Catalyst of a Mytilus galloprovincialis shell substrate: optimization of alcoholysis conditions for the catalytic depolymerization of waste polyester films.

Catalysts fabricated from waste Mytilus galloprovincialis shells feature high resource utilization, environmental friendliness and low cost. In this work, a powdered Mytilus galloprovincialis shell substrate was used as a catalyst for the glycolysis of a de-aluminized PET film to synthesize bis(2-hydroxyethyl) terephthalate (BHET), and favorable experimental results were obtained. Taking the BHET yield as the response value, a Box-Behnken response surface design was carried out on the basis of single-factor experiments to explore the influencing factors of the BHET yield as well as their interaction effects, and a quadratic regression model was established. Analysis of variance (ANOVA) verified that the established model was highly significant. The optimized glycolysis conditions for PET film depolymerization with ethylene glycol were determined as follows: a catalyst loading of 0.49%, reaction temperature of 198 °C, reaction duration of 1.5 h, and ethylene glycol dosage of 15.56 g; under these conditions, the actual BHET yield reached 83.95%. The Mytilus galloprovincialis shell-based catalytic system delivered a high BHET yield for PET film glycolysis. This strategy realizes the high-value concurrent utilization of waste biomass and waste PET resources, providing a green, low-cost chemical recycling pathway for PET with promising industrial application potential.