Comprehensive Characterization of Asphaltenes by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Precipitated under Different n-Alkanes Solvents

Abstract

Asphaltenes are still problematic fractions and their composition is not fully unveiled as it relates to the original crude oil and the precipitation method. In this work, the composition of asphaltenes precipitated with n-heptane and n-pentane from ten crude oils from the Sergipe-Alagoas Basin were assessed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) using five ionization procedures (electrospray ionization (ESI), ESI(+) with formic acid, ESI(−) with ammonium hydroxide, and ESI(−) with tetramethylammonium hydroxide, and atmospheric pressure photoionization (APPI), APPI(+) and APPI(−)) in combination with a 7.2 T LTQ FT Ultra Thermo Fisher spectrometer. The purpose was to evaluate compositional differences between C5- and C7-asphaltenes according to the adopted ionization methodologies. Asphaltenes were compared as a function of heteroatomic composition and aromaticity. Chemometrics strategies were employed to evaluate the heteroatom classes of higher va...