(153c) Strategies for Changing the Energy Content and Achieving C-C Coupling In Biomass-Derived Oxygenated Hydrocarbons

The transportation sector of society requires fuels that burn cleanly and that have high energy densities for efficient storage at ambient conditions, criteria that are currently best fulfilled by petroleum, a non-renewable resource in diminishing supply. Furthermore, energy production from fossil fuels leads to emission of CO₂, a greenhouse gas that contributes to global warming. These issues associated with the continued combustion of petroleum by the transportation sector would be ameliorated by producing clean burning liquid fuels from renewable biomass resources. In this respect, the amount of biomass that could be grown globally on a sustainable basis is comparable to the annual world-wide consumption of energy by the transportation sector.

The predominate class of compounds in ligno-cellulosic biomass consists of carbohydrates, having a C:O stoichiometry of 1:1, giving them low volatility and high water solubility, properties that are undesirable for use as transportation fuels. One strategy for converting these sugars to liquid transportation fuels is to remove most of the oxygen atoms, producing such mono-oxygenated fuels as ethanol, butanol, or dimethylfuran. Another attractive approach is to produce higher molecular weight alkanes that more closely resemble current transportation fuels derived from petroleum (e.g., C₅-C₁₂ for gasoline, C₉-C₁₆ for jet fuel, and C₁₀-C₂₀ for diesel applications), which could be processed and distributed by existing petrochemical technologies and infrastructure, respectively, and which could be used as fuels in existing transportation vehicles.

In this talk, we will explore strategies is to convert biomass-derived sugars to non-oxygenated liquid fuels. We will outline ideas for removal of oxygen from sugars in combination with isomerization steps to form branched hydrocarbons for gasoline, and we will explore approaches to achieve C-C coupling reactions to increase the molecular weight for diesel and jet fuels. We hope that this discussion may identify promising directions for future work involving the combination of theoretical and experimental studies.