Supercritical Water Gasification of Ethanol for Fuel Gas Production

Supercritical water gasification of dilute ethanol at the industrial scale promises a sustainable route to bio-syngas production for use in combined cycle power plants. Cost-effective bio-syngas production would reduce reliance on fossil fuels for electricity generation and reduce greenhouse gas emissions by utilizing waste biomass resources. Continuous supercritical water gasification offers high reactant conversion at short residence times without an added catalyst. The decomposition of ethanol in supercritical water is studied in a continuous reactor at 560 °C, 25 MPa, residence times between 3 and 8 s, and a constant initial ethanol concentration of 8.1 wt%. High-resolution, in-situ Raman spectroscopy facilitates identification of reaction products. Significant yields of H2, CO, and CH4 indicate the dominance of a dehydrogenation reaction pathway at studied conditions, while minor yields of ethane indicate a secondary dehydration reaction pathway. Ethylene yields are virtually nonexistent, indicating rapid hydrogenation of ethylene to ethane at these conditions. Ethanol dehydrogenation to H2, CO, and CH4 results in an overall fuel value upgrade of 84.5 kJ/mol-EtOH. Dehydration of ethanol to ethane results in an overall fuel degradation of −3.8 kJ/mol-EtOH.