Method for preparing isocyanates by a gas phase solventless process

Abstract

The present application relates to a process for preparing isocyanates. In particular, in the process of the present application, phosgene, especially liquid phosgene, is used as a quenching medium for preparing isocyanates.

Description

[Technical field]

[0001] The present invention relates to a method for preparing isocyanates, and more particularly to a method for preparing isocyanates by using phosgene, especially liquid phosgene, as a quenching medium. [Background technology]

[0002]

[0002] Isocyanates are a class of compounds that contain one or more isocyanate groups, such as aliphatic isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorus-containing isocyanates, inorganic isocyanates, and blocked isocyanates. Due to the high degree of unsaturation of the isocyanate groups they contain, they are highly chemically active and can undergo important chemical reactions with many substances. Therefore, isocyanates are widely used in reagents for polyurethane, polyurethane-urea, polyurea, polymer modification, organic synthesis, agriculture, medicine, and other fields.

[0003] In the prior art, the principles underlying the preparation of isocyanates using phosgene and amines are well known, and the methods mainly include liquid-phase and gas-phase methods. In the method of preparing isocyanates by gas-phase method, the isocyanates formed in the reactor are thermally unstable at high reaction temperatures (e.g., 300-400°C). Therefore, in order to avoid the formation of undesirable by-products due to thermal decomposition or further reaction of the isocyanates, the resulting reaction product mixture needs to be rapidly cooled to a temperature below 200°C after the phosgenation reaction. For this purpose, in the prior art, organic solvents (e.g., toluene, chlorobenzene, and chloronaphthalene) (see Chinese Patent No. 102245565B), isocyanates (see Chinese Patent No. 110914236A), or mixtures of solvents and isocyanates (see Chinese Patent No. 110072845A) are often used as quenching media to condense the reaction product mixture. One of the disadvantages of using these quenching media is that solid precipitates may form in the reactor, which will eventually block the passage of the gaseous reaction product mixture. Therefore, the reactor is required to be closed to clean the reaction passage. In addition, the recovery of the organic solvent also increases the production cost. In the prior art, in order to minimize the formation of solid precipitates, the quenching liquid is injected into the quenching zone by passing the quenching liquid through a quenching liquid nozzle arranged at the inlet of the quenching zone (see China Patent No. 111094240A). This raises the higher equipment requirements of the reactor and increases the production cost.

[0004] Therefore, there remains a need for optimized processes for preparing isocyanates. Summary of the Invention [Problem to be solved by the invention]

[0005]

[0005] The object of the present application is to provide a method for preparing isocyanates, more particularly, a method for preparing isocyanates by using phosgene (in particular liquid phosgene) as a quenching medium or by adjusting the flow rate ratio of the quenching medium to the phosgene stream prior to the phosgenation reaction. [Means for solving the problem]

[0006] In one aspect, the present application provides a method for preparing an isocyanate, comprising the steps of:

[0007] (a) providing a reactant amine stream and a phosgene stream, passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. and reacting therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene;

[0008] (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel;

[0009] (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing the hydrogen chloride, unreacted phosgene, and uncollected isocyanate through the washing zone;

[0010] (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone. The present invention provides a method comprising:

[0007]

[0011] The first quench medium and the second quench medium are independently selected from the group consisting of isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof, and the flow ratio of the first quench medium to the phosgene stream of step (a) is from 0.4:1 to 2:1.

[0008]

[0012] In another aspect, the present application provides a method for preparing an isocyanate, comprising the steps of:

[0013] (a) providing a reactant amine stream and a phosgene stream, passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. and reacting therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene;

[0014] (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel;

[0015] (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing the hydrogen chloride, unreacted phosgene, and uncollected isocyanate through the washing zone;

[0016] (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone. The present invention provides a method comprising:

[0009]

[0017] The first quench medium is phosgene and the second quench medium is selected from the group consisting of an isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof.

[0010]

[0018] In some embodiments, the reactant amine stream of step (a) is preheated to 200° C. to 600° C. by a first preheater before being passed into the first vessel; and / or the phosgene stream of step (a) is preheated to 200° C. to 600° C. by a second preheater before being passed into the first vessel.

[0011]

[0019] In some embodiments, the reactant amine stream and / or phosgene stream of step (a) are in gaseous or atomized form before, during, or after being passed into the first vessel.

[0012]

[0020] In some embodiments, the reactant amine stream and the phosgene stream of step (a) are mixed in the headspace of the first vessel.

[0013]

[0021] In some embodiments, the reactant amine stream and phosgene stream of step (a) flow from top to bottom in the reaction zone of the first vessel and react during this process to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene.

[0014]

[0022] In some embodiments, the reactant amine stream and the phosgene stream of step (a) have a retention time in the reaction zone of the first vessel of 260 seconds or less.

[0015]

[0023] In some embodiments, the phosgene stream in step (a) is in stoichiometric excess based on the amino groups of the reactant amine stream.

[0016]

[0024] In some embodiments, the feed ratio (in molar terms) of the phosgene stream to the reactant amine stream in step (a) is from 7:1 to 15:1.

[0017]

[0025] In some embodiments, the phosgene stream and / or the reactant amine stream of step (a) are passed into the first vessel simultaneously with or following the inert carrier gas.

[0018]

[0026] In some embodiments, the inert carrier gas is preheated to between 200° C. and 600° C. before being passed into the first vessel. In some embodiments, the molar flow rate of the inert carrier gas is between 10 and 100% of the molar flow rate of the reactant amine or phosgene stream.

[0019]

[0027] In some embodiments, the first quench medium in step (b) and the second quench medium in step (d) are the same. In some embodiments, the first quench medium in step (b) and the second quench medium in step (d) are different. In some embodiments, the first quench medium in step (b) and / or the second quench medium in step (d) do not comprise an organic solvent. In some embodiments, the first quench medium in step (b) is liquid phosgene. In some embodiments, the second quench medium is a liquid. In some embodiments, both the first quench medium and the second quench medium are liquid phosgene.

[0020]

[0028] In some embodiments, in step (b), the temperature of the reaction product mixture obtained in step (a) is rapidly reduced by utilizing the latent heat of vaporization of the first quench medium.

[0021]

[0029] In some embodiments, in step (d), the flow directions of the hydrogen chloride, unreacted phosgene, and uncollected isocyanate and the second quench medium stream of step (c) are reversed in the wash zone.

[0022]

[0030] In some embodiments, the washing conditions are configured to allow hydrogen chloride and unreacted phosgene (and optionally, inert carrier gas) to overflow from the top of the second vessel, and allow uncollected isocyanate to be refluxed to a collection zone of the second vessel. In some embodiments, the hydrogen chloride and unreacted phosgene (and optionally, inert carrier gas) overflowing from the top of the second vessel are cooled to −5 to 20° C. by a condenser and passed through a pressure control system. In some embodiments, the washing conditions are to control the temperature of the second quench medium and / or the condenser to a range of 0 to 15° C. In some embodiments, the hydrogen chloride overflowing from the top of the second vessel is passed through a pressure control system and then subjected to hydrogen chloride purification to form by-product hydrochloric acid.

[0023]

[0031] In some embodiments, the phosgene overflowing from the top of the second vessel is recycled to form the phosgene stream of step (a) or the first quench medium stream of step (b).

[0024]

[0032] In some embodiments, the isocyanate is a diisocyanate. In some embodiments, the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate. The isocyanate is selected from the group consisting of methylene diphenyl diisocyanate, pure isomer or mixture of isomers, toluene diisocyanate, pure isomer or 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). In some embodiments, the isocyanate is PDI, HDI, IPDI, or HTDI.

[0025]

[0033] In some embodiments, the reactant amine has the structural formula R(NH 2 ) nwhere n is 1, 2, or 3, and R is an aliphatic hydrocarbyl group or an 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. In some embodiments, the reactant amine is present in free form. 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, hydrogen sulfate, nitrate, and carbonate.

[0026]

[0034] 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, and trans-1,4-cyclohexanediamine. 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, the first quench medium is liquid phosgene, and the second quench medium is selected from the group consisting of liquid PDI, liquid HDI, liquid phosgene, liquid nitrogen, liquid carbon dioxide, or liquid hydrogen chloride. In some embodiments, both the first quench medium and the second quench medium are liquid phosgene. In some embodiments, when the first quench medium is phosgene, the flow ratio of the first quench medium phosgene to the phosgene stream in step (a) is 0.7:1 to 1.2:1.

[0027]

[0035] According to the method for preparing isocyanates provided in the present application, the use of solvents (especially organic solvents) during the preparation method can be avoided, the energy consumption is significantly reduced, the preparation method of isocyanates is simplified, and the equipment investment is lowered, thereby reducing the cost of large-scale production of isocyanates and reducing environmental pollution.

[0028]

[0036] The summary of the present application has been described above, and details may be simplified, generalized, or omitted. Therefore, it should be recognized by those skilled in the art that this section is merely explanatory and does not limit the scope of the present application in any manner. This summary is not intended to define key features or essential features of the claimed subject matter, nor is it to be used as an aid in determining the scope of the claimed subject matter.

[0029]

[0037] The foregoing and other features of the present application will become more fully and clearly understood from the following description and the appended claims, taken in conjunction with the accompanying drawings. It can be understood that these drawings only depict some embodiments of the present application disclosure, and therefore should not be considered as limiting the scope of the present application disclosure. The present application disclosure will be more clearly and in more detail described with reference to the accompanying drawings. [Brief description of the drawings]

[0030] [Figure 1]

[0038] FIG. 1 is a schematic diagram showing a flow chart of a method for preparing an isocyanate according to an embodiment of the present application. In the figure, E01 is a first preheater; E02 is a second preheater; E03 is a cooler; 101 is a reaction zone of the first vessel; 102 is a quench zone of the first vessel; 201 is a collection zone of the second vessel; 202 is a washing zone of the second vessel; and P01 is a pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031]

[0039] The illustrative embodiments described in the detailed description, drawings, and claims are not limiting. Other embodiments may be incorporated and other changes may be made without departing from the spirit or scope of the subject matter of this application. The various aspects of the disclosure of this application, as generally described herein and illustrated in the accompanying drawings, can be arranged, substituted, combined and designed in many different forms, all of which are expressly understood to constitute a part of this application.

[0032]

[0040] In one aspect, the present application provides a method for preparing an isocyanate, comprising the steps of:

[0041] (a) providing a reactant amine stream and a phosgene stream and passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. to react therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene;

[0042] (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel;

[0043] (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing the hydrogen chloride, unreacted phosgene, and uncollected isocyanate through the washing zone;

[0044] (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone. The present invention provides a method comprising:

[0033]

[0045] The first quench medium and the second quench medium are independently selected from the group consisting of isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof, and the flow ratio of the first quench medium to the phosgene stream of step (a) is from 0.4:1 to 2:1.

[0034]

[0046] In another aspect, the present application provides a method for preparing an isocyanate, comprising the steps of:

[0047] (a) providing a reactant amine stream and a phosgene stream, passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. and reacting therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene;

[0048] (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel;

[0049] (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing the hydrogen chloride, unreacted phosgene, and uncollected isocyanate through the washing zone;

[0050] (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone. The present invention provides a method comprising:

[0035]

[0051] The first quench medium is phosgene and the second quench medium is selected from the group consisting of an isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof.

[0036]

[0052] In this application, "isocyanate" refers to compounds containing one or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) isocyanate groups (RN=C=O), such as aliphatic isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorus-containing isocyanates, inorganic isocyanates, and blocked isocyanates. In some embodiments, the isocyanates in this application are diisocyanates. In some embodiments, the isocyanates in this application are aliphatic diisocyanates or aromatic diisocyanates. In some embodiments, the isocyanates in this application include aromatic and aliphatic isocyanates. For example, aromatic isocyanates include methylene diphenyl diisocyanate, pure isomer or mixture of isomers, toluene diisocyanate, pure isomer or 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 pentamethylene diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, and toluene diisocyanate. In some embodiments, the isocyanate in this application is pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), or methylcyclohexane diisocyanate (HTDI).

[0037]

[0053] Steps (a), (b), (c) and (d) of the method for preparing an isocyanate according to the present application are described in detail below.

[0038]

[0054] 1. Step (a)

[0055] In step (a) of the present application, a reactant amine stream and a phosgene stream are provided and then passed to a reaction zone of a first vessel at a temperature between 200° C. and 600° C. and reacted in the reaction zone of the first vessel at a temperature between 200° C. and 600° C. to obtain a reaction product mixture containing isocyanate, hydrogen chloride, and unreacted phosgene.

[0039]

[0056] In this application, a "reactant amine" refers to an amino (-NH) amine, which is a starting material for preparing an isocyanate. 2 For example, in some embodiments, the reactant amine has the structural formula R(NH 2 ) n where n is 1, 2, or 3, and R is an aliphatic hydrocarbyl group or an 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).

[0040]

[0057] In some embodiments, the reactant amine is, i.e., one NH 2 In some embodiments, the reactant amine is a primary amine having two NH groups. 2The diamine has a group. 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.

[0041]

[0058] In some embodiments, the reactant amine is present in free form. The term "free form" refers to the amine compound in non-salt form. The free amine compound may differ from the various salt forms in some physical and / or chemical properties, for example, in its solubility in polar solvents. The free amine compound may also be the same or similar to its various salt forms in some physical and / or chemical properties.

[0042]

[0059] In some embodiments, the reactant amine is present as an amine salt, hi some embodiments, the amine salt is selected from the group consisting of hydrochloride, sulfate, hydrogen sulfate, nitrate, and carbonate.

[0043]

[0060] 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.

[0044]

[0061] Isocyanates are typically prepared by the reaction of amines with phosgene. In preparing isocyanates, the temperature of the reaction with phosgene varies depending on the type of reactant amine used. In general, the reactant amine is reacted with phosgene at a temperature between 200°C and 600°C (e.g., 250°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 450°C, 500°C, 550°C, or any temperature within the range between any two of the above values) to produce an isocyanate.

[0045]

[0062] The reaction of amines with phosgene often occurs in steps: first, a carbamoyl chloride (RNHCOCl) is formed with the amine and phosgene at low temperature, which is then converted to the corresponding isocyanate (RN=C=O) at elevated temperature; hydrogen chloride is removed in both steps.

[0046]

[0063] For example, pentamethylenediamine and phosgene are used as starting materials and the main reactions in the reaction zone of the first vessel are as follows:

[0047] [ka]

[0048]

[0064] In some embodiments, the reactant amine stream of step (a) is in gaseous or misty form before, during, or after being passed into the first vessel. The vaporization of the reactant amine can be carried out in known vaporization equipment. In general, the vaporization can result in the decomposition of the reactant amine. To reduce the decomposition of the reactant amine, it should usually be advantageously vaporized, for example, at lower temperatures and lower pressures (e.g., below 75-85 kPa absolute pressure). In some embodiments, the phosgene stream of step (a) is in gaseous or misty form before, during, or after being passed into the first vessel. In step (a), the reactant amine stream can be passed into the first vessel with one side stream containing the reactant amine, or with multiple side streams (e.g., 2, 3, 4, 5 or more) containing the reactant amine. Similarly, in step (a), the phosgene stream may be passed into the first vessel with one sidestream containing phosgene, or with multiple sidestreams containing phosgene (e.g., 2, 3, 4, 5 or more). When the reactant amine stream (or phosgene stream) of step (a) is passed into the first vessel with multiple sidestreams containing the reactant amine (or phosgene), the multiple sidestreams may be passed into the first vessel at the same location or at different locations.

[0049]

[0065] In the process of preparing isocyanates, it is generally required to add a large amount of excess phosgene because when the phosgene concentration is insufficient, the formed isocyanate reacts with the excess amine to form urea or a high viscosity solid by-product. Therefore, it is preferable to provide an excess of phosgene to prevent the formation of by-products. For example, in some embodiments, the phosgene stream in step (a) is a stoichiometric excess based on the amino groups of the reactant amine stream. For example, the molar ratio of phosgene to amino groups of the reactant amine is typically from 1.1:1 to 30:1 (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, and ranges between any two of the above values). In some embodiments, in the first vessel, phosgene is used in a stoichiometric excess based on 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%) greater than theoretical. When the reactant amine stream (and / or phosgene stream) of step (a) is passed into the first vessel with multiple side streams containing the reactant amine (and / or phosgene), the total phosgene stream resulting from the sum of the multiple side streams containing phosgene is in stoichiometric excess based on the amino groups of the total reactant amine stream resulting from the sum of the multiple streams containing the reactant amine.

[0050]

[0066] In some embodiments, the feed ratio (in molar terms) of the phosgene stream to the reactant amine stream in step (a) is from 7:1 to 15:1 (e.g., 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or any value between any two of the above ratios). Further, the feed ratio (in molar terms) of the phosgene stream to the reactant amine stream in step (a) is from 10:1 to 14:1.

[0051]

[0067] In step (a), the phosgene contained in the phosgene stream may be unused phosgene or recycled phosgene. The term "unused phosgene" refers to a stream containing phosgene that is not recycled from the phosgenation process and that has not been subjected to any reaction step involving the phosgenation reaction after phosgene is usually synthesized with chlorine and carbon monoxide. The term "recycled phosgene" refers to a stream containing phosgene that is generated by collecting the exhaust gas of a reaction process for preparing isocyanates by phosgenation. As mentioned above, in the process for preparing isocyanates by a gas phase process, the use of excess phosgene is generally required, resulting in the presence of a large amount of phosgene in the reaction exhaust gas. Recycling of phosgene in the exhaust gas can reduce production costs.

[0052]

[0068] In some embodiments, the reactant amine stream of step (a) is preheated by a first preheater to a temperature required for the reaction of the reactant amine and phosgene to produce isocyanate, e.g., 200°C to 600°C (e.g., 250°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 450°C, 500°C, 550°C, or a range between any two of the foregoing values) prior to being passed into the first vessel. In some embodiments, the phosgene stream of step (a) is preheated by a second preheater to a temperature required for the reaction of the reactant amine and phosgene to produce isocyanates, e.g., 200°C to 600°C (e.g., 250°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 450°C, 500°C, 550°C, or a range between any two of the above values), before being passed into the first vessel. In some embodiments, the reactant amine and phosgene streams of step (a) are mixed in a mixing device and then preheated by a preheater to a temperature required for the reaction of the reactant amine and phosgene to produce isocyanates, for example, from 200° C. to 600° C. (e.g., 250° C., 300° C., 310° C., 320° C., 330° C., 340° C., 350° C., 360° C., 370° C., 380° C., 390° C., 400° C., 450° C., 500° C., 550° C., or a range between any two of the above values), prior to being passed into the first vessel. The reactant amine and / or phosgene may be preheated by direct or indirect heating, by steam heating, by electrical heaters, or by fuel combustion.

[0053]

[0069] In some embodiments, the reactant amine stream and the phosgene stream of step (a) are mixed in the headspace of the first vessel.

[0054]

[0070] In some embodiments, the reactant amine stream and the phosgene stream of step (a) are reacted in the reaction zone of the first vessel under an absolute pressure of 0.05 to 0.2 MPa (e.g., 0.06 Mpa, 0.07 Mpa, 0.08 Mpa, 0.09 Mpa, 0.1 Mpa, 0.11 Mpa, 0.12 Mpa, 0.13 Mpa, 0.14 Mpa, 0.15 Mpa, 0.16 Mpa, 0.17 Mpa, 0.18 Mpa, 0.19 Mpa, or a range between any two of the above values). The reaction is preferably carried out under an absolute pressure of 0.05 to 0.12 Mpa, more preferably 0.08 to 0.1 Mpa.

[0055]

[0071] In some embodiments, the reactant amine and phosgene streams of step (a) have a retention time in the reaction zone of the first vessel of 260 seconds or less, e.g., 250 seconds or less, 240 seconds or less, 230 seconds or less, 220 seconds or less, 210 seconds or less, 200 seconds or less, 190 seconds or less, 180 seconds or less, 170 seconds or less, 160 seconds or less, 150 seconds or less, 140 seconds or less, 130 seconds or less, 120 seconds or less, 110 seconds or less, 100 seconds or less, etc. Preferably, the reactant amine and phosgene streams of step (a) have a retention time in the reaction zone of the first vessel of 10 seconds or less, e.g., 1 second or less, 2 seconds or less, 3 seconds or less, 3.5 seconds or less, 4 seconds or less, 4.5 seconds or less, 5 seconds or less, 5.5 seconds or less, 6 seconds or less, 6.5 seconds or less, 7 seconds or less, 7.5 seconds or less, 8 seconds or less, 8.5 seconds or less, or 9 seconds or less. Without being bound by any theory, it is believed that it is preferable to maintain a short reaction time of the reactant amine and phosgene in order to avoid the formation of by-products as much as possible. The residence time of the reactant amine stream and the phosgene stream in the reaction zone of the first vessel can be controlled in various ways. For example, the residence time in the reaction zone of the first vessel can be controlled by controlling the flow rate of the reactant amine stream and / or the phosgene stream by a flow control device. For example, the reaction residence time in the first vessel is shortened or extended by increasing or decreasing the flow rate of the inert medium in the amine stream and / or the phosgene stream. For example, as the flow rate of the reactant amine stream and / or the phosgene stream increases, the residence time in the reaction zone of the first vessel decreases. Furthermore, in order to ensure that the reactant amine stream and the phosgene stream can complete the reaction in the shortest possible time, it is preferable to mix them as uniformly as possible, for example, by a suitable mixing device (e.g., a mixing unit or mixing zone, including dynamic or static mixing elements or mixing nozzles).

[0056]

[0072] In some embodiments, the flow rates of the reactant amine and phosgene are adjusted by the amine metering pump and the phosgene metering pump of the first vessel, respectively, so that the reactant amine and phosgene can be added to the first vessel at a constant rate for reaction. For example, the reactant amine (moles) is introduced into the first vessel at a constant rate of 1 to 5 moles / hour (e.g., 1 mole / hour, 2 moles / hour, 3 moles / hour, 4 moles / hour, 5 moles / hour, or any value within the range between any two of the above values), and the phosgene is introduced into the first vessel at a constant rate of 7 to 60 moles / hour (e.g., 7 moles / hour, 10 moles / hour, 20 moles / hour, 30 moles / hour, 40 moles / hour, 50 moles / hour, 60 moles / hour, or any value within the range between any two of the above values). Without being bound by any theory, it is believed that it is preferable to maintain constant flow rates of the reactants amine and phosgene so that the feed rates can be precisely controlled to ensure continuous production of isocyanate and to ensure the yield of isocyanate.

[0057]

[0073] In some embodiments, the reactant amine stream and phosgene stream of step (a) flow from top to bottom in the reaction zone of the first vessel and react during this process to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene.

[0058]

[0074] The phosgene stream and / or reactant amine stream of step (a) may also be passed into the first vessel simultaneously with or following the inert carrier gas. The inert carrier gas can promote the vaporization of the reactant amine, allowing for a more suitable dispersion effect. The inert carrier gas is a medium that exists in a gaseous state in the reaction vessel at the reaction temperature and does not react with the reactants or compounds present in the reaction process or is stable under the reaction conditions. Exemplary inert carrier gases include nitrogen, carbon dioxide, carbon monoxide, helium, or argon. In some embodiments, the inert carrier gas is preheated to 200°C to 600°C (e.g., 250°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 450°C, 500°C, 550°C, or a range between any two of the above values) before being passed into the first vessel. In some embodiments, the inert carrier gas (e.g., nitrogen) is passed into the first vessel at a constant rate of 2-7 L / hr (e.g., 2 L / hr, 3 L / hr, 3.5 L / hr, 4 L / hr, 4.48 L / hr, 4.5 L / hr, 5 L / hr, 5.5 L / hr, 6 L / hr, 6.5 L / hr, 7 L / hr, or any value within the range between any two of the above values). In some embodiments, the molar flow rate of the inert carrier gas is 10-100% (e.g., 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any value within the range between any two of the above values) of the molar flow rate of the reactant amine or phosgene. If the flow rate of the reactant amine stream is too low, the flow rate of the inert carrier gas is preferably increased to ensure adequate linear velocity.

[0059]

[0075] The first vessel may be any type of conventional reaction vessel known in the prior art, such as those disclosed in EP 289840 and EP 593334, suitable for non-catalytic homogeneous gas reactions, preferably for continuous non-catalytic homogeneous gas reactions, and capable of withstanding the moderate pressures required. The first vessel may be made of metal (e.g., steel, silver, or copper), glass, ceramic, or enamel. Preferably, steel reactors are used. The walls of the first vessel may be smooth or gently contoured (e.g., grooved or wrinkled).

[0060]

[0076] In some embodiments, the first vessel may be a tubular reactor. For example, the upper part of the tubular reactor is the reaction zone and the lower part is the quench zone. In addition to tubular reactors, essentially cuboid or cuboid reaction spaces, such as plate reactors, may also be used, as may reactors with any other desired cross-sectional shape.

[0061]

[0077] 2. Step (b)

[0078] In step (b) of the present application, the reaction product mixture obtained in step (a) is contacted with a first quench medium stream introduced into a quench zone of a first vessel and introduced into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel.

[0062]

[0079] To reduce or prevent the formation of by-products and inhibit the decomposition of the formed isocyanates, the reaction product mixture is cooled immediately after the reaction by contacting it with a first quenching medium stream introduced into a quenching zone of the first vessel. A preferred first quenching medium is a liquid quenching medium, which absorbs heat by evaporation and thus results in rapid cooling of the reaction product mixture. In some embodiments, the first quenching medium is present in a fine mist form so as to achieve rapid cooling of the reaction product mixture. For example, the reaction product mixture is cooled by the first quenching medium to a temperature between 110 and 150°C, for example, 110°C, 120°C, 130°C, 140°C, 150°C, or a range between any two of the above values.

[0063]

[0080] The "quench zone of the first vessel" in this application may also be another vessel separated from the first vessel, which has a similar function or effect, i.e., to provide a space for contact between the reaction product mixture and the first quench medium stream to cool the reaction product mixture and capture the target product isocyanate.

[0064]

[0081] In the art, commonly used quenching media include solvents, isocyanates, or mixtures of isocyanates and solvents. The first quenching media in the present application is selected from the group consisting of isocyanates, phosgene, hydrogen chloride, inert carrier gases, and any combination thereof. The product yield can be optimized by adjusting the flow rates of the first quenching media and the phosgene stream of step (a). The flow rate ratio of the first quenching media to the phosgene stream of step (a) can be adjusted to be 0.4:1 to 2:1 (e.g., 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or any value in the range between any two of the above ratios). For example, when a solvent (e.g., 1,2-dichlorobenzene) is used as the first quench medium, the flow ratio of the solvent (e.g., 1,2-dichlorobenzene) to the phosgene stream in step (a) is 0.4:1 to 0.6:1 (e.g., 0.54:1); when an isocyanate (e.g., PDI) is used as the first quench medium, the flow ratio of the isocyanate (e.g., PDI or HDI) to the phosgene stream in step (a) is 0.5:1 to 0.8:1 (e.g., 0.5:1 to 0.8:1); .68:1); when an inert carrier gas (e.g., nitrogen or carbon dioxide) is used as the first quench medium, the flow ratio of the inert carrier gas (e.g., nitrogen or carbon dioxide) to the phosgene stream in step (a) is 1.2:1 to 1.8:1 (e.g., 1.4:1 or 1.6:1); when hydrogen chloride is used as the first quench medium, the flow ratio of the hydrogen chloride to the phosgene stream in step (a) is 1.2:1 to 1.6:1 (e.g., 1.4:1).

[0065]

[0082] The inventors of the present application have also unexpectedly found that by using only phosgene as the first quench medium to cool the reaction product mixture obtained in step (a), the use of organic solvent in the whole reaction system can be avoided, and the problem of inlet blockage caused by solid adhesion can also be avoided, so that the whole method does not require the procedures of solvent recovery, rectification and recycle purification, and the preparation method is simple, has low energy consumption and low cost. Moreover, due to the shortened high-temperature purification step, the high-temperature residence time of the reaction product isocyanate is greatly shortened, the self-polymerization reaction is mitigated, and the product yield is high.

[0066]

[0083] In some embodiments, the first quench medium is not a solvent or does not contain a solvent. In some embodiments, the first quench medium is not an organic solvent (e.g., chlorobenzene, toluene, hexane, tetrahydrofuran, chloronaphthalene, etc.) or does not contain an organic solvent. In some embodiments, the first quench medium is not an isocyanate or does not contain an isocyanate.

[0067]

[0084] In some embodiments, in step (b), the temperature of the reaction product mixture obtained in step (a) is rapidly reduced by utilizing the latent heat of vaporization of the first quench medium. For example, the temperature of the reaction product mixture obtained in step (a) is rapidly reduced by the first quench medium, for example, at least 200° C. / sec. Without being bound by any theory, it is believed that it is preferable to rapidly reduce the temperature of the reaction product mixture obtained in step (a) to ensure the purity of the target product. If the temperature is not reduced in the shortest possible time, the reaction product mixture obtained in step (a) may undergo polymerization to generate impurities. The temperature of the reaction product mixture can be rapidly reduced in various ways, for example, by increasing the flow rate of the first quench medium, by reducing the initial temperature of the first quench medium, by improving the spray dispersion effect of the first quench medium to increase the heat exchange rate, etc.

[0068]

[0085] In some embodiments, the contact time of the reaction product mixture obtained in step (a) with the first quench medium stream in the quench zone of the first vessel is 1 second or less, e.g., 0.9 seconds or less, 0.8 seconds or less, 0.7 seconds or less, 0.6 seconds or less, 0.5 seconds or less, 0.4 seconds or less, 0.3 seconds or less, 0.2 seconds or less, or 0.1 seconds or less. Preferably, the contact time of the reaction product mixture obtained in step (a) with the first quench medium stream in the quench zone of the first vessel is between 0.2 seconds and 0.5 seconds.

[0069]

[0086] In some embodiments, step (b) is carried out under an absolute pressure of 0.05-0.2 Mpa (e.g., 0.06 Mpa, 0.07 Mpa, 0.08 Mpa, 0.09 Mpa, 0.1 Mpa, 0.11 Mpa, 0.12 Mpa, 0.13 Mpa, 0.14 Mpa, 0.15 Mpa, 0.16 Mpa, 0.17 Mpa, 0.18 Mpa, 0.19 Mpa, or a range between any two of the above values), preferably 0.05-0.12 Mpa, more preferably 0.08-0.1 Mpa.

[0070]

[0087] In some embodiments, the first quench medium is phosgene. In some embodiments, the first quench medium is liquid phosgene. In some embodiments, the first quench medium is pressurized liquid phosgene. Without being bound by any theory, it is believed that it is particularly advantageous to use pressurized liquid phosgene (e.g., the pressure is 0.5-2 MPa). Due to the high injection pressure of pressurized phosgene and the continuous boiling of some liquid phosgene on the inner wall surface, a layer of gas cushion film is formed, and the polymer cannot adhere to the inner wall, and solid precipitation and clogging of the reaction pipe are avoided. The pressure can be increased by increasing the flow rate of phosgene. For example, the flow rate of phosgene as the first quench medium is adjusted to 7-12 moles / hour (e.g., 7 moles / hour, 8 moles / hour, 9 moles / hour, 10 moles / hour, 11 moles / hour, 12 moles / hour, or any value in the range between any two of the above values). In some embodiments, the first quench medium is unused phosgene. In some embodiments, the first quench medium is recycled phosgene.

[0071]

[0088] In some embodiments, when the first quench medium is phosgene, the flow rate ratio of the first quench medium, phosgene, to the phosgene stream in step (a) is from 0.7:1 to 1.2:1 (e.g., 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, or any ratio within a range between any two of the above ratios).

[0072]

[0089] 3. Step (c)

[0090] The second vessel in step (b) includes a collection zone and a washing zone. In step (c) of the present application, the isocyanate is collected in the collection zone of the second vessel, and the hydrogen chloride, unreacted phosgene, and uncollected isocyanate (and optionally the inert carrier gas) are passed through the washing zone of the second vessel.

[0073]

[0091] As mentioned above, in step (b), the reaction product mixture is cooled by the first quench medium to a temperature between 110 and 150°C (e.g., 110°C, 120°C, 130°C, 140°C, 150°C, or a range between any two of the above values), whereby the target product isocyanate is liquefied and collected in the collection zone of the second vessel. However, at this temperature, the hydrogen chloride and unreacted phosgene in the reaction product mixture cannot be liquefied. Therefore, the hydrogen chloride, unreacted phosgene, and a small amount of unliquefied isocyanate are still in gaseous form and are fed into the washing zone of the second vessel.

[0074]

[0092] The collection zone and the washing zone of the second vessel can be arranged in any pattern. Preferably, the collection zone of the second vessel is located in the lower part of the second vessel, and the washing zone is located in the upper part of the second vessel. In some embodiments, the washing zone of the second vessel is a washing tower having at least one separator stage. In some embodiments, the isocyanate collected in the collection zone of the second vessel is pumped to the washing zone of the second vessel, thus realizing the circulation of the lower liquid. The circulation of the lower liquid has at least two advantages: it can relocate the agitation to realize the turbulence, dispersion, and homogenization of the liquid in the second vessel; it allows a stable output flow to the outside, thus making the following rectification tower operate more smoothly.

[0075]

[0093] 4. Step (d)

[0094] In step (d) of the present application, a second quench medium stream is introduced into the wash zone of the second vessel of step (c) and the hydrogen chloride, unreacted phosgene, and uncollected isocyanate (and optionally, the inert carrier gas) of step (c) are contacted with the second quench medium stream in the wash zone.

[0076]

[0095] In some embodiments, the second quench medium in step (d) is the same as the first quench medium in step (b), i.e., both are phosgene. In some embodiments, the second quench medium in step (d) is different from the first quench medium in step (b). For example, the second quench medium is an isocyanate, a solvent, or a mixture thereof. In some embodiments, the second quench medium is not a solvent or does not contain a solvent. In some embodiments, the second quench medium is not an organic solvent (e.g., chlorobenzene, toluene, hexane, tetrahydrofuran, chloronaphthalene, etc.) or does not contain an organic solvent. In some embodiments, the second quench medium is not an isocyanate or does not contain an isocyanate. In some embodiments, the second quench medium is a liquid. In some embodiments, the second quench medium is selected from the group consisting of liquid PDI, liquid HDI, liquid phosgene, liquid nitrogen, liquid carbon dioxide, or liquid hydrogen chloride. In some embodiments, the second quench medium is liquid phosgene. In some embodiments, both the first quench medium and the second quench medium are liquid phosgene.

[0077]

[0096] In some embodiments, the flow direction of the hydrogen chloride, unreacted phosgene, and uncollected isocyanate (and optionally the inert carrier gas) of step (c) and the flow direction of the second quench medium stream are reversed in the washing zone. For example, the hydrogen chloride, unreacted phosgene, and uncollected isocyanate (and optionally the inert carrier gas) flow from bottom to top, and the second quench medium flows from top to bottom, so that they come into complete contact, whereby the uncollected isocyanate of step (c) is condensed as much as possible from the gas phase stream. After the uncollected isocyanate of step (c) is treated in step (d), the isocyanate condensed to liquid is collected in the collection zone of the second vessel.

[0078]

[0097] In step (d), the washing conditions are controlled so that hydrogen chloride and unreacted phosgene (and optionally, inert carrier gas) overflow from the top of the second vessel, and uncollected isocyanate is refluxed to the collection zone of the second vessel. In this way, the yield of the target product isocyanate is maximized. For example, the hydrogen chloride and unreacted phosgene (and optionally, inert carrier gas) overflowing from the top of the second vessel is cooled to -5 to 20°C (e.g., 0°C, 5°C, 10°C, 15°C, 18°C, 19°C, or any temperature within the range between any two of the above values) by a cooler, and then passed through a pressure control system. Preferably, by controlling the temperature of the second quench medium and / or cooler to a moderately low range (e.g., 0-15°C, e.g., 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, or any temperature in the range between any two of the above values), the uncollected isocyanate of step (c) can be completely condensed and refluxed, while the hydrogen chloride and unreacted phosgene (and optionally the inert carrier gas) are not condensed and overflow from the top of the second vessel.

[0079]

[0098] In some embodiments, the hydrogen chloride overflowing from the top of the second vessel is passed through a pressure control system and then subjected to hydrogen chloride purification to form by-product hydrochloric acid. In some embodiments, the phosgene overflowing from the top of the second vessel is recycled to form the phosgene stream of step (a) or the first quench medium stream of step (b).

[0080]

[0099] In some embodiments, the method of preparing an isocyanate according to the present application further comprises step (e) in which the isocyanate collected in the collection zone of the second vessel is transferred into a purification apparatus for rectification to obtain a purified isocyanate. For clarity, step (e) is not a mandatory step in the method of the present application for preparing an isocyanate, provided that the purity of the isocyanate obtained by steps (b) and (d) is sufficiently high, e.g., 90% or more.

[0081]

[0100] According to the method for preparing isocyanate provided by the present invention, the use of organic solvent can be avoided, the whole method is solvent-free, and the reuse of phosgene is realized. Compared with the conventional method, the production cost is greatly reduced, the yield of isocyanate is improved, and the environmental pollution caused by organic solvent is also significantly reduced. In addition, the conversion rate of the isocyanate prepared by the method of the present invention can be up to 100%, and the selectivity can be up to 96% or more. "Conversion rate" refers to the ratio of the amount of reactant (e.g., reactant amine) detected after reaction and before purification by rectification to the amount of such reactant before reaction. "Selectivity" refers to the ratio of the actual target product measured by chromatographic analysis after reaction and before purification by rectification to the theoretical value of 100%.

[0082]

[0101] EXAMPLES

[0083]

[0102] In order that this invention may be more fully understood, the following examples are set forth. It should be understood that these examples are provided for illustrative purposes only and are not to be construed as limiting in any manner.

[0084]

[0103] Table 1 shows some abbreviations of the nouns mentioned in the examples.

[0085] [Table 1]

[0086]

[0104] The feeds, quenching media, conversions, and selectivities for the following examples are summarized in Table 2.

[0087] [Table 2]

[0088]

[0105] The steps and results of each example are described in detail below.

[0089]

[0106] Example 1: Synthesis of PDI

[0107] Example 1-1: PDA was used as the raw material, and 1,2-dichlorobenzene was used as the quench medium.

[0090]

[0108] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The mixed stream flowed from top to bottom through the reaction zone of the phosgenation reactor heated to 330°C (residence time 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly lowered by utilizing the latent heat of vaporization of the quench medium 1,2-dichlorobenzene, and the flow rate of the quench medium 1,2-dichlorobenzene (-10°C, 0.6 MPa) was 800g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, 1,2-dichlorobenzene was used to capture and absorb the target product. By weighing and liquid chromatography, the conversion rate of the reaction was 100% and the selectivity was 97.4%.

[0091]

[0109] Example 1-2: PDA was used as the raw material, and liquid PDI at -10°C was used as the quench medium.

[0092]

[0110] Phosgene and inert carrier gas were preheated to 330° C. 990 g / h (10 equivalents) of phosgene and 4.48 L / h of inert carrier gas (nitrogen) (i.e., 20 mol % of PDA) were mixed and initially introduced into the phosgenation reactor. After 10 minutes, PDA preheated to 330° C. was introduced into the phosgenation reactor at a rate of 102 g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330° C. for 3.5 seconds (i.e., the residence time was 3.5 seconds). The post-reaction mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the mixed gas after the reaction was rapidly lowered by utilizing the latent heat of vaporization of the quench medium (liquid PDI cooled to -10°C), and the flow rate of the quench medium PDI (-10°C, 0.5 MPa) was 1050g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, the liquid PDI cooled to -10°C was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.5%.

[0093]

[0111] Example 1-3: PDA was used as the raw material and liquid phosgene was used as the quench medium.

[0094]

[0112] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C in 3.5 seconds (i.e., the residence time was 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly cooled by utilizing the latent heat of vaporization of the quench medium (liquid phosgene), and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 800g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 99.3%.

[0095]

[0113] Examples 1-4: PDA was used as the raw material and liquid nitrogen was used as the quench medium.

[0096]

[0114] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C in 3.5 seconds (i.e., the residence time was 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid nitrogen), and the flow rate of the quench medium liquid nitrogen (-176°C, 0.5 MPa) was 450g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid nitrogen was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.2%.

[0097]

[0115] Examples 1-5: PDA was used as the raw material and liquid carbon dioxide was used as the quench medium.

[0098]

[0116] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C in 3.5 seconds (i.e., the residence time was 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid carbon dioxide), and the flow rate of the quench medium liquid carbon dioxide (-46°C, 0.7 MPa) was 600g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid carbon dioxide was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 92.1%.

[0099]

[0117] Examples 1-6: PDA was used as the raw material and liquid hydrogen chloride was used as the quench medium.

[0100]

[0118] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C in 3.5 seconds (i.e., the residence time was 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid hydrogen chloride), and the flow rate of the quench medium liquid hydrogen chloride (-40°C, 0.7 MPa) was 520g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid hydrogen chloride was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.1%.

[0101]

[0119] Examples 1-7: PDA hydrochloride was used as the raw material, and liquid phosgene was used as the quench medium.

[0102]

[0120] Phosgene and inert carrier gas were preheated to 330°C. 990 g / h (10 equivalents) of phosgene and 4.48 L / h of inert carrier gas (nitrogen) (i.e., 20 mol % of PDA hydrochloride) were mixed and initially introduced into the phosgenation reactor. After 10 minutes, gaseous PDA hydrochloride preheated to 330°C was introduced into the phosgenation reactor at a rate of 175 g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C for 3.5 seconds (i.e., the residence time was 3.5 seconds). The post-reaction mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the mixed gas after the reaction was rapidly lowered by utilizing the latent heat of vaporization of the quench medium (liquid phosgene), and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 800 g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100%, and the selectivity was 96.0%.

[0103]

[0121] Examples 1-8: The amount of phosgene was 12 equivalents, PDA was used as the raw material, and liquid phosgene was used as the quench medium.

[0104]

[0122] Phosgene and inert carrier gas were preheated to 330°C. 1188g / h (12 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of PDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, PDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 102g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 330°C in 3.5 seconds (i.e., the residence time was 3.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid phosgene), and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 850g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 98.8%.

[0105]

[0123] Example 2: Synthesis of HDI

[0124] Example 2-1: HDA was used as the raw material, and dichlorobenzene was used as the quench medium.

[0106]

[0125] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HDA preheated to 340°C was introduced into the phosgenation reactor at a rate of 116g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (dichlorobenzene), and the flow rate of the quench medium 1,2-dichlorobenzene (-10°C, 0.6 MPa) was 800g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, dichlorobenzene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.5%.

[0107]

[0126] Example 2-2: HDA was used as the raw material, and liquid HDI at -10°C was used as the quench medium.

[0108]

[0127] Phosgene and inert carrier gas were preheated to 340° C. 990 g / h (10 equivalents) of phosgene and 4.48 L / h of inert carrier gas (nitrogen) (i.e., 20 mol % of HDA) were mixed and initially introduced into the phosgenation reactor. After 10 minutes, HDA preheated to 340° C. was introduced into the phosgenation reactor at a rate of 116 g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed in 4.5 seconds through the reaction zone of the phosgenation reactor heated to 340° C. (i.e., the residence time was 4.5 seconds). The post-reaction mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the mixed gas after the reaction was rapidly lowered by utilizing the latent heat of vaporization of the quench medium (liquid HDI cooled to -10°C), and the flow rate of the quench medium liquid HDI (-10°C, 0.5 MPa) was 1050g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid HDI cooled to -10°C was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 93.1%.

[0109]

[0128] Example 2-3: HDA was used as the raw material and liquid phosgene was used as the quench medium.

[0110]

[0129] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HDA preheated to 340°C was introduced into the phosgenation reactor at a rate of 116g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid phosgene), and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 800g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 97.2%.

[0111]

[0130] Example 2-4: HDA was used as the raw material and liquid nitrogen was used as the quench medium.

[0112]

[0131] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HDA preheated to 340°C was introduced into the phosgenation reactor at a rate of 116g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid nitrogen), and the flow rate of the quench medium liquid nitrogen (-177°C, 0.5 MPa) was 450g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid nitrogen was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.3%.

[0113]

[0132] Example 2-5: HDA was used as the feedstock and liquid carbon dioxide was used as the quench medium.

[0114]

[0133] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HDA preheated to 340°C was introduced into the phosgenation reactor at a rate of 116g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium (liquid carbon dioxide), and the flow rate of the quench medium liquid carbon dioxide (-46°C, 0.7 MPa) was 600g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid carbon dioxide was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 91.1%.

[0115]

[0134] Example 2-6: HDA was used as the raw material and liquid hydrogen chloride was used as the quench medium.

[0116]

[0135] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HDA preheated to 340°C was introduced into the phosgenation reactor at a rate of 116g / h. The two reactant streams were mixed at the inlet of the reactor. Then, the stream was passed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). Then, the reacted mixed gas was fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly lowered by utilizing the latent heat of vaporization of the quench medium liquid hydrogen chloride, and the flow rate of the quench medium liquid hydrogen chloride (-40°C, 0.7 MPa) was 520g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid hydrogen chloride was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 90.1%.

[0117]

[0136] Examples 2-7: HDA hydrochloride was used as the raw material and liquid phosgene was used as the quench medium.

[0118]

[0137] Phosgene and inert carrier gas were preheated to 340°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HAD hydrochloride) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, gaseous HAD hydrochloride preheated to 340°C was introduced into the phosgenation reactor at a rate of 189g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 340°C in 4.5 seconds (i.e., the residence time was 4.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium liquid phosgene, and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 800g / h. The target product was cooled to 140°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 95.8%.

[0119]

[0138] Example 3: Synthesis of IPDI

[0139] Example 3-1: IPDA was used as the raw material, and liquid phosgene was used as the quench medium.

[0120]

[0140] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of IPDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, IPDA preheated to 330°C was introduced into the phosgenation reactor at a rate of 170g / h. The two reactant streams were mixed at the inlet of the reactor. The stream was then passed through the reaction zone of the phosgenation reactor heated to 330°C in 5 seconds (i.e., the residence time was 5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly lowered by utilizing the latent heat of vaporization of the quench medium liquid phosgene, and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 850g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 95.3%.

[0121]

[0141] Example 3-2: IPDA hydrochloride was used as the raw material, and liquid phosgene was used as the quench medium.

[0122]

[0142] Phosgene and inert carrier gas were preheated to 330°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of IPDA hydrochloride) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, gaseous IPDA hydrochloride preheated to 330°C was introduced into the phosgenation reactor at a rate of 243g / h. The two reactant streams were mixed at the inlet of the reactor. The stream was then passed through the reaction zone of the phosgenation reactor heated to 330°C in 5 seconds (i.e., the residence time was 5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly lowered by utilizing the latent heat of vaporization of the quench medium liquid phosgene, and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 900g / h. The target product was cooled to 130°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 94.8%.

[0123]

[0143] Example 4 Synthesis of HTDI

[0144] Example 4-1: HTDA was used as the raw material, and liquid phosgene was used as the quench medium.

[0124]

[0145] Phosgene and inert carrier gas were preheated to 350°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HTDA) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, HTDA preheated to 350°C was introduced into the phosgenation reactor at a rate of 128g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 350°C in 5.5 seconds (i.e., the residence time was 5.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium liquid phosgene, and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 850g / h. The target product was cooled to 150°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 96.3%.

[0125]

[0146] Example 4-2: HTDA hydrochloride was used as the raw material, and liquid phosgene was used as the quench medium.

[0126]

[0147] Phosgene and inert carrier gas were preheated to 350°C. 990g / h (10 equivalents) of phosgene and 4.48L / h of inert carrier gas (nitrogen) (i.e., 20 mol% of HTDA hydrochloride) were mixed and introduced into the phosgenation reactor initially. After 10 minutes, gaseous HTDA hydrochloride preheated to 350°C was introduced into the phosgenation reactor at a rate of 164g / h. The two reactant streams were mixed at the inlet of the reactor. The stream then flowed through the reaction zone of the phosgenation reactor heated to 350°C in 5.5 seconds (i.e., the residence time was 5.5 seconds). The reacted mixed gas was then fed into the quench zone of the phosgenation reactor. The temperature of the reacted mixed gas was rapidly reduced by utilizing the latent heat of vaporization of the quench medium liquid phosgene, and the flow rate of the quench medium liquid phosgene (-10°C, 0.5 MPa) was 900g / h. The target product was cooled to 150°C and then collected at the bottom of the reaction absorption vessel (collection vessel). In this method, liquid phosgene was used to capture and absorb the target product. By weighing and gas chromatography, the conversion rate of the reaction was 100% and the selectivity was 96.0%.

[0127]

[0148] Some embodiments of the present invention have been described above. However, it should be clearly pointed out that the present invention is not limited to those embodiments, and additions and modifications made to the disclosure clearly described in the present invention are included in the scope of the present invention. Furthermore, it should be understood that the features of the various embodiments described in the present invention are not mutually exclusive and can exist in various combinations and arrangements even if such combinations and arrangements are not explicitly stated, without departing from the spirit and scope of the present invention. Once a specific embodiment of the method for preparing an isocyanate has been described, it is clear to those skilled in the art that other embodiments incorporating the concept of the present application can be used. Therefore, the present application is not limited to a specific embodiment, but is defined by the spirit and scope of the appended claims.

Claims

1. 1. A method for preparing an isocyanate comprising the steps of: (a) providing a reactant amine stream and a phosgene stream and passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. to react therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene; (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel; (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing hydrogen chloride, unreacted phosgene, and uncollected isocyanate to the washing zone; (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone; Including, the first quench medium and the second quench medium are independently selected from the group consisting of isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof, and the flow ratio of the first quench medium to the phosgene stream of step (a) is from 0.4:1 to 2:1; The above method.

2. 1. A method for preparing an isocyanate comprising the steps of: (a) providing a reactant amine stream and a phosgene stream and passing them through a reaction zone of a first vessel having a temperature between 200° C. and 600° C. to react therein to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene; (b) contacting the reaction product mixture from step (a) with a first quench medium stream introduced into a quench zone of the first vessel and introducing the reaction product mixture into a second vessel through an inlet of the second vessel connected to the quench zone of the first vessel; (c) the second vessel of step (b) comprises a collection zone and a washing zone, collecting the isocyanate in the collection zone and passing hydrogen chloride, unreacted phosgene, and uncollected isocyanate to the washing zone; (d) introducing a second quench medium stream into a wash zone of the second vessel of step (c) and contacting the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) with the second quench medium stream in the wash zone; Including, the first quench medium is phosgene and the second quench medium is selected from the group consisting of an isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof; The above method.

3. (i) the reactant amine stream of step (a) is preheated to 200° C. to 600° C. by a first preheater before being passed into the first vessel; and / or the phosgene stream of step (a) is preheated to 200° C. to 600° C. by a second preheater before being passed into the first vessel; (ii) the reactant amine stream and / or phosgene stream of step (a) are present in gaseous or atomized form before, during, or after being passed into the first vessel; (iii) the reactant amine stream of step (a) and the phosgene stream are mixed in the headspace of the first vessel; (iv) the reactant amine stream of step (a) and the phosgene stream flow from top to bottom in the reaction zone of the first vessel and react during this process to obtain a reaction product mixture comprising isocyanate, hydrogen chloride, and unreacted phosgene; (v) the reactant amine stream and the phosgene stream of step (a) have a retention time in the reaction zone of the first vessel of 260 seconds or less; (vi) the phosgene stream of step (a) is in stoichiometric excess based on the amino groups of the reactant amine stream; (vii) the feed ratio (in molar terms) of the phosgene stream to the reactant amine stream in step (a) is from 7:1 to 15:1; and / or (viii) the phosgene stream and / or the reactant amine stream of step (a) are passed into the first vessel simultaneously with or following the inert carrier gas; Optionally, the inert carrier gas is preheated to between 200° C. and 600° C. before being passed into the first vessel; and / or Optionally, the molar flow rate of the inert carrier gas is 10 to 100% of the molar flow rate of the reactant amine or phosgene stream; The method according to claim 1 or 2.

4. The method of any one of claims 1 to 3, wherein the first quench medium in step (b) and the second quench medium in step (d) are the same.

5. The method of any one of claims 1 to 3, wherein the first quench medium in step (b) and the second quench medium in step (d) are different.

6. the first quench medium of step (b) and / or the second quench medium of step (d) are free of organic solvent; Optionally, the first quench medium in step (b) is liquid phosgene; Optionally, the second quench medium is a liquid; and / or Optionally, both the first quench medium and the second quench medium are liquid phosgene; The method according to any one of claims 1 to 5.

7. 7. The method according to any one of claims 1 to 6, wherein in step (b), the temperature of the reaction product mixture obtained in step (a) is rapidly reduced by utilizing the latent heat of vaporization of the first quench medium.

8. In step (d), the flow directions of the hydrogen chloride, unreacted phosgene, and uncollected isocyanate of step (c) and the flow direction of the second quench medium stream are reversed in the wash zone; Optionally, the wash conditions are configured to allow hydrogen chloride and unreacted phosgene (and optionally, the inert carrier gas) to overflow from the top of the second vessel and allow uncollected isocyanate to reflux into a collection zone of the second vessel; Optionally, the hydrogen chloride and unreacted phosgene (and optionally the inert carrier gas) overflowing from the top of the second vessel are cooled to −5 to 20° C. by a condenser and passed through a pressure control system; Optionally, the washing conditions are controlling the temperature of the second quench medium and / or the cooler within the range of 0-15°C; Optionally, the hydrogen chloride overflowing from the top of the second vessel is passed through a pressure control system and then subjected to hydrogen chloride purification to form a by-product hydrochloric acid; and / or Optionally, phosgene overflowing from the top of the second vessel is recycled to form the phosgene stream of step (a) or the first quench medium stream of step (b); The method according to any one of claims 1 to 7.

9. (i) the isocyanate is a diisocyanate; (ii) the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate; (iii) the isocyanate is selected from the group consisting of methylene diphenyl diisocyanate, either as a pure isomer or as a mixture of isomers, toluene diisocyanate, either as a pure isomer or as 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 / or (iv) the isocyanate is PDI, HDI, IPDI, or HTDI; The method according to any one of claims 1 to 8.

10. The reactant amine has the structural formula R(NH ２ ) ｎ where n is 1, 2, or 3 and R is an aliphatic hydrocarbyl group or an aromatic hydrocarbyl group; optionally, n is 2 and R is an aliphatic hydrocarbyl group; optionally, n is 2 and R is an aliphatic hydrocarbyl group having 2 to 10 carbon atoms; optionally, n is 2 and R is a linear or cyclic aliphatic hydrocarbyl group having 3 to 10 carbon atoms; Optionally, the reactant amine is present in free form; Optionally, the reactant amine is present as an amine salt; Optionally, the amine salt is selected from the group consisting of hydrochloride, sulfate, hydrogen sulfate, nitrate, and carbonate; and / or Optionally, 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; The method according to any one of claims 1 to 9.

11. 11. The method of any one of claims 1 to 10, wherein the reactant amine is selected from the group consisting of PDA, PDA hydrochloride, HDA, HDA hydrochloride, IPDA, IPDA hydrochloride, HTDA, and HTDA hydrochloride, the first quench medium is liquid phosgene, and the second quench medium is selected from the group consisting of liquid PDI, liquid HDI, liquid phosgene, liquid nitrogen, liquid carbon dioxide, and liquid hydrogen chloride.

12. 12. The method of claim 11, wherein both the first quench medium and the second quench medium are liquid phosgene.

13. 13. The process according to any one of claims 2 to 12, wherein the flow ratio of the first quench medium, phosgene, to the phosgene stream in step (a) is from 0.7:1 to 1.2:1.

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