Lignin organosolvolysis from autohydrolyzed corn (Zea mays) stalks: Ozonation of both solvolytic solid and juice

Abstract

The solubility of lignin from autohydrolyzed corn (Zea mays) stalks in different organic solvent–water mixtures and conditions was studied. The best lignin solvent was selected according to its lignin extraction capacity and its low reactivity to ozone. Both the organosolvolytic solid and juice obtained in optimal conditions, 75/25 (v/v) acetone–water mixture at 210°C for 45 min, and the autohydrolyzed material were treated with ozone, and the reaction products were determined by gas chromatography–mass spectrometry and gas chromatography–flame ionization detection. The concept of the solubility parameter (δ-value) was applied to explain the effect of the solvent-to-water ratio on lignin solubility. The δ-value of the lignin dissolved was 13.8 (cal/cm3)1/2. The δ-value of the various solvent–water mixtures was also calculated. The experimental delignification capacity of the aqueous organic solvents clearly reflects the proximity of their δ-value to that of lignin. In other words, the closer the δ-value of the aqueous organic solvent to that of lignin, the more effective it is; the hydrogen-bonding capacity of the solvent–water mixtures was also taken into account. The following acids were identified during ozonation: glycolic, oxalic, malonic, glyoxylic, butanedioic, malic, p-hydroxybenzoic, vanillic, and syringic. In addition, syringaldehyde, vanillin, p-hydroxybenzaldehyde, and hydroquinone were identified. Ozonation of theorganosolvolytic juice led to the formation of the oxyaromatic compounds, which were destroyed during treatment. This destruction was accompanied by the generation of aliphatic acids. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1867–1876, 1998