280439 Understanding the Reaction Network and Kinetics of the Hydrothermal Liquefaction of Microalgae
Hydrothermal liquefaction can convert wet algal biomass, at elevated temperatures and pressures, into an energy-dense biocrude oil without the need for dewatering the algae or extracting the lipids. Liquefaction occurs as the biomacromolecules react in and with water at elevated temperatures (e.g., 350 °C) and pressures to form smaller molecules that are closer to being in the range required for liquid fuels. Recent studies of microalgal liquefaction, examining some process variables, provide some clues about the reaction pathways, but not enough information to develop an entire reaction network. As the field progresses, quantitative reaction models based on the governing reaction network will be needed for process design and optimization. Developing such a model requires data from a thorough systematic study of the influence of all the relevant process variables on liquefaction of a single alga.
We present results from the liquefaction of Nannochloropsis sp. and the product intermediates to determine reaction pathways. From the experimental results, we determined the reaction network and constructed a model to predict the yields of the product fractions. We used first-order kinetics to describe the formation and consumption of the product fractions from liquefaction. The abundance of different compounds and the complexity of the numerous reactions necessitated the use of a global kinetic analysis to make the problem tractable. We applied this model to the liquefaction of other alga species. We will also show the fate of phosphorus in the product fractions.