In-situ catalytic hydrogenation-liquefaction of lignin: Role of heat and mass transfer.

A novel method that combined in-situ hydrogenation-liquefaction and intensified heat and mass transfer was proposed for efficient catalytic hydrothermal liquefaction of enzymatic hydrolysis lignin. The strategy enhanced heat and mass transfer, significantly accelerating lignin conversion from 79.30 wt% to 89.22 wt%, with the deoxidation rate rising from 1.27% to 68.53% and bio-oil HHV reaching 33.51 MJ/kg. Under these conditions, applying Ni/β-AlO, Ni/MgO-AlO, and Ni/MgO catalysts further increased bio-oil HHV to 33.54, 33.58, and 34.84 MJ/kg, respectively, while maintaining conversion efficiency. These catalysts with different metal-support interactions and acid-basic sites exhibited varied adsorption and hydrogenation characteristics, leading to aromatic hydrocarbon yield of 6.00-7.09%, and phenolic concentration increased from 61.37% to 82.53%. The performance was attributed to adsorption selectivity coupled with intensified heat and mass transfer, and the catalysts' mesopore properties mitigated mass transfer limitations in pores, facilitating selective adsorption/desorption and CO bond cleavage of intermediates on active sites.