Demetrio Gómez

Ozonation of Lignin Rich Solid Fractions from Corn Stalks

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...

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

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.

(Liquid +Liquid) Equilibrium for Ternary Systems Containing of an Ionic Liquid, n-Hexane and an Organic Compound Involved in the Kinetic Resolution of rac-2-Pentanol

In this paper, (liquid +liquid) equilibrium (LLE) data for 12 ternary systems containing an ionic liquid + n-hexane +an organic compound involved in the racemic resolution of rac-2-pentanol (rac-2-pentanol, vinyl butyrate, rac-2-pentyl butyrate, or butyric acid) have been experimentally determined at 298.2 K and atmospheric pressure. The ionic liquids used were i. 1-ethyl-3-methylimidazolium ethylsulfate, [emim+] [EtSO4 −]; ii. 1-butyl-3–methylimidazolium tetrafluoroborate, [bmim+][BF4 −] and iii. 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [bmim+][NTf2 −]. The binodal curves and the tie line compositions of the conjugate solutions were obtained by means of refractive index (ionic liquid rich phase) and by gas cromatography (hexane rich phase) to determine their potential for selectively extracting organic compounds from an ionic liquid reaction mixture. The tie line data were correlated through the use of the Non-Random Two-Liquid (NRTL) model for statistical consistency, which provides excellent agreement with the experimental measurements. There are no literature data for the mixtures discussed in this paper.