Biomass-Derived NiO-Biochar Catalyst for Transfer Hydrogenation of Furfural to Furfuryl Alcohol

A NiO-supported biochar catalyst derived from Syngonium podophyllum was prepared via a simple impregnation–calcination method and evaluated for the Meerwein–Ponndorf–Verley (MPV) reduction of furfural to furfuryl alcohol using isopropanol as both solvent and hydrogen donor, tackling the well-known challenge of suppressing side reactions and preserving selectivity toward furfuryl alcohol. Structural and surface characterization by XRD, XPS, SEM–EDS, ICP-OES, TGA, and FTIR confirmed the successful deposition of NiO species on the biochar surface and the preservation of the carbonaceous support. XPS analysis revealed surface enrichment of Ni species and the presence of accessible Ni 2 ⁺ coordination sites associated with NiO particles, which interact with oxygen-containing functional groups in the biochar matrix. Catalytic tests demonstrated that the NiO–biochar catalyst is active for furfural transfer hydrogenation, reaching 96% furfural conversion and 61% furfuryl alcohol yield at 130 °C under optimized conditions. Parameter studies revealed that catalyst loading, solvent volume, and temperature strongly influence catalytic performance by affecting active site availability and adsorption equilibria at the catalyst surface. Catalyst reuse experiments indicated gradual deactivation, which was attributed to the formation of polymerized carbonaceous deposits (humins) on the catalyst surface, as confirmed by TGA and FTIR analyses. Carbon balance calculations showed that part of the substrate carbon is retained as polymeric deposits on the catalyst. Overall, the results demonstrate that biochar derived from lignocellulosic residues can serve as a sustainable support for metal oxide catalysts, offering a promising alternative to conventional synthetic catalyst supports for biomass upgrading reactions.