Diffusivity of asphaltene molecules by fluorescence correlation spectroscopy.
Using fluorescence correlation spectroscopy (FCS) we measure the translational diffusion coefficient of asphaltene molecules in toluene at extremely low concentrations (0.03-3.0 mg/L): where aggregation does not occur. We find that the translational diffusion coefficient of asphaltene molecules in toluene is about 0.35 x 10(-5) cm(2)/s at room temperature. This diffusion coefficient corresponds to a hydrodynamic radius of approximately 1 nm. These data confirm previously estimated size from rotational diffusion studied using fluorescence depolarization. The implication of this concurrence is that asphaltene molecular structures are monomeric, not polymeric.
Andrews
A Ballard
AB
Schlumberger-Doll Research, 36 Old Quarry Road, Ridgefield, CT 06877, USA. bandrews@slb.com
Guerra
Rodrigo E
RE
Mullins
Oliver C
OC
Sen
Pabitra N
PN