A COMPARATIVE-STUDY OF HARD AND SOFTWOOD LIGNINS ALTERATIONS DURING TREATMENT IN DIOXANE-WATER-HCL AGENT

The objective of the presented contribution was a study of the lignin alterations occurring in the process of the acidolytic delignification of chosen representatives of soft and hard wood species (maple and sp ruce) in dioxane-water-HCl mixture. All lignin samples were characteri sed by yield or recovery, molecular weights, as well as by GLC data of corresponding nitrobenzene oxidation products. In order to obtain mor e information about condensation and degradative reactions of lignin u nder conditions of acidolytic treatment a simulation of the process of lignin isolation was performed, too. Samples of dioxane lignins obtai ned after 90 min. of isolation at 82.5 and 98 degrees C were therefore recooked during 360 min. under identical conditions as applied in the lignin isolations. Concentrations of lignin in the reaction mixture w ere 1 and 10% thus approximately corresponding the lignin concentratio n inside and outside of the wood meal during the lignin isolation. The obtained experimental data point out the course of both degradative a nd condensation reactions. Maple wood lignin undergo deeper degradatio n than those of spruce under the same reaction conditions. The decreas ed yields of lignin oxidation products with the time of acidolytic tre atment and after recooking hint at the formation of new linkages among building units of lignin thus modifying its macromolecules. The inten sity of occurring alterations of examined lignins is not only dependen t of time and temperature, but also of the concentration of lignin.