Characterization of the molecular composition of asphaltene from heavy petroleum residue before and after hydrotreating

Asphaltene is the main source of coking and catalyst deactivation during hydrotreating of heavy oils, and the variation of molecular composition of asphaltene during hydrotreating is crucial for improving the refining processes of heavy oils. In this work, asphaltene obtained from Tahe vacuum residue was characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) before and after hydrotreating. The asphaltene samples were separated by solid-phase extraction (SPE) to reduce the matrix effect and ionization suppression, and the sub fractions were also measured by FT-ICR MS. It was also found that vanadyl porphyrins was enriched by SPE method, making the detection of trace amount of vanadyl porphyrins possible after hydrotreating. The structural differences of vanadyl porphyrins during hydrotreating were studied by FT-ICR MS. It is proved in this work that pre-separation is helpful for providing comprehensive molecular composition of asphaltene samples, which is valuable for refining industry.