Accelerated solvent extraction of lignin from Aleurites moluccana (Candlenut) nutshells.

Lignin from candlenut shells was isolated using an ethanol-water accelerated solvent extraction method. Yields (based on Klason lignin) increased from about 14 to 33% as temperature increased from 100 to 195 °C and were also influenced by the amount of aqueous acid used to precipitate lignin from the extraction liquor. These yields were higher than could be obtained using a conventional dioxane-water acidolysis method. The resulting lignin was characterized by IR, 31P NMR, and 1H-13C HMQC NMR spectroscopic techniques. The lignin contained predominantly guaiacyl units, and both the total hydroxyl group content and phenolic hydroxyl group content were high.