Advances in 5-(Hydroxymethyl)Furfural Production From Cellulose Via CO2-Catalysis
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The global economy must make a radical shift to lower carbon emissions to avert large-scale impacts from climate change. Fuels derived from widely available biomass such as macroalgae, have the potential to limit the CO2 impact of transportation by reducing the reliance on fossil fuels. 5-(Hydroxymethyl)furfural (HMF) is a jet fuel precursor that can be produced from carbohydrates such as those available in macroalgal biomass. However, researchers pursuing the production of HMF from inexpensive carbohydrates have struggled to achieve high yields under economically sustainable conditions due to low yields and the formation of side-products such as organic acids and humic oligomers. Current methods for HMF preparation typically utilize reagents, reaction conditions and purification protocols that are not suitable for commercial biofuel production. In 2010, high-pressure CO2 was identified as a potential catalyst for HMF production. This thesis describes work done to improve the understanding of CO2-catalyzed HMF production. An initial study examined the effect of temperature, pressure and salt selection on CO2-catalyzed HMF production from glucose. It was found that an initial concentration of 1% glucose (in pentanol containing 10 mL of 10% CaCl2 solution) reacted at 200 oC under a pressure of 7 MPa of CO2 could produce HMF in a 64% yield. These same conditions were then applied to starch, xylan, and cellulose, and yields of 55%, 51%, and 22%, respectively, were obtained. Efforts were then made to improve HMF yield from cellulose by improving the reaction conditions and it was found that application of a temperature of 200 oC over 4 hours of reaction time gave the best yields (43% total furans), although the relationship between CO2 pressure and HMF production appears to be weaker than initially anticipated. Exploratory work was also done assessing the use of novel 5-HMF production methods, such as recycle-experiments and simultaneous production of the acetone adduct. Overall, this thesis work offers evidence that CO2-catalyzed production of 5-HMF and furfural from cellulose is possible, and assists in determining the best conditions for preforming this conversion.