Catalytic Hydrotreatment of Kraft Lignin over NiW/SiC: Effective Depolymerization and Catalyst Regeneration

A key challenge in biomass catalytic conversion, especially in pilot and practical scales, is the stability of the catalyst and its support. Depolymerization of Kraft lignin, which is characterized by structural recalcitrance and poison (metal and ash) rich nature, is a good model reaction to demonstrate the above challenge in biomass conversion. In the present study, the potential of SiC-based catalyst (commercially available SiC nanofiber-supported Ni and W, NiW/SiC) in lignin depolymerization was investigated. The results indicate the SiC-based catalyst is a milder catalyst than the state-of-the-art activated carbon-supported catalyst under the identical conditions and supplies a higher liquid product yield. More importantly, the NiW/SiC catalyst can be easily regenerated by coke combustion and subsequent acid washing, which cannot be achieved by either carbon or metallic oxide-supported catalysts. The performance of the regenerated catalyst with only 4% Ni input is almost unchanged compared with that of the fresh catalyst. These results illustrate that SiC combines the advantages of common supports such as activated carbon and metallic oxides and may be generally applicable as catalyst support in biomass conversion.