Depolymerization of Poly(1,2-propylene carbonate) via Ring Closing Depolymerization and Methanolysis

Abstract

The conversion of end-of-life plastics to useful chemicals can contribute to a resource-conserving and environmental-benign society. In this regard, we studied the depolymerization via methanolysis of poly(1,2-propylene carbonate) using straightforward metal salts as precatalysts. In more detail, in the presence of catalytic amounts of Zn(OAc)2 or NaOAc and methanol 1,2-propylene carbonate (generated by ring closing depolymerization), 1,2-propanediol and dimethyl carbonate (generated by methanolysis) were obtained as beneficial products. Importantly, the selectivity for ring closing depolymerization vs. methanolysis of the polycarbonate depends on various parameters. Moreover, the reaction time is of significance, because in the initial stage of the process the ring closing depolymerization is dominant, while in the further course the amount of the methanolysis products are increasing and the amount of 1,2-propylene carbonate is decreasing, due to conversion by methanolysis. Furthermore, the depolymerization of poly(1,2-propylene carbonate) was connected with a consecutive depolymerization of poly(oxymethylene), that means the depolymerization product 1,2-propanediol acts as depolymerization reagent for poly(oxymethylene) to generate 4-methyl-1,3-dioxolane as suitable compound.