In-depth characterization of light, medium and heavy oil asphaltenes as well as asphaltenes subfractions. (15th September 2022)

• Record Type: Journal Article
• Authors: Salehzadeh, Marziyeh; Husein, Maen M.; Ghotbi, Cyrus; Dabir, Bahram; Taghikhani, Vahid
• Is Part Of: Fuel. Volume 324:Part A(2022)
• Publication Date: 2022-09-15
• Subjects: A3000-2750 C–H stretching area of aliphatic -- A3150-3000 C–H stretching area of aromatic -- APCI Atmospheric pressure chemical ionization -- C aliphatic Aliphatic carbon -- C aromatic Aromatic carbon -- CA-Caliph Substituted aromatic carbons -- CAH Aromatic carbon atoms bonded to hydrogen atoms -- CAHβX Aromatic carbons bonded to β hydrogens to heteroatom -- CAP3 External peripheral aromatic carbon atoms at the junction of two fused rings -- Cau Carbons number per aromatic unit -- CAX Aromatic carbons attached to heteroatoms -- CDCl3 Deutero-chloroform -- CHNS Carbon-hydrogen–nitrogen-sulfur -- CY Internal triple bridgehead aromatic carbons -- dm Distance between two aromatic sheets -- dr Distance between saturate chains -- EDX Energy-dispersive X-ray spectroscopy -- F1 Least soluble subfraction -- F2 Intermediately soluble subfraction -- F3 Most soluble subfraction -- fa Aromaticity -- FTIR Fourier transform infrared -- GPC Gel permeation chromatography -- H Heavy crude oil -- Hal Aliphatic hydrogen -- Halα Aliphatic hydrogen in α-position -- Halβ Aliphatic hydrogen in β-position -- Halγ Aliphatic hydrogen in γ-position -- Har Aromatic hydrogen -- Hol Hydrogen attached to olefinic carbon -- I1376 C-CH2/C-CH3 symmetric bending -- I14555 C-CH2/C-CH3 asymmetric bending -- I1600 Aromatic C=C stretching -- I2924 Aliphatic CH2 stretching asymmetric -- I2957 Aliphatic CH3 stretching asymmetric -- I3050 Aromatic C–H stretching -- IAr Hydrogen aromaticity index -- L Light crude oil -- La Average diameter of aromatic sheets -- Lc Average height of aromatic cluster perpendicular to plane of sheets -- M Medium crude oil -- m/z Mass to charge -- Me Number of aromatic sheets in a cluster -- MS Mass sectrometry -- MW Molecular weight -- NMR Nuclear magnetic resonance -- PAH Polycyclic aromatic hydrocarbon -- Ra Number of aromatic rings for each aromatic sheet -- SEC Size exclusion chromatography -- SEM Scanning electron microscopy -- VPO Vapor pressure osmometry -- XPS X-ray photoelectron spectroscopy -- XRD X-ray diffraction; Asphaltenes -- Fractionation -- Spectroscopic technique -- Elemental analysis -- Solubility -- Association; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2022.124525
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Detailed analysis of asphaltenes originated from light, medium and heavy oils is provided. Asphaltenes are compared with least, intermediately and most soluble medium asphaltenes subfractions. Heavy oil asphaltenes and most soluble subfractions displayed least aromaticity and longest alkyl side chains. Precipitation/destabilization is majorly driven by π-π interactions and low steric hindrance. The effect of asphaltenes structures on their stability behavior is discussed. Abstract: Asphaltenes, and their related issues, have been the focus of many literature investigations. However, in-depth analysis of asphaltenes structure and its relation to asphaltenes stability has been considered by fewer studies. In this research, extensive analysis of the structure of asphaltenes extracted from light, medium, and heavy oils is provided, together with analysis of three subfractions of the medium oil asphaltene having the least, intermediate, and highest solubilities. To this end, elemental analysis, EDX, mass spectroscopy, FTIR, NMR, XRD, and SEM results were collected. Higher hydrogen content and hydrogen/carbon atomic ratio, lower aromatic nature and olefinic entities were observed in heavy oil asphaltenes as well as the most soluble subfraction. Moreover, the molecular structure of heavy oil asphaltenes and the most soluble subfraction displayed broader mass to charge ( m / z ) distribution range, longer alkyl side chains as well as higher number of stacked aromatic sheets within their nanoclusters. Asphaltenes hydrogens in α position followed similar trend as their heteroatom content, which was higher for the less soluble subfraction and medium oil asphaltenes. Generally, heavy oil asphaltenes possessed a molecular structure that was closer to the most soluble asphaltenes subfraction, whereas light oil asphaltenes possessed a molecular structure similar to the least soluble subfraction. Asphaltenes precipitation/destabilization was attributed to primarily higher attractive π-π interactions coupled with lower steric hindrance.