Continuous process and apparatus for the synthesis of methyldiphenylmethane dicarbamate

Abstract

The present application relates to a kind of continuous synthesis method and equipment of methylene dianiline, based on the efficient microscale mixing characteristics of microreactor, good mass transfer and heat transfer characteristics and the characteristics of accurately controlled reaction, the production of methylene dianiline and subsequent separation continuous operation, improve the reaction efficiency, while avoiding cumbersome separation step, improve separation efficiency, directly obtain oil phase product for pyrolysis.The multi-stage continuous flow microreaction system of the present application, by methylene reagent is added to the reaction system in steps and block control reaction temperature, thereby reducing the local methylene reagent concentration, reduce side reaction, realize the high quality production of product.Based on the production process of the present application, benzylaminomethylcarbamate 97% conversion can be realized in about 30min, after subsequent separation water washing, the reaction selectivity of 4,4'-MDC is higher than 75%.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical synthesis technology, specifically relating to a method for the continuous synthesis of diphenylmethane dicarboxylate in a microreactor. Background Technology

[0002] Diphenylmethane diisocyanate (MDI) is an important raw material for the synthesis of polyurethane and is widely used in aerospace, shipbuilding, automotive, construction, electronics, coatings, artificial leather, glass, footwear, and fiber industries. It has isomers such as 2,4'-MDI, 2,2'-MDI, and 4,4'-MDI, with 4,4'-MDI being the most widely used.

[0003] Currently, industrial production of MDI uses the phosgene process, which involves the following steps: aniline reacts with formaldehyde to produce diphenylmethane diamine (MDA), which then reacts with phosgene to obtain an MDI mixture. Finally, the mixture is separated by distillation to obtain the MDI monomer. Although this method is simple, technically mature, and widely used, it has drawbacks such as highly toxic raw materials, difficulty in removing residual chlorine from the product, corrosion of equipment by the byproduct hydrochloric acid, and environmental pollution.

[0004] Methyl diphenylmethane dicarboxylate (MDC) is an important intermediate in the non-phosgene synthesis of MDI, therefore, research on its clean and efficient synthesis is of great significance. Currently, MDC synthesis mainly employs a batch stirred tank process (e.g., cited references 1 and 2), which involves mixing methyl phenylcarboxylate with a formaldehyde solution containing an acid catalyst. Throughout the production process, factors such as the ratio of formaldehyde to methyl phenylcarboxylate, reactant concentrations, reaction temperature, and acid catalyst concentration all significantly impact the conversion rate and quality of the product. Furthermore, the reaction time for this process is typically 2–6 hours, resulting in low efficiency. Therefore, developing a highly efficient and controllable continuous synthesis process and equipment is an inevitable trend.

[0005] Reference 3 discloses an apparatus and method for preparing diphenylmethane dicarboxylate, comprising dissolving phenylcarboxylate in a solvent to obtain an oil phase material, dissolving a methyleneizing agent in an inorganic acid solution to obtain an aqueous phase material, emulsifying the oil and aqueous phase materials through a micromixer after preheating, and then performing a condensation reaction. After the reaction is completed, the mixture is condensed and allowed to stand for separation to obtain an oil phase product, which is then washed with water to obtain the diphenylmethane dicarboxylate. Although this method uses a micromixer to enhance the reaction and greatly shorten the reaction time, it does not describe the 4,4'-diphenylmethane dicarboxylate isomer, nor does it mention the selectivity of this isomer. Furthermore, the post-processing includes cooling, standing for separation, washing, and phase separation of the product, which is complex, cumbersome, and time-consuming, making it unsuitable for industrial applications. In addition, the oil and aqueous phase materials are preheated to 150°C before entering the micromixer, resulting in high energy consumption.

[0006] References:

[0007] Reference 1: CN107434774B

[0008] Reference 2: CN117185962A

[0009] Reference 3: CN113926403A Summary of the Invention

[0010] The problem the invention aims to solve

[0011] In view of the problems existing in the prior art, such as low production efficiency of condensation reaction, low selectivity of target product, and long post-reaction processing time, this invention first provides a continuous synthesis method for diphenylmethane dicarboxylate. This method connects the synthesis process of a multi-stage continuous flow microreactor system with the separation process of a post-processing system, aiming to achieve efficient conversion and rapid separation from reactants to products.

[0012] Furthermore, the present invention also provides an apparatus for implementing the method of synthesizing diphenylmethane dicarboxylate. The apparatus has a simple structure, can ensure that the processing method is carried out efficiently and in an orderly manner, and has good pressure resistance, enabling it to operate stably for a long time.

[0013] Solution for solving the problem

[0014] The present invention has found that the above-mentioned technical problems can be solved by the following technical solutions:

[0015] [1]. This invention provides a continuous synthesis method for diphenylmethane dicarboxylate, comprising the following steps:

[0016] a) Feed A and feed B are transported to a micro mixer for mixing, and then enter microreactor No. 1 for reaction to obtain the first oil-water mixture;

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

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

[0019] d) The third oil-water mixture is subjected to phase separation treatment using a liquid-liquid membrane separator to obtain the oil phase;

[0020] e) Post-process the oil phase to obtain the oil phase product;

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

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

[0023] [2]. According to the synthesis method described in [1], wherein,

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

[0025] The methyleneizing agent includes any one of trioxymethane, formaldehyde, and dimethoxymethane.

[0026] [3]. According to the synthesis method described in [1] or [2], wherein,

[0027] The inorganic acid catalyst in feed solution A has a content of 15-40 wt%, and the methyleneizing agent has a content of 0.1-5 wt%.

[0028] The content of methyl phenylcarbamate in feed solution B is 1-12 wt%.

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

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

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

[0032] The volumetric flow rate ratio of liquid A to liquid B is (0.2~2):1.

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

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

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

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

[0037] The temperature in the micro mixer is 15–50°C, and the mixing time is 0.1–10 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, No. 2 and No. 3 microreactors is 1 to 10 bar.

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

[0043] The post-processing includes water washing and re-phase separation steps.

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

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

[0046] [9]. Furthermore, the present invention also provides an apparatus for carrying out the synthesis method described in any one of [1]-[8], wherein,

[0047] The device includes a micro mixer, a No. 1 microreactor, a No. 2 microreactor, a No. 3 microreactor, and a liquid-liquid membrane separator connected in sequence.

[0048]

[10] . The device according to [9], wherein,

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

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

[0051] The 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) This invention prepares diphenylmethane dicarboxylate using a micro-chemical process centered on micro-mixers and microreactors. By controlling factors such as temperature, pressure, and the amount of methyleneization reagent added to the reaction system, the efficient and safe conversion of the raw material methyl phenylcarboxylate is achieved.

[0054] 2) Compared with the traditional batch reactor production process currently used in industry, this method reduces the amount of methyl phenylcarbamate used, saves raw material costs, and significantly shortens the reaction time from several hours to less than 35 minutes. In particular, by using a series of microreactors with segmented temperature control, the local concentration of the methyleneizing agent is reduced by adding the methyleneizing agent to the reaction system stepwise and controlling the reaction temperature in sections, thereby reducing side reactions and achieving high-quality product production. This results in a methyl phenylcarbamate conversion rate of up to 97% and a selectivity of 4,4'-diphenylmethanedicarbamate of up to 75%. While improving the selectivity of the target product, the conversion rate of methyl phenylcarbamate is not reduced.

[0055] 3) The post-processing system designed in this invention can make the post-processing steps of the product 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 this invention can reduce the generation of by-products and greatly reduce the cost and energy consumption of subsequent refining processes. Attached Figure Description

[0057] Figure 1 This is a process flow diagram of one embodiment of the present invention. Detailed Implementation

[0058] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0059] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

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

[0061] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0062] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0063] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0064] In this specification, the numerical range indicated by "above" or "below" refers to the numerical range that includes the stated number.

[0065] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 23±2℃.

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

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

[0068]

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

[0070]

[0071] This invention primarily provides a continuous synthesis method for diphenylmethane dicarboxylate and the apparatus for carrying out this synthesis method. This invention is mainly based on the following insights:

[0072] The synthesis of methyl diphenylmethanedicarbamate, especially methyl 4,4'-diphenylmethanedicarbamate, is a condensation reaction. Typically, trinuclear and polynuclear polymethylene polyphenylcarbamate byproducts are generated during methyleneization, resulting in a selectivity of around 60% for 4,4'-diphenylmethanedicarbamate. To reduce byproduct formation, a common practice is to increase the feed ratio of methyl phenylcarbamate, with a molar ratio of methyl phenylcarbamate to methyleneizing agent exceeding 4:1. This effectively addresses the formation of polymethylene polyphenylcarbamate, but significantly reduces the conversion rate of methyl phenylcarbamate. Furthermore, excess methyl phenylcarbamate after the reaction is miscible with methyl diphenylmethanedicarbamate, making recovery difficult and separation complex, leading to increased costs, a complex process, and a long processing time, making it unsuitable for large-scale industrial production.

[0073] Although an apparatus and method for preparing diphenylmethane dicarboxylate has been proposed in the prior art (e.g., reference 3), the apparatus 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 reactants still need to be preheated by a preheater (at a temperature as high as 150°C) before mixing, which greatly increases energy consumption. In addition, the post-processing is relatively complex, cumbersome, and time-consuming. At the same time, such an apparatus still presents challenges in improving the selectivity of the 4,4'-diphenylmethane dicarboxylate isomer. Furthermore, this invention discovers that when the synthesis process of a multi-stage continuous flow microreactor system is connected in series with the separation process of a post-treatment system, and the methylating agent is added to the reaction system stepwise while the temperature of the reaction system is controlled in sections, energy consumption and side reactions can be reduced, the conversion rate of methyl phenylcarbamate can be improved, and thus the selectivity of methyl 4,4'-diphenylmethanedicarbamate can be improved. This also improves the separation efficiency of methyl 4,4'-diphenylmethanedicarbamate and saves post-treatment time. This provides feasibility for continuous, large-scale, high-quality production of the product. Furthermore, this invention has verified that sequentially setting up a multi-stage continuous flow microreactor system and a post-treatment system in the direction of the reactant flow can efficiently and reliably obtain highly selective methyl 4,4'-diphenylmethanedicarbamate.

[0074] <First Aspect>

[0075] The first aspect of the present invention provides a method for synthesizing diphenylmethane dicarboxylate, comprising the following steps:

[0076] a) Feed A and feed B are transported to a micro mixer for mixing, and then enter microreactor No. 1 for reaction to obtain the first oil-water mixture;

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

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

[0079] d) The third oil-water mixture is subjected to phase separation treatment using a liquid-liquid membrane separator to obtain the oil phase;

[0080] e) Post-process the oil phase to obtain the oil phase product;

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

[0082] The following describes in detail each step of the synthesis method of the present invention.

[0083] Step a)

[0084] In this invention, feed solution A and feed solution B are mixed in a micro mixer and then fed into microreactor No. 1 for reaction. This allows the raw materials for producing diphenylmethane dicarboxylate to undergo liquid-liquid mixing and / or liquid-liquid dispersion in the micro mixer. Because the micro mixer can increase the contact surface area between feed solution A, which contains inorganic acid catalyst and methylene reagent, and feed solution B, which contains methyl phenylcarboxylate solution, the mixing and / or dispersion of the raw materials before the reaction is more uniform, 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 implementations, the methyleneizing agent includes any one of trioxymethane, formaldehyde, and dimethoxymethane.

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

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

[0089] In some specific implementations, a pump (e.g., a horizontal flow pump, a syringe pump, a diaphragm pump, etc.) is used to pass liquid A and liquid B into the micro mixer.

[0090] In some specific implementations, the ratio of the two feed liquids in the micromixer, i.e., the ratio of feed liquid A to feed liquid B, is adjusted so that the molar ratio of methyl phenylcarbamate in feed liquid B to the methyleneizing agent in feed liquid A is (1-2.2):1, preferably (1.2-2):1. For example, ratios such as 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, and 2.2:1 can be used. By maintaining the molar ratio of the methyleneizing agent to methyl phenylcarbamate within the above range, the formation of byproducts can be reduced while ensuring a high conversion rate of methyl phenylcarbamate, thus improving the selectivity of 4,4'-diphenylmethanedicarbamate.

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

[0092] The present invention does not particularly limit the micromixer used; it can be any micromixer known in the art suitable for liquid-liquid mixing, such as microchannel mixers, membrane dispersion mixers, or microsieve mixers. In a preferred embodiment, the micromixer is a microchannel mixer.

[0093] In some specific implementations, the channel diameter of the micro mixer is 0.1 to 2 mm, preferably 0.1 to 1.5 mm, for example, 0.2 mm, 0.25 mm, 0.5 mm, etc.

[0094] In some specific implementations, the temperature in the micro mixer 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 micro mixer within the above range, blockage of the reaction pipeline can be prevented and mixing efficiency can be improved.

[0095] In some specific implementation schemes, the mixing time of liquid A and liquid B in the micro mixer is 0.1 to 10 seconds, for example, it can be 1 second, 2 seconds, 3 seconds, 4 seconds, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds, etc. By controlling the mixing time within the range of 0.1 to 10 seconds, production efficiency can be taken into account while ensuring sufficient mixing.

[0096] This invention utilizes a No. 1 microreactor to react methyl phenylcarbamate with a methylene methylating agent in the presence of an inorganic acid catalyst to obtain a first oil-water mixture. The process involves a condensation reaction between the methyl phenylcarbamate solution and the methylene methylating agent solution in the oil-water two-phase contact within the No. 1 microreactor.

[0097] The present invention does not impose any particular limitation on the first microreactor used, which can be any microreactor known in the art suitable for liquid-liquid phase reactions, such as coil-type microreactors or microchannel reactors. Considering the high concentration of inorganic acid catalyst and the high reaction temperature in the condensation reaction of the present invention, in a preferred embodiment, the first 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 implementations, the reaction temperature in the No. 1 microreactor 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; if the temperature is too high, a large amount of polymethylene polyphenylcarbamate and other byproducts will be generated. By controlling the temperature of the No. 1 microreactor within the above range, the reaction efficiency can be effectively improved.

[0099] In some specific implementations, the residence time in the No. 1 microreactor 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. By controlling the residence time in the No. 1 microreactor within the above range, the yield of diphenylmethane dicarboxylate can be guaranteed while reducing equipment size and investment.

[0100] In some specific implementations, the pressure in the No. 1 microreactor 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 the No. 1 microreactor within the above range, the yield of diphenylmethane dicarboxylate can be guaranteed while reducing equipment size and investment.

[0101] Specifically, in this 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 with electron-withdrawing substituents on the benzene ring, such as chlorobenzene, nitrobenzene, or o-dichlorobenzene.

[0102] Steps b) and c)

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

[0104] This invention improves both the reaction selectivity and conversion rate by sequentially introducing feed solution C (i.e., an aqueous solution containing an inorganic acid catalyst and a methyleneizing agent) into microreactors No. 2 and No. 3.

[0105] In some specific embodiments, the inorganic acid catalyst content in the feed solution C is 15-40 wt%, preferably 15-30 wt%, more preferably 18-22 wt%, for example, it can be 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, etc.; the content of the methylene methylating agent is 20-100% of the methylene methylating agent content in feed solution 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 implementations, the volumetric flow rate ratio of the first oil-water mixture to the feed liquid C1 is (2-6):1, and the flow rate ratio of the second oil-water mixture to the feed liquid C2 is (2-6):1.

[0107] In some specific implementations, the volumetric flow rate ratio of liquid C1 to liquid C2 is (0.5-2):1, preferably (0.8-1.6):1, and can be, for example, 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 this invention, based on the total amount of methyleneizing reagent used in the reaction system, the molar ratio of methyl phenylcarbamate to the methyleneizing reagent is 2.5:1 or less, preferably (0.8 to 2):1, for example, it can be 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] This invention does not impose any particular limitation on the use of microreactor No. 2 and microreactor No. 3, which can be any microreactor known in the art suitable for liquid-liquid phase reactions, such as coil-type microreactors or microchannel reactors. In a preferred embodiment, both microreactor No. 2 and microreactor No. 3 are coil-type 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 implementations, the reaction temperature in the No. 2 microreactor is 110-130℃, preferably 115-125℃, for example, it can be 110℃, 112℃, 115℃, 118℃, 120℃, 122℃, 125℃, 128℃, 130℃, etc.

[0111] In some specific implementations, the residence time in the No. 2 microreactor 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 implementations, the reaction temperature in the No. 3 microreactor is 110-130℃, preferably 115-125℃, for example, it can be 110℃, 112℃, 115℃, 118℃, 120℃, 122℃, 125℃, 128℃, 130℃, etc.

[0113] In some specific implementations, the residence time in the No. 3 microreactor 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 implementations, the pressure in the No. 2 and No. 3 microreactors 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.

[0115] In some specific implementations, a pump (e.g., an injection pump) is used to feed liquid C into microreactors 2 and 3, respectively.

[0116] Step d)

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

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

[0119] Step e)

[0120] The present invention also includes a step of post-processing the oil phase obtained in step d).

[0121] In some specific implementations, the post-processing includes water washing and re-phase separation steps.

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

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

[0124] Other steps

[0125] In one embodiment, the present invention further includes the step of preparing liquid A, liquid B and liquid C.

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

[0127] In one embodiment, feed solution B is prepared by mixing methyl phenylcarbamate with an inert organic solvent (e.g., 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'-diphenylmethanedicarbamate can be 75%.

[0129] <Second aspect>

[0130] A 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 micro mixer, a No. 1 microreactor, a No. 2 microreactor, a No. 3 microreactor, a liquid-liquid membrane separator, and a washing separator connected in sequence.

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

[0132] By using the equipment of the present invention, the synthesis of diphenylmethane dicarboxylate of the present invention can be carried out efficiently and in an orderly manner, 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 with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0135] The microreactors used in the following examples are as follows:

[0136] Micromixer No. 1 is a T-type microchannel mixer: made of PEEK material, with a channel diameter of 0.25mm.

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

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

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

[0140] Pumps: Injection pumps are used to deliver liquid A and liquid C, and horizontal flow pumps are used to deliver liquid B.

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

[0142] Example 1

[0143] Mix 0.5865g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution A; mix 360g of o-dichlorobenzene and 28.8g of methyl phenylcarbamate to form solution B; and mix 0.1173g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution C.

[0144] like Figure 1 As shown, feed solution A (flow rate 0.53 mL / min) and feed solution B (flow rate 0.47 mL / min) were pumped into micromixer No. 1 (temperature 30℃, mixing time 2 s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1. The mixture then entered microreactor No. 1 (temperature 140℃, residence time 15 min, pressure 8 bar), which was connected to the outlet of micromixer No. 1, for a 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 are transported to microreactor No. 2 (temperature of 120℃, residence time of 10 min, and pressure of 8 bar) by a pump and reacted to obtain the 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 are pumped to microreactor No. 3 (temperature of 120℃, residence time of 7 min, and pressure of 8 bar) for reaction to obtain the third oil-water mixture.

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

[0148] The crude oil phase product was processed by a washing separator for 20 minutes to obtain the oil phase product.

[0149] The conversion rate of methyl phenylcarbamate was 96.2%, and the selectivity of methyl 4,4'-diphenylmethanedicarbamate was 75.1%.

[0150] Example 2

[0151] Mix 0.8798g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution A; mix 360g of o-dichlorobenzene and 28.8g of methyl phenylcarbamate to form solution B; and mix 0.2639g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution C.

[0152] like Figure 1 As shown, feed solution A (flow rate 0.53 mL / min) and feed solution B (flow rate 0.47 mL / min) were pumped into micromixer No. 1 (temperature 30℃, mixing time 2 s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1.5. The mixture then entered microreactor No. 1 (temperature 140℃, residence time 15 min, pressure 8 bar), which was connected to the outlet of micromixer No. 1, for a 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 are transported to microreactor No. 2 (temperature of 120℃, residence time of 10 min, and pressure of 8 bar) by a pump and reacted to obtain the 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 are transported to microreactor No. 3 (temperature of 120℃, residence time of 7 min, and pressure of 8 bar) and reacted to obtain the third oil-water mixture.

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

[0156] The crude oil phase product was processed by a washing separator for 20 minutes to obtain the oil phase product.

[0157] The conversion rate of methyl phenylcarbamate was 97.5%, and the selectivity of methyl 4,4'-diphenylmethanedicarbamate was 65.1%.

[0158] Comparative Example 1

[0159] The difference compared to Example 1 is that this comparative example did not use segmented feeding.

[0160] Mix 0.5865g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution A, and mix 360g of o-dichlorobenzene and 28.8g of methyl phenylcarbamate to form solution B.

[0161] Liquid A (flow rate 0.53 mL / min) and liquid B (flow rate 0.47 mL / min) were pumped into micromixer No. 1 (temperature 30℃, mixing time 2 s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1. The mixture then entered microreactor No. 1 (temperature 140℃, residence time 32 min, pressure 8 bar), connected to the outlet of micromixer No. 1, for a 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 separation to obtain crude oil product.

[0163] The crude oil phase product was processed by a washing separator for 20 minutes to obtain the oil phase product.

[0164] The conversion rate of methyl phenylcarbamate was 83.1%, and the selectivity of methyl 4,4'-diphenylmethanedicarbamate was 58.2%.

[0165] Comparative Example 2

[0166] The difference compared to Example 1 is that this comparative example did not use a continuous washing dispenser.

[0167] Mix 0.5865g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution A; mix 360g of o-dichlorobenzene and 28.8g of methyl phenylcarbamate to form solution B; and mix 0.1173g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution C.

[0168] Liquid A (flow rate 0.53 mL / min) and liquid B (flow rate 0.47 mL / min) were pumped into micromixer No. 1 (temperature 30℃, mixing time 2 s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1. The mixture then entered microreactor No. 1 (temperature 140℃, residence time 15 min, pressure 8 bar), connected to the outlet of micromixer No. 1, for a condensation reaction to obtain the first oil-water mixture.

[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 are transported to microreactor No. 2 (temperature of 120℃, residence time of 10 min, and pressure of 8 bar) by a pump and reacted to obtain the 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 are pumped to microreactor No. 3 (temperature of 120℃, residence time of 7 min, and pressure of 8 bar) for reaction to obtain the third oil-water mixture.

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

[0172] The conversion rate of methyl phenylcarbamate was 96.4%, and the selectivity of methyl 4,4'-diphenylmethanedicarbamate was 74.1%.

[0173] Comparative Example 3

[0174] The difference compared to Example 1 is that this comparative example did not use microreactor No. 3.

[0175] Mix 0.5865g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution A; mix 360g of o-dichlorobenzene and 28.8g of methyl phenylcarbamate to form solution B; and mix 0.1173g of paraformaldehyde and 56.25g of 20wt% hydrochloric acid to form solution C.

[0176] Liquid A (flow rate 0.53 mL / min) and liquid B (flow rate 0.47 mL / min) were pumped into micromixer No. 1 (temperature 30℃, mixing time 2 s) for mixing, wherein the molar ratio of methyl phenylcarbamate to formaldehyde was 2:1. The mixture then entered microreactor No. 1 (temperature 140℃, residence time 15 min, pressure 8 bar), connected to the outlet of micromixer No. 1, for a condensation reaction to obtain the first oil-water mixture.

[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 are transported to microreactor No. 2 (temperature of 120℃, residence time of 17 min, and pressure of 8 bar) by a pump and reacted to obtain the second oil-water mixture.

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

[0179] The crude oil phase product was processed by a washing separator for 20 minutes to obtain the oil phase product.

[0180] The conversion rate of methyl phenylcarbamate was 95.3%, and the selectivity of methyl 4,4'-diphenylmethanedicarbamate was 62.2%.

[0181] Industrial availability

[0182] The continuous synthesis method of diphenylmethane dicarboxylate of the present invention can be widely used in the industrial synthesis of diphenylmethane dicarboxylate.

Claims

1. A continuous synthesis method for diphenylmethane dicarboxylate, characterized in that, Includes the following steps: a) Feed solution A and feed solution B are fed to a micro mixer for mixing, and then fed into microreactor No. 1 for reaction to obtain a first oil-water mixture; the temperature in the micro mixer is 15~50℃; the temperature in microreactor No. 1 is 130~150℃; b) The first oil-water mixture and the feed liquid C1 are introduced into the No. 2 microreactor and reacted to obtain the second oil-water mixture; the temperature in the No. 2 microreactor is 110~130℃. c) The second oil-water mixture and feed liquid C2 are introduced into microreactor No. 3 and reacted to obtain the third oil-water mixture; the temperature in microreactor No. 3 is 110~130℃. d) The third oil-water mixture is subjected to phase separation treatment using a liquid-liquid membrane separator to obtain the oil phase; e) Post-process the oil phase to obtain the oil phase product; Wherein, both liquid C1 and liquid C2 are derived from liquid C, liquid A and liquid C are aqueous solutions containing inorganic acid catalyst and methylene reagent, and liquid B is methyl phenylcarbamate solution; The content of the methylene methylating agent in feed solution A is 0.1~5wt%, and the content of the methylene methylating agent in feed solution C is 20~40% of the content of the methylene methylating agent in feed solution A; Furthermore, the molar ratio of methyl phenylcarbamate in solution B to the methyleneizing agent in solution A is (1~2.2):

1.

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 methyleneizing agent includes any one of trioxymethane, formaldehyde, and dimethoxymethane.

3. The synthesis method according to claim 1 or 2, characterized in that, The content of the inorganic acid catalyst in feed solution A is 15~40 wt%; The content of methyl phenylcarbamate in solution B is 1~12 wt%; The content of the inorganic acid catalyst in feed solution C is 15~40wt%.

4. The synthesis method according to claim 1 or 2, characterized in that, The volumetric flow rate ratio of liquid A to liquid B is (0.2~2):

1.

5. The synthesis method according to claim 1 or 2, characterized in that, The micro mixer is a microchannel mixer, a membrane dispersion mixer, or a microsieve mixer; Microreactor No. 1, Microreactor No. 2, and Microreactor No. 3 are each independently a coil-type microreactor or a microchannel reactor.

6. The synthesis method according to claim 1 or 2, characterized in that, The mixing time in the micro mixer is 0.1~10s; The residence time in the No. 1 microreactor is 0.1~30 min; The residence time in the No. 2 microreactor is 0.1~30 min; The residence time in the No. 3 microreactor is 0.1~30 min; The pressure in microreactors No. 1, No. 2 and No. 3 is 1~10 bar.

7. The synthesis method according to claim 1 or 2, characterized in that, The post-processing includes water washing and re-phase separation steps.

8. The synthesis method according to claim 1 or 2, characterized in that, The post-processing temperature is below 50℃, and the time is 10~30min.

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