K2CO3/KOH synergistic alcoholysis of waste polyester textiles and their preparation of recycled DMT
Polyethylene terephthalate(PET)is commonly used in textiles and apparel,automotive interior and other fields due to its excellent properties such as high strength and chemical stability.With the rapid development and expansion of polyester textiles,the accumulation of waste polyester textiles is also increasing year by year.However,the waste polyester textiles are difficult to be degraded naturally,posing a significant environmental threat.Recycling waste PET textiles is therefore crucial.Previous studies have identified two main methods for recycling waste polyester textiles:the physical method and the chemical method.The physical method involves regenerating the textiles through simple melting and granulation,but this method does not produce recycled products with good quality and stable performance.The chemical method involves using a depolymerising agent to break down waste polyester textiles into small molecules.These molecules are then polymerized to create a recycled polyester product.This process is a crucial method for producing high-quality recycled polyester products.Currently,chemical methods primarily consist of hydrolysis,alcoholysis,and enzymatic hydrolysis.Among them,the glycol alcoholysis-methanol ester exchange method has gained popularity due to its mild reaction conditions.However,it suffers from low product yield and the formation of oligomers during the alcoholysis stage.Additionally,the ester exchange stage requires a complex product purification process.Current research is focused on addressing these issues.To address the issues of low product yields and increased oligomers in the glycolysis-methanol ester exchange process,this study suggested the use of K2CO3/KOH synergistic alcoholysis on discarded polyester textiles.Firstly,the inexpensive potassium carbonate was used as the primary catalyst in the alcoholysis stage.KOH was also introduced to co-polymerize the waste polyester textiles.Secondly,the response surface method was employed to optimize the process parameters in the alcoholysis stage,resulting in the identification of the optimal process parameters.Finally,the purification method was optimized in the ester-exchange stage based on the phase transition property of DMT,leading to the preparation of high-purity regenerated DMT.This paper introduced the use of KOH in the alcoholysis stage to co-polymerize waste polyester textiles.This reduced the oligomer content in the alcoholysis products and increased the BHET yield.In the ester exchange stage,a simple decompression sublimation method was used to purify the regenerated DMT.The purification process was also optimized.The experimental results indicate that the K2CO3/KOH synergistic alcoholysis of waste polyester textiles primarily produced BHET.The regenerated BHET yield demonstrated an increasing trend with the addition of KOH,peaking at 70.2％when the KOH addition reached 2％.The process parameters of the alcoholysis stage were optimized by using response surface methodology.The optimal conditions were determined to be a reaction temperature of 210℃,a reaction time of 120 minutes,K2CO3 content of 2.0％,and KOH content of 2.4％.These conditions resulted in a regenerated BHET yield of 73.1％.The regenerated DMT achieved a purity of over 99％after undergoing purification through decompression sublimation during the ester exchange stage.Efficient purification of the regenerated DMT was achieved.To enhance the reaction efficiency and product yield of waste polyester textiles,a cost-effective and viable method is the synergistic depolymerization of waste polyester textiles with K2CO3/KOH to prepare regenerated DMT.The research provides valuable reference for the environmentally friendly recycling of waste polyester textiles and lays a foundation for producing high-quality regenerated polyester downstream.
万方数据
