THE COLLOIDAL ASPECT OF A MACROSTRUCTURE OF PETROLEUM ASPHALT

Abstract

ABSTRACT Petroleum asphalt contains asphaltene which is peptized with resin fraction molecules and is dispersed in an intermicellar medium consisting of saturates and aromatics (gas oil fraction). The single sheet of asphalcic molecules, determined by a variety of instrumental methods, has an average size of 0.5 × 1.5 nm. These mesomorphic units as evaluated by x-ray diffraction contain ordered nuclei of Lc with 1.0 - I.S nm and Lc of 2.0 nm. The micellar structure can be evaluated from petroleum, asphalt, or asphattene suspended in any medium by small angle x-ray or neutron scattering to yield a morphological diameter measuring ca. 10 nm. The tendency of these units to be associated has been investigated by a number of investigators, for example, electron microscopic techniques such as freeze-fracture, holycarbon and metal shadowing have indicated a cluster diameter of 100 - 1000 nm. The upper range of these clusters (super-micelles) can again agglomerate into a giant size of agglomerate on the order of 2 - 10 μm, which corresponds to a typical floe weight. At high temperature these supermicelles can form two-dimensional liquid crystalline mesophase spherules with sizes varying from 2 to 5 μm