阅读说明：本技术 一种聚对苯二甲酸乙二醇酯塑料的降解方法 (Degradation method of polyethylene glycol terephthalate plastic ) 是由 孙永福 吴洋 焦星辰 谢毅 于 2021-08-16 设计创作，主要内容包括：本发明提供了一种低温碱性水体系中降解聚对苯二甲酸乙二醇酯(PET)的方法,包括以下步骤：将聚对苯二甲酸乙二醇酯塑料溶解在NaOH的水溶液中,在-10～-5℃条件下进行降解,得到苯二甲酸和乙二醇。实验结果表明在低温碱性体系中可以将聚对苯二甲酸乙二醇酯转化成对苯二甲酸和乙二醇,且在-10～-5℃可以获得最优异的降解率,通过数次降解循环可以实现超过百分之九十的废弃塑料完全降解,相较于常温碱性条件下具有更加优异的降解PET塑料性能。此外,本发明提供的降解方法安全系数高,所需的原料常规且成本低,实验装置易于搭建、回收和循环成本低廉。而且降解过程步骤少、设备技术条件和工艺流程简单、未来可推广到中试放大阶段甚至工业化。(The invention provides a method for degrading polyethylene terephthalate (PET) in a low-temperature alkaline water system, which comprises the following steps: dissolving polyethylene terephthalate plastic in NaOH aqueous solution, and degrading at the temperature of-10 to-5 ℃ to obtain the phthalic acid and the glycol. Experimental results show that the polyethylene glycol terephthalate can be converted into terephthalic acid and ethylene glycol in a low-temperature alkaline system, the most excellent degradation rate can be obtained at-10 to-5 ℃, more than ninety percent of waste plastics can be completely degraded through degradation cycles, and the PET plastic has more excellent PET plastic degradation performance compared with PET plastic degradation performance under the normal-temperature alkaline condition. In addition, the degradation method provided by the invention has the advantages of high safety coefficient, conventional required raw materials, low cost, easy establishment and recovery of experimental devices and low cycle cost. And the steps of the degradation process are few, the technical conditions of equipment and the process flow are simple, and the method can be popularized to a pilot scale-up stage and even industrialization in the future.)

1. A method for degrading polyethylene terephthalate plastic comprises the following steps:

dissolving polyethylene terephthalate plastic in NaOH aqueous solution, and degrading at the temperature of-10 to-5 ℃ to obtain the phthalic acid and the glycol.

2. The degradation process according to claim 1, wherein the ratio of the polyethylene terephthalate plastic, NaOH and water is 10 g: 15 g: 80 mL.

3. The degradation method according to claim 1, wherein the degradation time is 6-10 h.

4. The degradation process according to claim 1, wherein the degradation is carried out under conditions of vigorous stirring.

5. The degradation method according to claim 1, characterized in that it comprises the following steps:

dissolving polyethylene terephthalate plastic in a mixed solution of NaOH and water, stirring strongly at the temperature of-10 to-5 ℃, and then centrifuging in a high-speed centrifuge to obtain supernatant, wherein the precipitate is residual solid plastic.

6. The degradation method according to claim 5, wherein the high-speed centrifuge rotates at 6000-10000 rpm.

Technical Field

The invention relates to the technical field of plastic recovery, in particular to a method for degrading polyethylene terephthalate plastic.

Background

The use of plastics in large quantities has helped the rapid increase in the economics of many economies over the past few decades. This is because plastic materials are lightweight and have strong plasticity, which makes them widely used (e.g., automobiles, packaging, and housings, etc.). However, the corrosion resistance and the strong chemical inertness of plastics make their natural degradation extremely slow, thus presenting serious environmental problems. More seriously, when animals ingest large plastic fragments and micro-plastics, they propagate through the food chain into the human body, causing immeasurable damage to humans and the ecosystem. At present, about 2.6 million tons of plastic wastes generated worldwide every year are disposed of by incineration, which not only destroys the global ecosystem but also causes climate change because carbon dioxide gas equivalent to three times the mass of the burned plastic is discharged during the incineration. Thus, the potential carbon dioxide emissions of plastic waste are 2% of the current global emissions (37.5 million tons of carbon dioxide in 2018). Furthermore, plastics are also associated with the consumption of fossil fuels, about 6% of which are currently used for the production of plastics. This figure is expected to increase further as the decarbonization process in the energy sector increases, and the demand for plastics increases with increasing global wealth and urbanization. For example, in 2018, mckentin states that "recycling and recycling of plastics can bring up to $ 600 billion profit growth for the petrochemical and plastic industries.

Although plastics are inexpensive, they have created serious white contamination problems due to the lack of economic incentive to recover them in the past. China has recently begun to fight plastic waste from abroad and many other countries such as malaysia are expected to quickly imitate it. Also, the european union has a regulatory directive that is subject to legal restrictions, and by 2030, all plastic packaging should be recycled or reused in a cost-effective manner, with the aim of making recycling profitable to the enterprise. These drivers will drive government agencies and the industry to address the problem of plastic recycling. In addition to limiting the use of plastics and encouraging their recycling, the conversion of these plastic wastes into high value-added fuels is also an effective solution. At present, the landfill and incineration method is the most widely adopted treatment means at present, but serious environmental problems and resource waste are caused. Meanwhile, various physical, chemical and biological methods currently used still have the problems of low degradation efficiency and the like, so that a large number of efficient degradation methods which are convenient for large-scale application need to be found.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present invention is to provide a method for degrading polyethylene terephthalate plastic, which realizes efficient degradation of plastic in a low-temperature alkaline water system.

In order to achieve the purpose, the invention provides a method for degrading polyethylene terephthalate plastic, which comprises the following steps:

dissolving polyethylene terephthalate plastic in NaOH aqueous solution, and degrading at the temperature of-10 to-5 ℃ to obtain the phthalic acid and the glycol.

In the invention, the ratio of the polyethylene terephthalate plastic to the NaOH to the water is 10 g: 15 g: 80 mL.

The temperature of the degradation is more preferably-5 ℃.

According to the invention, the degradation time is preferably 6-10 h, and more preferably 8 h.

Preferably, the degradation is carried out under conditions of vigorous stirring.

Preferably, the degradation method comprises the following steps:

dissolving polyethylene terephthalate plastic in a mixed solution of NaOH and water, stirring strongly at the temperature of-10 to-5 ℃, and then centrifuging in a high-speed centrifuge to obtain supernatant, wherein precipitates are residual solid plastic.

According to the invention, the rotating speed of the high-speed centrifuge is 6000-10000 rpm, and more preferably 8000 rpm.

In some embodiments of the invention, the degradation method is specifically:

dissolving 10g of polyethylene terephthalate plastic in a mixed solution of 15g of NaOH and 80mL of distilled water, adding the mixed solution into a reaction vessel, stirring the mixed solution strongly at the temperature of minus 5 ℃ for 8 hours, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, washing the precipitate with water, and centrifuging the precipitate for several times to obtain the residual solid plastic.

The method provided by the invention can be applied to all PET products known to those skilled in the art, such as PET plastic bottles, plastic films, plastic packaging boxes and the like. The terephthalic acid and ethylene glycol produced by the degradation are of significant commercial value after purification. Terephthalic acid is one of the most important bulk feedstocks. Terephthalic acid and ethylene glycol are esterified and condensed to generate a polyester compound, and the polyester not only can be used for synthesizing fiber commodity polyester, but also can be used for producing films and injection molding industries, and is widely applied to the electronic and automobile manufacturing industries. In addition, terephthalic acid is also used for manufacturing herbicides, adhesives and the like. Ethylene glycol is an important petrochemical basic organic raw material, is mainly used for preparing polyester resin, a moisture absorbent, a plasticizer, an antifreezing agent, cosmetics and explosives, is used as a solvent for dyes, printing ink and the like, an analytical reagent and a chromatographic analytical reagent, and can also be used as a hydratable agent and a solvent for pharmacy and leather engineering.

Compared with the prior art, the invention provides a method for degrading polyethylene terephthalate (PET) in a low-temperature alkaline water system, which comprises the following steps: dissolving polyethylene terephthalate plastic in NaOH aqueous solution, and degrading at the temperature of-10 to-5 ℃ to obtain the phthalic acid and the glycol.

Experimental results show that the polyethylene glycol terephthalate can be converted into terephthalic acid and ethylene glycol in a low-temperature alkaline system, the most excellent degradation rate can be obtained at-10 to-5 ℃, more than ninety percent of waste plastics can be completely degraded through several degradation cycles, and the PET plastic has more excellent PET plastic degradation performance compared with the PET plastic degradation performance under the normal-temperature alkaline condition. In addition, the degradation method provided by the invention has high safety coefficient, the required raw materials are conventionally and easily obtained, the cost is low, and an experimental device is easy to build and recover and has low circulating cost. And the steps of the degradation process are few, the technical conditions of equipment and the process flow are simple, the degradation scale is not limited to the laboratory scale, and the method can be popularized to the pilot scale amplification stage and even industrialization in the future. Therefore, the method for degrading the waste PET plastics under the low-temperature alkaline condition is expected to be an efficient and sustainable development means for solving the problem of plastic pollution.

Drawings

FIG. 1 is a nuclear magnetic resonance carbon spectrum of a product obtained by degrading polyethylene terephthalate in a low-temperature alkaline water system in example 1 of the present invention;

FIG. 2 is a graph showing the residual mass of polyethylene terephthalate cyclically degraded three times in a 15g NaOH aqueous system at-5 ℃ in accordance with the present invention;

FIG. 3 is a diagram showing the quality of polyethylene terephthalate degraded in 15g NaOH aqueous system by three cycles under different temperature conditions;

FIG. 4 is a graph showing the quality of polyethylene terephthalate degraded three times under different alkali concentration conditions at-5 ℃ in the present invention;

FIG. 5 is a graph of the remaining mass of a commercial PET plastic bottle degraded three times in a 15g NaOH water system at-5 ℃.

Detailed Description

In order to further illustrate the present invention, the following will describe the degradation method of polyethylene terephthalate plastic provided by the present invention in detail with reference to the examples.

The following NaOH was purchased from national pharmaceutical group chemical reagents, Inc.;

the high-speed centrifuge is purchased from Kangjia scientific instruments, Inc. of Anhui, China, model HC-3518;

the model of the liquid nuclear magnetic resonance spectrometer is Bruker AVANCE AV III 400;

the vacuum drying oven was purchased from Shanghai sperm macro laboratory facilities, Inc., model XMTD-8222.

The polyethylene terephthalate plastic or plastic bottle in the following examples and comparative examples was a plastic material which had been previously pulverized and had a particle size of 5 mm.

Example 1

Dissolving 10g of polyethylene terephthalate plastic in a mixed solution of 15g of NaOH and 80mL of distilled water, adding the mixed solution into a reaction vessel, stirring the mixed solution strongly at the temperature of minus 5 ℃ for 8 hours, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, detecting a liquid-phase product, washing the precipitate with water, and centrifuging the precipitate for several times to obtain the residual solid plastic.

The obtained supernatant is characterized by a liquid nuclear magnetic resonance spectrometer, the obtained nuclear magnetic resonance carbon spectrum diagram is shown in figure 1, and the result shows that the polyethylene terephthalate is degraded into two monomers, namely phthalic acid and ethylene glycol, in a low-temperature alkaline water system.

Application example 1: degrading glycol terephthalate to generate terephthalic acid and glycol under alkaline condition

Dissolving 10g of polyethylene terephthalate plastic in a mixed solution of 15g of NaOH and 80mL of distilled water, adding the mixed solution into a reaction vessel, stirring the mixed solution strongly at the temperature of minus 5 ℃ for 8 hours, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, detecting a liquid-phase product, washing the precipitate with water, and centrifuging the precipitate for several times to obtain the residual solid plastic. The dried powder is put into a vacuum drying oven for drying for a plurality of hours, weighed and calculated to obtain the residual mass and the conversion amount. The experiment was repeated twice with the above remaining plastics and the continuous degradation effect was calculated.

FIG. 2 shows the residual mass of polyethylene terephthalate in the present application example at-5 ℃ in a 15g NaOH aqueous system with three cycles.

Comparative example 1

Dissolving 10g of polyethylene terephthalate plastic in a mixed solution of 15g of NaOH and 80mL of distilled water, adding the mixed solution into a reaction vessel, stirring the mixed solution strongly at the temperature of 10 ℃, 25 ℃ and 40 ℃ for 8h, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, detecting a liquid-phase product, and washing and centrifuging the precipitate for several times by using water to obtain the residual solid plastic. The dried powder is put into a vacuum drying oven for drying for a plurality of hours, weighed and calculated according to the residual mass and the conversion amount. The experiment was repeated twice with the above remaining plastics and the continuous degradation effect was calculated.

The results of comparing the quality results of the degraded plastics obtained in example 1 and comparative example 1 are shown in FIG. 3, and it was found that the degradation effect of ethylene terephthalate at 10 ℃ and at 25 ℃ and 40 ℃ is not as excellent as that at-5 ℃.

Comparative example 2

Respectively dissolving 10g of polyethylene terephthalate plastic in a mixed solution of 5g of NaOH, 10g of NaOH, 15g of NaOH, 20g of NaOH and 80mL of distilled water, adding the mixed solution into a reaction vessel, strongly stirring the mixed solution for 8 hours at the temperature of minus 5 ℃, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, detecting a liquid-phase product, washing the precipitate with water, and centrifuging the precipitate for several times to obtain the residual solid plastic. The dried material is put into a vacuum drying oven for drying for a plurality of hours, weighed and the residual mass and the conversion amount are calculated. And repeating the experiment twice by using the residual plastics, and calculating the continuous degradation effect.

The quality results of the degraded plastics obtained in the comparative example are shown in fig. 4, and it is found that the proper increase of the alkali concentration is beneficial to the degradation of the plastics, and the increase of the alkali concentration has little influence on the degradation effect, but the degradation efficiency is reduced, and unnecessary waste is caused.

As can be seen from fig. 2, 3 and 4, the use of the alkaline and low temperature synergistic conditions of the present invention facilitates the maximum degradation of polyethylene terephthalate to terephthalic acid and ethylene glycol.

Application example 2: low temperature alkaline degradation of commercial PET plastic bottles to terephthalic acid and ethylene glycol

Dissolving a 10g commercial PET plastic bottle in a mixed solution of 15g NaOH and 80mL distilled water, adding the mixed solution into a reaction vessel, stirring the mixed solution strongly for 8h at the temperature of minus 5 ℃, centrifuging the mixed solution in a high-speed centrifuge at the rotating speed of 8000rpm to obtain a supernatant, detecting a liquid-phase product, washing the precipitate with water, and centrifuging the precipitate for several times to obtain the residual solid plastic. The dried powder was placed in a vacuum oven for several hours, weighed, and the remaining mass and the converted amount were calculated. The experiment was repeated twice with the above remaining plastics and the continuous degradation effect was calculated.

Fig. 5 is a graph showing the results of the present invention for continuously degrading commercial PET plastic bottles. As can be seen from fig. 5, effective degradation of commercial PET plastic bottles can be achieved using the alkaline and low temperature synergistic conditions of the present invention.

As can be seen from the above examples and comparative examples, the present invention synergistically degrades PET plastics with high efficiency using low temperature and alkaline conditions. The reagent needed by degradation is easy to obtain, low in cost, recyclable, convenient to separate, simple, practical, efficient, environment-friendly and convenient for large-scale application.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.