Investigation of typical heterocyclic fragment structures and reaction characteristics in oil shale using density functional theory

Abstract

The atomic structure and chemical behavior of heterocyclic fragments, such as pyridine, thiophene, and furan, in oil shale are crucial for optimizing its thermal pyrolysis process. This study employs density functional theory (DFT) to investigate the atomic structure and reactivity of typical heterocyclic fragments with impurities such as sulfur, nitrogen, and oxygen in kerogen macromolecules—the main organic compound of oil shale. By analyzing the free energy barriers, reaction rates and half-lives, we found that oxygen-containing heterocyclic compounds exhibited higher pyrolysis efficiency compared to nitrogen- and sulfur-containing heterocyclic compounds at the same temperature. We also analyzed the electrostatic potential and natural population analysis charges of the heterocyclic compounds and discovered that nitrogen- and sulfur-containing heterocycles had negative electrostatic potentials, making them more susceptible to electrophilic reactions. These findings provide valuable insights into the mechanisms and kinetics of various processes involved in oil shale processing, which can inform the development of more efficient and sustainable oil shale utilization strategies.