Upcycling Single-Use Polyethylene into High-Quality Liquid Products

TLDR

Synthetic polymers are essential to modern life, yet inefficient recycling and slow degradation of plastics raise environmental concerns, and single‑use materials are largely wasted, underutilizing their chemical and energy value. The study aims to convert energy‑rich polyethylene into value‑added liquid products through catalytic hydrogenolysis. Catalytic hydrogenolysis is performed using well‑dispersed Pt nanoparticles supported on SrTiO₃ perovskite nanocuboids prepared by atomic layer deposition. Pt/SrTiO₃ fully converts polyethylene or a single‑use plastic bag into high‑quality lubricants and waxes with a narrow oligomer distribution at 170 psi H₂ and 300 °C under solvent‑free conditions for up to 96 h; adsorption studies and DFT calculations show PE binds more favorably to Pt sites, while smaller Pt nanoparticles with more undercoordinated sites over‑hydrogenolyze PE to light hydrocarbons.

Abstract

Our civilization relies on synthetic polymers for all aspects of modern life; yet, inefficient recycling and extremely slow environmental degradation of plastics are causing increasing concern about their widespread use. After a single use, many of these materials are currently treated as waste, underutilizing their inherent chemical and energy value. In this study, energy-rich polyethylene (PE) macromolecules are catalytically transformed into value-added products by hydrogenolysis using well-dispersed Pt nanoparticles (NPs) supported on SrTiO3 perovskite nanocuboids by atomic layer deposition. Pt/SrTiO3 completely converts PE (Mn = 8000-158,000 Da) or a single-use plastic bag (Mn = 31,000 Da) into high-quality liquid products, such as lubricants and waxes, characterized by a narrow distribution of oligomeric chains, at 170 psi H2 and 300 °C under solvent-free conditions for reaction durations up to 96 h. The binding of PE onto the catalyst surface contributes to the number averaged molecular weight (Mn) and the narrow polydispersity (Đ) of the final liquid product. Solid-state nuclear magnetic resonance of 13C-enriched PE adsorption studies and density functional theory computations suggest that PE adsorption is more favorable on Pt sites than that on the SrTiO3 support. Smaller Pt NPs with higher concentrations of undercoordinated Pt sites over-hydrogenolyzed PE to undesired light hydrocarbons.