2025 AIChE Annual Meeting

(584db) Supercritical Hydrothermal Liquefaction of Waste Woody Biomass

Authors

William J. DeSisto, University of Maine
Clayton Wheeler, University of Maine
Sampath Gunukula, University of Maine
This study aims to improve the quality of biocrude produced from the hydrothermal liquefaction (HTL) of waste woody biomass and enhance its potential as a feedstock for making sustainable aviation fuel. HTL is conducted at temperatures of 375 °C and pressures exceeding 3400 psi to depolymerize woody biomass under supercritical water conditions. HTL reactions are performed in both batch and continuous modes to examine the effect of heating and cooling rates on the depolymerization of woody biomass. A particle residence time of 15 minutes is selected for the batch HTL reactions once the desired temperature is reached. The same residence time is applied for the continuous HTL reactor. Additionally, we compare how varying process parameters, such as the reactor's initial pressure, influence the yield, composition, and quality of the biocrude produced. The HTL liquor is separated from the char via filtration. The liquor then undergoes solvent extraction to separate the organic phase from the aqueous phase. Ethyl acetate is used as the solvent due to its low solubility in water and relatively low boiling point compared to water. Various analytical techniques are employed to determine the components of the biocrude. Fourier Transform Infrared (FTIR) Spectroscopy is used to identify functional groups, while conventional gas chromatography-mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography (GC×GC) are used to analyze the composition of the biocrude and the aqueous phase. GC×GC offers advantages over conventional GC-MS due to its ability to resolve complex mixtures and distinguish compounds with similar boiling points. The GC-MS analysis showed that the HTL oil contained phenols, benzenediols, cycloketones, and ethers. Although these oxygenated molecules increase the biocrude's energy density, they also make it more unstable and chemically reactive, indicating the need for further upgrading.