Distillery-Waste-Derived C-SiO₂ Catalyst Support Reinforces Phenol Adsorption and Selective Hydrogenation

Selective hydrogenation of lignin-derived phenolic compounds is an essential process for developing the sustainable chemical industry and reducing dependence on nonrenewable resources. Herein, a composite C-SiO₂ material (DGC) was prepared via the stepwise pyrolysis and steam activation of the distiller's grains, a fermentation solid waste from the Chinese liquor industry. After Ru loading, Ru/DGC was used for the catalytic hydrogenation of phenol to cyclohexanol. Steam activation remarkably increased the hydrophilicity and specific surface area of DGC, introducing oxygen-containing functional groups on the surface of DGC, thereby promoting the adsorption of Ru³⁺ and phenol. Additionally, the large specific surface area facilitated the dispersion of the active metal. Furthermore, the steam activation of DGC promoted the graphitization of the carbon matrix and formed Si-H/Si-OH bonds on the SiO₂ surface. The benzene ring of phenol interacted with the carbon matrix via π-π stacking, and the hydroxyl group of phenol interacted with SiO₂ via hydrogen bonding. The synergistic interactions of phenol at the C-SiO₂ interface enhanced phenol adsorption to promote the hydrogenation. Consequently, 100 % of phenol was hydrogenated to cyclohexanol at 60 °C within 30 min. Furthermore, the optimized catalyst exhibited high activity for phenol hydrogenation even after four reuse cycles. The outstanding stability of the catalyst and its requirement for mild reaction conditions favor its large-scale industrial applications.