Oualitative and quantitative ATR-FTIR analysis and its application to coal char of different ranks

This paper analyzes the coal to char stages of char formation of six coals of different ranks by using Fourier transform infrared coupled with attenuated total reflectance (ATR-FTIR). The chars were obtained by coal pyrolysis carried out at temperature range of 450–700°C. The data obtained shows the pragmatic disappearance of the aliphatic hydrogen content with increasing char formation temperature. Numerical evaluation of the spectra enabled the determination of aromaticity, fa. The aromaticity was found to be between 0.66–0.79 for lignite, 0.75–0.90 for sub-bituminous, 0.84–1.00 for low volatile bituminous, 0.83–1.00 for high volatile bituminous, 0.94–1.00 for semi-anthracite, and 0.97–1.00 for anthracite respectively. With increasing rank of coal samples, spectra exhibit rising aromaticity and enhanced condensation of aromatic rings, whereas the aliphatic chain lengths decrease.