Chemical Characterization of GPC Fractions of Athabasca Bitumen Asphaltenes Isolated before and after Thermal Treatment

Abstract

The object of this work was to determine whether new information could be obtained by using gel permeation chromatography (GPC) to fractionate asphaltene samples prior to analysis. In particular, GPC elution profiles, elemental analyses, molecular weights by vapor pressure osmometry (VPO), and boiling point distributions of the asphaltenes isolated from the original Athabasca bitumen feed (Feed) and from its total liquid product (TLP) after visbreaking were compared. The analyses showed that for GPC run using chloroform, fractionation was based on size where elemental analyses and boiling point distributions indicated that the earlier eluting fractions were not aggregates of later eluting fractions. The largest TLP asphaltene species were slightly smaller in size (by GPC and VPO) to those in the Feed asphaltenes; the smallest TLP asphaltene species were smaller than those isolated from the Feed asphaltenes and contained material with an initial boiling point of 340 °C despite both vacuum distillation (524...