From Waste to Fuel: Coprocessing Waste Tire Pyrolysis Oil with Atmospheric Gas Oil to Produce Ultralow-Sulfur Diesel

In waste management, pyrolysis is a promising route for the energy valorization of waste tires. However, the resulting pyrolysis oil requires upgrading to serve as an alternative or recycled fuel comparable to middle distillates. Like other waste-derived materials (e.g., animal fats and used cooking oils), a coprocessing approach offers a viable solution for hydrotreating this oil within the existing refinery infrastructure. This study examines the coprocessing of atmospheric gas oil with waste tire pyrolysis oil at varying ratios (5–20 wt %) under industrial operating conditions (T = 330–390 °C, P = 5.5 MPa, and WHSV = 1 h–1) in a pilot-scale hydrotreating unit using a commercial Ni-Mo/Al2O3 catalyst. This process upgraded waste tire pyrolysis oil into middle distillate compounds and integrated it into the diesel fuel matrix. However, higher concentrations of waste tire pyrolysis oil in the feedstock negatively affected catalyst activity and worsened specific properties of the hydrotreated product, including the density, flash point, and cetane index. Our results highlight the optimal coprocessing ratio to effectively upgrade waste tire pyrolysis oil into a valuable recycled fuel without compromising catalyst activity, yielding an ultralow-sulfur diesel fuel.