Oil/Water Nanoemulsions: Activity at the Water–Oil Interface and Evaluation on Asphaltene Aggregates

Abstract

Oil-in-water (O/W) nanoemulsions based on nonionic ethoxylated polymeric surfactants were prepared and evaluated for demulsification of water/oil emulsions and model asphaltene emulsions. The nanoemulsions were prepared using two nonionic ethoxylated polymeric surfactants with different numbers of ethylene oxide units in their chains and the solvents xylene and Solbrax as the oil phase, at different concentrations. The interfacial properties of the different systems applied in the demulsification process were evaluated in model emulsions and were correlated with their ability and/or speed of diffusion to the interface. Tests of asphaltene dispersion/flocculation were performed to evaluate whether the nanoemulsions change the aggregation state of asphaltenes during the demulsification process. The results of gravitational separation tests showed that the new nanoemulsion formulations studied can be applied to demulsify water/oil emulsions. Both the type of polymeric surfactant used and the type and content of the oil phase in the nanoemulsions had a significant influence on the efficiency and speed of breaking down emulsions. The efficiency was related to the surfactant hydrophilicity and the solubility parameter of the oil phase, which also affected the size of the asphaltene aggregates.

Controlled releases of asphaltene inhibitors by nanoemulsions

“…In the case of using blank NE, NEs in this study consist of three components, which are: oil phase (xylene), surfactants (Tween 80 and SDS) and water. The first systematic study of using NE for demulisifacation of water/oil emulsions or asphaltene emulsions was reported by Souza et al [19,20]. In order to understand the effect of blank NE on asphaltene precipitation, we focus on the effect of each component in the NEs on asphaltene particles.…”

“…The second component in DBSA NE may affect asphaltene precipitation is xylene, which is one of the most effective solvents for asphaltenes [48]. The third component is surfactant; Souza et al [19] suggested that the diffusion of the surfactant molecules to the water/oil interface can reduce the aggregation size of the asphaltene. Therefore, in this study, it was found that the use mixed surfactants (Tween 80 and SDS) in DBSA NE can provide good interactions with asphaltene molecules.…”

“…DBSA NEs shows a strong tendency to migrate and adsorb at the water/oil interface due to the large surface area of the droplets and the presence of ionic / non-ionic surfactants,, which reduces the IFT to 3.7 mN m −1 . [19,20]. This interfacial activity explains the effectiveness of DBSA NE in controlling asphaltene precipitation, as it allows the displacement of asphaltenes from the water−oil interface, thereby stabilizing the asphaltene in solution.…”

“…An attempt to further reduce the amount of scale inhibitors has been done by Zhang et al, in 2016 [18] by using reverse micelles as nonaqueous scale inhibitor delivery vehicles for oilfield mineral scale control. In addition, a systematic study of the effectiveness of using oil-in-water nanoemulsions in breaking down asphaltene emulsions was reported by Souza et al [19,20].…”

Kinetic Study of Controlled Asphaltene Inhibitor Release from Nanoemulsions

“…Using high concentrations of inhibitor tends to produce self-associations in the bulk rather than adsorption on asphaltene, reducing their effectiveness [11,12]. More recently, a considerable work has grown up around the use of oil/ water nanoemulsions (NEs) in breaking down asphaltene emulsions [13,14,15]. However, efficient methods of enhancing long-term asphaltene stability with reduced AI amount are still much demanded.…”