阅读说明：本技术 一种连续光气化法制备异氰酸酯的方法 (Method for preparing isocyanate by continuous phosgenation method ) 是由 陈浩 尚永华 李建峰 朱付林 史培猛 吴谦 石滨 黎源 于 2020-06-24 设计创作，主要内容包括：本发明公开了一种连续光气化法制备异氰酸酯的方法,包括如下步骤：1)将反应原料的溶液部分和光气加入第一光化反应装置中进行反应,得到一级光化反应液；2)将所述一级光化反应液和光气加入第二光化反应装置中进行进一步反应,得到二级光化反应液；3)将所述二级光化反应液分离得到不含固体物质的反应液以及含固体物质的反应液,所述不含固体物质的反应液进入下一级工序,含固体物质的反应液经破碎分散后返回至第一光化反应装置中。本发明能够缩短反应时间、减少轻组分和高聚物生成,并且能够对固体物质,尤其是大颗粒抱团的盐酸盐进行乳化分散后再光化,减少反应残渣,提高了生产效率。(The invention discloses a method for preparing isocyanate by a continuous phosgenation method, which comprises the following steps: 1) adding a solution part of reaction raw materials and phosgene into a first photochemical reaction device for reaction to obtain a primary photochemical reaction liquid; 2) adding the primary photochemical reaction liquid and phosgene into a second photochemical reaction device for further reaction to obtain a secondary photochemical reaction liquid; 3) and separating the secondary photochemical reaction liquid to obtain a reaction liquid without solid matters and a reaction liquid with solid matters, wherein the reaction liquid without solid matters enters the next stage, and the reaction liquid with solid matters is crushed and dispersed and then returns to the first photochemical reaction device. The invention can shorten the reaction time, reduce the generation of light components and high polymers, emulsify and disperse solid substances, particularly large-particle cohesive hydrochloride, and then photochemically treat the solid substances, reduce reaction residues and improve the production efficiency.)

1. A method for preparing isocyanate by a continuous phosgenation method is characterized in that: the method comprises the following steps:

1) adding a solution part of reaction raw materials and phosgene into a first photochemical reaction device for reaction to obtain a primary photochemical reaction liquid;

2) adding the primary photochemical reaction liquid and phosgene into a second photochemical reaction device for further reaction to obtain a secondary photochemical reaction liquid;

3) and separating the secondary photochemical reaction liquid to obtain a reaction liquid without solid matters and a reaction liquid with solid matters, wherein the reaction liquid without solid matters enters the next stage, and the reaction liquid with solid matters is crushed and dispersed and then returns to the first photochemical reaction device.

2. The continuous phosgenation process of claim 1, wherein the isocyanate is prepared by: the solution part of the reaction raw material is the solution of amine salt and acyl chloride substances; the isocyanate is selected from one or more of aliphatic, alicyclic and aromatic diisocyanates, preferably aromatic diisocyanate with high heat sensitivity, and further preferably one or more of toluene diisocyanate, p-phenylene diisocyanate, 1, 5-naphthalene diisocyanate, diphenylmethane diisocyanate and m-xylylene diisocyanate.

3. The continuous phosgenation process of claim 1, wherein the isocyanate is prepared by: the secondary photochemical reaction liquid can also be separated to obtain phosgene and hydrogen chloride gas.

4. The continuous phosgenation process of claim 1, wherein the isocyanate is prepared by: controlling the proportion of the generated amount of isocyanate in the reaction liquid obtained by the first photochemical reaction device in the step 1) to the theoretical generated amount to be 80-90 wt%, and controlling the proportion of the generated amount of isocyanate in the reaction liquid obtained by the second photochemical reaction device in the step 2) to the theoretical generated amount to be 95-99 wt%;

preferably, the isocyanate concentration is from 5 to 30% by weight, preferably from 10 to 20% based on the total mass of solvent and isocyanate;

preferably, the reaction temperature of the phosgenation process in the first photochemical reaction device and the second photochemical reaction device is 120-170 ℃, preferably 130-140 ℃;

preferably, the reaction pressure of the phosgenation process in the first photochemical reaction device and the second photochemical reaction device is 0 to 0.5MPa, preferably 0.1 to 0.3 MPa.

5. A separation emulsifier for use in the method of any one of claims 1-4, characterized by: it includes: a separation chamber, a filtrate chamber surrounding the separation chamber, and an emulsification chamber below the separation chamber; the separation cavity is provided with a feed inlet and an air outlet, the filtrate cavity is provided with a filtrate discharge port, and the emulsification cavity is provided with an emulsification cavity liquid outlet; and adding the secondary photochemical reaction liquid into a separation emulsifier through the feed inlet, wherein the liquid at the liquid outlet of the emulsifying cavity is communicated with the first photochemical device, and the filtrate at the filtrate outlet is connected to the next stage of working procedure.

6. The separation emulsifier of claim 5, wherein: the feed inlet and the gas outlet are positioned at the top of the separation cavity, the filtrate discharge hole is positioned at the bottom of the filtrate cavity, and the liquid outlet of the emulsification cavity is positioned at the bottom of the emulsification cavity.

7. The separation emulsifier as claimed in claim 5 or 6, wherein: the separation emulsifier also comprises a filter layer, a filter residue scraper blade, a fixed rod, a fixed disk, a vortex wheel, a static gear and a moving gear; the filter layer is arranged at the periphery of the separation cavity, namely the filter layer is arranged between the separation cavity and the filtrate cavity; the filter residue scraper blade is fixed on the fixed rod in the separation cavity, and the fixed rod is connected on the fixed disk and rotates along with the fixed disk.

8. The separation emulsifier of claim 7, wherein: the separation cavity comprises a metal cylinder with a porous structure, the outer surface of the metal cylinder is provided with a filter medium which is used as the filter layer, and the pore diameter selection range of the filter medium is as follows: 50-300 meshes, and the material is selected from one or more of porous ceramics, metal woven mesh, sintered mesh, fiber filter cloth and filter membrane, preferably metal woven mesh and/or sintered mesh.

9. The separating emulsifier of claim 7 or 8, wherein: the filter residue scrapers are fixed on fixing rods of the separation cavity, preferably 3 fixing rods are uniformly distributed in the separation cavity; each fixing rod fixes a plurality of residue scraping plates at equal intervals from top to bottom, preferably 4; the filter residue scrapers among the fixed rods are distributed in a staggered manner, the filter residue scrapers have a certain downward inclination along the rotating direction, the selected inclination angle of the filter residue scrapers is 5-30 degrees, the distance between the tips of the filter residue scrapers and the surface of the filter medium is 0.2-2mm, and the preferred distance is 0.5-1 mm; the fixed rod rotates along with the fixed disk, the rotating speed is 10-100r/min, preferably 30-50r/min, and the fixed rod rotates in the same direction with the vortex wheel.

10. The separating emulsifier of claim 7 or 9, wherein: the vortex wheel is positioned at the junction of a cylindrical cavity and an inverted conical cavity in the separation cavity and comprises an impeller, a bottom disc and a central fixed shaft, twelve impellers are preferably and uniformly distributed, the ratio of the diameter of the vortex wheel to the inner diameter of the separation cavity is 1:30-1:3, the rotating speed of the vortex wheel is 50-500r/min, preferably, the separation emulsifier further comprises a liquid level meter which is arranged in the separation cavity, and the liquid level of the separation cavity is preferably 30-70% of the total volume of the separation cavity; the diameter ratio of the upper end opening to the lower end opening of the inverted cone-shaped cavity in the separation cavity is 10:1-2: 1; the emulsification cavity is a crushing cavity for accommodating solid particles, and a static gear and a moving gear are arranged in the emulsification cavity, and preferably three groups of emulsification cavities are provided;

preferably, the ratio of the flow of the liquid stream at the liquid outlet of the emulsifying cavity to the flow of the filtrate at the filtrate outlet is 1:9-1: 19;

preferably, the ratio of the inner diameters of the gas phase pipe for the gas outlet, the discharge pipe for the filtrate discharge port and the feed pipe for the separation cavity feed port is 5-10:1.5-3: 1;

preferably, the volume ratio of the cavities of the separation cavity, the filtrate cavity and the emulsification cavity is 1:1:0.1-1:2: 0.5;

preferably, the average residence time of the secondary photochemical reaction liquid in the separating emulsifier is 2-15 min.

Technical Field

The invention relates to the field of isocyanate preparation, in particular to a method for preparing isocyanate by a continuous phosgenation method.

Background

The preparation of isocyanates by reacting primary organic amines with phosgene in inert solvents is well known in the prior art. The phosgene method is mainly divided into a direct method and a salt forming method, wherein the direct method is to directly react primary amine with phosgene to prepare isocyanate; the salt-forming method comprises reacting the corresponding amine with an acidic gas such as hydrogen chloride, carbon dioxide, etc. to obtain amine hydrochloride or carbonate, and then reacting the amine salt with phosgene to prepare isocyanate. Both methods have certain defects, and the direct method is easy to cause amine coating due to high reaction speed to generate urea byproducts in the subsequent thermochemical process; the salt formation method has the disadvantages that the system viscosity is high due to the formation of stable hydrochloride firstly, the mixing effect is influenced, and the reaction time of the thermal photochemical process is long, so that the reaction concentration is limited and the polymer content is increased.

Chinese published patent CN200680022170 reports that the salt formation process is carried out at 120 ℃ and 0.01Mpa higher than atmospheric pressure, although high-temperature pressurization can reduce the viscosity of the hydrochloride and improve the conversion rate of the salt formation and the space-time efficiency, there are two defects, on one hand, the diamine is only suitable for diamine with higher stability at high temperature, and the color numbers of the salt formation and the photochemical solution are seriously affected; on the other hand, the salt formation rate is extremely high at high temperature, and the problems of heat transfer of a reaction kettle and coating of diamine are considered.

In chinese patent CN102070491B, a spray reactor is disposed in a salt-forming reaction kettle, amine is dissolved in an inert organic solvent to prepare an amine feed solution, and the amine feed solution enters a liquid-phase nozzle of the reactor; the hydrogen chloride gas enters a gas-phase nozzle of the reactor, and the hydrogen chloride gas and the gas-phase nozzle are quickly mixed and enter a salifying reaction kettle. The process requires that the hydrochloride concentration be run at a lower level in order to solve the plugging problem and enhance mixing. Resulting in higher overall energy consumption and difficult solution to the problem of nozzle blockage.

Chinese patent publication CN105126711A discloses a stirring and grinding reactor used in the salt-forming reaction process, the reactor is provided with a movable rotating plate and a stationary rotating plate which are sheared with each other, and the rotating plate is provided with a channel hole, thereby avoiding the agglomeration of hydrochloride and making the hydrochloride particles finer and finer. Although the method can obtain hydrochloride with better dispersibility, the pore channels on the rotating sheet are easy to block and may not achieve ideal effect, and the energy consumption of the whole equipment is higher.

At present, in the existing salt-forming phosgene method, the common characteristics of incomplete salt formation in salt formation, more side reactions in the photochemical process, capability of only processing hydrochloride with lower concentration and the like exist, so that a novel method for preparing isocyanate by using liquid phase phosgenation of salt formation needs to be developed to solve the problems of difficult dispersion of hydrochloride agglomeration, low production efficiency and the like.

Disclosure of Invention

The invention provides a method for preparing isocyanate by a continuous phosgenation method, which can make up the defects of the prior art, shorten the reaction time, reduce the generation of light components and high polymers, emulsify and disperse solid substances, particularly large-particle cohesive hydrochloride, and then carry out photochemical reaction, reduce reaction residues and improve the production efficiency.

In order to achieve the purpose, the invention adopts the following technical scheme: a method for preparing isocyanate by a continuous phosgenation method comprises the following steps:

1) adding a solution part of reaction raw materials and phosgene into a first photochemical reaction device for reaction to obtain a primary photochemical reaction liquid;

2) adding the primary photochemical reaction liquid and phosgene into a second photochemical reaction device for further reaction to obtain a secondary photochemical reaction liquid;

3) and separating the secondary photochemical reaction liquid to obtain a reaction liquid without solid matters and a reaction liquid with solid matters, wherein the reaction liquid without solid matters enters the next stage, and the reaction liquid with solid matters is crushed and dispersed and then returns to the first photochemical reaction device.

In the method of the present invention, the solution of the above reaction raw materials is partially a solution of organic primary amine raw materials for preparing isocyanate, such as a solution of amine salt and acid chloride. The secondary photochemical reaction liquid is separated to obtain most of the reaction liquid without solid matter and a small amount of reaction liquid with solid matter, wherein the solid matter refers to unreacted solid amine salt and solid acid chloride substances, and is usually large particle solid matter which is not easy to react. Preferably, the reaction solution without solid matter is filtered and then enters the next step, and the next step mainly refers to a separation step, such as desolventizing, rectification and purification, and the like. The secondary photochemical reaction liquid can be separated to obtain gases such as phosgene, hydrogen chloride and the like, and the gases preferably enter an external tail gas system to be subjected to tail gas treatment in a conventional manner.

In the method of the present invention, the photothermal reaction stage is continuously carried out in two stages, and the proportion of the amount of isocyanate formed in the reaction solution obtained in step 1), i.e., the first photochemical reaction apparatus, to the theoretical amount of production is controlled to 80 to 90% by weight, and the proportion of the amount of isocyanate formed in the reaction solution obtained in step 2), i.e., the second photochemical reaction apparatus, to the theoretical amount of production is controlled to 95 to 99% by weight. The invention can be used for sampling and monitoring, the proportion of the reaction is controlled by adjusting the residence time, and the residence time can be realized by controlling the liquid level in the reaction kettle.

In the process of the invention, the isocyanate concentration is calculated as the theoretically generated mass of isocyanate in the photochemical process relative to the total mass (mass percentage) of solvent and isocyanate. In the embodiment of the present invention, the isocyanate concentration is 5 to 30%, preferably 10 to 20%, and higher production efficiency can be obtained.

In the process of the present invention, the isocyanate is selected from one or more of aliphatic, cycloaliphatic and aromatic diisocyanates, preferably an aromatic diisocyanate with a relatively high heat sensitivity, such as: toluene diisocyanate, p-phenylene diisocyanate, 1, 5-naphthalene diisocyanate, diphenylmethane diisocyanate, m-xylylene diisocyanate, and the like.

In the method according to the invention, the reaction temperature of the phosgenation process in the first photochemical reaction device and the second photochemical reaction device is 120-170 ℃, preferably 130-140 ℃. If the photochemical reaction temperature is higher than 170 ℃ for a long time, the thermal stability of the product isocyanate is poor, so that the polymerization is caused, the tar content is increased, the improvement of the product yield is not facilitated, and the generation of certain substituted impurities (such as monochloride, monobromide, or the product of the monochloride, monobromide and aromatic solvent through Friedel-crafts alkylation) can be caused due to the temperature rise; while the temperature is lower than 120 ℃, the reaction speed of the diamine hydrochloride and the phosgene becomes slow, and impurities containing hydrochloride are generated.

In the method according to the present invention, the reaction pressure (gauge pressure) of the phosgenation process in the first photochemical reaction apparatus and the second photochemical reaction apparatus is 0 to 0.5MPa, preferably 0.1 to 0.3 MPa. The pressurized photochemical reaction under the pressure is favorable for improving the concentration of phosgene in a solvent, increasing the contact amount of diamine hydrochloride and phosgene, accelerating the reaction rate and shortening the reaction time. When the reaction pressure exceeds 0.5MPa, on one hand, the risk is high, and on the other hand, the high concentration HCl generated in the reaction can inhibit the reaction and is not beneficial to the reaction.

In the method according to the present invention, the solvent in the phosgenation process of the first and second photochemical reaction apparatuses is one or more selected from aromatic hydrocarbon solvents and carboxylic ester solvents having boiling points of 120-170 ℃ at normal pressure. The solvent shows reaction inertia in the reaction system of the invention, and does not react with raw materials, products and the like, and the density of the solvent is smaller than that of solid amine salt or acyl chloride, so that solid substances can be rapidly settled in the solvent. In a preferred embodiment of the present invention, the solvent is selected from one or more aromatic hydrocarbon solvents. The aromatic hydrocarbon solvent includes, but is not limited to, one or more of benzene, toluene, xylene, ethylbenzene, cumene, butylbenzene, cyclohexylbenzene, tetrahydronaphthalene, chlorobenzene, o-dichlorobenzene, methylnaphthalene, biphenyl, and triphenylmethane, preferably one or more of chlorobenzene, o-dichlorobenzene, butylbenzene, o-xylene, and cumene. The carboxylic ester solvent includes, but is not limited to, one or more of ethyl acetate, butyl acetate, amyl acetate, methyl salicylate, dimethyl phthalate, dibutyl phthalate, and methyl benzoate. Preferably, the solvent is selected from one or more of the aromatic hydrocarbon solvents.

The method of the invention is not only limited to the liquid phase salt formation method, but also is applicable to the cold-hot phosgenation method. That is, the reaction solution produced in the cold and hot phosgenation reaction stages was operated in accordance with steps 1), 2) and 3).

The method shortens the reaction time by controlling the conditions in the isocyanate preparation process, namely reducing the average heating time of the isocyanate in the photochemical thermal reaction stage, and particularly by carrying out sectional treatment on the reaction liquid, is beneficial to reducing the generation of light component impurities and heavy component impurities, thereby improving the quality and the reaction yield of the product.

The invention provides a separating emulsifier in a second aspect, which is a gas-liquid-solid three-phase separating emulsifier, comprising: a separation chamber, a filtrate chamber surrounding the separation chamber, and an emulsification chamber below the separation chamber; the separation cavity is provided with a feed inlet and an air outlet, the filtrate cavity is provided with a filtrate discharge port, and the emulsification cavity is provided with an emulsification cavity liquid outlet; and the secondary photochemical reaction liquid is added into the separation emulsifier through the feed inlet, the liquid at the liquid outlet of the emulsifying cavity is communicated with the first photochemical device, and the filtrate at the filtrate outlet is connected to the next stage of working procedure.

In the separating emulsifier of the present invention, preferably, the feed inlet and the gas outlet are located at the top of the separation chamber, the filtrate discharge outlet is located at the bottom of the filtrate chamber, and the liquid outlet of the emulsification chamber is located at the bottom of the emulsification chamber.

In the invention, the separation emulsifier also comprises a filter layer, a filter residue scraper blade, a fixed rod, a fixed disk, a vortex wheel, a static gear and a moving gear; the filter layer is arranged at the periphery of the separation cavity, namely the filter layer is arranged between the separation cavity and the filtrate cavity; the filter residue scraper blade is fixed on the fixed rod in the separation cavity, and the fixed rod is connected on the fixed disk and rotates along with the fixed disk.

In a specific embodiment, the separation chamber comprises a metal cylinder with a porous structure, and in order to filter out large-particle hydrochloride remained in the photochemical liquid, the outer surface of the metal cylinder can be provided with a filter medium, and the filter medium is used as the filter layer and has the pore size selected from the range of: 50-300 meshes, the material can be one or more of porous ceramics, metal woven mesh, sintered mesh, fiber filter cloth and filter membrane, and the metal woven mesh and/or the sintered mesh are preferred.

In a specific embodiment, the residue scraper is fixed on fixing rods of the separation cavity, preferably 3 fixing rods are uniformly distributed in the separation cavity; each fixing rod fixes a plurality of residue scraping plates at equal intervals from top to bottom, preferably 4; the filter residue scrapers among the fixed rods are distributed in a staggered manner, the filter residue scrapers have a certain downward inclination along the rotating direction, the selected inclination angle of the filter residue scrapers is 5-30 degrees, the distance between the tips of the filter residue scrapers and the surface of the filter medium is 0.2-2mm, and the preferred distance is 0.5-1 mm; the scraper fixing rod rotates along with the fixed disc, the rotating speed is 10-100r/min, preferably 30-50r/min, and the scraper fixing rod rotates in the same direction with the vortex wheel.

In a specific embodiment, the diameter ratio of an upper end opening and a lower end opening of the inverted cone-shaped cavity at the lower part of the separation cavity is 10:1-2:1, which is beneficial to improving the relative content of solid particles entering the emulsification cavity, and the diameter of the upper end opening is the diameter of the cylindrical cavity.

In a specific embodiment, the vortex wheel is located at the junction of a cylindrical cavity and an inverted conical cavity in the separation cavity, and consists of an impeller, a bottom disc and a central fixed shaft, the impeller is preferably uniformly distributed in twelve pieces, the ratio of the diameter of the vortex wheel to the diameter of the inside of the separation cavity is 1:30-1:3, the rotation speed of the vortex wheel is 50-500r/min, the vortex wheel rotates clockwise facing the impeller, the vortex wheel is used for driving photochemical liquid in the separation cavity to rotate at a high speed to generate centrifugal force, and the centrifugal force is adjusted according to the rotation speed of the vortex wheel, so that the purpose of controlling the liquid level of the separation cavity is achieved, preferably, the gas-liquid-solid three-phase separation emulsifier further comprises a liquid level meter which is arranged in the separation cavity, and the liquid level of the separation cavity is preferably 30-70% of the total volume of the separation cavity.

In a specific embodiment, the emulsification chamber is a crushing chamber for accommodating solid particles, a static gear and a moving gear are arranged in the emulsification chamber, preferably three groups of the static gear and the moving gear are arranged in the emulsification chamber, after a reaction solution containing high-concentration solid particles enters the emulsification chamber, the solid particles are crushed by the high-speed rotation of the moving gear, the particle size of the solid particles which can be crushed is 10000um, the particle size of the solid particles after crushing is 10-100um, and the single-pass crushing rate is 50-90%.

In a specific embodiment, the ratio of the flow rate of the liquid stream at the liquid outlet of the emulsification chamber to the flow rate of the filtrate at the filtrate outlet is 1:9-1:19, when the flow rate of the filtrate in the filtrate chamber is reduced, the flow rate of the filtrate can be increased by increasing the rotation speed of the deslagging scraper and the scroll wheel, and the liquid level of the reaction liquid in the separation chamber is reduced.

In the invention, the average residence time of the secondary photochemical reaction liquid in the separation emulsifier is 2-15min, the solid-liquid separation effect is better in the period, and the residence time can be controlled according to the liquid level in the separation cavity, namely the rotating speeds of the vortex wheel and the deslagging scraper are adjusted.

In a specific embodiment, the ratio of the inner diameters of the gas phase pipe for the gas outlet, the discharge pipe for the filtrate discharge port and the feed pipe for the separation cavity feed port is 5-10:1.5-3: 1. The material in the feeding pipe enters the separating emulsifier with pressure, and the separating emulsifier is slightly positive pressure, so the discharging pipe is 2-9 times thicker than the feeding pipe, and the gas phase pipe is designed to be thicker.

In a specific embodiment, the cavity volume ratio of the separation cavity, the filtrate cavity and the emulsification cavity is preferably 1:1:0.1-1:2: 0.5. As more than or equal to 90 percent of reaction liquid directly enters the filtrate cavity and only less than 10 percent of feed liquid containing solids needs to enter the emulsification cavity, the volume of the emulsification cavity is reduced so as to improve the emulsification efficiency.

In the invention, no matter in the photochemical reaction process in the liquid-phase salt forming method or in the thermal phosgenation reaction stage in the cold-hot phosgenation method, the reaction rate is fast in the early stage and slow in the later stage, more than 95% of isocyanate can be generated in a short time, unreacted solid amine salt and acyl chloride substances usually take a great deal of time to react even more than half of the total reaction time, and the process is accompanied with a great amount of monochloro and polymer. Therefore, the reaction liquid obtained by the second photochemical reaction device is treated in a segmented manner, the reaction liquid is added into the separation emulsifier, most of solids are settled in an emulsification cavity of the separation emulsifier and return to the first photochemical reaction device after being crushed and dispersed, clear liquid is filtered by a filter layer in the separation cavity of the separation emulsifier and then is sent to the next stage of working procedure, and phosgene, hydrogen chloride and the like carried in the reaction liquid enter a tail gas system. And controlling the flow ratio of the flow of the stream returning to the first photochemical reaction device to the flow ratio of the filtrate in the separation cavity by using a flow regulating valve of the liquid returning stream, namely controlling the flow ratio of the liquid stream at the liquid outlet of the emulsification cavity to the flow ratio of the filtrate at the filtrate outlet to be 1:9-1:19, wherein the part of reaction liquid containing solid amine salt and acyl chloride contains part of isocyanate, so that the control of the liquid returning with proper proportion is more critical.

In conclusion, the separating emulsifier of the present invention is particularly suitable for use in the process for preparing isocyanates.

Compared with the prior art, the invention has the following advantages:

(1) the method comprises the steps of adding amine salt or acyl chloride substances and phosgene which are reaction raw materials into a two-stage photochemical reaction device for reaction, enabling a small amount of reaction liquid containing solid substances such as unreacted amine salt or solid acyl chloride substances to enter an emulsifying cavity to be crushed, dispersed and returned to a first photochemical reaction device after the reaction liquid passes through a separation emulsifier, enabling most of the reaction liquid containing no solid substances to enter the next stage, and enabling gases such as phosgene, hydrogen chloride and the like to enter a tail gas system. The invention shortens photochemical reaction time, reduces generation of monochloro and polymer, improves product yield, improves productivity by 0.5-2 times compared with the traditional process, and saves production cost

(2) The invention reduces the generation of photochemical reaction residues, particularly cohesive hydrochloride or acyl chloride which is difficult to react in a system, and the substances finally enter a tar system and are treated as solid-liquid waste; meanwhile, the method can refine the large-particle solid matter which is difficult to react to improve the reaction effect, reduce the problems of equipment blockage or pollution and the like caused by residues, and is convenient for large-scale industrial application.

(3) The reaction liquid in the separation emulsifier has high separation efficiency, and most of solid matters can be separated through sedimentation, so that the energy consumption is reduced.

(4) The invention adopts the secondary photochemical reaction device to carry out continuous photochemical reaction, can achieve the effect of multi-stage reaction, saves the equipment investment, and is suitable for large-scale industrial application.

Drawings

FIG. 1 is a flow chart of a continuous photochemical reaction process for preparing isocyanate according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the overall structure of the separation emulsifier according to the embodiment of the present invention;

fig. 3 is a schematic structural view of the scroll wheel in fig. 2.

The labels in FIG. 1 are illustrated as follows: 1-a first photochemical reaction device (photochemical kettle), 2-a second photochemical reaction device (photochemical kettle) and 3-a separating emulsifier.

The labels in FIG. 2 are illustrated as follows: 4-a scraper rotating shaft motor, 5-a feed inlet, 6-a fixed disc, 7-a fixed rod, 8-a scraper, 9-a filter layer, 10-a metal cylinder, 11-a filtrate discharge outlet, 12-a scroll wheel, 13-a static gear, 14-a moving gear, 15-an emulsion cavity liquid outlet, 16-a turbine and gear rotating motor, 17-a liquid level meter, 18-a filtrate cavity, 19-a separation cavity, 20-an emulsion cavity and 21-an air outlet.

The labels in FIG. 3 are illustrated as follows: 22-bottom disc, 23-impeller, 24-central fixed shaft.

Detailed Description

The present invention will be further described with reference to the following examples and the accompanying drawings, but the present invention is not limited to the examples listed, and shall include equivalent modifications and variations of the technical solutions defined in the claims appended to the present application.

GC purity test instrument: agilent, column: DB-5, FID detector, injection port temperature 260 ℃, detector temperature 300 ℃, carrier gas: nitrogen (10mL/min), split ratio 10:1, sample introduction amount: 20 ul;

as shown in fig. 1, the method for preparing isocyanate by continuous photochemical reaction according to the embodiment of the present invention includes: the photochemical kettle 1 and the photochemical kettle 2 are added with a solvent with a certain liquid level for continuous operation, phosgene is introduced, the photochemical kettle 1 and the photochemical kettle 2 are heated, and the required temperature, pressure and average residence time are maintained. Slurry (specifically described in the following embodiment) containing hydrochloride, which is prepared through a primary salt forming reaction or a cold reaction, enters a photochemical kettle 1 at a certain flow rate, meanwhile, a product after the reaction and an unreacted material continuously enter the photochemical kettle 2, reaction liquid in the photochemical kettle 2 is continuously sent to a separation emulsifier 3 and is divided in the separation emulsifier 3, most of liquid reaction liquid enters the next stage of process from a filtrate discharge port 11 through a filter layer 9, a small amount of reaction liquid containing solids (mainly amine salt and solid acyl chloride) enters an emulsification cavity to be crushed and dispersed, and then returns to the photochemical kettle 1, and the concentration of the reaction liquid in the photochemical kettle 1 is basically maintained to be balanced after the reaction liquid lasts for a period of time.

As shown in fig. 2, the separation emulsifier adopted in the embodiment of the present invention is a gas-liquid-solid three-phase separation emulsifier, which specifically includes: a filtrate cavity 18, a separation cavity 19 and an emulsification cavity 20, wherein the filtrate cavity 18 surrounds the separation cavity 19, and the emulsification cavity is positioned below the separation cavity 19; the separation cavity 19 is provided with a feed inlet 5 and an air outlet 21, the filtrate cavity 18 is provided with a filtrate discharge port 11, the emulsification cavity 20 is provided with an emulsification cavity liquid outlet 15, the liquid at the outlet is communicated with the photochemical kettle 1, and the filtrate at the filtrate discharge port 11 is connected to the next stage of process.

In the separation emulsifier of the embodiment of the present invention, specifically, the feed port 5 and the gas outlet 21 are located at the top of the separation chamber 19, the filtrate discharge port 11 is located at the bottom of the filtrate chamber 18, and the emulsion chamber liquid outlet 15 is located at the bottom of the emulsion chamber 20, and in a preferred embodiment, the separation chamber 19 includes an upper cylindrical chamber and a lower inverted conical chamber.

The separation emulsifier provided by the embodiment of the invention further comprises a filter layer 9, a residue scraper 8, a vortex wheel 12, a static gear 13 and a moving gear 14, wherein the filter layer 9 is arranged at the periphery of the separation cavity 19, namely the filter layer 9 is arranged between the separation cavity 19 and the filtrate cavity 18; the filter residue scraper 8 is fixed on the fixed rod 7 in the separation cavity 19, the vortex wheel 12 and the moving gear 14 are fixed on the rotating shaft in the emulsification cavity 20, and the two rotate in the same direction.

Specifically, the cylindrical cavity at the upper part of the separation cavity 19 comprises a metal cylinder 10 with a porous structure, and a cavity is formed inside; the outer surface of the metal cylinder 10 is provided with a filter medium as a filter layer 9, and the pore diameter selection range of the filter medium is as follows: 50-300 meshes, and the material is preferably a metal woven net or a sintered net.

Specifically, the filter residue scrapers 8 are fixed on scraper fixing rods 7 of the separation cavity 19, and the number of the fixing rods 7 is 3, and the fixing rods are uniformly distributed in the separation cavity; each fixing rod 7 fixes a plurality of residue scraping plates 8, preferably 4, at equal intervals from top to bottom; the filter residue scrapers 8 between the fixed rods 7 are distributed in a staggered manner, so that filter residues on the filter medium can be completely removed, the filter residue scrapers have a certain downward inclination along the rotating direction, the selected inclination angle of the filter residue scrapers is 5-30 degrees, the distance between the tips of the filter residue scrapers and the surface of the filter medium is 0.2-2mm, and the preferred distance is 0.5-1 mm; the fixed disk 6 rotates at a speed of 10-100r/min, preferably 30-50r/min, and rotates in the same direction as the scroll wheel 12. The squeegee fixing lever 7 is not rotatable alone but is rotated along with the fixed disk 6.

Specifically, the diameter ratio of the upper end opening and the lower end opening of the inverted cone-shaped cavity at the lower part of the separation cavity 19 is 10:1-2:1, and the diameter of the upper end opening is the diameter of the cylindrical cavity.

Specifically, the vortex wheel 12 is located at the junction of a cylindrical cavity at the upper part of the separation cavity 19 and an inverted conical cavity at the lower part of the separation cavity and consists of an impeller 23, a bottom disc 22 and a central fixed shaft 24, the impellers 23 are uniformly distributed, the ratio of the diameter of the vortex wheel 12 to the diameter inside the separation cavity 19 is 1:30-1:3, the rotating speed of the vortex wheel 12 is 50-500r/min, the vortex wheel rotates clockwise facing the impeller 23, the gas-liquid-solid three-phase separation emulsifier further comprises a liquid level meter 17 which is arranged inside the separation cavity 19, and the liquid level of the separation cavity 19 is preferably 30-70% of the total volume of the separation cavity.

Specifically, the emulsification chamber 20 is a solid particle crushing chamber, and is composed of three groups of static gears 13 and moving gears 14, after a reaction liquid containing high-concentration solid particles enters, the solid particles are crushed through the high-speed rotation of the moving gears, the particle size of the solid particles which can be crushed is 10000um, the particle size of the solid particles after crushing is 10-100um, and the single-pass crushing rate is 50-90%.

Specifically, the ratio of the flow of the lower liquid flow of the emulsification cavity to the flow of the filtrate in the filtrate cavity is 1:9-1: 19.

The ratio of the inner diameters of a gas phase pipe used for the gas outlet 20, a discharge pipe used for the filtrate discharge port 11 and a feed pipe used for the separation cavity feed port 5 is 5-10:1.5-3: 1.

The cavity volume ratio of the separation cavity 19, the filtrate cavity 18 and the emulsification cavity 20 is preferably 1:1:0.1-1:2: 0.5.

Examples 1, 2 and 3 relate to separation emulsifier parameter adjustment, and examples 1, 4 and 5 relate to reaction process parameter adjustment.

Example 1

The diameter of the cylindrical part of the separation cavity on the upper part of the separation emulsifier is 1200mm, the height of the cylindrical part is 2000mm, the vertical height of the inverted cone part on the lower part of the separation cavity of the separation emulsifier is 400mm, the diameter of the lower opening of the inverted cone part is 200mm, the layer width of the filtrate cavity is 300mm, and the diameter of the vortex wheel is 100 mm. The diameter of the filtrate discharge port is 50mm, the filtrate discharge port is positioned at the junction of the cylindrical part and the inverted cone part of the separation cavity, the inner diameter of the feed port is 20mm, the filtrate discharge port is positioned at the top of the separation emulsifier, and the inner diameter of the gas outlet is 100 mm. The medium of the filtering layer is a stainless steel sintering net with 200 meshes, the distance between the tip of the residue filtering scraper and the filtering net is 1mm, and the included angle between the scraper and the fixed rod is 5 ℃.

The volumes of the photochemical reactor 1 and the photochemical reactor 2 are both 1m³The o-dichlorobenzene solution containing XDA hydrochloride prepared by primary salifying reaction (the concentration of XDI generated theoretically is 12%) enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction pressure (absolute pressure) is 0.1MPa, and the reaction temperature is 140The phosgene inlet amount of the photochemical kettles 1 and 2 is 60.0kg/h, the average residence time of the reaction liquid in the photochemical kettle 1 is adjusted to be 1h, the average residence time in the photochemical kettle 2 is 1.5h by controlling the liquid level of the reaction kettle, the rotating speed of a vortex wheel in the emulsifying separator is 100r/min, the rotating speed of a fixed disk is 20r/min, the discharging speed of a liquid outlet of the emulsifying cavity is 15.1kg/h, the discharging speed of a liquid outlet of the filtrate cavity is 136.0kg/h, and the average residence time of the photochemical liquid in the separation emulsifier is about 10 min. Samples were taken from photochemical kettle 1 and analyzed for reaction solution having a GC concentration of 9.8% (calibrated to actual concentration) and for reaction solution in photochemical kettle 2 having a GC concentration of 11.9% (calibrated to actual concentration).

Example 2

The diameter of the cylindrical part of the separation cavity on the upper part of the separation emulsifier is 1200mm, the height of the cylindrical part is 2000mm, the vertical height of the inverted cone part on the lower part of the separation cavity of the separation emulsifier is 200mm, the diameter of the lower opening of the inverted cone part is 600mm, the layer width of the filtrate cavity is 400mm, and the diameter of the scroll wheel is 400 mm. The diameter of the filtrate discharge port is 30mm, the filtrate discharge port is positioned at the junction of the cylindrical part and the inverted cone part of the separation cavity, the inner diameter of the feed port is 20mm, the filtrate discharge port is positioned at the top of the separation emulsifier, and the inner diameter of the gas outlet is 200 mm. The medium of the filtering layer is a 300-mesh stainless steel sintering net, the distance between the tip of the residue filtering scraper and the filtering net is 0.2mm, and the included angle between the scraper and the fixed rod is 15 ℃.

The volumes of photochemical kettles 1 and 2 are both 1m³An o-dichlorobenzene solution containing XDA hydrochloride prepared by primary salifying reaction (the concentration of XDI generated theoretically is 12%) enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction pressure (absolute pressure) is 0.1MPa, the reaction temperature is 140 ℃, the phosgene introducing amount of the photochemical kettle 1 and phosgene introducing amount of the photochemical kettle 2 are both 60.0kg/h, the average residence time of a reaction liquid in the photochemical kettle 1 is adjusted to be 1h by controlling the liquid level of the reaction kettle, the average residence time in the photochemical kettle 2 is 1.5h, the rotating speed of a vortex wheel in an emulsification separator is 50r/min, the rotating speed of a fixed disk is 10r/min, the discharging speed of a liquid outlet of an emulsification cavity is 10.0kg/h, the discharging speed of a liquid outlet of a filtrate cavity is 142.0kg/h, and the average residence time of the photochemical liquid in a separation emulsifier is about 15 min. Samples were taken from photochemical kettle 1 and analyzed for reaction solution having a GC concentration of 9.9% (calibrated to actual concentration) and for reaction solution in photochemical kettle 2 having a GC concentration of 11.9% (calibrated to actual concentration).

Example 3

The diameter of the cylindrical part of the separation cavity on the upper part of the separation emulsifier is 1200mm, the height of the cylindrical part is 2000mm, the vertical height of the inverted cone part on the lower part of the separation cavity of the separation emulsifier is 200mm, the diameter of the lower opening of the inverted cone part is 120mm, the layer width of the filtrate cavity is 300mm, and the diameter of the scroll wheel is 40 mm. The diameter of the filtrate discharge port is 60mm, the filtrate discharge port is positioned at the junction of the cylindrical part and the inverted cone part of the separation cavity, the inner diameter of the feed port is 30mm, the filtrate discharge port is positioned at the top of the separation emulsifier, and the inner diameter of the gas outlet is 300 mm. The medium of the filter layer is a 50-mesh metal woven mesh, the distance between the tip of the residue scraper and the filter screen is 2mm, and the included angle between the scraper and the fixed rod is 30 ℃.

The volumes of photochemical kettles 1 and 2 are both 1m³An o-dichlorobenzene solution containing XDA hydrochloride prepared by primary salifying reaction (the concentration of XDI generated theoretically is 12%) enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction pressure (absolute pressure) is 0.1MPa, the reaction temperature is 140 ℃, the phosgene introducing amount of the photochemical kettle 1 and phosgene introducing amount of the photochemical kettle 2 are both 60.0kg/h, the average residence time of a reaction liquid in the photochemical kettle 1 is adjusted to be 1h by controlling the liquid level of the reaction kettle, the average residence time in the photochemical kettle 2 is 1.5h, the rotating speed of a vortex wheel in an emulsification separator is 500r/min, the rotating speed of a fixed disk is 100r/min, the discharging speed of a liquid outlet of an emulsification cavity is 7.6kg/h, the discharging speed of a liquid outlet of a filtrate cavity is 144.4kg/h, and the average residence time of the photochemical liquid in a separation emulsifier is about 2 min. The reaction solution was analyzed by sampling in photochemical kettle 1 at a GC concentration of 10.1% (calibrated to the actual concentration) and in photochemical kettle 2 at a GC concentration of 12.0% (calibrated to the actual concentration).

Example 4

The diameter of the cylindrical part of the separation cavity on the upper part of the separation emulsifier is 1200mm, the height of the cylindrical part is 2000mm, the vertical height of the inverted cone part on the lower part of the separation cavity of the separation emulsifier is 100mm, the diameter of the lower opening of the inverted cone part is 300mm, the layer width of the filtrate cavity is 350mm, and the diameter of the scroll wheel is 100 mm. The diameter of the filtrate discharge port is 50mm, the filtrate discharge port is positioned at the junction of the cylindrical part and the inverted cone part of the separation cavity, the inner diameter of the feed port is 20mm, the filtrate discharge port is positioned at the top of the separation emulsifier, and the inner diameter of the gas outlet is 100 mm. The medium of the filtering layer is a stainless steel sintering net with 200 meshes, the distance between the tip of the residue filtering scraper and the filtering net is 1mm, and the included angle between the scraper and the fixed rod is 5 ℃.

The volumes of photochemical kettles 1 and 2 are both 1m³The chlorobenzene solution containing PPDA hydrochloride (the concentration of PPDI generated theoretically is 10%) prepared by primary salification reaction enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction pressure is 0.15MPa (gauge pressure), the reaction temperature is 120 ℃, the phosgene introducing amount of the photochemical kettles 1 and 2 is 75.0kg/h, the average residence time of the reaction solution in the photochemical kettle 1 is adjusted to 1.2h by controlling the liquid level of the reaction kettle, the average residence time in the photochemical kettle 2 is 1.5h, the turbine rotating speed in an emulsion separator is 100r/min, the fixed disk rotating speed is 20r/min, the discharging speed of an emulsion cavity is 10.0kg/h, the discharging speed of a filtrate cavity is 143.0kg/h, and the average residence time of the photochemical solution in a separation emulsifier is about 11 min. Samples were taken from photochemical kettle 1 and analyzed for the reaction solution having a GC concentration of 8.3% (calibrated to actual concentration) and for the reaction solution in photochemical kettle 2 having a GC concentration of 9.9% (calibrated to actual concentration).

Example 5

The diameter of the cylindrical part of the separation cavity on the upper part of the separation emulsifier is 1200mm, the height of the cylindrical part is 2000mm, the vertical height of the inverted cone part on the lower part of the separation cavity of the separation emulsifier is 200mm, the diameter of the lower opening of the inverted cone is 200mm, the layer width of the filtrate cavity is 400mm, and the diameter of the scroll wheel is 100 mm. The diameter of the filtrate discharge port is 50mm, the filtrate discharge port is positioned at the junction of the cylindrical part and the inverted cone part of the separation cavity, the inner diameter of the feed port is 20mm, the filtrate discharge port is positioned at the top of the separation emulsifier, and the inner diameter of the gas outlet is 100 mm. The medium of the filtering layer is a stainless steel sintering net with 200 meshes, the distance between the tip of the residue filtering scraper and the filtering net is 1mm, and the included angle between the scraper and the fixed rod is 5 ℃.

The volumes of photochemical kettles 1 and 2 are both 1m³The chlorobenzene solution containing TDA hydrochloride prepared by primary salification reaction (the concentration of TDI generated theoretically is 30%) enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction pressure is 0.5MPa (gauge pressure), the reaction temperature is 170 ℃, the phosgene introducing amount of the photochemical kettles 1 and 2 is 100.0kg/h, the average residence time of the reaction solution in the photochemical kettle 1 is adjusted to 1.3h by controlling the liquid level of the reaction kettle, the average residence time in the photochemical kettle 2 is 2h, the rotating speed of a turbine in an emulsifying separator is 100r/min, the rotating speed of a fixed disk is 20r/min, the discharging speed of a liquid outlet of an emulsifying cavity is 15.0kg/h, and the discharging speed of a liquid outlet of a filtrate cavity is 135.0kg/hThe mean residence time of the photochemical solution in the separating emulsifier was about 12 min. Samples were taken from photochemical kettle 1 and analyzed for the reaction solution having a GC concentration of 25.6% (calibrated to actual concentration) and for the reaction solution in photochemical kettle 2 having a GC concentration of 29.9% (calibrated to actual concentration).

Comparative example 1

The photochemical reaction is carried out continuously in a reaction kettle without a separation emulsifier, and the volumes of photochemical kettles 1 and 2 are both 1m³An o-dichlorobenzene solution containing XDA hydrochloride (the concentration of XDI generated theoretically is 12%) prepared by primary salifying reaction enters a photochemical kettle 1 at the flow rate of 150.0kg/h, the reaction is carried out at normal pressure, the reaction temperature is 140 ℃, the phosgene introducing amount of the photochemical kettle 1 and the phosgene introducing amount of the photochemical kettle 2 are both 60.0kg/h, the average residence time of a reaction solution in the photochemical kettle 1 is adjusted to be 1h by controlling the liquid level of the reaction kettle, and the average residence time in the photochemical kettle 2 is adjusted to be 3.5 h. The GC concentration of the sample analysis reaction liquid in the photochemical kettle 1 is 9.8 percent (calibrated with the actual concentration), the GC concentration of the reaction liquid in the photochemical kettle 2 is 11.7 percent (calibrated with the actual concentration), and the photochemical liquid contains spherical solid ammonium salt with the particle size of 0.5-10 mm.

Comparative example 2

The photochemical reaction is carried out continuously in a reaction kettle without a separation emulsifier, and the volumes of photochemical kettles 1 and 2 are both 1m³The method comprises the following steps of firstly, enabling a chlorobenzene solution containing PPDA hydrochloride (the concentration of PPDI generated theoretically is 10%) prepared through salt forming reaction to enter a photochemical kettle 1 at a flow rate of 150.0kg/h, wherein the reaction pressure is 0.15MPa (gauge pressure), the reaction temperature is 120 ℃, phosgene introduction amounts of the photochemical kettle 1 and the photochemical kettle 2 are both 75.0kg/h, adjusting the average residence time of a reaction solution in the photochemical kettle 1 to be 1.2h and the average residence time in the photochemical kettle 2 to be 3.0h by controlling the liquid level of the reaction kettle, adjusting the GC concentration of a sample analysis reaction solution in the photochemical kettle 1 to be 8.2% (calibrated with the actual concentration), adjusting the GC concentration of the reaction solution in the photochemical kettle 2 to be 9.7% (calibrated with the actual concentration), and enabling the photochemical solution to contain spherical solid ammonium salt and have different particle sizes of 0.5-10 mm.

From the comparative analysis of the above example 1 and comparative example 1, and the comparative example 4 and comparative example 2, the residence time of the photochemical solution in the photochemical kettle 2 of the comparative example 1 is longer than that of the example 1 of the invention, and the residence time of the photochemical solution in the photochemical kettle 2 of the comparative example 2 is longer than that of the example 4 of the invention; however, the reaction solution in the photochemical kettle 2 is analyzed, and the concentration of the reaction solution in the comparative example 1 is lower than that in the example 1 of the invention, and the concentration of the reaction solution in the comparative example 2 is lower than that in the example 4 of the invention. Indicating that there was still a lot of solid hydrochloride and acid chloride that was not converted. Therefore, by adopting the separation emulsifier and the process for preparing the isocyanate, high-purity reaction liquid without solid ammonium salt or solid acyl chloride substances can be obtained in the application of photochemical procedures, the reaction yield is improved, and the reaction time is shortened.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Not all embodiments are exhaustive. All obvious changes or modifications of the technical solution of the present invention are within the spirit of the present invention.