(206h) Production of Propylene from Polypropylene Waste Via Direct Microwave Catalytic Upcycling

Plastic waste crisis has led to severe environmental pollution and an obvious imbalance between production and upcycling. Although conventional catalytic depolymerization can be used for converting plastic waste into chemicals, it remains a significant challenge to achieve high selectivity towards value-added monomers using a one-step method under mild conditions. In this work, we report the high yield of propylene from polypropylene waste through a direct microwave-assisted catalytic process under mild conditions (ambient pressure, 400℃). The conversion of polypropylene reaches 100% with propylene yield up to 55 wt.% using Ru/Fe₂O₃ as a catalyst at 400℃ under microwave irradiation. In contrast, there is no conversion of polypropylene under thermal conditions at 400℃. As the reaction temperature under thermal conditions is increased to 600 °C, polypropylene conversion reached 100%, albeit with a lower propylene yield of 43 wt.%.

In addition, the reaction mechanism of upcycling polypropylene waste into propylene under microwave irradiation was analyzed by in-situ FTIR, in-situ Raman, and DFT calculation, as shown in Figure 1. Meanwhile, the microwave heating behaviors were studied by COMSOL modeling.

The combination of microwave-assisted catalytic upcycling and efficient microwave-sensitive catalyst is a promising approach to revolutionize plastic waste upcycling, turning a global environmental challenge into an industrially and economically valuable resource.