Layer-by-Layer Assembled Film of Asphaltenes/Polyacrylamide and Its Stability of Water-in-Oil Emulsions: A Combined Experimental and Simulation Study

Abstract

Emulsions with interface-active components at the water/oil (w/o) interface are of fundamental and practical interest in many fields. Here we investigate the interfacial films of asphaltenes and asphaltenes/polyacrylamide (PAM) at the w/o interface of water-in-crude oil emulsions. With the combination of the dissipative particle dynamics simulation and experimental observation, the molecular interactions of asphaltenes and asphaltenes/PAM at the w/o interface are extensively analyzed. We show that the rigid mechanical film of asphaltenes originates from a rigid structure of polycyclic aromatic hydrocarbons (PAHs) and the π–π bonding interactions between the PAHs of asphaltenes, and at a higher concentration of asphaltenes, the nanoaggregates of asphaltenes, acting as a space fortress at the w/o interface, make the drop–drop coalescence more difficult. In addition, a layer-by-layer assembled architecture film of asphaltenes/polyacrylamide formed at the w/o interface is identified, and we observe that the inner layer is composed of PAM with a network structure and the outer layer is composed of rigid asphaltenes. While the rigidity and stability of this film are attributed to the viscoelasticity and rheology of PAM and the “synergy effect” between asphaltenes and PAM, its presence greatly enhances the stability of water-in-oil emulsions. We further conclude that PAM with higher concentrations and molecular weights can generate a more ordered network structure, leading to a more stable asphaltenes/PAM film at the w/o interface. This combined study provides helpful insight into the demulsification of water-in-oil emulsion.

Mesoscopic probes in asphaltenes nanoaggregate structure: from perpendicular to paralleled orientation at the water-in-oil emulsions interface

“…9,12 In our previous studies, it was found that the rigid mechanical lm of asphaltenes originates from (i) rigid structure of polycyclic aromatic hydrocarbons (PAHs) and (ii) the pp bonding interactions between the PAHs of asphaltenes. 13 Moreover, a layer-by-layer assembled architecture lm was formed at the W/O interface when the system in presence of polyacrylamide (PAM). This layer-by-layer assembled architecture lm exhibits great viscoelasticity and rheology properties which enhances the stability of water-in-oil emulsions.…”

“…Though a large number of the aforementioned studies have been reported, a further understanding of the nanoaggregate structure and emulsion stability of asphaltenes at the O/W interface is still needed, especially at mesoscopic scale. 13 In this work, we employed dissipative particle dynamics (DPD) simulations for studying the nanoaggregate structures of asphaltenes at water/toluene interface with the mesoscopic scale. 13,22 DPD simulations method are an excellent technology for the simulation of coarse-grained systems over considerable length and time scales up to the mesoscopic scale.…”

“…13 In this work, we employed dissipative particle dynamics (DPD) simulations for studying the nanoaggregate structures of asphaltenes at water/toluene interface with the mesoscopic scale. 13,22 DPD simulations method are an excellent technology for the simulation of coarse-grained systems over considerable length and time scales up to the mesoscopic scale. 13,20 DPD simulations have been performed to study static and dynamic interfacial phenomena and the self-assembly behavior of amphiphilic molecule at the interface, 20,21 including asphaltenes at liquid/ liquid interface 22 and the solid/liquid interface.…”

Networked Nanogels from Self‐Assembly of End‐Functionalized Polymers at the Vapor/Liquid Interface: Molecular Dynamics Simulations

“…Moreover, the values of these peaks increase with increase in the surface coverage of the polymers. According to the density profiles, the self‐assembled monolayer thickness can be calculated by the “90‐10” criterion, which is defined as the distance along the interface over the solvent densities distributed from 90% to 10% of their bulk value. The self‐assembled monolayer thickness of the end‐functionalized polymer at the vapor/liquid interface is 3.84σ, 4.74σ, 5.46σ when the surface coverage of polymer is φ = 3.02%, φ = 4.54%, and φ = 6.81%, respectively.…”

Synthesis and performances for treating oily wastewater of polyether copolymers based on polyethyleneimine

“…The oil content decreased with increasing ratio of EO/PO at the same time. Indigenous components of crude oil such as asphaltenes, resins, naphthenic acids, and fine solids play important roles in stabilizing the oily wastewater, and the contents of EO in PEI99‐54 and PEI99‐11 were higher than the contents in the other corpolymers, which made PEI99‐54 and PEI99‐11 have stronger ability to remove the natural surfactants and the other indigenous components from the interface . Therefore, PEI99‐54 and PEI99‐11 showed a better performance in the treatment of oily wastewater.…”