Enhancement in the metal efficiency of Ru/TiO2 catalyst for guaiacol hydrogenation via hydrogen spillover in the liquid phase

Abstract

Decrease in the metal dispersion of noble-metal-loaded catalysts with high metal loading is a major factor reducing noble-metal efficiency. Herein, we investigated the enhancement in metal efficiency of Ru/TiO2 catalyst by utilizing hydrogen spillover in the liquid-phase. Ru was highly dispersed at low loadings (0.1 and 0.5 wt%), while larger nanoparticles were formed at higher loadings (1-5 wt%). The hydrogen spillover in liquid phase was activated at reaction temperature (100 degrees C) as the Ru dispersion decreased, which was confirmed through physical dilution experiments, hydrogen temperature-programmed-reduc tion, and kinetic analysis. Isotope experiment was conducted using D2O, observing inverse kinetic isotope effect (IKIE) for the high-Ru-loading catalysts. Based on the understanding of the hydrogen spillover in the liquid phase, the low metal efficiency of high-Ru-loading catalysts resulting from low dispersion could be compensated simply by physically mixing pristine TiO2, which played a role as new active sites when liquid-phase hydrogen spillover was activated. (C) 2022 Elsevier Inc. All rights reserved.