Separation and characterization of asphaltenic subfractions

Abstract

Recebido em 13/4/12; aceito em 2/7/12; publicado na web em 21/9/12The structure of the various asphaltenic subfractions found in crude oil was evaluated. For this purpose, C5 asphaltenes were extracted from an asphaltic residue using n-pentane as the flocculant solvent. The different subfractions were isolated from the C5 asphaltenes by the difference in solubility in different solvents. These were characterized by infrared spectroscopy, nuclear magnetic resonance, X-ray fluorescence, elementary analysis and mass spectrometry. The results confirmed that the subfractions extracted with higher alkanes had greater aromaticity and molar mass. However, small solubility variations between the subfractions were attributed mainly to the variation in the concentrations of cyclical hydrocarbon compounds and metals.

The influence of asphaltenes subfractions on the stability of crude oil model emulsions

“…Such (sub)fractions were obtained in a previous work as following. 27 The asphaltic residue and n-pentane (proportion of 15g:1L) were placed under stirring for 24 h. The insoluble fraction was placed in a Soxhlet extractor with n-pentane (proportion of 1g : 45mL). This extraction step continued until the paraffinic solvent appeared clear in the extractor.…”

“…[21][22][23][24] Among the properties desired of demulsifiers are high adsorption speed at the water-oil interface, displacement of the natural emulsifiers that stabilize the emulsions and formation of thin and fragile films at the water-oil interface, facilitating coalescence of the droplets. 16,25,26 The aim of this work was to study the influence of crude oil asphaltenes subfractions, obtained and characterized previously, 27 on the stability of water-in-oil (W/O) emulsions. The measurements were performed by the bottle test, with and without the addition of a demulsifier.…”

Optimization of Demulsifier Formulation for Separation of Water From Crude Oil Emulsions

“…They consist of condensed aromatic sheets with alkyl and cyclic side chains and heteroatoms (nitrogen, oxygen, sulfur) and trace metals like vanadium and nickel scattered throughout (Daaou et al, 2009). These molecules can have 30 or more carbons, and they are usually considered to be the heaviest and the most polar components of the petroleum, but recent work shows that the average molecular weight of asphaltenes extracted with n-heptane is about 750 g/mol (Groezin and Mullins, 2007) and surprisingly, lower values (around 400 g/mol) have also been found (Honse et al, 2012). They are characterized by a relatively constant hydrogen/carbon ratio of 1.15 with a specific gravity near one; however, the nature of asphaltenes in crude oil is still a subject of debate.…”

Development of Multifunctional Formulations for Inhibition of Waxes and Asphaltenes Deposition

“…In the last stage, the crystals unite to form a three-dimensional wax network that impedes the oil flow Asphaltenes are the petroleum components with the highest polarity and molar mass. They have great structural complexity due to their polycondensed aromatic rings, containing alkyl radicals of different sizes and functional groups formed by oxygen, nitrogen and sulfur, as well as heavy metals such as vanadium, nickel and iron (Honse et al, 2012;Mullis, 2007). Asphaltenes are defined as the petroleum fraction that are insoluble in n-alkanes (n-pentane, n-heptane etc.)…”