CN113105364B - Method and system for producing isocyanates - Google Patents

Method and system for producing isocyanates Download PDF

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Publication number
CN113105364B
CN113105364B CN202110377999.1A CN202110377999A CN113105364B CN 113105364 B CN113105364 B CN 113105364B CN 202110377999 A CN202110377999 A CN 202110377999A CN 113105364 B CN113105364 B CN 113105364B
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reaction
reaction vessel
phosgene
temperature
container
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CN113105364A (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

Abstract

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

Description

Method and system for producing isocyanates
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 isocyanates, aromatic isocyanates, unsaturated isocyanates, halogenated isocyanates, thioisocyanates, phosphorous-containing isocyanates, inorganic isocyanates, blocked isocyanates, and the like. Because the polyurethane has highly unsaturated isocyanate groups, the polyurethane has high chemical activity and can generate important chemical reaction with various substances, so the polyurethane can be widely applied to the fields of polyurethane, polyurethane urea and polyurea, polymer modification, organic synthesis reagents, agriculture, medicine and the like.
The principle of preparing isocyanates using 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 the gasified amine with gaseous phosgene to prepare isocyanate, and is not applicable to heat sensitive amine because of the high temperature gasification of the amine, and urea byproducts are easy to generate because of the high gas phase reaction speed. A typical liquid phase process involves three main chemical reactions, the first reaction being the reaction of an amine with phosgene to form carbamoyl chloride and carbamoyl chloride amine hydrochloride, the second reaction being the continued reaction of carbamoyl chloride amine hydrochloride with phosgene to form carbamoyl chloride, and the third reaction being the further reaction of carbamoyl chloride to form isocyanate and hydrogen chloride.
When the liquid phase method of phosgene is actually used for producing isocyanate, the ratio of phosgene to amine (namely, excess phosgene) is often required to be increased to increase the yield of isocyanate, which leads to the requirement of a large amount of phosgene in the reaction process, and increases the production cost, the safety cost and the tail gas pollution environmental treatment cost. Thus, there is a need to improve the isocyanate preparation process and reduce 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 demand 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 container at the temperature of minus 30 ℃ to 90 ℃ to obtain a first reaction product;
(b) Transferring the first reaction product obtained in the step (a) into a second reaction container, mixing with phosgene, and performing 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 with phosgene, and performing a third reaction in the third reaction container at a 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 with phosgene, and performing a fourth reaction in the fourth reaction container at a certain constant temperature between 120 and 300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein 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); 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 was not completely reacted in step (a); the off-gas of the third reaction vessel in step (c) comprises hydrogen chloride and unreacted complete phosgene in step (c), and optionally, unreacted complete phosgene in step (a), unreacted complete phosgene in step (d); and/or the off-gas of the fourth reaction vessel in step (d) comprises hydrogen chloride and unreacted complete 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 greater. 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 an intermediate carbamyl chloride hydrochloride, and optionally, one or more selected from the group consisting of: carbamoyl chloride, unreacted amine and phosgene in step (a).
In certain embodiments, the second reaction product comprises carbamoyl chloride and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride hydrochloride and phosgene in step (b).
In certain embodiments, the third reaction product comprises an isocyanate and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamoyl chloride hydrochloride in step (b), hydrogen chloride and phosgene, and unreacted carbamoyl chloride 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, unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride hydrochloride in step (b), hydrogen chloride and phosgene, unreacted carbamoyl chloride and phosgene in step (c), and unreacted phosgene in step (d).
In certain embodiments, prior to step (a), a solvent for the reactant amine is charged into the first reaction vessel and cooled to 0-10 ℃ under nitrogen protection.
In certain embodiments, the phosgene in step (b) is derived entirely from the off-gas of the fourth reaction vessel in step (d), and/or the phosgene in step (c) is derived entirely from the off-gas of the first reaction vessel in step (a); alternatively, the phosgene in step (b) is derived entirely from the offgas of the third reaction vessel in step (c), and/or the phosgene in step (c) is derived entirely from the offgas of the first reaction vessel in step (a) and/or the offgas of the fourth reaction vessel in step (d).
In certain embodiments, the flow rates of the reactant amine and phosgene are adjusted using an amine metering pump and a phosgene metering pump, respectively, of the first reaction vessel such that the reactant amine and phosgene are added to the first reaction vessel at a constant rate for reaction.
In certain embodiments, the first reaction described in step (a) is conducted in two temperature ranges, respectively, wherein the reaction temperature in the first stage is maintained at 30-50 ℃ and the reaction temperature in the second stage is raised 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 from 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 purifying device for rectification to obtain purified isocyanate.
In certain embodiments, the reactions of each step are carried out under atmospheric conditions.
In certain embodiments, phosgene is used in the first reaction vessel in a stoichiometric excess of 0% to 150% over theoretical based on the amine groups of the reactant amine.
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 ) n Wherein 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 groups: ethylamine, butylamine, pentylene diamine, hexamethylenediamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 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: diphenylmethylene diisocyanate as pure isomer or as a mixture of isomers, toluene diisocyanate as 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, t-butyl isocyanate, pentyl isocyanate (e.g., pentanediol diisocyanate), t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexanediisocyanate), 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 inlet, a phosgene feed inlet, and a reactant amine feed inlet; 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 quantity of reaction sample from the first reaction vessel; the second, third and fourth reaction vessels 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 vessels, respectively; a sampling port configured to operably withdraw a quantity of reaction sample from the second, third, or fourth reaction vessel; wherein the temperature control device is configured to selectively adjust the temperatures of the first, second, third, and fourth reaction vessels to predetermined values; wherein the vent of the first reaction container is selectively communicated with the emergency discharging device, and the discharge port of the first reaction container is selectively communicated with the discharge port of the second reaction container; the vent of the second reaction container is selectively communicated with the emergency discharging device, and the discharge port of the second reaction container is selectively communicated with the discharge port of the third reaction container; the vent of the third reaction container is selectively communicated with the emergency discharging device, and the discharge port of the third reaction container is selectively communicated with the discharge port of the fourth reaction container; the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and the vent of the first reaction vessel is in selective communication with the third reaction vessel, and the vent of the fourth reaction vessel is in selective communication with 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 third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the second reaction container.
In certain embodiments, the vent gas outlet of the first reaction vessel is in selective communication with the phosgene feed inlet of the third reaction vessel, and the vent gas outlet 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 off-gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its off-gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its off-gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its off-gas discharge.
In certain embodiments, 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 disposed at any one or more of the following positions: the first reaction vessel interior, the side wall of the first reaction vessel interior, the second reaction vessel interior, the side wall of the second reaction vessel interior, the third reaction vessel interior, the side wall of the third reaction vessel interior, the fourth reaction vessel interior, the side wall of the fourth reaction vessel; the non-contact temperature sensor is spaced apart from the first reaction vessel, and/or the second reaction vessel, and/or the third reaction vessel, and/or the fourth reaction vessel.
In certain 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 to exchange heat 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, fourth reaction vessels are selected from the group consisting of: carbon steel reaction kettle, stainless steel reaction kettle, enamel reaction kettle and steel lining reaction kettle. In certain embodiments, the first, second, third and fourth reaction vessels have viewing holes on the sidewalls thereof for visual inspection of the interiors of the first, second, third and fourth reaction vessels.
In certain embodiments, the system further comprises one or more of the following: stirring subassembly, measurement pumping mechanism, tail gas processing apparatus and purification device. The stirring assembly may be disposed within the first, second, third, and/or fourth reaction vessels. In certain embodiments, the stirring assembly includes a stirring shaft configured to operably effect one or more of the following motions, and a plurality of blades extending laterally outward from the stirring shaft: 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 port, phosgene feed port, reactant amine feed port of the first reaction vessel, and phosgene feed ports 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 directly applied to the third reaction vessel and the off-gas treatment device of the fourth reaction vessel is directly applied 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 directly applied to the third reaction vessel, and the off-gas treatment device of the third reaction vessel is directly applied 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 port of the first reaction vessel and the discharge port of the second reaction vessel, the first transfer pump being 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 which is communicated with the discharge port of the first reaction container and the discharge port of the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline.
In certain embodiments, a second transfer pump is disposed between the discharge port of the second reaction vessel and the discharge port of the third reaction vessel, the second transfer pump being operable to pump 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 which is communicated with the discharge port of the second reaction container and the discharge port of the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline.
In certain embodiments, a third transfer pump is disposed between the discharge port of the third reaction vessel and the discharge port of the fourth reaction vessel, the third transfer pump being operable to pump 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 conversion observation window is arranged on a pipeline which is communicated with the discharge port of the third reaction container and the discharge port of the fourth reaction container, and the material conversion observation window is configured to be used for visually observing the inside 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 being operable to pump off-gas of 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 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 inside 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 being operable to pump off-gas of 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 which is used for communicating the tail gas treatment device of the fourth reaction container and the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside 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 being operable to pump off-gas of 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 which is communicated with the tail gas treatment device of the fourth reaction container and the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside 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 being operable to pump off-gas of 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 which is communicated with the tail gas treatment device of the third reaction container and the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline.
In certain embodiments, a first thermostat is provided upstream of the phosgene feed port of the first reaction vessel through which phosgene may optionally enter 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 port of the second reaction vessel or the first attemperator.
In certain embodiments, a second attemperator is provided upstream of the phosgene feed port of the second reaction vessel through which phosgene may optionally enter the second reaction vessel. In certain embodiments, 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.
In certain embodiments, a third attemperator is provided upstream of the phosgene feed port of the third reaction vessel through which phosgene may optionally enter 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 provided upstream of the phosgene feed port of the fourth reaction vessel through which phosgene may optionally enter 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 a fourth reaction vessel.
By the method and the system for preparing the isocyanate, the requirement for phosgene in the preparation process of the isocyanate can be remarkably 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 and there may be cases where details are simplified, summarized and omitted, so those skilled in the art will recognize that this section is merely illustrative 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-mentioned and other features of the present application will be 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 present application and are therefore not to be considered limiting of its scope. The contents of the present application will be more specifically and more specifically described 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 inlet, 111c, 111 d-tail gas discharge outlet, 112a, 112 b-phosgene feed inlet, 113-reactant amine feed inlet, 120-discharge outlet, 140-vent, 150-sampling port, 160-observation hole, 170-stirring assembly, 171-stirring shaft, 172-blade;
200-second reaction vessel: 211a, 211 b-tail gas discharge ports, 212a, 212 b-phosgene feed ports, 220-discharge ports, 240-vent ports, 250-sampling ports, 260-observation holes, 270-stirring assemblies, 271-stirring shafts and 272-blades;
300-third reaction vessel: 311a, 311 b-tail gas discharge ports, 312a, 312 b-phosgene feed ports, 320-discharge ports, 340-vent ports, 350-sampling ports, 360-observation holes, 370-stirring components, 371-stirring shafts and 372-blades;
400-fourth reaction vessel: 411a, 411 b-exhaust gas discharge port, 412a, 412 b-phosgene feed port, 420-discharge port, 440-vent port, 450-sampling port, 460-observation hole, 470-stirring assembly, 471-stirring shaft, 472-blade;
500-temperature control device: 510. 520, 530, 540-heat exchange means;
610. 620, 630-material transferring observation windows;
710-first precooler, 720-second precooler, 730-third precooler, 740-fourth precooler;
810. 820, 830, 840-an exhaust gas treatment device; 850-purifying device;
910-first attemperator, 920-second attemperator, 930-third attemperator, 940-fourth attemperator;
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 transfer pump, 290-second transfer pump, 390-third transfer pump, 490-fourth transfer pump
Detailed Description
The illustrative embodiments described in the detailed description, drawings, and claims are not meant 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 readily understood that the aspects of the present application, as generally described herein, and illustrated in the figures, could be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated as part of this application.
1.Process for preparing 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 container at the temperature of minus 30 ℃ to 90 ℃ to obtain a first reaction product;
(b) Transferring the first reaction product obtained in the step (a) into a second reaction container, mixing with phosgene, and performing 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 with phosgene, and performing a third reaction in the third reaction container at a 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 with phosgene, and performing a fourth reaction in the fourth reaction container at a certain constant temperature between 120 and 300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein 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); 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, phosphorous-containing isocyanates, inorganic isocyanates, blocked isocyanates, and the like. In certain embodiments, "isocyanate" in the present application 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 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, pentyl isocyanate, t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, and the like. In certain embodiments, the isocyanate in the present application is selected from the group consisting of: pentanediisocyanate, hexanediisocyanate, p-phenylene diisocyanate, toluene diisocyanate.
The steps (a), (b), (c) and (d) of the isocyanate production method described herein are described in detail below, respectively.
1.1Step (a)
In step (a) of the present application, the reactant amine and phosgene are mixed and a first reaction is carried out in a first reaction vessel at a temperature of-30 ℃ to 90 ℃ to obtain a first reaction product.
Isocyanates are generally prepared by reacting amines with phosgene. The reaction of amine with phosgene is usually carried out in stages. First, carbamoyl chloride (RNHCOCl) is formed from amine and phosgene at low temperature, which is subsequently converted to the corresponding isocyanate (R-n=c=o) at elevated temperature, with hydrogen chloride being eliminated in both steps.
In the present application, "reactant amine" means that the starting material for the preparation of the isocyanate contains an amino group (-NH) 2 ) A compound of a group. For example, in certain embodiments, the reactant amine has the formula R (NH 2 ) n Wherein n is 1, 2 or 3, and r is an aliphatic, alicyclic or aromatic hydrocarbon group having 2-10 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 NH 2 A group. In certain embodiments, the reactant amine is a diamine, i.e., contains 2 NH' s 2 A group. In certain embodiments, the reactant amine is selected from one of the following groupsOne or more of: ethylamine, butylamine, pentylene diamine, hexamethylenediamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 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 groups: pentanediamine (e.g., 1, 5-dipentylamine), hexamethylenediamine (e.g., 1, 6-hexamethylenediamine), p-phenylenediamine, toluenediamine.
The first reaction carried out in the first reaction vessel of step (a) is the reaction of reactant 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 carbamyl chloride amine hydrochloride and in some cases, the first reaction product further comprises unreacted amine and phosgene in step (a). In some cases, the first reaction product further comprises carbamoyl chloride.
Taking pentylene diamine and phosgene as starting materials for example, the reaction carried out in the first reaction vessel is as follows:
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 30-50 ℃ (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 raised to 50-90 ℃ (e.g., 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃).
In certain embodiments, prior to step (a), a solvent for the reactant amine is charged into the first reaction vessel and cooled to 0-10deg.C (e.g., 0deg.C, 1deg.C, 2deg.C, 3deg.C, 4deg.C, 5deg.C, 6deg.C, 7deg.C, 8deg.C, 9deg.C, 10deg.C) 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 reactant amine is preferably o-dichlorobenzene or chlorobenzene as the solvent.
In the preparation of isocyanates, it is often necessary to add a large excess of phosgene, since, in the case of insufficient phosgene concentrations, the isocyanate formed forms instead with the excess amine urea or other high-viscosity solid by-products. In certain embodiments, the molar ratio of reactant amine to total phosgene used throughout the reaction, e.g., in step (a), step (b), step (c), and step (d), is from 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 foregoing values). In certain embodiments, phosgene is used in 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 in the first reaction vessel. Thus, the off-gas of the first reaction vessel in step (a) comprises unreacted complete phosgene in step (a), e.g. a stoichiometric excess of those phosgene. In certain embodiments, the phosgene content (w/w) in the off-gas of the first reaction vessel in step (a) is 90% or greater (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 an amine metering pump and a phosgene metering pump, respectively, of the first reaction vessel such that the reactant amine and phosgene are added to the first reaction vessel at a constant rate for reaction. For example, reactant amine is added to the first reaction vessel at a constant rate of 5-7kg/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 above), and 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 above). 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 amount of feed and ensures continuous production of isocyanate and yields of isocyanate.
1.2Step (b)
In step (b) of the present application, the first reaction product obtained in 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 to 200 ℃ to obtain a second reaction product.
In certain embodiments, the temperature in the second reaction vessel is maintained between 90-200deg.C (e.g., 90-100deg.C, 90-110deg.C, 90-120deg.C, 90-130deg.C, 90-140 deg.C, 90-150deg.C, 90-160 deg.C, 90-170 deg.C, 90-180 deg.C, 90-190 deg.C, 160-170 deg.C, 150-170 deg.C, 140-170 deg.C, 130-170 deg.C, 120-170 deg.C, 110-170 deg.C, 100-110 deg.C, 100-120 deg.C, 100-130 deg.C). 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, in certain instances, the second reaction product further comprises one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride hydrochloride and phosgene in step (b).
Taking pentylene diamine and phosgene as starting materials for example, the reaction mainly carried out in the second reaction vessel is as follows:
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 hydrogen chloride content (w/w) in the off-gas of the second reaction vessel is 60% or higher (e.g., 65%, 70%, 75%, 80%, 85%) and the phosgene content (w/w) is 40% or lower (e.g., 35%, 30%, 25%, 20%, 15%, 10%).
1.3Step (c)
In step (c) of the present application, the second reaction product obtained in 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 to 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 any range between two or more 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 an isocyanate and hydrogen chloride, and in certain instances, the third reaction product further comprises one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamoyl chloride hydrochloride in step (b), hydrogen chloride and phosgene, and unreacted carbamoyl chloride and phosgene in step (c).
Taking as an example the initial reaction starting materials of pentylene diamine and phosgene, the reactions carried out in the third reaction vessel include, but are not limited to, the following reactions:
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 in the off-gas of the third reaction vessel is 40% or greater (e.g., 45%, 50%, 55%, 60%, 65%). In certain embodiments, the phosgene content in 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, the third reaction product obtained in step (c) is transferred into a fourth reaction vessel, mixed with phosgene, and subjected to a fourth reaction in the fourth reaction vessel at a certain constant temperature between 120 and 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, for example, a constant temperature between 120 and 300 ℃ (e.g., 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, 200 ℃, 210 ℃, 220 ℃, 230 ℃, 240 ℃, 250 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃, or any 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, unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride amine hydrochloride and phosgene in step (b), unreacted carbamoyl chloride and phosgene in step (c), and unreacted phosgene in step (d).
Taking as an example the reaction of pentylene diamine and phosgene as starting reaction materials, the reaction performed in the fourth reaction vessel includes, but is not limited to, the following reactions:
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 byproducts. 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) in 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 this application, another advantage of providing 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 components in the fourth reaction vessel are relatively pure (the main component is isocyanate), and even if a very small amount of indissolvable crystals (carbamyl chloride amine hydrochloride) are dispersed in isocyanate, a large amount of phosgene is introduced to react the crystals to generate isocyanate, thereby greatly reducing the generation of byproducts and improving the yield of isocyanate.
In certain embodiments, the methods of preparing isocyanates described herein further comprise step (e) of transferring the fourth reaction product obtained in step (d) into a purification device for rectification to obtain purified isocyanates. For the avoidance of doubt, step (e) is not an essential step in the process for the preparation of isocyanates described herein, and the purity of the isocyanate obtained in step (d) is already sufficiently high, for example up to 90% or more.
In certain embodiments, each step in the process for the preparation of isocyanates described herein is carried out under atmospheric conditions.
1.5Phosgene circulation sleeve
The inventors of the present application selected the optimal reaction conditions for the preparation of isocyanate by splitting the isocyanate preparation 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, to ensure the yield of isocyanate, a large excess of phosgene is often required to be added during 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, thereby achieving the purposes of recycling phosgene and reducing production cost.
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 the off-gas of the fourth reaction vessel described in step (d). In certain embodiments, the phosgene described in step (b) is derived entirely 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 in step (d) is insufficient to react with the intermediate carbamoyl chloride hydrochloride to completely convert it to carbamoyl chloride, fresh phosgene may be additionally fed so that the second reaction is completed.
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 described in step (a). In certain embodiments, the phosgene described in step (c) is derived entirely from the off-gas of the first reaction vessel described in step (a). If there is insufficient phosgene in the off-gas from the first reaction vessel in step (a), fresh phosgene may additionally be fed so that the third reaction is completed.
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, the phosgene in step (b) is derived entirely from the off-gas of the fourth reaction vessel in step (d), and the phosgene in step (c) is derived entirely 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 the off-gas of the third reaction vessel described in step (c). In certain embodiments, the phosgene described in step (b) is derived entirely from the off-gas of the third reaction vessel described in step (c). If there is insufficient phosgene in the off-gas from the third reaction vessel in step (c), fresh phosgene may additionally be fed so that the second reaction is complete.
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 described in step (a) and/or the off-gas of the fourth reaction vessel described in step (d). 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) and/or the off-gas of the fourth reaction vessel described in step (d). If there is insufficient phosgene in the offgas from the first reaction vessel in step (a) and in the offgas from the fourth reaction vessel in step (d), fresh phosgene may additionally be fed in, so that the third reaction is completed.
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, the phosgene in step (b) is derived entirely from the off-gas of the third reaction vessel in step (c), and the phosgene in step (c) is derived entirely from the off-gas of the first reaction vessel in step (a) and the off-gas of the fourth reaction vessel in step (d).
Compared with the traditional method, the preparation method of the isocyanate can reduce the use amount of phosgene by 30-70%, thereby greatly reducing the production cost and obviously reducing the pollution of tail gas to the environment.
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 from each reaction vessel. The features common to fig. 1 and 2 are described below by taking fig. 1 as an example.
As shown in fig. 1, the system includes: the device comprises a first reaction container, a second reaction container, a third reaction container, a fourth reaction container 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 port, a vent and a sampling port. The temperature control device is configured to control the temperatures in the first, second, third, and fourth reaction vessels to produce isocyanate.
In certain embodiments, the feed inlet of the first reaction vessel may be further divided into a solvent feed inlet, a phosgene feed inlet, a reactant amine feed inlet, etc., depending on the type of feed. In certain embodiments, the feed inlet of the second, third, fourth reaction vessels may be further divided into phosgene feed inlet, etc., depending on the type of feed. It is contemplated that the number of each of the feed port, the exhaust port, the discharge port, the vent port, and the sampling port in the embodiment shown in fig. 1 is not limited to one, and a plurality of feed ports, exhaust ports, discharge ports, vents, or sampling ports may be provided as needed. In this application, a feed port, a vent port, a discharge port, a vent port, a sampling port are functionally defined openings, but one or more of the feed port, vent port, discharge port, vent port, sampling port may be physically multiplexed by providing corresponding switching means to reduce the number of openings, such as by providing the same opening on a first, second, third, or fourth reaction vessel to operatively input or expel reactants within 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 each stage of preparing isocyanate. For this purpose, the outlet openings provided in the individual reaction vessels are in selective communication with one another. For example, the discharge port of the first reaction vessel is in selective communication with the discharge port of the second reaction vessel, the discharge port of the second reaction vessel is in selective communication with the discharge port of the third reaction vessel, and the discharge port of the third reaction vessel is in selective communication with the discharge port of the fourth reaction vessel. In some embodiments, the discharge ports of each reaction vessel are located in the lower portion of the corresponding reaction vessel. In emergency situations, for example, when the pressure in the reaction vessel rises sharply or the liquid boils sharply to reach a certain threshold value, part of the gas can be decompressed or transferred to the emergency discharging device by enabling the vent of the reaction vessel to be communicated with the emergency discharging device, and/or part of the liquid can be decompressed or transferred to the emergency discharging device by enabling the discharge port of the reaction vessel to be selectively communicated with the emergency discharging device, so that the reaction vessel is prevented from being damaged, 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 a line connecting the vent of the first reaction vessel and the emergency discharge device. The selective communication between the discharge opening of the first reaction vessel and the emergency discharge device may also be achieved, for example, by providing a pressure relief valve in the line connecting the discharge opening of the first reaction vessel and the emergency discharge device. The discharge ports of the individual reaction vessels are in selective communication with one another, for example by means of switching valves, for the controlled transfer of material.
As described above, the reaction conditions in each stage of the phosgene liquid phase method for preparing isocyanate have a large temperature span, and it is difficult to perform a reaction test in the same reaction vessel in a large temperature span. 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, wherein 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 the isocyanate is performed in four stages. Correspondingly, the temperature regulating range of the first reaction container is-30-90 ℃, the temperature regulating range of the second reaction container is 90-200 ℃, the temperature regulating range of the third reaction container is 120-250 ℃, and the temperature regulating range of the fourth reaction container is 120-300 ℃. The first stage reaction utilizes the reaction of an amine and phosgene to form a suspension of carbamoyl chloride and an intermediate carbamoyl chloride amine hydrochloride, which is carried out in a first reaction vessel. Solvent, phosgene and amine are first introduced into the first reaction vessel through feed ports (i.e., solvent feed port, phosgene feed port, reactant amine feed port). Then gradually increasing the temperature T of the first reaction vessel by a temperature control device 11-1 (-30℃≤T 11-1 At a temperature of 90℃or lower, for example, gradually increasing the temperature and maintaining the temperature at 0 to 90 ℃. And then the first reaction product in the first reaction container is input into the second reaction container through a discharge hole of the first reaction product to carry out the reaction of the second stage. In the second stage reaction, the suspension obtained from the first stage reaction is reacted to form carbamoyl chloride. Similar to the operation of the first reaction vessel, the temperature T of the second reaction vessel is gradually increased by the temperature control means 11-2 (90℃≤T 11-2 200℃or lower, for example from 90℃to 170℃gradually, in order to bring about the reactionThe intermediate carbamyl chloride hydrochloride in the suspension obtained from the first stage reaction is completely reacted to generate carbamyl chloride. And 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 reacted to form isocyanate and hydrogen chloride. Similar to the operation of the first reaction vessel, the temperature T of the third reaction vessel is gradually increased by the temperature control means 11-3 (120℃≤T 11-2 And 250 ℃ or less, for example, gradually increasing from 170 ℃ to 180 ℃. And then the third reaction product in the third reaction vessel is fed into the fourth reaction vessel through the discharge port thereof so as to carry out the reaction of the fourth stage. In the fourth reaction stage, the carbamoyl chloride in the third reaction product is fully reacted to form isocyanate. The temperature of the fourth reaction vessel is regulated to T by a temperature control device 11-4 (120℃≤T 11-2 At a temperature of 300 ℃ or less, for example 180 ℃) and maintaining a constant temperature for the reaction. In certain embodiments, T 11-1 ≤T 11-2 ≤T 11-3 ≤T 11-4 。
In certain embodiments, the temperature adjustment ranges of the first, second, third and fourth reaction vessels may partially overlap each other, for example, the temperature adjustment range of the first reaction vessel is-30 to 90 ℃, the temperature adjustment range of the second reaction vessel is 80 to 180 ℃, the temperature adjustment range of the third reaction vessel is 160 to 190 ℃, and the temperature adjustment range of the fourth reaction vessel is 170 to 300 ℃. 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 discharge port of the first reaction vessel is selectively communicated with the third reaction vessel, and the off-gas discharge port of the fourth reaction vessel is selectively communicated with the discharge port of the second reaction vessel. Although in fig. 1 the connection port through which the off-gas discharge port of the first reaction vessel communicates with the third reaction vessel is not the feed port of the third reaction vessel (e.g., the connection port is another opening in the third reaction vessel than the feed port), it is understood that the off-gas discharge port of the first reaction vessel may (and preferably is) selectively communicate with the feed port of the third reaction vessel. Similarly, while in fig. 1 the connection port of the fourth reaction vessel through which the off-gas discharge port 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 discharge port of the fourth reaction vessel may (and preferably is) selectively in communication with the feed port of the second reaction vessel.
In fig. 2, the offgas discharge of the first reaction vessel, the offgas discharge of the fourth reaction vessel are each selectively communicated with the third reaction vessel, and the offgas discharge of the third reaction vessel is selectively communicated with the second reaction vessel. While in fig. 2 the connection port through which the off-gas discharge port of the first reaction vessel, the off-gas discharge port of the fourth reaction vessel communicate with the third reaction vessel is not the feed port of the third reaction vessel (e.g., other opening in the third reaction vessel than the feed port at the time of connection), it is understood that the off-gas discharge port of the first reaction vessel, the off-gas discharge port of the fourth reaction vessel may (and preferably are) selectively in communication with the feed port of the third reaction vessel. Similarly, while in fig. 2 the connection port of the third reaction vessel to 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 vent gas discharge port of the fourth reaction vessel may (and preferably is) in selective communication with the feed port of the second reaction vessel.
Fig. 3 shows a schematic block diagram of a system 10 for preparing isocyanate according to one embodiment of the present application, and fig. 4 shows a schematic block diagram of a system 20 for preparing isocyanate according to another embodiment of the present application. The difference between system 10 and system 20 is the different ways in which the off-gas from each reactor vessel is used. The 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 reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400 respectively contain reactants of each reaction stage and allow the reactants of each stage 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, and for example, the second reaction vessel 200 may include 2 or more (e.g., 2, 3, 4, 5, or more) reaction vessels, and the third reaction vessel 300 may include 2 or more (e.g., 2, 3, 4, 5, or more) reaction vessels. Without being bound by any theory, it is believed that the number of stages of tail gas application increases as the number of reaction vessels increases, further reducing the amount of phosgene used.
In some embodiments, the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 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, the fourth reaction vessel 400 may also be configured in any other shape suitable for performing a reaction, such as spherical, hemispherical, frustoconical, and the like. 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 have the same or different structures. 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, tail gas discharge ports 111c,111d, phosgene feed ports 112a,112b, reactant amine feed port 113. The solvent, phosgene, amine for the phosgene liquid phase process isocyanate may be fed into the first reaction vessel 100 through the corresponding solvent feed ports 111a,111b, phosgene feed ports 112a,112b, 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 comprises a discharge port 120, a vent 140, and a sampling port 150.
The second reaction vessel 200 includes: the exhaust gas discharge ports 211a,211b and the phosgene feed ports 212a,212b are used for discharging the exhaust gas of the second reaction vessel 200 and replenishing phosgene into the second reaction vessel 200 according to the reaction requirement, respectively. The second reaction vessel 200 further includes: discharge port 220, vent 240, sampling port 250.
The third reaction vessel 300 includes: the exhaust gas discharge ports 311a and 311b and the phosgene feed ports 312a and 312b are used for discharging the exhaust gas of the third reaction vessel 300 and supplementing phosgene into the third reaction vessel 300 according to the reaction requirement, respectively. The third reaction vessel 300 further comprises: discharge port 320, vent 340, sampling port 350.
The fourth reaction vessel 400 includes: the exhaust gas discharge ports 411a,411b and the phosgene feed ports 412a,412b are used for discharging the exhaust gas of the fourth reaction vessel 400 and replenishing phosgene into the fourth reaction vessel 400 according to the reaction requirement, respectively. The fourth reaction vessel 400 further includes: discharge port 420, vent 440, sampling port 450.
The vents 140, 240, 340, 440 are in communication with an emergency discharge device, optionally 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, respectively. The operator can operate the corresponding switching valve to extract a certain amount of reaction sample from the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, or the fourth reaction vessel 400 via the sampling port 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 port 140 of the first reaction vessel 100 is selectively communicated with the emergency discharge 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 discharge device. Similarly, the discharge port 320 of the third reaction vessel 300 and the discharge port 420 of the fourth reaction vessel 400 are selectively communicated, and the vent 340 of the third reaction vessel 300 is selectively communicated with the emergency discharge device. Similarly, vent 440 of 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 port 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 fourth reaction vessel outlet 420 is also in selective communication with an emergency discharge device. The discharge ports of the individual reaction vessels are 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 optional communication is achieved, for example, by a manually operated switching valve, or by an automatic operation of a safety valve which is arranged to automatically open to release pressure from one reaction vessel to the other when the pressure on one side of the valve exceeds a threshold value.
In this application, each reaction vessel may use a different emergency discharge device, or may share one emergency discharge device. For each reaction vessel, the vent and the discharge port may be connected to the same emergency discharge device, or may be connected to different emergency discharge devices.
In the example shown in fig. 3, the solvent feed ports 111a,111b, the off-gas discharge ports 111c,111d are provided at the top of the first reaction vessel 100, but in some embodiments, the solvent feed ports 111a,111b, the off-gas discharge ports 111c,111d may be provided at other locations, such as on the side walls of the reaction vessel, etc. 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 of the fourth reaction vessel 400. 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 disposed elsewhere.
In addition, although the solvent feed port 111a and the off-gas discharge port 111c on the first reaction vessel 100 share the same opening provided on the first reaction vessel 100 and the solvent feed port 111b and the off-gas discharge port 111d share the same opening provided on the first reaction vessel 100 in the example shown in fig. 3, in some embodiments, the solvent feed port 111a and the off-gas discharge port 111c may be openings provided on the first reaction vessel 100, respectively, and the solvent feed port 111b and the off-gas discharge port 111d may also be openings provided on 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 on the first reaction vessel 100 share the same opening provided on the first reaction vessel 100, the discharge port 220, the phosgene feed port 212a, and the sampling port 250 on the second reaction vessel 200 share the same opening provided on the second reaction vessel 200, and the discharge port 320, the phosgene feed port 312a, and the sampling port 350 on the third reaction vessel 300 share the same opening provided on the third reaction vessel 300, and the discharge port 420, the phosgene feed port 412a, and the sampling port 450 on the fourth reaction vessel 400 share the same opening provided on the fourth reaction vessel 400. However, in some embodiments, the discharge port 120 and the sampling port 150 may be openings respectively provided on the first reaction vessel 100, the discharge port 220 and the sampling port 250 may be openings respectively provided on the second reaction vessel 200, the discharge port 320 and the sampling port 350 may be openings respectively provided on the third reaction vessel 300, and the discharge port 420 and the sampling port 450 may be openings respectively provided on the fourth reaction vessel 400. Conversely, the openings shown in FIG. 3 as being provided separately on the reaction vessel may in other embodiments be provided to share the same opening on the reaction vessel. For example, in certain embodiments, reactant amine feed 113 and discharge 120 share the same opening provided on first reaction vessel 100. Hereinafter, "opening" may refer to one or more of solvent feed inlet 111a,111b, exhaust vent 111c,111d, phosgene feed inlet 112a,112b, reactant amine feed inlet 113, outlet 120, vent 140, sampling port 150, exhaust vent 211a,211b, phosgene feed inlet 212a,212b, outlet 220, vent 240, sampling port 250, exhaust vent 311a,311b, phosgene feed inlet 312a,312b, outlet 320, vent 340, sampling port 350, exhaust vent 411a,411b, phosgene feed inlet 412a,412b, outlet 420, vent 440, sampling port 450.
In some embodiments, an opening and closing member is provided at each opening for opening and closing the corresponding opening, the opening and closing member being movable between an open position and a closed position. In the open position, the opening is opened, allowing reactants, reaction products to enter and exit the reaction vessel; while in the closed position the opening is closed, thereby ensuring the tightness of the reaction vessel during the reaction, preventing leakage of reactants and/or reaction products from the reaction vessel. The opening and 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 inlets 111a,111b provided on the first reaction vessel 100, wherein a first precooler 710 is connected upstream of the solvent feed inlet 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, to which a third precooler 730 is connected upstream of the off-gas discharge port 311 b. The fourth reaction vessel 400 comprises two off-gas discharge ports 411a,411b, to which 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, third, and fourth precoolers 720, 730, 740 are used to regulate the temperature of the tail gas flowing therethrough. The precoolers can be independently selected from shell-and-tube precoolers, circulating heat exchange precoolers, refrigeration circulators, screw water chilling units, gas condensation systems and the like, for example, precoolers of tin-crown-free sub-constant temperature refrigeration technology Co. In some embodiments, only the first precooler 710 may be provided. In other embodiments, only the second precooler 720 may be provided. In other embodiments, only third precooler 730 may be provided. In other embodiments, only fourth precooler 740 may be provided.
In the embodiment shown in fig. 3, solvent optionally enters first reaction vessel 100 through a first precooler 710 via solvent feed port 111a or 111 b. When the solvent is not required to be pre-cooled or the first pre-cooler 710 is not required to be rinsed, the solvent is directly introduced into the first reaction vessel 100 through the solvent inlet 111a by controlling the opening and closing of the valve. When the solvent 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 solvent sequentially enters the first reaction vessel 100 through the first pre-cooler 710 and the solvent feed port 111b 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 off-gas discharge port 111c or 111d by the first precooler 710. When the off-gas is not required to be pre-cooled or the first pre-cooler 710 is not required to be flushed, the off-gas is directly discharged out of the first reaction vessel 100 through the off-gas discharge port 111c by controlling the opening and closing of the valve. When the tail gas needs to be pre-cooled or the residual reactant of the first precooler 710 needs to be flushed back into the first reaction container 100, the tail gas is discharged out of the first reaction container 100 through the tail gas discharge port 111d and the first precooler 710 by controlling the opening and closing of the valve.
Similarly, the off-gas of the second reaction vessel 200 may alternatively be discharged from the second reaction vessel 200 directly through the off-gas discharge port 211a or 211b, or sequentially discharged from the second reaction vessel 200 through the off-gas discharge port 211b and the second precooler 720. Similarly, the off-gas of the third reaction vessel 300 may alternatively be discharged out of the third reaction vessel 300 directly through the off-gas discharge port 311a or 311b, or sequentially discharged out of the third reaction vessel 300 through the off-gas discharge port 311b and the third precooler 730. Similarly, the off-gas of the fourth reaction vessel 400 may alternatively be discharged directly from the fourth reaction vessel 400 through the off-gas discharge port 411a or 411b, or sequentially discharged from the fourth reaction vessel 400 through the off-gas discharge port 411b and the fourth precooler 740.
By selectively pre-cooling the solvent entering the first reaction vessel and discharging the tail gas from the first, second, third or fourth reaction vessels, the temperature of the solvent or tail gas can be better adjusted, the reaction can be accelerated or the influence of the added solvent, the discharged tail gas and the tail gas to be recycled on the ongoing chemical reaction can be avoided.
Alternatively or additionally, during the reaction of the first reaction vessel 100, phosgene feed ports 112a, 112b are opened and the valve upstream of the first precooler 710 is closed, the gas mixture overflowing from the first reaction vessel 100 is circulated through the first precooler 710 for external circulation, condensed and returned to the first reaction vessel 100 again via solvent feed port 111a or 111 b. Similarly, during the reaction of the second reaction vessel 200, phosgene feed ports 212a, 212b are opened and the valve upstream of the second precooler 720 is closed, allowing the gas mixture overflowing from the second reaction vessel 200 to flow through the second precooler 720 for external circulation. Similarly, during the reaction of the third reaction vessel 300, phosgene feed ports 312a, 312b are opened and the valve upstream of the third precooler 730 is closed, allowing the gas mixture overflowing the third reaction vessel 300 to flow through the third precooler 730 for external circulation. Similarly, during the reaction of the fourth reaction vessel 400, phosgene feed ports 412a, 412b are opened and the valve upstream of the fourth precooler 740 is closed, allowing the gas mixture overflowing the fourth reaction vessel 400 to flow through the fourth precooler 740 for external circulation. In this way, the gas mixture generated in the reaction vessel can be condensed back into the reaction vessel, so that the reactants can be more fully utilized, 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 111b. In other embodiments, however, a single solvent feed may be provided on first reaction vessel 100, and the single opening may be selectively connected or disconnected upstream of the precooler, as desired. Similarly, in the embodiment shown in fig. 3, two off-gas discharge ports are provided on each of the first, second, third and fourth reaction vessels 100, 200, 300 and 400. In other embodiments, however, a single off-gas vent may be provided on the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and/or the fourth reaction vessel 400, and may be optionally connected or disconnected upstream of the single vent, depending on the actual needs.
In fig. 3, the first reaction vessel 100 includes two phosgene feed ports 112a,112b provided on the first reaction vessel 100, wherein a first temperature regulator 910 is connected upstream of the phosgene feed port 112b, and the phosgene feed port 112a multiplexes the same opening with the discharge port 120. The second reaction vessel 200 comprises two phosgene feed ports 212a,212b, a second thermostat 920 being connected upstream of the phosgene feed port 212b, the phosgene feed port 212a multiplexing the same opening as the discharge port 220. The third reaction vessel 300 includes two phosgene feed ports 312a,312b, a third attemperator 930 connected upstream of the phosgene feed port 312b, the phosgene feed port 312a multiplexing the same opening as the discharge port 320. The fourth reaction vessel 400 includes two phosgene feed ports 412a,412b, a fourth temperature regulator 940 being connected upstream of the phosgene feed port 412b, the phosgene feed port 412a multiplexing the same opening as the discharge port 420.
In certain embodiments, the first attemperator 910, the second attemperator 920, the third attemperator 930, and the fourth attemperator 940 are used to adjust the temperature of phosgene flowing therethrough, and the first attemperator 910, the second attemperator 920, the third attemperator 930, and the fourth attemperator 940 may be selected from shell-and-tube heat exchangers, circulating heat exchangers, and the like. In some embodiments, only the first thermostat 910 may be provided. In other embodiments, only the second attemperator 920 may be provided. In 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 first reaction vessel 100 through first attemperator 910 via phosgene feed-port 112 b. When the pre-temperature adjustment of the phosgene is not required, the phosgene is directly introduced into the first reaction vessel 100 through the phosgene feed port 112a by controlling the opening and closing of the valve. When it is necessary to pre-condition the phosgene, the opening and closing of the valve is controlled so that the phosgene sequentially enters the first reaction vessel 100 via the first attemperator 910 and the phosgene feed-in 112 b. Similarly, phosgene may alternatively enter second reaction vessel 200 directly through phosgene feed port 212a or sequentially through second attemperator 920 and phosgene feed port 212 b. Similarly, phosgene may alternatively enter third reaction vessel 300 directly through phosgene feed port 312a or enter third reaction vessel 300 sequentially through third attemperator 930 and phosgene feed port 312 b. Similarly, phosgene may alternatively enter fourth reaction vessel 400 directly through phosgene feed 412a or through fourth attemperator 940 and phosgene feed port 412b in sequence.
By selectively pre-conditioning the phosgene, the phosgene temperature can be better adjusted, reducing the effect of adding phosgene on the ongoing chemical reaction during the already ongoing reaction, and better controlling the state (liquid, gaseous, boiling) of the phosgene in the reaction vessel.
In the embodiment shown in fig. 3, the reactants in the first reaction vessel 100 may optionally enter the first temperature regulator 910 through the phosgene feed port 112a during the reaction, and enter the first reaction vessel 100 again through the phosgene feed port 112b after temperature regulation, so that the reactants in the reaction continuously circulate through the first temperature regulator 910, thereby increasing the mixing contact time of the reactant phosgene and improving the phosgene utilization rate. Similarly, the reactants in the second reaction vessel 200 can optionally enter the second temperature regulator 920 through the phosgene feed port 212a, and then enter the second reaction vessel 200 through the phosgene feed port 212b, so that the mixing contact time of the reactants and the phosgene is increased through external circulation, and the phosgene utilization rate is improved. Similarly, the reactants in the third reaction vessel 300 may optionally enter the third temperature regulator 930 through the phosgene feed port 312a and then enter the third reaction vessel 300 through the phosgene feed port 312b, increasing the mixing contact time of the reactants and phosgene through external circulation, improving the phosgene utilization. Similarly, the reactants in the fourth reaction vessel 400 may optionally enter the fourth temperature regulator 940 through the phosgene feed port 412a and then enter the fourth reaction vessel 400 through the phosgene feed port 412b, increasing the mixing contact time of the reactants and phosgene by external circulation, improving the phosgene utilization.
In the embodiment shown in fig. 3, the first attemperator 910 is configured as a heat exchanger type precooler that exchanges heat by the circulation of an aqueous glycol solution; the second attemperator 920, the third attemperator 930, and/or the fourth attemperator 940 are configured as heat exchanger-type preheaters that exchange heat through conduction oil circulation. In other embodiments, the first attemperator 910, the second attemperator 920, the third attemperator 930, and the fourth attemperator 940 may be selected from the group consisting of: electric heaters, refrigerators, heat exchangers (e.g., coil heat exchangers, plate heat exchangers, ring-groove heat exchangers, finned tube heat exchangers, plate 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 to adjust the temperatures of the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300 and the fourth reaction vessel 400 to predetermined values, respectively, for example, the temperature adjustment range of the first reaction vessel 100 is-30 to 90 ℃, the temperature adjustment range of the second reaction vessel 200 is 90 to 200 ℃, the temperature adjustment range of the third reaction vessel 300 is 120 to 250 ℃, and the temperature adjustment range of the fourth reaction vessel 400 is 120 to 300 ℃. In a preferred embodiment, the temperature adjustment range of the first reaction vessel 100 is between 0 and 90 ℃, the temperature adjustment range of the second reaction vessel 200 is between 90 and 170 ℃, the temperature adjustment range of the third reaction vessel 300 is between 170 and 180 ℃, and the temperature adjustment range of the fourth reaction vessel 400 is between 180 and 250 ℃.
The temperature control device 500 includes temperature sensors (not shown), heat exchange 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 in the above 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, which 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 measured values of the respective contact temperature sensors may be averaged by weighting as the temperature values of the respective reaction vessels.
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 containers 100, 200, 300 and/or 400 and spaced apart from the first, second, third and/or fourth reaction containers 100, 200, 300 and/or 400. The non-contact temperature sensor may be configured as an infrared temperature sensor, a radiation thermometer, or the like. The temperature sensor may be a commercially available one, for example, a temperature sensor selected from the group consisting of Fulush, ke En, and omega.
In some embodiments, a plurality of non-contact temperature sensors (e.g., 1, 2, 3, 4, etc.) may be provided, which may be provided 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 measured values of the respective contact temperature sensors may be averaged by weighting as the temperature values of the respective reaction vessels.
In the embodiment shown in fig. 3, the heat exchange means 510, 520, 530, 540 are jacketed circulating heat exchangers, wherein the heat exchange means 510 is attached to the side wall of the first reaction vessel 100, the heat exchange means 520 is attached to the side wall of the second reaction vessel 200, the heat exchange means 530 is attached to the side wall of the third reaction vessel 300, and the heat exchange means 540 is attached to the side wall of the fourth reaction vessel 400 to exchange heat with the reactants in the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300, and the fourth reaction vessel 400, respectively. The temperature ranges adjusted by heat exchange device 510, heat exchange device 520, heat exchange device 530, and heat exchange device 540 are not the same as each other. For example, the heat exchange device 510 may be adjustable to a temperature in the range of-30 to 90 ℃, the heat exchange device 520 may be adjustable to a temperature in the range of 90 to 200 ℃, the heat exchange device 530 may be adjustable to a temperature in the range of 120 to 250 ℃, and the heat exchange device 540 may be adjustable to a temperature in the range of 120 to 300 ℃. Those 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 other types of heat exchange devices, such as one of an electrothermal tube, a circulating heat exchange device (e.g., a tube heat exchanger, a plate heat exchanger, a ring groove heat exchanger, a finned tube heat exchanger, a plate 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, the heat exchange devices 510, 520, 530, 540 are configured as a circulating heat exchanger, wherein the heat exchange device 510 uses an aqueous glycol solution as the heat exchange liquid, and the heat exchange devices 520, 530, 540 use a heat transfer oil as the heat exchange liquid.
A temperature controller (not shown) is coupled to the temperature sensor and the heat exchanging devices 510, 520, 530, and 540, respectively, the temperature controller being configured to receive a measurement signal of the temperature sensor and operate the heat exchanging devices 510, 520, 530, and 540 according to the measurement signal. The operation of the temperature controller will be described below using 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 the preset temperature value with the current temperature value. If the comparison result is 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, the flow rate and the like of 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 is 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, the flow rate and the like of heat exchange liquid in the circulating heat exchange device are reduced. The temperature controller may be configured as various types of controllers that can be automatically controlled. In some embodiments, the temperature controller is a proportional-integral-derivative (PID) controller.
The materials of the first reaction vessel 100, the second reaction vessel 200, the third reaction vessel 300 and the fourth reaction vessel 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 that are suitable for use at smaller experimental scales.
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 kettles. Compared with a glass container, the reaction kettle has the advantages that the matched temperature control device of the industrial reaction kettle is more mature, and the reaction kettle can be conveniently transferred into experimental production after the 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 reaction kettle, stainless steel reaction kettle, enamel reaction kettle and steel lining reaction kettle.
In some embodiments, when the first, second, third and fourth reaction vessels 100, 200, 300 and 400 are reaction kettles, a viewing port 160 may be further provided on a side wall of the first reaction vessel 100, a viewing port 260 may be provided on a side wall of the second reaction vessel 200, a viewing port 360 may be provided on a side wall of the third reaction vessel 300, and a viewing port 460 may be provided on a side wall of the fourth reaction vessel 400. By observing the holes 160, 260, 360 and 460, the states inside 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 boils.
Because the reaction process of preparing isocyanate by the phosgene liquid phase method can generate slurry of carbamoyl chloride and hydrochloride of amine, the state is sticky, good stirring is needed to prevent byproducts from being generated, reactants are contacted more fully, and the reaction efficiency is improved. As shown in fig. 3, the first, second, third and fourth reaction containers 100, 200, 300 and 400 are provided with stirring assemblies 170, 270, 370 and 470, respectively, for stirring reactants inside the first, second, third and fourth reaction containers 100, 200, 300 and 400. Referring to fig. 3, the stirring assembly 170, 270, 370, 470 includes a stirring shaft 171, 271, 371, 471 and two blades 172, 272, 372, 472 extending laterally from the stirring shaft 171, 271, 371, 471 (i.e., in a direction intersecting the axis of the stirring shaft). In some embodiments, the stirring assemblies 170, 270, 370, 470 may also have only one blade extending laterally from the stirring shafts 171, 271, 371, 471. In other embodiments, the blending assemblies 170, 270, 370, 470 may have more blades extending laterally from the blending shafts 171, 271, 371, 471, e.g., 3, 4, 5, 6, 7, 8, etc. In certain embodiments, the stirring assemblies 170, 270, 370, and 470 may be any of an anchor stirrer, an anchor frame stirrer, or a straight blade stirrer.
In some embodiments, the system for preparing isocyanate may further comprise: a metering pumping mechanism disposed 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, for 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; for 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 pumping operation based on the amount of reactant flowing through each metering pump. By means of a metering pumping mechanism, the entry of the respective reactants (e.g. amine compound, phosgene) into the reaction vessel can be controlled accurately and quantitatively. The metering pump may be a combination of a flow meter and a pump, such as one of a rotameter, a positive displacement flow meter, an ultrasonic flow meter, and one of a positive displacement pump, an impeller or a jet pump.
In certain embodiments, the systems for preparing isocyanates herein further comprise a tail gas treatment device, e.g., the first reaction vessel 100 comprises a tail gas treatment device 810, the second reaction vessel 200 comprises a tail gas treatment device 820, the third reaction vessel 300 comprises a tail gas treatment device 830, and the fourth reaction vessel 400 comprises a tail gas treatment device 840. In the case of the phosgene-liquid-phase process for preparing isocyanates, the reaction off-gas is predominantly hydrogen chloride, which may also comprise a gaseous mixture of partially unreacted phosgene and other reaction products, which is environmentally polluting and toxic. Moreover, in the preparation of isocyanates, an excess of phosgene is usually introduced in order to increase the isocyanate yield, and thus a large portion (e.g., at least 90% or more) of the off-gas from some reaction vessels may be phosgene. If the excessive phosgene is directly used as tail gas to be discharged, 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 offgas discharge 111c,111d of the first reaction vessel 100 is directly applied to the third reaction vessel 300 through the offgas treatment apparatus 810, for example, in selective communication with the phosgene feed openings 312a,312b of the third reaction vessel 300, so that excess phosgene in the offgas of the first reaction vessel 100 is 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, in selective communication with the phosgene feed ports 212a,212b of the second reaction vessel 200, so that 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 vents 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., in selective communication with the phosgene feed ports 312a,312b of the third reaction vessel 300), and the off-gas vents 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., in selective 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., the hydrogen chloride content is 60% or greater (e.g., 65%, 70%, 75%, 80%, 85%), and the phosgene content is 40% or less (e.g., 35%, 30%, 25%, 20%, 15%, 10%). In certain embodiments, the off-gas of the third reaction vessel 300 is predominantly hydrogen chloride and phosgene, e.g., 40% or higher (e.g., 45%, 50%, 55%, 60%, 65%) and 60% or lower (e.g., 55%, 50%, 45%, 40%, 35%, 30%). The offgas of the second reaction vessel 200 and the third reaction vessel 300 is treated by offgas treatment apparatuses 820 and 830, respectively, and then discharged. In certain embodiments, the exhaust 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 offgas discharge opening 111c,111d of the first reaction vessel 100 is directly applied to the third reaction vessel 300 through the offgas treatment apparatus 810, and the offgas discharge opening 411a,411b of the fourth reaction vessel 400 is directly applied to the third reaction vessel 300 through the offgas treatment apparatus 840, for example, both of which are in selective communication with the phosgene feed openings 312a,312b of the third reaction vessel 300, so that excess phosgene in the offgas 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, in selective communication with the phosgene feed ports 212a,212b of the second reaction vessel 200, so that excess phosgene in the off-gas of the third reaction vessel 300 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., the hydrogen chloride content is 60% or greater (e.g., 65%, 70%, 75%, 80%, 85%), and the phosgene content is 40% or less (e.g., 35%, 30%, 25%, 20%, 15%, 10%). The offgas of the second reaction vessel 200 is treated by the offgas treatment apparatus 820 and then discharged. In certain embodiments, the exhaust 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 phosgene liquid phase process may further comprise a purification device 850 connected downstream of the fourth reaction vessel 400 for purifying the reaction product isocyanate (e.g., removing solvent or other impurities) such that the purity of the finally collected product isocyanate reaches a certain degree, e.g., higher than 90%. Purification apparatus 850 is, for example, a vacuum distillation column, through which the solvent in the reactants flowing therein can be removed by the temperature and pressure of the 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 outlet 220 of the second reaction vessel 200 and the outlet 320 of the third reaction vessel 300, the second transfer pump 290 being operable to pump a second reaction product between the outlet 220 of the second reaction vessel 200 and the outlet 320 of the third reaction vessel 300.
In certain embodiments, a third transfer pump 390 is disposed between the outlet 320 of the third reaction vessel 300 and the outlet 420 of the fourth reaction vessel 400, the third transfer pump 390 being operable to pump a third reaction product between the outlet 320 of the third reaction vessel 300 and the outlet 420 of the fourth reaction vessel 400.
In certain embodiments, a fourth transfer pump 490 is disposed between the outlet 420 of the fourth reaction vessel 400 and the purification apparatus 850, the fourth transfer pump 490 being operable to pump a fourth reaction product between the outlet 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 also 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 thermostat 910, the reactants in the first reaction vessel 100 are optionally pumped into the first thermostat 910 through the phosgene feed port 112a during the reaction by the first transfer pump 190, and then enter the first reaction vessel 100 again through the phosgene feed port 112b after being temperature-regulated, completing the external circulation, thereby 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 the second attemperator 920. Similarly, the second transfer pump 290 may pump the reaction product flowing from the phosgene feed port 212a through the second attemperator 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 products within the second reaction vessel 200 downstream, for example, to the third reaction vessel 300, etc.
In some embodiments shown in fig. 3 and 4, a third transfer pump 390 is also provided that is connected to the third attemperator 930. Similarly, third transfer pump 390 may pump the reaction product exiting phosgene feed port 312a through third attemperator 930, phosgene feed port 312b, and into 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, etc.
In some embodiments shown in fig. 3 and 4, a fourth transfer pump 490 is also provided that is connected to a fourth thermostat 940. Similarly, the fourth transfer pump 490 may pump the reaction product flowing from the phosgene feed port 412a through the fourth attemperator 940, the phosgene feed port 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 transfer pump 490 may pump the reaction products within the fourth reaction vessel 400 downstream, e.g., to the purification apparatus 850, etc.
As previously described, the system of the present application requires transfer of the reaction product 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 thus requires transfer through the discharge port 120 of the first reaction vessel 100 to the discharge port 220 of the second reaction vessel 200, the discharge port 220 of the second reaction vessel 200 to the discharge port 320 of the third reaction vessel 300, and the discharge port 320 of the third reaction vessel 300 to the discharge port 420 of the fourth reaction vessel 400. The transfer may be performed by a first transfer pump 190, a second transfer pump 290, and a third transfer pump 390.
In some embodiments, a transfer viewing window 610 is provided on a pipe connecting the discharge port 120 of the first reaction vessel 100 and the discharge port 220 of the second reaction vessel 200, the transfer viewing window 610 being configured for visual observation of the inside of the pipe. The residual condition of the reactant in the pipeline can be observed through the material transferring observation window 610, so that the completion degree of material transferring can be conveniently judged.
In some embodiments, a transfer viewing window 620 is provided on a pipe connecting the discharge port 220 of the second reaction vessel 200 and the discharge port 320 of the third reaction vessel 300, and the transfer viewing window 620 is configured to visually observe the inside of the pipe. The residual condition of reactants in the pipeline can be observed through the material transferring observation window 620, so that the completion degree of material transferring can be conveniently judged.
In some embodiments, a material transfer viewing window 630 is provided on a pipe connecting the discharge port 320 of the third reaction vessel 300 and the discharge port 420 of the fourth reaction vessel 400, and the material transfer viewing window 630 is configured to visually observe the inside of the pipe. The residual condition of reactants in the pipeline can be observed through the material transferring observation window 630, so that the completion degree of material transferring can be conveniently judged.
It should be noted that the above only exemplifies a part of the methods for preparing isocyanates which can be used in the system for preparing isocyanates of the present application, but the method for preparing isocyanates which can be used in 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 container at the temperature of minus 30 ℃ to 90 ℃ to obtain a first reaction product;
(b) Transferring the first reaction product obtained in the step (a) into a second reaction container, mixing with phosgene, and performing 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 with phosgene, and performing a third reaction in the third reaction container at a 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 with phosgene, and performing a fourth reaction in the fourth reaction container at a certain constant temperature between 120 and 300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein, the liquid crystal display device comprises a liquid crystal display device,
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 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).
Embodiment 2: the method according to embodiment 1, characterized in that,
the off-gas of the first reaction vessel in step (a) comprises unreacted phosgene in step (a);
the off-gas of the third reaction vessel in step (c) comprises hydrogen chloride and unreacted complete phosgene in step (c), and optionally, unreacted complete phosgene in step (a), unreacted complete phosgene in step (d); and/or
The off-gas from the fourth reaction vessel in step (d) comprises hydrogen chloride and unreacted phosgene in step (d).
Embodiment 3: the method 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 of any of the preceding embodiments, wherein the phosgene content (w/w) in the off-gas of the third reaction vessel in step (c) is 60% or less.
Embodiment 5: the method according to any one of the preceding embodiments, wherein 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, wherein,
the first reaction product comprises an intermediate carbamyl chloride amine hydrochloride, and optionally, one or more selected from the group consisting of: carbamoyl chloride, unreacted amine and phosgene in step (a);
the second reaction product comprises carbamoyl chloride and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride amine hydrochloride and phosgene in step (b);
The third reaction product comprises an isocyanate and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamoyl chloride hydrochloride in step (b), hydrogen chloride and phosgene, unreacted carbamoyl chloride 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, unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride amine hydrochloride and phosgene in step (b), unreacted carbamoyl chloride and phosgene in step (c), and unreacted phosgene in step (d).
Embodiment 7: the process according to any of the preceding embodiments, wherein prior to step (a), a solvent for the reactant amine is charged into the first reaction vessel and cooled to 0-10 ℃ under nitrogen protection.
Embodiment 8: the method according to any of the preceding embodiments, wherein,
the phosgene in step (b) is derived entirely from the off-gas of the fourth reaction vessel in step (d) and/or the phosgene in step (c) is derived entirely from the off-gas of the first reaction vessel in step (a); or alternatively
The phosgene in step (b) is derived entirely from the offgas of the third reaction vessel in step (c), and/or the phosgene in step (c) is derived entirely from the offgas of the first reaction vessel in step (a) and/or the offgas of the fourth reaction vessel in step (d).
Embodiment 9: the method according to any of the preceding embodiments, characterized in that the flow rates of the reactant amine and phosgene are adjusted with an amine metering pump and a phosgene metering pump, respectively, of the first reaction vessel such that the reactant amine and phosgene are added to the first reaction vessel at a constant rate for the reaction.
Embodiment 10: the process according to any 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 between 30 and 50 ℃ and the reaction temperature in the second stage is raised to between 50 and 90 ℃.
Embodiment 11: the process of any of the preceding embodiments, wherein the molar ratio of reactants amine to phosgene total used in step (a), step (b), step (c) and step (d) is from 1:4 to 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 purifying device for rectification to obtain purified isocyanate.
Embodiment 13: the method according to any of the preceding embodiments, wherein the reactions of the steps are carried out under atmospheric pressure conditions.
Embodiment 14: the method according to any of the preceding embodiments, characterized in that phosgene is used in the first reaction vessel in a stoichiometric excess of 0 to 150% over theoretical value, based on the amine groups of the reactant amine.
Embodiment 15: the method according to 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: according to the foregoing embodimentThe method of any of the formulas, wherein the reactant amine has the formula R (NH 2 ) n Wherein 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 of the preceding embodiments, wherein the reactant amine is selected from one or more of the group consisting of: ethylamine, butylamine, pentylene diamine, hexamethylenediamine, 1, 4-diaminobutane, 1, 8-diaminooctane, aniline, p-phenylenediamine, m-xylylenediamine, toluenediamine, 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, wherein the isocyanate is selected from the group consisting of: diphenylmethylene diisocyanate as pure isomer or as a mixture of isomers, toluene diisocyanate as 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, t-butyl isocyanate, pentyl isocyanate (e.g., pentanediol diisocyanate), t-pentyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate (e.g., hexanediisocyanate), cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate (e.g., p-phenylene diisocyanate).
Embodiment 19: a system for preparing isocyanate, characterized in that the system comprises a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel, a temperature control device, wherein,
the first reaction vessel includes: a solvent feed inlet, a phosgene feed inlet, and a reactant amine feed inlet; 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 quantity of reaction sample from the first reaction vessel;
The second, third and fourth reaction vessels 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 vessels, respectively; a sampling port configured to operably withdraw a quantity of reaction sample from the second, third, or fourth reaction vessel;
the temperature control device is configured to selectively adjust the temperatures of the first, second, third, and fourth reaction vessels to predetermined values;
wherein, the liquid crystal display device comprises a liquid crystal display device,
the vent of the first reaction container is selectively communicated with the emergency discharging device, and the discharge port of the first reaction container is selectively communicated with the discharge port of the second reaction container; the vent of the second reaction container is selectively communicated with the emergency discharging device, and the discharge port of the second reaction container is selectively communicated with the discharge port of the third reaction container; the vent of the third reaction container is selectively communicated with the emergency discharging device, and the discharge port of the third reaction container is selectively communicated with the discharge port of the fourth reaction container; the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and
The tail gas discharge port of the first reaction vessel is in selective communication with the third reaction vessel, and the tail gas discharge port of the fourth reaction vessel is in selective communication with 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 third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the second reaction container.
Embodiment 20: the system of embodiment 19, wherein the vent gas outlet of the first reaction vessel is in selective communication with the phosgene feed inlet of the third reaction vessel and the vent gas outlet 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, wherein the first reaction vessel is provided with a first precooler in communication with its solvent feed or off-gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its off-gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its off-gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its off-gas discharge.
Embodiment 23: the system of claim 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 may be located at any one or more of the following locations: the first reaction vessel interior, the side wall of the first reaction vessel interior, the second reaction vessel interior, the side wall of the second reaction vessel interior, the third reaction vessel interior, the side wall of the third reaction vessel interior, the fourth reaction vessel interior, the side wall of the fourth reaction vessel;
the non-contact temperature sensor is spaced apart 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 to exchange heat 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 in accordance with 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: carbon steel reaction kettle, stainless steel reaction kettle, enamel reaction kettle and steel lining reaction kettle; and/or
And observation holes are formed in the side walls of the first reaction container, the second reaction container, the third reaction container and the fourth reaction container and are used for visually observing the interiors of the first reaction container, the second reaction container, the third reaction container and the fourth reaction container.
Embodiment 26: the system of any one of embodiments 19-25, further comprising one or more of the following: the device comprises a stirring assembly, a metering pumping mechanism, a tail gas treatment device and a purification device;
wherein the stirring assembly may be disposed within the first, second, third, and/or fourth reaction vessels, 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 openings: a solvent feed port, a phosgene feed port, a reactant amine feed port of the first reaction vessel, and phosgene feed ports of the second, third, and fourth reaction vessels for controlling the amount of reactants pumped through these openings;
the tail gas treatment device of the first reaction container is directly applied to the third reaction container, and the tail gas treatment device of the fourth reaction container is directly applied to the second reaction container; or, the tail gas treatment device of the first reaction container and the tail gas treatment device of the fourth reaction container are directly applied to the third reaction container, and the tail gas treatment device of the third reaction container is directly applied to the second reaction container;
The purification device is connected downstream of the fourth reaction vessel.
Embodiment 27: the system of any of embodiments 19-26, wherein,
a first transfer pump is arranged between the discharge port of the first reaction vessel and the discharge port of the second reaction vessel, and the first transfer 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 which is communicated with the discharge port of the first reaction container and the discharge port of the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
A second transfer pump is arranged between the discharge port of the second reaction container and the discharge port of the third reaction container, and the second transfer pump is operable to pump a second reaction product between the discharge port of the second reaction container and the discharge port of the third reaction container; and/or a material transferring observation window is arranged on a pipeline which is communicated with the discharge port of the second reaction container and the discharge port of the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
A third transfer pump is arranged between the discharge port of the third reaction container and the discharge port of the fourth reaction container, and the third transfer pump is operable to pump a third reaction product between the discharge port of the third reaction container and the discharge port of the fourth reaction container; and/or a material transferring observation window is arranged on a pipeline which is communicated with the discharge port of the third reaction container and the discharge port of the fourth reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
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 being 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 which is used for communicating 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 inside of the pipeline; and/or
A sixth transfer pump is arranged between the tail gas treatment device of the fourth reaction vessel and the second reaction vessel, and the sixth transfer pump is operable to pump 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 used for communicating the tail gas treatment device of the fourth reaction container and the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
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 being 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 which is used for communicating the tail gas treatment device of the fourth reaction container and the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
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 being 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 which is communicated with the tail gas treatment device of the third reaction container and the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline.
Embodiment 28: the system of embodiment 27, wherein,
a first temperature regulator is arranged at the upstream of a phosgene feed port of the first reaction container, and phosgene can enter the first reaction container through the first temperature regulator selectively; the first temperature regulator is connected to the first transfer pump, and the first transfer pump can be used for switchably pumping a first reaction product to a discharge hole of the second reaction container or the first temperature regulator; and/or
A second temperature regulator is arranged at the upstream of the phosgene feed port of the second reaction container, and phosgene can enter the second reaction container through the second temperature regulator selectively; 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 port of the third reaction container, and phosgene can enter the third reaction container through the third temperature regulator optionally; 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; and/or
A fourth temperature regulator is arranged at the upstream of a phosgene feed port of the fourth reaction container, and phosgene can enter the fourth reaction container through the fourth temperature regulator selectively; the fourth attemperator is connected to a fourth transfer pump that switchably pumps a fourth reaction product downstream of the fourth attemperator or a 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 normal pressure condition, phosgene is directly introduced into each reaction container, the tail gas of each reaction container is not recycled, and the external circulation is not opened. The specific reaction materials and the amounts of the materials fed are shown in Table 1.
TABLE 1
The embodiment comprises the following steps:
(1) Adding 32kg of raw material o-dichlorobenzene as a backing into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring without external circulation, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.6 kg/8 hr), starting an amine solution metering pump after timing for 20min, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and keeping the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours.
(2) Transferring into a high-temperature kettle R102, heating from 90deg.C to 120deg.C for 0.5 hr, heating at 10deg.C/hr, and adding liquid phosgene at a constant speed of 2.2kg/hr by starting a phosgene metering pump for 3 hr. The temperature is raised from 120 ℃ to 180 ℃ at a speed of 10 ℃/hr, a phosgene metering pump is started, and liquid phosgene is added at a constant speed of 2.2kg/hr for 6 hours.
(3) Starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, reacting at a constant temperature of 180 ℃ under normal pressure for 6 hours, and completely dissolving; then the reaction is carried out for 23 hours at the constant temperature of 180 ℃ under normal pressure, and finally the material is completely dissolved out. Analysis of GC gave 12.2kg of the product pentanediisocyanate with a conversion of 90%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 110kg (2.2 kg/hr. Times.50 h), which far exceeded the theoretical demand of 17.4kg for phosgene.
Example 2
Under the normal pressure condition, phosgene is directly introduced into each reaction container, and tail gas of each reaction container is not recycled, but is externally circulated. The specific reaction materials and the amounts of the materials fed are shown in Table 2.
TABLE 2
The embodiment comprises the following steps:
(1) Adding 32kg of raw material o-dichlorobenzene as a backing into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, stirring to open external circulation, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4 kg/8 hr), timing for 20min, opening an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and maintaining the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours.
(2) Transferring into a high-temperature kettle R102, heating from 90deg.C to 120deg.C for 0.5 hr, heating at 10deg.C/hr, and adding liquid phosgene at a constant speed of 2.2kg/hr by starting a phosgene metering pump for 3 hr. The temperature is raised from 120 ℃ to 180 ℃ at a speed of 10 ℃/hr, a phosgene metering pump is started, and liquid phosgene is added at a constant speed of 2.2kg/hr for 6 hours.
(3) Starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, reacting at a constant temperature of 180 ℃ under normal pressure for 6 hours, and completely dissolving; then the reaction is carried out for 14 hours at the constant temperature of 180 ℃ under normal pressure, and finally the material is completely dissolved and discharged. Analysis of GC gave 12.4kg of the product pentanediisocyanate with a conversion of 91%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 91kg (2.2 kg/hr. Times.41 h), which is far in excess of the theoretical demand of 17.4kg for phosgene. However, the overall reaction time was reduced by 9 hours compared to example 1, and the amount of phosgene used was also reduced by about 20kg.
Example 3
Under the normal pressure condition, the external circulation is carried out, the tail gas of the low-temperature kettle R101 is applied to the high-temperature kettle R103, and then the tail gas is discharged; and (3) 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. The specific reaction materials and the amounts of the materials fed are shown in Table 3.
TABLE 3 Table 3
The embodiment comprises the following steps:
(1) Adding 32kg of raw material o-dichlorobenzene as a backing into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, stirring to open external circulation, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4 kg/8 hr), timing for 20min, opening an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and maintaining the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours.
(2) The materials are transferred into a high-temperature kettle R102, and the temperature is raised from 90 ℃ to 170 ℃ for 0.5 hour at the speed of 10 ℃/hr. The tail gas of the high-temperature kettle R104 is recycled to the high-temperature kettle R102, and fresh phosgene is not introduced into the high-temperature kettle R102 for 7.5 hours in total.
(3) Transferring materials into a high-temperature kettle R103, heating from 170 ℃ to 180 ℃ for 0.5 hour, preserving heat, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 1.5Kg/hr, and receiving tail gas (about 2 Kg/h) of the low-temperature kettle R101 for 7 hours.
(4) Transferring the materials into a high-temperature kettle R104, reacting at a constant temperature of 180 ℃ under normal pressure, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 3.0kg/hr for 7 hours, and finally completely dissolving and discharging. Analysis of GC gave 12.2kg of the product pentanediisocyanate 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 reduced by about 51kg (i.e., by about 47%) from the amount of phosgene used in example 1, and about 32kg (i.e., by about 35%) from the amount of phosgene used in example 2. Moreover, the overall reaction time was reduced by 14 hours compared to example 1 and by 5 hours compared to example 2.
Example 4
Under normal pressure, the external circulation is started, the tail gas of the low-temperature kettle R101 and the high-temperature kettle R104 is applied to the high-temperature kettle R103, the tail gas of the high-temperature kettle R103 is applied to the high-temperature kettle R102, and then the tail gas is discharged. The specific reaction materials and the amounts of the materials fed are shown in Table 4.
TABLE 4 Table 4
The embodiment comprises the following steps:
(1) Adding 32kg of raw material o-dichlorobenzene as a backing into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, stirring to open external circulation, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr (17.4 kg/8 hr), timing for 20min, opening an amine solution metering pump, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and maintaining the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 1.5kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours. The tail gas from the low temperature kettle R101 is then applied to the high temperature kettle R103.
(2) The materials are transferred into a high-temperature kettle R102 for 0.5 hour, the temperature is increased from 90 ℃ to 170 ℃ at the speed of 10 ℃/hr, the tail gas (about 3.2 kg/h) of the high-temperature kettle R103 is introduced into the high-temperature kettle R102, and the total time is 7 hours without using fresh phosgene.
(3) The materials are transferred into a high-temperature kettle R103, the time is 0.5 hour, the temperature is increased from 170 ℃ to 180 ℃ and the temperature is kept, and the tail gas (about 1.7 kg/h) of the low-temperature kettle R101 and the tail gas (about 1.8 kg/h) of the high-temperature kettle R104 are received for 7 hours.
(4) Transferring the materials into a high-temperature kettle R104, reacting at a constant temperature of 180 ℃ under normal pressure, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr for 7 hours, and finally completely dissolving and discharging. Analysis of GC gave 12.0kg of the product pentanediisocyanate with a conversion of 89%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 40.1kg, which was further reduced as compared with example 3, and the time taken for the entire reaction was further reduced.
Example 5
Under normal pressure, the external circulation is started, the tail gas of the low-temperature kettle R101 and the high-temperature kettle R104 is applied to the high-temperature kettle R103, the tail gas of the high-temperature kettle R103 is applied to the high-temperature kettle R102, and then the tail gas is discharged. The specific reaction materials and the amounts of the materials fed are shown in Table 5.
TABLE 5
The embodiment comprises the following steps:
(1) Adding 32kg of o-dichlorobenzene as a raw material into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, starting stirring and 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 (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and keeping the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 1.5kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours. The tail gas from the low temperature kettle R101 is then applied to the high temperature kettle R103.
(2) The materials are transferred into a high-temperature kettle R102 for 0.5 hour, the temperature is increased from 90 ℃ to 170 ℃ at the speed of 10 ℃/hr, the tail gas (about 3.2 kg/h) of the high-temperature kettle R103 is introduced into the high-temperature kettle R102, and the total time is 7 hours without using fresh phosgene.
(3) The materials are transferred into a high-temperature kettle R103, the time is 0.5 hour, the temperature is increased from 170 ℃ to 180 ℃ and the temperature is kept, and the tail gas (about 1.7 kg/h) of the low-temperature kettle R101 and the tail gas (about 1.8 kg/h) of the high-temperature kettle R104 are received for 7 hours.
(4) Transferring the materials into a high-temperature kettle R104, reacting at a constant temperature of 180 ℃ under normal pressure, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.0kg/hr for 7 hours, and finally completely dissolving and discharging. Analysis of GC gave 12.1kg of hexamethylene diisocyanate as a product with a conversion of 93%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 40.1kg, which was further reduced as compared with example 3.
Example 6
Under normal pressure, the external circulation is started, the tail gas of the low-temperature kettle R101 and the high-temperature kettle R104 is applied to the high-temperature kettle R103, the tail gas of the high-temperature kettle R103 is applied to the high-temperature kettle R102, and then the tail gas is discharged. The specific reaction materials and the amounts of the materials fed are shown in Table 6.
TABLE 6
The embodiment comprises the following steps:
(1) Adding 32kg of raw material chlorobenzene into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, stirring, opening external circulation, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, opening an amine solution metering pump after timing for 20min, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and maintaining the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 1.5kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours. The tail gas from the low temperature kettle R101 is then applied to the high temperature kettle R103.
(2) The materials are transferred into a high-temperature kettle R102 for 0.5 hour, the temperature is increased from 90 ℃ to 170 ℃ at the speed of 10 ℃/hr, the tail gas (about 3.2 kg/h) of the high-temperature kettle R103 is introduced into the high-temperature kettle R102, and the total time is 7 hours without using fresh phosgene.
(3) The materials are transferred into a high-temperature kettle R103, the time is 0.5 hour, the temperature is increased from 170 ℃ to 180 ℃ and the temperature is kept, and the tail gas (about 1.7 kg/h) of the low-temperature kettle R101 and the tail gas (about 1.8 kg/h) of the high-temperature kettle R104 are received for 7 hours.
(4) Transferring the materials into a high-temperature kettle R104, reacting at a constant temperature of 180 ℃ under normal pressure, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.0kg/hr for 7 hours, and finally completely dissolving and discharging. Analysis of GC gave 12.8kg of product terephthalyl isocyanate with 96% conversion.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 40.1kg, which was further reduced as compared with example 3, and the time taken for the entire reaction was further reduced.
Example 7
Under normal pressure, the external circulation is started, the tail gas of the low-temperature kettle R101 and the high-temperature kettle R104 is applied to the high-temperature kettle R103, the tail gas of the high-temperature kettle R103 is applied to the high-temperature kettle R102, and then the tail gas is discharged. The specific reaction materials and the amounts of the materials fed are shown in Table 7.
TABLE 7
The embodiment comprises the following steps:
(1) Adding 32kg of raw material chlorobenzene into a low-temperature kettle R101, cooling to 0-10 ℃ under the protection of nitrogen, stirring, opening external circulation, opening a phosgene metering pump, adding liquid phosgene at a constant speed of 2.2kg/hr, opening an amine solution metering pump after timing for 20min, adding liquid amine solution at a constant speed of 6.1kg/hr (49 kg/8 hr), keeping the reaction solution stable to form salt, and gradually heating the reaction temperature and maintaining the temperature at 35-45 ℃. Stirring was continued for 10min after addition was complete, taking 8.5 hours total salt. Changing the cooling into heating, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 1.5kg/hr, and heating the reaction liquid from 50 ℃ to 90 ℃ at a heating speed of 10 ℃/hr for 4 hours. The tail gas from the low temperature kettle R101 is then applied to the high temperature kettle R103.
(2) The materials are transferred into a high-temperature kettle R102 for 0.5 hour, the temperature is increased from 90 ℃ to 170 ℃ at the speed of 10 ℃/hr, the tail gas (about 3.2 kg/h) of the high-temperature kettle R103 is introduced into the high-temperature kettle R102, and the total time is 7 hours without using fresh phosgene.
(3) The materials are transferred into a high-temperature kettle R103, the time is 0.5 hour, the temperature is increased from 170 ℃ to 180 ℃ and the temperature is kept, and the tail gas (about 1.7 kg/h) of the low-temperature kettle R101 and the tail gas (about 1.8 kg/h) of the high-temperature kettle R104 are received for 7 hours.
(4) Transferring the materials into a high-temperature kettle R104, reacting at a constant temperature of 180 ℃ under normal pressure, starting a phosgene metering pump, adding liquid phosgene at a constant speed of 2.0kg/hr for 7 hours, and finally completely dissolving and discharging. Analysis of GC gave 12.3kg of toluene diisocyanate as product with a conversion of 96%.
In the preparation of the isocyanate of this example, the actual amount of phosgene used was about 40.1kg, which was further reduced as compared with example 3, and the time taken for the entire reaction was further reduced.
It should be noted that while in the foregoing detailed description reference is made to different parts of the system and sub-parts of these different parts, this division is merely exemplary and not mandatory. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art by studying the specification, the drawings, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the terms "a" and "an" do not exclude a plurality. In the practice of the present application, one part may perform the functions of a plurality of technical features recited in the claims.

Claims (23)

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 container at the temperature of minus 30 ℃ to 90 ℃ to obtain a first reaction product;
(b) Transferring the first reaction product obtained in the step (a) into a second reaction container, mixing with phosgene, and performing 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 with phosgene, and performing a third reaction in the third reaction container at a 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 with phosgene, and performing a fourth reaction in the fourth reaction container at a certain constant temperature between 120 and 300 ℃ to obtain a fourth reaction product, wherein the fourth reaction product comprises isocyanate;
wherein, the liquid crystal display device comprises a liquid crystal display device,
the phosgene in step (b) is derived entirely from the offgas of the third reaction vessel in step (c), and the phosgene in step (c) is derived entirely from the offgas of the first reaction vessel in step (a) and the offgas of the fourth reaction vessel in step (d);
In the first reaction vessel described in step (a), phosgene is used in a stoichiometric excess of 0% to 150% of theoretical value based on the amine groups of the reactant amine, and the phosgene content in the off-gas of the first reaction vessel described in step (a) is 90% by weight or more;
the phosgene in the second reaction vessel in step (b) is in stoichiometric excess and the phosgene content in the off-gas of the second reaction vessel is 40% by weight or less;
the phosgene in the third reaction vessel in step (c) is in stoichiometric excess and the phosgene content in the off-gas of the third reaction vessel is 60% by weight or less;
the phosgene in step (d) is in stoichiometric excess and the phosgene content in the off-gas of the fourth reaction vessel is 95% by weight or more;
the molar ratio of the reactants amine to phosgene used in step (a), step (b), step (c) and step (d) is between 1:4 and 1:8; and is also provided with
The reactant amine is diamine.
2. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the off-gas of the first reaction vessel in step (a) comprises unreacted phosgene in step (a);
The off-gas of the third reaction vessel in step (c) comprises hydrogen chloride and unreacted complete phosgene in step (c), and optionally, unreacted complete phosgene in step (a), unreacted complete phosgene in step (d); and/or
The off-gas from the fourth reaction vessel in step (d) comprises hydrogen chloride and unreacted phosgene in step (d).
3. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the first reaction product comprises an intermediate carbamyl chloride amine hydrochloride, and optionally, one or more selected from the group consisting of: carbamoyl chloride, unreacted amine and phosgene in step (a);
the second reaction product comprises carbamoyl chloride and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride amine hydrochloride and phosgene in step (b);
the third reaction product comprises an isocyanate and hydrogen chloride, and optionally, one or more selected from the group consisting of: unreacted amine and phosgene in step (a), unreacted intermediate carbamoyl chloride hydrochloride in step (b), hydrogen chloride and phosgene, unreacted carbamoyl chloride 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, unreacted amine and phosgene in step (a), unreacted intermediate carbamyl chloride amine hydrochloride and phosgene in step (b), unreacted carbamoyl chloride and phosgene in step (c), and unreacted phosgene in step (d).
4. The process of claim 1, wherein prior to step (a), a solvent for the reactant amine is introduced into the first reaction vessel and cooled to 0-10 ℃ under nitrogen protection.
5. The method according to claim 1, wherein the flow rates of the reactant amine and phosgene are adjusted by an amine metering pump and a phosgene metering pump, respectively, of the first reaction vessel such that the reactant amine and phosgene are added to the first reaction vessel at a constant rate for reaction.
6. The process according to claim 1, wherein the first reaction in step (a) is carried out in two temperature ranges, respectively, wherein the reaction temperature in the first stage is maintained at 30 to 50 ℃ and the reaction temperature in the second stage is raised to 50 to 90 ℃.
7. The method according to claim 1, characterized in that the method further comprises the steps of:
(e) And (d) transferring the fourth reaction product obtained in the step (d) into a purifying device for rectification to obtain purified isocyanate.
8. The method according to claim 1, wherein the reactions of each step are carried out under atmospheric pressure.
9. The method of any one of claims 1-8, 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.
10. The method of any one of claims 1-8, wherein the reactant amine has the formula R (NH 2 ) n Wherein n is 2 and R isAliphatic, alicyclic or aromatic hydrocarbon groups having 2 to 10 carbon atoms.
11. The method of any one of claims 1-8, wherein the reactant amine is selected from one or more of the group consisting of: pentanediamine, hexamethylenediamine, 1, 4-diaminobutane, 1, 8-diaminooctane, p-phenylenediamine, m-xylylenediamine, toluenediamine, 1, 5-naphthalenediamine, diphenylmethane diamine, dicyclohexylmethane diamine, m-cyclohexyldimethylene diamine, isophorone diamine, trans-1, 4-cyclohexanediamine.
12. The method according to any one of claims 1 to 8, wherein the isocyanate is selected from the group consisting of: diphenylmethylene diisocyanate as pure isomer or as isomer mixture, toluene diisocyanate as pure isomer or isomer mixture, 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, tert-amyl isocyanate, isopentyl isocyanate, neopentyl isocyanate, hexyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate.
13. The method of claim 12, wherein the amyl isocyanate is a pentanediisocyanate; the hexyl isocyanate is hexamethylene diisocyanate; or the phenyl isocyanate is terephthalyl isocyanate.
14. An apparatus for preparing isocyanate according to the method of claim 1, characterized in that the apparatus comprises a first reaction vessel, a second reaction vessel, a third reaction vessel, a fourth reaction vessel, a temperature control device, wherein,
The first reaction vessel includes: a solvent feed inlet, a phosgene feed inlet, and a reactant amine feed inlet; 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 quantity of reaction sample from the first reaction vessel;
the second, third and fourth reaction vessels 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 vessels, respectively; a sampling port configured to operably withdraw a quantity of reaction sample from the second, third, or fourth reaction vessel;
the temperature control device is configured to selectively adjust the temperatures of the first, second, third, and fourth reaction vessels to predetermined values;
wherein, the liquid crystal display device comprises a liquid crystal display device,
the vent of the first reaction vessel is selectively communicated with the emergency discharging device, the discharge port of the first reaction vessel is selectively communicated with the discharge port of the second reaction vessel, a first transfer pump is arranged between the discharge port of the first reaction vessel and the discharge port of the second reaction vessel, and the first transfer 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;
The vent of the second reaction container is selectively communicated with the emergency discharging device, and the discharge port of the second reaction container is selectively communicated with the discharge port of the third reaction container; a second transfer pump is arranged between the discharge port of the second reaction container and the discharge port of the third reaction container, and the second transfer pump is operable to pump a second reaction product between the discharge port of the second reaction container and the discharge port of the third reaction container;
the vent of the third reaction container is selectively communicated with the emergency discharging device, and the discharge port of the third reaction container is selectively communicated with the discharge port of the fourth reaction container; a third transfer pump is arranged between the discharge port of the third reaction container and the discharge port of the fourth reaction container, and the third transfer pump is operable to pump a third reaction product between the discharge port of the third reaction container and the discharge port of the fourth reaction container;
the vent of the fourth reaction vessel is in selective communication with an emergency discharge device, and
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 third reaction container, and the tail gas discharge port of the third reaction container is selectively communicated with the second reaction container;
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 being 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;
a seventh rotation is arranged between the tail gas treatment device of the fourth reaction container and the third reaction container
A feed pump, the seventh transfer pump being operable to pump off-gas of the fourth reaction vessel between the off-gas treatment device of the fourth reaction vessel and the third reaction vessel;
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 being 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 is also provided with
The temperature regulation range of the first reaction container is-30-90 ℃, the temperature regulation range of the second reaction container is 90-200 ℃, the temperature regulation range of the third reaction container is 120-250 ℃, and the temperature regulation range of the fourth reaction container is 120-300 ℃; and, in addition, the processing unit,
The first reaction vessel, the second reaction vessel, the third reaction vessel and the fourth reaction vessel are respectively used for carrying out the reactions of each stage for preparing isocyanate, wherein,
the phosgene in the first reaction vessel for the reaction to be carried out is used in a stoichiometric excess of 0% to 150% over the theoretical value, and the phosgene content in the off-gas of the first reaction vessel is 90% by weight or more;
the phosgene in the second reaction vessel used in the reaction performed is in stoichiometric excess, and the phosgene content in the off-gas of the second reaction vessel is 40% by weight or less;
the third reaction vessel is used for the reaction in which phosgene is stoichiometrically excess and the phosgene content in the off-gas of the third reaction vessel is 60% by weight or less;
the phosgene in the fourth reaction vessel used in the reaction performed is in stoichiometric excess, and the phosgene content in the off-gas of the fourth reaction vessel is 95% by weight or more; and, in addition, the processing unit,
the molar ratio of diamine to phosgene used in the reaction at each stage of isocyanate preparation is between 1:4 and 1:8.
15. The apparatus of claim 14, wherein the vent gas discharge of the first reaction vessel and the vent gas discharge of the fourth reaction vessel are each in selective communication with the phosgene feed of the third reaction vessel, and wherein the vent gas discharge of the third reaction vessel is in selective communication with the phosgene feed of the second reaction vessel.
16. The apparatus of claim 14, wherein the discharge ports of the first, second, third, and/or fourth reaction vessels are each in selective communication with an emergency discharge device.
17. The apparatus according to claim 14, wherein the first reaction vessel is provided with a first precooler in communication with its solvent feed or off-gas discharge, and/or the second reaction vessel is provided with a second precooler in communication with its off-gas discharge, and/or the third reaction vessel is provided with a third precooler in communication with its off-gas discharge, and/or the fourth reaction vessel is provided with a fourth precooler in communication with its off-gas discharge.
18. The device of claim 14, wherein the temperature control device comprises a temperature sensor, the temperature sensor being a contact temperature sensor and/or a non-contact temperature sensor, wherein,
the contact temperature sensor may be located at any one or more of the following locations: the first reaction vessel interior, the side wall of the first reaction vessel interior, the second reaction vessel interior, the side wall of the second reaction vessel interior, the third reaction vessel interior, the side wall of the third reaction vessel interior, the fourth reaction vessel interior, the side wall of the fourth reaction vessel;
The non-contact temperature sensor is spaced apart from the first reaction vessel, and/or the second reaction vessel, and/or the third reaction vessel, and/or the fourth reaction vessel.
19. The apparatus of claim 18, wherein the temperature control apparatus further comprises:
heat exchange means attachable to or formed by the side walls of the first, second, third and fourth reaction vessels to exchange heat 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 in accordance with the measurement signal.
20. The apparatus of any one of claims 14-19, wherein the first, second, third, and fourth reaction vessels are selected from the group consisting of: carbon steel reaction kettle, stainless steel reaction kettle, enamel reaction kettle and steel lining reaction kettle; and/or
And observation holes are formed in the side walls of the first reaction container, the second reaction container, the third reaction container and the fourth reaction container and are used for visually observing the interiors of the first reaction container, the second reaction container, the third reaction container and the fourth reaction container.
21. The apparatus of any one of claims 14-19, further comprising one or more of the following: the device comprises a stirring assembly, a metering pumping mechanism, a tail gas treatment device and a purification device;
wherein the stirring assembly may be disposed within the first, second, third, and/or fourth reaction vessels, 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 openings: a solvent feed port, a phosgene feed port, a reactant amine feed port of the first reaction vessel, and phosgene feed ports of the second, third, and fourth reaction vessels for controlling the amount of reactants pumped through these openings;
The tail gas treatment device of the first reaction container and the tail gas treatment device of the fourth reaction container are directly applied to the third reaction container, and the tail gas treatment device of the third reaction container is directly applied to the second reaction container;
the purification device is connected downstream of the fourth reaction vessel.
22. The device according to any one of claims 14 to 19, wherein,
a material transferring observation window is arranged on a pipeline which is communicated with the discharge port of the first reaction container and the discharge port of the second reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
A material transferring observation window is arranged on a pipeline which is communicated with the discharge port of the second reaction container and the discharge port of the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
A material transferring observation window is arranged on a pipeline which is communicated with the discharge port of the third reaction container and the discharge port of the fourth reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; 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 inside of the pipeline; 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 container and the third reaction container, and the material transferring observation window is configured to be used for visually observing the inside of the pipeline; and/or
The pipeline which is communicated with the tail gas treatment device of the third reaction container and the second reaction container is provided with a material turning observation window, and the material turning observation window is configured to be used for visually observing the inside of the pipeline.
23. The apparatus of claim 22, wherein the device comprises a plurality of sensors,
a first temperature regulator is arranged at the upstream of a phosgene feed port of the first reaction container, and phosgene can enter the first reaction container through the first temperature regulator selectively; the first temperature regulator is connected to the first transfer pump, and the first transfer pump can be used for switchably pumping a first reaction product to a discharge hole of the second reaction container or the first temperature regulator; and/or
A second temperature regulator is arranged at the upstream of the phosgene feed port of the second reaction container, and phosgene can enter the second reaction container through the second temperature regulator selectively; 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 port of the third reaction container, and phosgene can enter the third reaction container through the third temperature regulator optionally; 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; and/or
A fourth temperature regulator is arranged at the upstream of a phosgene feed port of the fourth reaction container, and phosgene can enter the fourth reaction container through the fourth temperature regulator selectively; the fourth attemperator is connected to a fourth transfer pump that switchably pumps a fourth reaction product downstream of the fourth attemperator or a fourth reaction vessel.
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