Study on DOTP synthesis via alcoholysis of waste PET using oyster shell-derived catalyst

From the perspective of green chemistry, biomass-derived catalysts were prepared using waste oyster shells as raw materials. The oyster shell-derived catalyst obtained at a calcination temperature of 950°C exhibited remarkable catalytic activity. This catalyst was used to catalyze the direct synthesis of diisooctyl terephthalate (DOTP) via alcoholysis of polyethylene terephthalate (PET) with isooctanol (2-EH), and significantly accelerated the formation of the reaction product. Based on the single-factor experiments of catalytic PET alcoholysis for DOTP synthesis, the process conditions for the synthesis of DOTP by PET alcoholysis were optimized using the response surface methodology, and the optimized reaction conditions were as follows: reaction temperature 185°C–190°C, catalyst dosage 6.20% (based on PET mass), n(2-EH):n(PET) 6.26, and reaction time 3.10 h. PET achieved complete depolymerization, and the DOTP yield was as high as 83.84%. This study provides a meaningful reference for the high-quality recycling of waste PET and the development of green catalytic technology for the direct synthesis of DOTP via alcoholysis.