Effect of noble metals on the performance of Ni–Mo catalysts for the hydrodeoxygenation of lignin oils to fuels

Improving the catalytic performance in the hydrodeoxygenation (HDO) of lignin oils to produce liquid fuels, while meeting industrial requirements, is important for addressing current environmental challenges. In the present study, the promoting effects of noble metals (Pd, Pt, and Ir) on the performance of the Ni–Mo/CeLa/Al₂O₃ catalyst were investigated in the HDO of a lignin-derived pyrolysis oil. Catalysts were prepared using incipient wetness impregnation, where 0.5 wt% of the noble metals were impregnated on the catalyst in a final, subsequent step. The HDO experiments were conducted either without or with dimethyl disulfide (DMDS) in a batch reactor at 320 °C and 50 bar (initial H₂ pressure at room temperature) for three hours. Interestingly, the highest deoxygenation degree was achieved over the reference catalyst when DMDS was added, in which the resulting oil contained approximately 60% aliphatic and phenolic compounds. Pt showed the most promising promoting effect, which is inferred from its improved hydrogenation capability.