Partial Oxidation of Ethanol in Supercritical Water

Ethanol is partially oxidized in a continuous supercritical water reactor at temperatures from 500 to 530 °C, constant pressure of 25 MPa, initial ethanol concentration of 5 wt %, residence times of 3–8 s, and oxidant-to-fuel stoichiometric equivalence ratios of 5, 7.5, and 10%. The experimental conditions are selected to study the regime where ethanol oxidation happens rapidly but below the temperature necessary to initiate hydrolysis reactions. The reactions and interactions of intermediate species can be analyzed, leveraging previous experimental results and the existing body of literature on ethanol hydrolysis, pyrolysis, and oxidation. Higher oxidant concentration increases ethanol destruction and gasification efficiency, although significant coke/char buildup is qualitatively observed within the reactor. Product yields from the experiments are used to infer significant reaction mechanisms, and a pathway is postulated for the counterintuitive formation of char under the studied conditions.