Multiscale modeling of mass transfer and adsorption in liquid-liquid dispersions. 2. application to calcium naphthenate precipitation in oils containing mono- and tetracarboxylic acids

Abstract

A dynamic multicomponent mass transport model is constructed and solved to determine the interfacial composition and bulk phase concentrations of surfactant mixtures containing a synthetic tetracarboxylic acid (BP10) and decanoic acid (DA) for water droplets dispersed in oil. The transport model employs a molecular mixed monolayer adsorption model that was parametrized by MD simulation and interfacial tension experiments in part 1 [Kovalchuk, K.Riccardi, E.Grimes, B. A. Ind. Eng. Chem. Res. 2014, 10.1021/ie501295k]. The model accounts for oil–water partitioning, the pH determined dissociation state of the acids, and micelle formation in the water phase. Since the interfacial concentration of tetracarboxylic acids in crude oil emulsions is hypothesized to influence the extent of fouling by calcium naphthenate precipitation, trends for the amount of calcium naphthenate precipitate formed in the system can be predicted as a function of the water volume fraction for various BP10:DA concentration ratios and drop sizes. The model provides an experimentally testable prediction that could support the hypothesis that calcium naphthenate precipitation is an interfacial reaction and have implications on petrochemical and engineering based inhibition strategies. The modeling framework outlined in parts 1 and 2 of this work is well-suited to studying interfacial phenomena in well-defined model systems employing a library of synthetic and purified indigenous crude oil surfactants.