Low-temperature upcycling of waste polyethylene terephthalate into fuel additives over diffusion-enhanced hollow Ru/ZSM-5

The growing accumulation of waste polyethylene terephthalate (PET) has raised great concern about its effective upcycling. Catalytic fast pyrolysis is a promising method for selectively upcycling of waste PET into aromatics. However, the high temperature and poor mass transfer performance remain considerably challenging. In this research, a diffusion-enhanced hollow ZSM-5 catalyst with Ru modification was designed for low-temperature valorization of waste PET into aromatics. Ru species significantly enhanced the primary depolymerization of long-chain polymers by generating abundant Lewis acid sites, which markedly increased the aromatics content. Additionally, the mesopore-rich structure formed after Ru-modification improved diffusion capacity of products effectively. The existing of active Ru 0 species was beneficial to the hydro-upgrading of oxygen-containing intermediates, therefore monocyclic aromatic hydrocarbons (MAHs) content and hydrogen atom utilization increased to a great extent. More gratifyingly, the pyrolysis temperature for preparing aromatics from waste PET was obviously lowered, probably due to the synergistic effect of diffusion-enhanced structure and Ru modification. Ru/ZH exhibited higher aromatics yield of 46.4 wt% with selectivity of 95.3 % at 500 °C, resulting in a significant mass yield increase of 93.1 % compared to unmodified hollow ZSM-5 (24.0 wt%). Finally, the plausible pathway for PET-to-aromatics via catalytic fast pyrolysis over Ru/ZH was proposed.