Study of the aggregation and adsorption of asphaltene sub-fractions A1 and A2 by white light interferometry: Importance of A1 sub-fraction in the aggregation process

In the present work we show the application of white light interferometric microscopy to study the adsorption of asphaltene on to glass surfaces. Asphaltenes, isolated from two different crude oils and dissolved in chloroform, were studied. The adsorption behavior of the total asphaltene and two sub-fractions is presented and the adsorption behavior is correlated with the solubility of each sub-fraction in different solvents. The existence of nanoaggregates of asphaltenes, even in a good solvent such as chloroform, is presented. The importance of each asphaltene sub-fraction in the aggregation and subsequent deposition is clearly shown. The characteristics of the adsorbed film illustrate differences in the average molecular structures of each sub-fraction and their impact on the solute-solute interaction and consequently the solubility. The results demonstrate, for the first time, the importance of A2, the asphaltene sub-fraction which is soluble, in the impact in the aggregate adsorption. (C) 2013 Elsevier B.V. All rights reserved.