Tandem Catalysis for Plastic Depolymerization: In Situ Hydrogen Generation via Methanol Aqueous Phase Reforming for Sustainable Polyethylene Hydrogenolysis

Depolymerizing plastic waste through hydrogen-based processes, such as hydrogenolysis and hydrocracking, presents a promising solution for converting plastics into liquid fuels. However, conventional hydrogen production methods rely heavily on fossil fuels, exacerbating global warming. This study introduces a novel approach to plastic waste hydrogenolysis that utilizes in situ hydrogen generated via the aqueous phase reforming (APR) of methanol, a biomass-derived chemical offering a more sustainable alternative. Our results show that a bimetallic Ru−Pt/TiO₂ catalyst achieved high conversion (85.1 %) and selectivity (81.0 %) towards liquid fuels and lubricant oils in a tandem process combining polyethylene (PE) hydrogenolysis and methanol APR. By tuning the metal loading, we identified that Pt enhances hydrogen production through methanol APR, while Ru drives C−C bond cleavage, which is crucial for PE hydrogenolysis. Isotope labeling analysis confirmed that hydrogen generated from methanol APR is effectively utilized in the PE hydrogenolysis reaction. This method was also successfully applied to post-consumer polyolefin waste, with selectivity toward valuable products ranging from 75.0 % to 88.9 %. This study highlights an innovative strategy to reduce reliance on fossil-fuel-derived hydrogen in plastic waste depolymerization, promoting both sustainability and environmental protection.