Influence of Fatty-Alkylamine Amphiphile on the Asphaltene Adsorption/Deposition at the Solid/Liquid Interface under Precipitating Conditions

The ability of a fatty-alkylamine amphiphile to inhibit asphaltene adsorption/deposition, as well as its ability to disperse the asphaltene layers on stainless steel, was studied using a quartz crystal microbalance with dissipation (QCM-D). The experiments were performed both under good solvent conditions and above asphaltene precipitation onset. The adsorption/deposition of asphaltenes from model oil solution in xylene/n-hexane was found to strongly increase up to the asphaltene precipitation onset (i.e., ∼60−65 vol % n-hexane), with a 7−8 times increase of the adsorbed amount, compared with adsorption from xylene. Beyond the precipitation onset, the amount of asphaltene adsorbed/deposited decreases. Under both good solvent and precipitating conditions, the amphiphile was unable to form a protective layer on stainless steel to prevent asphaltene adsorption/deposition. However, the amphiphile exhibited an excellent ability to reduce asphaltene adsorption/deposition by 80−95 wt % when injected along with asphaltene solution. It is found that the interactions between asphaltenes and inhibitor that are responsible for the adsorption/deposition inhibitory action are not of an acid−base nature. Maximum inhibitory action in minimizing the asphaltene adsorption/deposition was observed corresponding to a molar ratio (amphiphile/asphaltenes) of ∼0.10, despite this molar ratio being insufficient to prevent asphaltene precipitation. Similarly, the amphiphile also displayed an ability to remove 90−95 wt % of asphaltenes already adsorbed/deposited on stainless steel under precipitating conditions, thereby showing its effectiveness as both an asphaltene inhibitor (AI) and an asphaltene dispersant (AD) under good solvent conditions, as well as precipitating conditions