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 γ (6.8 m Nm - 1, toluene−0.1 N HCl), whereas for B, these values were M n = 1200 Da, f a = 20%, and γ = 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%, γ = 20.9 m Nm - 1 ).