Isolation and characterization of low and high molecular weight acidic compounds from Cerro Negro extraheavy crude oil.: Role of these acids in the interfacial properties of the crude oil emulsions

Two acidic samples, A and B, were isolated from Cerro Negro extraheavy crude oil. Sample A has a relatively low number average molecular weight (M-n = 480 Da), low aromaticity (f(a) = 15.2%), and low gamma (6.8 m Nm(-1), toluene-0.1 N HCl), whereas for B, these values were M-n = 1200 Da, f(a) = 20%, and gamma = 14.8 m Nm(-1). These values could be compared to those for Cerro Negro asphaltenes under the same conditions (M-n= 5000, in toluene by VPO, f(a) = 47%, gamma = 20.9 m Nm(-1)).