An Assay on Alkyl Aromatic Hydrocarbons: Unexpected Group-Type Separation of Diaromatic Hydrocarbons in Cretaceous Crude Oils from Brazilian Marginal Basin

Abstract

Numerous aromatic biomarkers such as aromatic carotenoids and aryl isoprenoids have been reported in Brazilian Cretaceous oils. The n-alkyl aromatics such as n-alkyl benzenes (ϕ-C n ), toluenes (ϕ T -C n ), xylenes, and mesitylenes have also been detected in geological samples and can be valuable tools in geochemical and environmental investigations. In this work, comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC−TOFMS) and GC−tandem MS (GC−MS/MS) were applied to identify the alkyl aromatic series in two crude oils from the Sergipe-Alagoas Basin, Brazil. Geochemical characteristics indicate a different depositional paleoenvironment for each sample, marine and lacustrine end-members. Aromatic compounds were identified using full mass spectrum information, diagnostic ions (i.e., m/z 92 for alkylbenzenes and m/z 106 for alkyltoluenes), selected reaction monitoring transitions, and coinjection with an authentic C 21 n-pentadecylbenzene standard. The Sergipe-Alagoas oils presented a series of n-alkylbenzenes and n-alkyltoluenes ranging from ϕ-C 7 to ϕ-C 33 and ϕ T -C 7 to ϕ T -C 30 , respectively. In addition, phytanyl arenes and a new series of α,ωbisphenylalkanes were identified for the first time in Sergipe-Alagoas oils. The n-alkylbenzene profile for marine crude oil resembles that of n-alkanes and n-alkylcyclohexanes, which suggests that they may have the same precursors. The investigation of aromatic fractions and detection of n-alkyl aromatic hydrocarbons in Brazilian Cretaceous oils provide new assignments to the contribution of organic matter and its geochemical significance.

Comprehensive Two-Dimensional Gas Chromatography Advances in Technology and Applications: Biennial Update

“…The composition of crude oils was the focus of many works in the past 2 years. ,,,− The work of Brazilian research groups led by Azevedo − and Augusto ,,,, focus on determining geochemical fingerprinting of samples from many regions in the country and optimizing methods for the resolution of crude oils and diesel composition. The use of GC×GC−TOFMS and other techniques such as Fourier transform ion cyclotron resonance-mass spectrometry (FTICR-MS) enabled the identification not only of hydrocarbons but also oxygen-, nitrogen-, and sulfur-containing volatile and nonvolatile compounds in crude oils with minimal sample preparation, with the latter promoted as a no-fractionation petroleomics technique. , GC×GC coupled with a VUV photoionization source TOFMS detector enabled the direct characterization and determination of the total sum of aromatic and aliphatic hydrocarbon species in different crude oils …”

“…Understanding the composition of these crudes helps to determine not only the quality and purity of petroleum and its derivatives but also biochemical precursors, biodegradation products, and geographical origin . The latter factor is especially useful in forensic investigations to locate and differentiate spill sources. − …”

“…149 Understanding the composition of these crudes helps to determine not only the quality and purity of petroleum and its derivatives but also biochemical precursors, biodegradation products, and geographical origin. 140 The latter factor is especially useful in forensic investigations to locate and differentiate spill sources. 152−157 The GC×GC resolving power was exploited to allow determination of kerosene surrogates, 158 assessment of the relationship between product composition and stability, 159 optimization of blends, 160 identification of diesel-derived pollutant emission in the atmosphere, 147,161 and development of statistical models for prediction of the fuel properties.…”