Fractionation of Japanese cedar and its characterization as treated by supercritical water

Abstract

Supercritical water treatment (380°C/100 MPa/8 s) was applied to extractive-free sapwood portion of Japanese cedar (Cryptomeria japonica) and the fractionated products were comparatively characterized, for water-soluble portion and water-insoluble portion composed of methanol-soluble portion and methanol-insoluble residue. As a result, the water-soluble portion was determined to be composed of carbohydrate-derived products such as organic acids, sugar-decomposed products, lignin-derived products, etc. The methanol-soluble portion was, on the other hand, mainly composed of lignin-derived products, whereby it consisted of solely guaiacyl-type lignin, representing the nature of softwood. The methanol-insoluble residue was also mainly composed of lignin to be 92.0% in its content. Moreover, the phenolic hydroxyl content determined by aminolysis method was 36.3 PhOH/100 C9. Furthermore, an alkaline nitrobenzene oxidation analysis indicated that, the methanol-insoluble residue was less in oxidation products compared to untreated sample. These lines of evidence suggest that methanol-insoluble residue is composed of lignin with more condensed-type of linkages with high phenolic hydroxyl groups. In addition, the water-soluble portion could be utilized for organic acid production, whereas the methanol-soluble portion and its insoluble residue for phenolic chemical production. © Springer 2011.