Delayed Aggregation of Asphaltenes in the Presence of Alcohols by Dynamic Light Scattering

Structure of an n-heptane asphaltene obtained from atmospheric residue of crude oil has been analyzed using ultraviolet, infrared, and nuclear magnetic resonance (H-1 and C-13) spectroscopy and elemental analysis. The molecular weight of asphaltene was deduced by GPC (M-n 3372gmole(-1)). Asphaltene exhibited H/C ratio of 0.905 and high sulfur content, being of thioether, thiophene rings or other C-S-C structures. Detailed ultravioletspectra of asphaltene recognized its construction as sets of fused aromatic rings, with each set having an average of three rings, thus, deducing a model structure. The onset point and aggregation behavior of asphaltene have been studied in the presence of alcohols(n-C6OH, n-C7OH, n-C8OH and n-C10OH) versus n-heptane, n-hexane and n-pentane as precipitating agents. The aggregation study has been carried out using dynamic light scattering. N-heptanol and n-hexanol showed the most delaying influence for the asphaltene aggregation versus n-heptane, n-hexane and n-pentane, respectively. Similarly, the aggregation behavior explored by dynamic light scattering showed that the use of n-hexanol and n-heptanol results in aggregate sizes that were smaller than those obtained when using n-octanol and n-decanol.