Sugar, hydrochar and bio-oil production by sequential hydrothermal processing of corn cob

Hydrothermal liquefaction (HTL) is an alternative process for biomass conversion with promising outcomes and environmentally-friendly prospects. However, a gap in the intermediate bioproducts was found in the hydrolysis step of HTL after a careful investigation of the current state-of-the-art. This study investigated two routes of the hydrothermal conversion of corn cob through HTL and sequential processing, i.e. subcritical water hydrolysis (SWH) + HTL. The influence of SWH (230-260 degrees C) and HTL temperatures (300-350 degrees C), and volumetric flow rate (5-10 ml min-1) were evaluated. GC-MS and FTIR analysis were performed for bio-oil characterization. Results showed that lower SWH temperatures favored glucose and furfural production, while higher temperature favored xylose and hydroxymethylfurfural (HMF). Bio-oil produced by the sequential processing exhibited a high concentration of nitrogenous and oxygenated compounds. Hydrochar produced in both routes exhibited a similar higher heating value and elemental composition, although FTIR analysis revealed different functional groups.