Catalytic hydroconversion of poplar lignin over a nitrogen-doped carbon material-supported nickel prepared by in situ co-pyrolysis

A nitrogen-doped carbon material-support nickel was prepared by two-step in situ co-pyrolysis of glucosamine hydrochloride, melamine (MA), and Ni(NO3)2·6H2O, and used for the catalytic hydroconversion (CHC) of poplar lignin (PL). Under 2 MPa of initial H2 pressure at 270 °C for 4 h, 91.7 wt% of soluble portion and 24.7 wt% of aromatic monomer yield were obtained from the CHC of PL over Ni10/NDCMD. The characterization results confirmed that adding MA resulted in a larger specific surface area, abundant mesoporous structure, and defect sites, facilitating the dispersion of Ni-Nx and promoting the diffusion and mass transfer of PL and its intermediates. In addition, pyridinic nitrogen provides abundant anchoring sites for nickel atoms to inhibit Ni-Nx accumulation and increase metal-support interactions. Therefore, Ni10/NDCMD with better texture and more Ni-Nx sites exhibited excellent catalytic activity and recycle stability for the CHC of PL.