Crude oil and base oil analysis in collaboration with petroleum companies

Analysis of complex crude oil and petroleum mixtures is challenging as they mostly consist of large, saturated hydrocarbons. In collaboration with petroleum companies, we have developed methods for the structural characterization of large alkanes in heavy base oils and other petroleum products by using high-temperature GCxGC/EI TOF HRMS and APCI LQIT Orbitrap HRMS. The high-temperature GCxGC/EI TOF HRMS method has been successfully used for the separation and classification of thousands of alkanes (and aromatic compounds) in heavy base oils. The APCI LQIT high-resolution Orbitrap method has shown great performance in determining the molecular weights, elemental compositions and sizes of aromatic cores in aromatic compounds in heavy base oils and in quickly providing valuable structural information. We also have developed an automated, accurate and precise method for the classification and quantitation of saturated and aromatic hydrocarbons in middle distillates of crude oil, which will facilitate oil refineries to improve the conversion processes of these distillates.

Figure 14. A low-resolution (+)APCI mass spectrum of a base oil sample.

Table 1. Relative abundances of different hydrocarbon types in Base Oil 1 based on (+)APCI MS measurements.

Figure 15. The relationship between the abundances of the different compound types and the number of carbon atoms in the compounds in Base Oil 1 based on (+)APCI MS.

Figure 16. The GCxGC/(+)EI TOF MS chromatogram of Base Oil 1 spiked with five linear alkane model compounds (shown in red dots and text). Primary oven temperature: 235 – 380 ⁰C; secondary oven temperature offset: 5 ⁰C; modulator temperature offset: 15 ⁰C; modulation time: 8 s. Peaks corresponding to linear and branched alkanes are marked in red. Peaks corresponding to cycloalkanes are marked in blue. Peaks corresponding to aromatic hydrocarbons are marked in orange.

Table 2. Relative abundances of compounds in three hydrocarbon classes in Base Oil 1 as determined based on GCxGC/(+)EI TOF MS data.

References:

1. Manheim, J. M.; Milton, J. R.; Zhang, Y.; Kenttämaa, H. I. Fragmentation of Saturated Hydrocarbons upon Atmospheric Pressure Chemical Ionization Is Caused by Proton-Transfer Reactions. Anal. Chem. 2020, 92(13), 8883–8892.
2. Manheim, J.M.; Wehde, K.; Zhang, W.T.J.; Vozka, P.; Romanczyk, M.; Kilaz, G.; Kenttämaa, H.I. Identification and Quantitation of Linear Alkanes in Lubricant Base Oils by Using GC×GC/EI TOF Mass Spectrometry. J. Am. Soc. Mass Spectrom. 2019, 30(12), 2670–2677.
3. Manheim, J.M.; Zhang, Y.; Viidanoja, J.; Kenttämaa, H.I. An Automated Method for Chemical Composition Analysis of Lubricant Base Oils by Using Atmospheric Pressure Chemical Ionization Mass Spectrometry. J. Am. Soc. Mass Spectrom. 2019, 30(10), 2014–2021.
4. Jin, C.; Viidanoja, J.; Li, M.; Zhang, Y.; Ikonen, E.; Root, A.; Romanczyk, M.; Manheim, J.M.; Dziekonski, E.; Kenttämaa, H.I. Comparison of Atmospheric Pressure Chemical Ionization and Field Ionization Mass Spectrometry for the Analysis of Large Saturated Hydrocarbons. Anal. Chem. 2016, 88(21), 10592–10598.