Carbon-modified TiO2 catalysts for oxidative upcycling of waste polyethylene to dicarboxylic acids

Abstract

Catalytic oxidation offers a promising green approach for converting polyethylene (PE) into valuable oxygenated products under mild conditions. However, its large-scale application is hindered by the high cost and limited activity of existing catalysts. Here, we report a metal-free, carbon-modified TiO2 (C/TiO2) catalyst for efficient oxidative conversion of PE under mild conditions (150 °C, 1.5 MPa air). After 24 h of reaction, a 120 wt% product oil-to-feedstock mass ratio and 74% carbon molar conversion (based on product oil) were achieved. The product oil primarily consists of long-chain dicarboxylic acids, confirmed by Fourier transforms infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and highresolution mass spectrometry (HRMS). Importantly, C/TiO2 also effectively converts real post-consumer PE plastics containing pigments, yielding similar product profiles. Spectroscopic and microscopic analyses reveal that carbon deposition increases oxygen vacancies, enhancing catalytic activity. This work offers an economic strategy for sustainable plastic waste valorization via tunable catalyst surface engineering.