Synthesis of aromatic monomers via hydrogenolysis of lignin over nickel catalyst supported on nitrogen-doped carbon nanotubes

The utilization of lignin to produce high value-added chemicals remains a significant challenge, this study reports the synthesis of highly active nitrogen-doped carbon nanotubes to support nickel-based catalysts via a two-stage pyrolysis process using a mixture of melamine and nickel acetate. The catalyst morphology is controlled through the use of melamine, the doped pyridinic nitrogen serves as an anchoring site for Ni metal, facilitating the dispersion of Ni metal and the formed Ni-Nx bond enhanced the stability of the catalyst. Additionally, the electron transfer between Ni and N atoms promoting the activation of hydrogen on the metallic nickel surface, which together with the aforementioned factors, contributes to the cleavage of the C-O bond in lignin, with 23.1% monomer yield under mild conditions. The density functional theory (DFT) calculations reveal that doped nitrogen atoms can provide electrons to carbon atoms, resulting in an electron-rich state that facilitated the adsorption of hydrogen.