Abstract:
Six Turkish lignites have been pretreated with the solutions of HCl or sodium ethanolate at room temperature or at 150°C. The volumetric swelling of the raw or pretreated lignites have been investigated by using 13 solvents at room temperature. These lignites have been subjected to Soxhlet extractions in the same solvents and in the linear alkylamines. The solubility of the samples in toluene under supercritical conditions were also tested. The effect of solvent on swelling ratio and on the extraction yields of the raw or pretreated lignites have been examined. The results have indicated that both swelling and extraction yields generally increased after the pretreatments and the increments are higher with hydrogen bonding solvents. Especially, sodium ethanolate pretreatment increases the solubility in toluene under supercritical conditions. The results suggest that solvent solubility parameter and electron donor number are effective in both swelling and solubility. A qualitative information regarding the structural characteristics of extracts was obtained by UV and NMR analysis. © 1997 Elsevier Science B.V.