The Formation of Char, Gaseous and Liquid Products during Lignin Carbonization in Super‐ and Subcritical Solvents

The carbonization of lignin was performed using different solvents including ethanol, water and 50 vol % ethanol/water mixture under super‐ and subcritical conditions at 260 °C. The chars from lignin carbonization in supercritical ethanol provided low O/C ratio (0.09‐0.14) and considerable content of surface oxygen‐containing group (0.18‐0.32 mmol g −1 ). Supercritical ethanol substantially participated in lignin carbonization, while the activity of ethanol was also influenced by the chemical structure of lignin. High carbon recovery of 103.8 % for chars was obtained from dealkaline lignin with guaiacyl characteristics, accompained with the production of H 2 and high valuable C 6 ‐C 10 esters.