Highly efficient valorization of waste polylactic acid for alkyl lactate production by dispersions of ultrasmall ZnO nanoparticles

Abstract

The valorization of waste polylactic acid (PLA) for the production of high value-added chemicals is a sustainable way to avoid carbon resource waste and promote circular economy. Here, we report a one-step catalytic process to highly efficient convert waste PLA into methyl lactate (MeLA) by methanolysis with dispersions of ultrasmall ZnO nanoparticles (4–5 nm) as catalysts. The PLA conversion and MeLA yield reach above 99 % and 95 % at 110 ℃ in 15 min, respectively. The catalytic activity and energy economy coefficient of the as-prepared catalyst exceed those of other reported PLA methanolysis catalysts. Furthermore, we showcase the application of this methodology to a wide range of commercial samples. More importantly, the catalyst exhibits excellent depolymerization effect on PLA in other alcohols (ethanol, ethylene glycol). This study provides a feasible strategy for upgrading end-of-life PLA into valuable chemicals and contributing to green and circular economy.