Ozonation of Lignin Rich Solid Fractions from Corn Stalks

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Abstract
Various kinds of solid materials containing lignin were obtained by fractionation (autohydrolysis and organosolvolysis) of corn (Zea mays) stalks. These materials were further ozonated in order to observe the behaviour of their constituent polymers, particular attention being paid to lignin, and the evolution of the water soluble reaction products during oxidation. An optimal moisture content for these materials of 60% was found, which led to the highest degree of solubilization during ozone treatment. Results indicate that lignin is the most severely affected polymer, followed by hemicelluloses and finally by cellulose. The ozonation of autohydrolyzed material involved its gradual delignification, the elimination of lignin being more easy at the beginning of the reaction than at the end. The following acids were identified by GC/MS and injection of standards in GC/FID: glycolic, oxalic, malonic, glyoxylic, glyceric, p-hydroxybenzoic and malic. In addition, p-hydroxybenzaldehyde and vanillin were also identified. During the ozonation of lignin-containing lignocellulosic materials in moistened solid state, ozone rapidly oxidized the initially generated oxyaromatics and transformed them into short chain aliphatic carboxylic acids.

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