Products and Kinetics for Isothermal Hydrothermal Liquefaction of Soy Protein Concentrate

Soy protein concentrate was hydrothermally treated at isothermal temperatures of 200, 250, 300, and 350 °C for times up to 60 min to produce a crude bio-oil. Additional product fractions included water-soluble products, gases, and residual solids. We report herein the conversion of protein and gravimetric yields of the different product fractions. The biocrude yield generally increased with both time and temperature as did the yield of gaseous products. The highest biocrude yield was 34%, produced from liquefaction at 350 °C for 60 min. Chemical and physical characterization of the biocrude revealed how its composition and boiling point range changed with reaction time. Finally, we report a reaction network and the parameters for a phenomenological kinetics model that captures the influence of time and temperature on the yields of gas, solid, biocrude, and aqueous-phase products from isothermal hydrothermal liquefaction (HTL) of soy protein concentrate. The reaction network comprised a sole primary path, which converted soy protein concentrate to aqueous-phase products. Secondary reactions of these water-soluble compounds produced biocrude and gases. There was no direct path to biocrude formation from the biomass feedstock.