CN112851502B - Method for catalyzing waste PET polyester to carry out methanol alcoholysis by using choline and terephthalic acid non-metallic ionic liquid - Google Patents
Method for catalyzing waste PET polyester to carry out methanol alcoholysis by using choline and terephthalic acid non-metallic ionic liquid Download PDFInfo
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- CN112851502B CN112851502B CN202110145245.3A CN202110145245A CN112851502B CN 112851502 B CN112851502 B CN 112851502B CN 202110145245 A CN202110145245 A CN 202110145245A CN 112851502 B CN112851502 B CN 112851502B
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- C07—ORGANIC CHEMISTRY
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- C07C67/00—Preparation of carboxylic acid esters
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
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- Y02W30/62—Plastics recycling; Rubber recycling
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Abstract
The invention relates to a method for catalyzing alcoholysis of methanol by using choline and terephthalic acid non-metallic ionic liquid to waste PET (polyethylene terephthalate) polyester, which is characterized in that the waste PET polyester (comprising PET bottles, PET packaging sheets, PET fibers and PET textiles) is used as a raw material, methanol is used as a solvent, choline and terephthalic acid non-metallic ionic liquid is used as a catalyst, the dosage of the catalyst is 0.5-10% of the mass of PET, the reaction temperature is 130-200 ℃, the reaction time is 30-360 min, and the mass ratio of methanol to PET is 1:1 to 10:1 under the condition of catalyzing alcoholysis of PET. The method has the characteristics that the catalyst does not contain metal, is green and environment-friendly, can reduce the demetallization unit operation of subsequent products, and improves the quality of degradation products, and has low requirements on raw materials, and alcoholysis products are easy to separate and purify.
Description
Technical Field
The invention relates to a method for recovering waste polyethylene glycol terephthalate by alcoholysis of methanol by using choline and terephthalic acid non-metallic ionic liquid as catalysts, belonging to the technical field of polymer degradation and green catalysis.
Background
Polyethylene terephthalate (Poly (ethylene terephthalate), PET for short) obtained by polycondensation of terephthalic acid and ethylene glycol is the earliest developed polyester product with the largest yield and the widest application. Because the PET has the characteristics of high strength, chemical corrosion resistance, good thermal stability, good melt fluidity and the like, the existing numerous plastic products, including textiles, electronic products, beverage containers, food packages, packages of personal care products, fibers and the like, all use the PET as a raw material, about 5600 ten thousand tons of PET is produced only 2013 worldwide, and the PET is still rising year by year. Due to the characteristics of light weight, large volume and difficult natural decomposition, the direct discharge of a large amount of waste PET not only causes serious environmental pollution, but also brings huge resource waste. Meanwhile, the raw material of PET is a non-renewable petroleum resource, and in recent years, the effective production amount of petroleum is rapidly reduced, and the supply and demand are increasingly tense. Therefore, the recycling of the waste PET not only can reduce the pollution to the environment, but also can prolong the utilization period of resources, save production raw materials and have great social and economic benefits.
The recovery method of waste PET is classified into a physical recovery method and a chemical recovery method according to different principles. The physical recycling method is a method of preparing recycled materials by pulverizing, separating, melting, purifying, etc. waste PET without destroying the chemical structure of the waste PET. The physical recovery method has the biggest characteristics of low cost and simple technology, and is mainly used for certain regeneration industries with low requirements on product quality. However, the physical and mechanical properties and various physical and chemical properties of the products regenerated by the physical recovery method are reduced, the polyester products recycled by the one-time physical recovery method are not suitable to be reused due to the reasons of low intrinsic viscosity and the like, the recycling of the waste PET by the method cannot reach the recycling of the essential significance, and the recycling can be realized only by the chemical recovery method. The chemical recovery method effectively utilizes the destructiveness of micromolecule degradation agent to macromolecular chain structure, firstly degrades the waste polyester into monomer or intermediate, and further carries out secondary polymerization on the monomer or intermediate obtained by degradation through separating and purifying each component and impurities of degradation products to realize regeneration, thereby achieving the purpose of changing waste into valuable. The method is not limited by the source of PET raw materials, PET composite materials or low-quality colored PET waste materials can be utilized, the method can be recycled for many times, and the regenerated product has high quality and wide application. Therefore, the chemical recovery method has a very significant advantage for the recycling of the waste PET compared with the physical recovery method.
However, in the chemical recovery method, when no catalyst is used, the degradation of PET is very slow only by the action of a solvent. Therefore, chemical degradation of PET often requires the introduction of metal-containing catalysts such as manganese acetate, zinc acetate, lead acetate, alkali or alkaline earth metal oxides, and the like. The metal catalyst for PET degradation has residues with different degrees in degradation products, and can severely restrict the further utilization of subsequent alcoholysis products, for example, the residues of the metal catalyst can influence the polymerization degree and color of polyester when the alcoholysis products are polymerized to prepare regenerated polyester, thereby greatly reducing the quality of the products, bringing threats to the health of human beings and the environment, and ensuring that the products after polymerization can not meet the requirements. Such as PET, is degraded, zinc acetate or mixtures thereof are commonly used as a catalyst. Although zinc is an essential trace element, zinc belongs to heavy metals, and is enriched in the environment and human body, high-level exposure can cause anemia, and excessive zinc can cause gastrointestinal problems and also can affect the central nervous system. China also sets corresponding limit on zinc in the environment, the limit on zinc in drinking water is 1ppm, and the contents of zinc in drinking water are strictly limited to 5ppm and 1ppm in the United states and Japan, respectively. Therefore, the catalytic degradation of PET by adopting the non-metal catalyst has important significance.
Currently, the most representative chemical recovery methods for PET are the hydrolysis method, the methanol alcoholysis method and the ethylene glycol alcoholysis method. The water degradation method is strict in requirements, needs to be carried out in a high-temperature and high-pressure environment, has high requirements on production equipment, generates a large number of byproducts, and is difficult to realize industrial production. The glycol alcoholysis method has the advantages of low efficiency, poor product selectivity, low yield, difficult product decoloration and purification and great limitation on the recovery of colored and impurity-containing waste PET raw materials. Compared with ethylene glycol, methanol has stronger nucleophilicity, high activity and short time required for complete degradation, and the Dimethyl terephthalate (DMT) product obtained by the methanol alcoholysis method has lower boiling point than the Bis (2-hydroxyethyi) terephthalate (BHET) product obtained by the ethylene glycol alcoholysis method, good high-temperature stability and is easy to obtain a high-purity product by distillation and purification. A small amount of PET can be dissolved in the choline and terephthalic acid non-metal ionic liquid, the alcoholysis activity of PET methanol is further improved through a dissolution-degradation coupling reaction, the reaction can be realized at a lower temperature and under a pressure, the reaction time is short, and the generation of colored byproducts in the degradation process is effectively avoided. Even if the adopted raw materials are colored waste PET, the alcoholysis of the PET by methanol and the subsequent decoloration and purification of the product cannot be influenced. The choline and terephthalic acid non-metal ionic liquid does not contain metal, can reduce metal removal units in subsequent treatment, reduces purification cost, avoids use limitation on obtained degradation products, has the characteristics of biodegradability, low toxicity, small corrosion to equipment and the like, and is convenient for large-scale popularization and use in industrialization. Therefore, the method for catalyzing the alcoholysis of the waste PET polyester by the choline and terephthalic acid non-metal ionic liquid through methanol can avoid the influence of the use of metal and the residual metal on depolymerized products, simplify purification steps, and has low requirements on PET raw material sources and wide applicability on raw materials. In addition, the catalyst can dissolve a small amount of PET, the reaction activity is improved through dissolution-degradation coupling reaction, so that the alcoholysis temperature is reduced, the alcoholysis time is shortened, the PET conversion rate and the DMT monomer yield are increased, products after reaction are easy to separate, and the catalyst has a wide application prospect.
The invention has the following advantages:
(1) The choline and terephthalic acid non-metal ionic liquid is used for methanolysis of the waste PET polyester, so that the influence of the use of a metal catalyst and metal residues on a depolymerized product is avoided, metal removal units in subsequent product treatment are reduced, the purification steps are simplified, and the separation cost is reduced;
(2) The choline and terephthalic acid non-metal ionic liquid is used for methanolysis of waste PET polyester, and the activity of the catalyst is improved and the dosage of the catalyst is reduced by virtue of the dissolution-degradation coupling effect of the catalyst on the PET, so that the production cost is reduced;
(3) According to the invention, the waste PET polyester is recovered by using methanol with strong nucleophilicity, the alcoholysis solvent has high activity, the reaction condition is mild, the product has good selectivity and high yield;
(4) The invention adopts methanol alcoholysis method to recover waste PET polyester, and the obtained DMT product is easy to separate and purify, thus having low requirement on the source of raw materials and using waste PET with high color and impurity content as raw materials;
(5) The waste PET polyester is subjected to methanol alcoholysis for recycling, so that the pollution of the waste PET to the environment and the ecology can be reduced, the utilization period of resources can be prolonged, the production raw materials are saved, and the method has great social and economic benefits.
Disclosure of Invention
The invention aims to provide a method for catalyzing waste PET polyester to carry out methanolysis by taking choline and terephthalic acid non-metal ionic liquid as a catalyst, and aims to solve the problems of poor product selectivity, low yield, difficulty in decoloring and purifying and metal residue in a depolymerized product caused by a metal degradation catalyst in the existing PET chemical recovery process.
In order to realize the aim, the invention provides a method for efficiently and rapidly catalyzing PET polyester to carry out alcoholysis on methanol under mild conditions by taking choline and terephthalic acid non-metallic ionic liquid as catalysts so as to realize efficient chemical recovery of PET. The specific implementation steps are as follows: and sequentially putting the waste PET bottles, the PET packaging sheets, the PET fibers or PET textiles, the catalyst and the methanol into a degradation kettle according to corresponding use amounts, reacting for a certain time at a certain temperature under the stirring condition, analyzing the amount of the DMT product and the residual PET, and calculating to obtain the yield of the DMT and the conversion rate of the PET.
The reaction equation of the invention is as follows:
the method for catalyzing waste PET polyester to carry out methanolysis by using choline and terephthalic acid non-metal ionic liquid is characterized in that waste PET polyester is used as a raw material, choline and terephthalic acid non-metal ionic liquid is used as a catalyst, and methanol is used as a solvent to carry out alcoholysis on PET.
The method for catalyzing waste PET polyester to carry out methanolysis by choline and terephthalic acid non-metallic ionic liquid is characterized in that the degraded PET polyester raw materials comprise PET bottles, PET packaging sheets, PET fibers and PET textiles, and the mass ratio of the used solvent to PET is 1:1 to 10:1, the adding amount of the catalyst is 0.5 to 10 percent of the mass of the PET, the reaction temperature is between 130 and 200 ℃, and the reaction time is between 30 and 360min. After the reaction is finished, the conversion rate of the PET polyester and the yield of DMT product are calculated according to the formulas (1) and (2):
Detailed Description
The present invention will be described below with reference to specific examples, but the application of the present invention is not limited to the scope of the examples, and variations and implementations are included in the technical scope of the present invention without departing from the spirit of the invention.
1. Influence of different non-metal ionic liquid catalysts on methanol alcoholysis of waste PET polyester
Examples 1 to 14
Putting the waste PET bottle chips, 5 mass percent of choline glycine, choline proline, choline formic acid, choline acetic acid, choline propionic acid, choline butyric acid, 1-ethyl-3-methylimidazole terephthalate, 1-propyl-3-methylimidazole terephthalate, 1-butyl-2, 3-dimethylimidazole terephthalate, 1-vinyl-3-butylimidazole terephthalate, 1-butyl-3-methylimidazole isophthalate, 1-butyl-3-methylimidazole phthalate, 1-butyl-3-methylimidazole benzoate and methanol in a mass ratio of 3 to the waste PET bottle chips into a degradation kettle, heating to 170 ℃, and reacting for 60min. After the reaction is finished, the mass of the DMT product and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of different non-metal ionic liquid catalysts on the alcoholysis of the waste PET polyester by methanol is detailed in the serial numbers 1-14 in the table 1.
TABLE 1 examples 1-14 Effect of different non-metallic ionic liquid catalysts on methanolysis of waste PET polyesters
2. Influence of catalyst dosage on methanol alcoholysis of waste PET (polyethylene terephthalate) polyester catalyzed by non-metallic ionic liquid
Examples 15 to 19
Putting the waste PET bottle chips, 0.5%, 1%, 3%, 7% and 10% of choline formic acid and methanol with the mass ratio of 3. After the reaction is finished, the mass of the DMT product and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of the catalyst dosage on the alcoholysis of the waste PET polyester by the nonmetallic ionic liquid with methanol is shown in the serial numbers 15-19 in the table 2.
TABLE 2 examples 15-19 Effect of catalyst levels on non-metallic Ionic liquids catalyzing alcoholysis of methanol from waste PET polyesters
| Examples | Amount of catalyst/% | DMT yield/% | PET conversion/%) |
| 15 | 0.5 | 25.4 | 42.7 |
| 16 | 1 | 47.3 | 53.2 |
| 17 | 3 | 68.9 | 75.1 |
| 18 | 7 | 93.9 | 100 |
| 19 | 10 | 92.1 | 100 |
3. Influence of methanol dosage on alcoholysis of waste PET (polyethylene terephthalate) polyester methanol catalyzed by non-metallic ionic liquid
Examples 20 to 23
Putting the waste PET bottle chips, 5% by mass of choline formic acid and methanol, the mass ratio of which is 1. After the reaction is finished, the mass of the product DMT and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of the methanol dosage on the alcoholysis of the waste PET polyester catalyzed by the nonmetallic ionic liquid by methanol is detailed in the serial numbers 20-23 in the table 3.
TABLE 3 examples 20-23 Effect of methanol dosage on non-metallic Ionic liquid catalyzed alcoholysis of waste PET polyester with methanol
4. Influence of reaction temperature on alcoholysis of methanol by catalyzing waste PET (polyethylene terephthalate) polyester by using non-metallic ionic liquid
Examples 24 to 28
Putting the waste PET bottle chips, 5% by mass of choline formic acid and methanol with the mass ratio of 3. After the reaction is finished, the mass of the product DMT and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of the reaction temperature on the alcoholysis of the methanol by catalyzing the waste PET polyester by the non-metal ionic liquid is shown in the serial number 24-28 in the table 4.
TABLE 4 examples 24-28 Effect of reaction temperature on non-metallic Ionic liquid catalyzed alcoholysis of methanol from waste PET polyester
| Examples | Reaction temperature/. Degree.C | DMT yield/%) | PET conversion/% |
| 24 | 130 | 10.3 | 12.0 |
| 25 | 150 | 23.4 | 33.1 |
| 26 | 160 | 86.9 | 91.1 |
| 27 | 180 | 95.3 | 100 |
| 28 | 200 | 94.2 | 100 |
5. Influence of reaction time on methanol alcoholysis of waste PET (polyethylene terephthalate) polyester catalyzed by non-metallic ionic liquid
Examples 29 to 34
And (2) putting the waste PET bottle chips, 5% of choline formic acid by mass and methanol with the mass ratio of 3. After the reaction is finished, the mass of the DMT product and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of the reaction time on the alcoholysis of the methanol by catalyzing the waste PET polyester by the non-metal ionic liquid is shown in the serial number 29-34 in the table 5.
TABLE 5 examples 29-34 Effect of reaction time on non-metallic Ionic liquid catalyzed methanolysis of waste PET polyesters
6. Influence of PET source on methanol alcoholysis of waste PET polyester catalyzed by non-metallic ionic liquid
Examples 35 to 37
Putting the waste PET packaging sheet, the PET fiber, the PET textile, 5% by mass of choline formic acid and 3% by mass of methanol into a degradation kettle, heating to 170 ℃, and reacting for 60min. After the reaction is finished, the mass of the DMT product and the residual PET is analyzed, and the yield of DMT and the conversion rate of PET are calculated. The influence of the PET source on the alcoholysis of the waste PET polyester catalyzed by the non-metallic ionic liquid by methanol is detailed in the serial numbers 35-37 in the table 6.
TABLE 6 examples 35-37 Effect of PET Source on non-Metal Ionic liquid catalyzed methanolysis of waste PET polyesters
| Examples | Reaction raw material | DMT yield/%) | PET conversion/%) |
| 35 | PET packaging sheet | 89.3 | 100 |
| 36 | PET fiber | 93.4 | 100 |
| 37 | PET textile | 91.6 | 100 |
Finally, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (1)
1. A method for catalyzing waste PET polyester to carry out alcoholysis with methanol by using a non-metal ionic liquid is characterized in that waste PET bottles, PET fibers or PET textiles are used as raw materials, choline glycine, choline formic acid and choline acetic acid are used as catalysts, methanol is used as a solvent, and the waste PET polyester is catalyzed to carry out alcoholysis under certain reaction conditions; when the non-metal ion liquid methanol alcoholysis PET is carried out, the using amount of the non-metal ion liquid catalyst is 5-10% of the mass of the PET, the alcoholysis temperature is 170-200 ℃, the alcoholysis time is 60-360 min, and the mass ratio of the methanol to the PET is 3:1 to 10:1.
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| CN113897628B (en) * | 2021-08-27 | 2023-04-18 | 中国科学院理化技术研究所 | Method for electrolyzing and depolymerizing PET (polyethylene terephthalate) by using electrocatalysis |
| CN114456073B (en) * | 2022-03-01 | 2023-02-10 | 北京化工大学 | Method for catalyzing depolymerization of polyethylene glycol terephthalate by cyanamide compound |
| IT202200005180A1 (en) * | 2022-03-16 | 2023-09-16 | Formula Centro Di Ricerca E Sviluppo Deep Tech S R L | PROCEDURE FOR THE DEPOLYMERIZATION OF PET |
| CN114736129B (en) * | 2022-04-06 | 2023-03-31 | 中国科学院成都有机化学有限公司 | Dicarboxylic acid-based eutectic solvent and preparation method and application thereof |
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| CN102020565A (en) * | 2010-11-24 | 2011-04-20 | 哈尔滨师范大学 | Method for catalyzing and degrading polyethylene glycol terephthalate material |
| CN105315164A (en) * | 2014-08-01 | 2016-02-10 | 中国科学院大连化学物理研究所 | Environment-friendly choline ionic liquid and preparation method therefor |
| CN111217700A (en) * | 2020-02-19 | 2020-06-02 | 中国科学院过程工程研究所 | Method for catalyzing alcoholysis of polyethylene terephthalate by using non-metal choline ionic liquid |
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