A practical method for determining the surface charge and point of zero charge of asphaltenes

Asphaltenes aggregates can be treated as colloids, and it point of zero charge could be measured to analyse their charge surface and their potential interactions with dispersants agents. It means that pH-dependent effect could promote or block their electrostatic interaction with its environment. Bearing this in mind, it was proposed and developed a feasible way to evaluate chemical affinity between asphaltenes and surfactants, knowing the asphaltenes aggregates chemical charge and applying a molecule bearing the corresponding countercharge, to obtain a favourable interaction (inhibiting aggregation/precipitation). Then, we studied the solid surface charges of nine Colombian asphaltenes, analysing their point of zero charge plot and values by the salt addition method, and elucidating their acid–base character. All the asphaltenes had a negative summatory of ΔpH with values that were from -0.39 (AK12, less acidic character) to -7.51(SR, more acidic character). The PZC analysis allowed us to identify and observe that the dispersion with caprylic acid was more effective. Thus, these fundamental descriptors can be important factors looking for understanding several challenges in oil and gas industry attributed to the asphaltenes, such as emulsion stability and flow assurance control.