Comparing Crude Oils with Different API Gravities on a Molecular Level Using Mass Spectrometric Analysis. Part 2: Resins and Asphaltenes

Abstract

The combination of fractionation methods for crude oils, such as saturate, aromatic, resin and asphaltene (SARA) fractionation, in combination with analysis by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has been used for reducing the complexity and improving the characterization of crude oils. We have used the FT-ICR MS techniques in conjunction with electrospray ionization (ESI(±)) and atmospheric pressure photoionization (APPI(+)) to find trends between MS data of SARA fractions of crude oils with different American Petroleum Institute (API) gravities from the Sergipe-Alagoas basin (Brazil), focusing on the resin and asphaltene fractions. For the first time, an adaptation of the SARA fractionation has been performed to obtain a second resin fraction, which presented compounds with an intermediate aromaticity level between the first resins and asphaltene fraction. Both the first and second resin and the asphaltene fractions were studied on a molecular level using multiple ionization techniques and FT-ICR MS to find a direct relationship between the API gravities of a heavy, medium and light crude oil. For the FT-ICR MS data and the API gravities an aromaticity tendency was found. The data show that the use of SARA fractionation with FT-ICR MS offers a tool for comprehensive characterization of individual fractions and selective chemical characterization of the components in crude oils.

A Detailed Look at the Saturate Fractions of Different Crude Oils Using Direct Analysis by Ultrahigh Resolution Mass Spectrometry (UHRMS)

“…Separation of the maltenes was performed using an automated open column chromatography system (Sepecore X10, Büchi, Labortechnik GmbH, Essen, Germany equipped with a UV-Vis Detector C-640 (Büchi, Labortechnik GmbH, Essen, Germany)) using cartridges (150 mm × 12 mm, packed with silica sorbent) and a solvent flow rate of 3 mL min −1 . The saturate, aromatic, resin I and resin II fractions where eluted using cyclohexane, cyclohexane:dichloromethane (1:1, v/v), methanol and ethyl acetate, respectively [10]. Elution of the single fractions was maintained using the UV-absorption of the effluent at 254 nm.…”

“…SARA is the acronym for the different fractions resulting from this technique (Saturate, Aromatics, Resin and Asphaltene). This fractionation technique was first introduced by Jewel et al [6] and was further studied, developed and optimized in the last decades by various research groups [1,[7][8][9][10]. SARA fractionation is based on the solubility, polarity and adsorption affinity of the different petroleum compounds [3,9].…”

“…Because of the irreversible adsorption affinity of asphaltenes to the stationary phase, the initial step is precipitation of asphaltenes using a paraffinic solvent (e.g., n-heptane or pentane). Later, the remaining portion of the crude oil (maltenes) are further fractionated to saturates, aromatics and resins by column chromatography using different solvents [3,[10][11][12]. Saturates, referring to their chemically descriptive name, are known to contain mainly nonpolar compounds including linear, branched and cyclic saturated hydrocarbons.…”

Bioremediation of Total Petroleum Hydrocarbons (TPH) by Bioaugmentation and Biostimulation in Water with Floating Oil Spill Containment Booms as Bioreactor Basin

“…The chemical composition of the crude oil contains the following four main compounds saturated, aromatics, resins and asphaltenes [ 38 ]. This is also named SARA [ 39 , 40 ]. Saturated hydrocarbons are regular and branched alkanes with C n H 2n+2 (aliphatic) structure.…”

Molecular-level reaction network in delayed coking process based on structure-oriented lumping

“…6 The application of supercritical fluid extraction and fractionation (SFEF) technology [7][8][9] and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry technology made breakthroughs in understanding the complex molecular structure of petroleum. [10][11][12][13] At the same time, the rapidly-developing computing technology greatly promoted the development of petroleum processing models from the traditional multi-lumping models [14][15][16][17] based on fractions to the molecular-level reaction kinetic models. Representative modeling method for molecular-level reaction kinetic models of refining processes included the structure-oriented lumping (SOL) method, [18][19][20] the modified molecular-type homologous serious (MTHS) representation, 21 and Bond-Electron matrix with Monte Carlo simulation and atomic topology.…”