CN112225661A - Impurity removal method and equipment for alcoholysis product after continuous alcoholysis of waste polyester - Google Patents
Impurity removal method and equipment for alcoholysis product after continuous alcoholysis of waste polyester Download PDFInfo
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- CN112225661A CN112225661A CN202011107071.3A CN202011107071A CN112225661A CN 112225661 A CN112225661 A CN 112225661A CN 202011107071 A CN202011107071 A CN 202011107071A CN 112225661 A CN112225661 A CN 112225661A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
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- 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
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
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- 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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Abstract
The invention provides a method and equipment for removing impurities from alcoholysis products after continuous alcoholysis of waste polyester, which comprises the following steps: introducing the alcoholysis product into a liquid-liquid cyclone separator, introducing a primary impurity removal product separated at the bottom into an intermediate storage tank, and introducing a second mixture overflowing from the top into a secondary separator for further separation and impurity removal to obtain a secondary impurity removal product; introducing the secondary impurity-removed product into an intermediate storage tank; the intermediate storage tank is connected with the ester exchange kettle. According to the invention, olefin melt impurities of the post-alcoholysis product of the waste polyester are continuously removed, and the content of the olefin melt impurities in the intermediate product after impurity removal is less than 1%, so that the blockage of subsequent treatment equipment is avoided. The method can be used for continuous sample feeding and sample discharging, the impurity removing equipment is arranged between an alcoholysis reaction kettle and an ester exchange kettle for continuous alcoholysis of waste polyester, the three are connected in series to form a system, and DMF production is carried out by adopting a continuous feeding and continuous discharging mode.
Description
Technical Field
The invention relates to the field of waste polyester recovery, in particular to a method and equipment for removing impurities from alcoholysis products after continuous alcoholysis of waste polyester.
Background
The Chinese name of PET is: polyethylene terephthalate belongs to polyester. PET is largely used as fiber, and engineering plastic resins can be classified into non-engineering plastic grades and engineering plastic grades, and the non-engineering plastic grades are mainly used for bottles, films, sheets, baking-resistant food containers and the like. PET chips are further classified into fiber-grade polyester chips and non-fiber-grade polyester chips. The fiber grade polyester is used for manufacturing polyester staple fibers and polyester filaments, is a raw material for processing fibers and related products for polyester fiber enterprises, and is a variety with the largest yield in chemical fibers.
The existing recovery method of waste polyester mainly comprises physical recovery and chemical recovery. The physical recovery method is simpler and more economical, but the performance of the regenerated product is poor. One important direction of chemical recovery is to alcoholyze the waste polyester with Ethylene Glycol (EG) to produce dihydroxy terephthalate (BHET) or oligomers, then perform transesterification in methanol to produce dimethyl terephthalate (DMT) and ethylene glycol, obtain pure DMT by purification, and use the pure DMT as raw material for polyester production, and use the purified methanol and ethylene glycol in the reaction system to realize the recycling of the waste polyester.
The Chinese patent application No. 201910617806.8 discloses a continuous alcoholysis recovery method for waste polyester, which adopts the continuous feeding and continuous alcoholysis process to perform homogeneous alcoholysis on materials in a molten state, the required alcoholysis time is short, more than two alcoholysis kettles are connected in series to perform continuous alcoholysis, and the product quality of an alcoholysate is stable. Meanwhile, because the use amount of EG in the alcoholysis process is optimized, distillation and concentration are not needed after the alcoholysis step is finished, and alcoholysis products directly enter an ester exchange kettle for ester exchange reaction, so that concentration equipment is saved. However, in the recovery method, as the materials are subjected to homogeneous alcoholysis in a molten state, the alcoholysis materials directly enter transesterification, and olefin melt impurities contained in the alcoholysis materials have the risk of blocking subsequent treatment equipment and need to be separated and removed,
in the prior art of removing impurities from alcoholysis materials, chinese patent No. 201010105259.4 discloses a method for removing impurities from a mixture after alcoholysis of PET, which comprises the steps of performing high temperature and high pressure in a depolymerization stage, decomposing polyolefin-based impurities to form a small molecular substance with a very low molecular weight and capable of being partially gasified at a polymer melt temperature of 230-. However, the method has complex operation process, high cost and low removal efficiency, needs special equipment for removal, and is not suitable for the alcoholysis reaction condition disclosed in the Chinese patent 201910617806.8.
However, the conventional method for separating and removing impurities from alcoholysis products of waste polyesters at present has many disadvantages, particularly:
1. it can only be removed intermittently.
2. The operation process is complicated.
3. The removal efficiency is low.
4. The product quality between the two batches was different.
Disclosure of Invention
In order to achieve the aim, the inventor provides a method and equipment for removing impurities from alcoholysis products after continuous alcoholysis of waste polyester, which can be continuously operated, can be arranged between an alcoholysis kettle and an esterification kettle, does not influence the continuous operations of alcoholysis and esterification, is simple to operate, can efficiently remove olefin melt impurities contained in the alcoholysis products, can efficiently perform subsequent esterification steps, and cannot cause the problem of equipment blockage.
The invention provides a method for removing impurities from alcoholysis products after continuous alcoholysis of waste polyester, which comprises the following steps:
introducing alcoholysis substances in an alcoholysis kettle after continuous alcoholysis of waste polyester into a liquid-liquid cyclone separator, introducing a primary impurity removal product separated from the bottom of the liquid-liquid cyclone separator into an intermediate storage tank, and introducing a second mixture overflowing from the top of the liquid-liquid cyclone separator into a secondary separator for further separation and impurity removal to obtain a secondary impurity removal product; introducing the secondary impurity-removed product into an intermediate storage tank; the intermediate storage tank is connected with the ester exchange kettle.
Alcoholysis products in the alcoholysis kettle after continuous alcoholysis of the waste polyester comprise dihydroxy terephthalate, an alcoholysis agent (ethylene glycol), an olefin melt, an alcoholysis catalyst (potassium carbonate or zinc acetate) and a byproduct (diethylene glycol). The density is as follows from small to large: olefin melt, ethylene glycol, diethylene glycol, dihydroxy terephthalate, potassium carbonate and zinc acetate.
Because the density of the olefin melt impurities is smaller than that of other components, the olefin melt impurities overflow from the top of the liquid-liquid cyclone separator and enter the secondary separator, and part of the ethylene glycol also overflows from the top;
and the rest first impurity removal products are positioned below the olefin melt impurities and enter the intermediate storage tank from the bottom of the liquid-liquid cyclone separator.
Further, the introduction pressure of the alcoholysis product into the liquid-liquid cyclone is greater than 0.1 MPA.
Further, the separation time of the alcoholysis product in the liquid-liquid cyclone separator is 1s, and the separation temperature is 200-210 ℃.
The alcoholysis temperature of the waste polyester is 180-200 ℃, and the separation temperature is slightly higher than the continuous alcoholysis temperature. Although the boiling point of the olefin melt impurities and the ethylene glycol is lower than 200 ℃, the introduction pressure is more than 0.1MPA, and the retention time is 1-2s, so that the olefin melt impurities and the ethylene glycol still exist in a liquid state at the temperature of 200-210 ℃, but the molecular distance is increased, and the olefin melt impurities and the ethylene glycol flow to the top of the liquid-liquid cyclone separator at a higher speed. A small amount of glycol and olefin melt impurities overflow from the top of the liquid-liquid cyclone separator together and enter a secondary separator.
The dihydroxyethyl terephthalate and the diglycol are stable liquid at the temperature and have higher density, and basically enter the intermediate storage tank from the bottom of the liquid-liquid cyclone separator.
Furthermore, in the alcoholysis product, the content of olefin melt impurities is 3-6%.
Further, the content of olefin melt impurities in the intermediate product in the intermediate storage tank is lower than 1%.
Further, the preparation of the alcoholysis product after the continuous alcoholysis of the waste polyester comprises the following steps:
pretreating materials, namely drying and deoxidizing the waste polyester to obtain a waste polyester raw material;
alcoholysis, namely continuously feeding the waste polyester raw material, an alcoholysis agent and an alcoholysis catalyst into a first alcoholysis kettle together in a molten state for carrying out first alcoholysis to obtain a melt A, and continuously feeding the melt A into a second alcoholysis kettle for carrying out second alcoholysis to obtain an alcoholysate;
the alcoholysis agent is ethylene glycol; the alcoholysis catalyst is potassium carbonate or zinc acetate.
Further, the secondary separator is a plate-type phase separator; working temperature: 190 ℃; working pressure: less than 0.1 MPa; separation time: 5-8 min. In the secondary separator, ethylene glycol (boiling point 197.3 ℃) which is liquid under these conditions flows into the intermediate tank, whereas the olefinic melt impurities are gaseous and are separated as impurities.
The invention also provides impurity removing equipment for the alcoholysis product after continuous alcoholysis of the waste polyester, which comprises a liquid-liquid cyclone separator, a secondary separator and an intermediate storage tank, wherein an inlet of the liquid-liquid cyclone separator is connected with an outlet of the alcoholysis kettle, an outlet at the top of the liquid-liquid cyclone separator is connected with an inlet of the secondary separator, an outlet at the bottom of the liquid-liquid cyclone separator is connected with the storage tank, a product outlet of the secondary separator is connected with the intermediate storage tank, the intermediate storage tank is connected with the transesterification kettle, and the secondary separator is also provided with an exhaust port for discharging olefin melt impurities.
Different from the prior art, the technical scheme at least comprises the following beneficial effects: the method continuously removes the olefin melt impurities of the post-alcoholysis product of the waste polyester, has short separation time, high efficiency, low cost and excellent impurity removal effect, and avoids the blockage of subsequent treatment equipment, and the content of the olefin melt impurities in the intermediate product after impurity removal is less than 1%. The method can be used for continuous sample feeding and sample discharging, the impurity removing equipment is arranged between an alcoholysis reaction kettle and an ester exchange kettle for continuous alcoholysis of waste polyester and is connected in series to form a system, DMF (dimethyl formamide) production is carried out by adopting a continuous feeding and continuous discharging mode, olefin melt impurities can be removed in the continuous production process, the production efficiency is high, and the method is suitable for industrial production.
Drawings
FIG. 1 shows the impurity removal equipment for the mixture after alcoholysis of PET as described in example 1.
Description of reference numerals:
1. an alcoholysis kettle is used for carrying out alcoholysis,
2. a liquid-liquid cyclone separator, a cyclone separator,
3. a second-stage separator, a first-stage separator,
4. and an intermediate storage tank.
Detailed Description
To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.
The present embodiment adopts: the Chinese patent application with application number 201910617806.8 discloses a continuous alcoholysis recovery method of waste polyester, which comprises the steps of carrying out continuous alcoholysis and ester exchange on a waste polyester raw material, an alcoholysis agent and an alcoholysis catalyst in a molten state to synthesize an ester exchange product; DMT crystallization and methanol washing are carried out on the ester exchange product, and a recovery liquid is obtained in the processes of DMT crystallization and methanol washing. The method specifically comprises the following steps:
pretreating materials, namely drying and deoxidizing the waste polyester to obtain a waste polyester raw material;
alcoholysis, namely continuously feeding the waste polyester raw material, an alcoholysis agent and an alcoholysis catalyst into a first alcoholysis kettle together in a molten state for carrying out first alcoholysis to obtain a melt A, and continuously feeding the melt A into a second alcoholysis kettle for carrying out second alcoholysis to obtain an alcoholysate;
the alcoholysis catalyst is potassium carbonate or zinc acetate, and the alcoholysis agent is ethylene glycol. The alcoholysis temperature is 180-200 ℃. In the alcoholysis product, the content of olefin melt impurities is 3-6%.
Example 1 impurity removing equipment for alcoholysis products after continuous alcoholysis of waste polyester
Referring to fig. 1, the impurity removing equipment for the alcoholysis product after continuous alcoholysis of waste polyester comprises a liquid-liquid cyclone separator 2, a secondary separator 3 and an intermediate storage tank 4, wherein an inlet of the liquid-liquid cyclone separator 2 is connected with an outlet of an alcoholysis kettle 1, an outlet at the top of the liquid-liquid cyclone separator 2 is connected with an inlet of the secondary separator 3, an outlet at the bottom of the liquid-liquid cyclone separator 2 is connected with the intermediate storage tank 4, a product outlet of the secondary separator 3 is connected with the intermediate storage tank 4, the intermediate storage tank 4 is connected with an ester exchange kettle, and the secondary separator 3 is further provided with an exhaust port for discharging olefin melt impurities.
Example 2 impurity removal of alcoholysis product after continuous alcoholysis of waste polyester by using the impurity removal equipment of example 1
Introducing an alcoholysis product in the alcoholysis kettle into an inlet of a liquid-liquid cyclone separator from an outlet of the alcoholysis kettle through a pressure pump at the pressure of 0.5MPa, overflowing olefin melt impurities with low density and a small amount of ethylene glycol in a mixture entering the liquid-liquid cyclone separator from the top to enter a secondary separator, and introducing primary impurity removal products (BHET and ethylene glycol) with high density into a storage tank from an outlet at the bottom of the liquid-liquid cyclone separator; the separation time of the alcoholysis product in the liquid-liquid cyclone separator is 1s, and the separation temperature is 210 ℃.
And (3) carrying out secondary separation on the second mixture (olefin melt impurities and EG) overflowing into the inlet of the secondary separator, discharging the olefin melt impurities out of the system from the exhaust port of the secondary separator, and feeding a secondary impurity-removed product (EG) into a storage tank. Working temperature of the secondary separator: 190 ℃; working pressure: less than 0.1 MPa; separation time: 5-8 min.
Analyzing the impurity content in the mixture before and after impurity removal equipment by using a liquid chromatograph:
the alcoholysis product of example 2 had an olefin based melt impurity level of 3% and the product in the storage tank had an olefin based melt impurity level of 0.7%.
Example 3 impurity removal of alcoholysate from waste polyester after continuous alcoholysis using the impurity removal equipment of example 1
Introducing an alcoholysis product in the alcoholysis kettle into an inlet of a liquid-liquid cyclone separator from an outlet of the alcoholysis kettle through a pressure pump at the pressure of 1MPa, overflowing olefin melt impurities with small density and a small amount of ethylene glycol in a mixture entering the liquid-liquid cyclone separator from the top to enter a secondary separator, and introducing primary impurity removal products (BHET and ethylene glycol) with large density into a storage tank from an outlet at the bottom of the liquid-liquid cyclone separator; the separation time of the alcoholysis product in the liquid-liquid cyclone separator is 2s, and the separation temperature is 200 ℃.
And (3) carrying out secondary separation on the second mixture (olefin melt impurities and EG) overflowing into the inlet of the secondary separator, discharging the olefin melt impurities out of the system from the exhaust port of the secondary separator, and feeding a secondary impurity-removed product (EG) into a storage tank. Working temperature of the secondary separator: 190 ℃; working pressure: less than 0.1 MPa; separation time: 5-8 min.
Analyzing the impurity content in the mixture before and after impurity removal equipment by using a liquid chromatograph:
the alcoholysis product of example 3 had an olefin based melt impurity content of 5% and the product in the storage tank had an olefin based melt impurity content of 1%.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrases "comprising … …" or "comprising … …" does not exclude the presence of additional elements in a process, method, article, or terminal that comprises the element. Further, herein, "greater than," "less than," "more than," and the like are understood to exclude the present numbers; the terms "above", "below", "within" and the like are to be understood as including the number.
It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.
Claims (9)
1. An impurity removal method for alcoholysis products after continuous alcoholysis of waste polyester is characterized by comprising the following steps: introducing alcoholysis substances in an alcoholysis kettle after continuous alcoholysis of waste polyester into a liquid-liquid cyclone separator, introducing a primary impurity removal product separated from the bottom of the liquid-liquid cyclone separator into an intermediate storage tank, and introducing a second mixture overflowing from the top of the liquid-liquid cyclone separator into a secondary separator for further separation and impurity removal to obtain a secondary impurity removal product; introducing the secondary impurity-removed product into an intermediate storage tank; the intermediate storage tank is connected with the ester exchange kettle.
2. The method of removing impurities according to claim 1, wherein the introducing pressure of the alcoholysis product into the liquid-liquid cyclone is greater than 0.1 MPA.
3. An impurity removal method according to claim 1, wherein the separation time of the alcoholysis product in the liquid-liquid cyclone separator is 1-2s, and the separation temperature is 200-210 ℃.
4. The abatement process of claim 1, wherein the alcoholysis product comprises bis-hydroxy terephthalate, ethylene glycol, and olefin melt impurities.
5. A process according to claim 3, wherein the alcoholysis product contains 3 to 6% of olefinic melt impurities.
6. A process according to claim 1, wherein the intermediate product in the intermediate storage tank contains less than 1% of olefinic melt impurities.
7. The impurity removal method of claim 1, wherein the preparation of the alcoholysis product of the waste polyester after continuous alcoholysis comprises the following steps:
pretreating materials, namely drying and deoxidizing the waste polyester to obtain a waste polyester raw material;
alcoholysis, namely continuously feeding the waste polyester raw material, an alcoholysis agent and an alcoholysis catalyst into a first alcoholysis kettle together in a molten state for carrying out first alcoholysis to obtain a melt A, and continuously feeding the melt A into a second alcoholysis kettle for carrying out second alcoholysis to obtain an alcoholysate;
the alcoholysis agent is ethylene glycol; the alcoholysis catalyst is potassium carbonate or zinc acetate.
8. A process for removing impurities according to claim 1, wherein the secondary separator is a plate-type phase separator; working temperature: 190 ℃; working pressure: less than 0.1 MPa; separation time: 5-8 min.
9. The impurity removing equipment for the alcoholysis product after continuous alcoholysis of the waste polyester is characterized by comprising a liquid-liquid cyclone separator, a secondary separator and an intermediate storage tank, wherein an inlet of the liquid-liquid cyclone separator is connected with an outlet of an alcoholysis kettle, an outlet at the top of the liquid-liquid cyclone separator is connected with an inlet of the secondary separator, an outlet at the bottom of the liquid-liquid cyclone separator is connected with the storage tank, a product outlet of the secondary separator is connected with the intermediate storage tank, the intermediate storage tank is connected with the transesterification kettle, and the secondary separator is further provided with an exhaust port for discharging olefin melt impurities.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1340077A (en) * | 1999-02-10 | 2002-03-13 | 伊斯曼化学公司 | Glycolysis process for recycling of post-consumer PET |
| CN1413178A (en) * | 1999-10-22 | 2003-04-23 | 帝人株式会社 | Method for separating and recovering dimethyl terephthalate and ethylene glycol from polyester waste |
| CN101805445A (en) * | 2010-01-29 | 2010-08-18 | 成强 | Chemical treating method for melt polycondensation high polymer old material regeneration |
| CN107308905A (en) * | 2017-07-28 | 2017-11-03 | 北京服装学院 | Waste and old polyester cotton method of separating component |
| CN108103613A (en) * | 2017-12-21 | 2018-06-01 | 福建荔枝新材料有限公司 | A kind of polyester material recycling and surface Mechanical lithography method |
| CN110845761A (en) * | 2019-11-25 | 2020-02-28 | 浙江海利环保科技股份有限公司 | Method for removing impurities in alcoholysis liquid |
-
2020
- 2020-10-16 CN CN202011107071.3A patent/CN112225661B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1340077A (en) * | 1999-02-10 | 2002-03-13 | 伊斯曼化学公司 | Glycolysis process for recycling of post-consumer PET |
| CN1413178A (en) * | 1999-10-22 | 2003-04-23 | 帝人株式会社 | Method for separating and recovering dimethyl terephthalate and ethylene glycol from polyester waste |
| CN101805445A (en) * | 2010-01-29 | 2010-08-18 | 成强 | Chemical treating method for melt polycondensation high polymer old material regeneration |
| CN107308905A (en) * | 2017-07-28 | 2017-11-03 | 北京服装学院 | Waste and old polyester cotton method of separating component |
| CN108103613A (en) * | 2017-12-21 | 2018-06-01 | 福建荔枝新材料有限公司 | A kind of polyester material recycling and surface Mechanical lithography method |
| CN110845761A (en) * | 2019-11-25 | 2020-02-28 | 浙江海利环保科技股份有限公司 | Method for removing impurities in alcoholysis liquid |
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