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

Abstract

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 nheptane), temperature (35-90 degrees C), SOR (3-20, vol/vol), surfactants, and surfactant concentration (0.5-2.0 wt % of the feedstock). As a result, the zeta potential with sodium dodecyl sulfonate (SDS) was shown to decrease, while the zeta potential of pitch with cetylpyridinium chloride (CPCI) 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 zeta potential and asphaltene content between SDS and CPCI can be explained by the adsorption mechanism.