(283g) Supercritical Water Reformation of Oxygenated Hydrocarbons

Decomposition of lignocellulosic biomass in near-critical and supercritical water is a fast and effective means of converting a less useful solid feedstock into a mixture of pumpable liquid products.  This process, known as liquefaction, can yield a wide array of smaller compounds (typically ranging from C₁ to C₇) from the macromolecules present in the biomass.  This type of feedstock is highly oxygenated, and as a result, the products from liquefaction are also oxygenated.  If the liquefaction products have little value on their own, they can be converted to a gaseous product via supercritical water reformation.  This process can produce synthesis gas for transportation fuel synthesis, or a high purity hydrogen/methane mixture that can be used to produce energy.  It is important to understand how the individual oxygenated functional groups present in a biomass derived feedstock affect the reformation process.  Gasification rate, product selectivity, susceptibility to coke formation, etc. can all vary depending on the oxygenated functional groups present in the feedstock.  This study attempts to elucidate these effects by examining the gasification of four oxygenated hydrocarbons in supercritical water.  1-Propanol, propionaldehyde, propionic acid, and acetone were selected as feedstocks, because they contain some of the most common oxygenated functional groups present after biomass liquefaction.  Experiments were performed in a custom built, continuous, supercritical water reformer at temperatures between 500°C and 700°C, residence times between 10 and 90 seconds, and water-to-carbon molar ratios of 8 and 15.  In addition to process effects, reaction pathways and kinetics were developed.