Catalytic Conversion of Lignin and Lignin-Derived β-O-4 Ether to Cyclohexanols over a CeO2-Doped Carbon-Supported Nickel-Based Catalyst

In this study, a CeO2-doped carbon-supported nickel-based catalyst (Ni/XCeO2–C–Y) was synthesized and applied to the catalytic depolymerization of lignin and its derivatives. The variations in CeO2 content and calcination temperature are observed to cause a notable impact on the existence of oxygen vacancies. The results demonstrated that an optimal Ni/20%CeO2–C-500 exhibited excellent effectiveness in the cleavage of the β-O-4 bond to ethylbenzene and cyclohexanol at 180 °C and 1 MPa N2. In this system, isopropanol is used as a hydrogen-donating solvent as it can produce H2 (detected by GC) during the reaction. The successful doping of CeO2 onto carbon contributes to the formation of an interaction between the carrier and nickel, causing a more uniform dispersion of metallic Ni. In addition, the selectivity of phenols in the real lignin depolymerization decreased from noncatalytic 71.5 to 25.4%, and most of the phenols were well converted into cyclohexanols and ketones. The reusability experiments revealed that Ni/20%CeO2–C-500 possessed excellent recycling and regeneration properties.