Characterization of Saturated Hydrocarbons in Vacuum Petroleum Residua: Redox Derivatization Followed by Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract

Heavy petroleum fractions, which have distinct chemical and physical properties, are becoming important refinery feedstocks. In comparison to aromatic and heteroatom-containing compounds, the saturate compounds in heavy petroleum fractions have rarely been analyzed using recent advanced mass spectrometry methods. In this work, the compositions of saturate fractions derived from six vacuum residua (VR) of different geological origins were determined and compared. Saturate fractions were subjected to ruthenium-ion-catalyzed oxidation (RICO) derivatization and characterized with negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results showed that the VR-derived saturates consisted of n-paraffins, isoparaffins, and naphthenes with 1–10 rings. The maximum double bond equivalent (DBE) values of species in various VR-derived saturates were similar. The maximum carbon number of VR-derived saturates was up to 100. The maximum carbon numbers of naphthenes in VR-derived saturates were generally greater than that of paraffins. The relative abundances and ranges of carbon numbers of the various species in VR-derived saturates differed depending upon their geological origin and the distillation temperature of samples. Compounds with 0–6 naphthenic rings were highly abundant in the VR-derived saturates. On the basis of the results of this study, the RICO/ESI FT-ICR MS method shows promise as a potential semi-quantitative analysis for saturates in heavy petroleum fractions.

Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons

“…FI-MS has been used in the petroleum industry for decades for the determination of the relative amounts of different hydrocarbon classes (paraffins and mono-, di-, tri-, tetra-, penta-, and hexanaphthenes) in base oils. ,, FI-MS is beneficial because it ionizes large saturated hydrocarbons with little to no fragmentation. However, FI-MS suffers from unsatisfactory robustness: poor reproducibility of ion signals (within a day and between days; see Figures S4–S6), limited dynamic range (often not more than 2 orders of magnitude), dependence of signal levels on emitter age, limited lifetime of FI emitters, variable fragmentation of ionized analytes (caused by new emitter or volatile sample, dust in the ion source, bad emitter part, etc.…”

Identification of basic nitrogen compounds in ethanol-soluble portion from Zhaotong lignite ethanolysis by positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

“…Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) proved to be a powerful technique for molecular characterization of extremely complex samples, such as petroleum [20][21][22][23], coal-derived liquids [24][25][26][27][28], pyrolysis bio-oils [29][30][31], and dissolved organic matter in waste water [32]. It has an ultrahigh broadband mass resolving power (exceeding 200,000) and mass accuracy (<1 ppm), allowing for baseline resolution of closely spaced isobaric species as well as distinct assignment of a unique elemental composition to each mass spectral peak.…”

Saturated Compounds in Heavy Petroleum Fractions

“…The presented structures reflect the identified elemental formulas (C c H h ); while the common biomarker molecules in cuts #14 and #20 have methyl and longer alkyl groups, , the polynaphthenic compounds in cuts #26 and #27 purposely do not contain alkyl side chains. In practice, the coelution of aromatic compounds into the saturates fraction can be a problem, and DBE values ≥4 could indicate naphthenic and/or aromatic rings. This is illustrated in Figure for the DBE distribution obtained for cut #20 saturates fraction, with representative saturated and aromatic compound families indicated.…”

“…Zhou et al converted saturated HCs in vacuum residue petroleum fractions through ruthenium-ion-catalyzed oxidation (RICO) into ketones (20%), which were reduced by LiAlH 4 reduction reaction to form alcohols, and alcohols (76%) which were analyzed by using ESI FT-ICR MS . Naphthenes with 0–6 rings were relatively highly abundant, and a maximum number of naphthenic rings of 10 and maximum carbon numbers of almost 100 were found common in the studied VR samples.…”