Preparation of Purple Mussel Shell-Based Catalysts and Investigation on Their Catalytic Performance in the Alcoholysis of Waste PET for DOTP Synthesis

To achieve high-value utilization of waste resources, this study employed discarded purple mussel shells as raw materials. A catalyst was prepared through one-step calcination at 850°C for the directed synthesis of diisooctyl terephthalate (DOTP) via the alcoholysis of waste polyethylene terephthalate (PET) with 2-ethylhexanol (2-EH). Through response surface methodology (RSM) optimization (reaction temperature 185°C–190°C, catalyst loading 6.10 wt% relative to PET, n(2-EH): n(PET) = 5.26, reaction time 3.18 h), complete PET degradation was achieved with a stable DOTP yield of 83.12%. This study established a closed-loop utilization system for “waste-to-waste resource conversion,” marking the first successful conversion of purple mussel shell waste into a high-efficiency PET alcoholysis catalyst. This breakthrough enabled the direct, one-step, targeted synthesis of the target product DOTP from waste PET alcoholysis, overcoming the technical bottleneck of traditional PET alcoholysis processes that rely on chemical catalysts and struggle to directly synthesize DOTP. It offered a novel strategy for the synergistic development of marine biomass waste utilization and green polymer recycling.