Molecular Weight and Density Distributions of Asphaltenes from Crude Oils

Energy Fuels, 2013, 27 (5), pp 2474–2487, DOI: 10.1021/ef400142v
Molecular Weight and Density Distributions of Asphaltenes from Crude Oils
D. M. Barrera , D. P. Ortiz , and H. W. Yarranton *
Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive Northwest, Calgary, Alberta T2N 1N4, Canada
Abstract
Because asphaltenes self-associate, their molecular weight and density distributions are a factor in asphaltene precipitiation. In order to ascertain these distributions, researchers fractionated heptane-extracted asphaltenes from four crude oils into solubility cuts. They dissolved the asphaltenes in toluene and then partially precipitated them at specified ratios of heptane/toluene to generate sets of light (soluble) and heavy (insoluble) cuts.
They measured the molecular weight and density for each cut. They determined that the asphaltenes include both associating and non-associating asphaltenes. They developed a guideline to represent the molecular weight distribution of non-associated and associated asphaltenes with a Γ distribution function. Finally, they correlated the density of asphaltene cuts to their molecular weight.
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