A method for preparing isocyanate by combining a supercritical phosgenation method with a piping method

Abstract

This application relates to a method for preparing isocyanates. Specifically, this application provides a method for preparing isocyanates by combining a supercritical phosgenation method with a piping method.

Description

Technical Field

[0001]

[0001] This application relates to a method for preparing isocyanates, specifically, a method for preparing isocyanates by combining a supercritical phosgenation method with a piping method.

Background Art

[0002]

[0002] Isocyanates are a class of compounds containing one or more isocyanate groups, including aliphatic isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorus-containing isocyanates, inorganic isocyanates, blocked isocyanates, and the like. Due to the highly unsaturated isocyanate groups contained therein, these are chemically highly reactive and can undergo important chemical reactions with many substrates. Therefore, isocyanates are widely used in polyurethanes, polyurethane-ureas, polyureas, polymer modification, reagents for organic synthesis, agriculture, medicine, and other fields.

[0003]

[0003] In the prior art, the principle of preparing isocyanates from phosgene and amines is well known. Due to the high reactivity of amines (especially aliphatic diamines), amines that have not yet participated in the reaction may react with reaction products and intermediates during the phosgenation reaction to produce by-products such as amine hydrochlorides, ureas, and biurets. To avoid the formation of by-products, capping reagents (such as HCl) are selected to protect the amino groups (-NH2) of the amines and form amine salts. However, the reactivity of amine salts is much lower than that of free amines, and amine salts are almost insoluble in any common organic solvent and can only be dispersed in the solvent. The phosgenation reaction using amine salts as raw materials generally requires the use of a large amount of solvent as a dispersant, and the content of amine salts in the solvent is often less than 10%, and the residence time of the phosgenation reaction is often several hours, or even more than 10 hours, as proven by practice.

Summary of the Invention

Problems to be Solved by the Invention

[0004]

[0004] Therefore, there is still a need for an optimized method for preparing isocyanate.

Means for Solving the Problems

[0005]

[0005] The present application aims to provide a method for preparing isocyanate, specifically, a method for preparing isocyanate by combining a supercritical phosgenation method with a piping method.

[0006]

[0006] In one aspect, the present application is a method for preparing isocyanate, comprising the following steps: (a) mixing a reactant amine stream and a phosgene stream at a temperature of -5 to 5 °C to obtain a mixture of the reactant amine and phosgene; (b) adjusting the temperature of the mixture obtained in step (a) to 182 °C to 205 °C so that phosgene is in a supercritical state, and reacting in a supercritical reactor for at least 15 minutes; (c) reacting the reaction product mixture obtained in step (b) under reduced pressure conditions for a reaction time of 30 seconds or less.

[0007]

[0007] In some embodiments, the reduced pressure in step (c) is carried out in a decompression reactor. For example, step (c) is a step of introducing the reaction product mixture from the supercritical reactor of step (b) to a decompression reactor for the reaction.

[0008]

[0008] In some embodiments, the method further comprises step (d): recovering the product. In some embodiments, step (d) comprises setting a quench zone at the outlet of the decompression reactor, contacting the reaction product mixture obtained in step (c) with a quench medium stream introduced into the quench zone, and reducing the temperature of the reaction product mixture obtained in step (c) to 170 °C or less.

[0009]

[0009] In some embodiments, the method further comprises step (e): purifying the product. In some embodiments, step (e) comprises: 1) introducing the reaction product mixture obtained in step (c) or step (d) into a degassing column, where hydrogen chloride and phosgene in the reaction product mixture overflow from the upper part of the degassing column and enter a hydrogen chloride / phosgene separation column, and the hydrogen chloride overflowing from the upper part of the separation column is purified by a tail gas removal treatment unit to produce by-product hydrochloric acid; 2) recovering phosgene from the bottom of the separation column in the lower step 1) for reuse and forming a phosgene stream in step (a); 3) recovering isocyanate and by-products in the reaction product mixture from the bottom of the degassing column in the lower step 1) and passing the isocyanate and by-products through a light component removal column to remove light component by-products; 4) recovering isocyanate and heavy component by-products from the bottom of the light component removal column in the lower step 3), passing the isocyanate and heavy component by-products through a purification column, recovering isocyanate from the purification column, and removing heavy component by-products.

[0010]

[0010] In some embodiments, the light component by-products in the lower step 3) are selected from the group consisting of piperidine, multiple hydropyridines, and combinations thereof. In some embodiments, the heavy component by-products in the lower step 4) are selected from the group consisting of tar, PDI polymer, by-product urea, and any combination thereof.

[0011]

[0011] In some embodiments, step (a) is performed before step (b) and step (c).

[0012] In some embodiments, no organic solvent is used in each of step (a), step (b), and step (c).

[0012]

[0013] In some embodiments, the reactant amine stream and the phosgene stream are mixed in a supercritical reactor in step (a).

[0014] In some embodiments, the mixed reactant amine stream and phosgene stream form suspended particles by shear emulsification. In some embodiments, the shear emulsification is carried out in a supercritical reactor.

[0013]

[0015] In some embodiments, the suspended particles have a diameter of 100 μm or less. In some embodiments, the suspended particles have a diameter of 50 μm or less. In some embodiments, the suspended particles have a diameter of 20 μm or less.

[0014]

[0016] In some embodiments, the reactant amine stream and the phosgene stream pass through a homogenization pump for uniform shear emulsification in step (a). In some embodiments, the uniform shear emulsification is achieved by controlling the lift, rotational speed, torque, suction, and / or shear homogenization time of the homogenization pump. In some embodiments, the circulating output volume of the homogenization pump is controlled to be 10 times or more the volume of the liquid hold-up in the supercritical reactor.

[0015]

[0017] In some embodiments, the phosgene stream in step (a) is stoichiometrically in excess compared to the amino groups of the reactant amine stream.

[0018] In some embodiments, the feed ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is 7:1 to 25:1. In some embodiments, the feed ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is 10:1 to 20:1. In some embodiments, the feed ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is 12:1.

[0016]

[0019] In some embodiments, the phosgene stream in step (a) exists in liquid form.

[0020] In some embodiments, the reaction temperature in step (c) is from 150°C to 450°C. In some embodiments, the reaction temperature in step (c) is from 200°C to 400°C. In some embodiments, the reaction temperature in step (c) is from 250°C to 350°C.

[0017]

[0021] In some embodiments, the reaction pressure in step (c) is from 15 KPa to 500 KPa. In some embodiments, the reaction pressure in step (c) is from 50 KPa to 300 KPa. In some embodiments, the reaction pressure in step (c) is from 50 KPa to 110 KPa. In some embodiments, the reaction pressure in step (c) is from 80 KPa to 100 KPa.

[0018]

[0022] In some embodiments, the residence time during the reaction in step (c) is from 0.5 second to 30 seconds. In some embodiments, the residence time during the reaction in step (c) is from 1.5 seconds to 20 seconds. In some embodiments, the residence time during the reaction in step (c) is from 2.5 seconds to 10 seconds.

[0019]

[0023] In some embodiments, in step (d), the product recovery temperature is 170°C or lower. In some embodiments, in step (d), the product recovery temperature is from 80°C to 150°C. In some embodiments, in step (d), the product recovery temperature is from 110°C to 140°C.

[0020]

[0024] In some embodiments, in step (d), the temperature of the reaction product mixture obtained in step (c) is rapidly decreased by utilizing the latent heat of vaporization of the quench medium. In some embodiments, the quench medium in step (d) is selected from the group consisting of an organic solvent, an isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof. In some embodiments, the organic solvent is selected from the group consisting of dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof. In some embodiments, the quench medium in step (d) is a liquid. In some embodiments, the quench medium in step (d) is liquid phosgene.

[0021]

[0025] In some embodiments, the vacuum reactor is a tubular reactor. In some embodiments, the inner diameter of the pipe in the vacuum reactor is 4 to 9 mm.

[0026] In some embodiments, the isocyanate is a diisocyanate. In some embodiments, the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate. In some embodiments, the isocyanate is selected from the group consisting of methylene diphenyl diisocyanate as a pure isomer or a mixture of isomers, toluene diisocyanate as a pure isomer or a mixture of isomers, 2,6-xylyl isocyanate, 1,5-naphthalene diisocyanate, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, t-butyl isocyanate, pentyl isocyanate (e.g., pentamethylene diisocyanate), t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexamethylene diisocyanate), cyclopentyl isocyanate, cyclohexyl isocyanate, and phenyl isocyanate (e.g., p-phenylene diisocyanate).

[0022]

[0027] In some embodiments, the isocyanate is pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or methylcyclohexane diisocyanate (HTDI). In some embodiments, the reactant amine has the structural formula R(NH2) n (wherein n is 1, 2, or 3 and R is an aliphatic or aromatic hydrocarbyl group). In some embodiments, n is 2 and R is an aliphatic hydrocarbyl group. In some embodiments, n is 2 and R is an aliphatic hydrocarbyl group having 2 to 10 carbon atoms. In some embodiments, n is 2 and R is a linear or cyclic aliphatic hydrocarbyl group having 3 to 10 carbon atoms).

[0023]

[0028] In some embodiments, the reactant amine is present in free form.

[0029] In some embodiments, the reactant amine is present as an amine salt. In some embodiments, the amine salt is selected from the group consisting of hydrochloride, sulfate, bisulfate, nitrate, and carbonate.

[0024]

[0030] In some embodiments, the reactant amine is one or more selected from the group consisting of ethylamine, butylamine, pentamethylenediamine, hexamethylenediamine, 1,4-diaminobutane, 1,8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 1,5-naphthalenediamine, diphenylmethanediamine, dicyclohexylmethanediamine, m-cyclohexyldimethylenediamine, isophoronediamine, methylcyclohexanediamine, and trans-1,4-cyclohexanediamine.

[0025]

[0031] In some embodiments, the reactant amine is selected from the group consisting of PDA, PDA hydrochloride, HDA, HDA hydrochloride, IPDA, IPDA hydrochloride, HTDA, and HTDA hydrochloride.

[0026]

[0032] The above and other features of the present application will be more fully and clearly understood from the following description in combination with the drawings and the appended claims. It should be understood that these drawings only depict some embodiments of the disclosure of the present application and should not be considered as limiting the scope of the disclosure of the present application. The disclosure of the present application will be described more clearly and in detail with reference to the drawings.

Brief Description of the Drawings

[0027]

Figure 1

[0033] It is a diagram showing a schematic flowchart of a method for adjusting isocyanate according to an embodiment of the present application, where 01 is a supercritical reactor, 02 is a vacuum reactor, 03 is a quencher, 04 is a degassing tower, 05 is a phosgene / hydrogen chloride separation tower, 06 is a light component removal tower, and 07 is a product purification tower.

Modes for Carrying Out the Invention

[0028]

[0034] The exemplary embodiments described in the detailed description, the drawings, and the claims are not intended to be limiting. Without departing from the spirit or scope of the subject matter of the present application, other embodiments may be adopted and other changes may be made. The various aspects of the disclosure of the present application generally described herein and illustrated diagrammatically in the drawings can be configured, substituted, combined, and designed in various different configurations, and it can be understood that all of these are clearly part of the content of the present application.

[0029]

[0035] In an aspect, the present application is a method for preparing isocyanate, comprising the following steps: (a) mixing a reactant amine stream and a phosgene stream at a temperature of -5 to 5°C to obtain a mixture of the reactant amine and phosgene; (b) Adjust the temperature of the mixture obtained in step (a) to 182°C to 205°C so that phosgene is in a supercritical state, and react in a supercritical reactor for at least 15 minutes; (c) Provide a method including the step of reacting the reaction product mixture obtained in step (b) under reduced pressure conditions for a reaction time of 30 seconds or less.

[0030]

[0036] As used herein, "isocyanate" refers to a class of compounds containing one or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) isocyanate groups (R-N=C=O), including aliphatic isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorus-containing isocyanates, inorganic isocyanates, and blocked isocyanates. In some embodiments, the isocyanate in the present application is a diisocyanate. In some embodiments, the isocyanate in the present application is an aliphatic diisocyanate or an aromatic diisocyanate. In some embodiments, the isocyanate in the present application includes an aromatic isocyanate or an aliphatic isocyanate. For example, aromatic isocyanates include methylene diphenyl diisocyanate as a pure isomer or a mixture of isomers, toluene diisocyanate as a pure isomer or a mixture of isomers, 2,6-xylyl isocyanate, 1,5-naphthalene diisocyanate, etc. Aliphatic isocyanates include methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, t-butyl isocyanate, pentyl isocyanate, t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, etc. In some embodiments, the isocyanate in the present application is selected from the group consisting of pentane diisocyanate, hexane diisocyanate, p-phenylene diisocyanate, and toluene diisocyanate. In some embodiments, the isocyanate in the present application is pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or methylcyclohexane diisocyanate (HTDI).

[0031]

[0037] Steps (a), (b), (c), and optional steps (d) and (e) of the method for preparing isocyanate according to this application are described in detail below.

[0032]

[0038] 1. Step (a)

[0039] In step (a) of this application, the reactant amine stream and the phosgene stream are mixed at a temperature of -5 to 5 °C to obtain a mixture of the reactant amine and phosgene.

[0033]

[0040] As used herein, "reactant amine" refers to a compound having an amino (-NH2) group as a starting material for preparing isocyanate. In some embodiments, the reactant amine has the structural formula R(NH2) n (wherein n is 1, 2, or 3, and R is an aliphatic or aromatic hydrocarbyl group). In some embodiments, n is 2 and R is an aliphatic hydrocarbyl group. In some embodiments, n is 2 and R is an aliphatic, alicyclic, or aromatic hydrocarbyl group having 2 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms). In some embodiments, n is 2 and R is a linear or cyclic aliphatic hydrocarbyl group having 3 to 10 carbon atoms (e.g., 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms).

[0034]

[0041] In some embodiments, the reactant amine is a primary amine, i.e., having one NH2 group. In some embodiments, the reactant amine is a diamine, i.e., having two NH2 groups. In some embodiments, the reactant amine is one or more selected from the group consisting of ethylamine, butylamine, pentamethylenediamine, hexamethylenediamine, 1,4-diaminobutane, 1,8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 1,5-naphthalenediamine, diphenylmethanediamine, dicyclohexylmethanediamine, m-cyclohexyldimethylenediamine, isophoronediamine, methylcyclohexanediamine, and trans-1,4-cyclohexanediamine. In some embodiments, the reactant amine is selected from the group consisting of pentamethylenediamine (e.g., 1,5-pentamethylenediamine), hexamethylenediamine (e.g., 1,6-hexamethylenediamine), p-phenylenediamine, isophoronediamine, methylcyclohexanediamine, and toluenediamine. In some embodiments, the reactant amine is pentamethylenediamine (PDA).

[0035]

[0042] In some embodiments, the reactant amine exists in a free form. The term "free" refers to an amine compound in a non-salt form. The amine compound in the free form may be different from amine compounds in various salt forms in terms of some physical and / or chemical properties, for example, solubility in polar solvents. The amine compound in the free form may also be the same or similar to amine compounds in various salt forms in terms of some physical and / or chemical properties.

[0036]

[0043] In some embodiments, the reactant amine exists as an amine salt. In some embodiments, the amine salt is selected from the group consisting of hydrochloride, sulfate, bisulfate, nitrate, and carbonate.

[0037]

[0044] In some embodiments, the reactant amine is one or more selected from the group consisting of pentamethylenediamine (PDA), PDA hydrochloride, hexamethylenediamine (HDA), HDA hydrochloride, isophoronediamine (IPDA), IPDA hydrochloride, methylcyclohexanediamine (HTDA), and HTDA hydrochloride.

[0038]

[0045] In conventional methods for preparing isocyanates, an organic solvent is commonly used to disperse the reactant amine, or an inert carrier gas (e.g., nitrogen, carbon dioxide, carbon monoxide, helium, or argon) is used to facilitate the vaporization of the reactant amine and achieve a more suitable dispersion effect. However, in the present invention, the inventors unexpectedly found that it is not necessary to use either an organic solvent or an inert carrier gas when mixing the reactant amine and phosgene in step (a). In some embodiments, the reactant amine stream and the phosgene stream are mixed within a supercritical reactor (e.g., both are introduced into and mixed within a supercritical reactor). In some embodiments, the reactant amine stream and the phosgene stream are mixed outside the supercritical reactor, i.e., they are mixed within another vessel or pipeline before being introduced into the supercritical reactor. To facilitate the mixing of the reactant amine stream and the phosgene stream and promote the subsequent reaction, in step (a), the reactant amine stream and the phosgene stream are mixed and then shear-emulsified to form suspended particles. In some embodiments, the suspended particles have a diameter of, for example, 100 μm or less, or 50 μm or less, or 20 μm or less. In some specific embodiments, the diameter of the suspended particles is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm, or in a range between any two of the above values. Without being limited by any theory, it is believed that the smaller the diameter of the formed suspended particles, the more it helps the subsequent reaction between the reactant amine and phosgene.

[0039]

[0046] In step (a), after the reactant amine stream and the phosgene stream are mixed, they can be shear-emulsified by any method known in the art. For example, the reactant amine and phosgene can be uniformly shear-emulsified by mechanical shearing using a high-speed shear emulsifier, a high-gravity mixer, a homogenizing pump, etc. In some embodiments, the reactant amine stream and the phosgene stream are mixed and then uniformly shear-emulsified by a homogenizing pump. In some embodiments, the shear-emulsification is carried out in a supercritical reactor. The homogenizing pump used in this application is a commercially available one such as the DHX homogenizing pump purchased from Ningbo Durrex Pump Industry Co., Ltd.

[0040]

[0047] The homogenizing pump can be installed inside the supercritical reactor (referred to as an "internal homogenizing pump" in this situation) or outside the supercritical reactor (referred to as an "external homogenizing pump" in this situation). In some embodiments of this application, the homogenizing pump is an internal homogenizing pump. When an internal homogenizing pump is used, uniform shear-emulsification can preferably be achieved by those skilled in the art by controlling the lift, rotational speed, torque, suction, and / or shear homogenization time of the homogenizing pump. Specific values can be determined by the size of the supercritical reactor and / or the experience of those skilled in the art. In some embodiments, the rotational speed of the internal homogenizing pump is set to 1000 - 3000 r / min (for example, 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, 2200 r / min, 2300 r / min, 2400 r / min, 2500 r / min, 2600 r / min, 2700 r / min, 2800 r / min, 2900 r / min, 3000 r / min, or any value or range between any two of the above values). In some embodiments, the flow rate of the internal homogenizing pump is 120 - 250 m 3 / h (for example, 120 m 3 / h, 130 m 3 / h, 140 m 3 / h, 150 m 3 / h, 160 m 3 / h, 170 m 3 / h, 180 m 3 / h, 190 m 3 / h, 200 m 3 / h, 210 m 3 / h, 220 m 3 / h, 230 m 3 / h, 240 m 3 / h, 250 m 3 / h, or any value or range between any two of the above values) is set. In some embodiments, the pressure of the internal homogenization pump is set to 0.1 - 1.2 MPa (e.g., 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, or any value or range between any two of the above values). In some embodiments, the inlet of the internal homogenization pump is set to 80 mm - 110 mm (e.g., 85 mm, 90 mm, 95 mm, 96 mm, 97 mm, 98 mm, 99 mm, 100 mm, 105 mm, 110 mm, or any value or range between any two of the above values). In some embodiments, the outlet of the internal homogenization pump is set to 60 mm - 90 mm (e.g., 65 mm, 70 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm, 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 90 mm, or any value or range between any two of the above values).

[0041]

[0048] Without being limited by any theory, when the circulation output volume of the internal homogenization pump is n times the liquid hold-up in the supercritical reactor, the internal homogenization pump is considered to have performed at least n times the shear emulsification on the reactant amine and phosgene therein. For example, when the circulation output volume of the internal homogenization pump is 10 times the liquid hold-up in the supercritical reactor, the internal homogenization pump has performed 10 times the shear emulsification on the reactant amine and phosgene therein. In some embodiments, the circulation output volume of the internal homogenization pump that is more than 10 times the liquid hold-up in the supercritical reactor is used as a criterion for determining whether uniform shear emulsification has been achieved. For example, when the circulation output volume of the internal homogenization pump is more than 10 times the liquid hold-up in the supercritical reactor (e.g., the circulation output volume of the internal homogenization pump is 11 times, 12 times, 13 times, 14 times, 15 times, 16 times, 17 times, 18 times, 19 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times, 50 times, or more), the mixture of the reactant amine and phosgene is determined to achieve uniform shear emulsification.

[0042]

[0049] In some embodiments, the homogenization pump is an external homogenization pump. The homogenization pump is installed outside the supercritical reactor, and the mixture after shear emulsification is directly transported from the outlet of the homogenization pump to the supercritical reactor. When an external homogenization pump is used, uniform shear emulsification can be achieved by those skilled in the art by controlling the type and rotational speed of the external homogenization pump, as well as the residence time of the substance in the external homogenization pump. In some embodiments, the rotational speed of the external homogenization pump is set to 1000 - 3000 r / min (for example, 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, 2200 r / min, 2300 r / min, 2400 r / min, 2500 r / min, 2600 r / min, 2700 r / min, 2800 r / min, 2900 r / min, 3000 r / min, or any value or range between any two of the above values). In some embodiments, the flow rate of the external homogenization pump is 120 - 250 m 3 / h (for example, 120 m 3 / h, 130 m 3 / h, 140 m 3 / h, 150 m 3 / h, 160 m 3 / h, 170 m 3 / h, 180 m 3 / h, 190 m 3 / h, 200 m 3 / h, 210 m 3 / h, 220 m 3 / h, 230 m 3 / h, 240 m 3 / h, 250 m 3 / h, or any value or range between any two of the above values). In some embodiments, the pressure of the external homogenization pump is set to 0.1 to 1.2 MPa (e.g., 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, or any value or range between any two of the above values). In some embodiments, the inlet of the external homogenization pump is set to 80 mm to 110 mm (e.g., 85 mm, 90 mm, 95 mm, 96 mm, 97 mm, 98 mm, 99 mm, 100 mm, 105 mm, 110 mm, or any value or range between any two of the above values). In some embodiments, the outlet of the external homogenization pump is set to 60 mm to 90 mm (e.g., 65 mm, 70 mm, 75 mm, 76 mm, 77 mm, 78 mm, 79 mm, 80 mm, 81 mm, 82 mm, 83 mm, 84 mm, 85 mm, 90 mm, or any value or range between any two of the above values).

[0043]

[0050] The "supercritical reactor" in the present application refers to a reactor that can bring the reactants into a supercritical state or in which the reaction is carried out in a supercritical medium. To ensure a supercritical reaction, parameters such as the pressure and temperature therein can be adjusted according to the reaction requirements (e.g., the types and properties of the reactants, etc.). The supercritical reactor used in the present invention can be any commercially available supercritical reactor such as the L-series high-temperature and high-pressure supercritical reactor purchased from Shanghai Labe Scientific Instrument Co., Ltd.

[0044]

[0051] In step (a), the reactant amine stream can be supplied to the supercritical reactor as a single sub-stream containing the reactant amine or as a plurality of sub-streams (e.g., two, three, four, five, or more) containing the reactant amine. Similarly, in step (a), the phosgene stream can be supplied to the supercritical reactor as a single sub-stream containing phosgene or as a plurality of sub-streams (e.g., two, three, four, five, or more) containing phosgene. When the reactant amine stream (or phosgene stream) is supplied to the supercritical reactor as a plurality of sub-streams containing the reactant amine (or phosgene) in step (a), the plurality of sub-streams can be supplied to the supercritical reactor at the same position or at different positions.

[0045]

[0052] The process for preparing isocyanates often requires the addition of a large amount of excess phosgene because if the phosgene concentration is insufficient, the generated isocyanate reacts with the excess amine to produce urea or other high-viscosity solid by-products. Therefore, it is preferred to provide excess phosgene to prevent the formation of by-products. For example, in some embodiments, the phosgene stream in step (a) is stoichiometrically in excess compared to the amino groups of the reactant amine stream. For example, the molar ratio of phosgene to the amino groups of the reactant amine is generally from 1.1:1 to 50:1 (e.g., 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 11:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, and ranges between any two of the above values). In some embodiments, in a supercritical reactor, phosgene is used in a stoichiometrically excess amount compared to the amino groups of the reactant amine, which is 0% to 250% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, or 250%, etc.) higher than the theoretical value. When the reactant amine stream (and / or phosgene stream) in step (a) is fed to the supercritical reactor in a plurality of sub-streams containing the reactant amine (and / or phosgene), the total phosgene stream resulting from the sum of the plurality of sub-streams containing phosgene is stoichiometrically in excess compared to the amino groups of the total reactant amine stream resulting from the sum of the plurality of sub-streams containing the reactant amine.

[0046]

[0053] In some embodiments, the feed ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is from 7:1 to 25:1 (for example, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, or any value between any two of the above ratios). Preferably, the feed ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is from 10:1 to 20:1.

[0047]

[0054] In step (a), the phosgene contained in the phosgene stream can be fresh phosgene or recycled phosgene. The term "fresh phosgene" refers to a stream containing phosgene that has not been regenerated from the phosgenation process and has not passed through any reaction stage involved in the phosgenation reaction, usually after synthesizing phosgene from chlorine and carbon monoxide. The term "recycled phosgene" refers to a stream containing phosgene recovered from the tail gas of the reaction for preparing isocyanate by phosgenation. As described above, in the process of preparing isocyanate by the gas-phase method, excess phosgene is often required. Therefore, a large amount of phosgene exists in the reaction tail gas, and by regenerating the phosgene in the tail gas, the purpose of reducing the production cost can be achieved. In some embodiments, the phosgene stream in step (a) exists in liquid form.

[0048]

[0055] In some embodiments, the reactant amine stream and the phosgene stream in step (a) are mixed at a low temperature, for example, any temperature between -5 °C and 5 °C, such as -5 °C, -4 °C, -3 °C, -2 °C, -1 °C, 0 °C, 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, or any value between any two of the above values. The mixing can be carried out at any constant temperature between -5 °C and 5 °C, or at a fluctuating temperature between -5 °C and 5 °C. In one embodiment, the mixing is carried out at a constant temperature of 0 °C.

[0049]

[0056] In some embodiments, step (a) is carried out before step (b) and step (c). That is, the reactant amine and phosgene are mixed before the reaction, and then they are heated together and reacted. One of the advantages of this operation is to prevent the reactant amine (e.g., amine salt) from decomposing or self-cyclizing at high temperature to produce by-products.

[0050]

[0057] 2. Step (b)

[0058] In step (b) of the present application, the temperature of the mixture obtained in step (a) is adjusted to 182°C to 205°C so that phosgene is in a supercritical state, and the reaction is carried out in a supercritical reactor for at least 15 minutes.

[0051]

[0059] For example, pentamethylenediamine hydrochloride and phosgene are used as starting materials, and the main reaction in step (b) is as follows:

[0052]

Chemical formula

[0060] In some embodiments, in step (b), the temperature in the supercritical reactor is adjusted to 182 - 205°C so that phosgene is in a supercritical state, and then the reactant amine is reacted with phosgene for 15 minutes or more.

[0053]

[0061] The "supercritical state" in the present application refers to a state where the temperature and pressure of a fluid are raised to a temperature higher than the critical temperature and a pressure higher than the critical pressure, resulting in the fluid being in a state between a gas and a liquid. Many physical and chemical properties of substances in the supercritical state are between those of a gas and a liquid, and have both advantages such as high solubility, good diffusivity, and easy control. It not only has a solubility and heat transfer coefficient similar to those of a liquid, but also has a viscosity and diffusivity coefficient similar to those of a gas. For example, the critical temperature of phosgene is 182°C and the critical pressure is 5.674 MPa. When the temperature of phosgene is 182°C or higher and the pressure is 5.674 MPa or higher, phosgene is in a supercritical state.

[0054]

[0062] Generally, amine salts are almost insoluble in any common organic solvent and can only be dispersed in the solvent. The inventors of the present application unexpectedly found that phosgene in a supercritical state can dissolve the reactant amine (especially amine salts), and phosgene in a supercritical state can be reacted with the reactant amine. Phosgene in a supercritical state not only serves as a solvent for the reactant amine but also serves as a starting material for the reaction. Therefore, no other solvent is required to dissolve the reactant amine, and the reaction rate is greatly improved. Furthermore, when the reactant amine is an amine salt (for example, PDA hydrochloride), it is also possible to efficiently avoid the deterioration of cyclization in the heating process of only the amine salt. In some embodiments, in step (b) of the present application, no organic solvent is used.

[0055]

[0063] In some embodiments, step (b) is carried out under supercritical phosgenation reaction conditions at a pressure of ≥ 5 MPa (e.g., 5.1 MPa, 5.2 MPa, 5.3 MPa, 5.4 MPa, 5.5 MPa, 5.6 MPa, 5.7 MPa, 5.8 MPa, 5.9 MPa, 6 MPa, 6.1 MPa, 6.2 MPa, 6.3 MPa, 6.4 MPa, 6.5 MPa, 6.6 MPa, 6.7 MPa, 6.8 MPa, 6.9 MPa, 7 MPa, 7.5 MPa, 8 MPa, 8.1 MPa, 8.2 MPa, 8.3 MPa, 8.4 MPa, 8.5 MPa, 8.6 MPa, 8.7 MPa, 8.8 MPa, 8.9 MPa, 9 MPa, 9.1 MPa, 9.2 MPa, 9.3 MPa, 9.4 MPa, 9.5 MPa, 9.6 MPa, 9.7 MPa, 9.8 MPa, 9.9 MPa, 10 MPa, 11 MPa, 12 MPa, or higher) and a temperature between 182°C and 205°C (e.g., 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C, 190°C, 191°C, 192°C, 193°C, 194°C, 195°C, 196°C, 197°C, 198°C, 199°C, 200°C, 201°C, 202°C, 203°C, 204°C, 205°C, or any value between any two of the above values). In some embodiments, in step (b), the reaction pressure is 5.2 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.2 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.3 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.4 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.5 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.6 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.7 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 6.9 MPa and the reaction temperature is 182°C. In some embodiments, in step (b), the reaction pressure is 7 MPa and the reaction temperature is 182°C.In some embodiments, in step (b), the reaction pressure is 7.8 MPa and the reaction temperature is 182 °C. In some embodiments, in step (b), the reaction pressure is 8.4 MPa and the reaction temperature is 182 °C.

[0056]

[0064] In some embodiments, in step (b), to ensure sufficient reaction between the reactant amine and phosgene, their reaction continues for 15 minutes or more, for example, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, or any value between any two of the above values. In some embodiments, the reaction between the reactant amine and phosgene in step (b) continues for 20 minutes. In some embodiments, the reaction between the reactant amine and phosgene in step (b) continues for 30 minutes or more, for example, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes, 40 minutes, or any value between any two of the above values.

[0057]

[0065] 3. Step (c)

[0066] In step (c) of the present application, the reaction product mixture obtained in step (b) is reacted under reduced pressure for 30 seconds or less.

[0058]

[0067] For example, pentamethylenediamine hydrochloride and phosgene are used as starting materials, and the main reaction in step (c) is as follows:

[0059]

Chemical formula

[0068] The reaction product mixture generated after step (b) contains an acyl chloride intermediate, unreacted reactant amine, and phosgene. Step (c) is a step of decomposing the acyl chloride intermediate to produce isocyanate. The applicant has unexpectedly found that the decomposition of acyl chloride under reduced pressure can significantly shorten the preparation time of isocyanate and solve the problem of high supercritical reaction pressure. In the conventional method for preparing isocyanate using phosgene, the residence time during the phosgenation reaction is several hours or even longer than 10 hours, and the pressure may reach 9 - 10 MPa. In the method of the present application, by combining the supercritical phosgenation reaction (i.e., step (b)) and the reaction under reduced pressure (i.e., step (c)), the preparation time of isocyanate may be shortened to less than 30 minutes, and the pressure may also be reduced to 6 - 8 MPa.

[0060]

[0069] In some embodiments, the reaction pressure in step (c) is 15 KPa - 500 KPa, for example, 15 KPa, 50 KPa, 60 KPa, 70 KPa, 80 KPa, 90 KPa, 100 KPa, 110 KPa, 120 KPa, 130 KPa, 140 KPa, 150 KPa, 200 KPa, 210 KPa, 220 KPa, 230 KPa, 240 KPa, 250 KPa, 260 KPa, 270 KPa, 280 KPa, 290 KPa, 300 KPa, 310 KPa, 320 KPa, 330 KPa, 340 KPa, 350 KPa, 400 KPa, 450 KPa, 500 KPa, or any value between any two of the above values. In some embodiments, the reaction pressure in step (c) is 50 KPa - 300 KPa. In some embodiments, the reaction pressure in step (c) is 50 KPa - 140 KPa. In some embodiments, the reaction pressure in step (c) is 50 KPa - 110 KPa. In some embodiments, the reaction pressure in step (c) is 70 KPa - 150 KPa.

[0061]

[0070] There are many ways to achieve reduced pressure in step (c). In some embodiments, step (c) is a step of introducing the reaction product mixture from the supercritical reactor in step (b) to a decompression reactor for the reaction. For example, after step (b) is completed, the valve between the supercritical reactor and the decompression reactor is opened so that the reaction product mixture in step (b) is introduced into the decompression reactor for the reaction. In some embodiments, the decompression reactor is a tubular reactor (e.g., a tubular decompression reactor). A tubular reactor is a type of continuous operation reactor that has a tubular shape and a large length-to-diameter ratio. The length of the tubular reactor is flexible and is characterized by achieving continuity and reaction without backmixing. In some embodiments, the inner diameter of the pipe in the decompression reactor is 4 to 9 mm (e.g., 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, or any value between any two of the above values).

[0062]

[0071] In some embodiments, before introducing the reaction product mixture into the decompression reactor, the decompression reactor is preheated to the temperature required for the reaction in this step (i.e., the acyl chloride decomposition reaction). In some embodiments, the reaction temperature in step (c) is 150 to 450 °C, for example, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, 410 °C, 420 °C, 430 °C, 440 °C, 450 °C, or any value between any two of the above values. Preferably, the reaction temperature in step (c) is 200 °C to 400 °C. More preferably, the reaction temperature in step (c) is 250 °C to 350 °C. In some embodiments, the reaction temperature in step (c) is 300 °C.

[0063]

[0072] In some embodiments, the residence time during the reaction in step (c) is from 0.5 second to 30 seconds, for example, 30 seconds, 25 seconds, 20 seconds, 15 seconds, 10 seconds, 9 seconds, 8 seconds, 7 seconds, 6 seconds, 5 seconds, 4.5 seconds, 4 seconds, 3.5 seconds, 3 seconds, 2.5 seconds, 2 seconds, 1.5 seconds, 1 second, 0.5 second, or any value between any two of the above values. Preferably, the residence time during the reaction in step (c) is from 1.5 seconds to 20 seconds. More preferably, the residence time during the reaction in step (c) is from 2.5 seconds to 10 seconds. The residence time during the reaction in step (c) can be controlled by various methods, for example, by controlling the flow rate of the reaction product mixture in step (b) and / or the inner diameter of the tubular reactor.

[0064]

[0073] In some embodiments, in step (c), no organic solvent is used.

[0074] 4. Step (d)

[0075] In some embodiments, the preparation method of the present application further includes step (d): recovering the product.

[0065]

[0076] In some embodiments, step (d) of the present application sets a quench zone at the outlet of the vacuum reactor, and the reaction product mixture obtained in step (c) contacts the quench medium flow introduced in the quench zone, and includes the step of reducing the temperature of the reaction product mixture obtained in step (c) to 170°C or lower.

[0066]

[0077] In some embodiments, the product recovery temperature in step (d) is 170°C or lower, for example, 170°C, 165°C, 160°C, 155°C, 150°C, 145°C, 140°C, 135°C, 130°C, 125°C, 120°C, 115°C, 110°C, 105°C, 100°C, 95°C, 90°C, 85°C, 80°C, 75°C, 70°C, or any value between any two of the above values. In some embodiments, the product recovery temperature in step (d) is from 80°C to 150°C. In some embodiments, the product recovery temperature in step (d) is from 110°C to 140°C.

[0067]

[0078] In some embodiments, in step (d), the temperature of the reaction product mixture obtained in step (c) is rapidly decreased by utilizing the latent heat of vaporization of the quench medium. Organic solvents (e.g., toluene, chlorobenzene, chloronaphthalene), isocyanates, or mixtures of solvents and isocyanates are often used as quench media for reducing the temperature in a supercritical reactor in the prior art. In some embodiments, the quench medium in step (d) is selected from the group consisting of organic solvents, isocyanates, phosgene, hydrogen chloride, inert carrier gases, and any combination thereof. In some embodiments, the organic solvent is selected from the group consisting of dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof. In some embodiments, the quench medium is a liquid (e.g., liquid phosgene). In some embodiments, the temperature of the reaction product mixture obtained in step (c) is rapidly decreased by using phosgene or a mixture of phosgene and isocyanate as the quench medium. Without being limited by any theory, the effect of using phosgene or a mixture of phosgene and isocyanate as the quench medium is considered to be superior to the effect of using an organic solvent as the quench medium. For example, by using phosgene or a mixture of phosgene and isocyanate as the quench medium, the use of an organic solvent in the entire reaction system can be avoided, and the problem of blockage of the inlet caused by solid adhesion to the wall can also be avoided. Therefore, there are no steps of solvent recovery, rectification, and regeneration purification in the whole process, the preparation process is simpler, the energy consumption is less, and the cost is less. Furthermore, since the high-temperature purification process is shortened, the high-temperature residence time of the reaction product isocyanate is significantly shortened, the self-polymerization reaction is reduced, and the product yield is increased.

[0068]

[0079] 5. Step (e)

[0080] In some embodiments, the preparation method of the present application further includes step (e): purifying the product.

[0069]

[0081] In some embodiments, step (e) includes the following sub-steps:

[0082] 1) Introducing the reaction product mixture obtained in step (c) or step (d) into a degassing tower, where hydrogen chloride and phosgene in the reaction product mixture overflow from the upper part of the degassing tower and enter a hydrogen chloride / phosgene separation tower, and the hydrogen chloride overflowing from the upper part of the separation tower is purified by a tail gas treatment unit to produce by-product hydrochloric acid;

[0083] 2) Recovering phosgene from the bottom of the separation tower in sub-step 1) for reuse and forming a phosgene stream in step (a);

[0084] 3) Recovering isocyanate and by-products in the reaction product mixture from the bottom of the degassing tower in sub-step 1) and passing the isocyanate and by-products through a light component removal tower to remove light component by-products;

[0085] 4) Recovering isocyanate and heavy component by-products from the bottom of the light component removal tower in sub-step 3), passing the isocyanate and heavy component by-products through a purification tower, recovering isocyanate from the purification tower, and removing heavy component by-products.

[0070]

[0086] For example, as shown in FIG. 1, in sub-step 1), the reaction product mixture obtained in step (c) or step (d) is introduced into a degassing tower 04, where hydrogen chloride and phosgene in the reaction product mixture overflow from the upper part of the degassing tower 04 and enter a hydrogen chloride / phosgene separation tower 05, and the hydrogen chloride overflowing from the upper part of the separation tower 05 is purified in a tail gas treatment unit to produce by-product hydrochloric acid.

[0071]

[0087] For example, as shown in FIG. 1, in the lower step 2), phosgene is recovered from the bottom of the hydrogen chloride / phosgene separation column 05 to form a phosgene stream, which is supplied to the supercritical reactor 01 for reuse.

[0072]

[0088] For example, as shown in FIG. 1, in the lower step 3), the isocyanate and by-products in the reaction product mixture are recovered from the bottom of the degassing column 04 and passed through the light component removal column 06 to remove the light component by-products. The light component by-products are conventional in the art. In some embodiments, the light component by-products are selected from the group consisting of piperidine, multiple hydropyridines, and combinations thereof. For example, as shown in FIG. 1, in the lower step 4), the isocyanate and heavy component by-products are recovered from the bottom of the light component removal column 06 and passed through the purification column 07, the isocyanate is recovered from the purification column, and the heavy component by-products are removed. The heavy component by-products are conventional in the art. In some embodiments, the heavy component by-products are selected from the group consisting of tar, PDI self-polymer, by-product urea, and any combination thereof. When the reactant amine is an amine salt, compared with the conventional gas-phase or liquid-phase phosgenation process, the step of converting the amine salt to an amine is omitted in the method for preparing isocyanate of the present application; compared with the existing salt-forming phosgenation process, the phosgene in the supercritical state used in the present application is used not only as a solvent for the reactant amine but also as a starting material for the reaction, and the use of a large amount of solvent can be avoided. Furthermore, in the process for preparing isocyanate using the method provided in the present application, the supercritical phosgenation reaction is combined with the reaction under reduced pressure, and as a result, not only the problems of insufficient reaction rate and high pressure in a simple supercritical reaction are avoided, but also the synergistic effects such as the problems of high impurity content and insufficient reaction in a simple pipe reaction are produced. Further, when phosgene or a mixture of phosgene and isocyanate is used as a quenching medium in the reaction process, the use of an organic solvent can be avoided, and the problem of blockage of the inlet caused by solid adhesion to the wall can also be avoided. Therefore, there are no steps of solvent recovery, rectification, and regeneration purification in the whole process, the preparation process is simpler, the energy consumption is less, and the cost is less.

[0073]

[0089] The summary of this application has been described above, and details may be simplified, generalized, and omitted. Therefore, it should be understood by those skilled in the art that this section is merely illustrative and is not intended to limit the scope of this application in any way. This summary is not intended to define the important features or essential features of the claimed subject matter, nor is it intended to be used as an aid in defining the scope of the claimed subject matter.

[0074]

[0090]

Examples

[0075]

[0091] To fully understand the present invention, the following examples are provided. It should be understood that these examples are provided for illustrative purposes only and should not be construed as limiting in any way.

[0076]

[0092] Abbreviations of some nouns mentioned in the examples are shown in Table 1.

[0077]

Table 1

[0093] The substance ratios, reaction conditions, and final yields used in the following examples are summarized in Table 2.

[0078]

Table 2-1

[0079]

Table 2-2

[0080]

Table 2-3

[0081]

Table 2-4

[0094] Example 1A: Preparation of PDI using PDA hydrochloride

[0095] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and fed into a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0082]

[0096] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa and the temperature was maintained in this state for 20 minutes.

[0083]

[0097] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0084]

[0098] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 159.4 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content was 88.6% and the yield was 92.3%.

[0085]

[0099] Example 1B: Preparation of PDI using PDA hydrochloride (PDA hydrochloride and phosgene were preheated separately without mixing)

[0100] PDA hydrochloride and liquid phosgene were separately heated to 182 °C in two high-pressure pipes.

[0086]

[0101] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Phosgene and PDA hydrochloride preheated to 182 °C were introduced into the tubular reactor at a molar ratio of 12:1. The residence time was controlled to 5 seconds, while the pressure inside the pipe was controlled to 80 KPa. The effluent gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0087]

[0102] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered. Then, when the residue was subjected to gas phase analysis, a number of impurities were found. The impurities were separated, analyzed, and identified as multiple hydropyridine impurities.

[0088]

[0103] Example 1C: Preparation of PDI using PDA hydrochloride (without homogenization shear)

[0104] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) without an internal homogenization device.

[0089]

[0105] Stirring was started. The reaction liquid was not homogenized by shear. Then, the 10 L autoclave was heated and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.9 MPa and the temperature was maintained in this state for 20 minutes.

[0090]

[0106] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped with extremely low-temperature phosgene at -20 °C to obtain the product liquid that was recovered. When about half of the reaction liquid had passed through, it was found that the pipe was blocked and the reaction could not be continued.

[0091]

[0107] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 76.1 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 87.9% and the yield was 43.7%.

[0092]

[0108] Example 1D: Preparation of PDI using PDA hydrochloride (the inner diameter of the reaction pipe was 3 mm)

[0109] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) without an internal homogenization device.

[0093]

[0110] Stirring was started. The reaction liquid was not homogenized by shear. Then, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 7.0 MPa, and the temperature was maintained in this state for 20 minutes.

[0094]

[0111] A tubular reactor (vacuum reactor) with an inner diameter of 3 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. When about half of the reaction liquid had passed through, it was found that the pipe was blocked and the reaction could not be continued.

[0095]

[0112] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 44.6 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content was 88.2% and the yield was 25.7%.

[0096]

[0113] Example 1E: Preparation of PDI using PDA hydrochloride (the inner diameter of the reaction pipe was 5 mm)

[0114] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) without an internal homogenization device.

[0097]

[0115] Stirring was started. The reaction liquid was not homogenized by shear. Then, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.5 MPa, and the temperature was maintained in this state for 20 minutes.

[0098]

[0116] A tubular reactor (vacuum reactor) with an inner diameter of 5 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid which was recovered.

[0099]

[0117] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 165.0 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 82.9% and the yield was 89.4%.

[0100]

[0118] Example 1F: Preparation of PDI using PDA hydrochloride (the inner diameter of the reaction pipe was 8 mm)

[0119] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) without an internal homogenization device.

[0101]

[0120] Stirring was started. The reaction liquid was not homogenized by shear. Then, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0102]

[0121] A tubular reactor (vacuum reactor) with an inner diameter of 8 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0103]

[0122] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 157.1 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 79.3% and the yield was 81.4%.

[0104]

[0123] Example 1G: Preparation of PDI using PDA hydrochloride (the inner diameter of the reaction pipe was 10 mm)

[0124] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) without an internal homogenization device.

[0105]

[0125] Stirring was started. The reaction liquid was not homogenized by shear. Then, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0106]

[0126] A tubular reactor (vacuum reactor) with an inner diameter of 10 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. Many yellowish-white solids were present in the recovered liquid, which was found to be the raw material.

[0107]

[0127] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 142.4 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 43.4% and the yield was 40.4%.

[0108]

[0128] Preparation of PDI using H:PDA hydrochloride (reaction at 350 °C) in Example 1

[0129] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0109]

[0130] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 7.0 MPa, and the temperature was maintained in this state for 20 minutes.

[0110]

[0131] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 350 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0111]

[0132] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 151.3 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 82.2% and the yield was 81.3%.

[0112]

[0133] Example 1I: Preparation of PDI using PDA hydrochloride (reaction at 400 °C)

[0134] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0113]

[0135] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.7 MPa, and the temperature was maintained in this state for 20 minutes.

[0114]

[0136] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 400 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 Kpa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. The recovered liquid contained a lot of tar and carbon residues.

[0115]

[0137] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 129.2 g of the residue. Gas phase quantitative analysis was performed, and the results showed that the content rate was 63.0% and the yield was 53.2%.

[0116]

[0138] Example 1J: Preparation of PDI using PDA hydrochloride (reaction at 250 °C)

[0139] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0117]

[0140] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.4 MPa, and the temperature was maintained in this state for 20 minutes.

[0118]

[0141] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 250 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid. The recovered liquid was found to contain a white solid, which was analyzed and identified as the starting material PDA hydrochloride.

[0119]

[0142] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 173.3 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content was 70.0% and the yield was 79.3%.

[0120]

[0143] Example 1K: Preparation of PDI using PDA hydrochloride (molar ratio of PDA hydrochloride: phosgene = 1:10)

[0144] 175 g (1 mol) of PDA hydrochloride and 990 g (10 mol) of phosgene were uniformly stirred and mixed at 0 °C and fed into a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0121]

[0145] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 5.7 MPa, and the temperature was maintained at this state for 20 minutes.

[0122]

[0146] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0123]

[0147] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 153.8 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 87.7% and the yield was 88.2%.

[0124]

[0148] Example 1L: Preparation of PDI using PDA hydrochloride (molar ratio of PDA hydrochloride: phosgene = 1:16)

[0149] 175 g (1 mol) of PDA hydrochloride and 1584 g (16 mol) of phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0125]

[0150] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 7.8 MPa, and the temperature was maintained in this state for 20 minutes.

[0126]

[0151] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0127]

[0152] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 156.9 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 88.9% and the yield was 91.2%.

[0128]

[0153] Example 1 Preparation of PDI using PDA hydrochloride (molar ratio of PDA hydrochloride: phosgene = 1:20)

[0154] 175 g (1 mol) of PDA hydrochloride and 1977.5 g (20 mol) of phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0129]

[0155] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 8.4 MPa, and the temperature was maintained in this state for 20 minutes.

[0130]

[0156] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0131]

[0157] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 158.7 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 89.2% and the yield was 92.5%.

[0132]

[0158] Example 1 Preparation of PDI using PDA hydrochloride (residence time was 1 second)

[0159] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0133]

[0160] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was 6.3 MPa, and the temperature was maintained in this state for 20 minutes.

[0134]

[0161] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 1 second (i.e., the residence time was 1 second). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. The recovered liquid was found to contain a white solid, which was analyzed and identified as the starting material PDA hydrochloride.

[0135]

[0162] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 167.5 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content was 55.0% and the yield was 60.2%.

[0136]

[0163] Example 1O: Preparation of PDI using PDA hydrochloride (residence time was 2.5 seconds)

[0164] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0137]

[0165] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene), and the pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.2 MPa, and the temperature was maintained in this state for 20 minutes.

[0138]

[0166] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 2.5 seconds (i.e., the residence time was 2.5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. The recovered liquid was found to contain white solids, which were analyzed and identified as the raw material PDA hydrochloride.

[0139]

[0167] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 156.1 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 69.8% and the yield was 71.2%.

[0140]

[0168] Example 1P: Preparation of PDI using PDA hydrochloride (the residence time was 10 seconds)

[0169] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and fed into a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0141]

[0170] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.5 MPa, and the temperature was maintained in this state for 20 minutes.

[0142]

[0171] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 10 seconds (i.e., the residence time was 10 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0143]

[0172] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 155.3 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 88.0% and the yield was 89.3%.

[0144]

[0173] Example 1 Q: Preparation of PDI using PDA hydrochloride (the residence time was 20 seconds)

[0174] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0145]

[0175] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.4 MPa, and the temperature was maintained at this state for 20 minutes.

[0146]

[0176] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 20 seconds (i.e., the residence time was 20 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered. The recovered liquid contained a lot of tar and carbon residues.

[0147]

[0177] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 176.7 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 54.2% and the yield was 62.6%.

[0148]

[0178] Preparation of PDI using R:PDA hydrochloride (the pressure in the hyper was 50 KPa)

[0179] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0149]

[0180] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0150]

[0181] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 50 KPa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0151]

[0182] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 160.9 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 81.9% and the yield was 85.6%.

[0152]

[0183] Example 1S: Preparation of PDI using PDA hydrochloride (the pressure in the hype was 110 KPa)

[0184] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0153]

[0185] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued; when the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0154]

[0186] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 110 KPa, and the outflow gas (liquid) was trapped with phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0155]

[0187] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 152.3 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 74.3% and the yield was 73.5%.

[0156]

[0188] Example 1 Preparation of PDI using PDA hydrochloride (the pressure in the hype was 140 KPa)

[0189] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0157]

[0190] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0158]

[0191] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated to raise its temperature to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 140 KPa, and the outflow gas (liquid) was trapped by phosgene at an extremely low temperature of -20 °C to obtain the product liquid that was recovered.

[0159]

[0192] After separating hydrogen chloride gas from the recovered liquid, phosgene was recovered, and then the residue was weighed to obtain 162.3 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content rate was 68.6% and the yield was 72.3%.

[0160]

[0193] Example 1 Preparation of PDI using U:PDA hydrochloride (using cryotrap of phosgene + PDI)

[0194] 175 g (1 mol) of PDA hydrochloride and 1188 g (12 mol) of liquid phosgene were uniformly stirred and mixed at 0 °C and supplied to a 10 L autoclave (supercritical reactor) equipped with an internal homogenization device.

[0161]

[0195] The internal homogenization pump and stirring were started simultaneously. After mixing by uniform shear, the 10 L autoclave was heated, and the temperature inside the autoclave was slowly raised to 182 °C (the supercritical temperature of phosgene). The pressure was observed. When the pressure was less than 10 MPa, the operation was continued again. When the pressure exceeded 10 MPa, the heating was stopped. When the temperature reached 182 °C, the pressure was recorded as 6.6 MPa, and the temperature was maintained in this state for 20 minutes.

[0162]

[0196] A tubular reactor (vacuum reactor) with an inner diameter of 4 mm was preheated and its temperature was raised to 300 °C. Then, the valve of the autoclave was slowly opened, and the outflow rate of the reaction liquid was controlled by adjusting the valve so that the time for the reaction liquid to pass through the tubular reactor was 5 seconds (i.e., the residence time was 5 seconds). During the process, the pressure in the pipe was controlled to be 80 KPa, and the outflow gas (liquid) was trapped by phosgene + PDI at an extremely low temperature of -20 °C (a total of 6000 g of phosgene + 220 g of PDI), and the product liquid was recovered.

[0163]

[0197] After separating gaseous hydrogen chloride from the recovered liquid, phosgene was recovered, and then the residue was weighed, obtaining 380.6 g of the residue. Gas-phase quantitative analysis was performed, and the results showed that the content was 88.4% and the yield was 92.1% by subtracting the 220 g of PDI used to trap by quenching.

Claims

Claim 1 A method for preparing isocyanate, comprising the following steps: (a) mixing a reactant amine stream and a phosgene stream at a temperature of -5 to 5 °C to obtain a mixture of the reactant amine and phosgene; (b) adjusting the temperature of the mixture obtained in step (a) to 182 °C to 205 °C so that phosgene is in a supercritical state, and reacting in a supercritical reactor for at least 15 minutes; (c) reacting the reaction product mixture obtained in step (b) under reduced pressure conditions for a reaction time of 30 seconds or less, optionally, the reduced pressure is carried out in a reduced pressure reactor, optionally, the reduced pressure reactor is a tubular reactor, and / or the inner diameter of the pipe in the reduced pressure reactor is 4 to 9 mm; The above method comprising the steps. Claim 2 Step (d): recovering the product, optionally, setting a quench zone at the outlet of the reduced pressure reactor, contacting the reaction product mixture obtained in step (c) with a quench medium stream introduced in the quench zone, and lowering the temperature of the reaction product mixture obtained in step (c) to 170 °C or less. The method according to claim 1, further comprising the step. Claim 3 Step (e): purifying the product, optionally, 1) introducing the reaction product mixture obtained in step (c) or step (d) into a degassing tower, where hydrogen chloride and phosgene in the reaction product mixture overflow from the upper part of the degassing tower and enter a hydrogen chloride / phosgene separation tower, and the hydrogen chloride overflowing from the upper part of the separation tower is purified by a tail gas removal treatment unit to produce by-product hydrochloric acid; 2) recovering phosgene from the bottom of the separation tower in the lower step 1) for reuse, and forming a phosgene stream in step (a); 3) recovering the isocyanate and by-products in the reaction product mixture from the bottom of the degassing tower in the lower step 1), and passing the isocyanate and by-products through a light component removal tower to remove light component by-products; 4) recovering the isocyanate and heavy component by-products from the bottom of the light component removal tower in the lower step 3), passing the isocyanate and heavy component by-products through a purification tower, recovering the isocyanate from the purification tower, and removing the heavy component by-products; The method according to claim 1 or 2, further comprising the step. Claim 4 Step (a) is carried out before step (b) and step (c); and / or no organic solvent is used in each of step (a), step (b), and step (c), the method according to any one of claims 1 to 3.

5. In step (a), (i) the reactant amine stream and the phosgene stream are introduced into a supercritical fluid reactor and mixed; (ii) the mixed reactant amine stream and phosgene stream form suspended particles by shear emulsification, optionally, the shear emulsification is carried out in the supercritical fluid reactor, and optionally, the suspended particles have a diameter of 100 μm or less, preferably 50 μm or less, more preferably 20 μm or less; and / or (iii) the reactant amine stream and the phosgene stream pass through a homogenization pump for uniform shear emulsification, optionally, the shear emulsification is achieved by controlling the lift, rotational speed, torque, suction, and / or shear homogenization time of the homogenization pump, and optionally, the circulating output volume of the homogenization pump is controlled to be 10 times or more the volume of the liquid hold-up in the supercritical reactor; The method according to any one of claims 1 to 4.

6. The phosgene stream in step (a) is stoichiometrically in excess compared to the amino groups of the reactant amine stream; The supply ratio (molar ratio) of the phosgene stream to the reactant amine stream in step (a) is 7:1 to 25:1 (preferably 12:1); The phosgene stream in step (a) exists in liquid form; The reaction temperature in step (c) is 150°C to 450°C, preferably 200°C to 400°C, more preferably 250°C to 350°C; The reaction pressure in step (c) is 15 kPa to 500 kPa, preferably 50 kPa to 300 kPa, more preferably 50 kPa to 110 kPa; The residence time during the reaction in step (c) is 0.5 seconds to 30 seconds, preferably 1.5 seconds to 20 seconds, more preferably 2.5 seconds to 10 seconds; The product recovery temperature in step (d) is 170°C or less, preferably 80°C to 150°C, more preferably 110°C to 140°C; In step (d), the temperature of the reaction product mixture obtained in step (c) is rapidly lowered by utilizing the latent heat of vaporization of the quench medium; and / or The quenching medium in step (d) is selected from the group consisting of an organic solvent, isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof, optionally the quenching medium in step (d) is liquid, and optionally liquid phosgene; The method according to any one of claims 1 to 5. Claim 7 The method according to claim 6, wherein the organic solvent is selected from the group consisting of dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof. Claim 8 The isocyanate is a diisocyanate, optionally an aliphatic diisocyanate or an aromatic diisocyanate, optionally methylene diphenyl diisocyanate as a pure isomer or a mixture of isomers, toluene diisocyanate as a pure isomer or a mixture of isomers, 2,6-xylyl isocyanate, 1,5-naphthalene diisocyanate, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, t-butyl isocyanate, pentyl isocyanate (e.g., pentamethylene diisocyanate), t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexamethylene diisocyanate), cyclopentyl isocyanate, cyclohexyl isocyanate, and phenyl isocyanate (e.g., p-phenylene diisocyanate), and is optionally PDI, HDI, IPDI, or HTDI, and the method according to any one of claims 1 to 7. Claim 9 The reactant amine has the structural formula R(NH ２ ) ｎ where n is 1, 2, or 3 and R is an aliphatic or aromatic hydrocarbyl group, optionally where n is 2 and R is an aliphatic hydrocarbyl group, optionally where n is 2 and R is an aliphatic hydrocarbyl group having 2 to 10 carbon atoms, optionally where n is 2 and R is a linear or cyclic aliphatic hydrocarbyl group having 3 to 10 carbon atoms; The reactant amine is present in free form or as an amine salt, optionally the amine salt is selected from the group consisting of hydrochloride, sulfate, bisulfate, nitrate, and carbonate; and / or The reactant amine is one or more selected from the group consisting of ethylamine, butylamine, pentamethylenediamine, hexamethylenediamine, 1,4-diaminobutane, 1,8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 1,5-naphthalenediamine, diphenylmethanediamine, dicyclohexylmethanediamine, m-cyclohexyldimethylenediamine, isophoronediamine, methylcyclohexanediamine, and trans-1,4-cyclohexanediamine, and optionally is selected from the group consisting of PDA, PDA hydrochloride, HDA, HDA hydrochloride, IPDA, IPDA hydrochloride, HTDA, and HTDA hydrochloride; The method according to any one of claims 1 to 8.

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