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.Reaction behavior of complex molecules in supercritical water can be inferred through the reaction pathways of model compounds in supercritical water. Methanol, ethanol, and isopropyl alcohol are gasified in a continuous reactor at temperatures between 500 and 560 degrees C and for residence times between 3 and 8 s. In-line Raman spectroscopy is used to rapidly identify and quantify reaction products. The results suggest the dominance of chain-branching, free radical reaction mechanisms that are responsible for decomposing primary alcohols in the supercritical water environment. The presence of a catalytic surface is proposed to be highly significant for initiating radical reactions. Global reaction pathways are proposed, and mechanisms for free radical reaction initiation, propagation, and termination are discussed in light of these and previously published experimental results.