Ruthenium(III) mediated oxidation of glycerol by cerium(IV) in aqueous sulfuric acid medium – a kinetic and mechanistic study

Abstract

The micro amount of (10⁻⁶ mol dm⁻³) ruthenium(III) mediated oxidation of glycerol by cerium(IV) in an aqueous sulfuric acid medium has been studied spectrophotometrically at 25°C and I = 1.60 mol dm⁻³. The stoichiometry is 1:2, i.e. one mole of glycerol requires two moles of cerium(IV). The main oxidation products were identified as cerium (III) and glycolic aldehyde. The reaction is first order in both cerium(IV) and ruthenium(III) concentrations. The order with respect to glycerol concentration varies from first order to zero order as the glycerol concentration increases. An increase in sulfuric acid concentration decreases the reaction rate. The added sulfate and bisulfate also decreases the rate of reaction. The added product cerium(III) and glycolic aldehyde do not have any significant effect on the reaction. The active species of oxidant and catalyst are Ce(SO₄)₂ and [Ru(H₂O)₆]³⁺. The possible mechanism is proposed and reaction constants involved have been determined. The activation parameters are determined with respect to slow step of the mechanism.