CN113105364A - Method and system for preparing isocyanate - Google Patents

Method and system for preparing isocyanate Download PDF

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Publication number
CN113105364A
CN113105364A CN202110377999.1A CN202110377999A CN113105364A CN 113105364 A CN113105364 A CN 113105364A CN 202110377999 A CN202110377999 A CN 202110377999A CN 113105364 A CN113105364 A CN 113105364A
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reaction vessel
reaction
phosgene
temperature
gas
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CN113105364B (en
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曹利峰
陆成樑
刘文杰
邱贵森
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Guang'an Mojia Biotechnology Co ltd
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Guang'an Mojia Biotechnology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C269/00—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups
    • C07C269/04—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups from amines with formation of carbamate groups
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/04—Preparation of derivatives of isocyanic acid from or via carbamates or carbamoyl halides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C269/00—Preparation of derivatives of carbamic acid, i.e. compounds containing any of the groups, the nitrogen atom not being part of nitro or nitroso groups

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  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The present application relates to a process and system for preparing isocyanates. Specifically, the methods and systems described herein prepare isocyanates by recovering and recycling excess phosgene.

Description

Method and system for preparing isocyanate
Technical Field
The present application relates to a method and system for preparing isocyanates, and more particularly, to a method and system for preparing isocyanates using a phosgene liquid phase process.
Background
Isocyanates are a class of compounds containing one or more isocyanate groups. Including aliphatic isocyanate, aromatic isocyanate, unsaturated isocyanate, halogenated isocyanate, thioisocyanate, phosphorus-containing isocyanate, inorganic isocyanate, blocked isocyanate and the like. Because it contains highly unsaturated isocyanate group, it has high chemical activity, and can produce important chemical reaction with several substances, so that it can be extensively used in the fields of polyurethane, polyurethane urea and polyurea, high-molecular modification, organic synthetic reagent, agriculture and medicine, etc.
The principle of the preparation of isocyanates from phosgene and amines is well known in the prior art, and is largely divided into liquid-phase and gas-phase processes. The gas phase method is to directly react gasified amine with gaseous phosgene to prepare isocyanate, and is not suitable for heat-sensitive amine because the amine needs to be gasified at high temperature, and urea byproducts are easily generated because the gas phase reaction speed is high. A typical liquid phase process involves three main chemical reactions, the first reaction being the reaction of an amine with phosgene to produce carbamoyl chloride and carbamoyl chloramine hydrochloride, the second reaction being the continued reaction of carbamoyl chloramine hydrochloride with phosgene to produce carbamoyl chloride, and the third reaction being the further reaction of carbamoyl chloride to produce isocyanate and hydrogen chloride.
When the isocyanate is actually produced by adopting the phosgene-liquid phase method, the yield of the isocyanate is increased by increasing the ratio of phosgene to amine (i.e. by making phosgene excessive), which results in that a large amount of phosgene is needed in the reaction process, and the production cost, the safety cost and the tail gas pollution environmental treatment cost are increased. Therefore, there is a need for an improved isocyanate production process that reduces the phosgene requirements during production.
Disclosure of Invention
The purpose of the application is to provide a method and a system for preparing isocyanate, which recycle phosgene in the reaction process, thereby reducing the phosgene requirement in the production process of isocyanate.
In one aspect, the present application provides a process for the preparation of isocyanates, characterized in that it comprises the steps of:
(a) mixing reactant amine and phosgene, and carrying out a first reaction in a first reaction vessel at the temperature of-30-90 ℃ to obtain a first reaction product;
(b) transferring the first reaction product obtained in the step (a) into a second reaction container, mixing the first reaction product with phosgene, and carrying out a second reaction in the second reaction container at the temperature of 90-200 ℃ to obtain a second reaction product;
(c) transferring the second reaction product obtained in the step (b) into a third reaction container, mixing the second reaction product with phosgene, and carrying out a third reaction in the third reaction container at the temperature of 120-250 ℃ to obtain a third reaction product;
(d) transferring the third reaction product obtained in the step (c) into a fourth reaction container, mixing the third reaction product with phosgene, and carrying out a fourth reaction in the fourth reaction container at a certain constant temperature of 120-300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein at least a portion of said phosgene in step (b) is derived from said off-gas of said fourth reaction vessel in step (d) and at least a portion of said phosgene in step (c) is derived from said off-gas of said first reaction vessel in step (a); alternatively, at least a portion of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
In certain embodiments, the off-gas of the first reaction vessel in step (a) comprises phosgene that has not reacted to completion in step (a); the off-gas from the third reaction vessel in step (c) comprises hydrogen chloride and the phosgene that has not reacted to completion in step (c), and optionally, the phosgene that has not reacted to completion in step (a), the phosgene that has not reacted to completion in step (d); and/or the off-gas of the fourth reaction vessel in step (d) comprises hydrogen chloride and the incompletely reacted phosgene in step (d).
In certain embodiments, the phosgene content (w/w) in the off-gas of the first reaction vessel in step (a) is 90% or more. In certain embodiments, the phosgene content (w/w) in the off-gas of the third reaction vessel in step (c) is 60% or less. In certain embodiments, the phosgene content (w/w) in the tail gas of the fourth reactor in step (d) is 95% or greater.
In certain embodiments, the first reaction product comprises the intermediate carbamoylchloramine hydrochloride, and optionally, one or more selected from the group consisting of: carbamoyl chloride, unreacted amine from step (a) and phosgene.
In certain embodiments, the second reaction product comprises carbamoyl chloride and hydrogen chloride, and optionally, one or more selected from the group consisting of: the unreacted amine and phosgene in step (a), and the unreacted intermediate carbamoylchloramine hydrochloride and phosgene in step (b).
In certain embodiments, the third reaction product comprises isocyanate and hydrogen chloride, and optionally, one or more selected from the group consisting of: the unreacted amine and phosgene in step (a), the unreacted intermediate carbamoylchloramine hydrochloride in step (b), hydrogen chloride and phosgene, and the unreacted carbamoylchloride and phosgene in step (c).
In certain embodiments, the fourth reaction product comprises an isocyanate, and optionally, one or more selected from the group consisting of: hydrogen chloride, the incomplete amine and phosgene reaction in step (a), the incomplete intermediate carbamoylchloramine hydrochloride reaction in step (b), hydrogen chloride and phosgene, the incomplete carbamoylchloride and phosgene reaction in step (c), and the incomplete phosgene reaction in step (d).
In some embodiments, before step (a), a solvent of reactant amine is put into the first reaction vessel and cooled to 0-10 ℃ under the protection of nitrogen.
In certain embodiments, all of the phosgene in step (b) is derived from the off-gas of the fourth reaction vessel in step (d), and/or all of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a); alternatively, all of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and/or all of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
In certain embodiments, the flow rates of the reactant amine and phosgene are adjusted using the amine metering pump and phosgene metering pump of the first reaction vessel, respectively, such that the reactant amine and phosgene are fed into the first reaction vessel for reaction at a constant rate.
In some embodiments, the first reaction in step (a) is carried out in two temperature ranges, wherein the reaction temperature in the first stage is maintained at 30-50 ℃, and the reaction temperature in the second stage is further increased to 50-90 ℃.
In certain embodiments, the total amount of reactant amine and phosgene used in step (a), step (b), step (c), and step (d) is fed in a molar ratio of 1:4 to 1: 8.
In certain embodiments, the methods described herein further comprise the steps of: (e) and (d) transferring the fourth reaction product obtained in the step (d) into a purification device for rectification to obtain purified isocyanate.
In certain embodiments, the reaction of each step is carried out under atmospheric conditions.
In certain embodiments, phosgene is used in stoichiometric excess of 0% to 150% over theoretical based on amine groups of the reactant amine in the first reaction vessel.
In certain embodiments, at least a portion of the reactant amine in step (a) is dissolved in a solvent, wherein the solvent comprises one or more selected from the group consisting of: chlorobenzene, o-dichlorobenzene, toluene, xylene, perchloroethylene, trichlorofluoromethane and butyl acetate.
In certain embodiments, the reactant amine has the formula R (NH)2)nWherein n is 1, 2 or 3 and R is an aliphatic, alicyclic or aromatic hydrocarbon group having 2 to 10 carbon atoms.
In certain embodiments, the reactant amine is selected from one or more of the following: ethylamine, butylamine, pentamethylene diamine, hexamethylene diamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluene diamine, 1, 5-naphthalenediamine, diphenylmethane diamine, dicyclohexylmethane diamine, m-cyclohexyldimethylene diamine, isophorone diamine, trans-1, 4-cyclohexanediamine.
In certain embodiments, the isocyanate is selected from the group consisting of: diphenylmethane diisocyanate as a pure isomer or as a mixture of isomers, toluene diisocyanate as a pure isomer or as a mixture of isomers, 2, 6-xylene isocyanate, 1, 5-naphthalene diisocyanate, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, tert-butyl isocyanate, amyl isocyanate (e.g., pentamethylene diisocyanate), tert-amyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexamethylene diisocyanate), cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate (e.g., p-phenylene diisocyanate).
In another aspect, the present application provides a system for preparing isocyanate, characterized by comprising a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel and a temperature control device, wherein the first reaction vessel comprises: a solvent feed port, a phosgene feed port, a reactant amine feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the first reaction vessel; a sampling port configured to operably extract a volume of reaction sample from the first reaction vessel; the second reaction vessel, the third reaction vessel and the fourth reaction vessel each comprise: a phosgene feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the second, third or fourth reaction vessel, respectively; a sampling port configured to operably extract a volume of reaction sample from the second, third, or fourth reaction vessel; wherein the temperature control device is configured to optionally adjust the temperature of the first, second, third, and fourth reaction vessels to a predetermined value; wherein the air vent of the first reaction vessel is selectively communicated with an emergency discharging device, and the discharge port of the first reaction vessel is selectively communicated with the discharge port of the second reaction vessel; the air vent of the second reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the second reaction vessel is selectively communicated with the discharge hole of the third reaction vessel; the air vent of the third reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the third reaction vessel is selectively communicated with the discharge hole of the fourth reaction vessel; the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and the tail gas discharge of the first reaction vessel is in selective communication with the third reaction vessel and the tail gas discharge of the fourth reaction vessel is in selective communication with the second reaction vessel; or the tail gas discharge port of the first reaction vessel and the tail gas discharge port of the fourth reaction vessel are selectively communicated with the third reaction vessel, and the tail gas discharge port of the third reaction vessel is selectively communicated with the second reaction vessel.
In certain embodiments, the off-gas discharge of the first reaction vessel is in selective communication with the phosgene feed inlet of the third reaction vessel, and the off-gas discharge of the fourth reaction vessel is in selective communication with the phosgene feed inlet of the second reaction vessel; or the tail gas discharge port of the first reaction container and the tail gas discharge port of the fourth reaction container are selectively communicated with the phosgene feed port of the third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the phosgene feed port of the second reaction container.
In certain embodiments, the discharge ports of the first, second, third, and/or fourth reaction vessels are each in selective communication with an emergency discharge device.
In certain embodiments, the first reaction vessel is provided with a first precooler in communication with its solvent feed or tail gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its tail gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its tail gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its tail gas discharge.
In some embodiments, the temperature control device comprises a temperature sensor, the temperature sensor is a contact temperature sensor and/or a non-contact temperature sensor, wherein the contact temperature sensor can be arranged at any one or more of the following positions: the first reaction vessel interior, the side wall of the first reaction vessel, the second reaction vessel interior, the side wall of the second reaction vessel, the third reaction vessel interior, the side wall of the third reaction vessel, the fourth reaction vessel interior, and the side wall of the fourth reaction vessel; the non-contact temperature sensor is arranged at a distance from the first reaction vessel, and/or the second reaction vessel, and/or the third reaction vessel, and/or the fourth reaction vessel.
In some embodiments, the temperature control device further comprises: heat exchange means attachable to or formed by the side walls of the first, second, third and fourth reaction vessels for heat exchange with reactants within the first, second, third and fourth reaction vessels; and a temperature controller coupled to the temperature sensor and the heat exchange assembly, the temperature controller configured to receive a measurement signal of the temperature sensor and operate the heat exchange device according to the measurement signal.
In certain embodiments, the first, second, third, and fourth reaction vessels are selected from the group consisting of: carbon steel reation kettle, stainless steel reation kettle, enamel reactor, steel lining reation kettle. In some embodiments, the side walls of the first, second, third and fourth reaction vessels are provided with viewing holes for visually viewing the interiors of the first, second, third and fourth reaction vessels.
In certain embodiments, the system further comprises one or more of the following components: stirring subassembly, measurement pumping mechanism, tail gas processing apparatus and purification device. The stirring assembly may be disposed within the first reaction vessel, the second reaction vessel, the third reaction vessel, and/or the fourth reaction vessel. In certain embodiments, the agitator assembly comprises an agitator shaft and a plurality of blades extending laterally outward from the agitator shaft, the agitator shaft configured to operably effect one or more of the following motions: rotation, translation, and oscillation.
In certain embodiments, the metering pumping mechanism is disposed upstream of one or more of the following openings: the solvent feed, phosgene feed, reactant amine feed of the first reaction vessel, and the phosgene feed of the second, third, and fourth reaction vessels are used to control the amount of reactants pumped through these openings.
In certain embodiments, the off-gas treatment device of the first reaction vessel is used directly to the third reaction vessel and the off-gas treatment device of the fourth reaction vessel is used directly to the second reaction vessel. In certain embodiments, the off-gas treatment device of the first reaction vessel and the off-gas treatment device of the fourth reaction vessel are both applied directly to the third reaction vessel, and the off-gas treatment device of the third reaction vessel is applied directly to the second reaction vessel.
In certain embodiments, the purification device is connected downstream of the fourth reaction vessel.
In certain embodiments, a first transfer pump is disposed between the discharge outlet of the first reaction vessel and the discharge outlet of the second reaction vessel, the first transfer pump operable to pump the first reaction product between the discharge outlet of the first reaction vessel and the discharge outlet of the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the first reaction vessel with the discharge port of the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a second transfer pump is disposed between the discharge outlet of the second reaction vessel and the discharge outlet of the third reaction vessel, the second transfer pump operable to pump a second reaction product between the discharge outlet of the second reaction vessel and the discharge outlet of the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the second reaction vessel with the discharge port of the third reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a third transfer pump is disposed between the discharge ports of the third and fourth reaction vessels, the third transfer pump operable to pump a third reaction product between the discharge ports of the third and fourth reaction vessels; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the third reaction vessel with the discharge port of the fourth reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a fifth transfer pump is disposed between the off-gas treatment device of the first reaction vessel and the third reaction vessel, the fifth transfer pump operable to pump off-gas from the first reaction vessel between the off-gas treatment device of the first reaction vessel and the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the tail gas treatment device of the first reaction vessel and the third reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a sixth transfer pump is disposed between the off-gas treatment device of the fourth reaction vessel and the second reaction vessel, the sixth transfer pump operable to pump off-gas from the fourth reaction vessel between the off-gas treatment device of the fourth reaction vessel and the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the tail gas treatment device of the fourth reaction vessel and the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a seventh transfer pump is disposed between the off-gas treatment device of the fourth reaction vessel and the third reaction vessel, the seventh transfer pump operable to pump off-gas from the fourth reaction vessel between the off-gas treatment device of the fourth reaction vessel and the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the tail gas treatment device of the fourth reaction vessel with the third reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, an eighth transfer pump is disposed between the off-gas treatment device of the third reaction vessel and the second reaction vessel, the eighth transfer pump operable to pump off-gas from the third reaction vessel between the off-gas treatment device of the third reaction vessel and the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the tail gas treatment device of the third reaction vessel with the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
In certain embodiments, a first attemperator is disposed upstream of the phosgene feed inlet of the first reaction vessel, through which phosgene optionally enters the first reaction vessel. In certain embodiments, the first attemperator is connected to the first transfer pump, which switchably pumps the first reaction product to the discharge of the second reaction vessel or the first attemperator.
In certain embodiments, a second attemperator is disposed upstream of the phosgene feed inlet of the second reaction vessel, through which phosgene optionally enters the second reaction vessel. In certain embodiments, the second attemperator is connected to the second transfer pump, which switchably pumps the second reaction product downstream of the second attemperator or second reaction vessel.
In certain embodiments, a third attemperator is disposed upstream of the phosgene feed inlet of the third reaction vessel, through which phosgene optionally enters the third reaction vessel. In certain embodiments, the third attemperator is connected to the third transfer pump, which switchably pumps a third reaction product downstream of the third attemperator or third reaction vessel.
In certain embodiments, a fourth attemperator is disposed upstream of the phosgene feed inlet of the fourth reaction vessel, through which phosgene optionally enters the fourth reaction vessel. In certain embodiments, the fourth attemperator is connected to the fourth transfer pump, which switchably pumps a fourth reaction product downstream of the fourth attemperator or fourth reaction vessel.
By the method and the system for preparing the isocyanate, the required amount of phosgene in the preparation process of the isocyanate can be obviously reduced, so that the cost is saved for preparing the isocyanate on a large scale, and the pollution to the environment is reduced.
The foregoing is a summary of the application that may be simplified, generalized, and details omitted, and thus it should be understood by those skilled in the art that this section is illustrative only and is not intended to limit the scope of the application in any way. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
Drawings
The above-described and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It is appreciated that these drawings depict only several embodiments of the disclosure and are therefore not to be considered limiting of its scope. The contents of the present application will be described more specifically and in detail with reference to the accompanying drawings.
FIG. 1 shows a schematic block diagram of a system for preparing isocyanates according to one embodiment of the present application.
FIG. 2 shows a schematic block diagram of a system for preparing isocyanates according to another embodiment of the present application.
FIG. 3 shows a schematic block diagram of a system 10 for preparing isocyanates according to another embodiment of the present application.
FIG. 4 shows a schematic block diagram of a system 20 for preparing isocyanates according to another embodiment of the present application.
List of reference numerals:
10. 20-a reaction system;
100-first reaction vessel: 111a,111 b-solvent feed, 111c,111 d-vent gas, 112a,112 b-phosgene feed, 113-reactant amine feed, 120-vent, 140-vent, 150-sample, 160-sight, 170-stirring assembly, 171-stirring shaft, 172-blade;
200-second reaction vessel: 211a,211 b-tail gas discharge port, 212a,212 b-phosgene feed port, 220-discharge port, 240-vent port, 250-sampling port, 260-observation port, 270-stirring component, 271-stirring shaft and 272-blade;
300-third reaction vessel: 311a,311 b-tail gas discharge port, 312a,312 b-phosgene feed port, 320-discharge port, 340-vent port, 350-sampling port, 360-observation port, 370-stirring component, 371-stirring shaft and 372-blade;
400-fourth reaction vessel: 411a,411 b-tail gas discharge port, 412a,412 b-phosgene feed port, 420-discharge port, 440-vent port, 450-sampling port, 460-observation port, 470-stirring component, 471-stirring shaft and 472-blade;
500-temperature control device: 510. 520,530, 540-heat exchange means;
610. 620, 630-material transferring observation window;
710-first precooler, 720-second precooler, 730-third precooler, 740-fourth precooler;
810. 820, 830, 840-tail gas treatment device; 850-purification means;
910-first thermostat, 920-second thermostat, 930-third thermostat, 940-fourth thermostat;
181-amine metering pump, 182-first phosgene metering pump, 280-second phosgene metering pump, 380-third phosgene metering pump and 480-third phosgene metering pump;
190-first material transferring pump, 290-second material transferring pump, 390-third material transferring pump, 490-fourth material transferring pump
Detailed Description
The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter of the present application. It will be understood that aspects of the present disclosure, as generally described in the present disclosure and illustrated in the figures herein, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which form part of the present disclosure.
1.Method for producing isocyanates
In one aspect, the present application provides a process for the preparation of isocyanates, characterized in that it comprises the steps of:
(a) mixing reactant amine and phosgene, and carrying out a first reaction in a first reaction vessel at the temperature of-30-90 ℃ to obtain a first reaction product;
(b) transferring the first reaction product obtained in the step (a) into a second reaction container, mixing the first reaction product with phosgene, and carrying out a second reaction in the second reaction container at the temperature of 90-200 ℃ to obtain a second reaction product;
(c) transferring the second reaction product obtained in the step (b) into a third reaction container, mixing the second reaction product with phosgene, and carrying out a third reaction in the third reaction container at the temperature of 120-250 ℃ to obtain a third reaction product;
(d) transferring the third reaction product obtained in the step (c) into a fourth reaction container, mixing the third reaction product with phosgene, and carrying out a fourth reaction in the fourth reaction container at a certain constant temperature of 120-300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein at least a portion of said phosgene in step (b) is derived from said off-gas of said fourth reaction vessel in step (d) and at least a portion of said phosgene in step (c) is derived from said off-gas of said first reaction vessel in step (a); alternatively, at least a portion of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
In the present application, "isocyanate" refers to a class of compounds containing one or more isocyanate groups (R-N ═ C ═ O), including aliphatic isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorus-containing isocyanates, inorganic isocyanates, blocked isocyanates, and the like. In certain embodiments, "isocyanate" herein includes aromatic isocyanates, aliphatic isocyanates, for example, aromatic isocyanates include diphenylmethylene diisocyanate as a pure isomer or as a mixture of isomers, toluene diisocyanate as a pure isomer or a mixture of isomers, 2, 6-xylene isocyanate, 1, 5-naphthalene diisocyanate, and the like. Aliphatic isocyanates include methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, t-butyl isocyanate, amyl isocyanate, t-amyl isocyanate, isoamyl isocyanate, neopentyl isocyanate, hexyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, and the like. In certain embodiments, the isocyanates herein are selected from the group consisting of: pentamethylene diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate and toluene diisocyanate.
The step (a), the step (b), the step (c) and the step (d) of the method for producing an isocyanate described herein are described in detail, respectively.
1.1Step (a)
In step (a) of the present application, the reactants amine and phosgene are mixed and a first reaction is carried out at a temperature of-30 ℃ to 90 ℃ in a first reaction vessel to obtain a first reaction product.
Isocyanates are generally prepared by reacting amines with phosgene. The reaction of the amine with phosgene is usually carried out in stages. First, carbamoyl chlorides (RNHCOCl) are formed from amines and phosgene at low temperatures and subsequently converted at elevated temperatures to the corresponding isocyanates (R-N ═ C ═ O), with hydrogen chloride being eliminated in both steps.
In the present application, "reactant amine" means that the starting material for the preparation of isocyanates contains amino groups (-NH)2) A compound of the group. For example, in certain embodiments, the reactant amine has the formula R (NH)2)nWherein n is 1, 2 or 3 and R is an aliphatic, cycloaliphatic or aromatic hydrocarbon group having from 2 to 10 carbon atoms (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10 carbon atoms).
In certain embodiments, the reactant amine is a primary amine, i.e., contains NH2A group. In certain embodiments, the reactant amine is a diamine, i.e., contains 2 NH2A group. In certain embodiments, the reactant amine is selected from one or more of the following: ethylamine, butylamine, pentamethylene diamine, hexamethylene diamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluene diamine, 1, 5-naphthalenediamine, diphenylmethane diamine, dicyclohexylmethane diamine, m-cyclohexyldimethylene diamine, isophorone diamine, trans-1, 4-cyclohexanediamine. In certain embodiments, the reactant amine is selected from one or more of the following: pentanediamines (e.g., 1, 5-dipentylamine), hexanediamines (e.g., 1, 6-hexanediamine), p-phenylenediamine, and toluenediamine.
The first reaction, which is carried out in the first reaction vessel of step (a), is a reaction of the reactants amine and phosgene at a temperature of-30 ℃ to 90 ℃ (e.g., -30 ℃ to 10 ℃, -30 ℃ to 20 ℃, -30 ℃ to 30 ℃, -20 ℃ to 40 ℃, -10 ℃ to 50 ℃, 0 ℃ to 60 ℃, 0 ℃ to 70 ℃, 0 ℃ to 80 ℃, 0 ℃ to 90 ℃, etc.) to form a first reaction product. The first reaction product comprises the intermediate carbamoylchloramine hydrochloride and, in some cases, the first reaction product further comprises the incompletely reacted amine of step (a) and phosgene. In some cases, the first reaction product further comprises carbamoyl chloride.
Taking pentanediamine and phosgene as initial reaction raw materials as examples, the reaction carried out in the first reaction vessel is as follows:
Figure BDA0003011563480000111
in certain embodiments, the first reaction described in step (a) is performed in two temperature ranges, respectively, wherein the reaction temperature in the first stage is maintained at 30 to 50 ℃ (e.g., 35 ℃, 36 ℃, 37 ℃, 38 ℃, 39 ℃, 40 ℃,41 ℃, 42 ℃, 43 ℃, 44 ℃, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃), and the reaction temperature in the second stage is further increased to 50 to 90 ℃ (e.g., 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃).
In some embodiments, prior to step (a), a solvent for the reactant amine is introduced into the first reaction vessel and cooled to 0-10 ℃ (e.g., 0 ℃,1 ℃,2 ℃,3 ℃,4 ℃,5 ℃,6 ℃, 7 ℃,8 ℃, 9 ℃, 10 ℃) under nitrogen protection. In certain embodiments, at least a portion of the reactant amine in step (a) is dissolved in a solvent, wherein the solvent comprises one or more selected from the group consisting of: chlorobenzene, o-dichlorobenzene, toluene, xylene, perchloroethylene, trichlorofluoromethane and butyl acetate. In the present application, the preferred solvent for the reactant amine is ortho-dichlorobenzene or chlorobenzene.
The preparation of isocyanates often requires the input of large excesses of phosgene, since, at insufficient phosgene concentrations, the isocyanate formed and the excess amine form urea or other solid by-products of high viscosity. In certain embodiments, the total amount of reactant amine and phosgene used in step (a), step (b), step (c), and step (d) is, for example, charged at a molar ratio of 1:4 to 1:8 (e.g., 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, or a range between any two of the above values) throughout the reaction. In certain embodiments, phosgene is used in the first reaction vessel in a stoichiometric excess of 0% to 150% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, etc.) of theoretical based on the amine groups of the reactant amine. Thus, the off-gas of the first reaction vessel in step (a) comprises the phosgene that has not reacted to completion in step (a), e.g. those phosgene in stoichiometric excess. In certain embodiments, the phosgene content (w/w) in the off-gas of the first reaction vessel in step (a) is 90% or more (e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%).
In certain embodiments, the flow rates of the reactant amine and phosgene are adjusted using the amine metering pump and phosgene metering pump of the first reaction vessel, respectively, such that the reactant amine and phosgene are fed into the first reaction vessel for reaction at a constant rate. For example, reactant amine is added to the first reaction vessel at a constant rate of 5 to 7kg/hr (e.g., 5kg/hr, 5.5kg/hr, 6kg/hr, 6.1kg/hr, 6.2kg/hr, 6.3kg/hr, 6.4kg/hr, 6.5kg/hr, 6.6kg/hr, 6.7kg/hr, 6.8kg/hr, 6.9kg/hr, 7kg/hr, or a range between any two of the foregoing values), phosgene is added to the first reaction vessel at a constant rate of 1-3kg/hr (e.g., 1kg/hr, 1.5kg/hr, 2kg/hr, 2.1kg/hr, 2.2kg/hr, 2.3kg/hr, 2.4kg/hr, 2.5kg/hr, 2.6kg/hr, 2.7kg/hr, 2.8kg/hr, 2.9kg/hr, 3kg/hr, or a range between any two of the foregoing). Without being bound by any theory, it is believed that maintaining a constant flow rate of the reactants amine and phosgene is preferred because it allows for precise control of the charge and ensures continuous production of isocyanate and yield of isocyanate.
1.2Step (b)
In the step (b) of the present application, the first reaction product obtained in the step (a) is transferred into a second reaction vessel, mixed with phosgene, and subjected to a second reaction in the second reaction vessel at a temperature of 90-200 ℃ to obtain a second reaction product.
In some embodiments, the temperature in the second reaction vessel is maintained at 90-200 ℃ (e.g., 90-100 ℃, 90-110 ℃, 90-120 ℃, 90-130 ℃, 90-140 ℃, 90-150 ℃, 90-160 ℃, 90-170 ℃, 90-180 ℃, 90-190 ℃, 160 ℃.,. 150-. In certain embodiments, the temperature in the second reaction vessel is higher than the temperature in the first reaction vessel. For example, the temperature of the first reaction vessel is 0 to 90 ℃ and the temperature of the second reaction vessel is 90 to 170 ℃.
In certain embodiments, the second reaction product comprises carbamoyl chloride and hydrogen chloride, and in certain instances, the second reaction product further comprises one or more selected from the group consisting of: the unreacted amine and phosgene in step (a), and the unreacted intermediate carbamoylchloramine hydrochloride and phosgene in step (b).
Taking pentanediamine and phosgene as the starting reaction materials for example, the reaction mainly carried out in the second reaction vessel is as follows:
Figure BDA0003011563480000131
in certain embodiments, the phosgene in the second reaction vessel is also in stoichiometric excess. Thus, the off-gas of the second reaction vessel in step (b) comprises hydrogen chloride and phosgene, and in certain embodiments, the off-gas of the second reaction vessel has a hydrogen chloride content (w/w) of 60% or more (e.g., 65%, 70%, 75%, 80%, 85%) and a phosgene content (w/w) of 40% or less (e.g., 35%, 30%, 25%, 20%, 15%, 10%).
1.3Step (c)
In the step (c) of the present application, the second reaction product obtained in the step (b) is transferred into a third reaction vessel, mixed with phosgene, and subjected to a third reaction in the third reaction vessel at a temperature of 120-250 ℃ to obtain a third reaction product.
In certain embodiments, the temperature in the third reaction vessel is maintained between 120 ℃ and 250 ℃ (e.g., 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, or a range between any two of the above values). In certain embodiments, the temperature in the third reaction vessel is higher than the temperature in the second reaction vessel. For example, the temperature of the second reaction vessel is 90 to 170 ℃, and the temperature of the third reaction vessel is 170 to 180 ℃.
In certain embodiments, the third reaction product comprises isocyanate and hydrogen chloride, and in certain instances, the third reaction product further comprises one or more selected from the group consisting of: the unreacted amine and phosgene in step (a), the unreacted intermediate carbamoylchloramine hydrochloride in step (b), hydrogen chloride and phosgene, and the unreacted carbamoylchloride and phosgene in step (c).
Taking pentanediamine and phosgene as the starting reaction materials for example, the reaction carried out in the third reaction vessel includes, but is not limited to, the following reactions:
Figure BDA0003011563480000141
in certain embodiments, the phosgene in the third reaction vessel is also in stoichiometric excess. Thus, the off-gas of the third reaction vessel in step (c) comprises hydrogen chloride and phosgene, and in certain embodiments, the hydrogen chloride content of the off-gas of the third reaction vessel is 40% or more (e.g., 45%, 50%, 55%, 60%, 65%). In certain embodiments, the phosgene content of the off-gas of the third reaction vessel is 60% or less (e.g., 55%, 50%, 45%, 40%, 35%, 30%).
1.4Step (d)
In step (d) of the present application, transferring the third reaction product obtained in step (c) into a fourth reaction vessel, mixing with phosgene, and performing a fourth reaction in the fourth reaction vessel at a constant temperature of 120-300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate.
In certain embodiments, the temperature in the fourth reaction vessel is maintained at a constant temperature, such as a constant temperature between 120-300 ℃ (e.g., 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃) or a range between any two of the above values). In certain embodiments, the temperature in the fourth reaction vessel is equal to or higher than the temperature in the third reaction vessel. For example, the temperature of the third reaction vessel is 170 to 180 ℃, and the temperature of the fourth reaction vessel is 180 ℃.
In certain embodiments, the fourth reaction product comprises an isocyanate, and in certain instances, the fourth reaction product further comprises one or more selected from the group consisting of: hydrogen chloride, the incomplete amine and phosgene reaction in step (a), the incomplete intermediate carbamoylchloramine hydrochloride and phosgene reaction in step (b), the incomplete carbamoylchloride and phosgene reaction in step (c), and the incomplete phosgene reaction in step (d).
Taking pentanediamine and phosgene as the starting reaction materials for example, the reaction carried out in the fourth reaction vessel includes, but is not limited to, the following reactions:
Figure BDA0003011563480000151
in certain embodiments, the phosgene in the fourth reaction vessel is also in stoichiometric excess. In certain embodiments, the phosgene in the fourth reaction vessel is in sufficient excess to increase the yield of isocyanate and avoid the formation of by-products. Thus, the off-gas of the fourth reaction vessel in step (d) comprises hydrogen chloride and phosgene, and in certain embodiments the hydrogen chloride content (w/w) of the off-gas of the fourth reaction vessel is 5% or less (e.g., 5%, 4%, 3%, 2%, 1%). In certain embodiments, the phosgene content (w/w) in the off-gas of the fourth reaction vessel is 95% or greater (e.g., 95%, 96%, 97%, 98%, 99%).
In the present application, another advantage of the fourth reaction vessel is that many solid byproducts generated in the third reaction vessel cannot enter the fourth reaction vessel, so that compared with the third reaction vessel, the composition in the fourth reaction vessel is relatively pure (the main component is isocyanate), and even if a small amount of insoluble crystals (carbamoylchloramine hydrochloride) are dispersed in isocyanate, the insoluble crystals can be reacted to generate isocyanate by introducing a large amount of phosgene, so that the generation of byproducts is greatly reduced, and the yield of isocyanate is improved.
In certain embodiments, the method of producing an isocyanate described herein further comprises a step (e) of transferring the fourth reaction product obtained in step (d) to a purification unit for rectification to obtain a purified isocyanate. For the avoidance of doubt, step (e) is not a necessary step in the process for the preparation of the isocyanates described herein, and the purity of the isocyanate obtained in step (d) is already sufficiently high, for example to 90% or more.
In certain embodiments, each step in the process for the preparation of isocyanates as described herein is carried out under atmospheric conditions.
1.5Phosgene circulation sleeve
The inventors of the present application selected the optimum reaction conditions for producing isocyanate by splitting the isocyanate production process into four reaction stages (or optionally, five reaction stages, six reaction stages), respectively, thereby more finely adjusting the respective reaction conditions (including temperature, material flow rate, etc.).
As previously mentioned, in order to ensure the yield of isocyanate, a large excess of phosgene is often required to be invested in the isocyanate preparation process, thereby reducing the production of by-products. Therefore, another advantage of splitting the isocyanate preparation process into a plurality of reaction stages is that phosgene in the tail gas of each reaction vessel can be recycled, so that the purposes of recycling phosgene and reducing production cost are achieved.
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene described in step (b) is derived from an off-gas of the fourth reaction vessel described in step (d). In certain embodiments, all of the phosgene described in step (b) is derived from the off-gas of the fourth reaction vessel described in step (d). If the phosgene in the off-gas from the fourth reaction vessel described in step (d) is insufficient to react with the intermediate carbamoyl chloride amine hydrochloride to complete the conversion to carbamoyl chloride, additional fresh phosgene may be introduced to complete the second reaction.
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene described in step (c) is derived from an off-gas of the first reaction vessel described in step (a). In certain embodiments, all of the phosgene described in step (c) is derived from the off-gas of the first reaction vessel described in step (a). If the off-gas from the first reaction vessel in step (a) is deficient in phosgene, additional fresh phosgene may be introduced to complete the third reaction.
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene in step (b) is derived from the off-gas of the fourth reaction vessel in step (d), and at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a).
In certain embodiments, all of the phosgene in step (b) is derived from the off-gas of the fourth reaction vessel in step (d), and all of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a).
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene described in step (b) is derived from an off-gas of the third reaction vessel described in step (c). In certain embodiments, all of the phosgene described in step (b) is derived from the off-gas of the third reaction vessel described in step (c). If the off-gas from the third reaction vessel in step (c) is deficient in phosgene, additional fresh phosgene may be introduced to complete the second reaction.
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene described in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d). In certain embodiments, all of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d). If the off-gas from the first reaction vessel in step (a) and the off-gas from the fourth reaction vessel in step (d) are deficient in phosgene, additional phosgene may be introduced to complete the third reaction.
In certain embodiments, at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and at least a portion (e.g., at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%) of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
In certain embodiments, all of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and all of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and the off-gas of the fourth reaction vessel in step (d).
The preparation method of the isocyanate can realize the recycling of phosgene, and compared with the traditional method, the use amount of phosgene can be reduced by 30-70%, so that the production cost is greatly reduced, and the pollution of tail gas to the environment is also obviously reduced.
2.System for preparing isocyanate
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof.
Fig. 1 shows a schematic block diagram of a system for preparing isocyanate according to one embodiment of the present application, and fig. 2 shows a schematic block diagram of a system for preparing isocyanate according to another embodiment of the present application. The difference between fig. 1 and fig. 2 is the different way of applying the off-gas to the individual reaction vessels. The features common to fig. 1 and 2 are described below using fig. 1 as an example.
As shown in fig. 1, the system includes: the device comprises a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel and a temperature control device. The first reaction container, the second reaction container, the third reaction container and the fourth reaction container respectively comprise a feed inlet, a tail gas discharge outlet, a vent and a sampling port. The temperature control device is configured to control the temperature in the first reaction vessel, the second reaction vessel, the third reaction vessel and the fourth reaction vessel to prepare the isocyanate.
In certain embodiments, the feed inlets of the first reaction vessel may be further divided into solvent feed inlets, phosgene feed inlets, reactant amine feed inlets, and the like, depending on the type of feed. In certain embodiments, the feed inlets of the second, third, and fourth reaction vessels may be further divided into phosgene feed inlets, and the like, depending on the type of feed. It is anticipated that the number of the feed inlet, the exhaust gas outlet, the discharge outlet, the vent port, and the sampling port in the embodiment shown in fig. 1 is not limited to one, and a plurality of feed inlets, exhaust gas outlets, discharge outlets, vent ports, and sampling ports may be provided as necessary. In the present application, the inlet, the exhaust gas outlet, the vent, and the sampling port are functionally defined openings, but one or more of the inlet, the exhaust gas outlet, the vent, and the sampling port may be physically multiplexed by providing corresponding switching devices to reduce the number of openings, for example, the same opening provided on the first, second, third, or fourth reaction vessel may be used to operatively input reactants into the reaction vessel or discharge reactants from the reaction vessel.
The first reaction vessel, the second reaction vessel, the third reaction vessel and the fourth reaction vessel are respectively used for carrying out reactions in various stages for preparing isocyanate. For this purpose, the outlet openings provided on the individual reaction vessels are selectively connected to one another. For example, the discharge port of the first reaction vessel is selectively communicated with the discharge port of the second reaction vessel, the discharge port of the second reaction vessel is selectively communicated with the discharge port of the third reaction vessel, and the discharge port of the third reaction vessel is selectively communicated with the discharge port of the fourth reaction vessel. In certain embodiments, the discharge port of each reaction vessel is located at a lower portion of the corresponding reaction vessel. In an emergency situation, for example, when the pressure in the reaction vessel rises sharply or the liquid boils sharply to reach a certain threshold value, part of gas can be discharged or transferred to the emergency discharging device by communicating the air vent of the reaction vessel with the emergency discharging device, and/or part of liquid can be discharged or transferred to the emergency discharging device by selectively communicating the discharge port of the reaction vessel with the emergency discharging device, so that the damage of the reaction vessel is prevented, and the safety of the whole system is improved. Taking the first reaction vessel as an example, the selective communication between the vent of the first reaction vessel and the emergency discharge device may be achieved, for example, by providing a pressure relief valve on the line connecting the vent of the first reaction vessel and the emergency discharge device. Selective communication between the outlet of the first reaction vessel and the emergency discharge device can also be achieved, for example, by providing a pressure relief valve on the line connecting the outlet of the first reaction vessel and the emergency discharge device. The outlets of the individual reaction vessels are selectively in communication with each other, for example by switching valves, for controllably transferring material.
As described above, the temperature span of the reaction conditions in each stage of the phosgene liquid phase method for producing isocyanates is large, and it is difficult to conduct a reaction test in a large temperature range in the same reaction vessel. In order to reduce the difficulty of temperature control of the reaction vessels, the four reaction vessels of the present invention perform the reaction in stages in which the temperature setting ranges of each reaction vessel are different from each other.
For example, in one embodiment, the phosgene liquid phase process for preparing isocyanates is carried out in four stages. Correspondingly, the temperature regulation range of the first reaction vessel is-30-90 ℃, the temperature regulation range of the second reaction vessel is 90-200 ℃, the temperature regulation range of the third reaction vessel is 120-250 ℃, and the temperature regulation range of the fourth reaction vessel is 120-300 ℃. The first stage of the reaction utilizes the reaction of an amine with phosgene to form a carbamateA suspension of an acid chloride and an intermediate carbamoylchloramine hydrochloride, conducted in a first reaction vessel. Solvent, phosgene and amine were first fed into the first reaction vessel through the feed ports (i.e., solvent feed port, phosgene feed port, reactant amine feed port). Then gradually raising the temperature T of the first reaction vessel by a temperature control device11-1(-30℃≤T11-1At a temperature of not more than 90 ℃, for example, gradually raising the temperature and maintaining the temperature at 0 to 90 ℃. Then the first reaction product in the first reaction container is input into the second reaction container through the discharge hole of the first reaction container so as to carry out the second stage reaction. In the second stage of the reaction, the suspension obtained from the first stage of the reaction is reacted to give carbamoyl chloride. The temperature T of the second reaction vessel is gradually increased by the temperature control means similarly to the operation of the first reaction vessel11-2(90℃≤T11-2At ≦ 200 deg.C, e.g. gradually increasing from 90 deg.C to 170 deg.C), in order to allow complete reaction of the intermediate carbamoyl chloride amine hydrochloride in the suspension resulting from the first stage reaction to carbamoyl chloride. Then the second reaction product in the second reaction container is input into a third reaction container through a discharge hole of the second reaction container so as to carry out the reaction of the third stage. In the third stage of the reaction, the carbamoyl chloride in the second reaction product is allowed to react to form isocyanate and hydrogen chloride. The temperature T of the third reaction vessel is gradually increased by the temperature control means similarly to the operation of the first reaction vessel11-3(120℃≤T 11-2250 ℃ C., for example, gradually from 170 ℃ to 180 ℃ C.). Then the third reaction product in the third reaction vessel is input into a fourth reaction vessel through a discharge hole of the third reaction vessel so as to carry out the reaction of a fourth stage. In the fourth stage of the reaction, the carbamoyl chloride in the third reaction product is allowed to react completely to form an isocyanate. Adjusting the temperature of the fourth reaction vessel to T by a temperature control device11-4(120℃≤T11-2At 300 ℃ or lower, for example 180 ℃ and maintaining the temperature constant. In certain embodiments, T11-1≤T11-2≤T11-3≤T11-4。
In some embodiments, the temperature control ranges of the first, second, third and fourth reaction vessels may partially overlap each other, for example, the temperature control range of the first reaction vessel is-30 to 90 deg.C, the temperature control range of the second reaction vessel is 80 to 180 deg.C, the temperature control range of the third reaction vessel is 160 to 190 deg.C, and the temperature control range of the fourth reaction vessel is 170 to 300 deg.C. By making the temperature at which the first reaction product is discharged from the first reaction vessel the same as the initial temperature of the second reaction vessel, the first reaction product discharged from the first reaction vessel can be continuously reacted while being transferred into the second reaction vessel. Similarly, by making the temperature at which the second reaction product is discharged from the second reaction vessel the same as the initial temperature of the third reaction vessel, the second reaction product discharged from the second reaction vessel can be continuously reacted while being transferred into the third reaction vessel; by making the temperature at which the third reaction product is discharged from the third reaction vessel the same as the initial temperature of the fourth reaction vessel, the third reaction product discharged from the third reaction vessel can be continuously reacted while being transferred into the fourth reaction vessel.
In fig. 1, the off-gas vent of the first reaction vessel is in selective communication with the third reaction vessel and the off-gas vent of the fourth reaction vessel is in selective communication with the vent of the second reaction vessel. Although the connection port through which the off-gas vent of the first reaction vessel communicates with the third reaction vessel is not the feed port of the third reaction vessel in fig. 1 (e.g., the connection port is another opening in the third reaction vessel than the feed port), it is understood that the off-gas vent of the first reaction vessel may (and preferably does) selectively communicate with the feed port of the third reaction vessel. Similarly, although in fig. 1 the connection port through which the off-gas vent of the fourth reaction vessel communicates with the second reaction vessel is not the feed port of the second reaction vessel (e.g., the connection port is another opening in the second reaction vessel than the feed port), it is understood that the off-gas vent of the fourth reaction vessel may (and preferably does) selectively communicate with the feed port of the second reaction vessel.
In fig. 2, the off-gas vent of the first reaction vessel, the off-gas vent of the fourth reaction vessel are each in selective communication with the third reaction vessel, and the off-gas vent of the third reaction vessel is in selective communication with the second reaction vessel. Although the connection ports through which the off-gas discharge ports of the first and fourth reaction vessels communicate with the third reaction vessel are not the feed ports of the third reaction vessel in fig. 2 (e.g., the connection ports are other openings in the third reaction vessel than the feed ports), it is understood that the off-gas discharge ports of the first and fourth reaction vessels may (and preferably do) selectively communicate with the feed ports of the third reaction vessel. Similarly, although in fig. 2 the connection port through which the off-gas vent of the third reaction vessel communicates with the second reaction vessel is not the feed port of the second reaction vessel (e.g., the connection port is another opening in the second reaction vessel than the feed port), it will be appreciated that the off-gas vent of the fourth reaction vessel may (and preferably does) selectively communicate with the feed port of the second reaction vessel.
Fig. 3 shows a schematic block diagram of a system 10 for preparing isocyanates according to one embodiment of the present application, and fig. 4 shows a schematic block diagram of a system 20 for preparing isocyanates according to another embodiment of the present application. System 10 differs from system 20 in the manner in which the off-gas is applied to each reactor vessel. Features common to both system 10 and system 20 are described below with respect to system 10.
As shown in fig. 3, the system 10 includes a first reaction vessel 100, a second reaction vessel 200, a third reaction vessel 300, a fourth reaction vessel 400, and a temperature control device 500. Wherein the first, second, third and fourth reaction vessels 100, 200, 300 and 400 respectively receive reactants of respective reaction stages and allow the reactants of the respective stages to react under specific conditions. Although the system 10 in fig. 3 includes four reaction vessels, the present invention is not limited to four reaction vessels, for example, the second reaction vessel 200 may include more than 2 (e.g., 2, 3, 4, 5 or more) reaction vessels, and the third reaction vessel 300 may include more than 2 (e.g., 2, 3, 4, 5 or more) reaction vessels. Without being bound by any theory, it is believed that the amount of phosgene used can be further reduced as the number of reaction vessels increases and the number of stages of tail gas application increases.
In some embodiments, the first, second, third and fourth reaction vessels 100, 200, 300, 400 are configured to be substantially cylindrical. In other embodiments, the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 may be configured in any other shape suitable for performing a reaction, such as a sphere, a hemisphere, a truncated cone, and the like. The structures of any two of the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 may be the same or different. Hereinafter, the "reaction vessel" may refer to the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and/or the fourth reaction vessel 400.
As shown in fig. 3, the first reaction vessel 100 includes: solvent feed ports 111a,111b, off- gas vent ports 111c,111d, phosgene feed ports 112a,112b, reactant amine feed port 113. The solvent, phosgene, and amine used in the phosgene liquid phase method for preparing isocyanate may be fed into the first reaction vessel 100 through the corresponding solvent feed ports 111a,111b, phosgene feed ports 112a,112b, and reactant amine feed port 113, respectively. The offgas of the first reaction vessel 100 may be discharged out of the first reaction vessel 100 through offgas discharge ports 111c and 111 d. The first reaction vessel 100 further includes a discharge port 120, a vent port 140, and a sampling port 150.
The second reaction vessel 200 includes: and the tail gas discharge ports 211a and 211b and the phosgene feed ports 212a and 212b are respectively used for discharging tail gas of the second reaction vessel 200 and supplementing phosgene to the second reaction vessel 200 according to reaction requirements. The second reaction vessel 200 further includes: a discharge port 220, a vent 240, and a sampling port 250.
The third reaction vessel 300 includes: and the tail gas discharge ports 311a and 311b and the phosgene feed ports 312a and 312b are respectively used for discharging tail gas of the third reaction vessel 300 and supplementing phosgene to the third reaction vessel 300 according to reaction requirements. The third reaction vessel 300 further includes: discharge port 320, vent port 340, and sampling port 350.
The fourth reaction vessel 400 includes: and the tail gas discharge ports 411a and 411b and the phosgene feed ports 412a and 412b are respectively used for discharging tail gas of the fourth reaction vessel 400 and supplementing phosgene to the fourth reaction vessel 400 according to reaction requirements. The fourth reaction vessel 400 further includes: discharge port 420, vent port 440, and sampling port 450.
Vents 140, 240, 340, 440, respectively, optionally communicate with an emergency discharge device through a switching valve to allow gas to enter or exit the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, or the fourth reaction vessel 400. The operator may operate the corresponding switching valve to extract a certain amount of reaction samples from the first, second, third or fourth reaction vessels 100, 200, 300 or 400 through the sampling ports 150, 250, 350, 450 for checking the composition of the reaction product, thereby determining the reaction rate.
The discharge port 120 of the first reaction vessel 100 and the discharge port 220 of the second reaction vessel 200 are selectively communicated, and the vent 140 of the first reaction vessel 100 is selectively communicated with an emergency discharging device. Similarly, the discharge port 220 of the second reaction vessel 200 and the discharge port 320 of the third reaction vessel 300 are selectively communicated, and the vent 240 of the second reaction vessel 200 is selectively communicated with the emergency discharging device. Similarly, the outlet 320 of the third reaction vessel 300 and the outlet 420 of the fourth reaction vessel 400 are selectively communicated, and the vent 340 of the third reaction vessel 300 is selectively communicated with an emergency discharging device. Similarly, the vent 440 of the fourth reaction vessel 400 is in selective communication with an emergency discharge device.
In certain embodiments, the discharge port 120 of the first reaction vessel is also in selective communication with an emergency discharge device. In certain embodiments, the discharge outlet 220 of the second reaction vessel is also in selective communication with an emergency discharge device. In certain embodiments, the discharge port 320 of the third reaction vessel is also in selective communication with an emergency discharge device. In certain embodiments, the discharge outlet 420 of the fourth reaction vessel is also in selective communication with an emergency discharge device. The discharge port of each reaction vessel is in selective communication with an emergency discharge device so that a portion of the liquid may be vented or diverted to the emergency discharge device.
The above-mentioned alternative communication may be achieved, for example, by manually operating a switching valve, or automatically by a safety valve which may be arranged to open automatically to vent pressure from one reaction vessel to another when the pressure on one side of the valve exceeds a threshold value.
In the present application, each reaction vessel may use a different emergency discharge device, or may share a common emergency discharge device. The vent and the discharge opening can be connected to the same emergency discharge device or to different emergency discharge devices for each reaction vessel.
In the embodiment shown in fig. 3, the solvent feed ports 111a,111b and the off- gas discharge ports 111c,111d are disposed at the top of the first reaction vessel 100, but in some embodiments, the solvent feed ports 111a,111b and the off- gas discharge ports 111c,111d may be disposed at other positions, such as the side wall of the reaction vessel. Although the phosgene feed port 112b and the reactant amine feed port 113 of the illustrated embodiment are disposed at the lower portion of the sidewall of the first reaction vessel 100, the phosgene feed port 112a is disposed at the bottom of the first reaction vessel 100, the phosgene feed port 212b is disposed at the lower portion of the sidewall of the second reaction vessel 200, the phosgene feed port 212a is disposed at the bottom of the second reaction vessel 200, the phosgene feed port 312b is disposed at the lower portion of the sidewall of the third reaction vessel 300, the phosgene feed port 312a is disposed at the bottom of the third reaction vessel 300, the phosgene feed port 412b is disposed at the lower portion of the sidewall of the fourth reaction vessel 400, and the phosgene feed port 412a is disposed at the bottom. However, in some embodiments, the phosgene feed ports 112a,112b, the reactant amine feed port 113, the phosgene feed ports 212a,212b, the phosgene feed ports 312a,312b, and the phosgene feed ports 412a,412b may be located elsewhere.
Further, although in the example shown in fig. 3, the solvent feed port 111a and the off-gas discharge port 111c of the first reaction vessel 100 share the same opening provided in the first reaction vessel 100, and the solvent feed port 111b and the off-gas discharge port 111d share the same opening provided in the first reaction vessel 100, in some embodiments, the solvent feed port 111a and the off-gas discharge port 111c may be openings provided in the first reaction vessel 100, respectively, and the solvent feed port 111b and the off-gas discharge port 111d may also be openings provided in the first reaction vessel 100, respectively.
In addition, although in the embodiment shown in fig. 3, the discharge port 120, the phosgene feed port 112a, and the sampling port 150 of the first reaction vessel 100 share the same opening provided in the first reaction vessel 100, the discharge port 220, the phosgene feed port 212a, and the sampling port 250 of the second reaction vessel 200 share the same opening provided in the second reaction vessel 200, the discharge port 320, the phosgene feed port 312a, and the sampling port 350 of the third reaction vessel 300 share the same opening provided in the third reaction vessel 300, and the discharge port 420, the phosgene feed port 412a, and the sampling port 450 of the fourth reaction vessel 400 share the same opening provided in the fourth reaction vessel 400. However, in some embodiments, the outlet 120 and the sampling port 150 may be openings respectively disposed on the first reaction vessel 100, the outlet 220 and the sampling port 250 may be openings respectively disposed on the second reaction vessel 200, the outlet 320 and the sampling port 350 may be openings respectively disposed on the third reaction vessel 300, and the outlet 420 and the sampling port 450 may be openings respectively disposed on the fourth reaction vessel 400. Conversely, the openings shown in fig. 3 as being provided on the reaction vessels, respectively, may in other embodiments be provided sharing the same opening on the reaction vessels. For example, in certain embodiments, the reactant amine feed port 113 and the feed port 120 share the same opening disposed on the first reaction vessel 100. Hereinafter, "opening" may refer to one or more of the solvent feed port 111a,111b, the off- gas discharge port 111c,111d, the phosgene feed port 112a,112b, the reactant amine feed port 113, the discharge port 120, the vent port 140, the sampling port 150, the off- gas discharge ports 211a,211b, the phosgene feed ports 212a,212b, the discharge port 220, the vent port 240, the sampling port 250, the off- gas discharge ports 311a,311b, the phosgene feed port 312a,312b, the discharge port 320, the vent port 340, the sampling port 350, the off- gas discharge ports 411a,411b, the phosgene feed ports 412a,412b, the discharge port 420, the vent port 440, and the sampling port 450.
In some embodiments, each opening is provided with an opening-closing member for opening and closing the corresponding opening, the opening-closing member being movable between an open position and a closed position. In the open position, the opening is open, allowing reactants, reaction products to enter and exit the reaction vessel; in the closed position, the opening is closed, thereby ensuring the closure of the reaction vessel during the reaction and preventing leakage of reactants and/or reaction products from the reaction vessel. The opening-closing member may be configured as a shutter, a valve, or other similar structures.
With continued reference to fig. 3, the first reaction vessel 100 includes two solvent feed ports 111a,111b disposed on the first reaction vessel 100, wherein a first precooler 710 is connected upstream of the solvent feed port 111 b. The second reaction vessel 200 includes two off- gas discharge ports 211a,211b, and a second precooler 720 is connected upstream of the off-gas discharge port 211 b. The third reaction vessel 300 comprises two off- gas discharge ports 311a,311b, and a third precooler 730 is connected upstream of the off-gas discharge port 311 b. The fourth reaction vessel 400 includes two off- gas discharge ports 411a,411b, and a fourth precooler 740 is connected upstream of the off-gas discharge port 411 b.
In certain embodiments, the first precooler 710 is used to regulate the temperature of the solvent or tail gas flowing therethrough, and the second precooler 720, the third precooler 730, and the fourth precooler 740 are used to regulate the temperature of the tail gas flowing therethrough. The precoolers can be independently selected from a shell-and-tube precooler, a circulating heat exchange precooler, a refrigeration circulator, a screw water chilling unit, a gas condensation system and the like, for example, from a precooler of Wuxi Guanya constant temperature refrigeration technology company Limited. In some embodiments, only the first precooler 710 may be provided. In other embodiments, only a second precooler 720 may be provided. In other embodiments, only a third precooler 730 may be provided. In other embodiments, only the fourth precooler 740 may be provided.
In the embodiment shown in fig. 3, the solvent may optionally enter the first reaction vessel 100 through the first precooler 710 via the solvent feed port 111a or 111 b. When the solvent does not need to be pre-cooled or the first pre-cooler 710 does not need to be flushed, the solvent is directly introduced into the first reaction vessel 100 through the solvent feed port 111a by controlling the opening and closing of the valve. When the solvent needs to be precooled or the residual reactants in the first precooler 710 need to be flushed back to the first reaction vessel 100, the solvent enters the first reaction vessel 100 through the first precooler 710 and the solvent feed port 111b in sequence by controlling the opening and closing of the valve.
In the embodiment shown in fig. 3, the off-gas of the first reaction vessel 100 is optionally discharged from the first reaction vessel 100 through the first precooler 710 via the off- gas discharge port 111c or 111 d. When the pre-cooling of the tail gas is not required or the flushing of the first pre-cooler 710 is not required, the tail gas is directly discharged out of the first reaction vessel 100 through the tail gas discharge port 111c by controlling the opening and closing of the valve. When the off-gas needs to be pre-cooled or the residual reactant in the first pre-cooler 710 needs to be flushed back into the first reaction vessel 100, the off-gas is discharged out of the first reaction vessel 100 through the off-gas discharge port 111d and the first pre-cooler 710 by controlling the opening and closing of the valve.
Similarly, the off-gas of the second reaction vessel 200 may also be optionally discharged out of the second reaction vessel 200 directly through the off- gas discharge port 211a or 211b, or out of the second reaction vessel 200 sequentially through the off-gas discharge port 211b and the second precooler 720. Similarly, the off-gas of the third reaction vessel 300 may also be optionally discharged out of the third reaction vessel 300 directly through the off- gas discharge port 311a or 311b, or out of the third reaction vessel 300 through the off-gas discharge port 311b and the third precooler 730 in sequence. Similarly, the off-gas of the fourth reaction vessel 400 may also be optionally discharged out of the fourth reaction vessel 400 directly through the off- gas discharge port 411a or 411b, or sequentially through the off-gas discharge port 411b and the fourth precooler 740.
By selectively precooling the solvent entering the first reaction vessel and the tail gas discharged from the first, second, third or fourth reaction vessels, the temperature of the solvent or the tail gas can be better adjusted, the reaction is accelerated or the influence of the added solvent, the discharged tail gas and the tail gas to be recycled on the ongoing chemical reaction is avoided.
Alternatively or additionally, during the reaction in the first reaction vessel 100, the phosgene feed openings 112a,112b are opened and the valve upstream of the first precooler 710 is closed, so that the gas mixture overflowing from the first reaction vessel 100 flows through the first precooler 710 for external circulation, and after condensation, is returned to the first reaction vessel 100 again through the solvent feed opening 111a or 111 b. Similarly, during the reaction in the second reaction vessel 200, the phosgene feed ports 212a,212b are opened and the valve upstream of the second precooler 720 is closed, so that the gas mixture overflowing from the second reaction vessel 200 is circulated through the second precooler 720 for external circulation. Similarly, during the reaction in the third reaction vessel 300, the phosgene feed ports 312a,312b are opened and the valve upstream of the third precooler 730 is closed, so that the gas mixture overflowing from the third reaction vessel 300 is externally circulated through the third precooler 730. Similarly, during the reaction in the fourth reaction vessel 400, the phosgene feed ports 412a,412b are opened and the valve upstream of the fourth precooler 740 is closed, so that the gas mixture overflowing from the fourth reaction vessel 400 is circulated through the fourth precooler 740 for external circulation. In this way, the gas mixture generated in the reaction vessel can be condensed and refluxed into the reaction vessel, so that the utilization of reactants is more sufficient, and the generation of byproducts and waste gas can be reduced.
In the embodiment shown in fig. 3, the first reaction vessel 100 is provided with two solvent feed ports 111a and 111 b. In other embodiments, however, a single solvent feed port may be provided in the first reaction vessel 100, and a precooler may optionally be connected or not connected upstream of the single opening, as desired. Similarly, in the embodiment shown in fig. 3, two off-gas discharge ports are provided on each of the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300 and the fourth reaction vessel 400. In other embodiments, however, a single off-gas vent may be provided in the first, second, third and/or fourth reaction vessels 100, 200, 300, 400, and optionally a precooler may or may not be connected upstream of the single vent, as desired.
In fig. 3, the first reaction vessel 100 comprises two phosgene inlet openings 112a,112b arranged on the first reaction vessel 100, wherein a first temperature controller 910 is connected upstream of the phosgene inlet opening 112b, and the phosgene inlet opening 112a and the outlet opening 120 are multiplexed into the same opening. The second reaction vessel 200 comprises two phosgene feed openings 212a,212b, upstream of which a second temperature controller 920 is connected, the phosgene feed opening 212a and the outlet opening 220 being multiplexed with one another. The third reaction vessel 300 comprises two phosgene feed inlets 312a,312b, a third temperature controller 930 is connected upstream of the phosgene feed inlet 312b, and the phosgene feed inlet 312a and the discharge outlet 320 are multiplexed into the same opening. The fourth reaction vessel 400 comprises two phosgene feed openings 412a,412b, a fourth temperature controller 940 being connected upstream of the phosgene feed opening 412b, the phosgene feed opening 412a and the outlet opening 420 being multiplexed with one another.
In certain embodiments, the first, second, third, and fourth thermostats 910, 920, 930, and 940 are used to regulate the temperature of the phosgene flowing therethrough, and the first, second, third, and fourth thermostats 910, 920, 930, and 940 may be selected from shell and tube heat exchangers, recycle heat exchangers, and the like. In some embodiments, only the first thermostat 910 may be provided. In other embodiments, only the second thermostat 920 may be provided. In still other embodiments, only the third thermostat 930 may be provided. In other embodiments, only the fourth thermostat 940 may be provided.
In the embodiment shown in FIG. 3, phosgene optionally enters the first reaction vessel 100 through a first attemperator 910 via phosgene feed inlet 112 b. When the pre-temperature adjustment of phosgene is not required, phosgene is directly fed into the first reaction vessel 100 through the phosgene feed opening 112a by controlling the opening and closing of the valve. When the temperature of the phosgene needs to be pre-regulated, the phosgene enters the first reaction vessel 100 through the first temperature regulator 910 and the phosgene inlet 112b in sequence by controlling the opening and closing of the valve. Similarly, phosgene can alternatively be fed directly into the second reaction vessel 200 via phosgene feed 212a or into the second reaction vessel 200 via the second temperature controller 920 and phosgene feed 212b in this order. Similarly, phosgene can alternatively be fed directly into the third reaction vessel 300 via the phosgene feed 312a or into the third reaction vessel 300 via the third temperature controller 930 and the phosgene feed 312b in this order. Similarly, phosgene can alternatively be fed directly into the fourth reaction vessel 400 via phosgene feed 412a or into the fourth reaction vessel 400 via the fourth attemperator 940 and phosgene feed 412b in sequence.
By selectively pre-conditioning the phosgene, the phosgene temperature can be better adjusted, the effect of phosgene addition on the ongoing chemical reaction is reduced during the ongoing reaction, and the state of the phosgene (liquid, gas, boiling) in the reaction vessel is better controlled.
In the embodiment shown in fig. 3, the reactant in the first reaction vessel 100 optionally enters the first temperature regulator 910 through the phosgene feed port 112a during the reaction, and enters the first reaction vessel 100 through the phosgene feed port 112b again after temperature regulation, so that the reactant in the reaction continuously circulates outside through the first temperature regulator 910, thereby increasing the mixing contact time of the reactant phosgene and improving the phosgene utilization rate. Similarly, the reactant in the second reaction vessel 200 can be selectively fed into the second temperature regulator 920 through the phosgene feed inlet 212a and then fed into the second reaction vessel 200 through the phosgene feed inlet 212b, and the mixing contact time of the reactant and phosgene is increased through external circulation, so that the phosgene utilization rate is improved. Similarly, the reactants in the third reaction vessel 300 can be selectively fed into the third temperature regulator 930 through the phosgene feed inlet 312a and then fed into the third reaction vessel 300 through the phosgene feed inlet 312b, and the mixing contact time of the reactants and the phosgene is increased through external circulation, so that the phosgene utilization rate is improved. Similarly, the reactant in the fourth reaction vessel 400 can optionally enter the fourth temperature regulator 940 through the phosgene feed inlet 412a and then enter the fourth reaction vessel 400 through the phosgene feed inlet 412b, and the mixing contact time of the reactant and the phosgene is increased through external circulation, so that the phosgene utilization rate is improved.
In the embodiment shown in fig. 3, the first attemperator 910 is configured as a heat exchanger type precooler that exchanges heat by circulation of the ethylene glycol aqueous solution; the second, third and/or fourth thermostats 920, 930 and 940 are configured as heat exchanger type preheaters which exchange heat through the circulation of the conduction oil. In other embodiments, the first thermostat 910, the second thermostat 920, the third thermostat 930, and the fourth thermostat 940 may be selected from: electric heaters, refrigerators, heat exchangers (e.g., coil heat exchangers, plate heat exchangers, ring and groove heat exchangers, finned tube heat exchangers, plate and shell heat exchangers, double-tube heat exchangers, shell and tube heat exchangers, split-tube heat exchangers, disc heat exchangers, candle heat exchangers, spiral heat exchangers, block heat exchangers, screw heat exchangers, and spiral heat exchangers).
As shown in fig. 3, the temperature control device 500 is used for adjusting the temperature of the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300 and the fourth reaction vessel 400 to a predetermined value, for example, the temperature of the first reaction vessel 100 is adjusted to-30 to 90 ℃, the temperature of the second reaction vessel 200 is adjusted to 90 to 200 ℃, the temperature of the third reaction vessel 300 is adjusted to 120 to 250 ℃ and the temperature of the fourth reaction vessel 400 is adjusted to 120 to 300 ℃. In a preferred embodiment, the temperature of the first reaction vessel 100 is adjusted to be in a range of 0 to 90 ℃, the temperature of the second reaction vessel 200 is adjusted to be in a range of 90 to 170 ℃, the temperature of the third reaction vessel 300 is adjusted to be in a range of 170 to 180 ℃, and the temperature of the fourth reaction vessel 400 is adjusted to be in a range of 180 to 250 ℃.
The temperature control device 500 includes a temperature sensor (not shown), heat exchanging devices 510,520,530,540, and a temperature controller (not shown). In certain embodiments, the temperature sensor is a contact temperature sensor, which may be disposed inside the first reaction vessel 100 and/or attached to a sidewall of the first reaction vessel 100, disposed inside the second reaction vessel 200 and/or attached to a sidewall of the second reaction vessel 200, disposed inside the third reaction vessel 300 and/or attached to a sidewall of the third reaction vessel 300, or disposed inside the fourth reaction vessel 400 and/or attached to a sidewall of the fourth reaction vessel 400. The contact temperature sensor is any sensor suitable for detecting a temperature within the above-mentioned temperature range, such as a thermocouple, a thermistor, a thermometer.
In some embodiments, a plurality of contact temperature sensors (e.g., 1, 2, 3, 4, etc.) may be provided, and these sensors may be provided at different locations of the reaction vessel to more fully and accurately obtain the temperature value of the reaction vessel. In the case where a plurality of temperature sensors are provided, the temperature value of the corresponding reaction vessel can be determined by weighted averaging the measurement values of the respective contact temperature sensors.
In certain embodiments, the temperature sensor is a non-contact temperature sensor. The non-contact temperature sensor is disposed outside the first, second, third and/or fourth reaction vessels 100, 200, 300 and/or 400 and separated from the first, second, third and/or fourth reaction vessels 100, 200, 300 and 400 by a certain distance. The non-contact temperature sensor may be configured as an infrared temperature sensor, a radiation thermometric meter, or the like. The temperature sensor may be a commercially available product, such as a temperature sensor selected from the group consisting of Fuluke, Keynes, and omega.
In some embodiments, a plurality of non-contact temperature sensors (e.g., 1, 2, 3, 4, etc.) may be provided, and these sensors may be disposed at different locations outside the reaction vessel to more fully and accurately obtain the temperature value of the reaction vessel. In the case where a plurality of temperature sensors are provided, the temperature value of the corresponding reaction vessel can be determined by weighted averaging the measurement values of the respective contact temperature sensors.
In the embodiment shown in fig. 3, heat exchange devices 510,520,530,540 are jacketed circulation heat exchangers, wherein heat exchange device 510 is attached to a side wall of first reaction vessel 100, heat exchange device 520 is attached to a side wall of second reaction vessel 200, heat exchange device 530 is attached to a side wall of third reaction vessel 300, and heat exchange device 540 is attached to a side wall of fourth reaction vessel 400 for heat exchange with reactants in the first, second, third and fourth reaction vessels 100, 200, 300 and 400, respectively. The temperature ranges regulated by heat exchange device 510, heat exchange device 520, heat exchange device 530, and heat exchange device 540 are different from each other. For example, the adjustable temperature range of the heat exchange device 510 is-30-90 ℃, the adjustable temperature range of the heat exchange device 520 is 90-200 ℃, the adjustable temperature range of the heat exchange device 530 is 120-250 ℃, and the adjustable temperature range of the heat exchange device 540 is 120-300 ℃. One skilled in the art can set the four temperature ranges to partially overlap or not overlap each other as desired.
Alternatively, the heat exchange devices 510,520,530,540 may be configured as one of other types of heat exchange devices, such as an electrical heating tube, a circulating heat exchange device (e.g., a tube heat exchanger, a plate heat exchanger, a ring and groove heat exchanger, a finned tube heat exchanger, a plate and shell heat exchanger, a double tube heat exchanger, a shell and tube heat exchanger, a split tube heat exchanger, a disc heat exchanger, a candle heat exchanger, a spiral heat exchanger, a block heat exchanger, a screw heat exchanger, and a spiral heat exchanger), or a combination thereof. In certain embodiments, heat exchange devices 510,520,530,540 are configured as a cyclic heat exchanger, wherein heat exchange device 510 selects an aqueous glycol solution as the heat-exchange liquid and heat exchange devices 520,530, and 540 select a thermally conductive oil as the heat-exchange liquid.
Temperature controllers (not shown) are coupled to the temperature sensors and the heat exchange devices 510,520,530, and 540, respectively, and the temperature controllers are configured to receive measurement signals of the temperature sensors and operate the heat exchange devices 510,520,530, and 540 according to the measurement signals. The operation of the temperature controller will be described below by taking the first reaction vessel 100 as an example. The temperature controller receives a detection signal indicating the temperature in the first reaction vessel 100 from the temperature sensor, determines the current temperature in the first reaction vessel 100, and then compares a preset temperature value with the current temperature value. If the comparison result shows that the current temperature is lower than the preset temperature value, the temperature controller correspondingly controls the heat exchange device to heat the reaction container, for example, the electric heating tube is started or the power of the electric heating tube is increased, the temperature and the flow speed of the heat exchange liquid in the circulating heat exchange device are increased, and the temperature of the reaction container is increased to a preset value. If the comparison result shows that the current temperature is higher than the preset temperature value, the temperature controller correspondingly controls the heat exchange device to cool the reaction container, for example, the electric heating tube is closed or the power of the electric heating tube is reduced, and the temperature and the flow rate of heat exchange liquid in the circulating heat exchange device are reduced. The temperature controller can be configured into various controllers capable of automatic control. In some embodiments, the temperature controller is a Proportional Integral Derivative (PID) controller.
The materials of the first, second, third and fourth reaction vessels 100, 200, 300 and 400 according to the present application may be any suitable materials. In certain embodiments, the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 are glass vessels, which are suitable for use in smaller laboratory scale situations.
In other embodiments, the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 are reaction vessels. Compared with a glass container, the reaction kettle has the advantages that a matched temperature control device of the reaction kettle is more mature industrially, and experimental production can be conveniently transferred after reaction conditions are determined. In certain embodiments, the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 are selected from the group consisting of: carbon steel reation kettle, stainless steel reation kettle, enamel reactor, steel lining reation kettle.
In some embodiments, when the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300 and the fourth reaction vessel 400 are reaction vessels, the observation hole 160 may be further formed on a sidewall of the first reaction vessel 100, the observation hole 260 may be formed on a sidewall of the second reaction vessel 200, the observation hole 360 may be formed on a sidewall of the third reaction vessel 300, and the observation hole 460 may be formed on a sidewall of the fourth reaction vessel 400. Through the observation holes 160, 260, 360 and 460, the states of the insides of the first, second, third and fourth reaction vessels 100, 200, 300 and 400 can be visually observed to determine whether the liquid in the reaction vessels is boiled.
The reaction process of preparing isocyanate by the phosgene liquid phase method can generate slurry of carbamoyl chloride and hydrochloride of amine, the state of the slurry is viscous, good stirring is needed to prevent the generation of byproducts, the reactants are contacted more fully, and the reaction efficiency is improved. As shown in fig. 3, stirring assemblies 170, 270, 370 and 470 are respectively disposed in the first, second, third and fourth reaction vessels 100, 200, 300 and 400 to stir the reactants inside the first, second, third and fourth reaction vessels 100, 200, 300 and 400. Referring to fig. 3, agitator assembly 170, 270, 370, 470 includes an agitator shaft 171, 271, 371, 471 and two blades 172, 272, 372, 472 extending transversely (i.e., in a direction intersecting the axis of the agitator shaft) from agitator shaft 171, 271, 371, 471. In some embodiments, agitator assembly 170, 270, 370, 470 may also have only one blade extending laterally from agitator shaft 171, 271, 371, 471. In other embodiments, agitator assemblies 170, 270, 370, and 470 may have more blades, e.g., 3, 4, 5, 6, 7, 8 blades, etc., extending laterally from agitator shafts 171, 271, 371, 471. In certain embodiments, the stirring assemblies 170, 270, 370, and 470 may be any one of an anchor stirrer, an anchor frame stirrer, or a straight blade stirrer.
In some embodiments, the system for preparing isocyanates may further comprise: and the metering pumping mechanism is arranged at the upstream of the feed inlet. The metering pumping mechanism includes a metering pump configured to deliver a volume of reactant into the reaction vessel. As shown in FIG. 3, with respect to the first reaction vessel 100, an amine metering pump 181 is provided upstream of the reactant amine feed port 113, and a first phosgene metering pump 182 is provided upstream of the phosgene feed ports 112a,112 b. Similarly, for the second reaction vessel 200, a second phosgene metering pump 280 is provided upstream of the phosgene feed ports 212a,212 b; for the third reaction vessel 300, a third phosgene metering pump 380 is provided upstream of the phosgene feed ports 312a,312 b; with respect to the fourth reaction vessel 400, a fourth phosgene metering pump 480 is provided upstream of the phosgene feed ports 412a,412 b. The metering pumping mechanism optionally includes a controller in signal communication with each metering pump and stopping the pumping operation based on the amount of reactant flowing through each metering pump. By means of the metering pump mechanism, the corresponding reactants (such as amine mixture, phosgene) can be accurately and quantitatively controlled to enter the reaction container. The metering pump may be a combination of a flow meter and a pump, such as one of a rotameter, a volumetric flow meter, an ultrasonic flow meter, and one of a volumetric pump, an impeller or an ejector pump.
In certain embodiments, the system for producing isocyanates herein further comprises an off-gas treatment apparatus, e.g., the first reaction vessel 100 comprises an off-gas treatment apparatus 810, the second reaction vessel 200 comprises an off-gas treatment apparatus 820, the third reaction vessel 300 comprises an off-gas treatment apparatus 830, and the fourth reaction vessel 400 comprises an off-gas treatment apparatus 840. In the reaction for preparing isocyanates by the phosgene liquid phase process, the reaction off-gases are mainly hydrogen chloride, which may also contain some unreacted phosgene and gaseous mixtures of other reaction products, and these off-gases are environmentally polluting and toxic. Moreover, in the preparation of isocyanates, excess phosgene is generally passed in order to increase the yield of isocyanate, so that some of the off-gases from the reaction vessel may be phosgene in large part (e.g., at least 90% or more). If the excess phosgene is directly discharged as tail gas, not only the environment is polluted, but also the production cost is greatly increased. In the invention, the tail gas treatment device is arranged to recycle or treat the tail gas of each reaction container, so that the system is more environment-friendly, the harm to the environment and personnel is reduced, and the production cost is greatly reduced.
As shown in fig. 3, the off- gas discharge ports 111c,111d of the first reaction vessel 100 are directly applied to the third reaction vessel 300 through the off-gas treatment device 810, for example, selectively connected to the phosgene feed ports 312a,312b of the third reaction vessel 300, so that the excess phosgene in the off-gas of the first reaction vessel 100 can be recycled in the third reaction vessel 300.
As shown in fig. 3, the off- gas discharge ports 411a,411b of the fourth reaction vessel 400 are directly applied to the second reaction vessel 200 through the off-gas treatment device 840, for example, selectively connected to the phosgene feed ports 212a,212b of the second reaction vessel 200, so that the excess phosgene in the off-gas of the fourth reaction vessel 400 can be recycled in the second reaction vessel 200.
In certain embodiments, the off- gas discharge ports 111c,111d of the first reaction vessel 100 are directly applied to the third reaction vessel 300 via the off-gas treatment device 810 (e.g., optionally in communication with the phosgene feed ports 312a,312b of the third reaction vessel 300), and the off- gas discharge ports 411a,411b of the fourth reaction vessel 400 are directly applied to the second reaction vessel 200 via the off-gas treatment device 840 (e.g., optionally in communication with the phosgene feed ports 212a,212b of the second reaction vessel 200), such that excess phosgene in the off-gas of the first reaction vessel 100 is recycled in the third reaction vessel 300 and excess phosgene in the off-gas of the fourth reaction vessel 400 is recycled in the second reaction vessel 200. In certain embodiments, the off-gas of the second reaction vessel 200 is predominantly hydrogen chloride, e.g., having a hydrogen chloride content of 60% or more (e.g., 65%, 70%, 75%, 80%, 85%), and a phosgene content of 40% or less (e.g., 35%, 30%, 25%, 20%, 15%, 10%). In certain embodiments, the off-gas of the third reaction vessel 300 is primarily hydrogen chloride and phosgene, e.g., a hydrogen chloride content of 40% or more (e.g., 45%, 50%, 55%, 60%, 65%) and a phosgene content of 60% or less (e.g., 55%, 50%, 45%, 40%, 35%, 30%). The off-gas of the second reaction vessel 200 and the third reaction vessel 300 is discharged after being treated by off- gas treatment devices 820 and 830, respectively. In certain embodiments, the tail gas treatment devices 820 and 830 may be acid mist purification towers, activated carbon adsorption towers.
As shown in fig. 4, in the system 20, the exhaust gas discharge ports 111c,111d of the first reaction vessel 100 are directly used in the third reaction vessel 300 through the exhaust gas treatment device 810, and the exhaust gas discharge ports 411a,411b of the fourth reaction vessel 400 are directly used in the third reaction vessel 300 through the exhaust gas treatment device 840, for example, are selectively communicated with the phosgene feed ports 312a,312b of the third reaction vessel 300, so that the excess phosgene in the exhaust gas of the first reaction vessel 100 and the fourth reaction vessel 400 is recycled in the third reaction vessel 300. Further, the off- gas discharge ports 311a,311b of the third reaction vessel 300 are directly applied to the second reaction vessel 200 through the off-gas treatment device 830, for example, are selectively communicated with the phosgene feed ports 212a,212b of the second reaction vessel 200, so that the excess phosgene in the off-gas of the third reaction vessel 300 can be recycled in the second reaction vessel 200. In certain embodiments, the off-gas of the second reaction vessel 200 is predominantly hydrogen chloride, e.g., having a hydrogen chloride content of 60% or more (e.g., 65%, 70%, 75%, 80%, 85%), and a phosgene content of 40% or less (e.g., 35%, 30%, 25%, 20%, 15%, 10%). The tail gas of the second reaction vessel 200 is treated by the tail gas treatment device 820 and then discharged. In certain embodiments, the tail gas treatment device 820 may be an acid mist purification tower, an activated carbon adsorption tower.
As shown in fig. 3 and 4, the system for determining the reaction conditions for preparing isocyanate by the phosgene liquid phase method may further include a purification apparatus 850, and the purification apparatus 850 is connected to the downstream of the fourth reaction vessel 400 for performing a purification treatment (e.g., removal of solvent or other impurities) on the reaction product isocyanate, so that the purity of the finally collected product isocyanate reaches a certain degree, for example, more than 90%. The purification device 850 is, for example, a vacuum distillation column, and can remove the solvent from the reactants flowing therein by the temperature and pressure of a heat transfer medium (e.g., water vapor) flowing therethrough.
In certain embodiments, a first transfer pump 190 is disposed between the outlet 120 of the first reaction vessel 100 and the outlet 220 of the second reaction vessel 200, the first transfer pump 190 being operable to pump the first reaction product between the outlet 120 of the first reaction vessel 100 and the outlet 220 of the second reaction vessel 200.
In certain embodiments, a second transfer pump 290 is disposed between the discharge port 220 of the second reaction vessel 200 and the discharge port 320 of the third reaction vessel 300, the second transfer pump 290 being operable to pump the second reaction product between the discharge port 220 of the second reaction vessel 200 and the discharge port 320 of the third reaction vessel 300.
In certain embodiments, a third transfer pump 390 is disposed between the discharge port 320 of the third reaction vessel 300 and the discharge port 420 of the fourth reaction vessel 400, the third transfer pump 390 being operable to pump the third reaction product between the discharge port 320 of the third reaction vessel 300 and the discharge port 420 of the fourth reaction vessel 400.
In some embodiments, a fourth material transfer pump 490 is disposed between the discharge port 420 of the fourth reaction vessel 400 and the purification apparatus 850, the fourth material transfer pump 490 being operable to pump the fourth reaction product between the discharge port 420 of the fourth reaction vessel 400 and the purification apparatus 850.
In the embodiment shown in fig. 3 and 4, the first transfer pump 190 is further connected to the first thermostat 910, and the first transfer pump 190 switchably pumps the reaction product to the discharge port 220 of the second reaction vessel 200 or the first thermostat 910. As described above with respect to the first temperature controller 910, the reactants in the first reaction vessel 100 may be pumped into the first temperature controller 910 through the phosgene feed port 112a, through the first transfer pump 190 during the reaction, and then into the first reaction vessel 100 through the phosgene feed port 112b again after temperature control, thereby completing the external circulation, and thus improving the phosgene utilization.
In some embodiments shown in fig. 3 and 4, a second transfer pump 290 is also provided that is connected to a second thermostat 920. Similarly, the second transfer pump 290 can pump the reaction products flowing out of the phosgene feed port 212a through the second thermostat 920, the phosgene feed port 212b and into the second reaction vessel 200 for external circulation. In addition, when the reaction in the second reaction vessel 200 is completed, the second transfer pump 290 may pump the reaction product within the second reaction vessel 200 downstream, for example, to the third reaction vessel 300, and the like.
In some embodiments shown in fig. 3 and 4, a third transfer pump 390 is also provided that is connected to a third thermostat 930. Similarly, the third material transfer pump 390 can pump the reaction product flowing out of the phosgene feed port 312a through the third temperature regulator 930 and the phosgene feed port 312b into the third reaction vessel 300 for external circulation. In addition, when the reaction in the third reaction vessel 300 is completed, the third transfer pump 390 may pump the reaction product within the third reaction vessel 300 downstream, for example, to the fourth reaction vessel 400, and the like.
In some embodiments shown in fig. 3 and 4, a fourth material transfer pump 490 is also provided that is connected to a fourth thermostat 940. Similarly, the fourth material transfer pump 490 can pump the reaction products flowing out of the phosgene feed inlet 412a through the fourth temperature regulator 940, the phosgene feed inlet 412b and into the fourth reaction vessel 400 for external circulation. In addition, when the reaction in the fourth reaction vessel 400 is completed, the fourth material-transferring pump 490 may pump the reaction product within the fourth reaction vessel 400 downstream, for example, to the purification apparatus 850, etc.
As described above, the system of the present application requires the reaction product to be transferred from the first reaction vessel 100 to the second reaction vessel 200, from the second reaction vessel 200 to the third reaction vessel 300, and from the third reaction vessel 300 to the fourth reaction vessel 400 during the reaction to continue the reaction, and therefore requires the transfer of the reaction product through the discharge port 120 communicating with the first reaction vessel 100 and the discharge port 220 of the second reaction vessel 200, the discharge port 220 communicating with the second reaction vessel 200 and the discharge port 320 communicating with the third reaction vessel 300, and the discharge port 320 communicating with the third reaction vessel 300 and the discharge port 420 communicating with the fourth reaction vessel 400. The material transfer can be performed by the first material transfer pump 190, the second material transfer pump 290, and the third material transfer pump 390.
In some embodiments, a pipeline connecting the outlet 120 of the first reaction vessel 100 and the outlet 220 of the second reaction vessel 200 is provided with a material transfer window 610, and the material transfer window 610 is configured to visually observe the inside of the pipeline. Can observe the inside reactant residual situation of pipeline through changeing material observation window 610, be convenient for judge the completion degree of changeing the material.
In some embodiments, a pipeline connecting the discharge port 220 of the second reaction vessel 200 and the discharge port 320 of the third reaction vessel 300 is provided with a material transfer observation window 620, and the material transfer observation window 620 is configured to visually observe the inside of the pipeline. Can observe the inside reactant residue condition of pipeline through changeing material observation window 620, be convenient for judge the completion degree of changeing the material.
In some embodiments, a pipeline connecting the discharge port 320 of the third reaction vessel 300 and the discharge port 420 of the fourth reaction vessel 400 is provided with a material transfer observation window 630, and the material transfer observation window 630 is configured to visually observe the inside of the pipeline. Can observe the inside reactant residual condition of pipeline through changeing material observation window 630, be convenient for judge the completion degree of changeing the material.
It should be noted that, the above list only some methods for preparing isocyanate by using the system of the present application, but the method for preparing isocyanate by using the system of the present application is not limited thereto.
The present application provides the following embodiments:
embodiment 1: a process for the preparation of isocyanates, characterized in that it comprises the following steps:
(a) mixing reactant amine and phosgene, and carrying out a first reaction in a first reaction vessel at the temperature of-30-90 ℃ to obtain a first reaction product;
(b) transferring the first reaction product obtained in the step (a) into a second reaction container, mixing the first reaction product with phosgene, and carrying out a second reaction in the second reaction container at the temperature of 90-200 ℃ to obtain a second reaction product;
(c) transferring the second reaction product obtained in the step (b) into a third reaction container, mixing the second reaction product with phosgene, and carrying out a third reaction in the third reaction container at the temperature of 120-250 ℃ to obtain a third reaction product;
(d) transferring the third reaction product obtained in the step (c) into a fourth reaction container, mixing the third reaction product with phosgene, and carrying out a fourth reaction in the fourth reaction container at a certain constant temperature of 120-300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein the content of the first and second substances,
at least a portion of the phosgene in step (b) is derived from the off-gas of the fourth reaction vessel in step (d), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a); or
At least a portion of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
Embodiment 2: the method according to embodiment 1, wherein,
the off-gas from the first reaction vessel in step (a) comprises the phosgene that has not reacted to completion in step (a);
the off-gas from the third reaction vessel in step (c) comprises hydrogen chloride and the phosgene that has not reacted to completion in step (c), and optionally, the phosgene that has not reacted to completion in step (a), the phosgene that has not reacted to completion in step (d); and/or
The off-gas of the fourth reaction vessel in step (d) comprises hydrogen chloride and the phosgene that has not reacted to completion in step (d).
Embodiment 3: the process according to embodiment 1 or 2, characterized in that the phosgene content (w/w) in the off-gas of the first reaction vessel in step (a) is 90% or more.
Embodiment 4: the process according to any one of the preceding embodiments, characterized in that the phosgene content (w/w) in the off-gas of the third reaction vessel in step (c) is 60% or less.
Embodiment 5: the process according to any of the preceding embodiments, characterized in that the phosgene content (w/w) in the off-gas of the fourth reactor in step (d) is 95% or more.
Embodiment 6: the method according to any of the preceding embodiments,
the first reaction product comprises an intermediate carbamoylchloramine hydrochloride, and optionally, one or more selected from the group consisting of: carbamoyl chloride, unreacted amine from step (a) and phosgene;
the second reaction product comprises carbamoyl chloride and hydrogen chloride, and optionally, one or more selected from the group consisting of: the amine and phosgene which have not reacted completely in step (a), the carbamoylchloramine hydrochloride which has not reacted completely in step (b), and phosgene;
the third reaction product comprises isocyanate and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamoylchloramine hydrochloride, hydrogen chloride and phosgene in step (b), unreacted carbamoylchloride and phosgene in step (c);
the fourth reaction product comprises an isocyanate, and optionally, one or more selected from the group consisting of: hydrogen chloride, the incomplete amine and phosgene reaction in step (a), the incomplete intermediate carbamoylchloramine hydrochloride and phosgene reaction in step (b), the incomplete carbamoylchloride and phosgene reaction in step (c), and the incomplete phosgene reaction in step (d).
Embodiment 7: the method according to any one of the preceding embodiments, wherein before step (a), a solvent of reactant amine is put into the first reaction vessel and cooled to 0-10 ℃ under the protection of nitrogen.
Embodiment 8: the method according to any of the preceding embodiments,
said phosgene in step (b) is derived exclusively from off-gas from said fourth reaction vessel in step (d), and/or said phosgene in step (c) is derived exclusively from off-gas from said first reaction vessel in step (a); or
The phosgene in step (b) is derived exclusively from off-gas from the third reaction vessel in step (c), and/or the phosgene in step (c) is derived exclusively from off-gas from the first reaction vessel in step (a) and/or from off-gas from the fourth reaction vessel in step (d).
Embodiment 9: the method according to any one of the preceding embodiments, characterized in that the flow rates of the reactant amine and phosgene are adjusted by an amine metering pump and a phosgene metering pump of the first reaction vessel, respectively, so that the reactant amine and phosgene are fed into the first reaction vessel for reaction at a constant rate.
Embodiment 10: the method according to any one of the preceding embodiments, wherein the first reaction in step (a) is carried out in two temperature ranges, wherein the reaction temperature in the first stage is maintained at 30-50 ℃, and the reaction temperature in the second stage is further increased to 50-90 ℃.
Embodiment 11: the process according to any one of the preceding embodiments, characterized in that the molar ratio of the total amount of reactants amine and phosgene used in step (a), step (b), step (c) and step (d) is between 1:4 and 1: 8.
Embodiment 12: the method according to any of the preceding embodiments, characterized in that the method further comprises the steps of: and (d) transferring the fourth reaction product obtained in the step (d) into a purification device for rectification to obtain purified isocyanate.
Embodiment 13: the method according to any of the preceding embodiments, characterized in that the reaction of each step is carried out under atmospheric conditions.
Embodiment 14: the method according to any one of the preceding embodiments, characterized in that phosgene is used in stoichiometric excess of 0 to 150% over the theoretical value, based on the amine groups of the reactant amine, in the first reaction vessel.
Embodiment 15: the method of any one of the preceding embodiments, wherein at least a portion of the reactant amine in step (a) is dissolved in a solvent, wherein the solvent comprises one or more selected from the group consisting of: chlorobenzene, o-dichlorobenzene, toluene, xylene, perchloroethylene, trichlorofluoromethane and butyl acetate.
Embodiment 16: the method of any of the preceding embodiments, wherein the reactant amine has the formula R (NH)2)nWherein n is 1, 2 or 3 and R is an aliphatic, alicyclic or aromatic hydrocarbon group having 2 to 10 carbon atoms.
Embodiment 17: the method according to any one of the preceding embodiments, wherein the reactant amine is selected from one or more of the group consisting of: ethylamine, butylamine, pentamethylene diamine, hexamethylene diamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluene diamine, 1, 5-naphthalenediamine, diphenylmethane diamine, dicyclohexylmethane diamine, m-cyclohexyldimethylene diamine, isophorone diamine, trans-1, 4-cyclohexanediamine.
Embodiment 18: the method according to any of the preceding embodiments, characterized in that the isocyanate is selected from the group consisting of: diphenylmethane diisocyanate as a pure isomer or as a mixture of isomers, toluene diisocyanate as a pure isomer or as a mixture of isomers, 2, 6-xylene isocyanate, 1, 5-naphthalene diisocyanate, methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, isobutyl isocyanate, tert-butyl isocyanate, amyl isocyanate (e.g., pentamethylene diisocyanate), tert-amyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexamethylene diisocyanate), cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate (e.g., p-phenylene diisocyanate).
Embodiment 19: a system for preparing isocyanate, which is characterized by comprising a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel and a temperature control device, wherein,
the first reaction vessel includes: a solvent feed port, a phosgene feed port, a reactant amine feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the first reaction vessel; a sampling port configured to operably extract a volume of reaction sample from the first reaction vessel;
the second reaction vessel, the third reaction vessel and the fourth reaction vessel each comprise: a phosgene feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the second, third or fourth reaction vessel, respectively; a sampling port configured to operably extract a volume of reaction sample from the second, third, or fourth reaction vessel;
the temperature control device is configured to optionally adjust the temperature of the first, second, third, and fourth reaction vessels to a predetermined value;
wherein the content of the first and second substances,
the air vent of the first reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the first reaction vessel is selectively communicated with the discharge hole of the second reaction vessel; the air vent of the second reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the second reaction vessel is selectively communicated with the discharge hole of the third reaction vessel; the air vent of the third reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the third reaction vessel is selectively communicated with the discharge hole of the fourth reaction vessel; the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and
the off-gas discharge of the first reaction vessel is in selective communication with the third reaction vessel and the off-gas discharge of the fourth reaction vessel is in selective communication with the second reaction vessel; or the tail gas discharge port of the first reaction vessel and the tail gas discharge port of the fourth reaction vessel are selectively communicated with the third reaction vessel, and the tail gas discharge port of the third reaction vessel is selectively communicated with the second reaction vessel.
Embodiment 20: the system of embodiment 19, wherein the off-gas discharge of the first reaction vessel is in selective communication with the phosgene feed inlet of the third reaction vessel and the off-gas discharge of the fourth reaction vessel is in selective communication with the phosgene feed inlet of the second reaction vessel; or the tail gas discharge port of the first reaction container and the tail gas discharge port of the fourth reaction container are selectively communicated with the phosgene feed port of the third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the phosgene feed port of the second reaction container.
Embodiment 21: the system of embodiment 19, wherein the discharge ports of the first, second, third and/or fourth reaction vessels are each in selective communication with an emergency discharge device.
Embodiment 22: the system according to embodiment 19, characterized in that the first reaction vessel is provided with a first precooler in communication with its solvent feed or tail gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its tail gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its tail gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its tail gas discharge.
Embodiment 23: the system of embodiment 19, wherein the temperature control device comprises a temperature sensor that is a contact temperature sensor and/or a non-contact temperature sensor, wherein,
the contact temperature sensor can be arranged at any one or more of the following positions: the first reaction vessel interior, the side wall of the first reaction vessel, the second reaction vessel interior, the side wall of the second reaction vessel, the third reaction vessel interior, the side wall of the third reaction vessel, the fourth reaction vessel interior, and the side wall of the fourth reaction vessel;
the non-contact temperature sensor is arranged at a distance from the first reaction vessel, and/or the second reaction vessel, and/or the third reaction vessel, and/or the fourth reaction vessel.
Embodiment 24: the system of embodiment 23, wherein the temperature control device further comprises:
heat exchange means attachable to or formed by the side walls of the first, second, third and fourth reaction vessels for heat exchange with reactants within the first, second, third and fourth reaction vessels; and
a temperature controller coupled to the temperature sensor and the heat exchange assembly, the temperature controller configured to receive a measurement signal of the temperature sensor and operate the heat exchange device according to the measurement signal.
Embodiment 25: the system of any one of embodiments 19-24, wherein the first, second, third, and fourth reaction vessels are selected from the group consisting of: a carbon steel reaction kettle, a stainless steel reaction kettle, an enamel reaction kettle and a steel lining reaction kettle; and/or
And observation holes are formed in the side walls of the first reaction vessel, the second reaction vessel, the third reaction vessel and the fourth reaction vessel and used for visually observing the interiors of the first reaction vessel, the second reaction vessel, the third reaction vessel and the fourth reaction vessel.
Embodiment 26: the system of any of embodiments 19-25, further comprising one or more of the following components: the device comprises a stirring assembly, a metering pumping mechanism, a tail gas treatment device and a purification device;
wherein the stirring assembly is disposable within the first reaction vessel, the second reaction vessel, the third reaction vessel, and/or the fourth reaction vessel, the stirring assembly comprising a stirring shaft and a plurality of blades extending laterally outward from the stirring shaft, the stirring shaft configured to operably effect one or more of the following motions: rotation, translation, and oscillation;
the metering pumping mechanism is disposed upstream of one or more of the following: a solvent feed, a phosgene feed, a reactant amine feed of the first reaction vessel, and phosgene feeds of the second, third, and fourth reaction vessels to control the amount of reactants pumped through these openings;
the tail gas treatment device of the first reaction vessel is directly applied to the third reaction vessel, and the tail gas treatment device of the fourth reaction vessel is directly applied to the second reaction vessel; or the tail gas treatment device of the first reaction vessel and the tail gas treatment device of the fourth reaction vessel are both directly applied to the third reaction vessel, and the tail gas treatment device of the third reaction vessel is directly applied to the second reaction vessel;
the purification device is connected downstream of the fourth reaction vessel.
Embodiment 27: the system of any of embodiments 19-26,
a first material transferring pump is arranged between the discharge port of the first reaction vessel and the discharge port of the second reaction vessel, and the first material transferring pump is operable to pump a first reaction product between the discharge port of the first reaction vessel and the discharge port of the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the first reaction vessel and the discharge port of the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline; and/or
A second material transferring pump is arranged between the discharge port of the second reaction vessel and the discharge port of the third reaction vessel, and the second material transferring pump can be used for pumping a second reaction product between the discharge port of the second reaction vessel and the discharge port of the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the second reaction vessel with the discharge port of the third reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline; and/or
A third material transferring pump is arranged between the discharge port of the third reaction vessel and the discharge port of the fourth reaction vessel, and the third material transferring pump can be used for pumping a third reaction product between the discharge port of the third reaction vessel and the discharge port of the fourth reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the discharge port of the third reaction vessel and the discharge port of the fourth reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline; and/or
A fifth material transfer pump is arranged between the tail gas treatment device of the first reaction vessel and the third reaction vessel, and the fifth material transfer pump can be used for pumping the tail gas of the first reaction vessel between the tail gas treatment device of the first reaction vessel and the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline which is communicated with the tail gas treatment device of the first reaction container and the third reaction container, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline; and/or
A sixth material transfer pump is arranged between the tail gas treatment device of the fourth reaction vessel and the second reaction vessel, and the sixth material transfer pump can be used for pumping the tail gas of the fourth reaction vessel between the tail gas treatment device of the fourth reaction vessel and the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline which is communicated with the tail gas treatment device of the fourth reaction vessel and the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline; and/or
A seventh material transfer pump is arranged between the tail gas treatment device of the fourth reaction vessel and the third reaction vessel, and the seventh material transfer pump can be used for pumping the tail gas of the fourth reaction vessel between the tail gas treatment device of the fourth reaction vessel and the third reaction vessel; and/or a material transferring observation window is arranged on a pipeline which is communicated with the tail gas treatment device of the fourth reaction vessel and the third reaction vessel, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
An eighth material transfer pump is arranged between the tail gas treatment device of the third reaction vessel and the second reaction vessel, and the eighth material transfer pump can be used for pumping the tail gas of the third reaction vessel between the tail gas treatment device of the third reaction vessel and the second reaction vessel; and/or a material transferring observation window is arranged on a pipeline communicating the tail gas treatment device of the third reaction vessel with the second reaction vessel, and the material transferring observation window is configured to be used for visually observing the interior of the pipeline.
Embodiment 28: the system of embodiment 27, wherein the first and second sensors are configured to,
a first temperature regulator is arranged upstream of a phosgene feed inlet of the first reaction vessel, and phosgene can selectively enter the first reaction vessel through the first temperature regulator; the first temperature regulator is connected to the first transfer pump, and the first transfer pump switchably pumps the first reaction product to the discharge port of the second reaction vessel or the first temperature regulator; and/or
A second temperature regulator is arranged upstream of the phosgene feed inlet of the second reaction vessel, and phosgene can selectively enter the second reaction vessel through the second temperature regulator; the second attemperator is connected to the second transfer pump, which switchably pumps a second reaction product downstream of the second attemperator or a second reaction vessel; and/or
A third temperature regulator is arranged at the upstream of the phosgene feed inlet of the third reaction vessel, and phosgene can selectively enter the third reaction vessel through the third temperature regulator; the third attemperator is connected to the third transfer pump, which switchably pumps a third reaction product downstream of the third attemperator or a third reaction vessel; and/or
A fourth temperature regulator is arranged upstream of a phosgene feed inlet of the fourth reaction vessel, and phosgene can selectively enter the fourth reaction vessel through the fourth temperature regulator; the fourth thermostat is connected to a fourth transfer pump that switchably pumps a fourth reaction product downstream of the fourth thermostat or fourth reaction vessel.
Examples
The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto.
Example 1
Under the condition of normal pressure, phosgene is directly introduced into each reaction container without recycling tail gas of each reaction container and external circulation. Specific reaction raw materials and charge amounts are shown in table 1.
TABLE 1
Figure BDA0003011563480000411
The embodiment comprises the following steps:
(1) putting 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, filling the bottom with the raw material, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring without external circulation, starting a phosgene metering pump to add liquid phosgene at a constant speed of 2.2kg/hr (17.6kg/8hr), timing for 20min, then starting an amine solution metering pump to add liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable to form salt, and gradually raising the reaction temperature and keeping the temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 2.2kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours.
(2) Transferring the materials into a high-temperature kettle R102, heating the materials from 90 ℃ to 120 ℃ in 0.5 hour, heating at the speed of 10 ℃/hr, and adding liquid phosgene at the constant speed of 2.2kg/hr by using a phosgene metering pump, wherein the total time is 3 hours. Heating from 120 ℃ to 180 ℃ at a heating rate of 10 ℃/hr, and adding liquid phosgene at a constant speed of 2.2kg/hr by using a phosgene metering pump, wherein the total time is 6 hours.
(3) Starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, reacting for 6 hours at a constant temperature of 180 ℃ under normal pressure, and not completely dissolving; then reacting for 23 hours at constant temperature of 180 ℃ under normal pressure, and finally completely dissolving and discharging. Analytical GC tests gave 12.2kg of the product pentamethylene diisocyanate with a conversion of 90%.
In the preparation of the isocyanates according to this example, phosgene is actually used in an amount of about 110kg (2.2 kg/hr. times.50 h), which far exceeds the theoretical requirement of 17.4kg for phosgene.
Example 2
Phosgene is directly introduced into each reaction vessel under normal pressure, and the tail gas of each reaction vessel is not recycled, but is recycled. Specific reaction raw materials and charge amounts are shown in table 2.
TABLE 2
Figure BDA0003011563480000421
The embodiment comprises the following steps:
(1) putting 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, filling a bottom, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4kg/8hr), timing for 20min, starting an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable for salifying, and gradually raising the reaction temperature and keeping the temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 2.2kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours.
(2) Transferring the materials into a high-temperature kettle R102, heating the materials from 90 ℃ to 120 ℃ in 0.5 hour, heating at the speed of 10 ℃/hr, and adding liquid phosgene at the constant speed of 2.2kg/hr by using a phosgene metering pump, wherein the total time is 3 hours. Heating from 120 ℃ to 180 ℃ at a heating rate of 10 ℃/hr, and adding liquid phosgene at a constant speed of 2.2kg/hr by using a phosgene metering pump, wherein the total time is 6 hours.
(3) Starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, reacting for 6 hours at a constant temperature of 180 ℃ under normal pressure, and not completely dissolving; then reacting for 14 hours at constant temperature of 180 ℃ under normal pressure, and finally completely dissolving and discharging. Analytical GC tests gave 12.4kg of the product pentamethylene diisocyanate with a conversion of 91%.
In the preparation of the isocyanates according to this example, phosgene was used in an amount of about 91kg (2.2 kg/hr. times.41 h) and far in excess of the theoretical requirement of 17.4kg for phosgene. However, the reaction time was reduced by 9 hours and the amount of phosgene used was reduced by about 20kg, as compared with example 1.
Example 3
Under the condition of normal pressure, external circulation is opened, tail gas of the low-temperature kettle R101 is mechanically applied to the high-temperature kettle R103, and then is discharged; and (3) mechanically applying the tail gas of the high-temperature kettle R104 to the high-temperature kettle R102, then discharging, and supplementing fresh phosgene when the phosgene recycled in the tail gas is insufficient. Specific reaction raw materials and charge amounts are shown in table 3.
TABLE 3
Figure BDA0003011563480000431
The embodiment comprises the following steps:
(1) putting 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, filling a bottom, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4kg/8hr), timing for 20min, starting an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable for salifying, and gradually raising the reaction temperature and keeping the temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 2.2kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours.
(2) Transferring the materials into a high temperature kettle R102, and heating from 90 ℃ to 170 ℃ at a heating rate of 10 ℃/hr for 0.5 hour. And recycling the tail gas of the high-temperature kettle R104 to the high-temperature kettle R102, and introducing no fresh phosgene into the high-temperature kettle R102 for 7.5 hours in total.
(3) Transferring the material into a high temperature kettle R103, increasing the temperature from 170 ℃ to 180 ℃ and preserving the temperature when the material takes 0.5 hour, adding liquid phosgene at a constant speed of 1.5Kg/hr by using a phosgene metering pump, and receiving tail gas (about 2Kg/h) of a low temperature kettle R101 for 7 hours in total.
(4) Transferring the materials into a high-temperature kettle R104, reacting at constant temperature of 180 ℃ under normal pressure, adding liquid phosgene at a constant speed of 3.0kg/hr by using a phosgene metering pump for 7 hours, and finally completely dissolving and discharging the materials. Analytical GC tests gave 12.2kg of the product pentamethylene diisocyanate with a conversion of 90%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 59kg, which was about 51kg less (i.e., about 47% less) than the amount of phosgene used in example 1 and about 32kg less (i.e., about 35% less) than the amount of phosgene used in example 2. Moreover, the total reaction time was reduced by 14 hours compared with example 1 and by 5 hours compared with example 2.
Example 4
Under the condition of normal pressure, external circulation is opened, tail gas of the low-temperature reactor R101 and the high-temperature reactor R104 is mechanically applied to the high-temperature reactor R103, the tail gas of the high-temperature reactor R103 is mechanically applied to the high-temperature reactor R102, and then the tail gas is discharged. The specific reaction materials and amounts of charge are shown in Table 4.
TABLE 4
Figure BDA0003011563480000441
The embodiment comprises the following steps:
(1) putting 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, filling a bottom, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4kg/8hr), timing for 20min, starting an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable for salifying, and gradually raising the reaction temperature and keeping the temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 1.5kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours. And then the tail gas of the low temperature reactor R101 is mechanically applied to the high temperature reactor R103.
(2) Transferring the materials into a high-temperature kettle R102, increasing the temperature from 90 ℃ to 170 ℃ at the temperature increasing speed of 10 ℃/hr for 0.5 hour, introducing tail gas (about 3.2kg/h) of the high-temperature kettle R103 into the high-temperature kettle R102, and using fresh phosgene in total for 7 hours without using fresh phosgene.
(3) Transferring the materials into a high temperature kettle R103, increasing the temperature from 170 ℃ to 180 ℃ and preserving the temperature for 0.5 hour, and receiving the tail gas (about 1.7kg/h) of the low temperature kettle R101 and the tail gas (about 1.8kg/h) of the high temperature kettle R104 for 7 hours in total.
(4) Transferring the materials into a high-temperature kettle R104, reacting at constant temperature of 180 ℃ under normal pressure, adding liquid phosgene at a constant speed of 2.2kg/hr by using a phosgene metering pump for 7 hours in total, and finally completely dissolving and discharging the materials. Analytical GC tests gave 12.0kg of the product pentamethylene diisocyanate with a conversion of 89%.
In the isocyanate production process of this example, the actual amount of phosgene used was about 40.1kg, and the actual amount of phosgene used was further reduced as compared with example 3, and the time consumption of the entire reaction was further reduced.
Example 5
Under the condition of normal pressure, external circulation is opened, tail gas of the low-temperature reactor R101 and the high-temperature reactor R104 is mechanically applied to the high-temperature reactor R103, the tail gas of the high-temperature reactor R103 is mechanically applied to the high-temperature reactor R102, and then the tail gas is discharged. Specific reaction raw materials and charge amounts are shown in table 5.
TABLE 5
Figure BDA0003011563480000451
The embodiment comprises the following steps:
(1) putting 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, filling the bottom with the raw material, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, starting an amine solution metering pump after timing for 20min, adding liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable for salifying, and gradually heating and maintaining the reaction temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 1.5kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours. And then the tail gas of the low temperature reactor R101 is mechanically applied to the high temperature reactor R103.
(2) Transferring the materials into a high-temperature kettle R102, increasing the temperature from 90 ℃ to 170 ℃ at the temperature increasing speed of 10 ℃/hr for 0.5 hour, introducing tail gas (about 3.2kg/h) of the high-temperature kettle R103 into the high-temperature kettle R102, and using fresh phosgene in total for 7 hours without using fresh phosgene.
(3) Transferring the materials into a high temperature kettle R103, increasing the temperature from 170 ℃ to 180 ℃ and preserving the temperature for 0.5 hour, and receiving the tail gas (about 1.7kg/h) of the low temperature kettle R101 and the tail gas (about 1.8kg/h) of the high temperature kettle R104 for 7 hours in total.
(4) Transferring the materials into a high-temperature kettle R104, reacting at constant temperature of 180 ℃ under normal pressure, adding liquid phosgene at a constant speed of 2.0kg/hr by using a phosgene metering pump for 7 hours in total, and finally completely dissolving and discharging the materials. Analytical GC tests gave 12.1kg of hexamethylene diisocyanate as product with a conversion of 93%.
In the isocyanate production process of this example, the actual amount of phosgene used was about 40.1kg, and the actual amount of phosgene used was further reduced as compared with example 3.
Example 6
Under the condition of normal pressure, external circulation is opened, tail gas of the low-temperature reactor R101 and the high-temperature reactor R104 is mechanically applied to the high-temperature reactor R103, the tail gas of the high-temperature reactor R103 is mechanically applied to the high-temperature reactor R102, and then the tail gas is discharged. The specific reaction materials and amounts of charge are shown in Table 6.
TABLE 6
Figure BDA0003011563480000461
The embodiment comprises the following steps:
(1) putting 32kg of chlorobenzene as a raw material into a low-temperature kettle R101, filling the bottom of the low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, starting an amine solution metering pump after timing for 20min, adding a liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable to form salt, and gradually heating and maintaining the reaction temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 1.5kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours. And then the tail gas of the low temperature reactor R101 is mechanically applied to the high temperature reactor R103.
(2) Transferring the materials into a high-temperature kettle R102, increasing the temperature from 90 ℃ to 170 ℃ at the temperature increasing speed of 10 ℃/hr for 0.5 hour, introducing tail gas (about 3.2kg/h) of the high-temperature kettle R103 into the high-temperature kettle R102, and using fresh phosgene in total for 7 hours without using fresh phosgene.
(3) Transferring the materials into a high temperature kettle R103, increasing the temperature from 170 ℃ to 180 ℃ and preserving the temperature for 0.5 hour, and receiving the tail gas (about 1.7kg/h) of the low temperature kettle R101 and the tail gas (about 1.8kg/h) of the high temperature kettle R104 for 7 hours in total.
(4) Transferring the materials into a high-temperature kettle R104, reacting at constant temperature of 180 ℃ under normal pressure, adding liquid phosgene at a constant speed of 2.0kg/hr by using a phosgene metering pump for 7 hours in total, and finally completely dissolving and discharging the materials. Analytical GC tests gave 12.8kg of product p-phenylene diisocyanate with a conversion of 96%.
In the isocyanate production process of this example, the actual amount of phosgene used was about 40.1kg, and the actual amount of phosgene used was further reduced as compared with example 3, and the time consumption of the entire reaction was further reduced.
Example 7
Under the condition of normal pressure, external circulation is opened, tail gas of the low-temperature reactor R101 and the high-temperature reactor R104 is mechanically applied to the high-temperature reactor R103, the tail gas of the high-temperature reactor R103 is mechanically applied to the high-temperature reactor R102, and then the tail gas is discharged. Specific reaction materials and amounts of charge are shown in table 7.
TABLE 7
Figure BDA0003011563480000471
The embodiment comprises the following steps:
(1) putting 32kg of chlorobenzene as a raw material into a low-temperature kettle R101, filling the bottom of the low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring, starting external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, starting an amine solution metering pump after timing for 20min, adding a liquid amine solution at a constant speed of 6.1kg/hr (49kg/8hr), keeping the reaction solution stable to form salt, and gradually heating and maintaining the reaction temperature at 35-45 ℃. After the addition, stirring was continued for 10min, and the total salt formation time was 8.5 hours. The cooling is changed into heating, a phosgene metering pump is started to add liquid phosgene at a constant speed of 1.5kg/hr, the temperature of the reaction liquid is raised from 50 ℃ to 90 ℃, the temperature raising speed is 10 ℃/hr, and the total time is 4 hours. And then the tail gas of the low temperature reactor R101 is mechanically applied to the high temperature reactor R103.
(2) Transferring the materials into a high-temperature kettle R102, increasing the temperature from 90 ℃ to 170 ℃ at the temperature increasing speed of 10 ℃/hr for 0.5 hour, introducing tail gas (about 3.2kg/h) of the high-temperature kettle R103 into the high-temperature kettle R102, and using fresh phosgene in total for 7 hours without using fresh phosgene.
(3) Transferring the materials into a high temperature kettle R103, increasing the temperature from 170 ℃ to 180 ℃ and preserving the temperature for 0.5 hour, and receiving the tail gas (about 1.7kg/h) of the low temperature kettle R101 and the tail gas (about 1.8kg/h) of the high temperature kettle R104 for 7 hours in total.
(4) Transferring the materials into a high-temperature kettle R104, reacting at constant temperature of 180 ℃ under normal pressure, adding liquid phosgene at a constant speed of 2.0kg/hr by using a phosgene metering pump for 7 hours in total, and finally completely dissolving and discharging the materials. Analytical GC tests gave 12.3kg of the product toluene diisocyanate with a conversion of 96%.
In the isocyanate production process of this example, the actual amount of phosgene used was about 40.1kg, and the actual amount of phosgene used was further reduced as compared with example 3, and the time consumption of the entire reaction was further reduced.
It should be noted that although in the above detailed description different parts of the system and sub-parts of these different parts are mentioned, this division is only exemplary and not mandatory. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art from a study of the specification, the drawings, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. In the practical application of the present application, one element may perform the functions of several technical features recited in the claims.

Claims (10)

1. A process for the preparation of isocyanates, characterized in that it comprises the following steps:
(a) mixing reactant amine and phosgene, and carrying out a first reaction in a first reaction vessel at the temperature of-30-90 ℃ to obtain a first reaction product;
(b) transferring the first reaction product obtained in the step (a) into a second reaction container, mixing the first reaction product with phosgene, and carrying out a second reaction in the second reaction container at the temperature of 90-200 ℃ to obtain a second reaction product;
(c) transferring the second reaction product obtained in the step (b) into a third reaction container, mixing the second reaction product with phosgene, and carrying out a third reaction in the third reaction container at the temperature of 120-250 ℃ to obtain a third reaction product;
(d) transferring the third reaction product obtained in the step (c) into a fourth reaction container, mixing the third reaction product with phosgene, and carrying out a fourth reaction in the fourth reaction container at a certain constant temperature of 120-300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein the content of the first and second substances,
at least a portion of the phosgene in step (b) is derived from the off-gas of the fourth reaction vessel in step (d), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a); or
At least a portion of the phosgene in step (b) is derived from the off-gas of the third reaction vessel in step (c), and at least a portion of the phosgene in step (c) is derived from the off-gas of the first reaction vessel in step (a) and/or the off-gas of the fourth reaction vessel in step (d).
2. The method of claim 1,
the off-gas from the first reaction vessel in step (a) comprises the phosgene that has not reacted to completion in step (a);
the off-gas from the third reaction vessel in step (c) comprises hydrogen chloride and the phosgene that has not reacted to completion in step (c), and optionally, the phosgene that has not reacted to completion in step (a), the phosgene that has not reacted to completion in step (d); and/or
The off-gas of the fourth reaction vessel in step (d) comprises hydrogen chloride and the phosgene that has not reacted to completion in step (d).
3. The process according to claim 1 or 2, characterized in that the phosgene content (w/w) in the off-gas of the first reaction vessel in step (a) is 90% or more.
4. The process according to any one of the preceding claims, characterized in that the phosgene content (w/w) in the off-gas of the third reaction vessel in step (c) is 60% or less.
5. The process according to any of the preceding claims, characterized in that the phosgene content (w/w) in the off-gas of the fourth reactor in step (d) is 95% or more.
6. A system for preparing isocyanate, which is characterized by comprising a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel and a temperature control device, wherein,
the first reaction vessel includes: a solvent feed port, a phosgene feed port, a reactant amine feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the first reaction vessel; a sampling port configured to operably extract a volume of reaction sample from the first reaction vessel;
the second reaction vessel, the third reaction vessel and the fourth reaction vessel each comprise: a phosgene feed port; a tail gas discharge port and a discharge port; a vent; the vent is configured to optionally communicate with an emergency discharge device to allow gas to enter or exit the second, third or fourth reaction vessel, respectively; a sampling port configured to operably extract a volume of reaction sample from the second, third, or fourth reaction vessel;
the temperature control device is configured to optionally adjust the temperature of the first, second, third, and fourth reaction vessels to a predetermined value;
wherein the content of the first and second substances,
the air vent of the first reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the first reaction vessel is selectively communicated with the discharge hole of the second reaction vessel; the air vent of the second reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the second reaction vessel is selectively communicated with the discharge hole of the third reaction vessel; the air vent of the third reaction vessel is selectively communicated with an emergency discharging device, and the discharge hole of the third reaction vessel is selectively communicated with the discharge hole of the fourth reaction vessel; the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and
the off-gas discharge of the first reaction vessel is in selective communication with the third reaction vessel and the off-gas discharge of the fourth reaction vessel is in selective communication with the second reaction vessel; or the tail gas discharge port of the first reaction vessel and the tail gas discharge port of the fourth reaction vessel are selectively communicated with the third reaction vessel, and the tail gas discharge port of the third reaction vessel is selectively communicated with the second reaction vessel.
7. The system of claim 6, wherein the off-gas discharge of the first reaction vessel is in selective communication with the phosgene feed inlet of the third reaction vessel and the off-gas discharge of the fourth reaction vessel is in selective communication with the phosgene feed inlet of the second reaction vessel; or the tail gas discharge port of the first reaction container and the tail gas discharge port of the fourth reaction container are selectively communicated with the phosgene feed port of the third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the phosgene feed port of the second reaction container.
8. The system of claim 6, wherein the discharge ports of the first, second, third and/or fourth reaction vessels are each in selective communication with an emergency discharge device.
9. The system according to claim 6, characterized in that the first reaction vessel is provided with a first precooler in communication with its solvent feed or tail gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its tail gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its tail gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its tail gas discharge.
10. The system according to claim 6, wherein the temperature control device comprises a temperature sensor, which is a contact temperature sensor and/or a non-contact temperature sensor, wherein,
the contact temperature sensor can be arranged at any one or more of the following positions: the first reaction vessel interior, the side wall of the first reaction vessel, the second reaction vessel interior, the side wall of the second reaction vessel, the third reaction vessel interior, the side wall of the third reaction vessel, the fourth reaction vessel interior, and the side wall of the fourth reaction vessel;
the non-contact temperature sensor is arranged at a distance from the first reaction vessel, and/or the second reaction vessel, and/or the third reaction vessel, and/or the fourth reaction vessel.
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