WO2011130907A1

WO2011130907A1 - Preparation of isocyanate by interface phosgenation reaction

Info

Publication number: WO2011130907A1
Application number: PCT/CN2010/071967
Authority: WO
Inventors: 华卫琦; 孙中平; 尚永华; 石滨; 李建峰; 薛永和; 孙辉; 王海影; 王伦鹏
Original assignee: 烟台万华聚氨酯股份有限公司; 宁波万华聚氨酯有限公司
Priority date: 2010-04-21
Filing date: 2010-04-21
Publication date: 2011-10-27

Abstract

A preparation method of isocyanate by interfacial phosgenation reaction is provided, which comprises the following steps: (a) allowing a solution stream of polyamine having the general formula (II) and a liquid stream of phosgene to flow through the respective mixer, then injecting them into a first-stage reactor at a contact angle of 30-180 degree, such that the solution stream of polyamine and the liquid stream of phosgene are contacted and mixed, and performing phosgenation reaction on the interface; (b) adding the obtained phosgenation liquid in a second-stage reactor, continuously performing the phosgenation reaction to obtain phosgenation liquid containing isocyanate; and (c) separating and purifying the phosgenation liquid containing isocyanate to obtain the isocyanate product.

Description

Method for preparing isocyanate by interfacial phosgenation reaction

The present invention relates to a process for the preparation of isocyanates, and more particularly to a process for the preparation of isocyanates by interfacial phosgenation. Background technique

It is well known that amines and phosgene can produce isocyanates, and depending on the type of amine, the reaction is carried out intermittently or continuously in a gas phase or a liquid phase (W. Sie fken, Lieb igs Ann. 562, 75 (1949)). From the literature reports, the preparation of isocyanates by phosgene method mainly adopts two processes of gas phase method and liquid phase method, and they have their own advantages.

The preparation of isocyanates by gas phase method is currently the focus of development. As early as the 1940s, gas phase phosgenation was used to prepare isocyanate channels (Siefken, Anna 1 en 562, 108, 1949). The gas phase reaction process is often carried out in a tubular reactor. The gas phase reaction process is a rapid reaction process that requires a fast mixing rate while avoiding high temperature coking. During the high-temperature gas phase phosgenation reaction, the residence time of the amines and isocyanates at a high temperature of 300-500 ° C is extremely unstable, and decomposition reactions such as removal of NH ₂ and NC 0 groups occur. In the gas phase process, after the high temperature gas phase photochemical process, the processes of thermal reaction, post treatment and separation are still required.

The process of gas phase phosgenation to prepare isocyanate belongs to high temperature phosgenation reaction. Because it is reacted in the gas phase, it has a fast and good mixing, which reduces the influence of hydrogen chloride and reduces the formation of high molecular weight such as by-product urea. However, due to the relatively fast reaction rate, the rate at which hydrogen chloride reacts with the amine to form the hydrochloride is also accelerated. Therefore, the high-temperature phosgenation reaction easily generates a large amount of the hydrochloride substance, resulting in a high impurity content in the product. Also, since the phosgenation reaction is carried out at a high temperature, the material requirements for the required equipment are very high. In view of the limitations of the above-mentioned high-temperature gas phase method in the preparation of isocyanates, the method has not been widely used in the field of phosgene preparation of isocyanates. Only Bayer and Yantai Wanhua have reported related articles, and related products are limited to TDI and parts. ADI products. The preparation of isocyanates by liquid phase phosgene is the most mature process route, including the salt-forming liquid phase method, the direct liquid phase method and the pressurized liquid phase method. Since the phosgenation reaction is a rapid reaction, the effects of mixing and hydrogen chloride are emphasized in the liquid phase reaction. The salt formation method mainly considers the protection of the amine group, and the direct liquid phase method mainly considers the mixing of the amine group and the phosgene.

GB1142628 describes the process of preparing isocyanate by hydrochloride, but when the conversion of hydrochloride is higher than 95%, the required reaction time is long, resulting in a decrease in yield, and the conversion rate of salt formation is less than 30%, then the unreacted HDA is more. Although the reaction time can be shortened, it is easy to react with HDI to form urea impurities.

US5523467 describes the salt-forming phosgenation reaction using esters as a solvent. By adding nitrogen gas during the reaction, HDI and carbamoyl chloride are prevented from forming tar-like substances, the yield of phosgenation reaction is increased, and the reaction time is shortened. It is industrially feasible to gradually make the salt formation reaction. However, due to the increase of nitrogen gas, the operating cost is increased, and the cost per unit product is increased. Compared with other processes, it still has the disadvantages of low yield and low aging.

5 。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。 Likewise, the continuous recycle of the isocyanate to the reaction zone containing the free amine does promote urea formation. The precipitated urea jeopardizes the stable operation of the process.

CN101056847 describes the use of ether as a solvent to form a salt melt with hydrogen chloride to separate hydrogen chloride, increase the yield and efficiency of the reaction. As the solvent, a compound capable of forming a salt melt with hydrogen chloride and reversibly releasing hydrogen chloride therefrom is used. The solvent capable of temporarily forming a salt melt with hydrogen chloride formed in the reaction is an ether and a polyether.

No. 5,136,086 describes the use of carboxylic acid esters as solvents for the reaction of amines with phosgene. A disadvantage of this solution is that the solvent reacts with the isocyanate. In the preparation of isocyanates by reaction of the corresponding amines with phosgene, it is often a requirement to achieve a reduction in the amount of phosgene present in the reaction system; another requirement that is often present in the preparation of polyisocyanates is to reduce side reactions and thus obtain higher Yield and product of interest with improved quality. This document proposes that, under the conditions in which an amine reacts with phosgene, when a solvent capable of temporarily forming a salt melt with the formed hydrogen chloride is used, the space-time yield of the method is increased and the side reaction is remarkably suppressed.

During the phosgenation reaction, the phosgene concentration in the isocyanate-containing actinic liquid is also a Very important influencing factors. CN1163608 describes a process for the preparation of isocyanates using a continuous process at a pressure of from 1 to 30 bar. The higher the concentration of phosgene dissolved in the isocyanate-containing actinic liquid, the corresponding isocyanate can be obtained. Under this process condition, the phosgene concentration around the amine group is increased to a molar ratio of phosgene to amine of 3:1 _4:1.

In summary, during the phosgene process for the preparation of isocyanate, hydrogen chloride has a great influence on the reaction process, which not only leads to a decrease in product quality, but also may lead to an increase in the amine-based hydrochloride solids during the reaction, which in turn leads to reactor blockage. It also leads to an increase in by-products in the isocyanate, and the phosgenation yield decreases. Therefore, it is necessary to control the influence of hydrogen chloride on the reaction process as much as possible during the development of the isocyanate preparation process.

In addition, the phosgenation interfacial reaction has been extensively studied in the preparation of carbonates, such as CN101235136, which describes a method for preparing polycarbonate by interfacial method using an impinging stream reactor. The method can improve the reaction efficiency of phosgene and phenate, shorten the reaction time, reduce the side reaction product, and reduce the energy consumption in the production process. However, the application of phosgenation interfacial reaction in the field of isocyanate has not been seen. Summary of the invention

In order to overcome the above problems in the prior art, it is an object of the present invention to provide a novel method for the preparation of isocyanates by interfacial phosgene.

The invention is based on the following concept: The liquid phase phosgenation reaction process is a reaction of a gas, liquid and solid three-phase system, and the main products are carbamoyl chloride, amine hydrochloride, hydrogen chloride, isocyanate and by-products. According to the process reaction, by-products of isocyanates such as amine hydrochloride are undesired products, but since the phosgenation reaction is a rapid reaction, the reaction of hydrogen chloride with an amine group is also a rapid reaction, thereby producing an amine-based hydrochloric acid. Undesirable products such as salt are inevitable. There have been many patent documents mentioning the control of the hydrogen chloride content in phosgene and the modification of the solvent system to control the formation of the hydrochloride. The present invention provides a new process based on the prior art to rapidly react a stream of light with an amine solution stream, while allowing the generated hydrogen chloride to be quickly removed from the reaction system, thereby minimizing the hydrogen chloride The effect of the photochemical reaction; in addition, the phosgene can also be refluxed to the reactor to continue the phosgenation reaction, and the efficiency should be significantly improved. Interfacial reactions usually refer to chemical reactions between heterogeneous (intermediate media). Various chemical reactions that occur under certain conditions depending on the characteristics of the contact surface and the type, content, state of existence, and nature of various chemical substances on the surface. The two-phase interface has five types: liquid-liquid, solid-liquid, solid-gas, liquid-gas, and solid-solid. The interface phosgenation reaction of the present invention refers to the formation of an interface between an amine and a phosgene liquid stream with the aid of a mixing distributor, and a rapid reaction, which mainly occurs in the amine solution stream, the optical gas stream and the solid product produced in the reaction system. Between the formed interfaces. The method for preparing an isocyanate represented by the general formula (I) by the interface phosgenation reaction provided by the present invention is as follows:

R (NCO) _n ( I )

R (dish ₂ ) _n ( II )

Wherein R is an aliphatic, alicyclic or aromatic hydrocarbon group, and at least two carbon atoms are arranged between any two adjacent (NC0) of the formula (I), and n > 2, the method comprising the following Steps:

(a) The solution stream of the polyamine of the general formula (II) and the liquid stream of phosgene are respectively flowed through the respective mixers, and then injected into the first-stage reactor at a contact angle of 30-180 degrees, so that The solution stream of the amine is contacted and mixed with the liquid stream of phosgene, and phosgenation reaction is carried out at the interface;

(b) the obtained actinic liquid enters the second-stage reactor, and the phosgenation reaction is continued to obtain an isocyanate-containing actinic liquid;

(c) The isocyanate-containing actinic liquid is separated and purified to obtain an isocyanate product. In the method provided by the present invention, it is preferred that R is an aliphatic C2-C50 hydrocarbon group, an alicyclic C2-C50 hydrocarbon group or an aromatic C6-C50 hydrocarbon group, and further preferably R is an aliphatic C4-C30 hydrocarbon group, an alicyclic C4- The C30 hydrocarbon group or the aromatic C6-C30 hydrocarbon group, more preferably R is an aliphatic C5-C18 hydrocarbon group, an alicyclic C5-C18 hydrocarbon group or an aromatic C6-C20 hydrocarbon group.

In the method provided by the present invention, n = 2-4, more preferably n = 2 or 3.

In the process provided by the present invention, the amine starting material used is a majority of reactive amines, and suitable amines contain from 2 to 15 carbon atoms, preferably from 3 to 15 carbon atoms, further preferably from 4 to 13 Aliphatic, alicyclic or aromatic monoamines, diamines, triamines, Tetraamines or pentaamines. For example, suitable aliphatic diamines are 1,4-butanediamine, 1,6-hexanediamine; alicyclic diamines are 1, 4-diaminocyclohexane, phenylamino-3, 3, 5- Trimethyl-5-aminomethylcyclohexane or 4,4,-dicyclohexylmethanediamine, etc.; suitable aliphatic triamines are 1,8-diamino-4-(aminomethyl)octane, Triaminodecane, etc. Among them, the amine raw material used in the present invention is preferably 1,6-hexanediamine, IPDA, H ₁₂ MDA and triaminodecane. Suitable aromatic amines are phenylenediethylenediamine, toluenediamine, diaminobenzene, naphthalenediamine, 2, 4, or 4,4,-diphenylmethanediamine and mixtures of isomers thereof, For example, a mixture of 2, 4-/2, 6-toluenediamine having an isomer ratio of 80/20-65/35 or pure 2,4-toluenediamine.

The solution stream of the polyamine of the present invention is an organic solution of one or more amines or amines; the liquid stream of the phosgene is a pure phosgene liquid or a phosgene solution. In the process of the present invention, the amine and phosgene may be diluted with an inert solvent to form a solution of the amine and a stream of phosgene. The inert solvent is generally selected from the group consisting of: benzene, toluene, xylene, chlorobenzene, decalin, o-dichlorobenzene, p-dichlorobenzene, monochlorobiphenyl, dialkyl terephthalate or phthalic acid One or more of diethyl esters; preferably chlorobenzene or o-dichlorobenzene.

In the process provided by the present invention, the isocyanate prepared may contain 2-15 carbon atoms (excluding carbon atoms in the isocyanate functional group), preferably 3 to 15 carbon atoms, and more preferably 4 to 13 carbon atoms. Aliphatic, alicyclic or aromatic monoisocyanate, diisocyanate, triisocyanate, tetraisocyanate or pentaisocyanate. For example, the aliphatic diisocyanate is: 1, 4-butane diisocyanate or 1,6-hexamethylene diisocyanate; the alicyclic diisocyanate is: 1, 4-cyclohexane diisocyanate, imino-3, 3, 5- Trimethyl-5-methylcyclohexane diisocyanate, 4,4,-dicyclohexylmethane diisocyanate, etc.; aliphatic triisocyanate: 1, 8-diamino-4-octane diisocyanate, trioxane Isocyanate or the like; Among them, hexamethylene diisocyanate, IPDI, H ₁₂ MDI and the like are preferable. The aromatic isocyanates are: phenylenediethylene diisocyanate, toluene diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate, 2, 4, or 4, 4, -diphenylmethane diisocyanate and mixtures of isomers thereof, for example , a mixture of 2, 4-/2, 6-toluene diisocyanate having an isomer ratio of 80/20-65/35 or pure 2,4-toluene diisocyanate. In the method provided by the present invention, the contact angle between the solution flow of the polyamine and the liquid flow of the phosgene refers to the angle between the mixer of the flow of the polyamine solution and the mixer of the phosgene flow, that is, , polyamine The angle between the solution stream and the phosgene stream prior to contact is preferably 45-135 degrees.

In the method provided by the present invention, preferably, a mixing distributor is disposed at a contact interface between the polyamine solution stream and the phosgene liquid stream, and the cross-sectional area of the mixing distributor accounts for about a kettle or a tower reactor. The cross-sectional area is 1/4 to 1/3. The mixing distributor may use a packing distributor, a tray distributor or a tray distributor, for example, a packing distributor, a tray distributor and a tray distributor of Tianda Beiyang Chemical Equipment Co., Ltd. to ensure The mixing reaction is carried out at the interface.

In the method provided by the present invention, the first stage reactor may also be referred to as a mixing reactor, and the second stage reactor may also be referred to as a thermal reactor. Wherein, the mixing reactor may be a tank reactor or a tower reactor commonly used in the art, preferably a tank reactor; further preferably, the mixing reactor (first stage reactor) is in the existing reaction Based on the process requirements of the method provided by the present invention, the internal structure of the reactor is modified as necessary; for the improvement of the specific reactor structure, please refer to the description of the specific embodiment below. The thermal reactor (second stage reactor) is a conventional reactor for preparing isocyanate, which may also be a column or tank reactor, and the thermal reactor may also be a single thermal reactor or two in series. Thermal reactors. The interface phosgenation reaction of the present invention occurs at the liquid-liquid, gas-liquid and gas-solid interfaces, and makes full use of the mixed layer produced when the amine solution stream and the phosgene stream are ejected at high speed by the respective mixers, With the aid of the mixing distributor, it is more conducive to the mixing of the amine solution and the phosgene flow. Since the reaction for preparing isocyanate by phosgenation is a rapid reaction, it can be completed in a short period of time. Therefore, it is selected to carry out the reaction at the interface, and a higher yield of carbamoyl chloride is obtained in the first phosgenation reaction. The interfacial photochemical reaction produces less impurities, and the reaction time is in the range of 10 to 120 seconds, preferably 30 to 60 seconds.

In the method provided by the present invention, the interfacial reaction temperature in the first-stage reactor (mixed reactor) is 60-160 degrees, preferably 80-130 degrees, to ensure that the reaction materials after being sprayed from the mixer are The first step of the phosgenation reaction in the first stage reactor can be carried out quickly and efficiently. One

-4: 1. The actinic liquid obtained by the interface phosgenation reaction enters the subsequent thermal reactor through the overflow port to perform a thermo-optic gasification reaction, and the reaction temperature is 90-150 degrees, preferably 110-130 degrees; In the process of interfacial reaction, the content of hydrogen chloride has been reduced, the content of solid amine hydrochloride is reduced, thereby reducing the thermal reaction residence time, improving the reaction efficiency and product quality; finally, the actin liquid passes through the separation system. An isocyanate product is obtained. Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

First, since the present invention employs an interfacial phosgene method to prepare an isocyanate, the phosgenation reaction time can be shortened, and the phosgenation yield and the quality of the actinic liquid can be improved.

The isocyanate actinic liquid obtained by the photochemical reaction is mainly a solvent, phosgene, hydrogen chloride, carbamoyl chloride, isocyanate, and amine hydrochloride. The content of hydrogen chloride in the actinic liquid obtained by the invention is very low, and due to the release of hydrogen chloride at the interface, the residence time of hydrogen chloride in the liquid phase is very short under the condition of micro-negative pressure, and remains in the liquid phase. Very little, this is very beneficial to the process of phosgenation reaction to prepare isocyanate.

Since the amine hydrochloride reacts with phosgene to obtain an isocyanate at a relatively slow rate, the efficiency of the phosgenation reaction is greatly reduced. As the hydrogen chloride per unit volume decreases, the probability of producing an amine hydrochloride decreases. Therefore, the present invention creates an environment that is detrimental to the residual hydrogen chloride, thereby increasing the efficiency of the phosgenation reaction.

In addition, the choice of reaction temperature is quite important for the phosgenation reaction process. The invention rapidly reacts phosgene with an amine at a higher reaction temperature, thereby reducing the influence of hydrogen chloride on the reaction process, reducing the content of the hydrochloride, improving the efficiency of the photochemical reaction, and finally obtaining better. The reaction effect.

Since the concentration of phosgenation solution is one of the important parameters determining whether the process route has industrial value, the photoissolution of high isocyanate concentration can significantly reduce the use of solvent, improve the space-time efficiency of phosgenation, and increase the overall phosgenation reaction. value. At present, the preparation of isocyanates by gas phase method is the focus of development: The isocyanate concentration of the actinic liquid obtained by the high temperature vapor phase method can reach 50 wt%. the above. However, the isocyanate concentration of the actinic liquid prepared by the salt formation method is 5-15 wt%, and the isocyanate concentration of the actinic liquid prepared by the direct liquid phase method is 15-25 wt. /. The isocyanate concentration of the actinic liquid obtained by the interface phosgenation reaction provided by the present invention can reach 25-40% by weight. Therefore, the method provided by the present invention makes the industrialization value more valuable than the direct liquid phase method. DRAWINGS

1 is a schematic illustration of a preferred embodiment of the method provided by the present invention.

As shown in Figure 1, 1 is a mixer for the amine solution stream, 2 is a phosgene stream mixer, 3 is a mixing distributor, 4 is a baffle, 5 is a condenser, and 6 is a micro-negative system, 7 It is a kettle reactor. Where TG is the thermometer, PG is the pressure gauge and M is the motor (motor). detailed description

The method provided by the present invention will be further described in detail below with reference to the accompanying drawings, but the present invention is not limited thereby.

In the present application, "amine" or "polyamine" or "amine solution" or "polyamine solution" can be used interchangeably because the amine is reacted in the form of a solution.

As shown in Fig. 1, the polyamine solution stream and the phosgene stream are respectively flowed through the respective mixers 1 and 2, and injected into the tank reactor 7 at a contact angle of 30-180 degrees to make the polyamine. The solution stream and the phosgene stream are contacted and mixed with each other at the mixing distributor 3 (at the reaction liquid interface), and phosgenation reaction is carried out at the interface; the obtained actinizing liquid enters the downstream thermal reactor (Fig. It is not shown), the phosgenation reaction is continued to obtain an isocyanate-containing actinic liquid; and the isocyanate-containing actinic liquid is separated and purified to obtain an isocyanate product.

According to a preferred embodiment of the invention, the kettle reactor 7 is provided with a condensing heat exchanger 5 (also called a condenser), and the outlet of the condensing heat exchanger is connected to the micro-negative pressure system 6. Thus, under micro-negative pressure, the hydrogen chloride generated in the interfacial phosgenation reaction can be quickly removed from the reactor to reduce the effect of hydrogen chloride on the reaction. Of course, while the generated hydrogen chloride is withdrawn from the reactor, a portion of the excess phosgene is also withdrawn. Since it is equipped with a condenser, the phosgene is condensed in the condenser and can be returned to the kettle reactor 7 via a return line. In this way, not only the volatilization of the phosgene is avoided, but also the phosgenation reaction can be further carried out after the phosgene is refluxed, thereby improving the efficiency of the reaction. The micro-negative pressure system is capable of generating a negative pressure that facilitates the extraction of gas from the condenser, typically from -5 to -30 KPa.

According to another preferred embodiment of the present invention, in order to improve the reflux effect of phosgene, in addition to the above-mentioned condenser, micro-negative pressure system and necessary process lines and accessories, it is preferable to One or more baffles are disposed below the reflux port of the condenser in the first stage reactor (tank reactor 7), wherein the lowermost baffles are disposed below the liquid level of the interfacial reaction. Specifically, when only one baffle is provided, the baffle is fixed below the condenser return port and below the liquid level; when a plurality of baffles are provided, the plurality of baffles are arranged in parallel with each other , and is substantially parallel to the liquid level of the interface reaction (horizontal setting), and the lowermost baffle is below the liquid surface. An additional baffle in the first stage reactor, which is functionally similar to the tray of the distillation column, and preferably the baffle is provided with a plurality of perforations so that the hydrogen chloride in the condensed reflux phosgene is completely volatilized. At the same time, the phosgene that is refluxed can enter the phosgenation reaction process, so that the phosgenation reaction is better.

In the present invention, the cross-sectional shape of the baffle is circular, triangular, rectangular, rhombic, trapezoidal, equilateral, non-equilateral, elliptical or the like, preferably circular, triangular or rectangular. The baffle is positioned directly below the condensate outlet of the condenser to ensure that the condensate from the condenser does not fall directly onto the level of the first stage reactor, but instead falls on the baffle. The cross-sectional area of the major surface of the baffle (including the open area) is approximately 5-15% of the cross-sectional area of the first stage reactor. In each baffle, 5-2 QQ openings are usually provided, preferably 10-15 Q openings.

In the present invention, the hydrogen chloride obtained by the heat exchange condenser can be used to prepare industrial hydrochloric acid by an absorption method, or the obtained hydrogen chloride can be oxidized to prepare chlorine gas, for example, by electrolytic oxidation, thereby realizing a cycle of hydrogen chloride separated during the reaction. use. The hydrogen chloride obtained by the present invention does not affect the quality of the later product.

The method for preparing an isocyanate by the interface phosgenation reaction provided by the present invention is mainly carried out in two stages. In the first stage of the phosgenation reaction, the amine is reacted with phosgene to give the corresponding carbamoyl chloride, hydrogen chloride and amine hydrochloride. The reaction between amine and phosgene is very rapid and is strongly exothermic. In order to minimize the formation of by-products and solids, the amine and phosgene must be rapidly mixed under solvent mixing conditions such that the first phosgenation stage typically requires the use of a mixer, which is typically a nozzle. The material amine and phosgene enter the reactor through the mixer outlet for phosgenation. The preferred mixers are tubular, venturi, annular annulus nozzles, micromixers, etc., which are reported in the patent literature for the preparation of isocyanates by phosgene. The invention adopts such a mixer, which is beneficial to the better mixing reaction of phosgene with amine, and is favorable for the phosgenation reaction process.

In the method provided by the present invention, the phosgene liquid stream is 3-30 m/s, preferably 8-18 m/s. The flow rate is from the phosgene flow mixer outlet to the first stage reactor; at the same time, the amine solution stream is passed from the amine solution stream mixer outlet at a flow rate of 3-30 m/s, preferably 8-18 m/s. In the first stage of the reactor, the light gas stream and the amine fluid have a very fast shear rate, ensuring the progress of the phosgenation reaction.

In addition to the mixers already mentioned above which can be used in the present invention, the novel mixers already disclosed in the prior art can also be used in the present invention: dynamic mixers, such as agitators, turbines or rotor-specific subsystems; static mixers For example, a Kenic mixer, a Schaschl i mixer or an SMV mixer; a jet mixer such as a nozzle or a T mixer. Further, the mixer usable in the present invention further includes: a nozzle such as an annular slit nozzle, an annular die nozzle, a smooth jet mixing nozzle, a blast jet nozzle, an angular spray chamber nozzle, a triple flow nozzle, a counter current mixing chamber, Pi tot nozzles and mixing nozzles; in-line mixers, centrifugal mixing pumps, tubular reactors or microstructure mixers, etc. The shape of the outlet of the above mixer may be circular, triangular, elliptical, quadrangular, rectangular, rhomboid or the like, preferably elliptical or rectangular.

The invention is illustrated in more detail below by the examples, but the following examples are not to be construed as limiting the invention.

Example 1

Each of Examples 1-3 employs a kettle reactor as a first-stage reactor equipped with a condenser, and a micro-negative pressure system connected to the condenser (selecting a micro-negative pressure of -1 Okpa) and mounting therein a baffle with 30 perforations below the phosgene condensate return port in the reactor (the area of which is about 7% of the cross-sectional area of the reactor), and three layers of baffles are installed in parallel, the lowest layer of which is below the liquid level. The second stage reactor employed was a conventional tank reactor.

The concentration was prepared at 30 wt ° /. a toluene diamine solution consisting of 70% by weight of o-dichlorobenzene and 30% by weight of toluenediamine; a flow rate of 100 kg/h of toluene diamine solution at a rate of 12 m/s and a phosgene of 95 kg/h The streams were passed through the outlets of the respective tube mixers at a rate of 12 m/sec into the kettle reactor. In the reactor, the two streams are contacted and mixed at a high speed at a contact angle of 90 degrees, and an interfacial reaction occurs at a reaction temperature of about 90 degrees, and the reaction time is 40 seconds; after passing through the reactor , obtained with a certain toluene diisocyanate The actinic liquid of the concentration, which enters the thermal reactor at 120 ° C through the overflow port to complete the reaction of isocyanate; and then purified by a separation system to obtain pure toluene diisocyanate.

By monitoring and analysis of the reaction process, it was found that the content of the hydrochloride in the actinic liquid was 3. 2 wt%, the content of carbamoyl chloride was 85. 3 wt%, and the content of toluene diisocyanate was 11. 5 wt. 9%。 The yield of toluene diisocyanate was 97.9%, the yield of toluene diisocyanate was 97.9%. Example 2

In this example, the formulated concentration was 20 wt ° /. a toluene diamine solution consisting of 80% by weight of o-dichlorobenzene and 20% by weight of toluenediamine; a flow rate of 100 kg/h of toluene diamine solution at a rate of 12 m/s and a flow rate of 64 kg/h of phosgene The liquid stream enters the tank reactor via the outlet of the respective nozzle mixer at a speed of 10 m/sec, in which the two streams are contacted and mixed at a high speed at a contact angle of 70 degrees. Then, the interface phosgenation reaction is carried out under the condition of a reaction temperature of about 70 degrees, and the reaction time is 42 seconds. After the reactor, an actinic liquid having a certain isocyanate concentration is obtained; the actinic liquid enters through the overflow port. The reaction of the isocyanate is carried out in a thermal reactor having a reaction temperature of 120 degrees; and then purified by a separation system to obtain a pure toluene diisocyanate.

5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Wt°/. 4%。 The yield of toluene diisocyanate was 98.4%. The yield of toluene diisocyanate was 98. 4%. Example 3

In this example, the formulated concentration was 18 wt ° /. a hexamethylenediamine solution consisting of 82% by weight of o-dichlorobenzene and 18% by weight of hexamethylenediamine, a flow rate of 100 kg/h of hexamethylenediamine solution at a speed of 14 m/s and a phosgene of 80 kg/h. The flow enters the kettle reactor via the outlet of the respective nozzle mixer at a rate of 13.6 m/sec, in which the two streams are contacted and mixed at a high speed at a contact angle of 90 degrees. The interface phosgenation reaction occurred under the condition of a reaction temperature of 80 degrees, and the reaction time was 40 seconds. After the reactor, it was obtained. An actinic solution of isocyanate concentration; the actinic liquid enters into a thermal reactor having a reaction temperature of 130 degrees via an overflow port to continue and complete the reaction; and then purified by a separation system to obtain pure hexamethylene diisocyanate.

By monitoring and analysis of the reaction process, it was found that the content of the hydrochloride in the actinic liquid was 12.3 wt%, the content of carbamoyl chloride was 84.9% by weight, and the content of hexamethylene diisocyanate was 2. 8 wt. 7%。 The yield of the hexamethylene diisocyanate was 96.7%. Comparative example 1

This comparative example was prepared by a conventional kettle phosgene method. A toluene diamine solution having a concentration of 30% by weight was prepared, consisting of 70% by weight of o-dichlorobenzene and 30% by weight of toluenediamine, and a flow rate of 100 kg/h of toluene diamine solution at a rate of 12 m/s and 95 kg/ The phosgene stream of h enters the tank reactor at a rate of 12 m/s for mixing and phosgenation, and an actinic liquid having a certain isocyanate concentration is obtained, and the actinic liquid continuously enters a reaction temperature of 100. The degree of reaction with the 120 degree two-stage thermal reactor completes the isocyanate reaction and is then purified by a separation system to obtain a pure toluene diisocyanate.

Through monitoring and analysis of the reaction process, it is known that in the phosgene gasification reaction, the viscosity of the actinic liquid is very large, and it needs to be cleaned to continue the reaction; in the actinic liquid obtained by the cold phosgenation reaction, the hydrochloride content is 50. 4wt%。 The content of the toluene diisocyanate is 4. 4wt. /. 8%。 The yield of toluene diisocyanate was only 91.8%. The yield of the obtained toluene diisocyanate was only 91.8%. Comparative example 2

This comparative example was prepared by a conventional kettle phosgene method. A toluene diamine solution having a concentration of 20% by weight was prepared, consisting of 80% by weight of o-dichlorobenzene and 20% by weight of toluenediamine, and a flow rate of 100 kg/h of toluene diamine solution at a rate of 12 m/s and 64 kg/ The phosgene stream of h enters the tank reactor at a rate of 10 m/s for mixing and phosgenation, and an actinic liquid having a certain isocyanate concentration is obtained, and the actin liquid continuously enters the reaction temperature respectively. In a two-stage thermal reactor of 100 degrees and 120 degrees, after the isocyanate reaction is continued and completed, the actinic liquid is purified by a separation system to obtain a pure toluene diisocyanate.

The octadecyl chloride content is 2.71wt%, the toluene diisocyanate content is 2. 71wt% / the content of the carbamoyl chloride is 4. . The yield of the toluene diisocyanate was 93. 4%. The yield of the toluene diisocyanate was 93. 4%.

Claims

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A method for producing an isocyanate represented by the formula (I) by an interfacial phosgenation reaction,

R (NCO) _n ( I )

R (NH ₂ ) _n ( ID

(b) the obtained actinic liquid enters the second-stage reactor, and the photochemical reaction is continued to obtain an isocyanate-containing actinic liquid;

(c) The isocyanate-containing actinic liquid is separated and purified to obtain an isocyanate product.

2. The method according to claim 1, wherein: the solution flow of the polyamine and the phosgene flow are passed through respective mixers, and the first-stage reaction is injected at a contact angle of 45-135 degrees. Device.

3. The method according to claim 2, wherein: the mixed-distributor is disposed at a horizontal section of the polyamine solution stream in contact with the phosgene stream; preferably, the mixing distributor is a filler distributor, Tray distributor or tray distributor.

4. The method according to any one of claims 1 to 3, wherein: the first stage reactor and the second stage reactor are a tank reactor or a tower reactor; The reactor is preferably a kettle reactor which has been modified as follows: The kettle reactor is equipped with a condensing heat exchanger, and the outlet of the condensing heat exchanger is connected to a micro-negative pressure system.

5. A method according to claim 4 wherein: one or more baffles are disposed below the reflux port of the condensing heat exchanger in the kettle reactor.

6. The method according to claim 5, wherein: when a baffle is provided, the baffle is fixed below the return port of the condenser and is located below the liquid level of the interface reaction; When the plate is flown, the plurality of baffles are horizontally disposed parallel to each other and substantially parallel to the liquid level of the interface reaction, and the lowermost baffle is below the liquid level of the interface reaction.

7. The method according to claim 6, wherein: the baffle has a cross-sectional shape of a circle, a triangle, a rectangle, a diamond, a trapezoid, an equilateral polygon, a non-equilateral polygon or an ellipse, preferably a circular shape. , triangular or rectangular; the cross-sectional area of the main surface of the baffle occupies 5-15% of the cross-sectional area of the first-stage reactor; each of the baffles has 5-200 openings, preferably 10-150 Open holes.

8. A method according to claim 1 or claim 7 wherein: the hydrogen chloride formed in the interfacial phosgenation reaction and a portion of the excess phosgene are rapidly removed from the first stage reactor by micro-negative pressure. After picking up, the phosgene is condensed by condensation through a condensing heat exchanger and returned to the first stage reactor via a condensing reflux line.

9. The method of claim 8 wherein: the phosgene stream returned to the first stage reactor via the condensing return line is dripped onto the one or more open-ended baffles to cause reflux phosgene The hydrogen chloride entrained in the stream is completely volatilized.

The method according to claim 1 or 9, wherein the reaction time of the solution flow of the first-stage reactor polyamine with the liquid flow interface of the phosgene is 10 to 120 seconds, preferably 30 to 60 seconds; The reaction temperature is from 60 to 160 degrees, preferably from 80 to 130 degrees; and the reaction temperature in the second-stage reactor is from 90 to 150 degrees, preferably from 110 to 130 degrees.

11. A method according to claim 1 or claim 7 wherein: the mixer of the polyamine solution stream and the phosgene stream are selected from the group consisting of: a tube mixer, a venturi mixer, an annulus mixing , nozzle or micro-mixer; and the shape of the mixer outlet is circular, triangular, elliptical, quadrangular, rectangular or diamond-shaped, preferably elliptical or rectangular.

12. The method according to claim 1, wherein: the phosgene stream is injected into the first stage reactor from the mixer outlet at a flow rate of 3-30 m/s, preferably 8-18 m/s; The amine solution stream is injected into the first stage reactor from the mixer outlet at a flow rate of from 3 to 30 m/s, preferably from 8 to 18 m/s.

13. The method according to claim 1, wherein the molar ratio of phosgene to amine in the actinic liquid after the interface phosgenation reaction is 3:1 to 4:1.

14. The method according to claim 1, wherein: the amine is selected from any one of the following compounds: 1, 4-butanediamine, 1,6-hexanediamine, 1,4-diamine Cyclohexane, amino- 3,3,5-trimethyl-5-aminomethylcyclohexane, 4,4,-dicyclohexylmethanediamine, triammonium a mixture of 2,4-/2,6-toluenediamine having a ratio of isomers of 80/20 to 65/35 or pure 2,4-toluenediamine, 4,4,-diaminodicyclohexyl Methane diamine.

15. The method according to claim 1, wherein the isocyanate is selected from any one of the following compounds: 1, 4-butyl diisocyanate, 1,6-hexamethylene diisocyanate, 1, 4-diisocyanate Cyclohexane, isophorone diisocyanate, 4,4,-dicyclohexylmethane diisocyanate, triisocyanate decane, toluene diisocyanate, 4,4,-diaminodicyclohexylmethane diisocyanate.

16. The method according to claim 1, wherein: the solution stream of the polyamine and the liquid stream of phosgene are the same solvent, and the solvent is selected from the group consisting of: toluene, xylene, chlorobenzene, o-dichlorobenzene or ten One or more of hydrogenated naphthalenes; preferably chlorobenzene or o-dichlorobenzene.