An investigation of lignocellulosic biopolymers solubility in Protic Ionic Liquids aqueous solutions

Abstract

Lignocellulosic biomass, composed mostly by lignin, cellulose and hemicellulose, is one of the most abundant renewable resource in the world. The use of Protic Ionic Liquids (PILs) to realize the pretreatment step of lignocellulosic biomass represents a promising technique, since they have been considered as green solvents for lignin dissolution and its extraction from biomass. In this study were evaluated the ability of six PILs and their aqueous solutions to dissolve Kraft lignin at the temperature of 323.15 K. This process was also evaluated within different periods of time (1, 2, 4, 8 and 24 hours), indicating that the saturation is reached within 8 hours to the majority of the systems studied. An optical microscope was used to analyze the lignin, xylose and cellulose dissolution process, separately, in tris(2-hydroxyethylammonium) lactate, which presented the highest ability to dissolve lignin among the PILs studied. This PIL was also used to assess the temperature effect, showing that lignin dissolution was increased when higher temperatures were applied.