Selective Hydrodeoxygenation of Lignin and Its Derivatives without Initial Reaction Pressure Using MOF-Derived Carbon-Supported Nickel Composites

In this study, Ni-metal–organic frameworks (MOFs) were used as precursors to obtain carbon-supported nickel composites (Ni@C) after calcination. The hydrodeoxygenation properties of the model compound and corncob lignin were investigated without an external hydrogenation source and initial pressure. Additionally, the effect of Ni@C on degradation of model compounds, corncob lignin, and benzyl phenyl ether (BPE) under different conditions was examined. The results showed that with isopropanol as the in situ hydrogen source, the conversion percentage of BPE was 90.2% and the yield of phenol was 88.3 wt % at 150 °C. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), NH3 temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG), and the lignin and bio-oil were characterized by gas chromatography–mass spectrometry (GC–MS) and two-dimensional heteronuclear single quantum coherence (2D-HSQC). It was found that the Ni@C catalyst with well dispersion, high support rate, and rich acid sites was successfully synthesized. In the process of degradation, the C–O ether bond in the structure of lignin was successfully broken to generate the phenolic monomer, and the high-efficiency hydrodeoxygenation of lignin was realized under mild conditions.