| Rapidly dwindling fossil fuel reserves and ever-increasing energy demands drive the search for new sources of energy, especially for the transportation sector. Among the technical hurdles facing the development of these alternative fuels is the presence of elevated levels of nitrogen and oxygen in biomass-derived crude oils, which introduce detrimental properties to the fuel. Catalytic hydrotreatment is the currently preferred method to remove these polar species from bio-crude. However, the efficiency of the hydrotreatment process is highly dependent on the chemical nature of the bio-oil. Therefore, a complete molecular characterization of the bio-oil is crucial to devise and monitor appropriate upgrading strategies and to improve the efficiency of the upgrading processes.;Electrospray ionization coupled with FT-ICR MS selectively ionizes thousands of polar constituents in the complex bio-oils without prior chromatographic fractionation and provides unmatched compositional details for individual molecules for identification of compound class (heteroatom content), type (number of rings plus double bonds or Double Bond Equivalents = DBE) and carbon number (degree of alkylation).;A detailed compositional description of bio-crude oil and aqueous by-product from hydrothermal liquefaction of microalga, Nannochloropsis salina is illustrated in chapter two. Aromatic nitrogen compounds and free fatty acids are the predominant species observed in the bio-oil and the aqueous fraction. Residual organics in the aqueous fraction comprise slightly lower DBE and carbon number compared to the HTL bio-oil. Heteroatom content and the functionality distribution illustrated for the HTL bio-oil highlight the need for better understanding of the bio-crude chemistries for HTL process optimization and upgrading strategy development.;Chapter three explores the influence of reaction temperature on the chemical composition of the hydrothermal liquefaction bio-oils derived from two biochemically distinct microalgal strains, Nannochloropsis gaditana and Chlorella sorokiniana. A lipid-rich biooil is obtained at low reaction temperatures, whereas the bio-oil obtained at high temperature is mainly composed of protein and carbohydrate derived materials. Double bond equivalents and carbon number distributions reported for various nitrogen- and oxygen- containing compounds provide a measure of aromaticity and a degree of alkylation for the observed compounds.;In chapter four, hydrothermal liquefaction bio-oil and hydrotreated product derived from pine tree farm waste are characterized by ESI FT-ICR MS to assess lignocellulosic materials as a potential biofuel feedstock via this processing methodology. Pyrolysis bio-oil from the same feedstock is characterized for direct comparison to the HTL bio-oil. This study also identifies the hydrotreatment-resistant compounds in the HTL bio-oil as well as various heteroatomic species that are completely and partially removed by hydrotreatment.;Chapter five includes results from two additional studies performed with our collaborators at Pacific Northwest National Laboratory and Universal Oil Products, as well as a description of an ongoing project designed to address the issues related to the microalgal cultivation. Section 5.1 provides data from a parametric study that evaluates the efficiency of the hydrotreatment under two different processing conditions. Section 5.2 describes HTL aqueous phase recycling effects on the properties of the HTL bio-crude from corn stover and pine. |
