Effects of Pyridine and Ionic Liquid ([Bmim]Cl) Extraction on the Structure of Mongolian Bituminous Coals

Organic solvents such as pyridine and ionic liquid (IL) ([Bmim]Cl anion) have been used to extract soluble parts from Mongolian sub-bituminous and bituminous coals for the first time. The extracts and insoluble coal residues were analyzed in detail by FTIR spectroscopy. The paper highlights the types of coal that influence traditional and innovative environmentally friendly solvents-based extraction. Bituminous type of coal IL-based extraction provides more promising results, such as many types of hydrogen bonds to be revealed, a shortage of aliphatic chain, a breakage of oxygen-containing structures, and removal of minerals or oxygen-containing groups, compared to sub-bituminous coal. The traditional solvent also has the advantage of being processed easily, a room temperature procedure producing virtually similar results to IL treatment in the low-frequency region. Quantitatively one can confirm some results such as the aromatization of extracts and the aliphatic chain length shortage.