The three-dimensional molecular structure model of Fushun oil shale kerogen, China

Abstract

Oil shale pyrolysis products mainly derive from the pyrolysis of organic kerogen. In this study, theoretical and experimental data were combined to conceive a reliable three-dimensional (3D) model of kerogen from the Fushun oil shale, China. The fundamental structural information was characterized based on experimental techniques, including 13C nuclear magnetic resonance spectroscopy (13C NMR), elemental analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), Fourier transform infrared spectroscopy(FTIR), and pyrolysis–gas chromatography–mass spectrometry (Py-GC/MS). Additionally, the molecular model of the two-dimensional structure of the kerogen was also established based on the basic structure and rapid thermal cleavage product information. The obtained formula is C240H322O32N7S5. Twelve isomers were constructed based on the “grid” concept and molecular dynamics methods and were applied to simulate the formed isomers. It has been identified that the number of grids affected the total energy of the kerogen, FS7 being the structure with the lowest total energy from the Fushun kerogen. The density of kerogen is an important index to evaluate the accuracy of the model, and our results indicate that there is a good match between the density calculated by the model and the experimentally obtained density. Also, a favorable relationship exists between the experimental and simulated values of the model covalent bond concentrations which proves the rationality and accuracy of the 3D molecular structure model. By combining theoretical and experimental data, we established a reliable structural model of the Fushun kerogen, which will provide a strong basis for future research on the pyrolysis mechanism of the Fushun oil shale at a molecular level.