CN114425237A - Separation device and method for recovering crude ethylene glycol near-azeotropic impurities in polyester production process - Google Patents

Separation device and method for recovering crude ethylene glycol near-azeotropic impurities in polyester production process Download PDF

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CN114425237A
CN114425237A CN202011078490.9A CN202011078490A CN114425237A CN 114425237 A CN114425237 A CN 114425237A CN 202011078490 A CN202011078490 A CN 202011078490A CN 114425237 A CN114425237 A CN 114425237A
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chloride
glycol
membrane
separation device
crude
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CN114425237B (en
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宋海峰
刘俊涛
孙凤侠
龚海燕
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Water Supply & Treatment (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention relates to a separation device and a separation method for recovering near-azeotropic impurities of crude ethylene glycol in a polyester production process. The invention adopts a membrane separation unit containing a composite membrane to treat near-azeotropic impurities. The composite film comprises a base film and a composite layer attached to the surface of the base film. The invention adopts a membrane separation process based on molecular morphology difference to replace a common rectification process, and is used for effectively separating impurities in crude glycol recovered in the polyester production process so as to solve the problem of separation of near-azeotropic components. Can be used in the industrial production of the glycol purification in the polyester recovery.

Description

Separation device and method for recovering crude ethylene glycol near-azeotropic impurities in polyester production process
Technical Field
The invention relates to a separation device and a separation method for recovering near-azeotropic impurities in crude glycol, in particular to a separation device and a separation method for recovering near-azeotropic impurities in crude glycol in the polyester production process.
Background
Chemical fiber is used as basic industry of textile industry and is always the key industry of Chinese planning and development. The polyester fiber accounts for 75 to 80 percent of the chemical fiber yield in China. Super-cotton-like technology represents the highest level of synthetic fiber development. The development of the super-simulation cotton fiber from polyester is not only because of the high productivity of the polyester fiber, compared with other chemical fiber varieties, the super-simulation cotton fiber has higher overall technical level and has a super-simulation foundation, but also is a main variety blended with cotton.
At present, the development direction of the polyester super-imitation cotton technology is mainly to introduce a polymer with an amide group into the synthesis preparation process of PET for copolymerization to obtain polyesteramide. The polyamide chain segment is introduced between the polyethylene glycol terephthalate chain segments, so that the polarity of the whole molecular chain is enhanced, the hydrogen bond acting force between the molecular chains and the cohesive energy density of the copolyamide ester are improved, the dyeing processing of subsequent fibers is facilitated, and the gas barrier property of the polyesteramide is improved.
The production process of the polyesteramide comprises the following steps: esterification is carried out on a certain amount of terephthalic acid, glycol and catalyst 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, components such as water, degradation products and unreacted glycol generated in a polyester reactor are pumped out to a crude glycol storage tank through a vacuum system, and are recovered by a glycol refining system.
The processing method of crude glycol pumped out by a vacuum system at present mainly comprises the following steps:
1. no ethylene glycol recovery refining unit: patent CN1054988A discloses a method for continuous production of polyester by direct esterification, wherein the process does not add a recovery and purification device to recover and purify the ethylene glycol in excess system, but directly returns the ethylene glycol condensed by a vacuum system to be used as raw material. The process can lead to the accumulation of aldehydes and acetals generated by the degradation of the polyester in a system, and the color of the polyester is increasingly poor.
2. A single process tower is arranged for ethylene glycol refining: patent CN101575122A discloses a method for refining crude ethylene glycol by using a process tower and a stripping tower, wherein the refined ethylene glycol is obtained from the tower bottom of the process tower, and the components such as water and aldehydes are obtained from the tower top, and then the wastewater is treated by the stripping tower. In the process, heavy component impurities generated by degradation cannot be separated, and the impurities are accumulated in a system, so that the chromaticity of the polyester is not up to the standard. The "transformation of esterification process tower" published in 2008, 2 nd 21 in polyester industry, also recovers crude ethylene glycol through a single process tower, and also causes the purity of refined ethylene glycol not to reach the standard.
Therefore, in the prior art, the ethylene glycol recovered from the polyester is mainly separated by common rectification or is directly recycled without any separation. The components of the crude glycol recovered in the preparation process of polyesteramide are more complex compared with the crude glycol recovered in the preparation process of conventional polyester, mainly because the high molecular polymer such as polyamide or the oligomer thereof is generally stable at normal temperature, but side reactions such as etherification, cyclization, thermal degradation, thermal oxidative degradation and the like can be generated in the polymerization reaction process to generate acetaldehyde, 2-methyl-1, 3-dioxolane, N-ethylmorpholine, morpholine ethanol, pyridine, acetic acid, cyclopentanone, amino formaldehyde, butyrolactone, valerolactone, glutarimide, succinimide, N-methyl-3-pyrroline-2-one, 2-vinyl-pyrroline, caprolactam, acetamide, diethylamide, hexanamide and the like, and in the system, due to the interaction influence of different chemical components, part of impurity components and the ethylene glycol have non-ideal gas-liquid equilibrium behavior in the rectification process, namely, the phenomenon of near azeotropic property, even if the difference between the boiling points of part of impurities and glycol is large, effective separation is difficult to realize by adopting conventional rectification, and the color index of the polyester or polyesteramide can not reach the standard (mainly the color of the polyester is yellow, even blackened and the like) when the strand of material returns to the polymerization reaction again. Therefore, the problem of separating near-azeotropic impurities is one of the key technical bases for the large-scale production of polyesters, particularly polyesteramides.
Disclosure of Invention
The invention aims to solve the technical problem of high content of near-azeotropic impurities in recycled ethylene glycol in the existing polyester production process, and provides a separation device and a separation method of the near-azeotropic impurities in crude ethylene glycol recycled in the polyester production process.
In order to solve the above technical problems, a first aspect of the present invention provides a separation apparatus for separating near-azeotropic impurities from crude ethylene glycol recovered in a polyester production process, the separation apparatus comprising a composite membrane unit including a base membrane and a composite layer attached to a surface of the base membrane. The composite layer is composed of polyamine and polyacyl chloride.
In the technical scheme, the thickness of the base film is 20-50 mu m, and the thickness of the composite layer is 3-5 mu m. The basement membrane is prepared from polysulfone, polyethersulfone, polyaryletherketone, polyvinyl chloride or polycarbonate, or derivatives thereof, or a mixture of one or more of the polysulfone, the polyethersulfone, the polyaryletherketone, the polyvinyl chloride or the polycarbonate by an L-S phase inversion method. The L-S phase inversion process is a well-known inversion process. The molecular weight cut-off of the basement membrane is 1000-5000 daltons according to the method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 Ultrafiltration Membrane test method '; the molecular weight cut-off of the composite membrane is 100-500 daltons.
In the above technical solution, the separation apparatus is preferably provided with an impurity pretreatment unit before the composite membrane unit, the impurity pretreatment unit includes:
the mixing and heating unit is used for mixing and heating the crude glycol and the reaction auxiliary agent;
the reaction unit is used for providing a reaction site of the crude glycol and the reaction auxiliary agent; and
and the cooling unit is used for cooling the reaction product of the crude glycol and the reaction auxiliary agent.
In the above technical scheme, the preparation process of the composite membrane comprises the following steps:
s1) respectively preparing polyamine solution and polyacyl chloride solution;
s2) dipping the basement membrane in polyamine solution, and scraping free liquid to obtain an amine modified basement membrane;
s3) dipping the amine modified basement membrane obtained in the step S2) in polyacylchloride solution, scraping free liquid, drying and washing to obtain the composite membrane.
In the above technical scheme, the polyamine is p-xylylenediamine, o-xylylenediamine, m-xylylenediamine, mesitylene-trimethylamine, p-xylylenediamine, o-phenylenediethylamine, m-phenylenediethylamine, mesitylene-triethylamine, p-phenylenediethylamine, o-phenylenedipropylamine, m-phenylenedipropylamine, mesitylene-tripropylamine, piperazine, 4-piperazinopiperidine, homopiperazine, 2' -bipyrazine or 2-methylpiperazine, or a derivative of two or more of the above components, or a mixture of two or more of them. Preferably, the polyamine is a mixture of one or more of p-xylylenediamine, o-xylylenediamine, m-xylylenediamine, mesitylene-trimethylamine, p-phenylenediethylamine, o-phenylenediethylamine, m-phenylenediethylamine, mesitylene-triethylamine, p-phenylenedipropylamine, o-phenylenedipropylamine, m-phenylenedipropylamine or s-phenylenedipropylamine and one or more of piperazine, 4-piperazinopiperidine, homopiperazine, 2' -bipyrazine or 2-methylpiperazine, preferably an equimolar mixture. In the polyamine solution, the mass concentration of polyamine is 2-5%, and the rest is water.
In the above technical scheme, the poly-acyl chloride is isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride, trimesoyl chloride, glutaryl dichloride, azelaioyl chloride, malonyl chloride, oxalyl chloride, adipoyl chloride, 1, 7-pimeloyl chloride, 1, 8-dioctanoyl chloride, 4' -diacyl diphenyl ether or 1, 4-cyclohexanedicarboxylic acid chloride, or a derivative of the above components, or a mixture of two or more of them. Preferably, the polybasic acyl chloride is a mixture of one or more of isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride, trimesoyl chloride, isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride and pyromellitic triacetyl chloride with one or more of glutaryl dichloride, azelaioyl chloride, malonyl chloride, oxalyl chloride, adipoyl chloride, 1, 7-pimeloyl chloride, 1, 8-dioctanoyl chloride, 4' -diacyl diphenyl ether and 1, 4-cyclohexanedicarboxylic acid dichloride, preferably an equimolar mixture. . The mass concentration of the polybasic acyl chloride in the polybasic acyl chloride solution is 0.3-1.5%, and the rest components are alkane solvents. The alkane solvent is normal alkane or isoparaffin, preferably one or more of n-hexane, cyclohexane and n-heptane.
In the above technical solution, the polyamine solution in step S1) further includes sodium dodecylbenzenesulfonate, ethylenediamine and/or triethylene glycol as a structural adjustment auxiliary. The mass concentration of the sodium dodecyl benzene sulfonate is 0.4-1%, the mass concentration of the ethylene diamine is 2-5%, and the mass concentration of the triethylene glycol is 5-10%. The sodium dodecyl benzene sulfonate is used for adjusting the thickness of a micro interface of a polyamine aqueous solution in an acyl chloride organic solution; the ethylene diamine is used for neutralizing reaction products and promoting chemical equilibrium movement; the triethylene glycol is used to improve the selective permeability of the finished film to ethylene glycol.
In the above technical solution, the polybasic acid chloride solution in step S1) preferably includes 1, 2-octanediol. The 1, 2-octanediol is used for adjusting the thickness of the micro-interface of the polybasic acyl chloride organic solution in the polyamine aqueous solution. The mass concentration of the 1, 2-octanediol is 0.5 to 1 percent.
In the technical scheme, the modified base film obtained in the step S2) is soaked in the polyamine solution for 3-8 minutes at the soaking temperature of 25 +/-4 ℃; scraping free liquid by using a scraper, and then soaking in a polyacyl chloride solution for 5-20 seconds at the temperature of 25 +/-4 ℃; scraping free liquid by a scraper, and drying in a nitrogen atmosphere at the drying temperature of 100-130 ℃ for 5-15 minutes; and cooling to normal temperature to obtain the composite film.
According to the invention, the polyamide or polypiperazine amide composite layer prepared according to the characteristics of impurity distribution in the polyester recovered glycol is measured according to the method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the cut-off molecular weight is 100-500 daltons.
In the technical scheme, the polyester is polyethylene terephthalate, a copolymer of polyethylene terephthalate and polyamide, and a copolymer of terephthalic acid, ethylene glycol and caprolactam. Preference is given to copolymers of polyethylene terephthalate and polyamide, copolymers of terephthalic acid, ethylene glycol and caprolactam. The near-azeotropic impurities in the crude ethylene glycol include: acetaldehyde, 2-methyl-1, 3-dioxolane, N-ethylmorpholine, morpholinoethanol, pyridine, acetic acid, cyclopentanone, amino formaldehyde, butyrolactone, valerolactone, glutarimide, succinimide, N-methyl-3-pyrrolin-2-one, 2-vinyl-pyrrolinone, caprolactam, acetamide, diethylamide, caproamide and the like.
The second aspect of the invention provides a separation method for separating near-azeotropic impurities in crude ethylene glycol recovered in a polyester production process, which comprises the following steps:
s1) mixing the crude glycol containing the near-azeotropic impurities with an organic acid reaction auxiliary agent, heating after mixing for a pretreatment reaction to obtain pretreated crude glycol;
s2) performing membrane filtration on the pretreated crude glycol to remove near-azeotropic impurities in the crude glycol.
In the technical scheme, the crude glycol containing the near-azeotropic impurities in the pretreatment process in the step S1) reacts with the organic acid reaction auxiliary agent to realize the molecular conversion of the near-azeotropic impurities and improve the rejection rate of the subsequent membrane to the impurities. The organic acid reaction auxiliary agent is preferably one or more of 2, 2-dimethylsuccinic acid, 2, 3-dimethylsuccinic acid, 2-dimethylglutaric acid, 2-diethyladipic acid, 2, 3-dimethylbenzoic acid, 2, 4-dimethylbenzoic acid and 2, 5-dimethylbenzoic acid. The proportion of the crude glycol containing the near-azeotropic impurities to the reaction auxiliary agent is (0.5-5) 100 by mass. The reaction temperature of the pretreatment reaction is 50-100 ℃, and the reaction time is 30-120 minutes. After the reaction is finished, the reaction product is preferably cooled to 20-40 ℃.
In the technical scheme, the operating pressure of the composite membrane is 1-3 MPa in absolute pressure, and the operating temperature is 20-60 ℃; the rejection rate of the membrane component to the near-boiling point impurities in the crude glycol recovered in the polyester production process is 60-98%.
In conclusion, the invention adopts the membrane separation process based on the molecular morphology difference to replace the common rectification process, and is used for effectively separating impurities in the crude glycol recovered in the polyester production process so as to solve the problem of separation of near-azeotropic components. Compared with the prior art, the invention has the following advantages: 1. the polyamide or polypiperazine monomer is optimized, so that the separation performance of the composite layer is improved; 2. the thickness of the composite layer and the selective permeability of the components are comprehensively adjusted by adding a structure modulation auxiliary agent in the polymerization process; 3. the impurity components are treated and converted, so that the rejection rate of the membrane to impurities is further improved. The technical scheme ensures that the retention rate of impurities in the crude glycol is up to 90-98%, better solves the problem that the content of near-boiling-point impurities in recycled glycol products in the prior art is high, and can be used in industrial production of polyester recycled glycol purification.
Detailed Description
The technical solution of the present invention is exemplarily described below with reference to specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without making any creative effort, shall not be beyond the protection scope of the present invention.
In one embodiment, the present invention provides a separation apparatus for separating near-azeotropic impurities from crude ethylene glycol recovered from a polyester production process, the separation apparatus comprising a composite membrane unit comprising a base membrane and a composite layer attached to a surface of the base membrane. The composite layer is composed of polyamine and polyacyl chloride. The preparation and properties of the composite membrane are shown in specific examples.
The separation device is selectively provided with an impurity pretreatment unit in front of the composite membrane unit, and the impurity pretreatment unit comprises:
the mixing and heating unit is used for mixing and heating the crude glycol and the reaction auxiliary agent;
the reaction unit is used for providing a reaction site of the crude glycol and the reaction auxiliary agent; and
and the cooling unit is used for cooling the reaction product of the crude glycol and the reaction auxiliary agent.
[ example 1 ]
This example separated the near-azeotropic impurities of crude ethylene glycol recovered from a polyester production process.
The polyester is a copolymer of terephthalic acid, ethylene glycol and caprolactam, the mass composition of crude ethylene glycol extracted by a polyester vacuum system fluctuates to a certain degree, and the mass composition of the crude ethylene glycol in the embodiment is as follows: 80% of ethylene glycol, 10% of water, 5% of caprolactam, 0.6% of acetaldehyde, 0.4% of 2-methyl-1, 3-dioxolane, 0.2% of N-ethylmorpholine, 0.2% of morpholine ethanol, 0.8% of cyclopentanone, 0.3% of amino formaldehyde, 0.7% of succinimide, 0.5% of N-methyl-3-pyrroline-2-one, 0.8% of acetamide, 0.3% of diethylamide and 0.2% of hexanamide.
The separation process of this example uses the aforementioned separation apparatus, wherein the thickness of the base film is 35 μm, and a 4 μm composite layer is attached to the surface of the base film. The molecular weight cut-off of the composite membrane is 300 daltons. The basement membrane is prepared from polysulfone according to an L-S phase inversion method. The L-S phase inversion process is a well-known inversion process. The molecular weight cut-off of the basement membrane is 2500 daltons according to the method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 Ultrafiltration Membrane test method '.
The composite layer is prepared from polyamine and polyacyl chloride according to an interfacial polymerization method. The preparation process of the composite membrane comprises the following steps:
s1) respectively preparing polyamine aqueous solution and polyacyl chloride organic solution;
the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine aqueous solution, the mass concentration of polyamine is 3.5%, the mass concentration of sodium dodecyl benzene sulfonate is 0.7%, the mass concentration of ethylenediamine is 3.5%, the mass concentration of triethylene glycol is 7.5%, and the balance is water. In the polybasic acyl chloride organic solution, the mass concentration of the polybasic acyl chloride is 0.9 percent, the mass concentration of the 1, 2-octanediol is 0.75 percent, and the rest components are n-hexane solvent.
S2) immersing the base film in an aqueous polyamine solution;
the impregnation time was 5 minutes and the impregnation temperature was 25 ℃. And scraping free liquid after dipping to obtain the amine modified basement membrane.
S3) immersing the amine-modified base film obtained in the step S2) in a polybasic acid chloride organic solution.
The immersion time in the polyacyl chloride organic solution was 12 seconds, and the immersion temperature was 25 ℃. And (4) scraping free liquid after dipping, drying and washing to obtain the composite membrane. The drying temperature was 115 ℃ and the drying time was 10 minutes. The washing process is to wash the mixture by adopting a large amount of desalted water until the electric conductivity is less than or equal to 5 mu S/cm.
The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 300 daltons. According to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling point impurities is 70%.
The embodiment provides a separation method for recovering near-azeotropic impurities of crude ethylene glycol in a polyester production process, which comprises the following steps:
s1) mixing the crude glycol containing the near-azeotropic impurities with an organic acid reaction auxiliary agent, heating after mixing, and carrying out pretreatment to obtain pretreated crude glycol; the reaction auxiliary agent is 2, 2-diethyl adipic acid. The ratio of the crude glycol to the reaction auxiliary agent is 100:2.5 in parts by weight. Mixing the crude glycol and 2, 2-diethyl adipic acid, heating the mixed solution to 70 ℃, keeping the reaction at 70 ℃ for 60 minutes, and cooling to 30 ℃ to obtain the pretreated crude glycol.
S2) carrying out membrane filtration on the crude glycol after impurity pretreatment to remove near-azeotropic impurities in the crude glycol.
The operating pressure of the prepared composite membrane is 2MPa in absolute pressure and the operating temperature is 40 ℃ in the membrane filtration process; the rejection rate of the membrane component to the near-boiling point impurities in the crude glycol recovered in the polyester production process is 95%.
[ example 2 ]
The process flow and the crude ethylene glycol raw material were the same as in example 1.
The separation process of this example uses the aforementioned separation apparatus, wherein the thickness of the base film is 20 μm, and a 3 μm composite layer is attached to the surface of the base film.
The reaction auxiliary agent is 2, 2-diethyl adipic acid; the proportion of the crude glycol to the reaction auxiliary agent is 100:0.5 in parts by mass; the mixing heating temperature of the crude glycol and the reaction auxiliary agent is 50 ℃, the reaction temperature is 50 ℃, the reaction time is 30 minutes, and the cooling temperature is 40 ℃.
The basement membrane is prepared from polyether sulfone according to a known L-S phase inversion method, and has a molecular weight cutoff of 5000 daltons. The composite layer is prepared from polyamine and polyacyl chloride according to a known interfacial polymerization method; the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine solution for preparing the composite membrane, the mass concentration of polyamine is 2%, the mass concentration of sodium dodecyl benzene sulfonate is 0.4%, the mass concentration of ethylenediamine is 2%, the mass concentration of triethylene glycol is 5%, and the balance is water. In the polybasic acyl chloride solution used for preparing the composite membrane, the mass concentration of the polybasic acyl chloride is 0.3 percent, the mass concentration of the 1, 2-octanediol is 0.5 percent, and the rest components are alkane solvents. The preparation method is used for the preparation process of the composite membrane, the dipping time of polyamine is 3 minutes, the dipping time of polyacyl chloride is 5 seconds, the drying temperature is 100 ℃, and the drying time is 5 minutes. The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 500 daltons. The operating pressure of the composite membrane is 1MPa in absolute pressure, and the operating temperature is 60 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling point impurities is 90%.
[ example 3 ]
The process flow and the crude ethylene glycol raw material were the same as in example 1.
The separation process of this example uses the aforementioned separation apparatus, wherein the thickness of the base film is 50 μm, and a 5 μm composite layer is attached to the surface of the base film.
The reaction auxiliary agent is 2, 2-diethyl adipic acid; the ratio of the crude glycol to the reaction auxiliary agent is 100:5 in parts by mass; the mixing heating temperature of the crude glycol and the reaction auxiliary agent is 100 ℃, the reaction temperature is 100 ℃, the reaction time is 120 minutes, and the cooling temperature is 20 ℃.
The basement membrane is prepared from polyether sulfone according to a known L-S phase inversion method, and the molecular weight cut-off of the basement membrane is 1000 daltons. The composite layer is prepared from polyamine and polyacyl chloride according to a known interfacial polymerization method; the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine solution for preparing the composite membrane, the mass concentration of polyamine is 5%, the mass concentration of sodium dodecyl benzene sulfonate is 1%, the mass concentration of ethylenediamine is 5%, the mass concentration of triethylene glycol is 10%, and the balance is water. In the polybasic acyl chloride solution used for preparing the composite membrane, the mass concentration of the polybasic acyl chloride is 1.5 percent, the mass concentration of 1, 2-octanediol is 1 percent, and the rest components are alkane solvents. The preparation method is used for the preparation process of the composite membrane, the soaking time of polyamine is 8 minutes, the soaking time of polyacyl chloride is 20 seconds, the drying temperature is 130 ℃, and the drying time is 15 minutes. The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 100 daltons. The operating pressure of the composite membrane is 3MPa in absolute pressure, and the operating temperature is 20 ℃; according to the determination of 4.2 glycol yield in the standard document of GB/T4649-2008 industrial glycol, the rejection rate of the membrane component on near-boiling-point impurities is 98%.
[ example 4 ]
The process flow, raw ethylene glycol, and pre-treatment process of crude ethylene glycol were the same as in example 1.
The separation process of this example used the aforementioned separation apparatus, wherein the thickness of the base film was 27 μm, and a 3.4 μm composite layer was attached to the surface of the base film.
The basement membrane is prepared from polyether sulfone according to a known L-S phase inversion method, and has a molecular weight cutoff of 2500 daltons. The composite layer is prepared from polyamine and polyacyl chloride according to a known interfacial polymerization method; the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine solution for preparing the composite membrane, the mass concentration of polyamine is 2.4%, the mass concentration of sodium dodecyl benzene sulfonate is 0.47%, the mass concentration of ethylenediamine is 2.3%, the mass concentration of triethylene glycol is 5.6%, and the balance is water. In the polybasic acyl chloride solution used for preparing the composite membrane, the mass concentration of the polybasic acyl chloride is 0.45 percent, the mass concentration of the 1, 2-octanediol is 0.56 percent, and the rest components are alkane solvents. The preparation method is used for the preparation process of the composite membrane, the soaking time of polyamine is 3.6 minutes, the soaking time of polyacyl chloride is 6.8 seconds, the drying temperature is 103 ℃, and the drying time is 6.25 minutes. The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 400 daltons. The operating pressure of the composite membrane is 2MPa in absolute pressure, and the operating temperature is 40 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component to near-boiling-point impurities is 93%.
[ example 5 ]
The process flow, raw ethylene glycol, and pre-treatment process of crude ethylene glycol were the same as in example 1.
The separation process of this example used the aforementioned separation apparatus, wherein the thickness of the base film was 43 μm, and a 4.4 μm composite layer was attached to the surface of the base film.
The basement membrane is prepared from polyether sulfone according to a known L-S phase inversion method, and has a molecular weight cutoff of 2500 daltons. The composite layer is prepared from polyamine and polyacyl chloride according to a known interfacial polymerization method; the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine solution for preparing the composite membrane, the mass concentration of polyamine is 4.6%, the mass concentration of sodium dodecyl benzene sulfonate is 0.92%, the mass concentration of ethylenediamine is 4.6%, the mass concentration of triethylene glycol is 9.3%, and the balance of water. In the polybasic acyl chloride solution used for preparing the composite membrane, the mass concentration of the polybasic acyl chloride is 1.35%, the mass concentration of 1, 2-octanediol is 0.93%, and the rest components are alkane solvents. The preparation method is used for the preparation process of the composite membrane, the soaking time of polyamine is 7.4 minutes, the soaking time of polyacyl chloride is 18 seconds, the drying temperature is 126 ℃, and the drying time is 13 minutes. The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 200 daltons. The operating pressure of the composite membrane is 2MPa in absolute pressure, and the operating temperature is 40 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling-point impurities is 96%.
[ example 6 ]
The process flow, crude ethylene glycol raw material, raw material pretreatment process were the same as in example 1.
The basement membrane is prepared from polyether sulfone according to a known L-S phase inversion method, and has a molecular weight cutoff of 2500 daltons. The composite layer is prepared from polyamine and polyacyl chloride according to a known interfacial polymerization method; the polyamine is an equimolar mixture of trimesamine and 4-piperazine piperidine; the polybasic acyl chloride is equimolar mixture of trimesoyl chloride and 1, 7-pimeloyl chloride. In the polyamine solution for preparing the composite membrane, the mass concentration of polyamine is 3.5%, the mass concentration of sodium dodecyl benzene sulfonate is 0.7%, the mass concentration of ethylenediamine is 3.5%, the mass concentration of triethylene glycol is 0%, and the balance of water. In the polybasic acyl chloride solution used for preparing the composite membrane, the mass concentration of the polybasic acyl chloride is 0.9 percent, the mass concentration of the 1, 2-octanediol is 0 percent, and the rest components are alkane solvents. The preparation method is used for the preparation process of the composite membrane, the soaking time of polyamine is 5 minutes, the soaking time of polyacyl chloride is 12 seconds, the drying temperature is 115 ℃, and the drying time is 10 minutes. The molecular weight cut-off of the prepared composite membrane is determined according to a method of ' 5.2 cut molecular weight ' in the standard GB/T32360-2015 ultrafiltration membrane test method ', and the molecular weight cut-off of the composite membrane is 350 daltons. The operating pressure of the composite membrane is 2MPa in absolute pressure, and the operating temperature is 40 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling point impurities is 85%.
Comparative example 1
The process flow and the raw material of the crude glycol are the same as those in example 1, and the membrane module adopts a commercial membrane module SUEZ-DK8040F30 (the molecular weight cut-off is 150-300 daltons). The operating pressure of membrane separation is 2MPa in absolute pressure, and the operating temperature is 40 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling-point impurities is 30%.
Comparative example 2
The process flow, the crude ethylene glycol raw material and the composite membrane preparation method are the same as those of example 2.
When the mass portion of the reaction auxiliary agent 2, 2-diethyladipic acid is 0, the operating pressure of the composite membrane is 1MPa in absolute pressure, and the operating temperature is 60 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component on near-boiling-point impurities is 60%.
Comparative example 3
The process flow, the crude ethylene glycol raw material and the composite membrane preparation method were the same as in example 3.
When the mass portion of the reaction auxiliary agent 2, 2-diethyladipic acid is 0, the operating pressure of membrane separation is 3MPa in absolute pressure, and the operating temperature is 20 ℃; according to the determination of 4.2 ethylene glycol yield in the standard document of GB/T4649-2008 industrial ethylene glycol, the rejection rate of the membrane component to near-boiling point impurities is 80%.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (19)

1. A separation apparatus for separating near-azeotropic impurities from crude ethylene glycol recovered from a polyester production process, the separation apparatus comprising a composite membrane unit comprising a base membrane and a composite layer attached to a surface of the base membrane.
2. The separation device of claim 1, wherein the composite layer is comprised of a polyamine and a polyacyl chloride.
3. The separation device of claim 1, wherein the thickness of the base film is 20 to 50 μm, and the thickness of the composite layer is 3 to 5 μm.
4. The separation device of claim 1, wherein the molecular weight cut-off of the membrane is 1000 to 5000 daltons; the molecular weight cut-off of the composite membrane is 100-500 daltons.
5. The separation device according to claim 1, wherein the separation device is provided with an impurity pretreatment unit before the composite membrane unit, the impurity pretreatment unit comprising:
the mixing and heating unit is used for mixing and heating the crude glycol and the reaction auxiliary agent;
the reaction unit is used for providing a reaction site of the crude glycol and the reaction auxiliary agent; and
and the cooling unit is used for cooling the reaction product of the crude glycol and the reaction auxiliary agent.
6. A separation device according to any one of claims 1 to 4, wherein the preparation of the composite membrane comprises the steps of:
s1) respectively preparing polyamine solution and polyacyl chloride solution;
s2) dipping the basement membrane in polyamine solution, and scraping free liquid to obtain an amine modified basement membrane;
s3) dipping the amine modified basement membrane obtained in the step S2) in polyacylchloride solution, scraping free liquid, drying and washing to obtain the composite membrane.
7. The separation device according to claim 6, wherein the polyamine is p-xylylenediamine, o-xylylenediamine, m-xylylenediamine, mesitylene-trimethylamine, p-phenylenethylamine, o-phenylenethylamine, m-phenylenethylamine, p-phenylenethylamine, o-phenylenedipropylamine, m-phenylenedipropylamine, s-phenylenedipropylamine, piperazine, 4-piperazinopiperidine, homopiperazine, 2' -bipyrazine or 2-methylpiperazine, or a derivative of two or more thereof; preferably, the polyamine is a mixture of one or more of p-xylylenediamine, o-xylylenediamine, m-xylylenediamine, mesitylene-trimethylamine, p-xylylenediamine, o-xylylenediamine, m-xylylenediamine, mesitylene-triethylamine, p-xylylenediamine, o-dipropylamine, m-xylylenediamine or tripropylene-aniline and one or more of piperazine, 4-piperazinopiperidine, homopiperazine, 2' -bipyrazine or 2-methylpiperazine.
8. The separation device according to claim 6, wherein the mass concentration of the polyamine in the polyamine solution is 2-5%, and the balance is water.
9. The separation device according to claim 6, wherein the polybasic acid chloride is isophthaloyl chloride, terephthaloyl chloride, phthaloyl chloride, trimesoyl chloride, glutaryl dichloride, azelaioyl chloride, malonyl chloride, oxalyl chloride, adipoyl chloride, 1, 7-pimeloyl chloride, 1, 8-dioctanoyl chloride, 4' -diacyl diphenyl ether or 1, 4-cyclohexanedicarboxylic chloride, or a derivative of the above components, or a mixture of two or more thereof; preferably, the polybasic acyl chloride is a mixture of one or more of isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride, trimesoyl chloride, isophthaloyl dichloride, terephthaloyl dichloride, phthaloyl dichloride and pyromellitic triacetyl chloride with one or more of glutaryl dichloride, azelaioyl chloride, malonyl chloride, oxalyl chloride, adipoyl chloride, 1, 7-pimeloyl chloride, 1, 8-dioctanoyl chloride, 4' -diacyl diphenyl ether and 1, 4-cyclohexanedicarboxylic acid dichloride.
10. The separation device of claim 6, wherein the mass concentration of the polybasic acyl chloride in the polybasic acyl chloride solution is 0.3-1.5%, and the rest components are alkane solvents.
11. The separation device of claim 6, wherein in the polyamine solution of step S1), one or more of sodium dodecylbenzene sulfonate, ethylenediamine or triethylene glycol is included as a structure adjustment aid.
12. The separation device of claim 11, wherein the mass concentration of the sodium dodecyl benzene sulfonate is 0.4-1%, the mass concentration of the ethylene diamine is 2-5%, and the mass concentration of the triethylene glycol is 5-10%.
13. The separation device of claim 6, wherein step S1) comprises 1, 2-octanediol in the polyacyl chloride solution; the mass concentration of the 1, 2-octanediol is 0.5 to 1 percent.
14. The separation device according to claim 6, wherein the modified base membrane of step S2) is soaked in the polyamine aqueous solution for 3-8 minutes at 25 ± 4 ℃; dipping in a polyacyl chloride solution for 5-20 seconds at the dipping temperature of 25 +/-4 ℃; the drying temperature is 100-130 ℃, and the drying time is 5-15 minutes.
15. The separator according to claim 1, wherein said polyester is polyethylene terephthalate, a copolymer of polyethylene terephthalate and polyamide, a copolymer of terephthalic acid, ethylene glycol and caprolactam; preferably copolymers of polyethylene terephthalate and polyamide or copolymers of terephthalic acid, ethylene glycol and caprolactam; the near-azeotropic impurities in the crude ethylene glycol include: acetaldehyde, 2-methyl-1, 3-dioxolane, N-ethylmorpholine, morpholinoethanol, pyridine, acetic acid, cyclopentanone, amino formaldehyde, butyrolactone, valerolactone, glutarimide, succinimide, N-methyl-3-pyrrolin-2-one, 2-vinyl-pyrrolinone, caprolactam, acetamide, diethylamide, caproamide.
16. A separation process for separating near-azeotropic impurities in crude ethylene glycol recovered during polyester production, comprising the steps of:
s1) mixing the crude glycol containing the near-azeotropic impurities with an organic acid reaction auxiliary agent, heating after mixing for a pretreatment reaction to obtain pretreated crude glycol;
s2) performing membrane filtration on the pretreated crude glycol to remove near-azeotropic impurities in the crude glycol.
17. The separation method according to claim 16, wherein the organic acid reaction auxiliary in step S1) is one or more of 2, 2-dimethylsuccinic acid, 2, 3-dimethylsuccinic acid, 2-dimethylglutaric acid, 2-diethyladipic acid, 2, 3-dimethylbenzoic acid, 2, 4-dimethylbenzoic acid, and 2, 5-dimethylbenzoic acid; the proportion of the crude glycol containing the near-azeotropic impurities to the reaction auxiliary agent is (0.5-5) 100 by mass.
18. The separation method according to claim 16, wherein the reaction temperature of the pretreatment reaction in step S1) is 50 to 100 ℃, and the reaction time is 30 to 120 minutes; after the reaction is finished, the reaction product is preferably cooled to 20-40 ℃.
19. The separation method according to claim 16, wherein the operating pressure of the composite membrane is 1 to 3MPa in absolute pressure, and the operating temperature is 20 to 60 ℃.
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