Investigation on Asphaltene Structures during Venezuela Heavy Oil Hydrocracking under Various Hydrogen Pressures

Venezuela heavy oil under various hydrogen pressures has been hydrocracked to investigate the variation of asphaltene components during reaction. Asphaltenes have been isolated from the product and analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR). The experimental data revealed that the interlamellar spacing and interchain spacing of the asphaltenes increased while the layer diameter decreased with the hydrogen pressure increasing. At the same time, the amount of aromatic carbon and alkyl carbon of the asphaltenes decreased gradually and the amount of naphthenic carbon increased. As the hydrogen pressure increased, the substitution ratio and the condensation degree parameter (HAU/CA) of the aromatic system in the periphery increased gradually and the replacement index and peri-position condensation index of asphaltenes decreased obviously.