Beneficiation of Indian coals using Ionic Liquids

The interaction between five different Ionic Liquids (ILs) and four Indian coals from the mineral rich eastern part of the country were carried out to identify its dissolution and swelling characteristics. Five ILs consisting of different cations namely: 1-butyl-3-methylimidazolium hexaflurophosphate [BMIM][PF6], 1-butyl-1-methylpyrrolidinium methyl carbonate [BMPYR][CH3CO3], 1-butyl-4-methylpyridinium tetrafluoroborate [BMPY][BF4], tributylmethylphosponium methylsulfate [MTBP][MeSO4] and tributylmethylammonium methylsulfate [TMA][MeSO4] were used. Morphological studies before and after heating the coals in ILs were carried out to determine the extent of swelling and fragmentation of coal particles. Using Fourier Transfer Infrared Spectroscopy (FTIR), the functional groups of ILs in untreated and ILs pretreated coal were identified. An overall 47.6%, 55.6% and 68.1% reduction in the peak area of hydroxyl group (phenolic and free hydroxyl radical) was observed for the ILs [BMIM][PF6], [BMPY][BF4] and [BMPYR][CH3CO3] for the bituminous coal respectively. From the proximate analysis, the increase in fixed carbon content (on weight basis) was found to be 1/3rd as compared to the raw coal. Among the ILs studied, [BMPYR][CH3CO3] was found to. have a highest swelling ratio of 1.5. This was also confirmed from the FTIR spectra and the measurement of swelling ratio. Following a similar trend, the morphological studies also concluded that the IL [BMPYR][CH3CO3] was most effective in disintegrating the coal particles to micrometer size. Also this IL gave a total yield extraction of 27.41% (on daf basis) for coal 2 (bituminous) and 35.13% (on daf basis) for coal 4 (lignite). (C) 2016 Elsevier B.V. All rights reserved.