Eco-Friendly Preparation of Ultrathin Biomass-Derived Ni3S2-Doped Carbon Nanosheets for Selective Hydrogenolysis of Lignin Model Compounds in the Absence of Hydrogen

Lignin is the abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-valued chemicals. Selectively hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CSs catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Y derived catalysts were produced using the different compositions under different temperatures (X=0 mg, 0.2 mg, 0.4 mg, 0.6 mg, 0.8 mg; Y=600 ℃, 700 ℃, 800 ℃, 900 ℃) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of corresponding obtained ethylbenzene and phenol could achieve 92% and 86% respectively over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 ℃ without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage the lignin ether bounds. The physicochemical characterizations were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Roman and XPS analysis. Based on the optimal reaction condition (260 ℃，4 h, 2.0 MPa N2), various of model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in next five consecutive cycle experiments with slight decrease of the transformation of lignin model compounds.