Electrolysis of glycerol in subcritical water

Recently, there has been a rising interest for the disposal of biorelated components that cannot be treated easily by biological processes. Because of the development of biodiesel production, the production of by-products such as crude glycerol has increased dramatically. Presently, in many biodiesel plants with low capacity, the aqueous phase containing produced/left glycerol, which is an important molecule in the context of renewable biomass resources to provide hydrogen energy and chemical intermediates, methanol and salts as by-products, is discharged as wastewater. In this manner, both environmental pollution and economical losses are created. Therefore, we developed a new hydrothermal electrolysis system, by which these organics can be converted into value added chemicals, under high-temperature and high-pressure aqueous conditions. In this study, hydrothermal electrolysis reactions of glycerol with an alkali were investigated systematically to determine the intermediate products and current efficiency. We next studied the effects of electricity loading on the molecular transformation of glycerol through the comparison of the product distribution obtained by hydrothermal electrolysis with that by hydrothermal degradation under alkaline conditions. As a gaseous product, hydrogen gas was generated, whereas lactic acid was produced as the main liquid product. The yield of lactic acid increased to 34.7% at 280 degrees C with 50 mM NaOH after 90 min reaction time. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3156006]