CN115304454B - Separation method and system for recycling glycol in polyester production process - Google Patents
Separation method and system for recycling glycol in polyester production process Download PDFInfo
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- CN115304454B CN115304454B CN202110495507.9A CN202110495507A CN115304454B CN 115304454 B CN115304454 B CN 115304454B CN 202110495507 A CN202110495507 A CN 202110495507A CN 115304454 B CN115304454 B CN 115304454B
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- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 title claims abstract description 428
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 238000000926 separation method Methods 0.000 title claims abstract description 45
- 229920000728 polyester Polymers 0.000 title claims abstract description 43
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 238000004064 recycling Methods 0.000 title claims abstract description 10
- 239000012535 impurity Substances 0.000 claims abstract description 43
- 238000000034 method Methods 0.000 claims abstract description 32
- 239000002994 raw material Substances 0.000 claims abstract description 27
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 239000012752 auxiliary agent Substances 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 8
- 150000001263 acyl chlorides Chemical class 0.000 claims abstract description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 21
- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 claims description 20
- 239000000047 product Substances 0.000 claims description 19
- 229910052757 nitrogen Inorganic materials 0.000 claims description 16
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 12
- -1 cyclic aldehydes Chemical class 0.000 claims description 10
- 238000010992 reflux Methods 0.000 claims description 10
- 229920001577 copolymer Polymers 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- DLFVBJFMPXGRIB-UHFFFAOYSA-N Acetamide Chemical compound CC(N)=O DLFVBJFMPXGRIB-UHFFFAOYSA-N 0.000 claims description 8
- BGTOWKSIORTVQH-UHFFFAOYSA-N cyclopentanone Chemical compound O=C1CCCC1 BGTOWKSIORTVQH-UHFFFAOYSA-N 0.000 claims description 8
- KZNICNPSHKQLFF-UHFFFAOYSA-N succinimide Chemical compound O=C1CCC(=O)N1 KZNICNPSHKQLFF-UHFFFAOYSA-N 0.000 claims description 8
- 239000004952 Polyamide Substances 0.000 claims description 7
- 229920002647 polyamide Polymers 0.000 claims description 7
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 7
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 7
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 claims description 7
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 claims description 6
- CTSLXHKWHWQRSH-UHFFFAOYSA-N oxalyl chloride Chemical compound ClC(=O)C(Cl)=O CTSLXHKWHWQRSH-UHFFFAOYSA-N 0.000 claims description 6
- SXYFKXOFMCIXQW-UHFFFAOYSA-N propanedioyl dichloride Chemical compound ClC(=O)CC(Cl)=O SXYFKXOFMCIXQW-UHFFFAOYSA-N 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 5
- VHGGRTWHRJRQKU-UHFFFAOYSA-N 1-methyl-2h-pyrrol-5-one Chemical compound CN1CC=CC1=O VHGGRTWHRJRQKU-UHFFFAOYSA-N 0.000 claims description 4
- DZCBKUAAGVVLOX-UHFFFAOYSA-N 1-morpholin-4-ylethanol Chemical compound CC(O)N1CCOCC1 DZCBKUAAGVVLOX-UHFFFAOYSA-N 0.000 claims description 4
- HTWIZMNMTWYQRN-UHFFFAOYSA-N 2-methyl-1,3-dioxolane Chemical compound CC1OCCO1 HTWIZMNMTWYQRN-UHFFFAOYSA-N 0.000 claims description 4
- HVCNXQOWACZAFN-UHFFFAOYSA-N 4-ethylmorpholine Chemical compound CCN1CCOCC1 HVCNXQOWACZAFN-UHFFFAOYSA-N 0.000 claims description 4
- IYLIUGUSZIJCKW-UHFFFAOYSA-N C=CC1=CC(=O)CN1 Chemical compound C=CC1=CC(=O)CN1 IYLIUGUSZIJCKW-UHFFFAOYSA-N 0.000 claims description 4
- ZSBDPRIWBYHIAF-UHFFFAOYSA-N N-acetyl-acetamide Natural products CC(=O)NC(C)=O ZSBDPRIWBYHIAF-UHFFFAOYSA-N 0.000 claims description 4
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 claims description 4
- ZHNUHDYFZUAESO-OUBTZVSYSA-N aminoformaldehyde Chemical compound N[13CH]=O ZHNUHDYFZUAESO-OUBTZVSYSA-N 0.000 claims description 4
- ALBYIUDWACNRRB-UHFFFAOYSA-N hexanamide Chemical compound CCCCCC(N)=O ALBYIUDWACNRRB-UHFFFAOYSA-N 0.000 claims description 4
- KNCYXPMJDCCGSJ-UHFFFAOYSA-N piperidine-2,6-dione Chemical compound O=C1CCCC(=O)N1 KNCYXPMJDCCGSJ-UHFFFAOYSA-N 0.000 claims description 4
- 229960002317 succinimide Drugs 0.000 claims description 4
- JDTUPLBMGDDPJS-UHFFFAOYSA-N 2-methoxy-2-phenylethanol Chemical compound COC(CO)C1=CC=CC=C1 JDTUPLBMGDDPJS-UHFFFAOYSA-N 0.000 claims description 3
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 claims description 3
- 239000006227 byproduct Substances 0.000 claims description 2
- 150000003997 cyclic ketones Chemical class 0.000 claims description 2
- CLBRCZAHAHECKY-UHFFFAOYSA-N [Co].[Pt] Chemical compound [Co].[Pt] CLBRCZAHAHECKY-UHFFFAOYSA-N 0.000 abstract description 16
- 238000000746 purification Methods 0.000 abstract description 3
- 238000009776 industrial production Methods 0.000 abstract 1
- 230000008569 process Effects 0.000 description 18
- 238000004458 analytical method Methods 0.000 description 11
- 238000010168 coupling process Methods 0.000 description 8
- 230000015556 catabolic process Effects 0.000 description 7
- 238000006731 degradation reaction Methods 0.000 description 7
- 229920006149 polyester-amide block copolymer Polymers 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 230000001186 cumulative effect Effects 0.000 description 5
- 239000000835 fiber Substances 0.000 description 5
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 5
- 238000007670 refining Methods 0.000 description 5
- 229920000742 Cotton Polymers 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 230000032050 esterification Effects 0.000 description 3
- 238000005886 esterification reaction Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 239000007857 degradation product Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000006266 etherification reaction Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000010525 oxidative degradation reaction Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007363 ring formation reaction Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/88—Separation; Purification; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification of at least one compound
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a separation method and a separation system for recycling glycol in a polyester production process. The separation method comprises the following steps: the crude ethylene glycol raw material reacts with acyl chloride auxiliary agent to obtain a pretreated mixed material; and rectifying and separating the pretreated mixture to obtain a light component, an ethylene glycol product and a heavy component. The separation system comprises a rectification system, wherein a raw material pre-reaction system is arranged in front of the rectification system, and the rectification system comprises a light component removal tower and a heavy component removal tower. The method solves the problems of high impurity content in the recovered glycol and high difficulty in conventional rectification separation in the polyester production process in the prior art, and the obtained glycol product has high purity, effectively removes impurities affecting the platinum cobalt thermochromatic property, improves the recycling doping amount for polyester production, and can be used in the industrial production of the recovered glycol purification of the polyester.
Description
Technical Field
The invention relates to a separation method and a separation system for recycling glycol in a polyester production process.
Background
The super cotton-like polyester fiber is characterized in that the main body of the super cotton-like polyester fiber is polyester, the polyester content is more than 85 percent, and the super cotton-like polyester fiber is a differentiation functionalized polyester fiber which looks like cotton, feels like cotton, wears like cotton and is more convenient to use than cotton. The super cotton-like polyester fiber is generally polyamide ester obtained by introducing a polymer with amide groups to be copolymerized in the synthetic preparation process of polyester PET.
The production process of the polyesteramide comprises the following steps: a certain amount of ethylene glycol, terephthalic acid and a catalyst are esterified in an esterification reactor, then a certain amount of caprolactam or polyamide and an auxiliary agent are added, copolymerization is carried out in a polymerization reactor, and water, complex degradation products, unreacted ethylene glycol and other components generated in the polyester reactor are pumped out to a crude ethylene glycol storage tank through a vacuum system and are recovered by an ethylene glycol refining system.
The current method for treating the crude glycol extracted by the vacuum system mainly comprises the following steps:
1. No ethylene glycol recovery refining unit: patent CN1054988a discloses a method for producing polyester continuously by direct esterification, which is characterized in that a recovery refining device is not additionally arranged to recover and refine the excessive ethylene glycol in the system, and the ethylene glycol condensed by a vacuum system is directly returned to be used as a raw material. This process can result in the accumulation of impurities in the system resulting from degradation of the polyester, resulting in a decrease in the color of the polyester.
2. A single process column was set up for ethylene glycol refinement: patent CN101575122a discloses a method for refining crude ethylene glycol by using a process tower and a stripping tower, wherein refined ethylene glycol is obtained from the bottom of the process tower, water, aldehydes and other components are obtained from the top of the process tower, and then the stripping tower is used for treating wastewater. In the process, heavy component impurities generated by degradation cannot be separated, the impurities are accumulated in a system, and finally polyester chromaticity is not up to standard. The ' transformation of esterification process tower ' published by 21 nd stage of 2008 in the polyester industry ' also recovers crude ethylene glycol through a single process tower, and still leads the purity of the refined ethylene glycol to be substandard.
Thus, the separation and refining of the recycled glycol in the production process of the polyesteramide is only in a simple rectifying and separating stage. Because the glycol component recovered in the preparation process of polyesteramide is more complex than that of conventional polyester, industrial devices and small-scale operation research processes find that certain impurities which are difficult to separate by conventional rectification always exist in the product glycol, and the thermochromatism of the product glycol always is difficult to reduce to the general use requirement of the polyester. Therefore, how to realize the separation of impurities and the reduction of thermochromatism through process innovation based on the conventional rectification process is one of the important problems to be solved in the large-scale continuous production of polyesters, especially polyesteramides.
Disclosure of Invention
The invention aims to solve the technical problems of high impurity content in recovered glycol in the polyester production process and high conventional rectification separation difficulty in the prior art, and provides a novel separation method and system for recovering glycol in the polyester production process. The method can obviously improve the purity of the glycol product in the existing rectification separation process, reduce the thermal chromaticity of the glycol product and improve the recycling blending proportion of the glycol product.
The first aspect of the invention provides a separation method for recycling glycol in a polyester production process, which comprises the following steps:
S1, reacting a crude ethylene glycol raw material with an acyl chloride auxiliary agent to obtain a pretreated mixed material;
s2, rectifying and separating the pretreated mixture to obtain a light component, an ethylene glycol product and a heavy component.
In the above technical scheme, the polyester is polyethylene terephthalate, or a copolymer of polyethylene terephthalate and polyamide, or a copolymer of terephthalic acid, ethylene glycol and caprolactam.
In the above technical scheme, the polyester is preferably a copolymer of polyethylene terephthalate and polyamide or a copolymer of terephthalic acid, ethylene glycol and caprolactam.
In the above technical scheme, in step S1, the raw material of crude ethylene glycol is a raw material containing crude ethylene glycol, and may be crude ethylene glycol or a mixture of crude ethylene glycol and fresh ethylene glycol. The crude ethylene glycol is derived from an ethylene glycol-rich material which is a byproduct in the polyester production process, and is generally derived from an ethylene glycol-rich material extracted by a vacuum system or an ethylene glycol-rich material which is preliminarily purified by a polyester process tower. The crude ethylene glycol comprises ethylene glycol and also comprises impurities including chain or cyclic aldehydes, chain or cyclic ketones, chain or cyclic nitrogen-containing impurities, and can also comprise other oxygen-containing impurities such as oxygen-containing heterocycles, alcohols and the like. In the raw material of the crude ethylene glycol, the mass content of the ethylene glycol is 75-95%. The crude ethylene glycol platinum cobalt has a thermochromatic value of greater than 500Hazen. The impurity content is not less than 5ppm by mass based on the total nitrogen element, preferably not less than 50ppm by mass, more preferably not less than 100ppm by mass.
In the above technical solution, the impurities include, but are not limited to, the following substances: water, acetaldehyde, N-ethylmorpholine, morpholinoethanol, N-methyl-3-pyrrolin-2-one, caprolactam, acetamide, caproamide, glutarimide, succinimide, 2-vinyl-pyrrolinone, diacetamide and the like. Optionally, the impurities may further include at least one of pyridine, 2-methyl-1, 3-dioxolane, cyclopentanone, amino formaldehyde, diethylene glycol, triethylene glycol, and the like.
In the above technical solution, in step S1, the auxiliary agent is at least one selected from oxalyl chloride, malonyl chloride and succinyl chloride.
In the technical scheme, in the step S1, the mass ratio of the raw material of the crude ethylene glycol to the auxiliary agent is 1000: (0.9-5.3).
In the above technical scheme, in step S1, the reaction conditions are as follows: the temperature is 48-105 ℃, the pressure is 0.47-1.05 MPa, and the reaction time is 0.19-0.53 hours.
In the above technical scheme, in step S2, the rectification separation includes light separation and heavy separation. The rectifying tower adopted for the light component removal and separation is a light component removal tower, and the theoretical plate number is 5-12. The light components such as water, aldehyde and the like are extracted from the top of the light component removing tower, and the tower bottom is ethylene glycol and the like and is used as the feeding material of the heavy component removing tower. The weight-removing separation adopts a rectifying tower as a weight-removing tower, and the theoretical plate number is 10-25. Qualified glycol products are extracted from the top or side line of the heavy-removal tower, and the tower bottom is composed of components such as diethylene glycol, triethylene glycol and the like.
In the technical scheme, the operating conditions of the light component removal and separation are as follows: the pressure is 9-33 kPa by absolute pressure, the temperature of the tower bottom is 120-177 ℃, the temperature of the tower top is 41-76 ℃, and the mass reflux ratio is 0.4-1.6.
In the technical scheme, the operation conditions of the heavy-removal separation are as follows: the pressure is 9-32 kPa by absolute pressure, the temperature of the tower bottom is 274-353 ℃, the temperature of the tower top is 125-168 ℃, and the mass reflux ratio is 0.9-3.2.
The invention provides a separation system for recycling glycol in a polyester production process, which comprises a rectification system, wherein a raw material pre-reaction system is arranged in front of the rectification system, and the rectification system comprises a light component removal tower and a heavy component removal tower.
In the technical scheme, the raw material pre-reaction system comprises a raw material heat exchanger of crude glycol and a reactor. The crude ethylene glycol raw material heat exchanger exchanges heat for low-pressure steam. The reactor may be filled with an inert packing such as an inert random packing or an inert structured packing.
High molecular polymers such as polyesters and polyamides or oligomers thereof are generally stable at normal temperature, but at higher temperatures, complex side reactions such as etherification, cyclization, thermal degradation, thermal oxidative degradation and the like can occur, and can produce dozens of impurity components such as acetaldehyde, 2-methyl-1, 3-dioxolane, N-ethylmorpholine, morpholinoethanol, pyridine, cyclopentanone, amino formaldehyde, glutarimide, succinimide, N-methyl-3-pyrroline-2-one, 2-vinyl-pyrrolinone, caprolactam, acetamide, diacetamide, hexanamide and the like. The mixture system of the series of impurities and the ethylene glycol is complex, and the interaction between the ethylene glycol and various impurities cannot be clarified at present, for example, the inventor finds that in the practical research process: although the difference between the bubble point of part of impurities and the bubble point of ethylene glycol is large, the part of impurities and the ethylene glycol show non-ideal gas-liquid balance behavior due to the interaction effect of different chemical components, namely, part of impurities and the ethylene glycol are distilled out from the top of a rectifying tower at the same time, so that the ethylene glycol product contains impurities which have obvious influence on chromaticity indexes, and at present, how to effectively remove the impurities which influence chromaticity is not clear.
The inventor creatively pre-reacts the raw material of the crude ethylene glycol with the auxiliary agent to enable the auxiliary agent to react with certain impurities which are difficult to separate to form new impurities, so that the bubble point difference between the impurities to be separated and the ethylene glycol is obviously increased or the non-ideal gas-liquid balance behavior is damaged, and further, the effective separation of the ethylene glycol and the new impurities formed after the pretreatment is realized. The invention solves the technical problems that the prior art is difficult to effectively separate impurities in the crude ethylene glycol raw material and affects the purity and quality of the ethylene glycol, and has simple and effective process flow and easy industrial implementation.
Drawings
FIG. 1 is a schematic diagram of a separation system for recovering ethylene glycol in the polyester production process of the present invention;
wherein reference numerals are as follows:
1 is a crude ethylene glycol raw material storage tank, 2 is a crude ethylene glycol raw material heat exchanger, 3 is a reactor, 4 is a rectification feeding buffer tank, 5 is a light component removal tower, and 6 is a heavy component removal tower.
Detailed Description
The following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
In the invention, the analysis of the glycol component and the measurement of the platinum cobalt chromaticity are carried out according to the analysis methods of the measurement of the content of 4.2 glycol and the measurement of the chromaticity of 4.3 in the standard document of GB/T4649-2008 industrial glycol.
In the invention, the nitrogen element content in the ethylene glycol material is tested by adopting a Mitsubishi total nitrogen analyzer NSX-2100V analyzer, wherein the analysis method is that the argon flow is 200ml/min, the oxygen flow is 400ml/min, and the combustion temperature is 1000-1050 ℃. The total nitrogen cumulative removal rate adopts a direct calculation method, and the calculation formula is as follows by mass:
The invention relates to a separation system (shown in figure 1) for recycling glycol in a polyester production process, which comprises: the rectification system is provided with a raw material pre-reaction system before the rectification system, and comprises a light component removal tower 5 and a heavy component removal tower 6. The raw material pre-reaction system comprises a raw material heat exchanger 2 and a reactor 3. The crude ethylene glycol raw material heat exchanger exchanges heat for low-pressure steam. The reactor is filled with inert filler. The separation process is as follows: raw ethylene glycol raw material (such as raw ethylene glycol is derived from ethylene glycol-rich materials extracted from a polyester vacuum system or ethylene glycol-rich materials which are preliminarily purified by a polyester process tower) enters a raw ethylene glycol raw material storage tank 1, the raw ethylene glycol raw material is mixed with an auxiliary agent according to a certain proportion, and enters a reactor 3 for reaction after heat exchange by a raw ethylene glycol raw material heat exchanger 2, and the obtained pretreated mixed material enters a rectification feeding buffer tank 4, then enters a light component removal tower 5 for light component removal, and the ethylene glycol-containing material flow with light components removed enters a heavy component removal tower 6 for heavy component removal to obtain an ethylene glycol product.
[ Example 1]
The polyester used in this example is a copolymer of terephthalic acid, ethylene glycol and caprolactam, and the crude ethylene glycol extracted by the polyester vacuum system has the following mass composition: 82.3% of ethylene glycol, 8.3% of water, 0.4% of acetaldehyde, 0.12% of N-ethylmorpholine, 0.14% of morpholinoethanol, 0.33% of N-methyl-3-pyrrolin-2-one, 3.3% of caprolactam, 0.53% of acetamide, 0.15% of caproamide, 0.11% of glutarimide, 0.46% of succinimide, 0.2% of 2-vinyl-pyrrolinone, 0.23% of diacetamide, 0.26% of 2-methyl-1, 3-dioxolane, 0.53% of cyclopentanone, 0.16% of amino formaldehyde, 0.75% of diethylene glycol, 0.23% of triethylene glycol and 1.50% of other components. The mass content of nitrogen-containing impurities in the crude ethylene glycol was 9000ppm based on total nitrogen.
The separation system (as in figure 1) employed in this example was one in which the crude ethylene glycol feedstock heat exchanger was low pressure steam heat exchanged and the reactor was packed with inert structured packing. The auxiliary agent is malonyl chloride, and the ratio of the raw material of the crude ethylene glycol to the auxiliary agent is 1000:2.5. the operating conditions of the reactor were as follows: the temperature was 75℃and the operating pressure was 0.7MPa, the reaction time was 0.35 hours.
The rectification system comprises a light component removing tower and a heavy component removing tower. The theoretical plate number of the light component removal tower is 8, and light components such as water, aldehyde and the like are extracted from the top of the light component removal tower; the theoretical plate number of the weight removing tower is 17, qualified glycol products are extracted from the top of the weight removing tower, and the tower bottom is composed of components such as diethylene glycol, triethylene glycol and the like. The operating conditions of the light ends column are as follows: the pressure is 20kPa in absolute pressure, the temperature of the tower bottom is 150 ℃, the temperature of the tower top is 60 ℃, and the mass reflux ratio is 1. The operating conditions of the de-weight column are as follows: the pressure is 20kPa in absolute pressure, the temperature of the tower bottom is 313 ℃, the temperature of the tower top is 150 ℃, and the mass reflux ratio is 2.
Analysis was carried out according to the "determination of 4.2 glycol content" in the standard document of GB/T4649-2008 industrial glycol, the cumulative removal rate of degraded impurities (calculated as total nitrogen) by the pre-reaction-rectification coupling process was 85%, and the mass purity of glycol was 99.8%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 180Hazen.
[ Example 2]
The crude ethylene glycol feed composition, separation process steps and apparatus for recovering ethylene glycol during the production of polyesteramide used in this example are the same as in example 1. The only difference from example 1 is the adjustment of the pre-reaction and rectification process parameters, as follows:
the crude ethylene glycol pre-reaction auxiliary agent is malonyl chloride, and the ratio of the crude ethylene glycol to the auxiliary agent is 1000:5. the reaction conditions were as follows: the operating temperature was 100deg.C, the operating pressure was 1MPa, and the reaction time was 0.5 hours.
The rectification system comprises a light component removing tower and a heavy component removing tower. The theoretical plate number of the light component removal tower is 11, and light components such as water, aldehyde and the like are extracted from the top of the light component removal tower; the theoretical plate number of the weight removing tower is 24, qualified glycol products are extracted from the top of the weight removing tower, and the tower bottom is composed of components such as diethylene glycol, triethylene glycol and the like. The operating pressure of the light component removing tower is 10kPa, the temperature of the tower bottom is 133 ℃, the temperature of the tower top is 46 ℃, and the mass reflux ratio is 1.5. The operating pressure of the heavy-removal tower is 10kPa, the temperature of the tower bottom is 288 ℃, the temperature of the tower top is 132 ℃, and the mass reflux ratio is 3.
Analysis is carried out according to the ' determination of 4.2 glycol content ' in GB/T4649-2008 industrial glycol ' standard document, the accumulated removal rate of degradation impurities (calculated by total nitrogen) by a pre-reaction-rectification coupling process is 92%, and the mass purity of glycol is 99.9%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 95Hazen.
[ Example 3]
The crude ethylene glycol feed composition, separation process steps and apparatus for recovering ethylene glycol during the production of polyesteramide used in this example are the same as in example 1. The only difference from example 1 is the adjustment of the pre-reaction and rectification process parameters, as follows:
The crude ethylene glycol pre-reaction auxiliary agent is malonyl chloride, and the ratio of the crude ethylene glycol to the auxiliary agent is 1000:1. the reaction conditions were as follows: the operating temperature was 50℃and the operating pressure was 0.5MPa, and the reaction time was 0.2 hours.
The rectification system comprises a light component removing tower and a heavy component removing tower. The theoretical plate number of the light component removal tower is 6, and light components such as water, aldehyde and the like are extracted from the top of the light component removal tower; the theoretical plate number of the de-weight tower is 11, qualified ethylene glycol is extracted from the top of the de-weight tower, and the tower bottom is composed of diethylene glycol, triethylene glycol and other heavy components. The operating pressure of the light component removing tower is 30kPa, the temperature of the tower bottom is 161 ℃, the temperature of the tower top is 69 ℃, and the mass reflux ratio is 0.5. The operating pressure of the heavy-removal tower is 30kPa, the tower bottom temperature is 336 ℃, the tower top temperature is 160 ℃, and the mass reflux ratio is 1.
Analysis was carried out according to the "determination of 4.2 glycol content" in the standard document of GB/T4649-2008 industrial glycol, the cumulative removal rate of degraded impurities (calculated as total nitrogen) by the pre-reaction-rectification coupling process was 78%, and the mass purity of glycol was 99.7%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 270Hazen.
[ Example 4]
This example differs from example 3 only in that the crude ethylene glycol pre-reaction auxiliary is oxalyl chloride, otherwise identical to example 3.
Analysis was carried out according to the "determination of 4.2 glycol content" in the standard document of GB/T4649-2008 industrial glycol, the cumulative removal rate of degraded impurities (calculated as total nitrogen) by the pre-reaction-rectification coupling process was 77%, and the mass purity of glycol was 99.7%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 300Hazen.
[ Example 5]
This example differs from example 2 only in that the crude ethylene glycol pre-reaction auxiliary is succinyl chloride, otherwise the same as example 2.
Analysis was carried out according to the "determination of 4.2 glycol content" in the standard document of GB/T4649-2008 industrial glycol, the cumulative removal rate of degraded impurities (calculated as total nitrogen) by the pre-reaction-rectification coupling process was 93wt%, and the mass purity of glycol was 99.9%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 80Hazen.
[ Example 6]
This example differs from example 3 only in that the crude ethylene glycol pre-reaction temperature was adjusted to 20℃and otherwise the same as example 3.
Analysis is carried out according to the ' determination of 4.2 glycol content ' in GB/T4649-2008 industrial glycol ' standard document, the accumulated removal rate of degradation impurities (calculated by total nitrogen) by a pre-reaction-rectification coupling process is 65%, and the mass purity of glycol is 99.5%. The platinum-cobalt thermochromate of the crude ethylene glycol is greater than 500Hazen, and after separation, the platinum-cobalt thermochromate of the obtained ethylene glycol product is reduced to 360Hazen.
Comparative example 1
This comparative example differs from example 3 only in that the amount of crude ethylene glycol pre-reaction auxiliary was adjusted to 0, otherwise as in example 3.
Analysis is carried out according to the ' determination of 4.2 glycol content ' in GB/T4649-2008 industrial glycol ' standard document, the accumulated removal rate of degradation impurities (calculated by total nitrogen) by a pre-reaction-rectification coupling process is 20%, and the mass purity of glycol is 98.7%. The platinum cobalt thermochromate before and after the purification of the crude glycol is more than 500Hazen.
Comparative example 2
The crude ethylene glycol material, separation process steps and apparatus for recovering ethylene glycol during the production of polyesteramide used in this comparative example were the same as in example 3. The comparative example differs from example 3 only in the adjustment of the parameters of the rectification process section, in particular as follows: the operating pressure of the light component removing tower is 80kPa, the temperature of the tower bottom is 190 ℃ and the temperature of the tower top is 94 ℃. The operating pressure of the weight removing tower is 80kPa, the temperature of the tower bottom is 371 ℃, and the temperature of the tower top is 190 ℃.
Analysis is carried out according to the ' determination of 4.2 glycol content ' in GB/T4649-2008 industrial glycol ' standard document, the accumulated removal rate of degradation impurities (calculated by total nitrogen) by a pre-reaction-rectification coupling process is 40%, and the mass purity of glycol is 99.1%. The platinum cobalt thermochromate before and after the purification of the crude glycol is more than 500Hazen.
The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (11)
1.A separation method for recycling glycol in a polyester production process, comprising:
S1, reacting a crude ethylene glycol raw material with an acyl chloride auxiliary agent to obtain a pretreated mixed material;
s2, rectifying and separating the pretreated mixture to obtain a light component, an ethylene glycol product and a heavy component;
In step S1, the crude ethylene glycol includes ethylene glycol and further includes impurities including chain or cyclic aldehydes, chain or cyclic ketones, and chain or cyclic nitrogen-containing impurities; the thermal color degree of the crude ethylene glycol platinum cobalt is more than 500Hazen, and the mass content of the impurities calculated by total nitrogen element is not less than 5ppm;
In the step S1, the acyl chloride auxiliary agent is at least one selected from oxalyl chloride, malonyl chloride and succinyl chloride, and the mass ratio of the raw material of the crude ethylene glycol to the acyl chloride auxiliary agent is 1000: (0.9 to 5.3);
In the step S2, rectification separation comprises light separation and heavy separation; the operating conditions for the light separation are as follows: the pressure is 9-33 kPa by absolute pressure, the temperature of the tower bottom is 120-177 ℃, the temperature of the tower top is 41-76 ℃, and the mass reflux ratio is 0.4-1.6; the operating conditions of the heavy separation are as follows: the pressure is 9-32 kPa by absolute pressure, the temperature of the tower bottom is 274-353 ℃, the temperature of the tower top is 125-168 ℃, and the mass reflux ratio is 0.9-3.2.
2. The method of claim 1 wherein the polyester is polyethylene terephthalate, or a copolymer of polyethylene terephthalate and polyamide, or a copolymer of terephthalic acid, ethylene glycol and caprolactam.
3. The method of claim 1 wherein the polyester is a copolymer of polyethylene terephthalate and polyamide or a copolymer of terephthalic acid, ethylene glycol and caprolactam.
4. The method of claim 1, wherein in step S1, the raw ethylene glycol material is a raw ethylene glycol-containing material; the crude ethylene glycol is derived from a byproduct material rich in ethylene glycol in the polyester production process.
5. The method according to claim 1, wherein in the step S1, the mass content of ethylene glycol in the raw ethylene glycol material is 75% to 95%.
6. The method according to claim 5, wherein in step S1, the mass content of the impurity, based on the total nitrogen element, is not less than 50ppm.
7. The method according to claim 5, wherein in step S1, the mass content of the impurity, based on the total nitrogen element, is not less than 100ppm.
8. The method of claim 1, wherein the impurities comprise water, acetaldehyde, N-ethylmorpholine, morpholinoethanol, N-methyl-3-pyrrolin-2-one, caprolactam, acetamide, caproamide, glutarimide, succinimide, 2-vinyl-pyrrolinone, and diacetamide.
9. The method of claim 8, wherein the impurities further comprise at least one of pyridine, 2-methyl-1, 3-dioxolane, cyclopentanone, amino formaldehyde, diethylene glycol, triethylene glycol.
10. The method according to claim 1, wherein in step S1, the reaction conditions are as follows: the temperature is 48-105 ℃, the pressure is 0.47-1.05 MPa, and the reaction time is 0.19-0.53 hours.
11. The method according to claim 1, wherein in the step S2, the rectifying tower adopted for the light component removal and separation is a light component removal tower, the theoretical plate number is 5-12, the light component is extracted from the top of the light component removal tower, and the stream containing glycol is taken as the feed of the heavy component removal tower at the bottom of the tower; the weight-removing separation adopts a rectifying tower as a weight-removing tower, and the theoretical plate number is 10-25; and (3) extracting ethylene glycol products from the tower top or side line of the heavy-component removing tower, wherein the tower bottom is a heavy component.
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