Hydrothermal Liquefaction of Microalgae in a Continuous Stirred-Tank Reactor

The microalgae species <i>Nannochloropsis gaditana</i> (<i>N. gaditana</i>, marine) and <i>Scenedesmus almeriensis</i> (<i>S. almeriensis</i>, freshwater) were subjected to hydrothermal liquefaction (HTL; 350 °C; residence time of 15 min) in a continuous stirred-tank reactor (190 mL) at microalgae loadings of 9.1 and 18.2 wt % in the feed. The results indicate that the high loading of biomass in the feed promotes the formation of biocrude oil, with a maximum yield of 54.8 ± 3.4 wt % for <i>N. gaditana</i>. A similar type of biocrude was obtained with both species. Its nitrogen and carbon contents increased at the high biomass loading, as well as the higher heating value. The HTL product yields varied from those reported for batch experiments carried out at the same reaction conditions. Most of the nutrients initially present in the feedstock were recovered to some extent in bioavailable forms in the aqueous phase, especially in the case of <i>N. gaditana</i>

Modeling the Lignin Degradation Kinetics in an Ethanol/Formic Acid Solvolysis Approach. Part 1. Kinetic Model Development

A formal kinetic model describing the main reaction pathways yielding demethoxylated monomeric phenols from wheat straw lignin in a hydrogen-enriched solvolysis reaction system using ethanol as cosolvent has been developed. The simplified lump model combines both a detailed focus on the deoxygenation reactions at molecular level as well as the reactions of global bulk lumps. The results show that depolymerization of lignin structures is quickly achieved and that deoxygenation reactions largely follow a main route pathway via intermediate methoxyphenols and catechols to give stable phenols in the liquid phase. Observed ethyl group substituents of phenolics are seen to originate from either alkylation reactions of the intermediates, or directly from the depolymerizing structures. A high correlation between primary 4-ethylphenol products and <i>para</i>-coumaryl units in the examined lignin suggests that main reaction pathways are strongly dependent on the type of plant lignin used