A multi-tool structural change investigation of Indian vitrinite rich bituminous coal due to CS2/NMP interaction

Solvents are important constituent in the coal liquefaction process as they act as hydrogen donors and serve as hydrogen shuttles between hydrogen and coal. A mixture of carbon disulfide (CS2) and N- methyl-2-pyrrolidinone (NMP) (1:1, v/v) was used as a solvent for a study of an Indian coal that was kept for swelling. The study of coal swelling provides valuable information, such as, determining the highest energy bond that can be broken by a particular solvent or by a mixture of solvents. It can be concluded from the results that maximum swelling and extraction yield are achieved by a CS2/NMP mixed solvent. The structure change of coal before and after its interaction with the solvent was also studied using techniques such as Fourier-transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), and X-ray powder diffraction (XRD). MR indicated that the mixed solvent caused a decrease in the solvent viscosity, enabling the solvent to penetrate more quickly into the coal structure. XRD structural parameters concluded a decrease in aromatidty and stacking height and an increase in the interplanar spacing of raw coal after the swelling process. This was due to a decrease in the crystalline carbon along with an increase in amorphous carbon. XRD results indicated that the four parallelogram-shaped aromatic sheets were parallelly connected. This was also clearly observed in HRTEM images. This work will be helpful in the understanding and development of coal liquefaction technology. (C) 2020 Elsevier B.V. All rights reserved.