Full Utilization of Hard-to-Recycle Mixed Plastic Waste by Conversion toward Pyrolysis Oil and BTX Aromatics on a Pilot Scale

This study investigates the technological feasibility of recycling mixed plastic waste streams into chemical building blocks on a pilot scale. Postconsumer-separated DKR-350 mixed plastic waste was first separated into two fractions by using a two-step negative near-infrared (NIR) optical sorting process. The resulting two fractions (polyolefin-rich and polyolefin-poor) were subjected to thermal and ex situ catalytic pyrolysis, respectively. Both types of pyrolysis were performed in a fluidized bed pilot plant, continuously operated at feed rates of 5 kg h^-1 and temperatures ranging from 460 to 550 °C. The polyolefin (PO)-rich fraction (∼81 wt % PE + PP) resulted in a maximum aliphatic-rich oil yield of 48 wt % and 26 wt % gas yield based on dry material intake. The PO-poor fraction, characterized by a lower PE/PP content (∼13 wt %) and high in PET and PS (43.5 and 14.4 wt %, respectively) normally unsuitable for efficient thermal pyrolysis, was processed through integrated cascading catalytic pyrolysis (ICCP) using a proprietary zeolite-based catalyst. This allowed for the successful transformation to 37 wt % aromatic-rich oil, with a total benzene, toluene, and xylenes (BTX) yield of 17 wt %, and 42 wt % gas. The high PET and PS content in the PO-poor fraction contributed to a significant increase in aromatic yields compared to the expected yield of a mixed plastic waste stream. This study thus demonstrates the potential to produce a full range of petrochemical building blocks, i.e., olefins and aromatics, from low-quality, hard-to-recycle plastic waste streams. Importantly, this work highlights that catalytic pyrolysis of the PO-poor residue stream, postsorting to yield PO-enriched streams, can effectively valorize this fraction, underscoring the technological viability of improved plastic recycling through targeted sorting and pyrolysis.