Influence of chloride and propionate anions on properties of corn hydrochar from hydrothermal carbonization and activation

The hydrothermal refinery is a promising thermochemical upgrading technology for high-moisture biomass and wastes. This work aimed to investigate the effect of chloride and propionate anions on hydrochar from hydrothermal carbonization of corn residues. Initial concentrations of ionic salt liquids used as a hydrothermal medium were within 0.33–1.71 mol/kg at the biomass/water weight ratio of 1/20 and 1/10 with a reaction temperature of 240C. The hydrochar obtained had low hemicellulose content and hydrogen/carbon molar ratio and high oxygen/carbon molar ratio. It was further upgraded to activated hydrochar with a maximum BET surface area of 2,144.22 m 2 g −1 and micropore volume of 1.08 cm 3 g −1 by soaking with 0.1 M phosphoric acid for 2 h followed by thermal activation at 900C for 2 h within a CO 2 environment. In addition, prediction of the removed hemicellulose from hydrochar was studied, focusing on the effect of lowering vapor pressure, molar concentration of ionic salt, and biomass concentration.