(374aw) Evaluating Biomass Conversion at CO2 Supercritical Conditions in the Presence of Cosolvents

There is an increased interest in developing processes using biomass as an alternative energy source. Some examples of existing processes that convert biomass into biofuels include pyrolsis, anaerobic digestion, and thermal gasification. The resulting products may include bio-oil, synthetic gas, methane, and other gases, depending on the specific process. In addition to these products, hydrolysis of biomass (ligno-cellulose) into fermentable sugars and then ethanol is currently receiving much attention. This route provides a shift from corn based ethanol production to the exploration of ligno-cellulose ethanol processes. However, the complex nature of the ligno-cellulose structure makes it difficult to break down by regular hydrolysis techniques. The major components in ligno-cellulose include cellulose, hemi-cellulose, and lignin, which may account for this intricate structure. With the understanding of this chemistry, a number of studies are currently researching and optimizing the ligno-cellulose route to producing fermentable sugars. Although there is extensive research on biomass conversion by the processes discussed above, there is a need to evaluate other methods of breaking down the ligno-cellulose. An example of this research can incorporate supercritical carbon dioxide in the presence of co-solvents to produce sugars and various chemicals. To explore this reaction route, cellulose, hemi-cellulose, and corn stover were subjected to CO2 supercritical conditions. The reaction was conducted using a 1 liter high-pressure reactor. Additionally, to enhance the reactivity of the nonpolar CO2, various polar cosolvents were mixed into the reaction, including methanol and water. Water was added at concentrations ranging from 5 to 30 wt%. The resulting products were analyzed using NMR, HPLC, and LCMS. Based on preliminary analytical results using a GCMS for experiments at 300oC, the suggested chemical composition consisted of a mixture of sugars, organic acids and several other components. Although these results suggested that a reaction occurred, the starting biomass was not completely converted, which was evidenced by the remaining solid residue at the end of the experiment.