Upcycling of Polyethylene Wastes to Valuable Chemicals over Group VIII Metal-decorated WO₃ Nanosheets

Catalytic cracking of polyolefin wastes into valuable chemicals at mild conditions using non-noble metal catalysts is highly attractive yet challenging. Herein it is reported that 2D tungsten trioxide (2D WO₃) nanosheets, after decorating with group VIII metal promoters (i.e., Fe, Co, or Ni), convert high-density polyethylene (HDPE) into alkylaromatics and olefins at low temperature and ambient pressure without using any solvent or hydrogen: 2D Ni/WO₃ with abundant Brønsted acidic sites initiates HDPE cracking at a low temperature of 240 °C; 2D Fe/WO₃ with low energy barrier of cyclization achieves a high HDPE conversion to 84.2% liquid hydrocarbons with a selectivity of 30.9% to aromatics at 300 °C. In-situ spectroscopic investigations and supplementary theoretical calculations illustrate that these aromatics are formed through the cyclization of alkene intermediates. These 2D catalysts also display high efficiency in the low-temperature cracking of single-use commercial polyethylene wastes such as packaging bags and bottles. This work has demonstrated the high potential of 2D non-noble metal catalysts in the efficient upcycling of waste polyolefin at mild conditions.