Recycling post-consumer PLA into acrylic acid or lactide using phosphonium ionic liquids

Abstract

Post-consumer poly(lactic acid) (PLA) is recycled to high value monomers, either acrylic acid (AA) or lactide (LAC), using a phosphonium ionic liquid as the active solvent, in the presence or absence of an acid cocatalyst. Chemical recycling of polymer waste to the original monomer (CRM) forms an important concept for a circular plastic economy. For poly(lactic acid) (PLA) this is often neglected as a result of PLA's known biodegradability. However, such degradation leads to the undesired generation of CO 2 , associated with a poor energy efficiency and a missed opportunity for fast circular reuse. In this work, we develop a system to recycle post-consumer PLA into either acrylic acid (AA) or lactide (LAC), depending on the presence/absence of an acidic cocatalyst and the applied reaction conditions. A detailed time profile showed that PLA is first converted into LAC and subsequently rearranged to AA under acidic conditions. Up to 50% of monomer yield was achieved in a single step, using a phosphonium ionic liquid (Bu 4 PBr) as the active solvent and only 5 mol% of organic cocatalyst.