C.

[0176] The feed liquid A (flow rate of 0.53 mL / min) and the feed liquid B (flow rate of 0.47 mL / min) were transported to the No. 1 micro mixer (temperature of 30°C, mixing time of 2s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2: 1. Then, the feed liquid A entered the No. 1 micro reactor connected to the outlet of the No. 1 micro mixer (temperature of 140°C, residence time of 15min, pressure of 8bar) for condensation reaction to obtain the first oil-water mixed liquid.

[0177] The feed liquid C (flow rate of 0.4 mL / min) and the first oil-water mixture obtained from the outlet of microreactor No. 1 were transported to microreactor No. 2 (temperature of 120°C, residence time of 17 min, pressure of 8 bar) using a pump for reaction to obtain a second oil-water mixture.

[0178] The second oil-water mixed liquid obtained from the outlet of the No. 2 microreactor is transported to a liquid-liquid membrane separator for liquid separation to obtain a crude oil phase product.

[0179] The crude oil phase product was treated by a washing separator for 20 min to obtain an oil phase product.

[0180] The results showed that the conversion rate of methyl phenylcarbamate was 95.3%, and the selectivity of methyl 4,4'-diphenylmethane dicarbamate was 62.2%.

[0181] Industrial Applicability

[0182] The continuous synthesis method of methyl diphenylmethane dicarbamate of the present invention can be widely used in the synthesis of methyl diphenylmethane dicarbamate in industry.

Claims

1. A continuous synthesis method of diphenylmethane diaminomethyl ester, characterized in that: The following steps are involved: a) delivering feed liquid A and feed liquid B to a micro mixer for mixing, and then entering microreactor No. 1 for reaction to obtain a first oil-water mixed liquid; b) introducing the first oil-water mixture and feed liquid C1 into microreactor No. 2 and reacting to obtain a second oil-water mixture; c) introducing the second oil-water mixture and feed liquid C2 into microreactor No. 3 and reacting to obtain a third oil-water mixture; d) subjecting the third oil-water mixture to phase separation through a liquid-liquid membrane separator, and obtaining an oil phase; e) post-treating the oil phase to obtain an oil phase product; Wherein, the feed liquid C1 and the feed liquid C2 are both derived from the feed liquid C, the feed liquid A and the feed liquid C are aqueous solutions containing an inorganic acid catalyst and a methylene agent, and the feed liquid B is a methyl phenylcarbamate solution; Furthermore, the molar ratio of the methyl phenylcarbamate to the methylene-forming agent is 2.5:1 or less.

2. The synthesis method according to claim 1, characterized in that The inorganic acid catalyst includes one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; The methylene agent includes any one of trioxymethylene, formaldehyde and dimethoxymethane.

3. The synthesis method according to claim 1 or 2, characterized in that The content of the inorganic acid catalyst in the feed liquid A is 15-40wt%, and the content of the methylene agent is 0.1-5wt%; The content of methyl phenylcarbamate in liquid B is 1 to 12 wt %; The content of the inorganic acid catalyst in the feed liquid C is 15-40wt%, and the content of the methylene-forming agent is 20-100% of the content of the methylene-forming agent in the feed liquid A.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The molar ratio of methyl phenylcarbamate in the feed solution B to the methylene reagent in the feed solution A is (1-2.2):1; The volume flow ratio of the feed liquid A to the feed liquid B is (0.2-2):

1.

5. The synthesis method according to any one of claims 1 to 4, characterized in that The micro mixer is a microchannel mixer, a membrane dispersion mixer or a micro mesh mixer; The No. 1 microreactor, the No. 2 microreactor and the No. 3 microreactor are each independently a coil-type microreactor or a microchannel reactor.

6. The synthesis method according to any one of claims 1 to 5, characterized in that The temperature in the micro mixer is 15 to 50° C., and the mixing time is 0.1 to 10 seconds; The temperature in the No. 1 microreactor is 130-150° C., and the residence time is 0.1-30 min; The temperature in the No. 2 microreactor is 110-130° C., and the residence time is 0.1-30 min; The temperature in the No. 3 microreactor is 110-130° C., and the residence time is 0.1-30 min; The pressure in the No. 1 microreactor, the No. 2 microreactor and the No. 3 microreactor is 1 to 10 bar.

7. The synthesis method according to any one of claims 1 to 6, characterized in that The post-treatment comprises the steps of water washing and re-phase separation.

8. The synthesis method according to any one of claims 1 to 7, characterized in that The post-treatment temperature is below 50° C. and the time is 10 to 30 minutes.

9. A device for implementing the synthesis method according to any one of claims 1 to 8, characterized in that: The equipment comprises a micro mixer, a No. 1 microreactor, a No. 2 microreactor, a No. 3 microreactor and a liquid-liquid membrane separator which are connected in sequence.

10. The device according to claim 9, characterized in that A washing liquid separator is also connected after the liquid-liquid membrane separator; Preferably, the washing liquid separator is provided with a water washing device and a liquid-liquid separator.

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