Efficient hydrodeoxygenation of guaiacol to phenol over Ru/Ti–SiO2 catalysts: the significance of defect-rich TiOx species.

Selective hydrodeoxygenation of lignin-derived phenolics to value-added aromatic products such as phenol with high efficiency and low energy consumption remains an important challenge in the field of biomass conversion. Herein, we fabricated a series of Ti-modified SiO2 supported catalysts (Ru/Ti–SiO2) with rich Ti3+ defects and size-controllable Ru particles via a facile wet impregnation method for the conversion of guaiacol in an aqueous phase. Under relatively mild conditions (240 °C and 0.4 MPa H2), Ru/Ti–SiO2 exhibited higher activity for C–O bond cleavage compared with both Ru/SiO2 and Ru/TiO2 catalysts, and achieved high guaiacol conversion (83.6%) and phenol selectivity (70.4%). The catalytic activity was increased with the introduction of the Ti modifier, and the deoxygenation ability of the Ru/Ti–SiO2 catalyst gradually increased with the Ti content. The presence of Ti–O–Si linkages in the Ti-modified SiO2 support promoted the formation of defect-rich TiOx species, which further inhibited the aggregation of Ru particles and increased their dispersion, regardless of the high reduction temperature and high Ru loading. Besides, those small-sized TiOx interacted with Ru electronically and promoted the formation of Ru0 species. The interface between Ru and TiOx species (Ru0–Ti3+) of the Ru/Ti–SiO2 catalyst was confirmed as the main active sites for the deoxygenation of guaiacol, benefiting the activation of the C–O bond. [ABSTRACT FROM AUTHOR]