Middle-phase Microemulsion Research Articles

Laundry Detergency of Solid Non-Particulate Soil Using Microemulsion-Based Formulation.

Laundry detergency of solid non-particulate soil on polyester and cotton was investigated using a microemulsion-based formulation, consisting of an anionic extended surfactant (C12,13-4PO-SO4Na) and sodium mono-and di-methyl naphthalene sulfonate (SMDNS) as the hydrophilic linker, to provide a Winsor Type III microemulsion with an ultralow interfacial tension (IFT). In this work, methyl palmitate (palmitic acid methyl ester) having a melting point around 30°C, was used as a model solid non-particulate (waxy) soil. A total surfactant concentration of 0.35 wt% of the selected formulation (4:0.65 weight ratio of C12,13-4PO-SO4Na:SMDNS) with 5.3 wt% NaCl was able to form a middle phase microemulsion at a high temperature (40°C),which provided the highest oil removal level with the lowest oil redeposition and the lowest IFT, and was much higher than that with a commercial detergent or de-ionized water. Most of the detached oil, whether in liquid or solid state, was in an unsolubilized form. Hence, the dispersion stability of the detached oil droplets or solidified oil particles that resulted from the surfactant adsorption played an important role in the oil redeposition. For an oily detergency, the lower the system IFT, the higher the oil removal whereas for a waxy (non-particulate) soil detergency, the lower the contact angle, the higher the solidified oil removal. For a liquefied oil, the detergency mechanism was roll up and emulsification with dispersion stability, while that for the waxy soil (solid oil) was the detachment by wettability with dispersion stability.

Modeling micelle formation and interfacial properties with iSAFT classical density functional theory.

Surfactants reduce the interfacial tension between phases, making them an important additive in a number of industrial and commercial applications from enhanced oil recovery to personal care products (e.g., shampoo and detergents). To help obtain a better understanding of the dependence of surfactantproperties on molecular structure, a classical density functional theory, also known as interfacial statistical associating fluid theory, has been applied to study the effects of surfactant architecture on micelle formation and interfacial properties for model nonionic surfactant/water/oil systems. In this approach, hydrogen bonding is explicitly included. To minimize the free energy, the system minimizes interactions between hydrophobic components and hydrophilic components with water molecules hydrating the surfactant head group. The theory predicts micellar structure, effects of surfactant architecture on critical micelle concentration, aggregation number, and interfacial tension isotherm of surfactant/water systems in qualitative agreement with experimental data. Furthermore, this model is applied to study swollen micelles and reverse swollen micelles that are necessary to understand the formation of a middle-phase microemulsion.

Additive Effects on the Phase Behavior of Cationic Surfactant ([C16mim]Br) Stabilized Hydrophobic Ionic Liquid Based Middle-Phase Microemulsions

The e-β fishlike phase diagram of the system [C16mim]Br/[Omim]Tf2N/water was constructed in the presence of different additives (alcohol and inorganic salt). From the diagram some additive-dependent characteristic physicochemical parameters were obtained. Results show that with the increase of the alkyl chain length of alcohols, the solubility of the alcohol in [Omim]Tf2N, and the optimum solubilization parameter (SP*) decrease, while the maximum alcohol width (△e) for the phase inversion and the mass fraction of the alcohol in the balanced interfacial film (Ain) increase. For inorganic salts, an increase in [NaCl], or an increase of the radius of halides (X–) at constant [NaX], or the substitution of the divalent anion SO42– by the same molar concentration of monovalent anion Cl– makes both SP* and △e increase, but Ain decrease. Overall, the alcohol effect on the phase behavior of the microemulsion is greater than the salt effect, and the composition effect of an inorganic salt is greater than the concen...

Green enhanced oil recovery (GEOR)

Green enhanced oil recovery (GEOR) is a chemical enhanced oil recovery (EOR) method involving the injection of specific green chemicals (surfactants/alcohols/polymers) that effectively displace oil because of their phase-behaviour properties, which decrease the interfacial tension (IFT) between the displacing liquid and the oil. In this process, the primary displacing liquid slug is a complex chemical system called a micellar solution, containing green surfactants, co-surfactants, oil, electrolytes and water. The surfactant slug is relatively small, typically 10% pore volume (PV). It may be followed by a mobility buffer such as polymer. The total volume of the polymer solution is typically ~1 PV. This study was conducted to examine the effectiveness of the combination of microbial by-products Bacillus subtilise strain JF-2 bio-surfactant and alcohol in recovering residual oil. It also considered whether bio-surfactant capability could be improved by blending it with non-ionic green surfactant. The study consisted of a phase behaviour study, IFT measurement and core-flooding experiments. In the phase behaviour study, it was found that 0.5% alkyl polyglycosides (APG) and 0.5–1.00% of butanol at 2% NaCl gave stable middle phase micro-emulsion. Non-ionic (APG 264) and anionic (bio-surfactant) mixtures are able to form stable middle phase micro-emulsion. Based on IFT reduction, two low concentrations (40 and 60 mg/l) of JF-2 bio-surfactant were identified where IFT values were low. The bio-surfactant and butanol formulation produced a total ~39.3% of oil initially in place (OIIP).

Preparation of CO2-responsive emulsions with switchable hydrophobic tertiary amine

Abstract We prepared a CO 2 responsive emulsion by using switchable hydrophobic tertiary amine, N , N -dimethylcyclohexylamine (DMCHA). DMCHA exhibits little miscibility with water in the absence of CO 2 , but shows a complete miscibility with water in the presence of CO 2 . DMCHA converts to water-soluble bicarbonate salts upon treatment with CO 2 , which could induce the ionic strength increase of aqueous phase. Together with paraffin oil, DMCHA was used to prepare CO 2 responsive O/W emulsions with a conventional surfactant, sodium dodecyl benzene sulfonate (SDBS), as the emulsifier. Emulsions containing DMCHA in paraffin oil were more stable than those without DMCHA, as a result of electrostatic interactions between a small fraction of protonated DMCHA and SDBS, confirmed by surface tension and 1 H NMR measurements. However, when exposed to CO 2 most of the paraffin oil and water separate from the emulsion with formation of a middle phase microemulsion. More significantly, DMCHA could be separated from the lower water phase upon removal of CO 2 and recycled.

Self-division of a mineral oil–fatty acid droplet

Self-division of a mineral oil–fatty acid droplet placed in an alkaline solution was investigated. The initially homogeneous mineral oil droplet containing various amounts of 2-hexyldecanoic fatty acid underwent a division process resulting in the formation of two droplets. One formed (‘daughter’) droplet contains middle-phase microemulsion (surfactant-rich phase), while the other contains mineral oil with 2-hexyldecanoic acid (surfactant-low organic phase). We found that the pH of the water phase has negligible effect on the ratio of the sizes of the ‘daughter’ droplets. However, the contact angle between two droplets highly depends on the pH of the alkaline solution.

Design of an optimal middle phase microemulsion for ultra high saline brine using hydrophilic lipophilic deviation (HLD) method

Abstract In this work, alcohol-free surfactant formulations incorporating sodium alkyl alkoxy sulfate surfactants and a sodium alkyl ethoxy sulfate surfactant are tested at 52 °C for reservoir brine having a total dissolved solids of above 300,000 mg/L with total hardness of about 13,000 mg/L. The optimized surfactant formulations show excellent aqueous phase stability, produce an ultra-low-interfacial tension (IFT) of 0.004 mN/m, and give fast coalescence rates of less than 30 min at reservoir salinity and temperature. Surfactant-only sand pack studies further validate the formulations by mobilizing about 60% of residual oil without mobility control. In addition, the hydrophilic lipophilic deviation (HLD) method is used to find the optimal surfactant/co-surfactant ratio (defined as the ratio giving the lowest IFT) at the reservoir salinity and temperature. Results show, first, that HLD constants measure at low salinity are applicable at high salinity and high hardness, and second, that the correct determination of surfactant head constant ‘K’ and temperature constant ‘αT’ governs the precision of the HLD approach as a surfactant selection tool for chemical enhanced oil recovery (cEOR) application. Results illustrate the potential of surfactant-only flooding to produce significant tertiary oil recovery.

알칼리-계면활성제 용액을 이용한 인도네시아 A원유의 마이크로에멀전 특성

For the enhanced oil recovery, one of the most important factors is to determine the surfactant formulation in chemical flood. The objective of this study is to analyze the microemulsion formed between the alkali-surfactant (AS) solution and A crude oil for screening surfactants. The alkali-surfactant solution was manufactured by using the surfactant purchased from AK ChemTech. C16-PO7-SO4 and sodium carbonate solution were used as surfactant and alkaline, respectively. Both TEGBE and IBA were used as a co-solvent. The AS solution and A crude oil can form a Type III middle phase microemulsion at the salinity from 0.0 wt%~3.6 wt%. Increasing the salinity causes the phase transition of microemulsion from the lower (Type I) to middle (Type III) to upper (Type II) phase. Interfacial tension (IFT) values calculated by Huh’s equation were in good agreement with ultralow IFT. According to this characteristic, the surfactant purchased from a domestic company can be applied to the enhanced oil recovery.

The UNIFAC model and the partition of alkyl and alkylphenol ethoxylate surfactants in the excess phases of middle phase microemulsions

The partition of non-ionic surfactants between oil and water is an important parameter that influences the performance of surfactant-based separations, the fate of surfactants in the environment, and the absorption by surfactants in living organisms. From a thermodynamics point of view, the partition of surfactants between oil and water can be used as a method to quantify the hydrophilic–lipophilic nature of surfactants and oil. In this work, a group contribution model, the universal functional activity coefficient (UNIFAC) framework, has been modified to fit and predict the partition of alkylphenol, and alkyl ethoxylated surfactants between aqueous and oil phases. To perform such calculations the interaction parameters of an ethoxylate functional group were optimized, including the temperature dependence for functional groups known to form hydrogen bonds (CH2CH2OH2O, OHH2O). The optimization was performed by fitting this modified UNIFAC model to experimental partition coefficient of octylphenol ethoxylated surfactants in the excess phases (water and n-heptane) of middle phase microemulsions at 25 and 55°C and to experimental critical micelle concentration (CMC) data. The modified UNIFAC is capable of predicting the partition of alkylphenol ethoxylates and alkyl ethoxylates with varying degrees of ethoxylation, tail length and temperature and different oils. The predicted partition values correlate with experimental bioconcentration factors (BCFs) reported for alkyl ethoxylates. The model also predicts properly the critical micelle concentration (CMC) of alkyl and alkylphenol ethoxylate surfactants. The predicted partitions also helped estimate the equivalent alkane carbon numbers (EACNs) of various oils.

Phase behavior and interfacial tension evaluation of a newly designed surfactant on heavy oil displacement efficiency; effects of salinity, wettability, and capillary pressure

This work aims to discuss the results of wide ranges of laboratory investigations to evaluate the performance of a newly-formulated surfactant for heavy oil reservoirs in order to improve the microscopic sweep efficiency after water flooding processes. In the first part, the specific behavior of the formulated surfactant including its salinity tolerance, interfacial tension, and optimum performance window was determined. Then, the application of surfactant solutions in real sandstone reservoir rocks was assessed for both oil-wet and water-wet cases. Besides, the effect of changing the capillary and viscous forces and interfacial tension on the residual phase saturations were characterized. According to the results, the newly formulated surfactant provides middle phase micro-emulsion and low IFT value (i.e., about 0.01mN/m) in a salinity window around 150,000ppm which indicates its proper performance at high salinity ranges. Both the relative volume and solubilization ratios demonstrate the proper values to be applied for real case applications. Monitoring the differential pressure response and the effluent states in both water-wet and oil-wet Berea sandstone cores represent an incremental residual heavy oil production after water flooding through the formation of the emulsified oil droplets in the effluent solutions by chemical slug flooding. Plotting the capillary desaturation curves for both wetting and non-wetting phases through different capillary numbers demonstrate a normal variation trend for the non-wetting phase (approximately a semi-log relationship), while the wetting phase is greatly affected by the capillary end effect and relative permeability variations in the porous medium. This useful information could be extended for the other similar cases of chemically enhanced heavy oil recovery processes.

Composition of the Middle Phase Microemulsion Formed by Sodium Dodecyl Sulfonate/1-Alcohol/n-Alkane/Water

The composition of the microemulsion plays a key role in modulating the formation of nanoparticles of inorganic materials. In order to understand the modulating mechanism, the composition of the middle phase microemulsion formed by Sodium Dodecyl Sulfonate/ 1-Alcohol/ n-Alkane/ Water quaternary system was studied by δ-γ phase diagram. A series of phase inversions O/W (2) → B.C.(3) → W/O( ) were observed with the increase in 1-alcohol concentration. Some physicochemical parameters, such as the coordinates of the start (βΒ, εB) and end points (βE, εE) of the middle-phase microemulsion, the mass fractions of AS (CS) and 1-alcohol (CA) in the total system, and the solubilities of AS (SO) and 1-alcohol (AO) in oil phase, were calculated. The influences of n-alkanes, 1-alcohol and concentration of NaCl solution on the composition of middle phase microemulsion were significantly.

Study of Oil Displacement Performance of Hydroxyl Sulfobetaine Surfactant

In this paper, new alkali-free hydroxyl sulfobetaine surfactant designed for the target oil reservoir in our laboratory was used. The interfacial tension property, emulsifying capability, peeling the oil film between surfactant/polymer binary oil-displacing system and the target crude oil and the viscosity of the system were investigated systematically. Finally, oil-displacement capacity of the binary oil-displacing system on the target reservoirs natural cores was discussed. The experimental results indicated under the actual condition of the target oil reservoir with total salinity ranging from 4694mg/L to 24270mg/L and temperature being 50°C, the surfactant/polymer binary oil-displacing system with surfactant mass fraction ranging from 0.025% to 0.2% and polymer mass fraction of 0.15% could reach ultra-low interfacial tension with the target crude oil rapidly. The surfactant/polymer binary system above mentioned could emulsified crude oil easily and the volume fraction of WinsorIII middle phase microemulsion could be up to 53.06%. It also could peel the oil film adhered to oil-wet quartz plate quickly and increase the viscoelastic of surfactant/polymer binary oil-displacing system slightly. The displacement experiments made by using natural core in the target oil field indicated that oil recovery was improved by 15% after water flooding. All these results showed that hydroxyl sulfobetaine surfactant had a good potential for flooding in EOR.

Middle-Phase Microemulsions Formed by n-Dodecyl Polyglucoside and Lauric-N-methylglucamide

The three-phase behaviors for the quaternary system of n-dodecyl polyglucoside or lauric-N-methylglucamide (MEGA-12)/n-alcohol/alkane/water have been studied with ϵ-β fishlike phase diagram. The increase of ϵ at constant β causes a series of phase inversions Winsor I(2) → III(3) → II . The physicochemical parameters, such as the mass fraction of n-butanol in the hydrophile-lipophile balanced interfacial layer (AS), the coordinates of the start and end points of the middle-phase microemulsion, and the solubilities of surfactant and n-butanol in alkane phase were calculated. The effects of different oils and aqueous media on the phase behavior, the composition of the interfacial layer, and the solubilizing power were investigated. It was found that the oil with small molecular volume increases the solubilizing power. In inorganic salt (NaCl) and acid (HCl) solutions, less n-butanol is needed than that in alkali (NaOH) solution to form middle- and single-phase microemulsions. The middle-phase microemulsions formed by n-dodecyl polyglucoside and lauric-N-methylglucamide were compared.

보조계면활성제가 노닐페놀 에톡실레이트 계면활성제, 탄화수소 오일, 물로 이루어진 삼성분계의 상평형 및 동적거동에 미치는 영향

본 연구에서는 보조계면활성제 첨가가 nonylphenol ethoxylate (NP) 계면활성제, 물, 탄화수소 오일의 3성분으로 이루어진 시스템의 평형 및 동적 거동에 미치는 영향을 살펴보았다. 실험에서 사용한 펜탄올, 옥탄올, 데칸올 등의 보조계면활성제는 모두 소수성 첨가제로 작용하였으며, 소수성 증가 효과는 알코올의 사슬 길이 증가 및 첨가량 증가에 따라 증가하였다. 계면활성제 시스템이 친수적인 조건에서는 비극성 오일의 종류에 상관없이 시간에 따라 오일의 크기가 감소하였으며, 마이셀 용액에 의한 탄화수소 오일의 가용화는 diffusion-controlled 메커니즘이 아닌, interface-controlled 메커니즘을 따름을 확인할 수 있었다. 반면에 소수성 조건에서는 과포화로 인하여 일어나는 자발적 유화 현상과 물과 계면활성제의 오일상으로의 확산으로 인한 오일의 크기 증가가 관찰되었다. 비극성 탄화수소 오일과 계면활성제 수용액 사이의 시간에 따른 계면장력 측정 결과는 동적 거동 실험결과와 일치하는 경향을 나타내었다. 한편 middle-phase 마이크로에멀젼을 포함한 3상이 형성되는 조건에서는 매우 낮은 계면장력으로 인하여 오일이 수용액 상에 빠른 속도로 가용화되었고 작은 방울 형태로 유화되었다. In this study, the effects of cosurfactant on phase equilibrium and dynamic behavior were studied in systems containing nonylphenol ethoxylate (NP) surfactant solutions and nonpolar hydrocarbon oils. All the cosurfactants used during this study such as n-pentanol, n-octanol and n-decanol acted as a hydrophobic additive and the hydrophobic effect was found to increase with both increases in chain length and amount of addition of a cosurfactant. Dynamic behavior studies under hydrophilic conditions showed that the solubilization of hydrocarbon oil by NP micellar solution is controlled by an interface-controlled mechanism rather than a diffusion-controlled mechanism. Both spontaneous emulsification of water into oil phase and expansion of oil drop were observed under lipophilic conditions because of diffusion of surfactant and water into oil phase. Under conditions of a three phase region including a middle-phase microemulsion, both rapid solubilization and emulsification of oil into aqueous solutions were found mainly due to the existence of ultralow interfacial tension.

Effect of Nonaqueous Phase Liquids on the Phase Behavior of Microemulsion Formed by n-Dedocyl Polyglucoside

Surfactant-enhanced aquifer remediation has gained more and more attention. In this article, the n-dodecyl polyglucoside based middle phase microemulsions have been studied with the Winsor phase diagram method. The phase types, phase volumes, alcohol window, optimum alcohol concentration, and region of the middle-phase microemulsion were observed. The results show that the increase in n-butanol concentration causes a series of phase inversion Winsor I (2) → III(3) → II(). The larger the concentration of C12G1.46, the larger the solubilization power of the microemulsion system. The solubilization power of the microemulsion system for chlorocarbon is larger than that for alkanes.

Temperature-Dependent Phase Behavior, Particle Size, and Conductivity of Middle-Phase Microemulsions Stabilized by Ethoxylated Nonionic Surfactants

The present paper deals with the influence of salinity and temperature on the phase behavior and conductivity of middle-phase microemulsions stabilized by ethoxylated nonionic surfactants. Optimal salinity of microemulsion increases with increases in temperature. Middle phase microemulsion shows stability for temperatures up to 330 K, and then the relative phase volume of middle phase decreases slightly. Particle size distribution of the microemulsion formulations with different ethoxylated nonionic surfactants have been studied by dynamic light scattering. Percolation behavior of the middle-phase microemulsion systems have been studied as a function of mass fraction of water for different nonionic surfactants at 0.02 mass fractions of NaCl concentration by electrical conductivity measurement. The temperature effect on the electrical conductivity of middle-phase microemulsions is also studied. With an increase in temperature, the conductivity increases and the activation energy of the system also increase...

Phase behavioral changes in SDS association structures induced by cationic hydrotropes

Phase behavior of systems containing sodium dodecyl sulfate (SDS) as anionic surfactant and each of tetraethyl ammonium chloride (TEACl) and tetrabutyl ammonium bromide (TBAB) as cationic hydrotropes in the presence of water and heptane oil was studied. This combination was also used to formulate alcohol-free middle phase microemulsion at different salt concentrations. Anisotropy was detected by cross polarizer and polarized microscopy. Ultralow interfacial tension for microemulsion was calculated theoretically using Chun Huh equation. Micelles and inverse micelles were characterized by conductivity measurements. Liquid crystals did not appear in these short-chain hydrotropic systems. Microemulsion salinity scans for 1% SDS/TBAB (2:1M ratio) at 25°C, exhibited Winsor III type at an optimal salinity of 8.5% NaCl, whereas the optimal salinity was found to be 4% NaCl for 8% SDS/TBAB (1:1M ratio).

Phase behavior of the water+nonionic surfactant (C12E8)+1-dodecene ternary system across a wide temperature range

This manuscript is the first report that discusses the phase behavior of a ternary system composed of water, nonionic surfactant C12E8, and 1-dodecene. The phase behavior (Kahlweit fish and tie lines at different temperatures) of this ternary system was investigated based on the phase behavior of the water+C12E8, water+1-dodecene and C12E8+1-dodecene binary subsystems. Novel experimental liquid–liquid equilibrium data are presented for the three corresponding subsystems. The data obtained for the water+C12E8 system was compared with data from the literature. The phase prism of the ternary system was measured over a wide temperature range using several analytical methods (Karl Fischer titration and HPLC). The general phase behavior is very similar to the well-known phase behavior of water +nonionic surfactant+alkane systems. Classical Winsor-type phase behavior was established within the ternary system depending on the temperature. At 354.15K, a middle-phase microemulsion, which contained 1-dodecene and water mass fractions of approximately 0.2 and 0.6, was found. This phase behavior can be exploited for chemical reactions, such as the hydroformylation of 1-dodecene to yield 1-tridecanal through the use of the water-soluble and very expensive Rh catalyst at temperatures at which the middle-phase microemulsion exists.

Water-Diesel Microemulsions Stabilized by an Anionic Extended Surfactant and a Cationic Hydrotrope

Alcohol-free microemulsions were formulated using mixtures of extended surfactant (C12-14-PO14-EO2SO4Na), sodium dodecyl benzene sulfonic acid and cationic hydrotropes with equal amounts of water and diesel. The cationic hydrotropes had short hydrocarbon or propylene oxide chain. The formulation included sodium carbonate to convert naphthenic acids in diesel to soaps. The phase behavior at ambient temperature of oil-free mixtures as a function of NaCl concentration was investigated. Visual inspection as well as cross polarizers were used to detect anisotropy. The microemulsion fish phase diagram and solubilization ratios for diesel and brine in the middle phases were determined. The minimum surfactant concentration needed to initiate middle phase formation was 0.10 wt%. Salinity scans revealed that optimal salinity can be adjusted according to the hydrophilic/lipophilic nature of the hydrotrope used. Interfacial tension measurements using a spinning drop tensiometer showed a minimum value of 0.0015 mN/m between middle phase microemulsion and excess brine and a value of 0.032 mN/m between diesel and brine.

Phase Behavior of Microemulsions Formulated with Sodium Alkyl Polypropylene Oxide Sulfate and a Cationic Hydrotrope

The partial ternary phase diagram of anionic extended surfactant of alkyl polypropylene oxide sulfate C12(PO)4SO4 alone and combined with the cationic hydrotrope, tetrabutyl ammonium bromide with water and decane were determined under ambient conditions. Middle phase microemulsion was formulated using salinity scans in the dilute region of surfactant/brine/decane. Visual inspection as well as cross polarizer and optical microscopy were used to detect anisotropy. Spinning drop tensiometer was used to measure interfacial tension (IFT). The first ternary phase diagram using the extended surfactant alone showed three one phase regions, the anisotropic lamellar liquid crystalline phase, L α and the isotropic L1 micellar liquid and L3 sponge phase. In the second ternary phase diagram using the extended surfactant combined with tetra butyl ammonium bromide, an isotropic micellar region, L 1, appeared in the diluted area of the phase diagram. Meanwhile the L α phase disappeared completely and the three phase region has a bluish transparent middle phase. Interfacial tension measurements between middle phase and brine, and between decane and brine yielded ultra low values. Calculated IFT values using the characteristic length obtained using De Gennes approximation gave almost half the measured values. The interfacial rigidity was also calculated and compared to values obtained from the literature.