Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

Abstract

Understanding the molecular structure characteristics of coal at the molecular level is of great significance to realize the rational utilization and efficient conversion of coal. This paper gives insights into the acquisition of characterization parameters of coal molecular microstructure by testing and analyzing the long flame coal from Qinggangping (QGP) Coal Mine through proximate analysis, ultimate analysis, vitrinite reflectance determination, fourier transform infrared Spectroscopy test (FTIR), X-ray photoelectron epectroscopy test (XPS), carbon nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The results show that benzene rings in the QGP coal are mainly connected in a disubstituted way, accounting for 36.48%. Oxygen atoms mainly exist in the oxygen-containing functional groups such as the ether C–O, C=O and –COO. Aliphatic hydrocarbons in the aliphatic group are mainly of symmetrical -CHx stretching vibration. Hydroxyl groups are mainly composed of OH–OH and OH–O hydrogen bonds, accounting for 29.21% and 21.53%, respectively. Nitrogen atoms exist in the form of C4H5N. The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. There are benzene, naphthalene and anthracene in the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is finally determined as C205H181O29N3S. On this basis, the two-dimensional and three-dimensional macromolecular models are constructed with the assistance of simulation software. In addition, the 13C-NMR spectra and densities of the constructed molecular models are calculated, which verifies the rationality of the models. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant.

Changes in the Microstructure and Wettability of Water-Containing Coal after Hot Flue Gas (CO2–N2) Injection

“…13 C NMR is a technical method that quantitatively and qualitatively identifies carbon atoms in organic matter. , Thanks to its high sensitivity and convenience regarding the characterization of complex mixtures, this method is commonly used to characterize the information about carbon skeletons in coal molecular structures. , …”

“…32,33 Thanks to its high sensitivity and convenience regarding the characterization of complex mixtures, this method is commonly used to characterize the information about carbon skeletons in coal molecular structures. 34,35 In this study, 13 C NMR tests were carried out by virtue of an AVANCE III 600 MHz fully digital superconducting NMR spectrometer (Bruker, Germany). In the tests, the following parameters were set: a rotor speed of 6,500 Hz, contact time of 2 ms, cyclic delay of 5 s, and number of scans of 5,012.…”