Flocculation behavior of asphaltenes in solvent/nonsolvent systems

J. A. Östlund*, J. E. Löfroth, K. Holmberg, M. Nyden

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Diffusion coefficients of asphaltenes dissolved in two aromatic (solvents, toluene-d8 or ethylbenzene-d10, were measured with the pulsed-field gradient spin echo nuclear magnetic resonance (PFG-SE NMR) technique upon addition of flocculant (pentane-d12 or heptane-d16). It was observed that the change in the diffusion coefficients, as a function of amount of added flocculant, was small in the concentration interval studied (up to 30 wt% alkane). Complementary kinetic flocculation studies were made at alkane additions above 55 wt%. The initial change in turbidity upon the addition of alkane was measured with an UV-VIS spectrophotometer. The obtained stability ratio, W, showed that asphaltenes were least stable in the ethylbenzene-pentane system and most stable in the toluene-heptane system. These findings were in agreement with the PFG-SE NMR. When combining the results from the two different techniques it appeared as if there was a dramatic increase in flocculation above a certain "threshold concentration" of added alkane. Furthermore, the flocculation appeared to be reaction controlled until as much as 63 wt% of n-pentane or, alternatively, 68 wt% of n-heptane had been added to the systems, after which the flocculation became primarily diffusion controlled. Finally, careful relaxation measurements showed that the asphaltenes displayed two distinctly different transverse (T2) relaxation times (most probably averages), one at 0.6 ms and the other at 7 ms.

Original languageEnglish
Pages (from-to)150-158
Number of pages9
JournalJournal of Colloid and Interface Science
Issue number1
Publication statusPublished - 1 Sep 2002
Externally publishedYes


  • Aggregation
  • Asphaltenes
  • Diffusion
  • Flocculation
  • Kinetic
  • Precipitation
  • Pulsed-field gradient spin echo nuclear magnetic resonance
  • Stability


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