CN115093348B

CN115093348B - Method for preparing isocyanate by pipeline phosgene method

Info

Publication number: CN115093348B
Application number: CN202210798904.8A
Authority: CN
Inventors: 薛永和; 陆成樑; 刘文杰; 刘佳特; 袁海新; 邱贵森
Original assignee: Mojia Shanghai Biotechnology Co ltd
Current assignee: Mojia Shanghai Biotechnology Co ltd
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2023-10-27
Anticipated expiration: 2042-07-06
Also published as: CN115093348A

Abstract

The application relates to a method for producing isocyanates. In particular, the present application provides a process for preparing isocyanates by the pipeline phosgenation process.

Description

Method for preparing isocyanate by pipeline phosgene method

Technical Field

The present application relates to a process for preparing isocyanates, more particularly to a process for preparing isocyanates by the pipeline phosgene 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. Because of the high reactivity of amines (particularly aliphatic diamines), the amine that is not reacted temporarily may react with the reaction products and intermediates during the phosgenation reaction, thereby producing byproducts such as amine hydrochlorides, urea, biuret, and the like. To avoid the formation of by-products, a capping reagent (e.g., HCl) may be selected to cap the amine group (-NH) of the amine ₂ ) Protecting to form amine salt. However, amine salts are much less reactive than free amines and are practically insoluble in any common organic solvent and can only be dispersed in the solvent. It has been proved that the phosgenation reaction using amine salts as raw materials generally requires the use of a large amount of solvent as a dispersant, and the content of amine salts in the solvent is often less than 10%, and the residence time of the phosgenation reaction is often several hours or even tens of hours.

Thus, there remains a need for an optimized isocyanate preparation process.

Disclosure of Invention

The object of the present application is to provide a process for preparing isocyanates, more particularly isocyanates by the pipeline phosgene process.

In one aspect, the present application provides a process for preparing an isocyanate, the process comprising the steps of:

(a) Mixing the reactant amine stream and the phosgene stream at a temperature of-5 to 5 ℃ to obtain a mixture of reactant amine and phosgene;

(b) Positive pressure delivering the mixture obtained in step (a) to a reactor comprising a first temperature controlled zone and a second temperature controlled zone, wherein the temperature of the first temperature controlled zone is 180 ℃ to 260 ℃ and the reaction time in the first temperature controlled zone is 1 to 30 seconds; the temperature of the second temperature control zone is 280-400 ℃, and the reaction time in the second temperature control zone is 1-30 seconds.

In certain embodiments, the mixture obtained in step (a) is fed to the reactor at positive pressure using a diaphragm pump in step (b). In certain embodiments, the mixture obtained in step (a) is delivered to the reactor at positive pressure using a diaphragm pump with a polytetrafluoroethylene pump head in step (b).

In certain embodiments, the method of preparing an isocyanate further comprises step (c) collecting the product. In certain embodiments, the step (c) comprises: providing a quench zone at the outlet of the reactor such that the reaction product mixture obtained in step (b) is contacted with a quench medium stream passing into the quench zone, and reducing the temperature of the reaction product mixture obtained in step (b) to below 170 ℃.

In certain embodiments, the method further comprises step (d) purifying the product. In certain embodiments, step (d) comprises:

1) Introducing the reaction product mixture obtained in the step (b) or the step (c) into a degassing tower, wherein hydrogen chloride and phosgene in the reaction product mixture overflow from the top of the degassing tower and enter a hydrogen chloride/phosgene separation tower, and the hydrogen chloride overflowed from the top of the separation tower is refined by a tail gas removal treatment unit to form hydrochloric acid as a byproduct;

2) Recycling phosgene from the bottom of the separation column of sub-step 1) to form the phosgene stream of step (a);

3) Collecting isocyanate and byproducts from the bottom of the degasser of sub-step 1) in the reaction product mixture, passing them through a lights removal column to remove lights byproducts;

4) Collecting isocyanate and heavy component byproducts from the bottom of the light component removal column of sub-step 3), passing them through a refining column, collecting isocyanate from the refining column, and removing heavy component byproducts.

In certain embodiments, step (a) is performed before step (b).

In certain embodiments, no organic solvent is used in both step (a) and step (b).

In certain embodiments, in step (a), the reactant amine stream and the phosgene stream are mixed and then shear emulsified to form suspended particles. In certain embodiments, the suspended particles have a diameter of less than or equal to 100 μm; preferably less than or equal to 50 μm; more preferably less than or equal to 20. Mu.m.

In certain embodiments, in step (a), the reactant amine stream and the phosgene stream are mixed and then sheared and emulsified uniformly by a homogenizing pump. In certain embodiments, the shear emulsification uniformity is achieved by controlling the lift, rotational speed, torque, suction, and/or shear homogenization time of the homogenizing pump. In certain embodiments, the circulating output volume of the homogenizing pump is controlled to be greater than or equal to 10 times the volume of the liquid holdup in the compounding kettle.

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

In certain embodiments, the ratio of the phosgene stream to the reactant amine stream feed (on a molar basis) in step (a) is from 7:1 to 25:1. In certain embodiments, the ratio of the phosgene stream to the reactant amine stream feed (on a molar basis) in step (a) is from 10:1 to 20:1. In certain embodiments, the phosgene stream and reactant amine stream in step (a) are fed in a ratio (on a molar basis) of 12:1.

In certain embodiments, the phosgene stream in step (a) is present in liquid form.

In certain embodiments, the temperature of the first temperature controlled zone in step (b) is from 200 ℃ to 240 ℃. In certain embodiments, the temperature of the first temperature controlled zone in step (b) is from 210 ℃ to 230 ℃. In certain embodiments, the temperature of the first temperature controlled zone in step (b) is 220 ℃.

In certain embodiments, the reaction time of the first temperature controlled zone in step (b) is from 2 seconds to 10 seconds. In certain embodiments, the reaction time of the first temperature controlled zone in step (b) is from 3 seconds to 6 seconds. In one embodiment, the reaction time of the first temperature controlled zone in step (b) is 4 seconds.

In certain embodiments, the temperature of the second temperature controlled zone in step (b) is 300 ℃ to 350 ℃. In certain embodiments, the temperature of the second temperature controlled zone in step (b) is from 310 ℃ to 330 ℃. In certain embodiments, the temperature of the second temperature controlled zone in step (b) is 320 ℃.

In certain embodiments, the reaction time of the second temperature controlled zone in step (b) is from 2 seconds to 10 seconds. In certain embodiments, the reaction time of the second temperature controlled zone in step (b) is from 3 seconds to 4 seconds. In certain embodiments, the reaction time of the second temperature controlled zone in step (b) is 3 seconds.

In certain embodiments, the product collection temperature of step (c) is 170 ℃ or less. In certain embodiments, the product collection temperature of step (c) is from 80 ℃ to 150 ℃. In certain embodiments, the product collection temperature of step (c) is from 110 ℃ to 140 ℃.

In certain embodiments, in step (c), the latent heat of vaporization of the quenching medium is utilized to rapidly reduce the temperature of the reaction product mixture obtained in step (b).

In certain embodiments, the quenching medium described in step (c) is selected from the group consisting of: an organic solvent, isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof. In certain embodiments, the organic solvent is selected from the group consisting of: dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof. In certain embodiments, the quenching medium described in step (c) is in a liquid state. In certain embodiments, the quenching medium described in step (c) is liquid phosgene.

In certain embodiments, the reactor described in step (b) is a pipeline reactor. In certain embodiments, the pipeline reactor is a coil pipeline reactor. In certain embodiments, the conduit reactor has a conduit inner diameter of 2 to 20mm. In certain embodiments, the conduit reactor has a conduit inner diameter of 3 to 8mm. In certain embodiments, the conduit reactor has a conduit inner diameter of 4 to 5mm.

In certain embodiments, the isocyanate is a diisocyanate. In certain embodiments, the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate. 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 certain embodiments, the isocyanate in the present application is Pentamethylene Diisocyanate (PDI), hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), or methylcyclohexane diisocyanate (HTDI).

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 or aromatic hydrocarbon group. In certain embodiments, n is 2 and R is an aliphatic hydrocarbon group. In certain embodiments, n is 2 and R is an aliphatic hydrocarbon group having 2 to 10 carbon atoms. In certain embodiments, n is 2 and R is a linear or cyclic aliphatic hydrocarbon group having 3 to 10 carbon atoms.

In certain embodiments, the reactant amine is present in free form.

In certain embodiments, the reactant amine is present in the form of an amine salt. In certain embodiments, the amine salt is selected from the group consisting of: hydrochloride, sulfate, bisulfate, nitrate and carbonate.

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, methylcyclohexane diamine, trans-1, 4-cyclohexanediamine.

In certain embodiments, the reactant amine is selected from the group consisting of: PDA, PDA hydrochloride, HDA hydrochloride, IPDA hydrochloride, HTDA and HTDA hydrochloride.

Drawings

The above and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. It is appreciated that these drawings depict only several embodiments of the present disclosure and are therefore not to be considered limiting of its scope. The present application will be described more specifically and in detail with reference to the accompanying drawings.

FIG. 1 shows a schematic flow diagram of a process for preparing isocyanates according to one embodiment of the present application; wherein: 01 is a batching kettle, 02 is a diaphragm pump, 03 is a low-temperature pipeline reactor, 04 is a high-temperature pipeline reactor, 05 is a quenching zone, 06 is a light component removing tower, and 07 is a product refining tower.

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 inventive subject matter. It will be readily understood that the aspects of the present disclosure, as generally described and illustrated in the figures herein, could be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated as part of this disclosure.

In the present application, "isocyanate" refers to a class of compounds containing one or more (e.g., two, three, four, five, six, seven, eight, nine, ten 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, the isocyanate in the present application is a diisocyanate. In certain embodiments, the isocyanate in the present application is an aliphatic diisocyanate or an aromatic diisocyanate. In certain embodiments, the isocyanates in the present application include 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. In certain embodiments, the isocyanate is PDI, HDI, IPDI or HTDI.

The steps (a) and (b), and optionally the steps (c) and (d), respectively, of the process for preparing isocyanates according to the application are described in detail below.

1.Step (a)

In step (a) of the present application, the reactant amine stream and the phosgene stream are mixed at a temperature of from-5 to 5 ℃ to obtain a mixture of reactant amine and phosgene.

In the present application, "reactant amine" means that the starting material for preparing isocyanate contains amino (-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 or aromatic hydrocarbon group. In some embodimentsN is 2, and R is an aliphatic hydrocarbon group. In certain embodiments, n is 2 and R is an aliphatic, cycloaliphatic, 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, n is 2 and R is a linear or cyclic aliphatic hydrocarbon group having 3-10 carbon atoms (e.g., 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 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, methylcyclohexane 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, isophoronediamine, methylcyclohexamethylenediamine, toluenediamine. In certain embodiments, the reactant amine is Pentylene Diamine (PDA).

In certain embodiments, the reactant amine is present in free form. The term "free" refers to the amine compound in a non-salt form. Amine compounds in the free form may differ from their various salt forms in certain physical and/or chemical properties, for example, solubility in polar solvents. The amine compounds in the free form may also be the same or similar in certain physical and/or chemical properties as their various salt forms.

In certain embodiments, the reactant amine is selected from one or more of the following groups: pentanediamine (PDA), PDA hydrochloride, hexamethylenediamine (HDA), HDA hydrochloride, isophorone diamine (IPDA), IPDA hydrochloride, methylcyclohexamethylenediamine (HTDA) and HTDA hydrochloride.

In conventional methods of preparing isocyanates, organic solvents are typically used to disperse the reactant amine, or inert carrier gases (e.g., nitrogen, carbon dioxide, carbon monoxide, helium, or argon) are used to assist in the vaporization of the reactant amine and to achieve a more suitable dispersing effect. However, in the present invention, the inventors have unexpectedly found that the mixing of reactant amine and phosgene in step (a) may be accomplished without the use of an organic solvent and without the use of an inert carrier gas. In order to facilitate mixing the reactant amine stream and the phosgene stream to facilitate the subsequent reaction, in step (a), the reactant amine stream and the phosgene stream may be mixed and then sheared to form suspended particles. In certain embodiments, the suspended particles have a diameter of, for example, less than or equal to 100 μm, or less than or equal to 50 μm, or less than or equal to 20 μm. In certain embodiments, the suspended particles have a diameter of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm, or any value or range between any two of the foregoing. Without being bound by any theory, it is believed that the smaller the diameter of the suspended particles formed, the more advantageous the subsequent reaction of the reactants amine and phosgene proceeds.

After mixing the reactant amine and phosgene streams in step (a), shear emulsification may be performed using any method known in the art. For example, a high-speed shearing emulsifying machine, a supergravity mixing device, a homogenizing pump, etc. can be used to uniformly shear and emulsify reactant amine and phosgene by a mechanical shearing method. In certain embodiments, the reactant amine stream and the phosgene stream are mixed and then sheared and emulsified uniformly by a homogenizing pump. The homogenizing pump used in the present application may be commercially available, for example, a DHX type homogenizing pump available from Ningbodeli pump industry Co.

In certain embodiments, step (a) is to introduce the reactant amine stream and the phosgene stream into a batch kettle for mixing. In the art, the homogenizing pump may be provided inside the batch tank (referred to as an "internal homogenizing pump" in this case) or outside the batch tank (referred to as an "external homogenizing pump" in this case). In certain embodiments of the application, the homogenizing pump is an in-built homogenizing pump. When an internal homogenizing pump is used, the shearing and emulsifying uniformity can be preferably achieved by controlling the lift, rotation speed, torque, suction force and/or shearing and homogenizing time of the homogenizing pump, and specific values can be determined according to the size of the batching kettle and/or experience of the person skilled in the art. In certain embodiments, the built-in homogenizing pump is set at a rotational speed of 1000 to 3000r/min. In certain embodiments, the built-in homogenizing pump is provided with a flow rate of 120 to 250m ³ And/h. In certain embodiments, the internal homogenizing pump is set at a pressure of 0.1 to 1.2MPa. In certain embodiments, the inlet of the in-built homogenizing pump is provided at a value or range between 80mm and 110mm (e.g., 85mm, 90mm, 95mm, 96mm, 97mm, 98mm, 99mm, 100mm, 105mm, 110mm, or any two of the above). In certain embodiments, the outlet of the in-built homogenizing pump is provided as 60mm to 90mm (e.g., 65mm, 70mm, 75mm, 76mm, 77mm, 78mm, 79mm, 80mm, 81mm, 82mm, 83mm, 84mm, 85mm, 90mm, or any value or range between any two of the above).

Without being bound by any theory, it is believed that when the built-in homogenizing pump circulates an output volume n times the volume of the liquid holdup in the batch kettle, the built-in homogenizing pump has performed at least n shear emulsions of the reactants amine and phosgene therein. For example: when the circulation output volume of the built-in homogenizing pump is 10 times of the volume of the liquid holdup in the batching kettle, the built-in homogenizing pump has sheared and emulsified reactant amine and phosgene for 10 times. In some embodiments, whether the shearing emulsification uniformity has been achieved is determined based on the internal homogenizing pump circulating output volume being greater than or equal to 10 times the volume of the liquid holdup in the compounding tank. For example, when the internal homogenizing pump circulation output volume is greater than or equal to 10 times the volume of the liquid holdup in the batch tank (e.g., the internal homogenizing pump circulation output volume is 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50 or more times the liquid holdup in the batch tank), then it is determined that the mixing of reactant amine and phosgene has achieved shear emulsification uniformity.

In some embodiments, the homogenizing pump is an external homogenizing pump, the homogenizing pump is arranged outside the batching kettle, and the sheared and emulsified emulsion is directly conveyed into the batching kettle from the homogenizing pump. When an external homogenizing pump is used, a person skilled in the art can ensure that shearing and emulsification are uniform by controlling the type and the rotating speed of the homogenizing pump outside the batching kettle and the residence time of the materials in the homogenizing pump. In certain embodiments, the external homogenizing pump is set to a rotational speed of 1000 to 3000r/min. In some embodiments, the external homogenizing pump is set to have a flow rate of 120 to 250m ³ And/h. In certain embodiments, the external homogenizing pump is set at a pressure of 0.1 to 1.2MPa. In certain embodiments, the inlet of the external homogenizing pump is provided at a value or range between 80mm and 110mm (e.g., 85mm, 90mm, 95mm, 96mm, 97mm, 98mm, 99mm, 100mm, 105mm, 110mm, or any two of the above). In certain embodiments, the outlet of the external homogenizing pump is provided at 60mm to 90mm (e.g., 65mm, 70mm, 75mm, 76mm, 77mm, 78mm, 79mm, 80mm, 81mm, 82mm, 83mm, 84mm, 85mm, 90mm, or any value or range between two of the foregoing values).

In certain embodiments, the reactant amine stream of step (a) is in a liquid state prior to entering the batch tank. The reactant amine stream described in step (a) may enter the batching kettle via a single reactant amine-containing substream or via multiple (e.g., 2, 3, 4, 5, or more) reactant amine-containing substreams. Likewise, the phosgene stream described in step (a) may enter the batching kettle via a single phosgene-containing substream, or via multiple (e.g., 2, 3, 4, 5 or more) phosgene-containing substreams. When the reactant amine stream (or phosgene stream) in step (a) enters the batching kettle via multiple substreams containing the reactant amine (or phosgene), multiple substreams may enter the batching kettle at the same location or may enter the batching kettle at different locations.

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. Therefore, in order to prevent the formation of by-products, phosgene is preferably supplied in an excess form. For example, in certain embodiments, the phosgene stream described in step (a) is in stoichiometric excess based on the amino groups of the reactant amine stream. For example, the molar ratio of phosgene to amine groups of the reactant amine is typically 1.1:1 to 30:1 (e.g., 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 11:1, 15:1, 20:1, 25:1, 30:1, and ranges between any of the above). In certain embodiments, phosgene is used in excess of 0% to 250% (e.g., 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 210%, 220%, 230%, 240%, 250%, etc.) of stoichiometric excess over the amino groups of the reactant amine in the batch tank. When the reactant amine stream (and/or phosgene stream) described in step (a) enters the batching kettle via a plurality of reactant amine (and/or phosgene) -containing substreams, the plurality of phosgene-containing substreams and the total phosgene stream produced are stoichiometrically excess based on the amino groups of the plurality of reactant amine-containing substreams and the total reactant amine stream produced.

In certain embodiments, the ratio of the phosgene stream and reactant amine stream feed (on a molar basis) described in step (a) is from 7:1 to 25:1 (e.g., 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, or any value between any two of the above). Preferably, the ratio of the phosgene stream to the reactant amine stream feed (on a molar basis) as described in step (a) is from 10:1 to 20:1, for example 12:1.

The phosgene contained in the phosgene stream described in step (a) may be fresh phosgene or recycled phosgene. The term "fresh phosgene" refers to a phosgene-containing stream which has not been recycled from the phosgenation process and which has not been subjected to any reaction stage involving the reaction of phosgene after synthesis of phosgene, typically from chlorine and carbon monoxide. The term "recycled phosgene" refers to the phosgene-containing stream produced in the tail gas collected from the reaction process for the preparation of isocyanates by the phosgenation process. As described above, in the process of preparing isocyanate by gas phase method, it is often necessary to use excessive phosgene, so that a large amount of phosgene is contained in the reaction tail gas, and the purpose of reducing production cost can be achieved by recycling the phosgene in the tail gas. In certain embodiments, the phosgene stream described in step (a) is present in liquid form.

In certain embodiments, the reactant amine stream and phosgene stream described in step (a) are mixed at low temperature, preferably at any temperature between-5 and 5 ℃, such as at a temperature of-5 ℃, -4 ℃, -3 ℃, -2 ℃, -1 ℃, 0 ℃, 1 ℃, 2 ℃, 3 ℃, 4 ℃, 5 ℃ or any value or range between any two of the above values. When the reactant amine streams and phosgene streams are mixed at a temperature of-5 to 5 c, no reaction occurs and a mixture of reactant amine and phosgene is obtained. The mixing may be carried out at any constant temperature between-5 and 5 ℃, or at a varying temperature between-5 and 5 ℃. In one embodiment, the mixing is performed at a temperature of 0 ℃.

In certain embodiments, step (a) is performed prior to step (b), i.e., the reactants amine and phosgene are mixed prior to their reaction and then the reaction is co-warmed. One of the advantages of such an operation is that decomposition of the reactant amine (e.g., amine salt) at high temperatures, or self-cyclization to produce byproducts, can be avoided.

2.Step (b)

In step (b) of the present application, the mixture obtained in step (a) is fed under positive pressure into a reactor comprising a first temperature controlled zone and a second temperature controlled zone, wherein the temperature of the first temperature controlled zone is 180 ℃ to 260 ℃ and the reaction time in the first temperature controlled zone is 1 to 30 seconds; the temperature of the second temperature control zone is 280-400 ℃, and the reaction time in the second temperature control zone is 1-30 seconds.

In step (b) of the present application, the reaction is carried out in two stages. Without being bound by any theory, it is believed that such a staged temperature setting has unexpected effects, such as allowing the acid chloride formation reaction (i.e., the reaction performed in the first temperature controlled zone) and the acid chloride decomposition reaction (i.e., the reaction performed in the second temperature controlled zone) to proceed completely separately, avoiding side reactions between the target product (i.e., isocyanate) and the intermediate product, allowing for higher overall reaction selectivity, less impurities, higher yields, and more complete reaction. Furthermore, the reaction can be carried out in a sectional manner, so that various reaction conditions can be controlled and regulated more precisely.

Taking as an example the starting reaction materials of glutaric amine hydrochloride and phosgene, the reaction mainly carried out in the first stage in step (b) is as follows:

wherein the reaction of the first stage is completed in said first temperature controlled zone in step (b).

In certain embodiments, the temperature of the first temperature controlled zone in step (b) is 180 ℃ to 260 ℃. In certain embodiments, the temperature of the first temperature controlled zone in step (b) is 200 ℃ to 240 ℃, e.g., 201 ℃, 202 ℃, 203 ℃, 204 ℃, 205 ℃, 206 ℃, 207 ℃, 208 ℃, 209 ℃, 210 ℃, 211 ℃, 212 ℃, 213 ℃, 214 ℃, 215 ℃, 216 ℃, 217 ℃, 218 ℃, 219 ℃,220 ℃, 221 ℃, 222 ℃, 223 ℃, 224 ℃, 225 ℃, 226 ℃, 227 ℃, 228 ℃, 229 ℃, 230 ℃, 231 ℃, 232 ℃, 233 ℃, 234 ℃, 235 ℃, 236 ℃, 237 ℃, 238 ℃, 239 ℃, 240 ℃, or any value or range between any two of the foregoing, e.g., 210 ℃ to 230 ℃ (e.g., 220 ℃).

In certain embodiments, in step (b), the reaction time in the first temperature controlled zone is 2 seconds to 10 seconds, such as 2 seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5 seconds, 5 seconds, 5.5 seconds, 6 seconds, 6.5 seconds, 7 seconds, 7.5 seconds, 8 seconds, 8.5 seconds, 9 seconds, 9.5 seconds, 10 seconds, or any value or range between any two of the foregoing. In certain embodiments, the reaction time in the first temperature controlled zone is 3 seconds to 6 seconds (e.g., 4 seconds, 5 seconds, or 6 seconds). Without being bound by any theory, it is believed that it is preferable to keep the reaction time of the reactants amine and phosgene short, since the formation of by-products can be avoided as much as possible. The residence time of the mixture obtained in step (a) in the first temperature controlled zone may be controlled in various ways, for example by controlling the flow rate of the mixture obtained in step (a) by means of a flow regulating device; for example, the flow rate of the mixture obtained in step (a) is increased and its residence time in the first temperature controlled zone is reduced.

In certain embodiments, the temperature of the first temperature controlled zone is 220 ℃, and the reaction time in the first temperature controlled zone is 4 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 200 ℃, and the reaction time in the first temperature controlled zone is 4 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 240 ℃, and the reaction time in the first temperature controlled zone is 4 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 220 ℃, and the reaction time in the first temperature controlled zone is 2 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 220 ℃, and the reaction time in the first temperature controlled zone is 3 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 220 ℃, and the reaction time in the first temperature controlled zone is 5 seconds. In certain embodiments, the temperature of the first temperature controlled zone is 220 ℃, and the reaction time in the first temperature controlled zone is 6 seconds.

Taking glutaraldehyde hydrochloride and phosgene as starting materials for example, the main reactions performed in the second stage are as follows:

the reaction at this stage is completed in said second temperature controlled zone in step (b). In certain embodiments, the temperature of the second temperature controlled zone is 280 ℃ to 400 ℃, such as 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, 360 ℃, 370 ℃, 380 ℃, 390 ℃, or 400 ℃, and any value or range between any two of the values described above. In certain embodiments, the temperature of the second temperature controlled zone is 300 ℃ to 350 ℃. In certain embodiments, the temperature of the second temperature controlled zone is 310 ℃ to 330 ℃. In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃.

In certain embodiments, the reaction time in the second temperature controlled zone is 2 seconds to 10 seconds, such as 2 seconds, 2.5 seconds, 3 seconds, 3.5 seconds, 4 seconds, 4.5 seconds, 5 seconds, 5.5 seconds, 6 seconds, 6.5 seconds, 7 seconds, 7.5 seconds, 8 seconds, 8.5 seconds, 9 seconds, 9.5 seconds, 10 seconds, and any value or range between any two of the foregoing. In certain embodiments, the reaction time in the second temperature controlled zone is 3 seconds to 4 seconds. Without being bound by any theory, it is believed that keeping the reaction time of phosgene and intermediate IM2 short is preferable because the formation of by-products can be avoided as much as possible. The residence time of the mixture of phosgene and intermediate IM2 in the second temperature-controlled zone can be controlled in a number of ways, for example by controlling the flow rate of the mixture of phosgene and intermediate IM2 by means of a flow-regulating device; for example, the flow of the mixture of phosgene and intermediate IM2 increases and its residence time in the second temperature-controlled zone decreases.

In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃, and the reaction time in the second temperature controlled zone is 3 seconds. In certain embodiments, the temperature of the second temperature controlled zone is 300 ℃, and the reaction time in the second temperature controlled zone is 3 seconds. In certain embodiments, the temperature of the second temperature controlled zone is 340 ℃, and the reaction time in the second temperature controlled zone is 3 seconds. In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃, and the reaction time in the second temperature controlled zone is 1 second. In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃, and the reaction time in the second temperature controlled zone is 2 seconds. In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃, and the reaction time in the second temperature controlled zone is 4 seconds. In certain embodiments, the temperature of the second temperature controlled zone is 320 ℃, and the reaction time in the second temperature controlled zone is 5 seconds.

In certain embodiments, the reactor described in step (b) is a pipeline reactor. In the present application, the "pipeline reactor" may also be called a tubular reactor, and refers to a continuously operated reactor with a tubular shape and a large length-diameter ratio, and belongs to a plug flow reactor. The length of the pipeline reactor can be adjusted, and the pipeline reactor is characterized in that continuous reaction can be realized, and the reaction cannot be backmixed. The pipeline reactors generally comprise horizontal pipe reactors, riser reactors, coil pipe reactors, U-pipe reactors and the like. In certain embodiments, the pipeline reactor is a coil pipeline reactor. Different inner diameters and/or volumes of pipe reactors may be used depending on the reaction throughput and the like. The pressure of the reaction can be adjusted by adjusting the inner diameter of the pipe reactor. For example, an excessively large inner diameter may result in incomplete reaction of the reactant amine and phosgene; too small an inside diameter may result in pipe plugging. In certain embodiments, the conduit reactor used in the present application has a conduit inner diameter of 2 to 20mm (e.g., 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, or any value between any two of the above ranges of values). In certain embodiments, the conduit reactor used in the present application has a conduit inner diameter of 3 to 8mm. In certain embodiments, the conduit reactor used in the present application has a conduit inner diameter of 4 to 5mm. In certain embodiments, the coiled tubing reactor is a coiled tubing reactor having an inner diameter of 4 millimeters, a vertical height of 84 centimeters, a total length of 70 meters, and a total volume of 879.2 milliliters. In certain embodiments, the coiled tubing reactor is a coiled tubing reactor having an inner diameter of 3 millimeters, a vertical height of 84 centimeters, a total length of 70 meters, and a total volume of 494.5 milliliters.

The pipeline reactor used in the present application may be commercially available; or can be prepared by itself, for example, by using self-purchased stainless steel tubes and processing and shaping the tubes by a die.

In certain embodiments, the pressure of the pipeline reactor of step (b) is controlled to be between 50 and 140KPa (e.g., 60KPa, 65KPa, 70KPa, 75KPa, 80KPa, 85KPa, 90KPa, 95KPa, 100KPa, 105KPa, 110KPa, 115KPa, 120KPa, 125KPa, 130KPa, 135KPa or any value between any two above ranges of values, e.g., 80 to 110 KPa).

The first temperature control zone and the second temperature control zone may be located in different regions, such as upstream and downstream regions, within the same pipe reactor. The first temperature control area and the second temperature control area can have the same or different volumes, and on the premise of the same inner diameter, the volume identity can be controlled by controlling the length and the height of the pipeline. In certain embodiments, the volume ratio of the first temperature controlled zone to the second temperature controlled zone is 4:3. When the flow rate of the mixture obtained in the step (a) in the reactor is fixed, the volume ratio of the first temperature control zone to the second temperature control zone is the reaction residence time ratio of the reaction in the first temperature control zone to the second temperature control zone. In certain embodiments, the first and second temperature controlled zones have the same inner diameter and length, but are 48cm and 36cm in height, respectively.

In certain embodiments, the first and second temperature controlled zones of the reactor may be heated separately. For example, two different heating furnaces are adopted and the temperatures are respectively controlled; or two different heat medium circulation systems are adopted.

The first temperature control zone and the second temperature control zone can also adopt pipeline reactors with different inner diameters according to conditions. The pipe reactors with different inner diameters can be connected through joints, for example, seamless connection is realized through a closed joint.

In certain embodiments, the mixture obtained in step (a) is fed to the reactor at positive pressure using a diaphragm pump in step (b). In the present application, the "diaphragm pump" may also be referred to as a control pump, which separates the body to be infused from the plunger and the pump cylinder by means of a membrane, thereby protecting the plunger and the pump cylinder. The parts of the diaphragm, which are in contact with the liquid, are each made of a corrosion-resistant material or coated with a corrosion-resistant substance. In the art, the diaphragm pump diaphragm is respectively arranged in various special occasions according to different liquid media, such as nitrile rubber, chloroprene rubber, fluororubber, polytetrafluoroethylene, polytetrafluoroethene and the like, and is used for pumping various media to meet the needs. The inventors of the present application tried to use various kinds of pump heads, such as polypropylene (PP), polyethylene (PE) and the like, which were all found to be corroded by phosgene, and finally screened out stable and corrosion-resistant Polytetrafluoroethylene (PTEE) pump heads. Thus, in certain embodiments, the diaphragm pump is provided with a polytetrafluoroethylene pump head (also referred to herein as a "polytetrafluoroethylene pump head").

In the present application, "positive pressure delivery" means that the mixture obtained in step (a) is pumped into the reactor using a pump (e.g., a diaphragm pump, a metering pump, etc.). When the mixture obtained in step (a) is fed into the reactor, the reactor inlet has a section which naturally forms a step-by-step temperature rise, since phosgene is rapidly gasified and absorbs a large amount of heat, during which a large amount of gaseous phosgene acts as a carrier gas pushing the reactant amine through the reactor at a faster rate. Thus, in certain embodiments, without the use of an organic solvent in step (b), phosgene may be both a reactant and a solvent, as well as a transport fluid that facilitates the reaction to proceed continuously. During the reaction in the reactor, the reactant amine undergoes the processes of surface melting, phosgenation, acid chloride decomposition, product evaporation, and the remaining reactant amine continues to react until disappearing. The reaction time of the first temperature controlled zone and/or the second temperature controlled zone may be controlled by controlling the flow rate and feed rate of the pump.

3.Step (c)

In certain embodiments, the methods of making of the present application further comprise (c) collecting the product.

In certain embodiments, step (c) of the present application comprises the sub-steps of: providing a quench zone at the outlet of the reactor such that the reaction product mixture obtained in step (b) is contacted with a quench medium stream passing into the quench zone, reducing the temperature of the reaction product mixture obtained in step (b) to a temperature below 170 ℃ (e.g., 160 ℃, 150 ℃, 140 ℃, 130 ℃, 120 ℃, 110 ℃, 100 ℃, 90 ℃, 80 ℃, 70 ℃, 60 ℃, 50 ℃ or any value between any two of the above values). In certain embodiments, the product collection temperature of step (c) is from 80 ℃ to 150 ℃. In certain embodiments, the product collection temperature of step (c) is from 110 ℃ to 140 ℃.

Common quenching media in the art include solvents, isocyanates or mixtures of isocyanates with solvents; wherein the solvent may be an organic solvent, preferably an organic solvent which does not participate in the reaction. The quenching medium in the present application may be selected from the group consisting of: an organic solvent, isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof. In certain embodiments, the organic solvent is selected from the group consisting of: dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof. In certain embodiments, the quenching medium is or does not comprise a solvent. In certain embodiments, the quenching medium is or does not comprise an organic solvent (e.g., chlorobenzene, toluene, hexane, tetrahydrofuran, chloronaphthalene), and the like. In certain embodiments, the quenching medium is fresh phosgene. In certain embodiments, the quenching medium is recycled phosgene. In certain embodiments, the quenching medium described in step (c) is in a liquid state. In certain embodiments, the quenching medium described in step (c) is liquid phosgene.

Without being bound by any theory, it is believed that the use of phosgene or a mixture of phosgene and isocyanate as the quenching medium works better than the use of an organic solvent as the quenching medium. For example, the use of phosgene or the mixture of phosgene and isocyanate as a quenching medium can avoid the use of an organic solvent in the whole reaction system and the problem of inlet blockage caused by solid coanda, so that the whole process has no links of solvent recovery, rectification and cyclic refining, and the preparation process is simpler, lower in energy consumption and lower in cost. Meanwhile, the high-temperature refining process is shortened, so that the high-temperature residence time of the isocyanate as a reaction product is greatly shortened, the self-polymerization reaction is reduced, and the product yield is higher.

In general, the quenching medium itself has a lower temperature to better act to reduce the reaction product mixture, and may be, for example, from-50 to-10 ℃ (e.g., -50 ℃, -45 ℃, -40 ℃, -35 ℃, -30 ℃, -25 ℃, -20 ℃, -15 ℃, -10 ℃ or any value in between any two ranges of values above). In certain embodiments, the temperature of the quenching medium is-20 ℃.

In certain embodiments, in step (c), the reaction product mixture obtained in step (b) is rapidly reduced in temperature using the latent heat of vaporization of the quenching medium. For example, the quenching medium causes a momentary decrease in the temperature of the reaction product mixture obtained in step (b), for example at least 200 ℃/sec. Without being bound by any theory, it is believed that it is preferable to provide a momentary decrease in the temperature of the reaction product mixture obtained in step (b), as this ensures the purity of the target product; if the temperature is not reduced in as short a time as possible, the reaction product mixture obtained in step (b) may polymerize to give impurities. The temperature of the reaction product mixture may be instantaneously reduced by a variety of means, such as increasing the flow rate of the quench medium, decreasing the initial temperature of the quench medium, increasing the spray dispersion effect of the quench medium to increase the heat exchange rate, and so forth.

4.Step (d)

In certain embodiments, the method further comprises step (d) purifying the product.

In certain embodiments, the step (d) comprises the sub-steps of:

Taking fig. 1 as an example, PDA hydrochloride and phosgene are mixed in a batch kettle 01 at low temperature (e.g., at a temperature of-5 to 5 ℃) to obtain a mixture of PDA hydrochloride and phosgene. The mixture of PDA hydrochloride and phosgene is then conveyed to a low temperature pipeline reactor 03 and a high temperature pipeline reactor 04 for reaction by a diaphragm pump 02 under positive pressure, and a reaction product mixture is obtained. The reaction product mixture is passed through a light component removal column 06 after being cooled in a quenching zone 05 to remove light component byproducts (e.g., piperidine, polyhydropiperidine, etc.) from the top of the light component removal column 06; the target product (isocyanate) and heavy component byproducts (e.g., tar, PDI self-polymers, urea, etc.) are collected from the bottom of the light component removal column 06 and passed through the product refining column 07. The target product (isocyanate) is collected from the top of the product refining column 07 and heavy component byproducts are removed from the bottom of the product refining column 07.

When the reactant amine is an amine salt, the process for preparing the isocyanate of the present application avoids the step of converting the amine salt to an amine compared to conventional gas or liquid phase phosgenation; compared with the existing salt-forming phosgene process, the phosgene used in the application can be used as a solvent of reactant amine and also can be used as a starting material of the reaction, so that a large amount of solvent is avoided. In addition, in the process of preparing isocyanate by using the method, the acyl chloride generation reaction and the acyl chloride decomposition reaction are completely and separately carried out, so that side reactions between a target product and an intermediate product are avoided, the whole reaction selectivity is higher, the impurities are less, the yield is high, and the reaction is more thorough. In addition, the mixture of phosgene or phosgene and isocyanate can be used as a quenching medium in the reaction process, so that the problem of inlet blockage caused by the attachment of solid walls can be avoided, the links of solvent recovery, rectification and circulating refining are omitted in the whole process, the preparation process is simpler and more convenient, the energy consumption is lower, and the cost is lower. The method of the application ensures that the flow of isocyanate production is simple and time-saving, the energy consumption is reduced, and the reaction selectivity and the comprehensive yield are obviously improved by strictly controlling the reaction temperature and time in two temperature control areas in the pipeline.

The foregoing is a summary of the application and there may be a simplification, generalization, and omission of details, so it will be recognized by those skilled in the art 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.

Examples

In order that the application may be more fully understood, the following examples are set forth. It should be understood that these examples are for illustrative purposes only and are not to be construed as limiting in any way.

Some of the noun abbreviations mentioned in the examples are shown in table 1.

Table 1: noun abbreviations

English abbreviations	Chinese name
		PDI	Pentamethylene diisocyanate
PDA	Pentanediamine

The technical scheme of the application is exemplified below by taking PDA hydrochloride to prepare PDI as an example.

Example 1: selection of diaphragm pump heads

Example 1A: PE material diaphragm pump head

1750g (10 mol) PDA hydrochloride and 11880g (120 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃, and then are sent into a 100L stirring kettle, and a homogenizing device is arranged in the kettle.

Stirring is started, a built-in homogenizing pump is started at the same time, and shearing and mixing are carried out uniformly.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started for a coiled pipe type pipeline reactor with an inner diameter of 4 millimeters (mm), a vertical height of 84 centimeters (cm), a total length of 70 meters (m) and a total volume of 879.2 milliliters (ml). The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a PE (polyethylene) pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front section and the rear section is 4 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, extremely cold capturing and drawing the effluent gas (liquid) through a quenching medium at the temperature of minus 20 ℃ to obtain a product collecting liquid, after 3 minutes, enabling the diaphragm pump to have a liquid leakage phenomenon, stopping the pump in an emergency way, disconnecting all pipelines connected with the pump, and disassembling the pump after emergency treatment, so that the pump head is found to be corroded by phosgene. The reaction cannot proceed.

Example 1B: diaphragm pump head made of PP material

Starting a diaphragm pump with a PP (polypropylene) pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front and back sections is 4 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, extremely cold capturing and drawing the effluent gas (liquid) through a quenching medium at the temperature of minus 20 ℃ to obtain a product collecting liquid, after about 2 minutes, causing the diaphragm pump to have liquid leakage, stopping the pump emergently, disconnecting all pipelines connected with the pump, and disassembling the pump after emergency treatment, wherein the pump head is found to be corroded by phosgene. The reaction cannot proceed.

Example 1C: isolation pump head made of polytetrafluoroethylene material

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started for a coiled pipe type pipeline reactor with an inner diameter of 4 millimeters (mm), a vertical height of 84 centimeters (cm), a total length of 70 meters (m) and a total volume of 879.2 milliliters (m 1). The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid. In the whole reaction process, the pump head is intact, so that the isolation pump head made of polytetrafluoroethylene material is selected to screen the following reaction conditions.

Example 2: selection of isocyanate reaction conditions

A summary of the material ratios, reaction conditions, and final yields for the preparation of PDI using PDA hydrochloride in the various examples below are shown in table 2.

Table 2: preparation of PDI from PDA hydrochloride

(the quenching medium is phosgene or phosgene and PDI mixed solution)

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The steps and results of the various embodiments are described in detail below, respectively. In each of examples 2A to 2W below, phosgene or a mixture of phosgene and PDI was used as a quenching medium.

Example 2A: PDI preparation by PDA hydrochloride

The front and rear heating rods were turned on to heat the molten salt in the two sleeves, and a 4 millimeter (mm) inner diameter, a vertical height of 84 centimeters (cm), a total length of 70 meters (m), and a total volume of 879.2 milliliters (ml) coil pipe reactor was started to preheat. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to obtain 1592g for gas phase quantitative analysis, which showed a content of 87.4%, and a reaction yield of 90.4% was calculated.

Example 2B: PDI preparation of PDA hydrochloride (heterogeneous shearing)

1750g (10 mol) PDA hydrochloride and 11880g (120 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃ and then are fed into a 100L stirring kettle, and a homogenizing device is not arranged in the kettle.

Stirring is started to mix PDA hydrochloride and liquid phosgene, and the mixture is sheared in a heterogeneous manner.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

The reaction was stopped in the middle of the reaction, and the reaction could not be continued.

The collected liquid was separated to recover phosgene after hydrogen chloride gas was separated, and then 1400g of the residue was weighed for gas phase quantitative analysis, and the result showed a content of 77.4%, and the reaction yield was calculated to be 70.4%.

Example 2C: PDI preparation of PDA hydrochloride (inner diameter of reactor 3 mm)

Stirring is started to mix the PDA hydrochloride and the liquid phosgene, and the mixture is subjected to homogenizing shearing.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with an inner diameter of 3mm, a vertical height of 84cm, a total length of 70m and a total volume of 494.5 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at a speed of 70.6ml/s, namely, the residence time of the front and back sections is 4 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 464g of the residue was weighed for gas phase quantitative analysis, and the result showed a content of 85.2%, and the reaction yield was calculated to be 25.7%.

Example 2D: PDI preparation of PDA hydrochloride (inner diameter of reactor 5 mm)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with an inner diameter of 5mm, a vertical height of 84cm, a total length of 70m and a total volume of 1373 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 196.2ml/s, namely, the residence time of the front and back sections is 4 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to give 1506.0g, which was quantitatively analyzed in a gas phase to show 86.2% content, and the reaction yield was calculated to be 84.3%.

Example 2E: PDI preparation of PDA hydrochloride (inner diameter of reactor 8 mm)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating of the coiled pipe type pipeline reactor with the internal diameter of 8mm, the vertical height of 84cm, the total length of 70m and the total volume of 3517ml is started. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 502.4ml/s, namely, the residence time of the front section and the rear section is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene after hydrogen chloride gas was separated, and then 1538.1g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 80.3%, and the reaction yield was calculated to be 80.2%.

Example 2F: PDI (front molten salt preheating to 200 ℃ C.)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 200 ℃ and the rear molten salt is preheated to 320 ℃.

The collected liquid was separated to recover phosgene after hydrogen chloride gas was separated, and then 1557g of the residue was weighed and analyzed quantitatively in a gas phase, and the result showed a content of 81.3% and a calculated reaction yield of 82.2%.

Example 2G: PDI (front molten salt preheating to 240 ℃ C.)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 240 ℃ and the rear molten salt is preheated to 320 ℃.

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1616.7g, and was subjected to gas phase quantitative analysis, and the result showed a content of 84.3%, and the reaction yield was calculated to be 88.5%.

Example 2H: PDI (rear molten salt preheating to 300 ℃ C.)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front fused salt is preheated to 220 ℃, and the rear fused salt is preheated to 300 ℃.

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1607.7g, and was subjected to gas phase quantitative analysis, and the result showed a content of 84.2%, and the reaction yield was calculated to be 87.9%.

Example 2I: PDI (rear molten salt preheating to 340 ℃ C.)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 48cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 36cm, namely the volume ratio is 4:3, and all the pipeline reactors are immersed in the molten salt bath. The front fused salt is preheated to 220 ℃, and the rear fused salt is preheated to 340 ℃.

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1617.1g, and was subjected to gas phase quantitative analysis, whereby the content was 83.9%, and the reaction yield was calculated to be 88.1%.

Example 2J: PDI (molar ratio of phosgene to PDA hydrochloride is 12:1, and the residence time in the former stage is 2s)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactor in the front section heating furnace sleeve is 33.6cm, the vertical height of the pipeline reactor in the rear section heating furnace sleeve is 50.4cm, namely the volume ratio is 2:3, and the pipeline reactor is completely immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at a speed of 175.8ml/s, namely, the residence time of the front and back sections is 2 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to obtain 1849.2g for gas phase quantitative analysis, which showed a content of 50.3%, and a reaction yield of 60.4% was calculated.

Example 2K: PDI preparation from PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 10:1, front-stage residence time is 3s)

1750g (10 mol) PDA hydrochloride and 990g (100 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃, and then are sent into a 100L stirring kettle, and a homogenizing device is arranged in the kettle.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactor in the front section heating furnace sleeve is 42cm, the vertical height of the pipeline reactor in the rear section heating furnace sleeve is 42cm, namely the volume ratio is 3:3, and the pipeline reactor is completely immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 146.5ml/s, namely, the residence time of the front section and the rear section is 3 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 1540g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 76.0%, and the reaction yield was calculated to be 75.9%.

Example 2L: PDI preparation from PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 16:1, front-stage residence time is 5s)

1750g (10 mol) PDA hydrochloride and 15840g (160 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃, and then are sent into a 100L stirring kettle, and a homogenizing device is arranged in the kettle.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactor in the front section heating furnace sleeve is 52.5cm, the vertical height of the pipeline reactor in the rear section heating furnace sleeve is 31.5cm, namely the volume ratio is 5:3, and the pipeline reactor is completely immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 109.9ml/s, namely, the residence time of the front and back sections is 5 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 1594.7g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 87.2%, and the reaction yield was calculated to be 90.3%.

Example 2M: PDI preparation from PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 20:1, front-stage residence time is 6s)

1750g (10 mol) PDA hydrochloride and 19800g (200 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃, and then are sent into a 100L stirring kettle, and a homogenizing device is arranged in the kettle.

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted to enable the vertical height of the pipeline reactor in the front section heating furnace sleeve to be 56cm, and the vertical height of the pipeline reactor in the rear section heating furnace sleeve to be 28cm, namely the volume ratio is 6:3, and the pipeline reactor is completely immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 97.7ml/s, namely, the residence time of the front and back sections is 6 seconds and 3 seconds respectively, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 1587.5g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 87.5%, and the reaction yield was calculated to be 90.2%.

Example 2N: PDI (post residence time 1 s) prepared from PDA hydrochloride

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted to enable the vertical height of the pipeline reactor in the front section heating furnace sleeve to be 67cm, the vertical height of the pipeline reactor in the rear section heating furnace sleeve to be 17cm, namely the volume ratio is 4:1, and the pipeline reactor is completely immersed in molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at a speed of 175.8ml/s, namely, the residence time of the front section and the rear section is respectively 4 seconds and 1 second, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene after hydrogen chloride gas was separated, and then 1675.1g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 51.3%, and the reaction yield was calculated to be 55.8%.

Example 2O: PDI (post residence time 2 s) prepared from PDA hydrochloride

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted to enable the vertical height of the pipeline reactor in the front section heating furnace sleeve to be 56cm, and the vertical height of the pipeline reactor in the rear section heating furnace sleeve to be 28cm, namely the volume ratio is 4:2, and the pipeline reactor is completely immersed in molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 146.5ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 2 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to obtain 1724.2g for gas phase quantitative analysis, which showed a content of 62.7%, and a reaction yield of 70.2% was calculated.

Example 2P: PDI preparation of PDA hydrochloride (post-residence time 4 s)

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactors are vertically arranged at the central positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactors in the front section heating furnace sleeve is 42cm, the vertical height of the pipeline reactors in the rear section heating furnace sleeve is 42cm, namely the volume ratio is 4:4, and all the pipeline reactors are immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 109.9ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 4 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 1577.5g of the residue was weighed and subjected to gas phase quantitative analysis, which showed 86.3% content and 88.4% reaction yield was calculated.

Example 2Q: PDI (post residence time 5 s) prepared from PDA hydrochloride

The front end and the rear end heating rods are started to heat molten salt in the two sleeves, and preheating is started to a coiled pipe type pipeline reactor with the internal diameter of 4mm, the vertical height of 84cm, the total length of 70m and the total volume of 879.2 ml. The coil pipe type pipeline reactor is vertically arranged at the center positions of the two molten salt sleeves, the positions are adjusted so that the vertical height of the pipeline reactor in the front section heating furnace sleeve is 37.3cm, the vertical height of the pipeline reactor in the rear section heating furnace sleeve is 46.7cm, namely the volume ratio is 4:5, and the pipeline reactor is completely immersed in the molten salt bath. The front molten salt is preheated to 220 ℃, and the rear molten salt is preheated to 320 ℃.

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 97.6ml/s, namely, the residence time of the front section and the rear section is respectively 4 seconds and 5 seconds, controlling the pressure in the pipeline to be 80KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1560.6g, and was subjected to gas phase quantitative analysis, whereby the content was 82.1%, and the reaction yield was calculated to be 83.2%.

Example 2R: PDI preparation with PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 10:1)

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1584.2g, and was subjected to gas phase quantitative analysis, and the result showed a content of 73.1%, and the reaction yield was calculated to be 75.2%.

Example 2S: PDI preparation with PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 14:1)

1750g (10 mol) PDA hydrochloride and 13860g (140 mol) liquid phosgene are stirred and mixed uniformly at 0 ℃, and then are sent into a 100L stirring kettle, and a homogenizing device is arranged in the kettle.

The collected liquid was separated to recover phosgene, and then 1594.8g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 87.0%, and the reaction yield was calculated to be 90.1%.

Example 2T: PDI preparation with PDA hydrochloride (molar ratio of phosgene to PDA hydrochloride is 16:1)

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front section and the back section is 4 seconds and 3 seconds respectively, and enabling effluent gas (liquid) to pass through quenching medium at the temperature of minus 20 ℃ for extremely cold capturing and drawing to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then 1596.5g of the residue was weighed and subjected to gas phase quantitative analysis, and the result showed a content of 87.2%, and the reaction yield was calculated to be 90.4%.

Example 2U: PDI (50 KPa pressure) preparation of PDA hydrochloride

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front section and the rear section is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 50KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to obtain hydrogen chloride gas, and phosgene was recovered, and then the residue was weighed to obtain 1583.6g, and was subjected to gas phase quantitative analysis, and the result showed a content of 81.2%, and the reaction yield was calculated to be 83.5%.

Examples2V: PDI (110 KPa pressure) preparation of PDA hydrochloride

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 110KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to obtain 1572.6g for gas phase quantitative analysis, which showed a content of 75.4%, and a reaction yield of 77.0% was calculated.

Example 2W: PDI preparation of PDA hydrochloride (140 KPa pressure)

Starting a diaphragm pump with a tetrafluoro pump head, pumping mixed slurry of PDA hydrochloride and liquid phosgene into a pipeline reactor at the speed of 125.6ml/s, namely, the residence time of the front and back sections is respectively 4 seconds and 3 seconds, controlling the pressure in the pipeline to be 140KPa, and enabling effluent gas (liquid) to pass through quenching medium extremely cold capturing at the temperature of minus 20 ℃ to obtain product collecting liquid.

The collected liquid was separated to recover phosgene, and then the residue was weighed to obtain 1761.5g for gas phase quantitative analysis, which showed 58.4% content and calculated to yield 66.8%.

Claims

1. A process for preparing an isocyanate, said process comprising the steps of:

(a) Mixing a reactant amine stream and a phosgene stream at a temperature of-5 to 5 ℃ to obtain a mixture of the reactant amine and the phosgene, shearing and emulsifying uniformly by a homogenizing pump after the reactant amine stream and the phosgene stream are mixed, and the molar quantity ratio of the phosgene stream to the reactant amine stream is 7:1 to 25:1;

(b) Positive pressure conveying the mixture obtained in step (a) into a pipeline reactor, wherein the reactor comprises a first temperature control zone and a second temperature control zone, the temperature of the first temperature control zone is 180-260 ℃, and the reaction time in the first temperature control zone is 2-10 seconds; the temperature of the second temperature control zone is 280-400 ℃, and the reaction time in the second temperature control zone is 2-10 seconds; the pressure of the pipeline reactor is controlled between 50 KPa and 140KPa, and the inner diameter of a pipeline of the pipeline reactor is 4 mm to 20mm;

Wherein the structural formula of the reactant amine is R (NH) ₂ ) _n Wherein n is 2, R is an aliphatic alkylene group having 2 to 10 carbon atoms or an aromatic alkylene group having 3 to 10 carbon atomsA base.

2. The method of claim 1, wherein the mixture obtained in step (a) is fed to the reactor at positive pressure using a diaphragm pump with a polytetrafluoroethylene pump head in step (b).

3. The method of claim 1, further comprising the step of (c) collecting the product.

4. A method according to claim 3, wherein step (c) comprises: providing a quench zone at the outlet of the reactor such that the reaction product mixture obtained in step (b) is contacted with a quench medium stream passing into the quench zone, reducing the temperature of the reaction product mixture obtained in step (b) to below 170 ℃; and said quenching medium is selected from the group consisting of: an organic solvent, isocyanate, phosgene, hydrogen chloride, an inert carrier gas, and any combination thereof.

5. The method of claim 1, further comprising the step of (d) purifying the product.

6. The method of claim 5, wherein step (d) comprises:

7. The method of claim 1, wherein step (a) is performed before step (b).

8. The method of claim 1, wherein no organic solvent is used in both step (a) and step (b).

9. The method of claim 1, wherein in step (a), the reactant amine stream and the phosgene stream are mixed and then shear emulsified to form suspended particles.

10. The method of claim 9, wherein the suspended particles have a diameter of less than or equal to 100 μm.

11. The method of claim 10, wherein the suspended particles have a diameter of less than or equal to 50 μιη.

12. The method of claim 10, wherein the suspended particles have a diameter of less than or equal to 20 μιη.

13. The method according to claim 1, wherein the shear emulsification uniformity is achieved by controlling the lift, rotational speed, torque, suction force and/or shear homogenization time of the homogenizing pump.

14. The method of claim 13, wherein the circulating output volume of the homogenizing pump is controlled to be greater than or equal to 10 times the volume of the liquid hold-up in the batch kettle.

15. The process of claim 1, wherein the molar amount of phosgene stream and reactant amine stream feed in step (a) is in the range of 10:1 to 20:1.

16. The method of claim 15, wherein the molar ratio of the phosgene stream to reactant amine stream feed in step (a) is 12:1.

17. The method of claim 1, wherein the phosgene stream in step (a) is present in liquid form.

18. The method of claim 1, wherein the temperature of the first temperature controlled zone in step (b) is from 200 ℃ to 240 ℃.

19. The method of claim 18, wherein the temperature of the first temperature controlled zone in step (b) is from 210 ℃ to 230 ℃.

20. The method of claim 19, wherein the temperature of the first temperature controlled zone in step (b) is 220 ℃.

21. The method of claim 1, wherein in step (b), the reaction time in the first temperature controlled zone is from 3 seconds to 6 seconds.

22. The method of claim 21, wherein in step (b), the reaction time in the first temperature controlled zone is 4 seconds.

23. The method of claim 1, wherein the temperature of the second temperature controlled zone in step (b) is 300 ℃ to 350 ℃.

24. The method of claim 23, wherein the temperature of the second temperature controlled zone in step (b) is 310 ℃ to 330 ℃.

25. The method of claim 24, wherein the temperature of the second temperature controlled zone in step (b) is 320 ℃.

26. The method of claim 25, wherein in step (b), the reaction time in the second temperature controlled zone is from 3 seconds to 4 seconds.

27. The method of claim 26, wherein in step (b), the reaction time in the second temperature controlled zone is 3 seconds.

28. A process according to claim 3, wherein the product collection temperature of step (c) is 170 ℃ or less.

29. A process according to claim 3, wherein the product collection temperature of step (c) is from 80 ℃ to 150 ℃.

30. A process according to claim 3, wherein the product collection temperature of step (c) is from 110 ℃ to 140 ℃.

31. The process of claim 4 wherein in step (c) the latent heat of vaporization of the quenching medium is used to rapidly reduce the temperature of the reaction product mixture obtained in step (b).

32. The method of claim 4, wherein the organic solvent is selected from the group consisting of: dichloromethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, tetrahydrofuran, chloronaphthalene, and any combination thereof.

33. The method of claim 4, wherein the quenching medium in step (c) is in a liquid state.

34. The method of claim 33, wherein the quenching medium in step (c) is liquid phosgene.

35. The method of claim 1, wherein the pipeline reactor is a coil pipeline reactor.

36. The method according to claim 1, wherein the pipeline reactor has a pipeline inner diameter of 3 to 8mm.

37. The method of claim 36, wherein the conduit reactor has a conduit inner diameter of 4 to 5mm.

38. The method of claim 1, wherein the isocyanate is a diisocyanate.

39. The method according to claim 1, wherein the isocyanate is an aliphatic diisocyanate or an aromatic diisocyanate.

40. The process according to claim 1, wherein the isocyanate is toluene diisocyanate or 1, 5-naphthalene diisocyanate as pure isomer or as a mixture of isomers.

41. The method according to claim 1, wherein the isocyanate is pentanediisocyanate, hexanediisocyanate, or terephthalisocyanate.

42. The method of claim 1, wherein the isocyanate is PDI, HDI, IPDI or HTDI.

43. The method of claim 1, wherein the reactant amine has the formula R (NH ₂ ) _n Wherein n is 2 and R is a linear or cyclic aliphatic having 3 to 10 carbon atomsHydrocarbylene groups.

44. The method of any one of claims 1-43, wherein the reactant amine is present in free form.

45. The method of any one of claims 1-43, wherein the reactant amine is present in the form of an amine salt.

46. The method of claim 45, wherein the amine salt is selected from the group consisting of: hydrochloride, sulfate, bisulfate, nitrate and carbonate.

47. The method of any one of claims 1-39, 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, m-cyclohexyldimethylenediamine, isophoronediamine, methylcyclohexamethylenediamine, trans-1, 4-cyclohexanediamine.

48. The method of any one of claims 1-39, wherein the reactant amine is selected from the group consisting of: PDA, PDA hydrochloride, HDA hydrochloride, IPDA hydrochloride, HTDA and HTDA hydrochloride.