CN118772017A - A method and system for preparing isocyanate - Google Patents

Abstract

The present invention relates to the field of isocyanates, and in particular to a method and system for preparing isocyanates, the method comprising the following steps: reacting diphenylmethane series diamines and polyamines with phosgene to obtain a first reaction mixture; mixing the first reaction mixture with a phosgene-containing mixture to react to obtain a second reaction mixture; and decomposing the second reaction mixture to obtain the isocyanate; wherein the temperature of the first reaction mixture is 40 to 150° C., and the temperature of the second reaction mixture is 20 to 120° C. The method for preparing isocyanates in one embodiment of the present invention can reduce the content of diamine hydrochloride impurities in the obtained crude isocyanate product by reacting the first reaction mixture obtained by reacting diamines and polyamines with phosgene with phosgene at a relatively low temperature, and reduce or eliminate the influence of the impurities on the reaction device.

Description

A method and system for preparing isocyanate

Technical Field

The present invention relates to isocyanate, and in particular to a method and system for preparing isocyanate by phosgenation reaction.

Background Art

Isocyanates all have -NCO functional groups in their molecular structures. Currently, phosgenation is mainly used to produce such substances at home and abroad. Under the corresponding temperature and pressure conditions, diphenylmethane series diamines and polyamines (referred to as "diamines and polyamines"), phosgene and inert solvents are mixed and reacted to obtain a photochemical reaction liquid containing isocyanate and hydrogen chloride. After separating the inert solvent and phosgene in the photochemical reaction liquid, a crude isocyanate product can be obtained, and the crude product can be separated to obtain an isocyanate product.

The reaction of the above-mentioned diamines and polyamines with phosgene to generate isocyanates requires two intermediate steps. The first step includes rapidly reacting the diamines and polyamines with excess phosgene at low temperature to generate isocyanate precursor formamide chloride, i.e., cold phosgenation reaction; the second step includes decomposing the isocyanate precursor into isocyanate and hydrogen chloride at high temperature, i.e., hot phosgenation reaction. The temperature generally used in cold phosgenation is lower than that in the hot phosgenation process. In the hot phosgenation process, the reaction temperature is generally in the range of 100°C to 200°C.

However, since the mixing of the reaction streams cannot be completely uniform, the cold phosgenation reaction is difficult to be fully carried out on the scale of industrial equipment, and its main by-products are polyphenylmethane polyamine hydrochloride, polyphenylmethane polyurea, etc. Such substances are easy to deposit in the reactor during subsequent processes, such as the decomposition of formamide chloride and the removal of phosgene, causing the reactor to clog and need to be shut down for cleaning after a certain period of operation, which greatly increases production costs and affects production efficiency.

Summary of the invention

In order to overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a method for preparing isocyanate, comprising the following steps:

reacting diphenylmethane series diamines and polyamines with phosgene to obtain a first reaction mixture;

mixing the first reaction mixture with a phosgene-containing mixture to react to obtain a second reaction mixture; and

subjecting the second reaction mixture to a decomposition reaction to obtain the isocyanate;

The temperature of the first reaction mixture is higher than that of the second reaction mixture, the temperature of the first reaction mixture is 40-150°C, and the temperature of the second reaction mixture is 20-120°C.

In a second aspect, an embodiment of the present invention provides a system for preparing isocyanate, comprising:

A first reaction device is used to react diphenylmethane series diamines and polyamines with phosgene to obtain a first reaction mixture;

a second reaction device, for mixing the first reaction mixture with a phosgene-containing mixture for reaction to obtain a second reaction mixture; and

A reactive distillation tower, used for performing a decomposition reaction on the second reaction mixture to obtain isocyanate;

Wherein, the second reaction device is a jet reactor.

In a third aspect, an embodiment of the present invention provides a jet reactor, comprising a heat exchange section, a throat jet section and a mixing section which are sequentially connected; wherein the heat exchange section comprises an inner tube and an outer tube, the inner tube comprises a material cavity for accommodating a material, the inner tube is arranged inside the outer tube, and a heat exchange cavity is formed between the tube wall of the inner tube and the tube wall of the outer tube; the heat exchange cavity and the material cavity are both connected to the throat jet section;

The heat exchange section and the mixing section are both circular tubes, and the throat jet section is an irregular circular tube, whose longitudinal section includes two arcs arranged opposite to each other, and the distance between the tangents of the two arcs is equal to the minimum inner diameter of the throat jet section; the inner diameter of the inner tube of the heat exchange section and the inner diameter of the mixing section are larger than the minimum inner diameter of the throat jet section.

In one embodiment of the isocyanate preparation method of the present invention, the first reaction mixture obtained by reacting diamines and polyamines with phosgene is reacted with phosgene at a relatively low temperature, thereby reducing the content of diamine hydrochloride and/or polyamine hydrochloride impurities in the obtained crude isocyanate product and reducing or eliminating the impact of the impurities on the reaction device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

FIG1 is a schematic structural diagram of a jet reactor according to an embodiment of the present invention;

FIG2 is a schematic structural diagram of a system for preparing isocyanate according to an embodiment of the present invention;

The following are the descriptions of the reference numerals:

100. First reaction device; 200. Second reaction device; 210. Heat exchange section; 211. Inner tube; 212. Outer tube; 213. Material chamber; 214. Heat exchange chamber; 220. Throat jet section; 230. Mixing section; 300. Phase separation device; 400. Reaction distillation tower; 410. Pump 1; 420. Heat exchange device; 430. Pump 2.

DETAILED DESCRIPTION

Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions therein are essentially used as illustrations rather than to limit the present invention.

One embodiment of the present invention provides a method for preparing isocyanate, comprising the following steps:

S1: reacting diphenylmethane series diamines and polyamines with phosgene (cold photogasification reaction) to obtain a first reaction mixture including an isocyanate precursor;

S2: mixing the first reaction mixture with the phosgene-containing mixture to react to obtain a second reaction mixture; and

S3: subjecting the isocyanate precursor in the second reaction mixture to a decomposition reaction (thermal phosgenation reaction) to obtain isocyanate;

The temperature of the first reaction mixture is higher than that of the second reaction mixture. The temperature of the first reaction mixture is 40-150°C, and the temperature of the second reaction mixture is 20-120°C.

In one embodiment, the prepared isocyanate may be diphenylmethane diisocyanate and/or polyphenylmethane polyisocyanate.

In one embodiment, diamine, polyamine and phosgene are reacted in an inert solvent to obtain a first reaction mixture, and the reaction temperature may be the same as the temperature of the obtained first reaction mixture.

In one embodiment, the reaction temperature of step S1 or the temperature of the first reaction mixture may be 40-150° C., such as 45° C., 58° C., 60° C., 70° C., 82° C., 85° C., 95° C., 110° C., 130° C., 140° C., 145° C., 148° C. Further, the reaction temperature of step S1 or the temperature of the first reaction mixture may be 80-95° C.

In one embodiment, the devices and process involved in step S1 can refer to conventional devices and processes in the art, such as the devices and processes disclosed in CN111995549A and CN108079921B.

In one embodiment, the reaction pressure of step S1 or the pressure of the first reaction mixture may be 1.5 to 6.0 barg, such as 2.7 barg, 3.0 barg, 3.5 barg, 4.0 barg, 5.0 barg. Further, the reaction pressure of step S1 or the pressure of the first reaction mixture may be 2.0 to 4.0 barg.

In one embodiment, the first reaction mixture includes an inert solvent, and the inert solvent can be one or more of diethyl isophthalate, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene. Further, the inert solvent can be chlorobenzene and/or o-dichlorobenzene. Further, the inert solvent can be chlorobenzene.

In one embodiment, the first reaction mixture includes an inert solvent, the target product of the step S1 reaction, which is a formamide chloride precursor, and a byproduct. The byproduct may include diphenylmethane diamine hydrochloride (referred to as "diamine hydrochloride") and/or polyphenylmethane polyamine hydrochloride (referred to as "polyamine hydrochloride"), and further, the byproduct may also include polyphenylmethane polyurea.

In one embodiment, the phosgene-containing mixture includes phosgene and an inert solvent, and the inert solvent can be one or more of diethyl isophthalate, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene. Further, the inert solvent can be chlorobenzene and/or o-dichlorobenzene. Further, the inert solvent can be chlorobenzene.

In one embodiment, by reacting the first reaction mixture with the phosgene-containing mixture at a relatively low reaction temperature (e.g., 20-120° C.), the byproducts contained in the first reaction mixture, such as polyphenylmethane polyamine hydrochloride, can be converted into isocyanate precursors, thereby increasing the conversion rate of the reactants and reducing the content of impurities in the products.

In one embodiment, the reaction temperature of step S2 or the temperature of the second reaction mixture may be 20-120° C., such as 22° C., 32° C., 44° C., 60° C., 65° C., 70° C., 80° C., 98° C., 108° C., 115° C., 117° C. Further, the reaction temperature of step S2 or the temperature of the second reaction mixture may be 55-65° C.

In one embodiment, the pressure of the second reaction mixture may be 3 to 5 barg.

In one embodiment, the first reaction mixture and the phosgene-containing mixture may be subjected to heat exchange treatment to reduce the temperature of the first reaction mixture before the mixed reaction. The temperature of the phosgene-containing mixture may be -30 to 20°C, for example, -29°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 13°C, 15°C, 17°C, 19°C. Further, the temperature of the phosgene-containing mixture may be -10 to 6°C.

In one embodiment, the pressure of the phosgene-containing mixture may be 6-15 barg, such as 8 barg, 9 barg, 10 barg, 11 barg, 12 barg, 13 barg. Further, the pressure of the phosgene-containing mixture may be 10-12 barg.

In one embodiment, the phosgene-containing mixture can be recovered from the reaction system of S3.

In one embodiment, in the phosgene-containing mixture, the mass content of phosgene is 50-90%, such as 55%, 60%, 65%, 70%, 75%, 80%, 85%. Further, the mass content of phosgene can be 80-85%.

In one embodiment, the mass ratio of the phosgene-containing mixture to the first reaction mixture may be 1:5 to 1:10, such as 1:5.5, 1:6, 1:6.5, 1:7, 1:8, 1:9. Further, the mass ratio of the phosgene-containing mixture to the first reaction mixture may be 1:6 to 1:6.5.

In one embodiment, the first reaction mixture and the phosgene-containing mixture are mixed and reacted in a jet reactor, and the jet reactor may be an existing jet-type mixing reaction device for the mixing reaction of two liquid phase substances.

In one embodiment, as shown in FIG. 1 , the jet reactor includes a heat exchange section 210, a throat jet section 220 and a mixing section 230 which are sequentially connected; the heat exchange section 210 is used to perform heat exchange treatment between the first reaction mixture and the phosgene-containing mixture, and the phosgene-containing mixture and the first reaction mixture after heat exchange are mixed and reacted in the mixing section 230 through the throat jet section 220, and then discharged from the jet reactor to obtain a second reaction mixture.

In one embodiment, the heat exchange section 210 includes an inner tube 211 and an outer tube 212, the inner tube 211 includes a material cavity 213 for accommodating materials, the inner tube 211 is disposed inside the outer tube 212, and a heat exchange cavity 214 is formed between the tube wall of the inner tube 211 and the tube wall of the outer tube 212. During operation, the first reaction mixture enters the throat jet section 220 through the material cavity 213, and the phosgene-containing mixture enters the throat jet section 220 through the heat exchange cavity 214. The high-temperature first reaction mixture and the low-temperature phosgene-containing mixture flow in the heat exchange section 210 at the same time, enabling the two to exchange heat.

In one embodiment, the heat exchange chamber 214 and the material chamber 213 are both connected to the throat jet section 220 .

In one embodiment, the throat jet section 220 is an irregular circular tube, the diameter of which is larger at both ends than in the middle, and the diameter gradually decreases from both ends to the middle, with the smallest diameter in the middle. Further, the longitudinal section of the throat jet section 220 includes two arcs arranged opposite to each other, and the distance between the tangents of the two arcs is equal to the minimum inner diameter d1 of the throat jet section. The longitudinal section refers to a section parallel to the axis direction of the throat jet section 220 or a section along the length direction.

In one embodiment, the centers of the two arcs of the longitudinal section of the throat jet section 220 are located outside the longitudinal section.

In one embodiment, two arcs of the longitudinal section of the throat jet section 220 have the same radius and/or curvature.

In one embodiment, the two arcs of the longitudinal section of the throat jet section 220 are symmetrically arranged. Further, the two arcs are symmetrical about the axis of the throat jet section 220, that is, the two arcs are respectively located on both sides of the axis of the longitudinal section.

In one embodiment, the inner tube 211 and the outer tube 212 of the heat exchange section 210 may both be circular tubes, and the inner diameter d4 of the inner tube is greater than the minimum inner diameter d1 of the throat jet section.

In one embodiment, the ratio of the inner diameter d3 of the outer tube to the inner diameter d2 of the mixing section can be 0.6:1 to 0.8:1, for example, 0.7:1; the ratio of the inner diameter d4 of the inner tube to the inner diameter d2 of the mixing section can be 0.5:1 to 0.7:1, for example, 0.6:1; wherein the inner diameter d3 of the outer tube is greater than the inner diameter d4 of the inner tube; the ratio of the height (or width) d5 of the annular heat exchange cavity (i.e., the size of the gap between the inner tube 211 and the outer tube 212) to the inner diameter d2 of the mixing section can be 0.05:1 to 0.15:1, for example, 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.14:1. The value of d5 is equal to the value obtained by subtracting the outer diameter of the inner tube 211 from the inner diameter d3 of the outer tube and then dividing by 2.

In one embodiment, the mixing section 230 is a circular tube, and the inner diameter d2 of the mixing section is greater than the minimum inner diameter d1 of the throat jet section. Further, the ratio of the minimum inner diameter d1 of the throat jet section to the inner diameter d2 of the mixing section can be 1:6 to 1:10, and further can be 1:6 to 1:8, for example 1:7, 1:9.

In one embodiment, the time for the first reaction mixture and/or the phosgene-containing mixture to exchange heat in the heat exchange section 210 (or the time for flowing through the heat exchange section 210) is 4 to 8 seconds, and can further be 5 to 6 seconds, which is the time from the time the material enters the heat exchange section 210 to the time it leaves the heat exchange section 210.

In one embodiment, the residence time of the material discharged from the heat exchange section (i.e., the first reaction mixture and the phosgene-containing mixture) in the throat jet section 220 (or the time flowing through the throat jet section 220) is 0.2 to 1 s, and can further be 0.4 to 0.6 s.

In one embodiment, the residence time of the material discharged from the throat jet section 220 (i.e., the material obtained by mixing the phosgene-containing mixture with the first reaction mixture) in the mixing section 230 (or the time it flows through the mixing section 230) is 10 to 15 seconds, and can further be 12 to 13 seconds.

In one embodiment, as shown in FIG. 2 , the reaction of the second reaction mixture can be carried out in a decomposition reactor, such as a reaction distillation tower 400. The reaction distillation tower 400 includes a tower bottom, a tower top, and a tower body connecting the tower top and the tower bottom, and a gas feed port is provided on the tower body. The area between the gas feed port and the tower bottom is a reaction section, and a tower tray, a filler, etc. are provided in the reaction section to achieve the decomposition of the formamide chloride compound.

In one embodiment, the second reaction mixture discharged from the jet reactor can be separated (or phase-separated) to obtain a decomposition reaction gas phase material and a decomposition reaction liquid phase material, and the decomposition reaction gas phase material is introduced into the reaction distillation tower 400 from the gas feed port, and the decomposition reaction liquid phase material is introduced into the tower bottom; wherein the distance between the gas feed port and the tower bottom is greater than the distance between the gas feed port and the tower top.

In one embodiment, the second reaction mixture can be separated by a phase separation device 300 , and the phase separation device 300 can be an existing phase separation tank.

In one embodiment, the mass ratio of the decomposition reaction gas phase material to the decomposition reaction liquid phase material may be 1:2 to 1:3, and further may be 1:2.2 to 1:2.5.

In one embodiment, the number of theoretical plates of the whole reactive distillation tower 400 is 24 to 30. According to the height calculation, counting from top to bottom (from the top to the bottom), the gas feed port can be located within the range of the 12th to 16th or 14th to 15th tower plates. The feed position of the decomposition reaction liquid phase material is the bottom of the tower or close to the bottom of the tower.

In one embodiment, the tower body material of the reactive distillation tower 400 is Hastelloy or 316L.

In one embodiment, during the preparation of isocyanate, the bottom temperature of the reaction distillation tower 400 can be 150-210°C, and can further be 180-200°C, for example, 160°C, 170°C, 185°C, 190°C, 195°C; the top temperature can be 40-50°C, and can further be 45-48°C; the top pressure can be 0.3-0.6MPag, for example, 0.4MPag, 0.5MPag.

In one embodiment, the isocyanate precursor in the second reaction mixture is decomposed in the reaction distillation tower 400, and the generated hydrogen chloride gas is discharged from the top of the tower, and a crude product containing isocyanate and an inert solvent can be obtained from the bottom of the tower. Further, the crude product in the bottom of the tower can be discharged from the reaction distillation tower 400 through a pump 1 410.

In one embodiment, a phosgene-containing mixture can be withdrawn laterally from the middle of the tower body, cooled by a heat exchange device 420 (e.g., a heat exchanger), and then sent to the second reaction device 200 by a pump 430 to perform heat exchange and mixing reaction with the first reaction mixture.

In one embodiment, the temperature of the phosgene-containing mixture extracted from the reaction distillation tower 400 may be 50-60° C., and further may be 55-58° C. The phosgene-containing mixture may be cooled to −30-20° C. by the heat exchange device 420 and then transported to the second reaction device 200 .

An embodiment of the present invention provides an isocyanate preparation system that can be used to implement the above-mentioned preparation method, comprising a first reaction device 100, a second reaction device 200 and a reaction distillation tower 400; wherein the first reaction device 100 is used to react diamines and polyamines with phosgene to obtain a first reaction mixture; the second reaction device 200 is used to mix the first reaction mixture with a phosgene-containing mixture for reaction to obtain a second reaction mixture; the reaction distillation tower 400 is used to react the second reaction mixture to obtain isocyanate; wherein the second reaction device 200 is a jet reactor.

In one embodiment, the first reaction device 100 is connected to the second reaction device 200 to deliver the first reaction mixture to the second reaction device 200 for reaction. Further, the first reaction mixture can be delivered to the second reaction device 200 by a pump.

In one embodiment, the first reaction device 100 may include a static mixer and a dynamic reactor.

In one embodiment, the structure of the jet reactor can refer to the above description.

In one embodiment, the jet reactor includes a heat exchange section 210, a throat jet section 220 and a mixing section 230 which are connected in sequence; the heat exchange section 210 includes an inner tube 211 and an outer tube 212, the inner tube includes a material cavity 213 for accommodating materials, the inner tube 211 is arranged inside the outer tube 212, and a heat exchange cavity 214 is formed between the tube wall of the inner tube 211 and the tube wall of the outer tube 212.

In one embodiment, the first reaction device 100 may be connected to the heat exchange section 210 , and further, the first reaction device 100 is connected to the inner tube 211 of the heat exchange section 210 .

In one embodiment, the throat jet section 220 is an irregular circular tube, and its longitudinal section includes two arcs arranged opposite to each other, and the distance between the tangents of the two arcs is equal to the minimum inner diameter d1 of the throat jet section.

In one embodiment, the preparation system further includes a phase separation device 300 for separating the second reaction mixture to obtain a decomposition reaction gas phase material and a decomposition reaction liquid phase material.

In one embodiment, the phase separation device 300 is connected to the second reaction device 200 and the reaction distillation tower 400 respectively, and can be an existing phase separation tank. Further, the phase separation device 300 is connected to the mixing section 230 of the second reaction device 200.

In one embodiment, the structure of the reactive distillation tower 400 can refer to the above description.

In one embodiment, the reaction distillation tower 400 includes a tower top, a tower bottom, and a tower body connecting the tower top and the tower bottom, and a gas feed port and a phosgene outlet are provided on the tower body. The gas feed port is used to feed the decomposition reaction gas phase material, and the phosgene outlet is used to extract the phosgene-containing mixture in the reaction distillation tower 400.

In one embodiment, a pump 410 is provided outside the reaction distillation tower 400 to discharge the crude product in the bottom of the tower out of the tower.

In one embodiment, the phase separation device 300 includes a gas outlet and a liquid outlet, the gas outlet is connected to the gas feed inlet of the reaction distillation tower 400, and the liquid outlet is connected to the tower bottom.

In one embodiment, the distance between the gas feed inlet of the reaction distillation tower 400 and the bottom of the tower is greater than the distance between the gas feed inlet and the top of the tower.

In one embodiment, along the height direction of the tower body, the phosgene outlet is located higher than the gas feed port of the reaction distillation tower 400 . For example, the phosgene outlet may be located at 2 to 10 theoretical plates, preferably 3 to 5 theoretical plates.

In one embodiment, the preparation system further includes a heat exchange device 420, which is connected to the phosgene outlet of the reaction distillation tower 400 to cool the phosgene-containing mixture. In addition, the concentration of phosgene in the phosgene-containing mixture extracted from the reaction distillation tower 400 can be regulated by the cooling treatment of the heat exchange device 420.

In one embodiment, the second reaction device 200 is connected to the heat exchange device 420, and further, the heat exchange device 420 is connected to the heat exchange chamber 214 of the second reaction device 200, so that the phosgene-containing mixture is transported to the heat exchange chamber 214 through pump 2 430 for heat exchange with the first reaction mixture.

In one embodiment, the structure and purpose of each device in the isocyanate preparation system can refer to the structure and purpose of the same device in the aforementioned preparation method.

As shown in FIG1 , an embodiment of the present invention provides a jet reactor, comprising a heat exchange section 210, a throat jet section 220 and a mixing section 230 which are connected in sequence; wherein the heat exchange section 210 comprises an inner tube 211 and an outer tube 212, the inner tube 211 comprises a material cavity 213 for accommodating materials, the inner tube 211 is arranged inside the outer tube 212, and a heat exchange cavity 214 is formed between the tube wall of the inner tube 211 and the tube wall of the outer tube 212; the heat exchange cavity 214 and the material cavity 213 are both connected to the throat jet section 220;

The heat exchange section 210 and the mixing section 230 are both circular tubes, and the throat jet section 220 is an irregular circular tube, whose longitudinal section includes two arcs arranged opposite to each other, and the distance between the tangents of the two arcs is equal to the minimum inner diameter d1 of the throat jet section; the inner tube inner diameter d4 of the heat exchange section 210 and the inner diameter d2 of the mixing section are larger than the minimum inner diameter d1 of the throat jet section.

In one embodiment, the structure of the jet reactor can refer to the above description.

The method for preparing isocyanate according to one embodiment of the present invention can effectively reduce existing production processes, improve the raw material conversion rate, and has a simple process and low operating cost.

The method for preparing isocyanate according to one embodiment of the present invention can reduce the total mass content of diamine hydrochloride and/or polyamine hydrochloride as impurities in the crude product of the reactor of a reactive distillation tower (measured in terms of mass fraction in the crude product) to 400-3000 ppm (the corresponding content in the prior art is 5000-10000 ppm), effectively extending the operation cycle of the reactive distillation tower, for example, the operation cycle of the reactive distillation tower can be extended to 750-800 days, and the pressure drop of the entire tower is 5-10 kPa.

In one embodiment of the present invention, a method for preparing isocyanate is carried out by subjecting the incompletely converted compounds (such as diamine hydrochloride impurities) in the first reaction mixture to a secondary injection reaction with phosgene, and at the same time, the product hydrogen chloride is continuously separated from the reaction system in a reaction distillation tower, so that the equilibrium is moved toward the direction of the product, thereby greatly improving the equilibrium conversion rate of diamine hydrochloride and reducing the loss of isocyanate in the production process.

The method for preparing isocyanate in one embodiment of the present invention reduces the content of insoluble diamine hydrochloride and/or polyamine hydrochloride as reaction by-products, thereby reducing the risk of blockage in the transportation and storage of reaction materials, prolonging the stable operation time of the reaction device, and improving the quality of the isocyanate product.

Hereinafter, a method for preparing isocyanate according to an embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples.

1. Raw materials

Phosgene: Produced by the Yantai MDI unit in Yantai Wanhua Industrial Park, industrial product;

Diphenylmethane series diamines/polyamines: produced by Yantai MDI unit in Yantai Wanhua Industrial Park, industrial products, CAS No. 101-77-9;

Chlorobenzene: purchased from Jiangsu Longchang Chemical Co., Ltd., industrial product, 99%.

2. Test methods

The content of diamine hydrochloride and/or polyamine hydrochloride in the crude product is determined by referring to the method of patent application CN117682962A, using a liquid chromatography method, and the analytical instrument is Agilent 1260.

Example 1

S1: The inert solvent chlorobenzene and the diphenylmethane series diamine/polyamine are mixed in a static mixer at a mass ratio of 3:1 to form a mixed solution; phosgene and the mixed solution are mixed in a dynamic mixer at a mass ratio of phosgene:diamine/polyamine=4:1 to perform a cold photogasification reaction. The temperature of the cold photogasification reaction is controlled at 130°C and the pressure is 2.7 barg. After the reaction, a first reaction mixture with a temperature of 150°C is obtained.

S2: The first reaction mixture is transported to the material chamber 213 of the heat exchange section 210 of the second reaction device 200 by a pump, and the phosgene-containing mixture (temperature of 20° C. and pressure of 12 barg) is transported to the heat exchange chamber 214 of the heat exchange section 210, so that the first reaction mixture and the phosgene-containing mixture are heat exchanged; the first reaction mixture and the phosgene-containing mixture after heat exchange enter the mixing section 230 through the throat jet section 220 for mixed reaction, and the second reaction mixture with a temperature of 120° C. and a pressure of 5 barg is discharged from the mixing section 230;

The mass ratio of the phosgene-containing mixture to the first reaction mixture is 1:6.5, the material is in the heat exchange section 210 for 6 seconds, in the throat jet section 220 for 0.6 seconds, and in the mixing section 230 for 13 seconds. The ratio of the minimum inner diameter d1 of the throat jet section to the inner diameter d2 of the mixing section is 1:8, the ratio of the inner diameter d3 of the outer tube to the inner diameter d2 of the mixing section is 0.8:1, the ratio of the inner diameter d4 of the inner tube to the inner diameter d2 of the mixing section is 0.7:1, and the ratio of the height d5 of the heat exchange chamber to the inner diameter d2 of the mixing section is 0.05:1.

S3: Pass the second reaction mixture into the phase separation device 300 for phase separation to obtain decomposition reaction gas phase material and decomposition reaction liquid phase material, the mass ratio of the decomposition reaction gas phase material and the decomposition reaction liquid phase material is 1:2.5; pass the decomposition reaction gas phase material into the reaction distillation tower 400 from the gas feed port, and pass the decomposition reaction liquid phase material into the tower kettle for decomposition reaction, the tower top pressure is 0.6MPag, the tower top temperature is 48°C, and the tower kettle temperature is 200°C.

During the reaction, hydrogen chloride gas is discharged from the top of the tower, and the crude product containing isocyanate and inert solvent is located in the bottom of the tower and is discharged through pump 1 410; a phosgene-containing mixture with a temperature of 58°C is taken out from the middle of the tower body, wherein the mass content of phosgene is 85%. The phosgene-containing mixture discharged from the reaction distillation tower 400 is cooled to 20°C after heat exchange by the heat exchange device 420, and the cooled phosgene-containing mixture is pressurized to 12 barg by pump 2 430 and then transported to the heat exchange chamber 214 of the heat exchange section 210 of the second reaction device 200.

The number of theoretical plates of the whole reaction distillation tower 400 is 30, counting from top to bottom, the gas feed port is located at the 15th tower plate, and the tower body material is 316L. The phosgene outlet is located above the feed position of the reaction distillation tower 400, counting 5 theoretical plates upward from the feed position.

The total mass content of diamine hydrochloride and/or polyamine hydrochloride in the crude product discharged from the bottom of the tower (based on the mass of the crude product) was measured to be 500 ppm. In addition, the above process can make the operating life of the reaction distillation tower 400 reach 800 days, and the pressure drop of the whole tower is 6 kPa.

Example 2

S1: The inert solvent chlorobenzene and the diphenylmethane series diamine/polyamine are mixed in a static mixer at a mass ratio of 3:1 to form a mixed solution; phosgene and the mixed solution are mixed in a dynamic mixer at a mass ratio of phosgene:diamine/polyamine=4:1 to perform a cold photogasification reaction. The temperature of the cold photogasification reaction is controlled at 30°C and the pressure is 1.5 barg. After the reaction, a first reaction mixture with a temperature of 45°C is obtained.

S2: The first reaction mixture is transported to the material chamber 213 of the heat exchange section 210 of the second reaction device 200 by a pump, and the phosgene-containing mixture (temperature of -30°C and pressure of 6 barg) is transported to the heat exchange chamber 214 of the heat exchange section 210, so that the first reaction mixture and the phosgene-containing mixture are heat exchanged; the first reaction mixture and the phosgene-containing mixture after heat exchange enter the mixing section 230 through the throat jet section 220 for mixed reaction, and the second reaction mixture with a temperature of 20°C and a pressure of 3 barg is discharged from the mixing section 230;

The mass ratio of the phosgene-containing mixture to the first reaction mixture is 1:5, the material is in the heat exchange section 210 for 4 seconds, in the throat jet section 220 for 0.2 seconds, and in the mixing section 230 for 10 seconds. The ratio of the minimum inner diameter d1 of the throat jet section to the inner diameter d2 of the mixing section is 1:6, the ratio of the inner diameter d3 of the outer tube to the inner diameter d2 of the mixing section is 0.6:1, the ratio of the inner diameter d4 of the inner tube to the inner diameter d2 of the mixing section is 0.5:1, and the ratio of the height d5 of the heat exchange cavity to the inner diameter d2 of the mixing section is 0.05:1.

S3: Pass the second reaction mixture into the phase separation device 300 for phase separation to obtain decomposition reaction gas phase material and decomposition reaction liquid phase material, the mass ratio of the decomposition reaction gas phase material and the decomposition reaction liquid phase material is 1:2; pass the decomposition reaction gas phase material into the reaction distillation tower 400 from the gas feed port, and pass the decomposition reaction liquid phase material into the bottom of the tower for decomposition reaction, the tower top pressure is 0.3MPag, the tower top temperature is 40°C, and the tower bottom temperature is 150°C.

During the reaction, hydrogen chloride gas is discharged from the top of the tower, and the crude product containing isocyanate and inert solvent is located in the bottom of the tower and is discharged through pump 1 410; a phosgene-containing mixture with a temperature of 50°C is taken out from the middle of the tower body, wherein the mass content of phosgene is 50%. The phosgene-containing mixture discharged from the reaction distillation tower 400 is cooled to -30°C after heat exchange by the heat exchange device 420, and the cooled phosgene-containing mixture is pressurized to 6 barg by pump 2 430 and then transported to the heat exchange chamber 214 of the heat exchange section 210 of the second reaction device 200.

The number of theoretical plates of the whole reactive distillation tower 400 is 24, counting from top to bottom, the gas feed port is located at the 12th tower plate, and the tower body material is Hastelloy. The phosgene outlet is located above the feed position of the reactive distillation tower 400, and two theoretical plates are counted upward from the feed position.

The total mass content of diamine hydrochloride and/or polyamine hydrochloride in the crude product discharged from the bottom of the tower (based on the mass of the crude product) was measured to be 2800 ppm. In addition, the above process can make the operating life of the reaction distillation tower 400 reach 760 days, and the pressure drop of the whole tower is 10 kPa.

Example 3

S1: The inert solvent chlorobenzene and the diphenylmethane series diamine/polyamine are mixed in a static mixer at a mass ratio of 3:1 to form a mixed solution; phosgene and the mixed solution are mixed in a dynamic mixer at a mass ratio of phosgene:diamine/polyamine=4:1 to perform a cold photogasification reaction. The temperature of the cold photogasification reaction is controlled at 75°C and the pressure is 6 barg. After the reaction, a first reaction mixture with a temperature of 90°C is obtained.

S2: The first reaction mixture is transported to the material chamber 213 of the heat exchange section 210 of the second reaction device 200 by a pump, and the phosgene-containing mixture (temperature of 10°C and pressure of 15 barg) is transported to the heat exchange chamber 214 of the heat exchange section 210, so that the first reaction mixture and the phosgene-containing mixture are heat exchanged; the first reaction mixture and the phosgene-containing mixture after heat exchange enter the mixing section 230 through the throat jet section 220 for mixed reaction, and the second reaction mixture with a temperature of 60°C and a pressure of 5 barg is discharged from the mixing section 230;

The mass ratio of the phosgene-containing mixture to the first reaction mixture is 1:6, the material is in the heat exchange section 210 for 4 seconds, in the throat jet section 220 for 1 second, and in the mixing section 230 for 15 seconds. The ratio of the minimum inner diameter d1 of the throat jet section to the inner diameter d2 of the mixing section is 1:6, the ratio of the inner diameter d3 of the outer tube to the inner diameter d2 of the mixing section is 0.8:1, the ratio of the inner diameter d4 of the inner tube to the inner diameter d2 of the mixing section can be 0.7:1, and the ratio of the height d5 of the heat exchange cavity to the inner diameter d2 of the mixing section is 0.05:1.

S3: Pass the second reaction mixture into the phase separation device 300 for phase separation to obtain decomposition reaction gas phase material and decomposition reaction liquid phase material, the mass ratio of the decomposition reaction gas phase material and the decomposition reaction liquid phase material is 1:3; pass the decomposition reaction gas phase material into the reaction distillation tower 400 from the gas feed port, and pass the decomposition reaction liquid phase material into the bottom of the tower for decomposition reaction, the tower top pressure is 0.6MPag, the tower top temperature is 50°C, and the tower bottom temperature is 210°C.

During the reaction, hydrogen chloride gas is discharged from the top of the tower, and the crude product containing isocyanate and inert solvent is located in the bottom of the tower and is discharged through pump 1 410; a phosgene-containing mixture with a temperature of 60°C is taken out from the middle of the tower body, wherein the mass content of phosgene is 50%. The phosgene-containing mixture discharged from the reaction distillation tower 400 is cooled to 10°C after heat exchange by the heat exchange device 420, and the cooled phosgene-containing mixture is pressurized to 15 barg by pump 2 430 and then transported to the heat exchange chamber 214 of the heat exchange section 210 of the second reaction device 200.

The number of theoretical plates of the whole reactive distillation tower 400 is 30, counting from top to bottom, the gas feed port is located at the 16th tower plate, and the tower body material is Hastelloy. The phosgene outlet is located above the tower feed position of the reactive distillation tower 400, counting 10 theoretical tower plates upward from the feed position.

The total mass content of diamine hydrochloride and/or polyamine hydrochloride in the crude product discharged from the bottom of the tower (based on the mass of the crude product) was measured to be 1600 ppm. In addition, the above process can make the operating life of the reaction distillation tower 400 reach 785 days, and the pressure drop of the whole tower is 8 kPa.

Example 4

Diphenylmethane diisocyanate was prepared using substantially the same raw materials and process as in Example 1, except that in step S2, the phosgene-containing mixture and the first reaction mixture were introduced into a kettle-type fully mixed flow reactor for a mixing reaction, and the temperature of the second reaction mixture obtained after the reaction was 117°C.

The total mass content of diamine hydrochloride and/or polyamine hydrochloride in the crude product discharged from the bottom of the tower (based on the mass of the crude product) was measured to be 8000 ppm. In addition, the above process can make the operating life of the reaction distillation tower 400 reach 200 days, and the pressure drop of the whole tower is 32 kPa.

Comparative Example 1

Diphenylmethane diisocyanate is prepared using substantially the same raw materials and processes as in Example 2, with the only difference being that in step S2, chlorobenzene at a temperature of -30°C and a pressure of 6 barg (instead of the phosgene-containing mixture in Example 2) is transported to the second reaction device 200 for heat exchange and mixing with the first reaction mixture.

The total mass content of diamine hydrochloride and/or polyamine hydrochloride in the crude product discharged from the bottom of the tower (based on the mass of the crude product) was measured to be 9500 ppm. In addition, the above process can make the operating life of the reactive distillation tower 400 reach 160 days, and the pressure drop of the whole tower is 40 kPa.

According to the description of each embodiment and comparative example, compared with comparative example 1, the embodiment of the present invention can reduce the content of impurities in the product, extend the operating life of the reaction distillation tower, and reduce the pressure drop of the whole tower by reacting the first reaction mixture obtained by reacting diamine and polyamine with phosgene at a relatively low temperature, thereby reducing the pressure drop of the whole tower. In addition, the above effects can be further enhanced by mixing the first reaction mixture with the phosgene-containing mixture in a jet reactor.

Unless otherwise defined, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

The embodiments described in the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Those skilled in the art may make various other substitutions, changes and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments, but is only limited by the claims.

Claims (10)

1.A process for the preparation of isocyanates, comprising the steps of:

reacting diamines and polyamines of the diphenylmethane series with phosgene to obtain a first reaction mixture;

mixing the first reaction mixture with a mixture containing phosgene to react to obtain a second reaction mixture; and

Subjecting the second reaction mixture to a decomposition reaction to produce the isocyanate;

Wherein the temperature of the first reaction mixture is higher than the temperature of the second reaction mixture, the temperature of the first reaction mixture is 40-150 ℃, and the temperature of the second reaction mixture is 20-120 ℃.

2. The method of claim 1, wherein the first reaction mixture is at a temperature of 80 to 95 ℃; and/or the number of the groups of groups,

The temperature of the second reaction mixture is 55-65 ℃; and/or the number of the groups of groups,

The first reaction mixture and/or the phosgene-containing mixture comprises an inert solvent selected from one or more of diethyl isophthalate, benzene, toluene, xylene, chlorobenzene and o-dichlorobenzene; and/or the number of the groups of groups,

The first reaction mixture and the mixture containing phosgene are subjected to heat exchange treatment firstly, and then mixed for reaction, wherein the temperature of the mixture containing phosgene is-30-20 ℃; and/or the number of the groups of groups,

Mixing the first reaction mixture with the phosgene-containing mixture in a jet reactor; and/or the number of the groups of groups,

The reaction of the second reaction mixture is carried out in a reactive distillation column.

3. The production method according to claim 2, wherein the phosgene-containing mixture is recovered from a reaction system for producing the isocyanate, and wherein the mass content of phosgene in the phosgene-containing mixture is 50 to 90%; and/or the number of the groups of groups,

The jet reactor comprises a heat exchange section, a throat jet section and a mixing section which are sequentially communicated; the heat exchange section is used for carrying out heat exchange treatment on the first reaction mixture and the phosgene-containing mixture, and the phosgene-containing mixture and the first reaction mixture subjected to heat exchange are discharged out of the jet reactor after being mixed and reacted in the mixing section through the throat jet section to obtain the second reaction mixture; and/or the number of the groups of groups,

The temperature of the tower bottom of the reactive rectifying tower is 150-210 ℃, the temperature of the tower top is 40-50 ℃, and the pressure of the tower top is 0.3-0.6 Mpag; and/or the number of the groups of groups,

The temperature of the mixture containing phosgene is-10-6 ℃.

4. The production method according to claim 3, wherein the mass content of phosgene in the phosgene-containing mixture is 80 to 85%; and/or the number of the groups of groups,

The mass ratio of the phosgene-containing mixture to the first reaction mixture is 1:5-1:10; and/or the number of the groups of groups,

The time for the first reaction mixture and/or the phosgene-containing mixture to exchange heat in the heat exchange section is 4-8 s; and/or the number of the groups of groups,

The material discharged from the heat exchange section flows through the throat jet section for 0.2-1 s; and/or the number of the groups of groups,

The retention time of the materials discharged from the throat jet section in the mixing section is 10-15 s; and/or the number of the groups of groups,

The heat exchange section comprises an inner pipe and an outer pipe, the inner pipe comprises a material cavity for containing materials, the inner pipe is arranged in the outer pipe, and a heat exchange cavity is formed between the pipe wall of the inner pipe and the pipe wall of the outer pipe; the first reaction mixture enters the throat jet section through the material cavity, and the phosgene-containing mixture enters the throat jet section through the heat exchange cavity; and/or the number of the groups of groups,

The throat jet section is an irregular circular tube, the longitudinal section of the throat jet section comprises two arcs which are oppositely arranged, and the distance between the tangent lines of the two arcs is equal to the minimum inner diameter of the throat jet section.

5. The method of claim 4, wherein the mass ratio of the phosgene-containing mixture to the first reaction mixture is in the range of 1:6 to 1:6.5; and/or the number of the groups of groups,

The inner diameter of the inner tube of the heat exchange section is larger than the minimum inner diameter of the throat jet section; the mixing section is a circular tube, and the inner diameter of the mixing section is larger than the minimum inner diameter of the throat jet section; and/or the number of the groups of groups,

The two arcs are respectively positioned at two sides of the axis of the longitudinal section; and/or the number of the groups of groups,

Separating the second reaction mixture to obtain a decomposition reaction gas-phase material and a decomposition reaction liquid-phase material; the reaction rectifying tower comprises a tower kettle and a tower top, the decomposition reaction gas-phase material is introduced into the reaction rectifying tower from a gas feed port, and the decomposition reaction liquid-phase material is introduced into the tower kettle; the distance between the gas feeding port and the tower bottom is larger than the distance between the gas feeding port and the tower top.

6. The method of claim 5, wherein the ratio of the minimum inner diameter of the throat jet section to the inner diameter of the mixing section is 1:6 to 1:10; and/or the number of the groups of groups,

The mass ratio of the decomposition reaction gas-phase material to the decomposition reaction liquid-phase material is 1:2-1:3.

7. A system for preparing isocyanate, comprising:

The first reaction device is used for reacting diamine and polyamine of diphenylmethane series with phosgene to obtain a first reaction mixture;

The second reaction device is used for mixing the first reaction mixture with a mixture containing phosgene for reaction to obtain a second reaction mixture; and

The reaction rectifying tower is used for carrying out decomposition reaction on the second reaction mixture to prepare isocyanate;

Wherein the second reaction device is a jet reactor.

8. The preparation system of claim 7, wherein the jet reactor comprises a heat exchange section, a throat jet section and a mixing section in sequential communication; the heat exchange section comprises an inner pipe and an outer pipe, the inner pipe comprises a material cavity for containing materials, the inner pipe is arranged in the outer pipe, and a heat exchange cavity is formed between the pipe wall of the inner pipe and the pipe wall of the outer pipe;

The throat jet section is an irregular circular tube, the longitudinal section of the throat jet section comprises two arcs which are oppositely arranged, and the distance between the tangent lines of the two arcs is equal to the minimum inner diameter of the throat jet section; and/or the number of the groups of groups,

The preparation system further comprises a phase separation device, which is used for separating the second reaction mixture to obtain a decomposition reaction gas-phase material and a decomposition reaction liquid-phase material; the reactive distillation tower comprises a tower top, a tower kettle and a tower body connected with the tower top and the tower kettle, wherein a gas feed inlet and a phosgene discharge outlet are arranged on the tower body.

9. The preparation system of claim 8, wherein a ratio of a minimum inner diameter of the throat jet section to an inner diameter of the mixing section is 1:6 to 1:10; and/or the number of the groups of groups,

The two arcs are respectively positioned at two sides of the axis of the longitudinal section; and/or the number of the groups of groups,

The preparation system further comprises a heat exchange device which is respectively connected with the phosgene discharge port of the reaction rectifying tower and the heat exchange cavity of the second reaction device; and/or the number of the groups of groups,

The distance between the gas feed inlet and the tower kettle is greater than the distance between the gas feed inlet and the tower top; the phase splitting device comprises a gas outlet and a liquid outlet, the gas outlet is connected with a gas feeding port of the reactive distillation tower, and the liquid outlet is connected with the tower kettle.

10. The jet reactor is characterized by comprising a heat exchange section, a throat jet section and a mixing section which are sequentially communicated; the heat exchange section comprises an inner pipe and an outer pipe, wherein the inner pipe comprises a material cavity for containing materials, the inner pipe is arranged in the outer pipe, and a heat exchange cavity is formed between the pipe wall of the inner pipe and the pipe wall of the outer pipe; the heat exchange cavity and the material cavity are communicated with the throat jet section;

The heat exchange section and the mixing section are round pipes, the throat jet section is an irregular round pipe, the longitudinal section of the throat jet section comprises two arcs which are oppositely arranged, and the distance between the tangents of the two arcs is equal to the minimum inner diameter of the throat jet section; the inner diameter of the inner tube of the heat exchange section and the inner diameter of the mixing section are larger than the minimum inner diameter of the throat jet section.