Catalytic Cracking of Polylactic Acid to Acrylic Acid

As a typical type of sustainable plastic, polyesters can be recycled or upcycled into value-added chemicals in a variety of methods. However, excess reagents are required for most of the depolymerization and upcycling processes, causing the emission of environmental pollutants and the waste of chemical resources. Here we demonstrate a one-pot catalytic process to directly crack polylactic acid into acrylic acid by acid catalyst with the assistance of an ionic liquid, Bu4PBr. Polylactic acid is attacked by the Br- from Bu4PBr and the H+ from acid to form oligomers containing Br or acryloyl group, and these oligomers serve as intermediates to produce acrylic acid during their mutual transformation. The acrylic acid is vaporized directly from the reactor and obtained in a collector with a selectivity around 90 % when polylactic acid is fully converted. This green process shows great advantages in atom economy compared to the conventional recycling/upcycling methods for polyesters, in addition, a better efficiency in converting the polymer than the corresponding monomer could inspire new upcycle strategies for different plastic wastes.