Oxidative depolymerization of kraft lignin assisted by potassium tert-butoxide and its effect on color and UV absorption

Abstract

A chemically mild methodology was demonstrated to obtain decomposed lignin products via oxidative depolymerization. We effectively produced light-colored lignin materials with low molecular weight and narrow molecular weight distribution by simple agitation at ambient temperature and pressure in the presence of potassium tert-butoxide and gaseous oxygen. This oxidative depolymerization dissociated various lignin bonding structures and oxidized aliphatic hydroxyl groups of lignin, expanding conjugated system within the depolymerized lignin molecules. This chemical transformation resulted in the generation of effective chromophoric moieties to enhance the UV absorption property of the resulting depolymerized products, which showed a significant improvement in the sun protection capability.