Abstract
This chapter describes the use of supercritical carbon dioxide (scCO(2)) and scCO(2)-expanded liquids, as reaction media for the oxidative fragmentation of lignin using hydrogen peroxide as the oxidant. Kraft Indulin Lignin (KIL) is oxidized with peroxide in neat scCO(2) but more extensive oxidation occurs in scCO(2)-expanded liquids, selectively inducing the formation of large amounts of carboxylic acids via the elimination of phenolic moieties. Interestingly, the weight average molecular weight of the lignin oxidized in neat scCO(2) decreased while it increased in scCO(2)-expanded liquid, most likely via the preferential elimination of the lower molecular weight fragments. Notably, all these significant oxidative transformations occur in total absence of alkali, which is essential when such reactions occur in aqueous media.