(72b) Microstructure of Asphaltenes in Solvent Blends Investigated By Viscometry

Weiyi Kong, Amanda Chew, Michael P. Hoepfner

Department of Chemical Engineering, University of Utah, Salt Lake City, Utah 84112

keywords: Asphaltene, Solubility, Rheology, Viscosity

Abstract

In this talk we will present our work on the microstructure of asphaltenes in solvent blends investigated by intrinsic viscosity measurements. Previous work has verified that the asphaltenes cluster that in the process of aggregating and preciptiating from solution have a more compact structure than soluble asphaltenes as determined from fractal dimension measurements of scattering results. The compaction of asphaltene clusters may lead to a readily detectable decrease in the intrinsic viscosity. Characterizing the microstructure of asphaltenes through intrinsic viscosity measurements will shed light on the asphaltene precipitation mechanism using a readily available laboratory technique. In this study, heptane-toluene blends were used to control asphaltene solubility and molecular weight distribution of the polydisperse asphaltene mixture. Our goal was to investigate what impact the addition of a precipitant had on modifying the intrinsic viscosity of asphaltene solution to understand the mechanism of asphaltene precipitation. Experiments varied the n-alkane precipitant used to destabilize the asphaltenes to investigate trends in asphaltene microstructure and phase behavior. The results of intrinsic viscosities of asphaltene in different solvent blends aids in the understanding of how the asphaltene microstructure changes as asphaltenes destabilize and phase separate from organic and petroleum mixtures.