Synthesis of bis(2-ethylhexyl) terephthalate from waste poly(ethylene terephthalate) catalyzed by tin catalysts

The production scale and usage of plastics have generated significant amounts of waste especially in regards of PET which is one of the widely produced polymer worldwide, whose accumulation in the environment has become an issue despite attempts to increase its recycling rate. Herein, we applied a new group of catalysts based on organotin compounds for the depolymerization of PET waste. The obtained results showed the formation of dioctyl terephthalate (DOTP), which is a commonly produced plasticizer. For this purpose, a number of organotin catalysts, including tin (II) oxalate, tin (II) bis(2-ethylhexanoate), monobutyltin tris(2-ethylhexanoate), dibutyltin oxide, and dioctyltin oxide (V) were tested. Additionally, common transesterification catalysts, such as zinc acetate and potassium hydroxide, were applied and proved less effective than the tested organotin compounds. Our results showed that among tested compounds monobutyltin tris(2-ethylhexanoate) was the most effective catalyst. Taking into account its good properties an application sample of plasticizer was synthesized on a large scale using monobutyltin tris(2-ethylhexanoate). Furthermore, the physio-chemical and plasticizing properties were determined for two types of plasticizer samples (purified and unpurified).