Reductive Catalytic Fractionation of Birch Wood in Ethanol Medium over a Novel Bifunctional Catalyst Ni/HfO2

A novel bifunctional catalyst based on Ni supported on hafnium oxide was prepared to
\ndepolymerise birch wood lignin. A native lignin fraction of birch wood was promptly depolymerised
\ninto valuable phenolic monomers, enriched with propenylsyringol through one-pot catalytic reductive
\nfractionation at 225 °C, and 4 MPa H2 during 3 hours. The yield of liquid products increased from
\n23 to 37 wt.% under the hydrogenation in the presence of catalyst. Detailed Brunauer- Emmett-Teller,
\nрН of the point of zero charge, and X-ray photoelectron spectroscopy investigations revealed that the
\nmetal–acid synergistic effect in the presence of acid sites and of both Ni2+ and Ni 0 were responsible for
\nthe breaking of C–C bond, ester and ether linkages bonds in lignin. Moreover, modifying catalyst by
\nphosphoric acid generated propenylsyringol in higher yield. Overall, this report highlighted the potential
\nof the simple preparation strategy of the bifunctional catalyst based on Ni supported on acidic HfO2 to
\ndepolymerize wood lignin and proposed possible mechanism for reductive catalytic fractionation of
\nbirch wood biomass