Molecular Recognition in Aggregates Formed by Asphaltene and Resin Molecules from the Athabasca Oil Sand

Abstract

The conformation of lowest energy of an asphaltene molecule of the Athabasca sand oil was calculated through molecular mechanics. The molecule has a complex globular shape with small internal cavities. This shape resulted mostly from the existence of polymethylene bridges connecting the aromatic regions. Molecular aggregates formed with the asphaltene and with nine resins from the same oil, and with n-octane and toluene, were also studied. The resins showed higher affinities for the asphaltene than toluene and n-octane and also exhibited a noticeable selectivity for some of the external sites of the asphaltene. This selectivity based on the molecular recognition of the site depends on the fit between the resins and the site of the asphaltene. The selectivity explains why resins of one oil may not solubilize asphaltenes from other crudes. An analysis of the changes in the enthalpic and entropic contributions to the free energy showed that both contributions should be considered when the stability of the asphaltene and resin molecular aggregates is examined.

Adsorption of asphaltenes from toluene on mineral surface

“…The solvated asphaltene crystallites are the primary particles of the colloidal dispersed phase. These particles can associate and aggregate, forming various size particles depending on temperature, pressure and concentration [8,15,16,19,21,[26][27][28][29][30][31][32][33][34][35]42,43]. In fact, asphaltenes are natural surfactants stabilising water/crude oil emulsion [21,22,[44][45][46][47][48][49][50][51][52].…”

Adsorption of asphaltenes from toluene on typical soils of Lublin region

“…The solvated asphaltene crystallites are the primary particles of a colloidal dispersed phase. These particles can associate and aggregate forming large particles dependent on temperature, pressure and concentration [7,8,11,13,[17][18][19][20][21][22][23][24][25][26][27]30,[40][41][42][43]. It is well known that asphaltenes are natural surfactants stabilising water/crude oil emulsion [13,14,[44][45][46][47][48][49][50][51][52][53].…”

Use of a Novel Fluorinated Organosulfur Compound To Isolate Bacteria Capable of Carbon-Sulfur Bond Cleavage

“…As conventional crude oils are consumed throughout the world, heavier oils are being exploited which, due to their high viscosity, cannot be transported from remote field sites to refineries without adding diluents. The vacuum residue fraction of crude oils (boiling point Ն 524°C [975°F]) contributes to viscosity, and recent models indicate that alkyl sulfides compose important bridges in the network of high-molecularweight molecules in this fraction (34). Up to 40% of the sulfur in these fractions is in the form of alkyl sulfides; if these alkyl COS bonds can be selectively cleaved using a biological catalyst, reductions in molecular size and viscosity could occur.…”