Anchoring site rich mesoporous alumina-supported Pt catalysts for hydrotreatment of the light fraction of waste plastic pyrolysis oil

Abstract

Catalytic hydrotreatment is important for upgrading waste plastic pyrolysis oil (WPPO) into stable, fuel-compatible hydrocarbon streams, yet the catalyst design principles governing heteroatom removal, particularly hydrodenitrogenation (HDN), remain poorly understood. Here, we show that penta-coordinated AlO5 defect sites in mesoporous alumina play a dual role: they anchor platinum and enhance its dispersion, but excessive anchoring stabilizes oxidized Pt species (Ptx⁺) at the expense of catalytically active metallic Pt0. Consequently, the catalyst with the highest Pt dispersion (Pt/m-Al2O3-400) did not yield the best HDN performance; instead, Pt/m-Al2O3-600 achieved over 85 % removal of nitrogen, sulfur, and chlorine from the light WPPO fraction at 350 °C. GC×GC–TOF/MS analysis revealed that olefin hydrogenation was largely complete by 300 °C, while nitrogen-containing compounds persisted due to the high activation barrier for C–N bond cleavage. These findings establish that HDN activity in Pt/Al2O3 systems is dictated by a critical balance between Pt dispersion and accessible metallic Pt0 sites, which can be effectively optimized by tuning the density of AlO5 defect sites. This structure–activity insight offers a rational basis for designing hydrotreatment catalysts tailored to low-sulfur, heteroatom-rich pyrolysis oil. Copyright © 2026. Published by Elsevier Ltd.