CN117466778B - Method for producing isocyanates and isocyanate production system - Google Patents
Method for producing isocyanates and isocyanate production system Download PDFInfo
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- CN117466778B CN117466778B CN202311785346.2A CN202311785346A CN117466778B CN 117466778 B CN117466778 B CN 117466778B CN 202311785346 A CN202311785346 A CN 202311785346A CN 117466778 B CN117466778 B CN 117466778B
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- 239000012948 isocyanate Substances 0.000 title claims abstract description 50
- 150000002513 isocyanates Chemical class 0.000 title claims abstract description 50
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000007788 liquid Substances 0.000 claims abstract description 144
- 239000007787 solid Substances 0.000 claims abstract description 86
- 239000002245 particle Substances 0.000 claims abstract description 74
- 238000006243 chemical reaction Methods 0.000 claims abstract description 65
- 238000000034 method Methods 0.000 claims abstract description 52
- 238000002309 gasification Methods 0.000 claims abstract description 29
- -1 amine compound Chemical class 0.000 claims abstract description 27
- 239000011344 liquid material Substances 0.000 claims abstract description 25
- YGYAWVDWMABLBF-UHFFFAOYSA-N Phosgene Chemical compound ClC(Cl)=O YGYAWVDWMABLBF-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000012442 inert solvent Substances 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims description 54
- 239000012071 phase Substances 0.000 claims description 24
- 230000008569 process Effects 0.000 claims description 21
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims description 17
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 9
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 9
- 239000007791 liquid phase Substances 0.000 claims description 9
- 229920000768 polyamine Polymers 0.000 claims description 8
- RFFLAFLAYFXFSW-UHFFFAOYSA-N 1,2-dichlorobenzene Chemical compound ClC1=CC=CC=C1Cl RFFLAFLAYFXFSW-UHFFFAOYSA-N 0.000 claims description 6
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 4
- 229920006389 polyphenyl polymer Polymers 0.000 claims description 4
- 238000010992 reflux Methods 0.000 claims description 4
- RELMFMZEBKVZJC-UHFFFAOYSA-N 1,2,3-trichlorobenzene Chemical compound ClC1=CC=CC(Cl)=C1Cl RELMFMZEBKVZJC-UHFFFAOYSA-N 0.000 claims description 3
- OCJBOOLMMGQPQU-UHFFFAOYSA-N 1,4-dichlorobenzene Chemical compound ClC1=CC=C(Cl)C=C1 OCJBOOLMMGQPQU-UHFFFAOYSA-N 0.000 claims description 3
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 claims description 3
- RNLHGQLZWXBQNY-UHFFFAOYSA-N 3-(aminomethyl)-3,5,5-trimethylcyclohexan-1-amine Chemical compound CC1(C)CC(N)CC(C)(CN)C1 RNLHGQLZWXBQNY-UHFFFAOYSA-N 0.000 claims description 3
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 3
- YMHQVDAATAEZLO-UHFFFAOYSA-N cyclohexane-1,1-diamine Chemical compound NC1(N)CCCCC1 YMHQVDAATAEZLO-UHFFFAOYSA-N 0.000 claims description 3
- 229940117389 dichlorobenzene Drugs 0.000 claims description 3
- JLVWYWVLMFVCDI-UHFFFAOYSA-N diethyl benzene-1,3-dicarboxylate Chemical compound CCOC(=O)C1=CC=CC(C(=O)OCC)=C1 JLVWYWVLMFVCDI-UHFFFAOYSA-N 0.000 claims description 3
- ZZTCPWRAHWXWCH-UHFFFAOYSA-N diphenylmethanediamine Chemical compound C=1C=CC=CC=1C(N)(N)C1=CC=CC=C1 ZZTCPWRAHWXWCH-UHFFFAOYSA-N 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 229910000856 hastalloy Inorganic materials 0.000 claims description 3
- NTNWKDHZTDQSST-UHFFFAOYSA-N naphthalene-1,2-diamine Chemical compound C1=CC=CC2=C(N)C(N)=CC=C21 NTNWKDHZTDQSST-UHFFFAOYSA-N 0.000 claims description 3
- DYFXGORUJGZJCA-UHFFFAOYSA-N phenylmethanediamine Chemical compound NC(N)C1=CC=CC=C1 DYFXGORUJGZJCA-UHFFFAOYSA-N 0.000 claims description 3
- 239000008096 xylene Substances 0.000 claims description 3
- MVPPADPHJFYWMZ-IDEBNGHGSA-N chlorobenzene Chemical group Cl[13C]1=[13CH][13CH]=[13CH][13CH]=[13CH]1 MVPPADPHJFYWMZ-IDEBNGHGSA-N 0.000 claims 1
- 229910001220 stainless steel Inorganic materials 0.000 claims 1
- 239000010935 stainless steel Substances 0.000 claims 1
- 238000002360 preparation method Methods 0.000 abstract description 7
- 239000007789 gas Substances 0.000 description 19
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 12
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 11
- 239000000047 product Substances 0.000 description 11
- 239000004202 carbamide Substances 0.000 description 10
- 150000001263 acyl chlorides Chemical class 0.000 description 9
- 239000012295 chemical reaction liquid Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 238000005192 partition Methods 0.000 description 9
- 239000000126 substance Substances 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 6
- 239000006227 byproduct Substances 0.000 description 6
- 150000001875 compounds Chemical class 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000005194 fractionation Methods 0.000 description 5
- 230000002035 prolonged effect Effects 0.000 description 5
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 4
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 4
- 238000006552 photochemical reaction Methods 0.000 description 4
- 239000007795 chemical reaction product Substances 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 230000000903 blocking effect Effects 0.000 description 2
- 239000012043 crude product Substances 0.000 description 2
- 238000004811 liquid chromatography Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- NGNBDVOYPDDBFK-UHFFFAOYSA-N 2-[2,4-di(pentan-2-yl)phenoxy]acetyl chloride Chemical compound CCCC(C)C1=CC=C(OCC(Cl)=O)C(C(C)CCC)=C1 NGNBDVOYPDDBFK-UHFFFAOYSA-N 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 125000001951 carbamoylamino group Chemical group C(N)(=O)N* 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000003840 hydrochlorides Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000004020 luminiscence type Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000010517 secondary reaction Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C263/00—Preparation of derivatives of isocyanic acid
- C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C263/00—Preparation of derivatives of isocyanic acid
- C07C263/18—Separation; Purification; Stabilisation; Use of additives
- C07C263/20—Separation; Purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2601/00—Systems containing only non-condensed rings
- C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
- C07C2601/14—The ring being saturated
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to the technical field of isocyanate, and provides a method for preparing isocyanate and an isocyanate preparation system. The method comprises the following steps: (1) Classifying a mixed stream obtained by cold light gasification reaction of an amine compound and phosgene in the presence of an inert solvent to divide the mixed stream into a gas phase stream, a light liquid stream and a heavy liquid stream, wherein the light liquid stream contains light solid particles, the heavy liquid stream contains heavy solid particles, and the density of the light solid particles is smaller than that of the heavy solid particles; (2) And feeding the light liquid material flow into the rectifying tower from a position between a stripping section and a rectifying section of the rectifying tower, and obtaining isocyanate products at the tower bottom of the rectifying tower.
Description
Technical Field
The invention relates to the technical field of isocyanate, in particular to a method for preparing isocyanate and an isocyanate preparation system.
Background
The isocyanate molecular structure has functional groups of-NCO, and at present, the phosgenation method is mainly adopted at home and abroad to produce the substances. Under the corresponding temperature and pressure conditions, the amine compound, phosgene and inert solvent are mixed to obtain photochemical reaction liquid containing isocyanate and hydrogen chloride, the inert solvent and the phosgene in the photochemical reaction liquid are separated to obtain an isocyanate crude product, and the crude product is separated to obtain the isocyanate product.
The reaction of amine compounds with phosgene to give isocyanates requires two intermediate steps, the so-called "cold phosgenation" and "hot phosgenation" processes. The first step is to form isocyanate precursor acyl chloride and hydrochloride substance by amine compound and excessive phosgene at low temperature, namely 'cold light gasification' reaction; in the second step the isocyanate precursor is decomposed at high temperature into isocyanate and hydrogen chloride, i.e. "hot phosgenation". In cold gasification, generally lower temperatures are used, for example temperatures below 60 ℃, in the case of hot phosgenation temperatures of from 100 ℃ to 200 ℃ are usually reached.
In the process of producing isocyanate by reacting amine compounds with phosgene, as is well known in the art, solid substances such as acyl chlorides and hydrochlorides produced by normal cold reaction, and part of urea byproducts are produced due to poor mass transfer effect, and the substances are also solids. The substances can be directly deposited in the reactor in the thermal reaction process, and can be further catalyzed to generate more solid byproducts, so that the solids cannot be decomposed and finally are deposited in the reaction and solvent separation system, and the substances are required to be shut down and cleaned after running for a certain time, so that the production cost is greatly increased, and the production efficiency is greatly influenced.
Chinese patent CN 107787318B discloses a process for the preparation of isocyanates by passing the product stream obtained after the reaction of an amine compound with phosgene through reactors in series, separating hydrogen chloride generated during the "hot phosgenation" reaction by depressurization to promote the decomposition of the isocyanate precursor. The method only adopts a balance moving mode, has the defect of low decomposition rate, and the reactors connected in series are required to increase equipment and operation investment.
Chinese patent application CN 114787125A discloses a process for the preparation of isocyanates, which process designs the acid chloride decomposition reactor as a bubble column or tray column.
Chinese patent CN 113831262B discloses a method for preparing isocyanate by continuous phosgenation, the method divides the phosgenation process into two stages, a solid separation device is added at the outlet of the second stage phosgenation reaction device, the second stage photochemical reaction liquid is separated to obtain a reaction liquid containing no solid matter and a reaction liquid containing solid matter, the reaction liquid containing no solid matter enters the next stage process, and the reaction liquid containing solid matter is returned to the first photochemical reaction device after being broken and dispersed. The method separates the secondary reaction liquid, and can solve the problem that solid deposition affects long-period stable operation in post-treatment processes such as dephosgene, solvent separation and the like to a certain extent. However, the solids are mainly concentrated at the cold reaction outlet and the initial stage of the thermal reaction in the whole phosgenation reaction process, and the solids easily cause scaling and blocking of the thermal reaction system, so that the heat input and the running stability of equipment are affected. This patent does not describe a solid particle treatment scheme at this stage.
Disclosure of Invention
The invention provides a method for preparing isocyanate and an isocyanate preparation system, wherein the method for preparing isocyanate can obviously improve the problem of system blockage, can effectively prolong the operation period of a reactor in a hot phosgenation reaction, and is beneficial to prolonging the operation period of a post-treatment system.
The invention provides the following technical scheme for achieving the purpose:
the present invention provides a process for preparing isocyanates, comprising the steps of:
(1) Classifying a mixed stream obtained by cold light gasification reaction of an amine compound and phosgene in the presence of an inert solvent to divide the mixed stream into a gas phase stream, a light liquid stream and a heavy liquid stream, wherein the light liquid stream contains light solid particles, the heavy liquid stream contains heavy solid particles, and the density of the light solid particles is smaller than that of the heavy solid particles;
(2) And feeding the light liquid material flow into the rectifying tower from a position between a stripping section and a rectifying section of the rectifying tower, and obtaining isocyanate products at the tower bottom of the rectifying tower.
In some embodiments, in step (1), the density of the heavy solid particles is 1.15-1.30 g/cm 3 Preferably 1.18 to 1.25 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the light solid particles is 0.95-1.12 g/cm 3 Preferably 1.02 to 1.10 g/cm 3 。
In some embodiments, in step (1), the residence time of the liquid phase stream in the mixed stream in the classification device performing the classification treatment is 1 to 10min, preferably 3 to 6min;
the pressure of the classifying device is, for example, 0MPag to 0.5MPag, preferably 0.1 MPag to 0.3MPag.
In some embodiments, in step (1), the light liquid stream is 10% -50% by mass of the mixed stream; the mass percentage of the heavy liquid material flow in the mixed material flow is 40% -85%; the mass percentage of the gas phase material flow in the mixed material flow is 1.5% -10%.
In some embodiments, the classifying treatment is performed in a classifying device that separates light and heavy solid particles in a feed liquid based on a density difference principle;
preferably, the grading device comprises a kettle body, wherein the inner cavity of the kettle body is divided into a first material liquid groove, a second material liquid groove, a buffer area and a third material liquid groove which are adjacent in sequence, the first material liquid groove is provided with a mixed material inflow port, the second material liquid groove is provided with an overflow port for overflow of upper material liquid in the first material liquid groove into the second material liquid groove, a lower liquid flow channel capable of communicating the first material liquid groove with the buffer area is formed between the outer wall of the lower part of the second material liquid groove and the inner wall of the kettle body, and the third material liquid groove is provided with an overflow port for overflow of upper material liquid in the buffer area into the third material liquid groove; the bottom of the second liquid tank is provided with a light liquid material outflow opening, and the bottom of the third liquid tank is provided with a heavy liquid material outflow opening; the kettle body is provided with a gas phase outlet for discharging gas phase material flow escaping from the inner cavity of the kettle body.
In some embodiments, in the step (2), the theoretical plate number of the rectifying section of the rectifying tower is 3-8, preferably 4-5; the theoretical plate number of the stripping section of the rectifying tower is 13-25, preferably 15-20;
preferably, the tower body material of the rectifying tower is hastelloy or 316L.
In some embodiments, the temperature of the tower bottom of the rectifying tower is 120-190 ℃; the tower top pressure is 0 MPag-0.5 MPag; the reflux ratio is 0.2 to 2.0, preferably 1 to 1.2.
In some embodiments, in step (1), the inert solvent comprises one or more of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, diethyl isophthalate, preferably chlorobenzene and/or o-dichlorobenzene;
in some embodiments, the amine-based compound comprises one or more of diaminodiphenylmethane, polymethylene polyphenyl polyamine, diaminotoluene, isophorone diamine, hexamethylene diamine, cyclohexane diamine, p-phenylene diamine, naphthalene diamine;
in some embodiments, the mass ratio of phosgene to amine compound is from 1 to 10;
in some embodiments, the mass ratio of the amine compound to the inert solvent is 1 (1-6).
The present invention also provides an isocyanate production system for carrying out the process described above, the system comprising:
classification means for classifying a mixed stream obtained by the cold light gasification reaction to separate a gas phase stream, a light liquid stream containing the light solid particles and a heavy liquid stream containing the heavy solid particles from the mixed stream; the mixed material flow is obtained by cold light gasification reaction of amine compounds and phosgene in the presence of inert solvents;
and the rectifying tower is used for receiving the light liquid material flow and the heavy liquid material flow and carrying out thermal phosgenation reaction to generate isocyanate, the feeding position of the light liquid material flow of the rectifying tower is arranged at the tower kettle of the rectifying tower, and the feeding position of the heavy liquid material flow of the rectifying tower is arranged between the stripping section and the rectifying section of the rectifying tower.
In some embodiments, the classifying device is a classifying device for separating light and heavy solid particles in a feed liquid based on a density difference principle.
The technical scheme provided by the invention has the following beneficial effects:
according to the invention, the classification process of solid particles in the mixed feed liquid obtained by the cold gasification reaction is added on the basis of the conventional process of preparing isocyanate by the phosgenation reaction, urea substances which are easy to block and aggravate side reaction are separated, so that the residence time of the urea substances on a tray is reduced, the blocking risk of the reaction feed liquid in the heat treatment process is reduced, the stable operation period of a reaction device can be prolonged, and the quality of isocyanate products is improved.
The method is adopted to prepare isocyanate, the mixed feed liquid obtained by cold light gasification reaction is firstly subjected to classification treatment, and then the heavy liquid material flow and the light liquid material flow obtained by classification are fed into the reaction rectifying tower at specific feeding positions to carry out the thermal light gasification reaction, so that the problem of blockage of the tower reactor can be effectively solved, compared with the prior art, the method has the advantages of simple process, effective shortening of production flow, contribution to improving of raw material conversion rate, prolonged operation period of the tower reactor, contribution to reducing of pressure drop of the whole tower and contribution to reduction of production cost.
Drawings
FIG. 1 is a schematic diagram of an isocyanate production system in one embodiment;
FIG. 2 is a schematic diagram of a classification apparatus in one embodiment.
Reference numerals illustrate: a mixture inflow port 1, a gas phase outlet 2, a light liquid outflow port 3, a heavy liquid outflow port 4, a mixture stream 5, a gas phase stream 6, a heavy liquid stream 7, a light liquid stream 8, a column bottom 11, a stripping section 12, a rectifying section 13, a first partition 14, a second partition 15, a third partition 16, a first liquid tank 17, a second liquid tank 18, a buffer area 19, a third liquid tank 20, a column body 100, a classification device 200, and a rectifying column 300.
Detailed Description
In order that the invention may be readily understood, a further description of the invention will be provided with reference to the following examples. It should be understood that the following examples are only for better understanding of the present invention and are not meant to limit the present invention to the following examples.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The term "and/or" as may be used herein includes any and all combinations of one or more of the associated listed items.
Where specific experimental steps or conditions are not noted in the examples, they may be performed according to the operations or conditions of the corresponding conventional experimental steps in the art. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Terms of orientation such as up, down, left, right, front, rear, front, back, top, bottom, etc. mentioned or possible to be mentioned in the present specification are defined with respect to the configurations shown in the drawings, which are relative concepts, and thus may be changed according to different positions and different use states thereof. The words "inner" and "outer" refer to directions toward or away from, respectively, the geometric center of a particular component. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In one aspect, the present invention provides a process for preparing an isocyanate, the process comprising the steps of:
(1) Classifying a mixed stream 5 (a reaction liquid containing acyl chloride and hydrochloride substances) obtained by cold light gasification reaction of amine compounds and phosgene in the presence of an inert solvent, so that the mixed stream 5 is divided into a gas phase stream 6, a light liquid stream 8 and a heavy liquid stream 7, wherein the light liquid stream 8 contains light solid particles, the heavy liquid stream 7 contains heavy solid particles, and the density of the light solid particles is less than that of the heavy solid particles; wherein the main components in the gas phase stream 6 are HCl and phosgene;
(2) The light liquid stream 8 is fed to the bottom 11 of the rectifying column 300 for carrying out the thermal phosgenation reaction, the heavy liquid stream 7 is fed to the rectifying column 300 from a position between the stripping section 12 and the rectifying section 13 of the rectifying column 300, and an isocyanate product, mainly a mixed product of isocyanate and an inert solvent, is obtained in the bottom 11 of the rectifying column 300.
The present inventors have found during the course of the study that the solid particles produced after the reaction of an amine compound and phosgene can be classified into two types according to their densities, namely, light solid particles having a smaller density and heavy solid particles having a larger density. Wherein the density of the light solid particles is less than the liquid phase density of the mixed stream and the density of the heavy solid particles is greater than the liquid phase density of the mixed stream. In the invention, a mixed stream 5 obtained by cold light gasification reaction is firstly subjected to grading treatment and is separated into a gas phase stream 6, a light liquid stream 8 and a heavy liquid stream 7 before entering a hot light gasification reaction stage, wherein the light liquid stream 8 is a feed liquid enriched with light solid particles (mainly containing urea byproducts and mainly containing isocyanate-amine compound containing ureido groups), and the heavy liquid stream 7 is a feed liquid enriched with heavy solid particles (mainly containing acyl chloride, hydrochloride and compound of acyl chloride and hydrochloride); the inventor finds that the light liquid stream 8 is sent to the tower kettle 11 of the rectifying tower 300 in the thermal phosgenation reaction stage, and the heavy liquid stream 7 is sent to the position between the stripping section 12 and the rectifying section 13 of the rectifying tower 300, so that the problems of fouling, scaling and the like of the rectifying tower can be obviously improved, the raw material conversion rate can be improved, the operating period of the rectifying tower can be effectively prolonged, and the operating period of a downstream post-treatment system can be further prolonged.
Preferably, in the step (1), the density of the heavy solid particles is 1.15-1.30 g/cm 3 For example 1.15 g/cm 3 、1.16g/cm 3 、1.18 g/cm 3 、1.20 g/cm 3 、1.23g/cm 3 、1.25 g/cm 3 、1.28 g/cm 3 Or 1.30 g/cm 3 Preferably 1.18 to 1.25 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the light solid particles is 0.95-1.12 g/cm 3 For example 0.95g/cm 3 、0.98g/cm 3 、1.00 g/cm 3 、1.02 g/cm 3 、1.05 g/cm 3 、1.10g/cm 3 Or 1.12g/cm 3 Preferably 1.02 to 1.10 g/cm 3 . The mixed stream 5 is subjected to classification treatment to obtain a heavy liquid stream 7 enriched with the heavy solid particles with the preferred density and a light liquid stream 8 enriched with the light solid particles with the preferred density, so that urea byproducts and other solid particles are thoroughly separated, wherein the urea byproducts are enriched in the light liquid stream 8, the heavy solid particles (mainly comprising acyl chloride, hydrochloride and a compound of the acyl chloride and the hydrochloride) are enriched in the heavy liquid stream 7, and the light liquid stream 8 enriched with the light solid particles with the density and the heavy liquid stream 7 enriched with the heavy solid particles with the density are fed into the rectifying tower 300 according to the specific feeding position of the invention for carrying out thermal phosgenation reaction, thereby being beneficial to further improving the anti-blocking effect of a reaction device and further improving the quality of isocyanate products.
The inventor finds that light solid particles contained in a mixed stream obtained by the cold light gasification reaction are main reasons for fouling and scaling of a tower reactor in the hot light gasification reaction, the main components of the light solid particles are isocyanate-amine compounds containing urea groups, and the light solid particles are difficult to dissolve in an inert solvent due to strong hydrogen bond interaction among the urea groups in the hot light gasification reaction; in the invention, the light liquid material flow 8 rich in light solid particles enters the thermal phosgenation reaction stage in a mode of being sent into the tower kettle 11 of the rectifying tower 300, so that the possibility of reactor siltation and scaling caused by light solid impurity particles can be greatly reduced; in the invention, a heavy liquid material flow 7 rich in heavy solid particles is sent between a rectifying section 13 and a stripping section 12 of a rectifying tower 300, and the main components of the heavy solid particles are acyl chloride, hydrochloride and a compound of the acyl chloride and the hydrochloride, and the heavy solid particles are dissolved step by step and are completely dissolved in a mixed material flow in the thermal phosgenation reaction process; by the specific feeding mode of the light liquid material flow 8 and the heavy liquid material flow 7 in the thermal phosgenation reaction stage, the problem of blockage of the tower reactor can be effectively solved, and the conversion rate of raw materials can be improved.
Preferably, in the step (1), the residence time of the liquid phase stream in the mixed stream 5 in the classification device 200 is 1 to 10min, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10min, and preferably 3 to 6min, when the classification treatment is performed. The preferred residence time is used to facilitate the enrichment of light solid particles of a target density in the light liquid stream 8 and heavy solid particles of a target density in the heavy liquid stream 7 during classification, to further extend the reactor run length and to further improve the isocyanate product quality. The operating pressure of the classifying device 200 is, for example, 0MPag to 0.5Mpa, for example, 0.1, 0.2, 0.3, 0.4, 0.5Mpa, etc., preferably 0.1 MPag to 0.3 Mpa.
In some preferred embodiments, in step (1), the density of the heavy solid particles is 1.15-1.30 g/cm 3 The density of the light solid particles is 0.95-1.12 g/cm 3 And the residence time of the liquid phase material flow in the classifying device 200 is 1-10 min, so that the operation period of the rectifying tower 300 can be further prolonged, and the product quality can be improved. In a more preferred embodiment, in the step (1), the density of the heavy solid particles is 1.18-1.25 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the light solid particles is 1.02-1.10 g/cm 3 And the residence time of the liquid phase material flow in the classifying device 200 is preferably 3-6 min, which is beneficial to remarkably improving the running period and the product quality of the rectifying tower 300.
In some embodiments, in step (1), after the classification treatment of the classification device 200, the light liquid stream 8 has a mass percentage of 10% -50%, for example, 10%, 20%, 30%, 40% or 50%, etc., in the mixed stream 5;
after the classification treatment by the classification device 200, the mass percentage of the heavy liquid stream 7 in the mixed stream 5 is 40% -85%, for example 40%, 50%, 60%, 70%, 80% or 85%, etc., for example 50% -85%;
the mass percentage of the gas phase stream 6 in the mixed stream 5 is 1.5% -10%, for example 1.5%, 2%, 4%, 6%, 8% or 10%, etc.
In step (1), the mixed stream 5 may be specifically fed to the classification apparatus 200 by a pump for classification treatment. Further, the classification treatment is performed in a classification device for separating light and heavy solid particles based on the density difference principle, and the classification treatment of the mixed stream can be performed directly by using a device capable of classifying light and heavy solid particles in a feed liquid by the density difference principle, which is known in the art.
In some embodiments, the classification device 200 shown in fig. 2 may be used to perform classification treatment of a mixed material flow, specifically, for example, the classification device 200 includes a tank body 100, an inner cavity of the tank body 100 is divided into a first material liquid tank 17, a second material liquid tank 18, a buffer area 19 and a third material liquid tank 20 that are adjacent in sequence, the first material liquid tank 17 is provided with a mixed material liquid inlet 1, the second material liquid tank 18 is provided with an overflow port for overflow of an upper material liquid in the first material liquid tank 17 into the second material liquid tank 18, a lower liquid flow channel capable of communicating the first material liquid tank 17 and the buffer area 19 is formed between an outer wall of a lower portion of the second material liquid tank 18 and an inner wall of the tank body 100, that is, a lower liquid flow channel capable of enabling a lower portion or bottom material liquid in the first material liquid tank 17 to enter the buffer area 19 through a lower liquid flow channel indicated by a dashed arrow in fig. 1, and the third material liquid tank 20 is provided with an overflow port for overflow of an upper material liquid in the buffer area 19 into the third material liquid tank 20; the bottom of the second liquid tank 18 is provided with a light liquid material outflow opening 3, and the bottom of the third liquid tank 20 is provided with a heavy liquid material outflow opening 4; the tank body 100 is provided with a gas phase outlet 2 for discharging a gas phase stream escaping from the inner cavity of the tank body 100. Specifically, for example, the inner cavity of the kettle body is divided into a first material liquid tank 17, a second material liquid tank 18, a buffer area 19 and a third material liquid tank 20 which are sequentially adjacent by a plurality of partition boards, and taking fig. 1 as an example, the partition boards comprise a first partition board 14, a second partition board 15 and a third partition board 16; specifically, for example, the lower portion of the second liquid tank 18 is narrowed as compared to the upper portion, so that a free space is formed between the outer wall of the lower portion of the second liquid tank 18 and the inner wall of the lower portion of the tank body 100, thereby allowing a lower liquid flow passage through which a lower liquid flow can pass; a gap is formed between the top of the second partition 15 and the top of the tank body 100 so that the gas phase can pass through and enter the gas phase outlet 2; in the example of fig. 2, the height of the third baffle 16 is less than the height of the first baffle 14. Fig. 2 shows only an example of a classification device 200, and other devices capable of classifying light and heavy solid particles in a feed liquid by using a density difference principle can be used to perform classification treatment on the mixed stream 5.
In a preferred embodiment, in the step (2), the theoretical plates of the rectifying section 13 of the rectifying tower 300 are 3 to 8, preferably 4 to 5; the theoretical plate number of the stripping section 12 of the rectifying tower 300 is 13-25, preferably 15-20. The stripping section 12 of the rectifying tower 300 simultaneously realizes the reaction and stripping functions. The adoption of the optimized rectifying tower parameters is beneficial to further improving the reaction effect and the anti-blocking effect and is beneficial to obtaining a better equipment operation period.
Preferably, the material of the column body of the rectifying column 300 is hastelloy or 316L.
In a preferred embodiment, the temperature of the rectifying tower 300 is 120 ℃ to 190 ℃, for example, 120, 130, 150, 170, 190 ℃, etc.; the tower top pressure is 0MPag to 0.5MPag, for example, 0.1, 0.3, 0.5Mpag and the like; the reflow ratio is 0.2 to 2.0, for example, 0.2, 0.5, 1, 1.5, 2.0, etc., preferably 1 to 1.2.
In some embodiments, it will be advantageous to obtain more excellent performance by conducting the isocyanate preparation under a combination of the above-mentioned preferred conditions.
In some embodiments, the amine compound comprises one or more of diaminodiphenylmethane, polymethylene polyphenyl polyamine, diaminotoluene, isophorone diamine, hexamethylene diamine, cyclohexane diamine, p-phenylene diamine, naphthalene diamine.
In some embodiments, the inert solvent comprises one or more of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, diethyl isophthalate, preferably chlorobenzene and/or o-dichlorobenzene. The mass ratio of the amine compound to the inert solvent is, for example, 1 (1 to 6), preferably 1 (2.5 to 5), more preferably 1 (3 to 4), for example, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5 or 1:5.5. In some embodiments, the mass ratio of phosgene to amine compound is from 1 to 10, such as 1, 2, 4, 6, 8, 10, etc.
In the present invention, the cold gasification reaction in the step (1) may be performed by a conventional process in the art, which is not particularly limited. For example, amine compounds and solvents are mixed in a static mixer, and mixed solution of phosgene and solvents is mixed in a dynamic mixer for adiabatic reaction, so as to obtain a cold light gasification reaction product. Preferably, the temperature of the cold light gasification reaction product is 60-140 ℃; preferably, the pressure of the cold light gasification reaction is 1-30 barg.
The reaction process of the luminescence gasification reaction can be carried out, for example, with reference to patent application CN115925581 a. The main improvement of the present invention over the prior art is that the mixed stream obtained in the cold light gasification reaction is staged before entering the hot light gasification reaction.
The present invention provides an isocyanate production system for carrying out the process described above, see fig. 1, said system comprising:
a fractionation device 200 for fractionation of a mixed stream 5 obtained by the cold gasification reaction to separate a gas phase stream 6, a light liquid stream 8 containing the light solid particles and a heavy liquid stream 7 containing the heavy solid particles from the mixed stream 5; wherein the mixed material flow 5 is obtained by cold light gasification reaction of amine compounds and phosgene in the presence of inert solvent;
the rectifying tower 300 is configured to receive the light liquid stream 8 and the heavy liquid stream 7 and perform a thermal phosgenation reaction to generate isocyanate, a feeding position of the light liquid stream 8 of the rectifying tower 300 is disposed at a tower bottom 11 of the rectifying tower 300, and a feeding position of the heavy liquid stream of the rectifying tower 300 is disposed between a stripping section 12 and a rectifying section 13 of the rectifying tower 300.
Further, the classifying device 200 is a classifying device for separating light and heavy solid particles based on the principle of density difference. In some embodiments, for example, the apparatus shown in fig. 2 is used as the classifying apparatus, and the description of the classifying apparatus shown in fig. 2 is referred to in the foregoing description, and will not be repeated.
The following further illustrates the inventive arrangements by way of specific examples, but it should not be construed that the scope of the invention is limited thereto.
In the following examples and comparative examples, methods for detecting the density of heavy solid particles in heavy liquid stream 7 and the density of light liquid solid particles in light liquid stream 8: after sampling either the heavy liquid stream 7 or the light liquid stream 8 for filtration, the density was determined by drainage.
In the following examples and comparative examples, the reaction effect was represented by the content of the urea-based compound as a by-product in the bottom liquid of the rectifying column (the smaller the urea-based compound content, the better the reaction quality).
The determination method of the urea compound comprises the following steps: the liquid chromatography is adopted for measurement, a liquid chromatography instrument is Shimadzu LC-20A, a SIL-20A autosampler, a CT0-20A column incubator, an SPD-M20A detector and a chromatographic column of ODSP (250 x 4.6 mm) (Inertsil) with the thickness of 5 μm.
A schematic diagram of the isocyanate production system in the following example is shown in FIG. 1, and a classification apparatus 200 is used as shown in FIG. 2. In the following examples and comparative examples, the process of generating a mixture stream by the phosgenation reaction of an amine compound with phosgene in the solvent chlorobenzene is illustrated as follows:
mixing solvent chlorobenzene and methylene crosslinked polyamine (hereinafter referred to as polyamine) in a static mixer to generate a mixed solution, mixing phosgene and the mixed solution in a dynamic mixer, and then performing adiabatic cold light gasification reaction under the reaction pressure of 1-30 barg and the temperature of a cold reaction product of 60-140 ℃. After the reaction, a mixed stream, i.e. mixed stream 5 in fig. 1, was obtained for further processing in the subsequent examples and comparative examples.
Wherein the methylene crosslinked polyamine of the polyphenylmethane series is: and (3) producing the smoke table MDI device in the smoke table Wanhua industrial park. The mass ratio of chlorobenzene to methylene crosslinked polyphenyl methane series polyamine is 1.0-4.0. The mass ratio of phosgene to polyamine is 1.0-5.0.
Example 1
The mixed stream 5 is pumped from the mixed stream inlet 1 to the classifying device 200 for classification treatment, the pressure in the inner cavity of the classifying device 200 is 0.12MPag, and the residence time of the liquid phase stream in the mixed stream 5 in the classifying device 200For 5min. A light liquid stream 8 flows out from the light liquid stream outlet 3, a heavy liquid stream 7 flows out from the heavy liquid stream outlet 4, and a gas phase stream 6 is discharged from the gas phase outlet 2. The light liquid stream 8 obtained after fractionation had a mass ratio of 35% in the mixed stream 5, the heavy liquid stream 7 obtained after fractionation had a mass ratio of 62% in the mixed stream 5, and the gas phase stream 6 obtained after fractionation had a mass ratio of 3% in the mixed stream 5. Wherein the density of the heavy solid particles in the heavy liquid stream 7 is 1.23 g/cm 3 The density of the light solid particles in the light liquid stream 8 was 1.05 g/cm 3 . Referring to fig. 1, the light liquid stream 8 obtained in the above step is fed to the bottom 11 of the rectifying column 300, and the heavy liquid stream 7 is fed to the first stage theoretical plate between the rectifying section 13 and the stripping section 12 of the rectifying column 300. The theoretical plate number of the rectifying section 13 is 5; the theoretical plate number of the stripping section 12 is 21, and the column body material of the rectifying column 300 is 316L.
The temperature of the column bottom 11 of the rectifying column 300 is 155 ℃; the pressure at the top of the column is 0.4 MPag; the overhead temperature was 95℃and the reflux ratio was 1.2.
The isocyanate production was performed according to this example, and the operational lifetime of the rectifying column 300 reached 779 days (no clogging/scaling occurred during this period, resulting in the need for shut down for dredging or unblocking).
Examples 2-3 and comparative examples 1-2
Examples 2-3 and comparative examples 1-2 were each carried out with reference to example 1, with the only difference that: the light solid particle density in the light liquid stream 8 obtained after classification, the heavy solid particle density in the heavy liquid stream 7 obtained after classification, and the residence time of the liquid stream in the mixed stream 5 in the classification apparatus 200 when the classification treatment of the mixed stream 5 is performed in the classification apparatus 200 are different in terms of parameters, specifically, see table 1.
TABLE 1
Note that the "rectifying column operation cycle" described in table 1 refers to the duration of continuous operation of the rectifying column, and the condition that no clogging/scaling occurs during the period, and thus, the production is stopped for dredging or dredging.
Comparative example 3
Reference example 1 was performed with the difference that: in comparative example 3, the mixed stream produced in the cold gasification reaction was directly pumped into the first stage theoretical plate between the rectifying section and stripping section of the rectifying column.
According to the preparation of the isocyanate in the comparative example, the service life of the rectifying tower is shortened to 274 days, and the urea content in the tower bottom liquid of the rectifying tower is 2634ppm.
It will be readily appreciated that the above embodiments are merely examples given for clarity of illustration and are not meant to limit the invention thereto. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (15)
1. A process for preparing an isocyanate, said process comprising the steps of:
(1) Classifying a mixed stream obtained by cold light gasification reaction of an amine compound and phosgene in the presence of an inert solvent to divide the mixed stream into a gas phase stream, a light liquid stream and a heavy liquid stream, wherein the light liquid stream contains light solid particles, the heavy liquid stream contains heavy solid particles, and the density of the light solid particles is smaller than that of the heavy solid particles; the density of the heavy solid particles is 1.15-1.30 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the light solid particles is 0.95-1.12 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The classification treatment is carried out in a classification device for separating light and heavy solid particles in feed liquid based on a density difference principle, and the residence time of a liquid phase material flow in the mixed material flow in the classification device is 1-10 min;
(2) And feeding the light liquid material flow into the rectifying tower from a position between a stripping section and a rectifying section of the rectifying tower, and obtaining isocyanate products at the tower bottom of the rectifying tower.
2. The method of claim 1, wherein in step (1), the density of the heavy solid particles is 1.18-1.25 g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The density of the light solid particles is 1.02-1.10 g/cm 3 。
3. The method according to claim 2, wherein in the step (1), a residence time of the liquid phase stream in the mixed stream in a classification device for performing the classification treatment is 3 to 6 minutes.
4. The method of claim 3, wherein the pressure of the classifying device is 0mpag to 0.5mpag.
5. The method of claim 4, wherein the pressure of the classifying device is 0.1 mpag to 0.3mpag.
6. The method of claim 1, wherein in step (1), the light liquid stream is present in the mixed stream in an amount of 10% to 50% by mass;
the mass percentage of the heavy liquid material flow in the mixed material flow is 40% -85%;
the mass percentage of the gas phase material flow in the mixed material flow is 1.5% -10%.
7. The method according to any one of claims 1 to 6, wherein the classifying device comprises a tank body, an inner cavity of the tank body is divided into a first liquid tank, a second liquid tank, a buffer area and a third liquid tank which are adjacent in sequence, a mixture inflow port is arranged in the first liquid tank, an overflow port for overflow of upper layer liquid in the first liquid tank into the second liquid tank is arranged in the second liquid tank, a lower liquid flow channel capable of communicating the first liquid tank with the buffer area is formed between an outer wall of the lower part of the second liquid tank and an inner wall of the tank body, and an overflow port for overflow of upper layer liquid in the buffer area into the third liquid tank is arranged in the third liquid tank; the bottom of the second liquid tank is provided with a light liquid material outflow opening, and the bottom of the third liquid tank is provided with a heavy liquid material outflow opening; the kettle body is provided with a gas phase outlet for discharging gas phase material flow escaping from the inner cavity of the kettle body.
8. The method according to any one of claims 1 to 6, wherein in the step (2), the theoretical plates of the rectifying section of the rectifying column are 3 to 8; the theoretical plate number of stripping sections of the rectifying tower is 13-25.
9. The method according to claim 8, wherein in the step (2), the theoretical plates of the rectifying section of the rectifying tower are 4-5;
the theoretical plate number of stripping sections of the rectifying tower is 15-20.
10. The method according to claim 8, wherein the column body material of the rectifying column is hastelloy or 316L stainless steel.
11. The method according to claim 8, wherein the temperature of the rectifying column bottom is 120 ℃ to 190 ℃; the tower top pressure is 0 MPag-0.5 MPag; the reflux ratio is 0.2-2.0.
12. The method of claim 11, wherein the reflux ratio is 1-1.2.
13. The process of any one of claims 1-6, wherein in step (1), the inert solvent comprises one or more of chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, benzene, diethyl isophthalate;
and/or the amine compound comprises one or more of diaminodiphenylmethane, polymethylene polyphenyl polyamine, diaminotoluene, isophorone diamine, hexamethylenediamine, cyclohexanediamine, p-phenylenediamine and naphthalene diamine;
and/or the mass ratio of the phosgene to the amine compound is 1-10;
and/or the mass ratio of the amine compound to the inert solvent is 1 (1-6).
14. The process according to claim 13, wherein in step (1), the inert solvent is chlorobenzene and/or o-dichlorobenzene.
15. An isocyanate production system for carrying out the process according to any one of claims 1 to 14, characterized in that it comprises:
classification means for classifying a mixed stream obtained by the cold light gasification reaction to separate a gas phase stream, a light liquid stream containing the light solid particles and a heavy liquid stream containing the heavy solid particles from the mixed stream; the mixed material flow is obtained by cold light gasification reaction of amine compounds and phosgene in the presence of inert solvents;
the rectifying tower is used for receiving the light liquid material flow and the heavy liquid material flow and carrying out thermal phosgenation reaction to generate isocyanate, the light liquid material flow feeding position of the rectifying tower is arranged at the tower kettle of the rectifying tower, and the heavy liquid material flow feeding position of the rectifying tower is arranged between the stripping section and the rectifying section of the rectifying tower;
the classifying device is a classifying device for separating light solid particles and heavy solid particles in feed liquid based on a density difference principle.
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| CN108147979A (en) * | 2017-12-25 | 2018-06-12 | 万华化学集团股份有限公司 | A kind of method for preparing methyl diphenylene diisocyanate and/or polyphenyl polymethylene polyisocyanates |
| CN115925581A (en) * | 2021-08-09 | 2023-04-07 | 万华化学集团股份有限公司 | Method for preparing isocyanate |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108147979A (en) * | 2017-12-25 | 2018-06-12 | 万华化学集团股份有限公司 | A kind of method for preparing methyl diphenylene diisocyanate and/or polyphenyl polymethylene polyisocyanates |
| CN115925581A (en) * | 2021-08-09 | 2023-04-07 | 万华化学集团股份有限公司 | Method for preparing isocyanate |
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