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

Abstract

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-Ni-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 degrees C and 55 bar of hydrogen (H-2) pressure. Moreover, Ru-NiO/TiO2 catalyst could also be easily recovered and reused up to four runs without notable change in original activity. (C) 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.