Selective oxidation of glycerol to formic acid catalyzed by Ru(OH)4/r-GO in the presence of FeCl3

Abstract

Herein selective oxidation of glycerol to formic acid catalyzed by Ru(OH)4 nanoparticles decorated on reduced graphite oxide (r-GO) in the presence of FeCl3 was presented. The Ru(OH)4/r-GO catalyst was prepared via refluxing RuCl3 aqueous solution containing graphite oxide (GO), and was characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It was indicated that Ru species were present in the form of Ru(OH)4, which was uniformly distributed on the r-GO surface with average particle size around 1.3nm. The as-prepared Ru(OH)4/r-GO catalyst was used to catalyzed the glycerol oxidation in aqueous solutions of Lewis acids (including FeCl3, AlCl3, CrCl3, ZnCl2), and the effects of reaction time, temperature (120–180°C), O2 pressure (0.5–1.5MPa) and FeCl3 concentration (5–60mM) were investigated. It was demonstrated that Ru(OH)4/r-GO and FeCl3 displayed synergistic effect on the production of formic acid from glycerol oxidation in aqueous solution at 160°C, and high yields of formic acid around 60% were achieved. The possible reaction pathway was discussed. Moreover, the combination of Ru(OH)4/r-GO and FeCl3 was extended to the oxidation of carbohydrates including glucose, fructose and cellulose, and formic acid was obtained in relatively high yields. This study provides an efficient catalytic system for production of formic acid from biomass.