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Catalytic Hydrogenation Reactions For The Production Of Renewable Fuels From Biomass

Depletion of fossil fuel reserves along with growing environmental concerns has shifted focus towards renewable energy sources for liquid fuels production, such as biofuels. Most biofuels, like ethanol, are single-component fuels that cannot meet today's engine specifications unless they are blended with petroleum feedstocks. Current transportation infrastructure uses petroleum fuels that are mixtures of compounds. Therefore, it is important to be able to produce multi-component fuels in a cost effective way, from renewable resources. Aqueous-phase hydrogenation reactions are crucial in converting biomass-derived molecules into liquid fuels and chemicals. It is possible to produce multi-component fuels through the hydrogenation of bio-oils in the aqueous phase. One of the hardest functionalities to be hydrogenated in bio-oils is the carboxylic acids. Our findings on acetic acid hydrogenation studies over monometallic catalysts will be discussed combined with insight learned from DFT calculations. Ruthenium has been shown to be the most active and selective catalyst towards ethanol formation. Acetyl species appears to be a key component as its formation is the rate-determining step for almost all catalysts. Another way of making multi-component fuels is by the liquid-phase processing of the hemicellulose portion of biomass. It will be shown that hemicellulose-derived aqueous feedstocks can be converted into a petroleum feedstock that can readily be processed in existing petroleum refineries to make a variety of fuels. Furfural is produced in high yields from the dehydration of hemicellulose-derived sugar streams. The aldol condensation of furfural with acetone gives highly conjugated C 13 compounds along with some polymeric adducts. In the presence of supported metal catalyst these compounds undergo hydrogenation, and at the same time, form heavy cyclic molecules via Diels-Alder reactions. Through hydrodeoxygenation and isomerization over bifunctional catalysts these molecules produce refinery feedstocks, or more specifically, fluid catalytic cracker cycle oil substitutes, having carbon numbers up to C 31 . This integrated catalytic process can be tuned to adjust the yield of the hydrocarbon products thereby selectively producing jet and diesel fuel range compounds or a heavier petroleum refinery feedstock. This study demonstrates that biomass can produce mixtures of components that can fit seamlessly into petroleum refinery infrastructure.
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