CN114225455A - System and method for purifying hexamethylene diisocyanate - Google Patents
System and method for purifying hexamethylene diisocyanate Download PDFInfo
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- CN114225455A CN114225455A CN202111562606.0A CN202111562606A CN114225455A CN 114225455 A CN114225455 A CN 114225455A CN 202111562606 A CN202111562606 A CN 202111562606A CN 114225455 A CN114225455 A CN 114225455A
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- 239000005057 Hexamethylene diisocyanate Substances 0.000 title claims abstract description 65
- RRAMGCGOFNQTLD-UHFFFAOYSA-N hexamethylene diisocyanate Chemical compound O=C=NCCCCCCN=C=O RRAMGCGOFNQTLD-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims description 25
- 239000000463 material Substances 0.000 claims abstract description 65
- 239000002904 solvent Substances 0.000 claims abstract description 26
- 239000003381 stabilizer Substances 0.000 claims abstract description 26
- 238000002360 preparation method Methods 0.000 claims abstract description 17
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 7
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims abstract description 4
- 238000003756 stirring Methods 0.000 claims abstract description 4
- YGYAWVDWMABLBF-UHFFFAOYSA-N Phosgene Chemical compound ClC(Cl)=O YGYAWVDWMABLBF-UHFFFAOYSA-N 0.000 claims description 24
- 239000007789 gas Substances 0.000 claims description 23
- 239000012535 impurity Substances 0.000 claims description 13
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 12
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 12
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 12
- 239000000126 substance Substances 0.000 claims description 11
- IDKXMGZRWKCTGA-UHFFFAOYSA-N chloroimino(oxo)methane Chemical compound ClN=C=O IDKXMGZRWKCTGA-UHFFFAOYSA-N 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 8
- 238000010992 reflux Methods 0.000 claims description 7
- 239000007791 liquid phase Substances 0.000 claims description 6
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims description 6
- 150000007970 thio esters Chemical class 0.000 claims description 6
- GHKOFFNLGXMVNJ-UHFFFAOYSA-N Didodecyl thiobispropanoate Chemical compound CCCCCCCCCCCCOC(=O)CCSCCC(=O)OCCCCCCCCCCCC GHKOFFNLGXMVNJ-UHFFFAOYSA-N 0.000 claims description 4
- JKBYAWVSVVSRIX-UHFFFAOYSA-N octadecyl 2-(1-octadecoxy-1-oxopropan-2-yl)sulfanylpropanoate Chemical compound CCCCCCCCCCCCCCCCCCOC(=O)C(C)SC(C)C(=O)OCCCCCCCCCCCCCCCCCC JKBYAWVSVVSRIX-UHFFFAOYSA-N 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- 238000009835 boiling Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 238000011084 recovery Methods 0.000 claims description 3
- 125000004209 (C1-C8) alkyl group Chemical group 0.000 claims description 2
- 239000003508 Dilauryl thiodipropionate Substances 0.000 claims description 2
- 238000007872 degassing Methods 0.000 claims description 2
- 235000019304 dilauryl thiodipropionate Nutrition 0.000 claims description 2
- 125000000623 heterocyclic group Chemical group 0.000 claims description 2
- 238000003860 storage Methods 0.000 claims description 2
- 239000011552 falling film Substances 0.000 claims 1
- 238000006116 polymerization reaction Methods 0.000 abstract description 9
- 238000000746 purification Methods 0.000 abstract description 9
- 239000007788 liquid Substances 0.000 abstract description 7
- 238000004939 coking Methods 0.000 abstract description 4
- 238000010438 heat treatment Methods 0.000 abstract description 2
- 239000011273 tar residue Substances 0.000 abstract 1
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 description 8
- 239000012948 isocyanate Substances 0.000 description 7
- 150000002513 isocyanates Chemical class 0.000 description 7
- JLVWYWVLMFVCDI-UHFFFAOYSA-N diethyl benzene-1,3-dicarboxylate Chemical compound CCOC(=O)C1=CC=CC(C(=O)OCC)=C1 JLVWYWVLMFVCDI-UHFFFAOYSA-N 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- RFFLAFLAYFXFSW-UHFFFAOYSA-N 1,2-dichlorobenzene Chemical compound ClC1=CC=CC=C1Cl RFFLAFLAYFXFSW-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000003963 antioxidant agent Substances 0.000 description 2
- 230000003078 antioxidant effect Effects 0.000 description 2
- 239000013068 control sample Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001718 carbodiimides Chemical class 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000000539 dimer Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012719 thermal polymerization Methods 0.000 description 1
- 239000013638 trimer Substances 0.000 description 1
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Classifications
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- 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
- B01D3/146—Multiple effect distillation
-
- 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
- B01D3/34—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping with one or more auxiliary substances
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a system for purifying hexamethylene diisocyanate, which is used for purifying photochemical liquid obtained based on phosgenation synthesis, and comprises the following steps: and (2) sending the HDI photochemical solution from the tower to a de-phosgene tower for de-gassing, sending the de-gassed material to a de-solvent tower and a de-light tower for further processing to obtain crude HDI material liquid, sending the obtained crude HDI to a preparation kettle with stirring, combining the crude HDI with a mixed stabilizer, sending the mixture to a rectifying tower for rectifying, and extracting a fraction from the tower top to obtain a qualified HDI product. The invention has simple and convenient operation, reduces the polymerization of materials in a desolventizing section by using the desolventizing tower and the light component removing tower, can avoid the polymerization coking phenomenon caused by long-time heating of high-content HDI in the tower by adding a mixed stabilizer before rectification, improves the purification efficiency to a great extent and reduces the generation of tar residues.
Description
Technical Field
The invention belongs to the technical field of preparation of hexamethylene diisocyanate, and particularly relates to a purification method of hexamethylene diisocyanate, in particular to a purification method of photochemical synthesized hexamethylene diisocyanate.
Background
The isocyanate is widely applied to various fields of industrial production, war industry, aerospace and the like, hexamethylene diisocyanate is a high-end isocyanate product with increasing demand, and the conventional industrial purification method of the hexamethylene diisocyanate is mainly carried out through the steps of degassing, desolventizing, rectifying and the like, so that the HDI product meeting the index is finally obtained. The isocyanate is a heat-sensitive substance, HDI is not an exception, and HDI is known to be extremely easy to deteriorate at high temperature to generate solid impurities such as dimer, trimer, carbodiimide, urethanonediamine and the like, and the impurities not only affect the product yield, but also block pipelines and reboilers in the industrial production process and even attach walls to affect heat exchange, thereby greatly affecting the treatment cost and the production efficiency.
The patent CN103382167A discloses a method for refining hexamethylene diisocyanate, HDI photochemical solution enters a distillation tower with a stirrer to be distilled, all o-dichlorobenzene solvent is removed, tower kettle materials and DEIP solvent are mixed according to a certain proportion and enter a rectification tower with a stirrer to be further processed, and a qualified HDI product is obtained; according to the invention, the stirring is introduced in the rectification process, so that the materials are uniformly heated, the polymerization of HDI is reduced to a certain extent, but a large amount of heavy solvent diethyl isophthalate (DEIP) is introduced in the subsequent treatment, the DEIP is easy to generate side reaction with the phosgene which is not removed completely in the system, insoluble impurities are generated, and the DEIP is easy to be incompletely separated from the HDI in the circulation process, so that the product yield is reduced.
Patent CN1729166A discloses a method for purifying isocyanate synthesis product, which uses a thin film evaporator to heat and gasify, the isocyanate is extracted from tower measuring line, phosgene and hydrogen chloride gas are extracted from tower top, the tower bottom material enters the next thin film evaporator to be processed, and the obtained tower top material and the material extracted from the first tower measuring line are combined to obtain the isocyanate product. According to the invention, through the use of the film evaporator, the heat exchange area is increased, the material residence time is reduced to reduce the polymerization probability of isocyanate, but the soluble impurity monochloro isocyanate cannot be effectively separated, and the solvent needs to be removed first and then the film evaporator is used for treatment, so that the problem of polymerization at the bottom of a desolventizing section tower cannot be avoided.
Disclosure of Invention
The invention solves the problems of long material heating time, easy coking, large residue amount, low purification yield and the like in the prior art, and provides a system and a method for purifying hexamethylene diisocyanate.
The invention is realized by the following technical scheme:
the HDI photochemical solution obtained through synthesis generally contains a large amount of solvent, a small amount of phosgene, hydrogen chloride and other soluble and insoluble impurities, in order to avoid corrosion of equipment at high temperature in the subsequent process under the action of acid gas, phosgene and hydrogen chloride are removed to obtain degassed feed liquid, the feed liquid is distilled and desolventized in a tower to remove the solvent, the solvent used in the HDI synthesis process is generally chlorobenzene, the boiling point difference between chlorobenzene and HDI is large, in the continuous desolventizing process, the material in a desolventizing tower kettle is always at a constant temperature, the lower the solvent amount in the material in the tower kettle is, the higher the kettle temperature is, the larger the solvent amount is, the longer the material retention time is, the certain retention amount of the solvent oil in the material in the desolventizing tower kettle is controlled to be about 5-10%, the temperature in the tower kettle and the HDI content are reduced, and the long-time thermal polymerization of high-content HDI is avoided. At the moment, the desolventized material contains a small amount of solvent, soluble impurities, oligomers and the like, the desolventized material is further subjected to lightness removal, the residual solvent and volatile impurities (monochloro isocyanate) are removed in a lightness removing tower with short retention time and good separation efficiency, and HDI carried out by light components is recycled to the desolventizing tower for recovery. In the rectification process, high-content HDI is easy to cause polymerization and carbonization due to overhigh temperature and longer residence time of the tower kettle.
The invention provides a purification system which comprises a light gas removal tower, a desolventizing tower, a light gas removal tower, a stabilizer preparation kettle and a rectifying tower; the material outlet at the bottom of the light gas removal tower is connected with the feed inlet of the light gas removal tower, the material outlet at the bottom of the light gas removal tower is connected with the feed inlet at the upper part of the stabilizer preparation kettle, and the material outlet at the lower part of the preparation kettle is connected with the feed inlet at the middle part of the rectifying tower. The system also comprises a reboiler, an overhead condenser and a material conveying pump, and the specific steps are as follows:
s1 feeding the HDI photochemical solution obtained by phosgenation synthesis through the upper part of a phosgene removing tower, condensing by a tower top condenser, and then extracting phosgene and hydrogen chloride gas, wherein the removed phosgene and hydrogen chloride gas are sent to a pressurized rectifying tower for separation and recovery, and a degassed material with the phosgene content less than 1000ppm is extracted from the tower bottom; the operating pressure of the phosgene removing tower is 0.5 bar-2.0 bar, 1.0-1.5 bar is preferred, and the theoretical plate number is 5-15.
S2, conveying the degassed material into a desolventizing tower from the 8 th to 12 th plates of the desolventizing tower, adjusting the reflux ratio, collecting most of the solvent at the tower top, conveying the desolventized solvent into a solvent receiving storage tank, and collecting HDI material containing 5-10% of the solvent and other impurities at the tower bottom; the operating pressure of the desolventizing tower is 0.05 bar-0.3 bar, preferably 0.1 bar-0.2 bar, and the theoretical plate number is 10-20.
S3 feeding the desolventized material into a lightness-removing tower from the 14 th to 18 th plates of the lightness-removing tower, adjusting the reflux ratio, feeding the liquid-phase light component extracted from the tower top into a desolventizing tower for circulation, and extracting a high-content HDI material from the tower bottom, wherein the high-content HDI material contains monochloro isocyanate impurities less than 1500 ppm; the operating pressure of the light component removal tower is 0.02 bar-0.2 bar, preferably 0.02 bar-0.1 bar, and the theoretical plate number is 15-30.
And (3) feeding the material in the lightness-removing tower kettle taken out from S4 into a stabilizer preparation kettle with stirring and heat tracing, wherein the material in the stabilizer preparation kettle and the mixed stabilizer are mixed according to the mass ratio of 1: 0.001-0.015 weight percent, preferably 1: 0.005-0.01; the temperature of the stabilizer preparation kettle is more than 60 ℃.
And (3) feeding the S5 mixed material into the rectifying tower from the 8 th to 10 th plates of the rectifying tower, adjusting the reflux ratio, wherein the liquid phase extracted from the top of the tower is a qualified HDI product, the operating pressure of the rectifying tower is 0.01bar to 0.08bar, and the theoretical plate number is 10 to 20.
In the step S1, the HDI mass fraction in the HDI photochemical solution is 10-60%, preferably 10-20%; the mass fraction of phosgene is 0.5-5%; the mass fraction of the hydrogen chloride is 0.05-1%; the mass fraction of the monochloro isocyanate is 0.1-2%, preferably 0.1-1%.
The method has higher requirements on the residual phosgene amount in the material, and the residual phosgene amount directly influences the action effect of the added mixed stabilizer on the HDI monomer.
In step S4, the mixed stabilizer is a mixture of a high-boiling-point phenolic substance a and a macromolecular thioester B, and the structural formula of the high-boiling-point phenolic substance a is as follows:
wherein X1, X2, X3, X4 and X5 are independently selected from H, C1-C8 alkyl chain, heterocycle, S or the combination thereof. Macromolecular thioesters B include, but are not limited to: dioctadecyl thiodipropionate, dilauryl thiodipropionate, didodecyl thiodipropionate, preferably dioctadecyl thiodipropionate; the mixing mass ratio of the two substances is A: b is 1:1.3 to 3, preferably 1:1.5 to 2.0.
In summary, the following beneficial effects of the invention are:
1. compared with the prior art, the system and the method for purifying hexamethylene diisocyanate have the advantages that a desolventizing tower and a light-removing tower are combined for HDI purification, the separation effect of volatile impurities is improved, the polymerization of HDI in a desolventizing section is avoided due to the lower tower kettle temperature, the polymerization of HDI in the light-removing section is reduced due to the shorter residence time, a mixed stabilizer of a high-boiling-point phenolic substance and a macromolecular thioester antioxidant is introduced in a rectifying section, the mixed substance can remarkably reduce the polymerization coking of high-content HDI at high temperature, and the high-boiling-point phenolic substance and the macromolecular thioester antioxidant are easy to separate from HDI.
2. The system and the method for purifying hexamethylene diisocyanate have the advantages of low material loss rate, small residue, simple and convenient process operation and low equipment requirement.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic flow chart of an implementation method provided by the present invention.
Reference numbers and corresponding part names in the drawings:
1-a light gas removal tower; 2-a stripper reboiler; 3-a desolventizing tower; 4-a desolventizing column reboiler; 5-a light component removal tower; 6-a light component removal tower reboiler; 7-a rectifying tower; 8-a rectifying tower reboiler; 9-a solvent reservoir; 10-stabilizer preparation kettle.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.
The specific embodiment of the invention provides a purification system and a method of hexamethylene diisocyanate photochemical liquid, wherein the system comprises a light-removing gas tower 1, a light-removing gas tower reboiler 2, a desolventizing tower 3, a desolventizing tower reboiler 4, a light-removing tower 5, a light-removing tower reboiler 6, a stabilizer preparation kettle 10, a rectifying tower 7 and a rectifying tower reboiler 8;
in the system, a material outlet at the bottom of the light gas removal tower 1 is connected with a material inlet of a desolventizing tower 3, a material outlet at the bottom of the desolventizing tower 3 is connected with a material inlet of a light removal tower 5, a material outlet at the bottom of the light removal tower 5 is connected with a material inlet at the upper part of a stabilizer preparation kettle 10, and a material outlet at the lower part of the stabilizer preparation kettle 10 is connected with a material inlet at the middle part of a rectifying tower 7.
The processing method comprises the following steps: the method comprises the steps of treating a hexamethylene diisocyanate photochemical liquid in a phosgene removal tower 1, extracting phosgene and hydrogen chloride gas from the tower top, sending a liquid-phase extracted material in a tower kettle into a desolventizing tower 3, desolventizing the solvent from the tower top of the desolventizing tower 3, sending an extracted material in a tower kettle of the desolventizing tower 3 into a light component removal tower 5, extracting light components such as monochloro isocyanate, solvent and the like from the tower top of the light component removal tower 5, fully mixing a material in a tower kettle of the light component removal tower 5 and a stabilizing agent in a preparation kettle, sending the mixture into a rectifying tower 7 for further treatment, extracting hexamethylene diisocyanate oligomer and a coking substance from a tower kettle of the rectifying tower 7, and extracting a hexamethylene diisocyanate product meeting indexes from the tower top.
Examples
As shown in fig. 1, the HDI photochemical solution obtained by synthesis was subjected to sample sending analysis, wherein the mass content of HDI was 13.9%, the mass content of phosgene was 2.0%, the mass content of hydrogen chloride was 0.12%, the mass content of monochloro isocyanate was 1.3%, the mass content of heavy component impurities was 0.26%, and the balance was solvent chlorobenzene. Feeding the photochemical liquid from the 2 nd to 3 rd plates at the upper part of a desorptive gas tower 1, wherein the pressure in the tower is 1.2bar, the number of theoretical plates is 10 to 12, the liquid phase is totally refluxed, phosgene and hydrogen chloride gas are extracted from the gas phase of a condenser at the tower top, the extracted tower kettle materials are subjected to central control sample analysis, the mass content of HDI is 14.38 percent, the mass content of phosgene is 500ppm, the materials after the phosgene removal are fed from the 3 th to 9 th plates of the desorptive gas tower, the pressure in the desorptive gas tower is 0.1bar, and the number of theoretical plates is 10 to 15. The temperature of the tower bottom is 115 ℃, and the solvent content of the tower bottom is 8.5 percent.
And (3) feeding the material after desolventizing from the 16 th to 17 th plates of the light component removal tower 5, wherein the pressure in the light component removal tower is 0.05bar, the number of theoretical plates is 20-30, the temperature of a tower kettle is 155 ℃, the reflux ratio is 1:1.5, and the extracted material in the tower kettle is subjected to central control sample analysis, wherein the mass content of monochloro isocyanate is 1071ppm, and the chlorobenzene content is 137 ppm.
And (3) exchanging heat of the lightness-removed material to 60 ℃ through a quencher, feeding the lightness-removed material into the configuration kettle from a feed inlet at the upper part of the stabilizer configuration kettle, feeding the lightness-removed material and the stabilizer according to a feeding ratio of 1:0.01, discharging the lightness-removed material from the bottom of the configuration kettle after a short retention time, and feeding the lightness-removed material from the 8 th plate to the 9 th plate of the rectification tower 7, wherein the pressure in the rectification tower is 0.05bar, and the theoretical number of the plates is 16. The analytical results of the taken overhead material are shown in the following table:
| index name | Analysis results |
| HDI content% | ≥99.65 |
| Ppm of hydrolyzed chlorine | ≤80 |
| NCO value% | ≥49.7 |
| Chroma (Pt-Co) | 25 |
| Appearance of the product | Colorless and transparent, and no suspended matter |
By the process, the product purification yield reaches 96%.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. The system for purifying hexamethylene diisocyanate is characterized by comprising a light-removing gas tower (1), a light-removing gas tower reboiler (2), a desolventizing tower (3), a desolventizing tower reboiler (4), a light-removing tower (5), a light-removing tower reboiler (6), a stabilizer preparation kettle (10), a rectifying tower (7) and a rectifying tower reboiler (8); the system comprises a degassing tower (1), a material outlet at the bottom of the tower is connected with a feed inlet of a desolventizing tower (3), a material outlet at the bottom of the desolventizing tower (3) is connected with a feed inlet of a light component removing tower (5), a discharge outlet at the bottom of the light component removing tower (5) is connected with a feed inlet at the upper part of a stabilizer configuration kettle (10), a discharge outlet at the lower part of the stabilizer configuration kettle (10) is connected with a feed inlet at the middle part of a rectifying tower (7), and the system further comprises a tower top condenser and a material conveying pump.
2. A method of purifying hexamethylene diisocyanate, comprising the steps of:
s1, feeding the HDI photochemical solution obtained by phosgenation synthesis through the upper part of a phosgene removal tower (1), condensing by a tower top condenser to obtain phosgene and hydrogen chloride gas, feeding the removed phosgene and hydrogen chloride gas into a pressurized rectifying tower (7) for separation and recovery, and collecting a degassed material with the phosgene content less than 1000ppm from the tower bottom; the operating pressure of the phosgene removal tower (1) is 0.5-2.0 bar, preferably 1.0-1.5 bar, and the theoretical plate number is 5-15;
s2, conveying the degassed material into a desolventizing tower (3) from the 8 th to 12 th plates of the desolventizing tower (3), adjusting the reflux ratio, collecting most of the solvent at the top of the tower, conveying the desolventized solvent into a solvent receiving storage tank (9), and collecting an HDI material containing 5-10% of the solvent and other impurities at the bottom of the tower; the operating pressure of the desolventizing tower (3) is 0.05 bar-0.3 bar, preferably 0.1 bar-0.2 bar, and the theoretical plate number is 10-20;
s3, feeding the material subjected to desolventizing into a lightness-removing tower (5) from the 14 th to 18 th plates of the lightness-removing tower (5), adjusting the reflux ratio, feeding a liquid-phase light component extracted from the top of the tower into a desolventizing tower (3) for circulation, and extracting a high-content HDI material from the tower kettle, wherein the high-content HDI material contains monochloro isocyanate impurities of less than 1500 ppm; the operating pressure of the light component removal tower (5) is 0.02 bar-0.2 bar, preferably 0.02 bar-0.1 bar, and the theoretical plate number is 15-30;
s4, transferring the recovered material of the light component removal tower (5) to 60 ℃ through a quencher after heat exchange, sending the material into a stabilizer preparation kettle (10) with stirring and heat tracing, wherein the material in the stabilizer preparation kettle (10) is mixed with a mixed stabilizer according to the mass ratio of 1: 0.001-0.015 weight percent, preferably 1: 0.005-0.01; the temperature of the stabilizer preparation kettle (1) is more than 60 ℃;
s5, feeding the mixed material obtained in the step S4 into a rectifying tower (7) from the 7 th to 8 th plates of the rectifying tower (7), and carrying out heat tracing to more than 60 ℃ all the time in a pipeline conveying interval; adjusting the reflux ratio, wherein the liquid phase extracted from the tower top is a qualified HDI product; the operating pressure of the rectifying tower (7) is 0.01 bar-0.08 bar, and the theoretical plate number is 10-20.
3. A method for purifying hexamethylene diisocyanate according to claim 2, wherein the HDI photochemical solution comprises 10% to 60%, preferably 10% to 20% of HDI by mass; the mass fraction of phosgene is 0.5-5%; the mass fraction of the hydrogen chloride is 0.05-1%; the mass fraction of the monochloro isocyanate is 0.1-5%, preferably 0.1-2%, and the balance is solvent.
4. A method for purifying hexamethylene diisocyanate according to claim 2, wherein said mixed stabilizer is a mixture of a high-boiling phenolic substance a and a macromolecular thioester B, a high-boiling phenolic substance a having the following general structural formula:
wherein X1, X2, X3, X4 and X5 are independently selected from H, C1-C8 alkyl chain, heterocycle, S or the combination of the above; the macromolecular thioester B comprises but is not limited to: dioctadecyl thiodipropionate, dilauryl thiodipropionate, didodecyl thiodipropionate, preferably dioctadecyl thiodipropionate; the mixing mass ratio of the two substances is A: b is 1:1.3 to 3, preferably 1:1.5 to 2.0.
5. The process for purifying hexamethylene diisocyanate according to claim 2, wherein in steps S3 and S5, the lightness-removing column reboiler (6) and the rectification column reboiler (8) are preferably falling film reboilers.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111562606.0A CN114225455A (en) | 2021-12-20 | 2021-12-20 | System and method for purifying hexamethylene diisocyanate |
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| CN114984601A (en) * | 2022-07-05 | 2022-09-02 | 中国科学院过程工程研究所 | Device system and method for separating and refining 1, 5-pentamethylene diisocyanate by non-phosgene method |
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| CN114984601A (en) * | 2022-07-05 | 2022-09-02 | 中国科学院过程工程研究所 | Device system and method for separating and refining 1, 5-pentamethylene diisocyanate by non-phosgene method |
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