Asphaltene−Paraffin Structural Interactions. Effect on Crude Oil Stability

Abstract

The effect of asphaltene−paraffin complexes on crude oil stability, in terms of wax crystallization and asphaltene deposits solubility, was studied. The influence of flocculated asphaltenes on the wax crystallization tendency of a paraffinic crude oil and on the effectiveness of a maleic anhydride copolymer derivative paraffin inhibitor was evaluated by means of polarized light microscopy. It was demonstrated that flocculated asphaltenes provide wax crystallization sites whose presence interferes with the inhibitor crystal modification mechanism. The existence of asphaltene−paraffin complexes was assessed by HPLC kinetic dissolution studies of composite materials formed by combinations of such hydrocarbon fractions. Commercial macrocrystalline and microcrystalline waxes were used in these experiments. Different types of asphaltenes were probed as well, covering varying ranges of aromaticities and stability. Asphaltene properties were observed to be important parameters influencing composites dissolution. A selective partition of paraffins and asphaltenes in solubilized fractions was determined by high-temperature thin-layer chromatography.