Transformation of biomass derivatives in aqueous medium: Oxidation of ethanol from sugarcane and acetol from biodiesel glycerol catalyzed by Fe3+- H2O2

Abstract

Ethanol obtained from sugarcane is an interesting biomass feedstock that is widely used as fuel and fuel additive. Another relevant biomass feedstock is acetol obtained from glycerol, the major byproduct of biodiesel manufacturing. Ethanol and acetol were oxidized by the Fe(ClO4)3-HClO4-H2O2 system in water at 60 °C with full conversions. Ethanol (0.1 M) oxidation yielded 0.058 M formic acid (HFO) and 0.085 M acetic acid (HAC), whereas acetol (0.1 M) oxidation provided 0.059 M HFO and 0.1 M HAC. On the basis of kinetic studies, the oxidation of these feedstocks followed different mechanisms. Ethanol oxidation followed a chain mechanism induced by hydroxyl radicals generated during the catalytic decomposition of H2O2 by Fe3+. Acetol oxidation, on the other hand, followed a non-chain process in which the complex formed between acetol (as substrate) and the catalyst played a decisive role, and interaction between this complex and H2O2 was the limiting stage. The activation energies for ethanol and acetol oxidation were 24.1 and 14.8 kcal/mol, respectively.