Energize New Mexico
National Science Foundation
We illustrate a detailed compositional characterization of hydrothermal liquefaction (HTL) oils derived from two biochemically distinct microalgae, Nannochloropsis gaditana and Chlorella sorokiniana, for a range of reaction temperatures as observed by high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The unique capability to unequivocally derive molecular formulae directly from FT-ICR MS-measured mass-to-charge ratio (for several thousand compounds in each oil) shows that lipids are completely reacted/converted for at any HTL reaction temperature above 200 oC and reveals the formation of non-lipid reaction products with increasing temperature. Specifically, lipid-rich oil is obtained at low reaction temperatures (Less than 225 degrees Celsius) for both microalgal strains. For the positive ion mode, the major lipid components in C. sorokiniana and N. gaditana HTL oils are betaine lipids and acylglycerols, respectively. Acidic species in the HTL oils (observed by the negative ion mode) are dominated by free fatty acids regardless of reaction temperature. HTL oils obtained at Hhigher-temperatures HTL oils (Greater than or equal to 225 degrees Celsius) are comprised of a variety of basic nitrogen- and oxygen-containing compounds that originated from protein and carbohydrate degradation at elevated temperatures. Similar structural features are observed for the abundant nitrogen heterocyclics between the two species with a slightly lower carbon number for C. sorokiniana, overall.
Schaub, Tanner. "Temperature-Dependent HTLComposition of Microalgal Hydrothermal Liquefaction Oils Monitored by Fourier Transform Ion Cyclotron Resonance MS." (2018). https://digitalrepository.unm.edu/energizenm/694