Contribution of mass spectrometry in assessing quality of petroleum fractions: The use of mass spectrometry for assessing asphaltenes

• Asphaltenes were analyzed by MALDI TOF.
• Matrix MALDI TOF, quality of spectra, and compositional information were evaluated.
• Chemical compositions of asphaltenes found were analyzed (C, H, S, N and O).

This study presents the results of an analysis of crude oil and asphaltene samples using the MALDI TOF technique. Thirty crude petroleum samples (24.53–32.05 API gravity) obtained from a Brazilian refinery were used in this study. Asphaltenes were precipitated from the corresponding crude oil samples with n-heptane. Mass spectra were acquired with a MALDI TOF mass spectrometer in a mass range of 100–1000 Da. The main purpose of this study was to analyze the composition of the asphaltene molecules extracted from oil samples according to their molecular composition (molecular weight and composition heteroatoms). The mean composition of the group analyzed was calculated as follows: 17% sulfur-containing molecules, 28% nitrogen-containing molecules, 19% oxygen-containing molecules, 12% sulfur–oxygen-containing molecules and 17% nitrogen–oxygen containing molecules; only 7% of the compounds contained only hydrogen and carbon in their composition. Finally, MALDI TOF analysis can be a very efficient process with a great potential for estimating the physicochemical properties of asphaltenes. A VBA (Visual Basic for Applications) algorithm allowed us to determine the elemental composition of components of asphaltene samples. The elemental composition showed that, despite having the same physical characteristics, the chemical composition of the samples was different.