(621cr) Characteristics of Ash-Free Coals Recovered By Vacuum Distillation and Dilution Precipitation from Solvent-Extracted Solution

In this study, the SEM, BET, FTIR and 13C NMR results of ash-free coal (AFC) samples obtained from solvent-extracted solution by vacuum distillation (VD) and dilution precipitation (DP), are compared.

In the solvent extraction process for making AFC, Kideco coal (Indonesian sub-bituminous coal) is mixed with non-polar 1-methylnaphthalene (1-MN) solvent. By stirring the coal-solvent mixture at high temperature for a certain period, a soluble part of organics in the coal is extracted. The AFC is recovered from the extracted solution using VD and DP. When the solution is exposed to heat under reduced pressure, the solvent evaporates and therefore the AFC is recovered in VD process. On the other hand, the AFC is recovered by adding a diluent to the extracted solution at room temperature during DP process. Some of the coal components dissolved in the solvent are precipitated by the addition of hexane diluent as a result of the reduced solubility.

According to the analyses, the surface of the VD-treated AFC (VD-AFC) is relatively smooth showing small surface area, while that of the DP-treated AFC (DP-AFC) is rough. In addition, the DP-AFC contains more aromatic functional groups than the VD-AFC.