The Study on Interactions Between Stabilizers and Asphaltenes

Asphaltene stabilizers are the main means to inhibit the flocculation and sedimentation of asphaltenes in crude oil exploitation, transportation, and refining operations. In this work, the interactions between asphaltenes and 2-dodecyl benzene sulfonic acid, 4-dodecyl benzene sulfonic acid, 4-dodecyl aniline, 4-dodecyl phenol, polyisobutylene succinic imide benzene boric acid and polyisobutylene succinic imide benzene sulfonic acid were studied by XPS, XRD, DLS, TEM and SEM methods. The aggregation behavior of asphaltenes in the absence and presence of stabilizers was characterized by analyzing asphaltene's particle size, surface composition, and aggregate microstructure. It was observed that the interactions between asphaltene and stabilizers decreased asphaltene aggregate size in solution, and that the polymeric stabilizer with an acidic group was superior to the small-molecule stabilizer with an acidic group, but both better than chemicals with basic groups. It was found that stabilizer adsorption on asphaltenes affected the O, N, S contents of asphaltene surface and prompted formation of protonated pyridinic N+ and nitrogen-oxide -R-N+-O-, which further revealed that an acid-base reaction was the most effective at stabilizing asphaltene-stabilizer complexes, followed by pi-pi interactions and hydrogen bonds. We also found that the synergistic effects of pi-pi and acid-base reactions stimulated the transformation of 2-dodecyl benzene sulfonic acid adsorbed on asphaltene from the vertical state at low concentrations to the tiled arrangement at high concentrations. XRD results showed that adsorption of stabilizers on asphaltene increased the distance of asphaltene aromatic sheets and decreased the aggregation number of asphaltene to below the critical aggregation number of asphaltene tactoids.