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Energy & Fuels 2009, 23, 1194–1200
Asphaltene Nanoaggregates Studied by Centrifugation† Farshid Mostowfi,*,‡ Kentaro Indo,‡ Oliver C. Mullins,§ and Richard McFarlane| Schlumberger-DBR Technology Center, Edmonton, Alberta T6N 1M9, Canada, Schlumberger-Doll Research, 1 Hampshire Street, Cambridge, Massachusetts 02139, and Alberta Research Council, 250 Karl Clark Road, Edmonton, Alberta T6N 1E4, Canada ReceiVed August 1, 2008. ReVised Manuscript ReceiVed NoVember 2, 2008
The colloidal structure of asphaltenes impacts various physical properties and is important to characterize. Previously, in both laboratory and oilfield studies, asphaltenes have been shown to form nanoaggregates. In addition, previous work has shown that asphaltenes exhibit a critical nanoaggregate concentration (CNAC) in toluene in the range of 50-150 mg/L. In this study, centrifugation is used to prove a major change of asphaltene aggregation at the CNAC concentration, thereby corroborating previous results. Collection of these nanoaggregates by centrifugation validates there existence. The nanoaggregate size is found to be ∼2.5 nm, which is compatible with corresponding previous determinations from gravitational gradients. Asphaltene monomers are seen to be small (
