Efficient glycolysis of PET waste with Zn-mediated ionic liquid catalyst: Uncovering the mechanism of dimolecular activation and kinetic acceleration

Efficient recycling of polyethylene terephthalate (PET) is critical for alleviating environmental burdens and promoting closed-loop plastic utilization. Herein, a promising metal-based ionic liquid catalyst, [N₁₁₁₁][Zn(OAc)₃], has been synthesized from tetramethylammonium hydroxide and zinc acetate, and its catalytic performance in PET glycolysis was systematically evaluated. Results show that the [N₁₁₁₁][Zn(OAc)₃] can achieve high PET conversion rate and BHET yield under relatively mild conditions. Under optimized conditions (170 °C, 50 min, 0.2 g catalyst, and 20 g ethylene glycol), the system achieved a PET conversion rate of 90.1% and a BHET yield of 77.2%. Kinetic analysis suggests that the reaction follows a shrinking-core model with an apparent activation energy of 144.7 kJ mol⁻¹. Theoretical calculation results demonstrated that the high efficiency of the Zn-based ionic liquid is attributed to the synergistical activation of both PET and EG. Additionally, the rapid desorption of BHET for Zn-based ionic liquid can accelerate the reaction kinetic.