Untreated and hydrotreated nitrogen-concentrated distillation fractions (483−504 °C) from Syncrude oil
have been analyzed by electron ionization, field desorption ionization, and electrospray ionization Fourier
transform ion cyclotron resonance mass spectrometry. The routinely attainable mass resolving power ≥300 000
at m/z 300 and sub-ppm mass accuracy allowed for resolution and elemental compositional assignment of
various compound classes. Multiple closely spaced mass doublets (with mass differences <10 mDa) were
detected. Although hydrotreatment reduced the relative abundances of several heteroatomic classes (N2, S3,
NS2, NOS, O3, OS2, and O2S) below detectability, N-, S-, O-, O2-, OS-, and NO-containing compounds survived
hydrotreatment. Analysis of N-, S-, and O-containing compounds and hydrocarbon compounds at the molecular
level exposes compositional changes and reveals the effectiveness of the hydrotreating process.
We analyzed three vacuum gas oil distillation fractions, 295−319 °C, 319−456 °C, and 456−543 °C, with
a home-built external electron ionization (EI) 7 T Fourier transform ion cyclotron resonance (FT-ICR) mass
spectrometer. EI at 10 eV allows soft ionization of aromatic compounds in the vacuum gas oil range.
Unambiguous elemental composition assignment provides insight into compositional variations at the molecular
level; for example, ultrahigh resolving power (m/Δm
50% ≈ 300 000 at m/z 300) and mass accuracy (<0.4
ppm) readily resolve C3/SH4 doublets (3.4 mDa mass difference) across the full m/z range of interest. To our
knowledge, this is the first time that hydrocarbons and sulfur-containing hydrocarbons have been completely
mass-resolved across the full VGO range. Aromatic hydrocarbons are the major detected components in all
three samples. In addition, many sulfur-, nitrogen-, and oxygen-containing compounds were directly observed.
The concentrations of the heteroatomic species increase with boiling point. Detailed data analysis revealed
compound types (rings plus double bonds) and their carbon number distributions for hydrocarbon and
heteroatomic compounds in the distillation fractions and increasing average molecular weight (or carbon number
distribution) and aromaticity with increasing boiling temperature of the petroleum fractions. The present analysis
requires only micrograms of sample, is fast (single time-domain data set acquired in a few seconds), and
highly reproducible.
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