THE SOLUBILITY AND 3-DIMENSIONAL STRUCTURE OF ASPHALTENES

The tendency of the asphaltenes to form aggregates in hydrocarbon solu tion is one of their most characteristic features and has tended to co mplicate the determination of the structure of petroleum. In addition, if the composition and properties of the precipitated asphaltenes ref lect those of the micelles in solution, the latter should be considere d as mixed micelles. This is a reasonable assumption in view of the la rge quantities of soluble resins found in the precipitated solid. Empi rical observations indicate that the resins play an important role in stabilizing asphaltenes in crude oil and under unfavorable solvent con ditions the asphaltene species are prone to further aggregation into c lusters that are unstable and precipitate from the crude oil. It is al so suggested that the resins and the asphaltenes from a particular cru de oil have points of structural similarity relative to the asphaltene s and resins from another crude oil. On a more localized scale, i.e. i n one particular crude oil there are also structural differences withi n the constituents of asphaltenes and structural differences within th e constituents of the resins are also anticipated. Therefore, the stru cture of the micelles within any one 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 molecu les 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.