Fractionation methods of eucalyptus kraft lignin for application in biorefinery

Abstract Kraft lignin has high dispersity and low reactivity. This study aimed to obtain more homogeneous and modified chemical fractions from the application of fractionation methods using organic solvents and acid precipitation. Organic solvents used were ethyl acetate, ethanol, methanol and acetone. The pHs tested were 9, 7, 5, 3 and 1, by adding hydrochloric acid. The fractions were characterized of acid-soluble and insoluble lignin, carbohydrates, ashes, elemental analysis and by Py-GC/MS. All fractions obtained in both fractionation methods showed higher carbon contents, higher purity and lower S/G ratio than the corresponding initial materials, characteristics that are very favorable for the application in biorefinery. Acetone-soluble (sequential) and pH 1 (one-step) precipitated fractions are the most promising for carbon fiber production. Fractions soluble in ethyl acetate (one-step) and insoluble at pH 3 and 1 (sequential) appear to be the most appropriate for applications that require good oxidative properties. The fractions soluble in ethanol (one-step), methanol (one-step), acetone (one-step) and precipitated at pH 9 (one-step) and pH 5 (sequential) are the ones that allow better chemical substitution in obtaining bioproducts. Fractions soluble in ethanol (sequential) and precipitated at pHs 5 and 1 (sequential) are not of commercial interest due to their low yield.