Asphaltene Precipitation from Athabasca Bitumen Using an Aromatic Diluent: A Comparison to Standard n-Alkane Liquid Precipitants at Different Temperatures
journal contributionposted on 16.12.2015 by Ørjan Bjorøy, Per Fotland, Eimund Gilje, Harald Høiland
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Asphaltenes are precipitated from Athabasca bitumen upon the addition of liquid precipitants. The asphaltene onset and the amount of precipitated asphaltenes using different equivalents of added liquid precipitant are determined. The deasphalting power of an aromatic solvent with structural similarities to toluene, namely, α,α,α-trifluorotoluene (BTF), is investigated, and the results are compared to using n-pentane (n-C5), n-hexane (n-C6), and n-heptane (n-C7) as liquid precipitants. A correlation between maximum asphaltene precipitation and the surface tension of the pure liquid precipitants studied is observed. Increasing the temperature results in increasing the volume fraction of liquid precipitant at the asphaltene onset and a decrease in the amount of maximum asphaltene precipitation. Composition elemental analyses show a small increase in the relative amounts of sulfur atoms in asphaltenes with increasing precipitation temperatures. The appearances of asphaltenes precipitated at different temperatures are compared before and after thorough washing with excess liquid precipitant. Asphaltene precipitation experiments are time-consuming and have motivated us to introduce an empirical function to describe asphaltene yields between asphaltene onset and maximum asphaltene precipitation requiring less experimental data. Our results provide useful tools for future studies of gradient asphaltene precipitation; processes that are of current interest with the development of new(er) techniques for bitumen extraction.