Rapid Glycolysis of Waste Polyethylene Terephthalate Fibers via a Stepwise Feeding Process
Dandan Lei, Xiaoli Sun, Shasha Hu, Huibin Cheng, Qinghua Chen, Qingrong Qian, Qiao Xiao, Changlin Cao, Lireng Xiao, Baoquan Huang
Abstract
Recycling waste polyethylene terephthalate (PET) fibers is critical for both environmental and resource protection. However, the PET fiber possesses good chemical stability and high crystallinity, resulting in the conversion of PET. Herein, we developed a strategy of stepwise feeding process to recycle PET fibers and recover the potential monomer by adding it to the glycolysis agent diethylene glycol after it had been warmed up to reaction temperature. The results show a significant increase in the PET fiber conversion (92.5%) and yield of water-soluble products (70.4%) in 90 min as compared to a one-step feeding process of 28 and 14.4%, respectively. These water-soluble products are monomers and dimers which are confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectroscopy, and high-performance liquid chromatography. It is also obviously found that the conversion of PET and yields of fibers are lower than those of bottle flakes and particles. In addition, a ’column shrinkage model’ is proposed to describe the glycolysis process of the fibers. The apparent reaction activation energy of fibers was derived as 27.19 kJ/mol, which is somewhat higher than those of PET bottle flakes and particles.