Micellar solubilization of petroleum fractions by heavy alkylbenzene sulfonate surfactant

Advancements in Characterization Techniques for Microemulsions: From Molecular Insights to Macroscopic Phenomena

Microemulsions are thermodynamically stable, optically isotropic, transparent, or semi-transparent mixed solutions composed of two immiscible solvents stabilized by amphiphilic solutes. This comprehensive review explores state-of-the-art techniques for characterizing microemulsions, which are versatile solutions essential across various industries, such as pharmaceuticals, food, and petroleum. This article delves into spectroscopic methods, nuclear magnetic resonance, small-angle scattering, dynamic light scattering, conductometry, zeta potential analysis, cryo-electron microscopy, refractive index measurement, and differential scanning calorimetry, examining each technique's strengths, limitations, and potential applications. Emphasizing the necessity of a multi-technique approach for a thorough understanding, it underscores the importance of integrating diverse analytical methods to unravel microemulsion structures from molecular to macroscopic scales. This synthesis provides a roadmap for researchers and practitioners, fostering advancements in microemulsion science and its wide-ranging industrial applications.

High-performance arabinoglucuronoxylan-based biosurfactants for oily sludge separation

Arabinoglucuronoxylan (AGX), an important carbohydrate polymer in lignocellulosic biomass, contains many functional groups. It has excellent amphiphilic modification properties and has potential application in the separation of oily sludge. In this study, a simple strategy for producing high-performance AGX-based biosurfactants was studied and the raw AGX was extracted from bamboo by hydrothermal treatment. AGX-based biosurfactants with amphiphilic structure were produced by AGX and dodecanal succinic anhydride (DDSA) using rapid homogeneous esterification reactions in deep eutectic solvents (DES). This resulted in a significant reduction in the surface tension of the water from 72.32 to 29.76 mN·m^-1. These parameters are similar to those achieved using sodium dodecyl sulfate (SDS), a widely employed synthetic surfactant. Other physicochemical properties, including foamability, emulsification activity, stability, solubilization, and detergency were significantly improved compared to the unmodified AGX, demonstrate that AGX-based biosurfactants are promising detergents for oily sludge remediation and oil recovery. The results provide a new pathway for high value utilization of arabinoglucuronoxylan.

A mechanism study of sodium dodecylbenzene sulfonate on oil recovery: effect of branched chain structure

The effects of the branched structures of SDBS molecules on oil recovery are investigated by molecular dynamics method. The relative density of oil molecules shows that SDBS molecule with benzene ring located near the center of alkyl chain has the best effect on oil displacement. Dynamic trajectories show that the water and SDBS molecules gradually occupy the calcite surface and replace the oil droplets. In this process, more water molecules gather nearby the polar groups of SDBS, indicating that the polar group has a significant effect on the water infiltration and the formation of water channels. Contact angle between SDBS molecule and calcite surface indicates that compared to straight chains, the branched structure tends to spread on the calcite interface. Moreover, adsorption energies of the simulation systems further prove that as the aromatic ring is closer to the middle of the alkyl chain, the oil displacement effect is better.

In situ micro-emulsification during surfactant enhanced oil recovery: A microfluidic study

HYPOTHESIS

It is generally believed that the improved efficiency of surfactant enhanced oil recovery (EOR) comes from ultra-low interfacial tension (IFT) between oil and surfactant solution owing to the formation of middle-phase microemulsion. However, hindered visibility in underground porous media prevents direct observation of in situ generation of middle-phase microemulsion during surfactant flooding. Thus, direct visualization of the process is vital, and could clarify its contribution to EOR.

EXPERIMENTS

Micro-emulsification of a displacing fluid containing sodium 4-dodecylbenzenesulfonate and alcohol propoxy sulfate with model oil was investigated. Phase diagrams were drawn using salinity scans, and the influence of polymer on emulsification was analyzed. Micro-emulsification was monitored through in situ fluorescent tagging via 2D-microfluidics and ex situ visualization via cryo-electron microscopy and small angle X-ray scattering. Its contribution to the oil recovery factor was quantified by measuring the volume of each phase in the eluates.

FINDINGS

On-chip experiments indicated that in situ micro-emulsification occurred when the prescreened surfactant solution flowed in contact with trapped oil. The aqueous phase initially invaded the residual oil, forming a low mobility microemulsion. This microemulsion was then diluted by subsequent displacing fluid, forming a new driving fluid that caused ultra-low IFT in the trapped oil downstream. Under the synergistic effect of micellar solubilization and trapped-oil mobilization, the recovery factor could be increased by up to 40% over waterflooding and 43% on polymer inclusion in the formulation.

Computational Study on the Microscopic Adsorption Characteristics of Linear Alkylbenzene Sulfonates with Different Chain Lengths on Anthracite Surface

In order to explore the influence of different lengths of hydrophobic carbon chains on the diffusion characteristics of surfactants on the surface of anthracite, six linear alkyl benzene sulfonates with different hydrophobic carbon chain lengths were selected (mC, m = 8, 10, 12, 14, 16, 18; m represents the numbers of carbon atoms in the hydrophobic carbon chain), and molecular dynamics (MD) simulations were adopted. Models of surfactant-anthracite, surfactant-graphite layer, and water-surfactant-anthracite were constructed. After analyzing a series of properties such as adsorption energy, diffusion coefficient, radial distribution function (RDF), and hydrophobic tail order parameters, it was found that 12C had the highest adsorption strength on the surface of anthracite; the reason was that 12C had the highest degree of aggregation near the oxygen-containing functional groups on the surface of anthracite. Further studies had found that the hydrophobic tail chain of 12C had the strongest isotropy. The study fills the gap in the systematic study of the diffusion characteristics of linear alkylbenzene sulfonates (LAS) with different chain lengths on the surface of anthracite, enriches and develops the basic theory of coal wettability, and also provides technical ideas for the design of new surfactants and new dust suppression agents.

Microscopic Diffusion Characteristics of Linear Alkylbenzene Sulfonates on the Surface of Anthracite: The Influence of Different Attachment Sites of Benzene Ring in the Backbone

In order to explore the effect of the attachment site of the benzene ring in the backbone of the surfactant on its diffusion characteristics on the surface of anthracite, the molecular dynamics simulation method was used, and the four isomers (m-C16, m = 2,4,6,8; m represents the attachment site of the benzene ring in the backbone) of sodium hexadecyl benzene sulfonate (SHS) were selected. Binary models of surfactant/anthracite, surfactant/graphene modified by oxygen-containing functional groups, and a ternary model of water/surfactant/anthracite were constructed. By analyzing a series of properties such as interaction energy, contact surface area, relative concentration distribution, radial distribution function, hydrophobic tail chain order parameter, etc., it is concluded that the adsorption strength of 4-C16 on the surface of anthracite is the highest; the reason is that 4-C16 has the highest degree of aggregation near the oxygen-containing functional groups on the surface of anthracite. Further investigations find that 4-C16 can be densely covered on the ketone group, and the longer branch chain of 4-C16 has the highest degree of order in the Z-axis direction.