Chemical and Structural Properties of Carbonaceous Products Obtained by Hydrothermal Carbonization of Saccharides

A carbon-rich solid product, here denoted as hydrochar, has been synthesized by, the hydrothermal carbonization of three different saccharide (glucose, sucrose, and starch) at temperatures ranging from 170 to 240 degrees C. This material is made up of uniform spherical micrometer-sized particles that have a diameter in the 0.4-6 mu m range, which can be modulated by modifying the synthesis conditions (i.e., the concentration of the aqueous saccharide solution, the temperature of the hydrothermal treatment, the reaction time, and type of saccharide. The formation of the carbon-rich solid through the hydrothermal carbonization of saccharides is the consequence of dehydration, condensation, of polymerization and aromatization reactions. The microspheres thus obtained posess from a chemical point of view, a core-shell structure consisting of a highly aromatic nucleus (hydrophobic) and a hydrophilic shell containing a high concentration of reactive oxygen functional groups (i.e., hydroxyl/phenolic, carbonyl, or carboxylic).