Study of Colombian coals using photoacoustic Fourier transform infrared spectroscopy

Five of the most important Colombian coals were studied using Photoacoustic Fourier transform infrared (PA-FTIR) spectroscopy. The PA-FTIR spectra were used to obtain structural parameters and to determine the analytical potential of this technique. The molecular structural parameters, CH2/CH3, fa, Hal/Har, and (R/C)u were correlated with fixed carbon contained in the samples to determine aliphatic hydrogen, Hal, and the aromatic hydrogen, Har in coals studied here. These parameters enabled the determination of aromaticity, fa, which was found to be between 0.66 and 0.98. The aliphatic and aromatic regions were considered between 3005–2760 cm−1 and 912–670 cm−1, respectively. Finally, using the molecular structural parameters, the grade of maturation (rank) of coal samples studied was determined.

Research Highlights
► The PA-FTIR spectroscopy method has been used successfully for determining structural parameters of Colombian coals.
► The structural parameters, CH2/CH3, fa, Hal/Har were correlated with fixed carbon contained.
► It is possible determine the rank of coal studied here, using the structural parameters fa and (R/C)u.