Supercritical Dioxane Extraction of Spruce Wood and of Dioxane-Lignin and Comparison of the Extracts with the Pyrolysis Products

Abstract

Samples of spruce wood and of dioxane-lignin prepared from spruce wood were subjected to supercritical dioxane extraction at 330 C. To compare the yield and the nature of the compounds present in distillate obtained upon pyrolysis to those of supercritical gas extract, the same samples were pyrolysed at 340°C. The extracts and distillates were separated into three fractions by solvent fractionation using hexane and benzene successively. The simpler compounds were identified by GC/MS and the yields of phenols were compared. More complex compounds insoluble both in hexane and benzene have been characterized by ¹H NMR spectrometry. It was found that the supercritical extracts and the pyrolysis distillates contained similar compounds; however, demethoxylation during pyrolysis was extensive compared to supercritical gas extraction which occurred under rather mild conditions.