关键词: 废弃聚酯纺织品, 乙二醇醇解, 氮化硼, 再生对苯二甲酸双羟乙酯

Abstract: Polyethylene terephthalate (PET), as one of the most commonly used plastics all over the world, is extensively applied in fields such as the textile industry, engineering plastics and electronic devices. Its widespread application has led to the accumulation of a large amount of PET waste, causing serious environmental pollution and resource waste. Therefore, the treatment of waste PET has become an important issue that should be quickly solved in the environmental field. Ethylene glycol glycolysis of PET is an economical, environmentally friendly and efficient recycling method, and it is also the most widely used technology in industry. Glycolysis involves the cleavage of PET molecular chains facilitated by the solvent action of ethylene glycol (EG), resulting in the formation of bis(2-hydroxyethyl) terephthalate (BHET) monomers. After purification, these monomers can serve as raw materials for the synthesis of recycled polyester, thereby achieving closed-loop resource utilization. Compared with traditional physical recycling, the glycolysis of PET offers advantages such as lower energy consumption, milder reaction conditions, higher monomer recovery rates and reduced environmental impact. It not only enhances resource utilization efficiency but also mitigates environmental pollution, thereby promising a good application prospect. Therefore, further optimizing the glycolysis process flow is an essential path for current sustainable development strategies and holds significant importance in the fields of energy conservation and environmental protection. During the glycolytic depolymerization of waste polyester textiles, catalysts are indispensably needed to accelerate the reaction rate and improve the product yield. Although metal-based catalysts can efficiently depolymerize PET in a relatively short time, the introduction of a large number of metal ions also affects the purity of the product, which increases the difficulty of subsequent product purification. To address the issues of high metal leaching and potential secondary pollution caused by traditional metal-based catalysts during the glycolysis of waste polyester textiles, this study utilizes rod-like boron nitride (c-BN) as a glycolysis catalyst. The glycolysis reaction process is optimized by varying catalyst preparation conditions, reaction time, reaction temperature and catalyst dosage. The results demonstrate that the c-BN calcined at 600 ℃ exhibits the best catalytic efficiency. Under the optimal glycolysis reaction conditions: 10 g of PET, reaction temperature of 200 ℃, reaction time of 3 hours and catalyst dosage of 60 mg, a 100% PET conversion rate and a 69.58% yield of BHET are achieved. By scaling up the PET dosage under the aforementioned glycolysis conditions, a conversion rate approaching or exceeding 100% can be attained for 10 g of PET. Finally, the glycolysis effects of various PET wastes such as fibers, bottle flakes and chips are compared, and it is found that a BHET yield of over 55% can be achieved in all cases, indicating the universal applicability of the catalyst. The research provides new insights into the development of green catalysts for the depolymerization process of waste polyester textiles.

Key words: waste polyester textiles, ethylene glycol glycolysis, boron nitride, regenerated bis 2-hydroxyethyl terephthalate