Synergistic Effect of Ru–Ni Nanoparticles for Enhanced Amination Upcycling of Polylactic Acid Plastic Waste into Alanine

Chemical upcycling of plastic waste into high-value chemicals and fuels is a promising strategy to combat global plastic pollution and advance a circular economy. Herein, we designed a series of bimetallic RuNi/CeInOx catalysts with different ratios of Ru/Ni for the amination of polylactic acid (PLA) plastic waste into alanine. It was noticed that the optimized Ru3Ni5/CeInOx exhibited exceptional performance, delivering a high alanine yield of 83.7% with an alanine production rate of 3.74 molAla molRu–1 h–1 at 180 °C for 18 h under 0.1 MPa N2, which was apparently higher than that of previously reported catalysts. Systematic investigations revealed that the remarkably enhanced catalytic performance primarily stemmed from the synergistic effect between Ru and Ni nanoparticles, which produced enriched oxygen vacancies, promoted a smaller particle size of Ru nanoparticles, and reinforced the interaction between Ru and Ni species, cooperatively accelerating the reaction rates of dehydrogenation, amination, and hydrogenation processes in converting PLA to alanine. Moreover, it maintained excellent cycling stability over three consecutive cycles. This study provides critical insights into constructing highly efficient bimetal catalysts for the amination upcycling of polylactic acid plastic waste into valuable chemicals.