Optimizing biofuel production: Direct integration and co-hydroprocessing of hydrolysis lignin into oil refineries over an unsupported NiMoP catalyst

Journal article, 2025

Our study investigates the production of drop-in fuels by co-hydroprocessing solid hydrolysis lignin in a batch reactor operated in cycling mode. To simulate the blending potential with lignin oil, we utilized petroleum-derived intermediates like hexadecane and VGO. We demonstrate the significant production of blended lignin-oil through direct co-hydroprocessing of hydrolysis lignin and its hydroprocessed oil using a spent catalyst. The reactivity of hydrolysis lignin is influenced by its interaction with organic mediators in the lignin-oil blends. For hydrotreated lignin in hexadecane, we observed an 83.4 wt% yield of lignin monomers, predominantly isomeric alkane-derived, including cycloalkanes. Co-hydroprocessing with fresh lignin increased lignin-oil blend yield and reduced char formation. Additionally, the NiMoP loading significantly boosted naphtha and light gas oil yields. Co-hydroprocessing with VGO exhibited a slightly higher yield of 85.6 wt%, accompanied by a significantly lower char yield of 1.6 wt% compared to the uncatalyzed reaction, which yielded 33.7 wt% char. The enhanced reactivity and affinity with VGO resulted in improved selectivity towards naphthenes and aromatics. Overall, higher catalyst loadings promoted dealkylation and deoxygenation reactions while suppressing char formation, remarkably evident with VGO in multicycling. Interestingly, multicycling led to a higher bio-oil yield and lower char formation. Furthermore, our study suggests that co-hydroprocessing with intermittent feeding of hydrolysis lignin in a sequential operation mode can achieve deep deoxygenation, higher energy yield, and mass lignin-oil yields while maximizing the distillate range of jet and marine fuel fractions, as qualitatively evident using funnel plots.