Hydrothermal Liquefaction of Softwood: Selective Chemical Production Under Oxidative Conditions

This work was conducted to determine the effect of oxygen on hydrothermal liquefaction of softwood for the production of valuable chemicals. Softwood was subjected to liquefaction in the presence and absence of either 1.6 g/L sodium carbonate or 5 bar oxygen gas. The oxygen supplementation diverted sugars from dehydration toward oxidation resulting in 4-fold elevated yields of organic acids. Dissolved sugars and furans showed maxima in narrow temperature regions of 170–190 and 210–230 °C while the yields (weight percentage based on dry wood) of organic acids, phenolic substances, and bio-oil reached their respective maxima of 10.4%, 3.5%, and 7.4% at 230–270 °C. These results of oxidative hydrothermal liquefaction advance sustainable production of chemicals from renewable lignocellulose.