Selective dissociation of benzoic acid on carbonate surfaces: A density functional theory perspective

Abstract

The adsorption of benzoic acid (BA) and the consequent benzoate (B) formation are fundamental processes responsible for wettability alteration on carbonate surfaces in the carbonate-oil interface. However, mixed wettability due to the occurrence of both Ca2+ and Mg2+ ions leads to current not well-understood changes in chemical properties related to BA and B formation. Therefore, we investigated by Density-Functional Theory a dissociative adsorption mechanism through different parallel and perpendicular conformations of BA and B on the calcite and dolomite (101-4) surfaces. In particular, BA is stably adsorbed on both carbonate surfaces main due to charge distribution between the carboxyl group and the surface cations. Furthermore, we find that the hydroxyl group tends to be available on dolomite rather than on calcite, being experimentally supported as the source for the possible BA selective adsorption. The calculated dissociation energy barrier also shows that dolomite surface displays the ideal condition just for a possible kinetic dependence upon the presence of water molecules. Therefore, we concluded that the mixture of calcite and dolomite portions in the reservoir surface could indeed work together upon the B formation. Accordingly, our results provide fundamental insights for the dissociation of acid oil components on mixed carbonate surfaces.