| The development and improvement of biomass utilization technologies is an important research goal to reduce net emissions of greenhouse gases. Hydrothermal gasification of biomass is one such technology, which uses the unique properties of hot compressed water to convert biomass into gaseous fuels.;Hydrogen and carbon dioxide were the primary products produced, while when using 100 mM sodium carbonate solution methane also became a significant product. Four distinct mechanisms for gas production seemed to occur, depending on the sodium carbonate concentration. First of all, without the addition of sodium carbonate, very little gas was produced, furfural alcohol was the major intermediate in the liquid phase, and considerable black solid residues were formed. In the second region, increases in sodium carbonate concentration resulted in a linear increase in both hydrogen and carbon dioxide between 0 and 75 mM. Furfural alcohol was effectively suppressed in the liquid phase in this region, and the ratio of CO2 increase to H2 increase was about 1.4. In the third region, both hydrogen and carbon dioxide decreased. Finally, in the fourth region, hydrogen remained relatively constant while carbon dioxide decreased considerably to almost 0mmol at 1M sodium carbonate concentration. For each of the four levels of alkalinity, the effect of phase behaviour was studied. Without the addition of sodium carbonate, an increased headspace (higher vapour:liquid fraction) enhanced the hydrogen production significantly. While qualitatively similar effects were observed when using sodium carbonate at 50 and 100mM sodium carbonate concentration, the magnitude of the effect was dampened to a factor of 2.5 and 1.5 respectively.;Based on literature and the data herein, it is proposed that the effect of headspace fraction is related to a shift in the reaction mechanism which favours low density, free radical reactions. Most specifically, direct fragmentation to glycolaldehyde is expected to be enhanced. Given the relatively high kinetics for gasification of C1 aldehydes/acids versus C2 aldehydes/acids, this may explain the gasification efficiency increases since glycolaldehyde decomposition is thought in literature to proceed through a C1 intermediate. Furthermore, since alkali salts catalyze the Lobry-deBruyn Van Eckstein Transform, it is proposed that this may account for the reduced effect of headspace fraction under alkaline conditions.;Finally, the use of a Pt group catalyst (ruthenium) for the gasification of a real biomass was examined. The catalytic gasification of cattle manure to produce hydrogen was studied in a batch, 1.8L reactor. It was found that the combined use of sodium hydroxide and a ruthenium chloride catalyst considerably enhanced the hydrogen production. However, visible amounts of chemical intermediates still remained in the solution after gasification, thus application of the aforementioned technology under subcritical conditions with biomass still requires more research, both in terms of catalytic roles and stability, as well as further research regarding the decomposition of key intermediates in biomass gasification.;In the primary component of this work, the hydrothermal gasification of cellulose (the most globally abundant biopolymer), was investigated in a 69 mL batch reactor, which was heated by a muffle furnace. The gas products were determined using micro gas chromatography (micro-GC), and the liquid phase composition was determined by using gas chromatography with a flame ionization detector. The effects of alkali salt (sodium carbonate) concentrations, and phase behaviour on gas yield and liquid phase composition were studied in the presence of metal catalyst Pt/Al2O3. |
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