The Influence of Some Interfacial Properties of PEO-b-PPO Copolymers on Dewatering of Water-in-Oil Asphaltene Model Emulsions

Abstract

Three different macromolecular structures of poly(ethylene oxide-b-propylene oxide) copolymers, used in formulations of commercial demulsifiers for breaking water-in-crude oil emulsions, were investigated. The interfacial activity (), the lower interfacial tension (m), the critical micelle concentration (CMC), the interfacial concentration (Γ) and the molecular area (A) adsorbed at the interface of the surfactant solutions were evaluated. These results were correlated to surfactant performance in coalescing three different asphaltene model emulsions. The PEO-b-PPO commercial demulsifiers, that were capable to dewater asphaltene model emulsions, exhibited interfacial activity to the oil-water interface, reduced the interfacial tension to low values, reached the CMC at low concentration and presented low molecular area adsorbed at the interface.

Molecular Destabilization Mechanism of Asphaltene Model Compound C5Pe Interfacial Film by EO-PO Copolymer: Experiments and MD Simulation

“…C5Pe is a typical asphaltene model that was reported in several studies. − Xylenes model was based on the proportion of each component (60% of m -xylene, 20% of o -xylene, and 20% of p -xylene). The EO-PO copolymer was modeled as a star-like structure with three arms (Figure ). Glycerol was used as the base compound with 35% of EO percent in total weight.…”

“…Therefore, we aim to reveal the molecular demulsification mechanism by both experiments and molecular dynamics (MD) simulations. EO-PO copolymer was used as the demulsifier because it has been extensively investigated 18,20,24,25 and reported as an effective additive in breaking asphaltene/bitumen-stabilized water-in-oil emulsions. 20,21 As asphaltenes are merely a solubility class having undefined chemical composition and molecular structure, different asphaltene model compounds have been used as models in MD simulation.…”

“…EO-PO copolymer was used as the demulsifier because it has been extensively investigated 18,20,24,25 and reported as an effective additive in breaking asphaltene/bitumen-stabilized water-in-oil emulsions. 20,21 As asphaltenes are merely a solubility class having undefined chemical composition and molecular structure, different asphaltene model compounds have been used as models in MD simulation. 26−29 C5Pe is a suitable model compound, as it shows interfacial activities very similar to those of asphaltenes.…”

“…It is widely accepted that the emulsion stability is due to the formation of a mechanically strong, rigid, and viscoelastic interfacial film by the accumulation of surface-active components, such as asphaltenes, resins, naphthenic acids, and inorganic solids from the bitumen or crude oil. − These components stabilize the emulsion by preventing the direct contact between droplets or the drainage of the thin film between them. , Asphaltenes are believed to be the main components that contribute to the formation of the rigid film, which stabilizes W/O emulsions. − For efficient breakup of the W/O emulsions, the use of demulsifier has been regarded as an economical and efficient method that is widely used in the petroleum industry. , Modern demulsifiers are usually mixtures of surface-active macromolecular chemicals, such as acid- or base-catalyzed phenol-formaldehyde polymers, ethoxylated and/or propyloxylated polyamines, diepoxides, polyols, and silicone copolymers. − Most of the active ingredients in the chemicals used as demulsifiers are copolymers of ethylene oxide (EO) and propylene oxide (PO) of different molecular mass and EO-to-PO ratio. − …”

“…Therefore, we aim to reveal the molecular demulsification mechanism by both experiments and molecular dynamics (MD) simulations. EO-PO copolymer was used as the demulsifier because it has been extensively investigated ,,, and reported as an effective additive in breaking asphaltene/bitumen-stabilized water-in-oil emulsions. , As asphaltenes are merely a solubility class having undefined chemical composition and molecular structure, different asphaltene model compounds have been used as models in MD simulation. − C5Pe is a suitable model compound, as it shows interfacial activities very similar to those of asphaltenes. Nenningsland et al have extensively investigated factors affecting the emulsion stability by an array of techniques and concluded that the formation of a rigid network/layer of polycyclic aromatic compounds, such as asphaltene model compound C5Pe, was responsible for enhancing the emulsion stability.…”