(136e) Electrochemical Conversion of Glycerol

Biodiesel consumption has increased at a compounded annual growth rate of 180%, expanding from 91 million gallons in 2005 to 412 million gallons in 2008 [1]. This dramatic growth is fueled by regulatory incentives, increased demand for fleet use, and the desire to achieve energy independence through use of a renewable source. The production of glycerol (C3H8O3), the principal by-product of biodiesel and oleochemical production, is expected to increase significantly with the expansion of biofuels. Although glycerol is used in food and personal care products, supply currently outstrips demand so that up to 350,000 tons of glycerol is incinerated in the US annually [2]. The electrolytic conversion of glycerol into value added products has been reported [3]. This process was carried out at low temperatures using Pt/C electrocatalysts and resulted in a production of aldehydes and acids depending on the applied potential. Research described in this paper explored the use of an electrochemical reactor that resembled a proton exchange membrane (PEM) fuel cell for the oxidation of glycerol. Noble metals based anode and cathode (1 mg/cm2 loading) were used with Nafion® 117 to produce the membrane electrode assemblies (5 cm2). The activities and selectivities were evaluated at 50 °C and varying potentials with humidified N2 (100 mL/min) flowing to the cathode and glycerol (100 mL/min) flowing to the anode. The products were characterized using a gas chromatograph equipped with flame ionization and mass spectrometer detectors. The electrocatalysts were characterized using x-ray diffraction and BET surface area analysis. The selectivities and conversion varied significantly with the applied potential as shown in Figure 1, with high glyceraldehyde production rates at higher potentials. The conversions and reaction rates increased with potential. Those results provide key information to study the mechanism of electrochemical oxidation of glycerol in an electrochemical reactor and to optimize experimental conditions to achieve high selectivity. References [1] Renewable Energy Consumption and Electricity Preliminary Statistics 2008: Energy Information Administration, DOE/EIA (2009) [2] Zheng Y et al. Commodity Chemicals Derived from Glycerol, an Important Biorefinery Feedstock. Chem. Rev. (2008), 108, 5253?5277 [3] Roquet et al. Kinetics and Mechanisms of the Electrocatalytic Oxidation of Glycerol as Investigated by Chromatographic Analysis of the Reaction-Products - Potential and pH Effects. Electrochim Acta (1994) vol. 39 (16), 2387-2394