Asphaltene Subfractions Responsible for Stabilizing Water-in-Crude Oil Emulsions. Part 3. Effect of Solvent Aromaticity

Abstract

Whole asphaltenes (WA) were fractionated by the E-SARA method according to their adsorption characteristics at oil–water interfaces from either toluene or heptol solutions. Heptol, a mixture of n-heptane and toluene at a 1:1 volume ratio, is a less aromatic solvent than toluene. The effect of solvent aromaticity on the composition of resulting asphaltene subfractions at oil–water interfaces was studied to determine the key functional groups that are critical to the asphaltene-induced stabilization of water-in-oil (W/O) petroleum emulsions. The interfacially active asphaltenes (IAA) were extracted as materials irreversibly adsorbed onto emulsified water droplets, while the asphaltenes remaining in the oil phase were considered as remaining asphaltenes (RA). Although toluene-extracted interfacially active asphaltenes (T-IAA) accounted for only 1.1 ± 0.3 wt % of WA, this subfraction of asphaltenes exhibited a greater interfacial activity and formed more rigid films at the oil–water interface than IAA extract...