Transforming biomass tar into a highly active Ni-based carbon-supported catalyst for selective hydrogenation-transalkylation of guaiacol

The development of a carbon-based catalyst for selective transformation of renewable lignin to value-added chemicals is a fascinating chemical upgrade route. In this study, the highly efficient Ni/C catalysts derived from waste biomass tar was fabricated for selective hydrogenation-transalkylation (HTTA) of guaiacol to 1-methyl-1,2-cyclohexanediol. Carbonization temperatures and activators can be used to regulate the contents of oxygen-containing functional groups on carbon surface, which further affect the catalytic performance. Results showed that the Ni/C-K-800 catalyst with KOH as activator and 800 degrees C as carbonization temperature exhibited the excellent catalytic performance (about 100 % conversion) for the guaiacol transformation at 220 degrees C, 2 MPa H-2 for 2 h, and the final product could be stably controlled at 1-methyl-1,2-cyclohexanediol. Main reaction pathway of guaiacol over Ni/C catalyst was proposed: 1) conversion of guaiacol to 1-methyl-1,2-cyclohexanediol through transalkylation and hydrogenation of benzene ring; 2) transform of 1-methyl-1,2-cyclohexanediol to cyclohexanol through direct hydrogenolysis. Furthermore, biomass tar-derived carbon support has good resistance towards carbon accumulation on Ni metals. These findings can provide a basis for designing green and efficient catalyst derived from biomass tar for biomass upgrading.