Pyrolysis of a Low Asphaltene Crude Oil under Idealized in Situ Combustion Conditions

The coke formation is crucial to the crude oil in situ combustion (ISC) process. This study provided some insights through analyzing the influences of temperature and reaction atmosphere on the coke chemical-structural property. Thin coke films were produced on the polished single-crystal Si surface from the Xinjiang crude oil. Their functional groups were compared by Fourier transform infrared spectroscopy (FTIR), while the nanostructures were characterized through Raman spectroscopy, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) techniques. In addition, the low-temperature oxidation (LTO) coke and the pyrolytic coke reactivities were investigated by thermogravimetric analyses. The results indicated that the main carbon structures in the pyrolytic coke were amorphous. No crystallization phenomena, such as the aromatic ring condensation and the planar stacking, were observed within the characteristic ISC pyrolytic temperature range. Despite the pyrolytic coke yield increase with the temperature, almost constant chemical-structural properties were conserved. This study compared the chemical-structural properties of the LTO coke and the pyrolytic coke from the ISC process. The greater oxidation rate of the LTO coke was attributed to the considerable O-containing groups.