EFFECT OF PRESWELLING ON SOXHLET AND SUPERCRITICAL GAS EXTRACTION OF A TURKISH LIGNITE

Preswelling of Mugla-Yatagan lignite with THF (Tetrahydrofuran) follow ed by removal of the swelling agents results in higher extract yields, probably because the solvent molecules had easier access to the expan ded pore structure of the swollen lignite. On the other hand, the yiel ds of supercritical THF extract of the same lignite sample indicated t hat during removal of the swelling agent the expanded pore structure h ad collapsed. The results show that higher extract yields might have b een obtained by the combined effect of the expanded pore structure of the swollen lignite and the solvent power of the mixed solvent ,i.e., of the mixture of swelling agent and supercritical extraction fluid.