DELIGNIFICATION AND FRACTIONATION OF SUGARCANE BAGASSE WITH IONIC LIQUIDS

Abstract

The pretreatment and fractionation of sugarcane bagasse into carbohydrate-rich (CRM) and lignin-rich material (LRM) was investigated using a series of cholinium-, triethylammonium- and 1-butyl-3-methylimidazolium ionic liquids in conjunction with acetone-water-mixtures as precipitating antisolvent. Compositional analysis of the CRM showed that the pretreatment with carboxylate anion containing ILs allowed high carbohydrate recovery and moderate to high delignification, while hydrogen sulfate based ILs led to a marked reduction in both lignin and hemicellulose content. The recovery of the solubilized lignin, which could serve as a potentially valuable product stream was found highest for ILs comprising hydrogen sulfate anions. Spectroscopic characterization and comparison with alkaline, Formacell and commercial kraft lignin samples revealed differences in purity, functional group composition and syringyl-to-guaiacyl (S/G) ratio between the individual LRM fractions, giving rise to different potential applications for the derived lignins.