Efficient Catalytic Depolymerization of Waste PET Alcohols with Oyster Shell Matrix Materials

The pollution control of polyethylene terephthalate (PET) and the resource utilization of waste biomass are important issues for sustainable development. This study uses discarded oyster shell biomass after consumption as a precursor to prepare highly active calcium oxide-based catalysts through high-temperature calcination, achieving synergistic governance of “treating waste with waste.” The thermal stability, microscopic morphology and crystalline structure of the oyster shell matrix were systematically characterized through TGA, SEM, and XRD, and the correlation mechanism between the catalytic activity and physical and chemical properties was clarified. Based on single-factor experimental results, the response surface methodology (RSM) was used to optimize the PET glycolysis process in a multivariate way, and a mathematical model was established by combining with the Design–Expert software to quantify the interactions of the parameters of reaction temperature (199℃), time (3.8 h), ethylene glycol dosage (16 mL), and catalyst dosage (0.39%) to achieve a breakthrough improvement of BHET yield of A breakthrough improvement of 83.53% was achieved. Compared with the traditional metal salt and ionic liquid catalysts, this biomass-based system can avoid the consumption of fossil resources and significantly reduce the difficulty of catalyst separation and the risk of environmental pollution. The research constructs a closed-loop recycling model of “aquatic waste-catalytic material-plastic regeneration,” which provides a highly efficient and economical solution for the green degradation of PET, and is of dual practical value in promoting the circular economy of plastics and achieving the goal of carbon neutrality.