Alcoholysis Of Polyethylene Terephthalate For Dioctyl Terephthalate Using Deep Eutectic Solvents As Efficient Catalysts

Polyethylene terephthalate?PET?is widely used in many fields for its excellent properties,but as the economy continues to develop,huge PET waste emissions have caused serious environmental problems and recycling of used PET must be taken seriously.Dioctyl terephthalate?DOTP?can be prepared by alcoholysis of PET,and DOTP has also been used as a substitute for dioctyl phthalate?DOP?because of its excellent properties and safe non-toxic properties,and it has been produced and used in many developed countries.The traditional method of preparing DOTP is costly and complicated.Therefore,it is necessary to find an efficient and environmentally friendly way to prepare DOTP.In this study,2-Ethyl-1-hexanol?2-EH?was used as solvent,a series of deep eutectic solvents?DESs?were synthesized as catalysts and PET was used as raw material to prepare DOTP.After screening,the best DES catalyst was prepared by using choline chloride?Ch Cl?and zinc acetate?Zn?Ac?₂?as the hydrogen bond donor and acceptor at the same molar ratio,and this method has the advantages of simple synthesis,low cost,low toxicity and high catalytic activity.Under the optimal conditions:at 180°C,60 min,PET:2-EH 1:5 molar ratio and Ch Cl/Zn?Ac?₂?1:1?5 wt%PET,the degradation rate of PET reaches 100%,and the DOTP yield is 84.7%.The characterization of catalysts,products and by-products was by FT-IR,¹H NMR,TGA,SEM and so on.Through the calculation of density functional theory?DFT?and molecular simulation,the possible mechanism is proposed.The results show that the synergistic catalysis play a key role in PET degradation.The reaction kinetics was also studied,and the PET alcoholysis is a first-order reaction with an activation energy of 95.05 k J/mol.In this study,Ch Cl/Zn?Ac?₂?1:1?was synthesized and used as an efficient and green catalyst for PET degradation under mild conditions,and high-value product DOTP was obtained.This work shows that DES catalysts have very broad development and application prospects,at the same time,it is also hoped that this study can provide some reference for the degradation of other waste polymers.