Dimethyl terephthalate

The commercial PET polyester slices (processing grade: fiber grade, non-extinction, intrinsic viscosity 0.676 dL/g) were purchased from Sinopec Yizheng Chemical Fiber Co., Ltd. (Yizheng, China). The SiO₂ nanoparticles (amorphous hydrophilicity, particle size is about 100~200 nm) were purchased from Zhejiang Yuda Chemical Co., Ltd. Sulfoxide chloride, benzene, tetrachloroethane, phenol, antimony trioxide, toluene, dimethyl terephthalate (DMT), zinc acetate, acetone, triphenyl phosphite, o-phenanthroline (Phen), and N,N-dimethylformamide (DMF) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Beijing, China). Tetraethylene glycol (TEG) was obtained from Shanghai Macklin Biochemical Technology Co., Ltd. (Shanghai, China). All the above mentioned reagents are of analytical grade (AR), and were used as received without further purification. Terbium chloride (99.99%) was purchased from Shandong Desheng New Materials Co., Ltd. (Jining, China).

Dimethyl terephthalate (DMT), 1,4-butanediol (BDO), catalysts tetrabutyl titanate (TBT) and magnesium acetate (MgAc₂) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). CHDM was purchased from Aladdin Reagent Co. Ltd. (Shanghai, China); it was the mixture of 69% trans and 31% cis, and PTMG with an average molar weight of 1000 g mol⁻¹ was supplied by BASF (Shanghai, China). The antioxidants (Irganox 1010 and Irgafos 168) were supplied by Ciba (Basel, Switzerland). All of these chemical materials were dried under vacuum at 80 °C for 24 h to a constant mass before use.