SOLUBILIZATION OF LIGNITE WITH SUPERACID (TRIFLUOROMETHANESULFONIC ACID) ISOPENTANE AT THE MILD CONDITIONS

Trifluoromethanesulfonic acid (TFMS) was found to solubilize lignite and subbituminous coal in the presence of isopentane at temperature as low as 150 degrees C for three hours under autogeneous pressure of 6.1-6.9 MPa without hydrogen. Yallourn coal gave 63 wt% pyridine soluble fraction after reaction and required more TFMS to achieve the maximum solubility, but the treated Taiheiyo coal could be solubilized in pyridine to the extent of 90% by the same reaction with TFMS, Acid-catalyzed depolymerization with TFMS would be inadequate, because the lignite has many oxygen containing functional groups, The average molecular weight of benzene soluble and THF soluble fraction from the treated Yallourn coal decreased, and their aromaticity increased with the increase of TFMS concentration. In contrast, average molecular weight of soluble fraction from the treated Taiheiyo coal was unchanged, and their aromaticity decreased with the increase of TFMS concentration. It is suggested that TFMS plays an important role in depolymerization of the coal molecules for Yallourn coal solubilization, and accelerates alkylation and hydrogenation in the Taiheiyo coal solubilization. Oxygen functional groups would lower the activity of TFMS as acid catalyst by interaction, leading to the formation of water from the cleavage of aliphatic ether groups and the dehydration of phenoxy OH groups.