NMR IMAGING STUDIES OF ASPHALTENE PRECIPITATION IN ASPHALTS

Nuclear magnetic resonance (NMR) images were obtained on asphalts whic h were dissolved in toluene and titrated with iso-octane to the point of onset of flocculation. When iso-octane was added to the asphalt and the mixture stirred, asphaltene precipitation proceeded in a normal f ashion. However, when the titrant was added slowly to minimize mixing at the iso-octane-asphalt-toluene interface, the images showed that a layer of material formed at the solvent interface which was different from the asphaltenes or the maltenes. The formation of this layer appe ared to depend on asphaltene concentration and degree of aging, i.e. t he greater the asphaltene content and the degree of aging, the more pr ominent the layer. The WC ratio of the layer was similar to the resin fraction of the asphalt. These observations suggest that NMR imaging m ight be used to assess asphalt compatibility in aged asphalts. (C) 199 8 Elsevier Science Ltd. All rights reserved.