The Solubility and Three-Dimensional Structure of Asphaltenes

Abstract

The tendency of the asphaltenes to form aggregates in hydrocarbon solution is one of their most characteristic features and has tended to complicate the determination of the structure of petroleum. In addition, if the composition and properties of the precipitated asphaltenes reflect those of the micelles in solution, the latter should be considered as mixed micelles. This is a reasonable assumption in view of the large quantities of soluble resins found in the precipitated solid.Empirical observations indicate that the resins play an important role in stabilizing asphaltenes in crude oil and under unfavorable solvent conditions the asphaltene species are prone to further aggregation into clusters that are unstable and precipitate from the crude oil. It is also suggested that the resins and the asphaltenes from a particular crude oil have points of structural similarity relative to the asphaltenes and resins from another crude oil. On a more localized scale, i.e. in one particular crude oil there are also structural differences within the constituents of asphaltenes and structural differences within the constituents of the resins are also anticipated.Therefore, the structure of the micelles within anyone crude oil must be expected to be varied and non-homogenous. From the evidence cited herein, it follows that the potential for graphite-type stacking by the asphaltene molecules in the center of a micelle might not be as great as the potential for the micelles forming by asphaltene-resin interactions rather than by asphaltene-asphaltene interactions.

The influence of asphaltene-resin molecular interactions on the colloidal stability of crude oil

“…Resin molecules are smaller and lower in molecular weight compared to asphaltene molecules, so the asphaltene micelles are expected to be surrounded by more than one resin molecule [91,92]. Indeed, the quantitative ratio of Asphaltenes Resins Aromatics Saturates Fig.…”

Multiple-sourced features of marine oils in the Tarim Basin, NW China – Geochemical evidence from occluded hydrocarbons inside asphaltenes

“…Previous work has suggested that asphaltenes can adsorb and even occlude compounds, including hydrocarbons, within their complex three-dimensional structures (Schabron and Speight, 1998). Well protected from secondary alteration events, these occluded hydrocarbons represent the original oil derived from kerogen (Liao et al, 2006).…”

Petroleum Asphaltenes - Part 1: Asphaltenes, Resins and the Structure of Petroleum

“…An important corollary of petroleum composition is that the mole fraction of resins is always larger that that of asphaltenes and hence the micelles are expected to be richer in resins (Schabron and Speight, 1998). The micelle center would be formed from polar asphaltene molecules that would be surrounded by one or more of the resin molecules that are placed between the center and the periphery thereby masking the polar functions.…”