Ru–NiOx nanohybrids on TiO₂ support prepared by impregnation-reduction method for efficient hydrogenation of lactose to lactitol

Lactose is a reducing disaccharide consisting of two different monosaccharides such as galactose and glucose. The hydrogenation of lactose to lactitol is a formidable challenge because it is a complex process and several side products are formed. In this work, we synthesized Ru–Ni bimetallic nanohybrids as efficient catalysts for selective lactose hydrogenation to give selective lactitol. Ru–Ni bimetallic nanohybrids with Ru–NiO_x (x = 1, 5, and 10 wt%) are prepared by impregnating Ru and Ni salts precursors with TiO₂ used as support material. Ru–Ni bimetallic nanohybrids (represented as 5Ru–5NiO/TiO₂) catalyst is found to exhibit the remarkably high selectivity of lactitol (99.4%) and turnover frequency i.e. (374 h⁻¹). In contrast, monometallic Ru/TiO₂ catalyst shows poor performance with (TOF = 251 h⁻¹). The detailed characterizations confirmed a strong interaction between Ru and NiO species, demonstrating a synergistic effect on the improvement on lactitol selectivity. The impregnation-reduction method for the preparation of bimetallic Ru–NiO/TiO₂ catalyst promoted Ru nanoparticles dispersed on NiO and intensified the interaction between Ru and NiO species. Ru–NiO/TiO₂ efficiently catalyzed the hydrogenation of lactose to lactitol with high yield/selectivity at almost complete conversion of lactose at 120 °C and 55 bar of hydrogen (H₂) pressure. Moreover, Ru–NiO/TiO₂ catalyst could also be easily recovered and reused up to four runs without notable change in original activity.