Abstract
Molecular compositions of two types of heavy oil were studied using positive atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Vacuum gas oil (VGO) was generated from vacuum distillation of atmospheric residual oil (AR), and slurry oil (SLO) was generated from catalytic cracking of AR. These heavy oils have similar boiling point ranges in the range of 210-, but they showed different mass ranges and double-bond equivalent (DBE) distributions. Using DBE and carbon number distributions, aromatic ring distributions, and the extent of alkyl side chains were estimated. In addition to the main aromatic hydrocarbon compounds, those containing sulfur, nitrogen, and oxygen heteroatoms were identified using simple sample preparation and ultra-high mass resolution FT-ICR MS analysis. VGO is primarily composed of mono- and di-aromatic hydrocarbons as well as sulfur-containing hydrocarbons, whereas SLO contained mainly polyaromatic hydrocarbons and sulfur-containing hydrocarbons. Both heavy oils contain polyaromatic nitrogen components. SLO inludes shorter aromatic alkyl side chains than VGO. This study demonstrates that APPI FT-ICR MS is useful for molecular composition characterization of petroleum heavy oils obtained from different refining processes.
Highlights
Due to increasing crude oil prices and the availability of sour heavy crude oils and unconventional crude oils, most refineries are trying to upgrade the residual heavy oil fractions of petroleum to transportation fuels or petrochemicals to maximize profits from crude oil
The spectra were calibrated using internal CH2 series peaks of double-bond equivalent (DBE) 4 hydrocarbon class (HC) class compounds, and the molecular formulas were assigned within an error of 2 ppm
The relative intensity of compounds with DBE values between 0 and 3 observed by atmospheric pressure photoionization (APPI) FT-ion cyclotron resonance (ICR) MS was relatively low, suggesting that non-aromatic hydrocarbons were not ionized by APPI
Summary
Due to increasing crude oil prices and the availability of sour heavy crude oils and unconventional crude oils, most refineries are trying to upgrade the residual heavy oil fractions of petroleum to transportation fuels or petrochemicals to maximize profits from crude oil. Two types of heavy oil from different refinery processes were compared by 7T FT-ICR MS coupled with APPI : VGO and slurry oil (SLO). The two heavy oils have similar boiling point ranges and the same order of nitrogen and sulfur contents.
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