Boosting the selective catalytic pyrolysis of plastic waste polylactic acid to monomer

Polylactic acid (PLA), as the most popular biodegradable polymers, has considered as a potential substitute for the petroleum-based plastics, but its large-scale applications are still limited because of lacking advisable wastes management strategies. Herein, we report a heterogeneous bimetallic FeNi catalyst for the selective catalytic pyrolysis of PLA to monomer under the isothermal temperature, solvent-free conditions. A series of Fe-based catalysts were prepared with a view to facilitate lactide conversion and improve its selectivity by tuning the properties of all Fe species. The optimal catalyst Fe10Ni1 @NC shows excellent catalytic performance with a 73% yield of lactide, which is mainly attributed to the "synergistic effect" between all Fe species sites and FeNi alloys and the basic of N-dope carbon matrix. It's discovered that Fe/Fe,C/Fe3O4 sites are beneficial for the cleavage of ester linkages, and the FeNi alloys formed by introducing low amounts of Ni to Fe sites show better selectivity for the ring cyclization step. This work not only develops the pyrolysis methods of biodegradable plastic wastes to obtain the high-value chemicals and also contributes toward a circular economy.