Effects of Potassium Phosphates and Other Additives on Biocrude Production and Composition from Hydrothermal Liquefaction of Pectin and Chitin

We determined the influence of added potassium phosphates, Na₂CO₃, and KOH on the product distribution and characteristics of the biocrude from the hydrothermal liquefaction (HTL) of pectin and chitin. Added K₃PO₄and KOH provided a significant positive effect (30-70% increase) on the biocrude yields from HTL of both polysaccharides. These basic conditions resulted in a higher biocrude yield, whereas acidic conditions (added KH₂PO₄) reduced the yields of biocrude relative to the control experiment. HTL with basic additives increased both the H/C and O/C atomic ratios relative to the control experiments, and the higher O/C ratios for chitin HTL were sufficient to reduce the heating values of these biocrudes. Addition of K₃PO₄led to a larger fraction of low-boiling compounds being present in the biocrude from HTL of chitin, which is a desirable outcome. Taken collectively, the results show that additives can be used to increase biocrude yields and engineer HTL outcomes, to an extent, for valorization of these abundant polysaccharide renewable resources.