FeCl3-Doped Cobalt Ferrite as an Efficient Magnetic Catalyst for PET Glycolysis Depolymerization

Abstract

A comparative study of cobalt ferrite (CoFe₂O₄) catalysts synthesized via three different methods is presented, aiming to evaluate their catalytic activities in poly(ethylene terephthalate) (PET) chemical depolymerization by glycolysis. The synthesized catalysts have been characterized by X-ray photoelectron spectroscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and energy dispersive spectroscopy. The conversion of PET into bis(2-hydroxyethyl)terephthalate (BHET) monomer was examined using these cobalt ferrites. The BHET in the reaction mixture was analyzed by FTIR, HPLC, DSC, and TGA and results show the catalyst synthesized by coprecipitation demonstrates the highest BHET yield (95.4%) at a temperature of 200 °C and a pressure of 0.7 bar in 1 h with only 1.0 wt% loading. Hydrothermal synthesized CoFe₂O₄ and solvent-free synthesized CoFe₂O₄ both showed lower BHET yields. The catalytic performance of the coprecipitated CoFe₂O₄ catalyst was influenced by the presence of unintentionally trapped FeCl₃ within the catalyst, which resulted in its enhanced activity. The CoFe₂O₄ catalyst from coprecipitation exhibited acceptable magnetic recoverability and reusability for four consecutive cycles, further highlighting its usefulness and sustainability.

Graphical Abstract