Heavy petroleum composition. 2. Progression of the boduszynski model to the limit of distillation by ultrahigh-resolution FT-ICR mass spectrometry

Abstract

Heavy petroleum fractions are structurally and compositionally complex mixtures that defy characterization by many traditional analytical techniques. Here, we present the detailed characterization of a Middle Eastern heavy crude oil distillation series, in further support of the Boduszynski model, which proposes that petroleum is a continuum with regard to composition, molecular weight, aromaticity, and heteroatom content as a function of the boiling point. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides ultrahigh resolving power and mass accuracy and thereby allows for elemental assignment for each of the tens of thousands of peaks in a single crude oil sample. Part 1 of our five-part series established the validity of the Boduszynski model for the heavy vacuum gas oil (HVGO) distillation series. Here, we extend our analysis to fractions from a Middle Eastern heavy crude with cut temperatures including and beyond the middle distillate range. Collectively, the detailed compositional results for all heteroatom classes strongly support the continuity model. Interestingly, extrapolation of distillable compositional space to a high carbon number (up to 1 MDa) cannot account for the bulk properties of nondistillable (asphaltenic) species. Thus, either the continuity model does not accurately describe nondistillable petroleum materials (they are discontinuous in compositional space) or they are not high-molecular-weight (>2000 Da) materials. © 2010 American Chemical Society.