Effect of Ionic Surfactants on Improving Deasphalting Selectivity in a Nonpolar System

To reduce the amount of solvent used in the solvent deasphalting process, this study investigated the possibility of improving deasphalting selectivity at a low solvent/oil ratio (SOR) by modifying the stability of the asphaltene colloidal dispersion with ionic surfactants. To do this, an experiment was conducted by changing the solvent types (n-pentane and n-heptane), temperature (35-90 °C), SOR (3-20, vol/vol), surfactants, and surfactant concentration (0.5-2.0 wt % of the feedstock). As a result, the ζ potential with sodium dodecyl sulfonate (SDS) was shown to decrease, while the ζ potential of pitch with cetylpyridinium chloride (CPCl) rose, as compared to those without surfactant. Also, the difference is bigger at a low SOR than at a high SOR. Finally, it was confirmed that, for SDS, the asphaltene content rose about 6% for the incremental 3% rise of pitch yield, while for CPCI, the asphaltene content rose 9-10% for the incremental 1.8% rise of the pitch yield, at the same time. The different movement of ζ potential and asphaltene content between SDS and CPCl can be explained by the adsorption mechanism.