Gasification Pathways and Reaction Mechanisms of Primary Alcohols in Supercritical Water

Supercritical water gasification is a promising waste-to-energy technology with the ability to convert aqueous and/or heterogeneous organic feedstocks to high-value gaseous products, e.g., green hydrogen. Reaction behavior of complex molecules in supercritical water can be inferred through knowledge of the reaction pathways of model compounds in supercritical water. In this study methanol, ethanol, and isopropyl alcohol are gasified in a continuous supercritical water reactor at temperatures between 500 and 560 °C, and for residence times between 3 and 8 s. In situ Raman spectroscopy is used to rapidly identify and quantify reaction products. The experiments confirm the dominance of chain-branching, free radical reaction mechanisms that are responsible for decomposing primary alcohols in the supercritical water environment. Reaction pathways and mechanisms for three alcohols are proposed, conversion metrics are presented, and results are compared with known reaction mechanisms for methanol and ethanol oxidation.