Molecular weight and specific gravity distributions for athabasca and coldlake bitumens and their saturate, aromatic, resin, and asphaltene fractions

Molecular weight and specific gravity distribution data are required for ch aracterizing oils containing complex mixtures, and this characterization in formation is very essential for the computation of thermodynamic properties and phase equilibria. The accuracy of these computations will be enhanced if molecular weight and specific gravity data of fractions containing simil ar groups/structures or common solubility properties are used. This is beca use the critical properties normally correlate better for a single fraction than for the whole oil. Data in this work is relevant to the phase equilib rium calculations and predictions of asphaltene precipitation from represen tative Canadian bitumens. Athabasca and Cold Lake bitumen samples were used and divided into asphaltene and deasphalted oil fractions by adding 40 vol umes of n-heptane. The deasphalted oils were divided into saturate, aromati c, and resin fractions using a modified ASTM D2007 procedure. The average m olecular weights of these SARA fractions were measured using vapor pressure osmometry (VPO), and the molecular weight distributions of the SARA fracti ons were measured using gel permeation chromatography (GPC) calibrated with polystyrene standards. Results were verified using VPO measurements, and t he correction factors for the GPC distributions were calculated. The specif ic gravities of saturate and aromatic fractions were measured using an Anto n-Paar densitometer, and resin fraction values were obtained using a water pycnometer and those of;asphaltenes using a helium pycnometer. Specific gra vity distributions were computed using the measured data and the correlatio n reported in the literature.