Efficient hydrotreatment of waste tire pyrolysis oil using N-doped biochar loaded with cobalt-molybdenum carbide

Pyrolysis technology converts waste tires into waste tire pyrolysis oil (WTPO), which has a high calorific value (41.63MJ/kg). WTPO yields up to 57.87 wt% at 475 °C, but its high sulfur and nitrogen content restricts its applications. To address this issue, we used the nitrogen-doped biochar (NBC) as carriers to prepare Co-Mo₂C/NBC catalysts for hydrotreating WTPO. The results demonstrated that N-doping enhanced the dispersion of Mo₂C, strengthened the interaction between the catalyst and the carrier, and improved the catalyst's ability to adsorb and activate hydrogen. Furthermore, Co promoted Mo carburization, resulting in the formation of more Mo₂C and imparting greater Lewis acidity to the Co-Mo₂C/NBC catalyst. Moreover, the presence of Co enriched Mo with electrons, thereby facilitating both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions. Specifically, the removal of S and N from WTPO using Co-Mo₂C/NBC reached 99.6 % and 89.3 %, respectively, at 330 °C and 6 MPa hydrogen pressure, which eliminated the colored unsaturated molecules in WTPO and improved the oxidation resistance of WTPO. Notably, the Co-Mo₂C/NBC catalyst showed excellent stability, and the S removal remained above 97.8 % after seven reuse cycles. This study provides insights into the development of efficient hydrotreating catalysts for WTPO.