1‐Ethyl‐3‐Methylimidazolium Tetrafluoroborate Ionic Liquid as an Efficient Catalyst for the Methanolysis of PET

ABSTRACT The recycling of polyethylene terephthalate (PET), a widely used polyester plastic, has become an increasingly significant issue. This study aims to develop an efficient and environmentally friendly catalytic system for the degradation of waste PET and realize the resource utilization of polyester. The methanolysis of PET was investigated using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([Emim]BF 4 ) as a catalyst. The effects of temperature, time, [Emim]BF 4 dosage, and methanol dosage on the reaction were systematically examined. The conversion of PET reached 100% with a dimethyl terephthalate (DMT) yield of 74.06% under optimal conditions: 200°C, 2 h, a PET‐to‐[Emim]BF 4 mass ratio of 5:1, and a PET‐to‐methanol mass ratio of 6:1. Kinetic analysis revealed that the reaction followed first‐order kinetics, with an apparent activation energy of 51.16 kJ/mol. A possible mechanism for the [Emim]BF 4 ‐catalyzed methanolysis of PET was proposed. Furthermore, density functional theory (DFT) calculations demonstrated that [Emim]BF 4 could effectively reduce both the reaction energy barriers and the final‐state energy, thereby enhancing the reaction rate and favoring the forward progression of the reaction.