The performance of several extended surfactants as water-in-crude oil emulsion breakers was evaluated using two criteria: (1) the demulsifier dose required (C D*) to attain the minimum stability at the so-called optimum formulation, and (2) the corresponding low minimum stability value. These surfactants were found to behave in the same way as typical commercial demulsifiers do; i.e., they require a lower dose C D* when their hydrophilicity is slightly greater. The reported data for a dozen different extended surfactants indicate how the two performance indices are altered by changing the structure characteristics, such as the propylene oxide number, the ethylene oxide number, and the ionic polar group (carboxylate, sulfate, phosphate). The best performance as a demulsifier seems to depend on the proper combination of these structures to attain a well-fitting compromise.

Three different cases were selected to study the effect of physicochemical formulation on interfacial rheology properties of surfactant-oil-water (SOW) systems by increasing the complexity of the system from a basic case. This was performed by changing the normalized hydrophilic-lipophilic deviation (HLD N ) to attain the optimum formulation at HLD N = 0. Two types of SOW systems were studied: the first one used an ionic surfactant with a salinity scan, and the second one a mixture of two nonionic surfactants in a formulation scan produced by changing their proportion. Both of them contained cyclohexane as a pure oil phase, without alcohol. Sec-butanol was then added as a co-surfactant with hardly any formulation influence on HLD N . The complexity in interfacial rheology was then increased by changing the oil to a light crude with low asphaltene content. The interfacial rheology is also reported for a realistic system with a high asphaltene content comprised of crude oil diluted in cyclohexane with a conventional surfactant and a commercial demulsifier. The findings confirm that at optimum formulation and whatever the scanning variable (salinity, average ethylene oxide number in the nonionic surfactant mixture, or surfactant/demulsifier concentration), the interfacial tension, and interfacial elastic moduli E, E 0 , and E 00 exhibit a deep minimum. These observations are related to the acceleration of the surfactant exchanges between the interface, oil, and water, near the optimum formulation. Several arguments are put forward to explain how these findings could contribute to the decrease in emulsion stability at HLD N = 0.Keywords Crude oil Á Asphaltenes Á Amphiphiles Á Interfacial rheology Á Formulation Á Emulsion stability Á HLD N

Asphaltenes tend to aggregate in different structures depending on the aromatic content of the oil phase. The different aggregates adsorb at the interface as some kind of lipophilic surfactant, which tends to stabilize water-in-oil emulsions. Hydrophilic demulsifier molecules are added to combine with asphaltenes until the optimum formulation is attained at HLD = 0, thus resulting in the emulsion instability. It is found that with the change of asphaltenic aggregate structure produced by the aromatic content of the oil, its surfactant-like effect at the interface is also altered. The performance of dehydration is significantly improved with only 5% of aromatic additive in the oil phase.

This work reviews the use of carbohydrates and their derivatives as renewable raw materials in the production of surfactants. Methods to attain state‐of‐the‐art carbohydrate‐derived surfactants are described. This includes surfactants widely used nowadays and others that have not yet transcended beyond the academic field. Given the abundance of hydroxyl groups in carbohydrates and the considerable quantity of different surfactant structures that can be generated during their synthesis, selectively obtaining a target product represents a challenge. Therefore, this work focuses on the platform chemicals available to synthesize biobased surfactants. The first part of the review comprises a brief introduction of simple and complex carbohydrates to better understand their chemistry. Then, a description of the processes to obtain biobased building blocks derived from carbohydrates according to the National Renewable Energy Laboratory (NREL, USA), and their usefulness in synthesizing surfactants is presented. This provides an organized inventory of the knowledge around the synthesis–production of surfactants from carbohydrate derivatives, emphasizing raw materials that could be inserted into the circular bioeconomy concept. Finally, the current industry trends and the potential role of biobased surfactants around new dioxane regulations are discussed.

Summary Asphaltene-stabilized water-in-oil (W/O) emulsions can cause severe problems during oil production and transportation. These emulsions are broken by adding a demulsifying agent at a suitable concentration (CD*) to obtain the optimal formulation, with minimal emulsion stability (stability*). Herein, we studied, from a phenomenological point of view, the performance of two demulsifiers on W/O emulsion breaking with high asphaltene content. A very simple polyethoxylated nonylphenol demulsifier (6EO) and a complex commercial demulsifier (COD) were studied. The influence of the chemical nature of the oil phase on the performance of the demulsifiers was evaluated. The emulsion stability* and CD* values of W/O systems of heavy crude oil diluted in cyclohexane (Systems A and B) were compared to W/O emulsions composed by a heavy crude oil diluted in heavy naphtha or in an aromatic synthetic crude oil as the oil phase (Systems C and D). The results show that demulsifier performance improves significantly when the crude oil is diluted in heavy naphtha and in aromatic synthetic crude oil, obtaining unstable W/O emulsions (rupture time of 10−2–10−1 minutes). In the latter cases, the CD* value is significantly lower and with a wide area of low emulsion stability compared to systems formulated with crude oil diluted in cyclohexane. The mechanisms that generate this type of behavior are discussed and strategies to increase performance and robustness analyzed.