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Petroleum molecules with interfacial activity play a fundamental role in stabilizing water-in-oil (W/O) emulsions and thus have been the focus of many studies. Using the wet silica method, crude oil samples from Brazilian fields (designated P5 and P6) were fractionated into two fractionsone with the interfacially active molecules (IA) and another containing the non-interfacially active molecules (NIA). This fractionation was performed using a mixture of cyclohexane/toluene (1:1 v/v) (CH/TOL) for oils P5 and P6 and n-octane/toluene (1:1 v/v) (OC/TOL) only for oil P6 to evaluate the influence of the solvent system on the profile of the fractions obtained. The fractions obtained and the parent oils were characterized chemically by Fourier-transform infrared spectroscopy (FTIR), 1H-nuclear magnetic resonance (1H-NMR), and electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI (±) FT-ICR MS) and analyzed for interfacial activity using systems composed of brine (aqueous phase) and n-heptane/toluene mixture (organic phase). The results from FTIR and 1H-NMR evidenced the polar and aromatic character of the IA fractions, while the predominantly hydrocarbon composition was observed in the NIA fractions as well as their respective parent oils. The characterization by FT-ICR MS showed the influence of the solvent system on the basic species of the IA fractions, by ESI (+), and a difference in the acid compounds of the fractions isolated from the two parent oils, by ESI (−): the IA fraction isolated from P5 presented the compound classes O4[H] and O2[H] as major components, while the major compounds in the IA fractions isolated from P6 with CH/TOL or OC/TOL were O­[H], O2[H], and N­[H]. Decrease in the interfacial tension values on the order of 30% was observed when comparing each interfacially active fraction with their parent oil.

Naphthenic acids (NAs), present in a typical Brazilian acid crude oil and its thermal degradation products, were investigated using two separation methodologies: solid-phase extraction (SPE) and liquid–liquid extraction (LLE). Fractions produced were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and negative-ion-mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI(−)-FT-ICR MS). Of the NAs extraction methods studied, SPE was more efficient than LLE. Further, ESI(−)-FT-ICR MS results showed that the SPE method with eluent phase variation allowed for the detection of a larger amplitude of NAs compounds (m/z 200–1200), reducing the occurrence of ion suppression on the NAs of higher average molecular weight (M w) distribution. It was noted that the aromaticity or double bond equivalent (DBE) of these produced collective fractions as well as their M w values increased as a function of the polarity of the extraction system (DCM → DCM:MeOH:FA). Also, 1H NMR analysis revealed the alkyl predominance evidenced by the presence of high Hβ content in fractions, suggesting that the NAs compounds have long and unbranched chains. The behavior of NAs species during the thermal degradation process was also evaluated, and the results showed their presence in only five SPE extracts out of six, containing different M w values (M w = 366, 417, 531, 662, and 836 Da). This suggests that, in the last SPE fraction (named SF6: m/z 700–1150, carbon number of C52–C72, and DBE = 0–15; detected only in virgin crude oil), the NAs were selectively cracked during the thermal degradation process.

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ESI-FT-ICR MS was efficient in identifying primary (carbohydrates and organic acids) and secondary metabolites (13 phenolic compounds) presents in the crude and phenolic extract of the samples, respectively. © 2017 Society of Chemical Industry.