Dissipative Particle Dynamics Study of Interfacial Properties and the Effects of Nonionic Surfactants on Hydrocarbon/Water Microemulsions

The aim of this work was to apply dissipative particle dynamics (DPD) mesoscopic simulations to study the interfacial orientation and the effect of the nonionic surfactant, hexaethylene glycol monododecyl ether (C₁₂E₆), on different (oil (dodecane)/water) microemulsion systems. The Hildebrand-solubility-parameter model and Flory–Huggins/Hansen-solubility-parameter (FH/HSP) model were combined to evaluate the DPD interaction parameter (a_ij) where the solubility parameters (δ_i) as DPD input parameters were preliminary validated by all-atom molecular dynamics (MD) results and experimental data. The interfacial property dependence of dodecane/water/C₁₂E₆ system on the oil/water (o/w) ratio and on the concentration of surfactant and orientation at the interface were investigated. It was found that the surfactant addition reduced the IFT of o/w interfaces and this reduction was more efficient for water-in-oil microemulsions (o/w ≤ 1).     

Studies of Interfacial Activities of Four Kinds of Surfactants at Oil/Water Interface

This article aims to compare the interfacial activities of different kinds of surfactants in the same oil/water system. The anionic surfactants of alkylbenzene sulfonates, the polyoxyethylenated nonionic surfactants, the cationic surfactants of alkyl trimethyl ammonium chlorides, and the zwitterionic surfactants of alkyl hydroxyl sulfobetaines were used, and the interfacial tensions of the surfactant solutions against kerosene at different NaCl concentrations were measured. It is found that the interfacial activities of the alkylbenzene sulfonates are high and ultralow interfacial tensions (<0.01 mN/m) can be obtained at proper salinities. While, the nonionic surfactants have relatively low interfacial activities and the minimum tensions are around 0.01 mN/ms. The salinity scanning curves of the alkylbenzene sulfonates and nonionic surfactants decrease first, then increase, showing their interfacial activities can be changed by the salinity effectively. The cationic and zwitterionic surfactants have very low interfacial activities, of which all the tensions are higher than 0.1 mN/ms and are hard to be changed by the salinity. The experimental results may have important reference values for enhanced oil recovery.     

由表面活性物质溶液的动界面张力外推求平衡界面张力的研究

表面活性物质溶液的界面张力往往随时间而变,难以测得平衡界面张力J。Kloubek^[1]曾应用经验式:1/(δ_H2O-δ_t)=b/(At^1/2)+1/A,以[1/(δ_H2O-δ_t)]对1/t^1/2作图外推求得溶液的平衡表面张力,但所得结果仅与文献值大致相符。本文从理论上分析该经验式的由来,以及产生偏离的原因,并寻求了解决的办法。     

Gemini阴离子表面活性剂水溶液的界面活性

Gemini阴离子表面活性剂水溶液的界面活性;Gemini阴离子表面活性剂;表面张力;CMC;C20;界面张力     

油/水界面表面活性剂的复配协同机制

采用耗散颗粒动力学(DPD)方法模拟了椰油酸二乙醇酰胺(6501)分别与十二烷基-α-烯烃磺酸钠(DAOS)、椰油酰胺丙基二甲基甜菜碱(CAB)和十二烷基苯磺酸钠(SDBS)复配体系中表面活性剂在油/水界面的排布行为, 探讨了盐度及分子结构对单一和复配表面活性剂界面活性的影响, 从界面效率、界面密度和分子排布等角度讨论了油水界面表面活性剂混合体系的复配协同增效机制.     

Synthesis and Interfacial Properties of Imidazoline Surfactants

Quaternary ammonium salts of 2‐undecyl (heptadecyl)‐1‐dithioureido‐ethyl‐imidazoline (SUDEI/SHDEI) have been synthesized, and their interfacial properties are investigated. The effects of temperature, alkyl chain R length, and polarity of solvents on the surface tension are discussed. The results show that surface tension of SUDEI and SHDEI in water solutions decreases with increasing of temperature, and SHDEI shows lower cmc value than SUDEI at constant temperature, indicating that it is easier for SHDEI to form micelles in water. SUDEI and SHDEI show much higher cmc in ethanol‐water (1∶4, v/v) than that in pure water. The molecular structure of SUDEI/SHDEI is composed of lipophilic group R and hydrophilic group comprising active elements S, N and imidazoline ring and the two groups are of similar length, which is similar to that of bi‐block copolymer. Thus, interesting results have been found in the preparation of nanomaterials in the presence of imidazoline surfactants. The corresponding mechanisms are still under investigation.     

Investigation Static/Dynamic Surface and Interfacial Tension of Some Synthesized Polymeric Surfactants to Enhance the Egyptian Jet Fuel A1 Atomization

In the present work some exthoxylated polyalkylphenol surfactants have different alkyl chains (nonyl and dodecyl) were synthesized. The static surface tension for these surfactants in water and jet fuel A1 was measured and the critical micelle concentration (CMC) for each surfactant was determined. The data show the general trend of decreasing the CMC against the molecular weight of the synthesized polymeric surfactants. The HLB of these surfactants was also calculated. The dynamic surface tension for the synthesized surfactants was measured at CMC. The dynamic interfacial tension for these surfactants with jet fuel A1 at CMC was also measured using the spinning drop technique. The results showed that the effect of the synthesized surfactants on deceasing the time of droplet maturation was significant remarked. The decrease of this time leads to enhance of jet fuel atomization.     

新型含硅表面活性剂的合成及性能研究

含有双胺基的三硅氧烷中的伯胺基与D-葡萄糖酸-δ-内酯进行酰胺化,仲胺基与低聚乙二醇甲醚缩水甘油醚、二缩水甘油醚进行烷基化,制备了新型含硅表面活性剂Me₃SiOSiMeR¹OSiMe₃ [R¹=(CH₂)₃NR²(CH₂)₂NHCO(CHOH)₄CH₂OH; R²=H, CH₂CH(OH)CH₂O(CH₂CH₂O)_xCH₃, x=1, 2, 3] (1a, 2a～2c)和(CH₂OCH₂)_y(Me₃SiOSiMeR³OSiMe₃)₂ [R³=(CH₂)₃NR⁴～(CH₂)₂NHCO(CHOH)₄CH₂OH; R⁴=CH₂CH(OH)CH₂OCH₂, y=0, 1, 2] (3a～3c).这些化合物的结构用¹H, ¹³C核磁共振仪和元素分析仪进行鉴定.研究了这些新型含硅表面活性剂的界面性能,在浓度分别为10^-4和10^-5 mol·L^-1时可以将水的表面张力降低至约21 mN·m^-1.     

Dynamic Interfacial Tension Behavior of Water/Oil Systems Containing In situ-Formed Surfactants

Time-dependent interfacial tension (IFT) has been investigated for an interfacially reactive immiscible system composed of model-acidified oil and alkaline water. The acidified oil was composed of either lauric acid or linoleic acid dissolved in n-dodecane. Drop volume tensiometry was employed to measure the interfacial tension between the two phases. In the case of lauric acid, the IFT value was found to decrease sharply with increasing alkali concentration, even at low drop formation times. In the case of linoleic acid, the IFT decrease with the drop formation time was more gradual, especially at low alkali concentration. The rate of formation of the interfacial area was also found to be dependent on alkali concentration.     

Interfacial Structure of Water as a New Descriptor of the Hydrogen Evolution Reaction

Driven by the persisting poor understanding of the sluggish kinetics of the hydrogen evolution reaction (HER) on Pt in alkaline media, a direct correlation of the interfacial water structure and activity is still yet to be established. Herein, using Pt and Pt–Ni nanoparticles we first demonstrate a strong dependence of the proton donor structure on the HER activity and pH. The structure of the first layer changes from the proton acceptors to the donors with increasing pH. In the base, the reactivity of the interfacial water varied its structure, and the activation energies of water dissociation increased in the sequence: the dangling O−H bonds < the trihedrally coordinated water < the tetrahedrally coordinated water. Moreover, optimizing the adsorption of H and OH intermediates can re-orientate the interfacial water molecules with their H atoms pointing towards the electrode surface, thereby enhancing the kinetics of HER. Our results clarified the dynamic role of the water structure at the electrode–electrolyte interface during HER and the design of highly efficient HER catalysts.     

石油磺酸盐结构与界面活性关系研究

对25个不同来源及批次的石油磺酸盐样品进行界面张力测试、质谱分析,研究了其结构与界面活性之间的相互关系.实验结果表明:高碳链C17~C25磺酸盐含量的高低对界面活性具有最主要的影响,含量较高则界面活性较优.另外当样品所含组分的分子量在200~800范围内均匀分布时,相对丰度最大的分子离子峰聚集在479(C23苯磺酸盐)附近的样品界面活性则较优.     

Molecular Dynamics Simulation of Sulfobetaine-Type Zwitterionic Surfactants at the Decane/Water Interface: Structure,Interfacial Properties

Molecular dynamics simulations of interfacial properties of new sulfobetaine-type zwitterionic surfactants were performed using a united atomistic model, and a detailed analysis of hydrophilicity, temperature sensitivity, and salt resistance of surfactants was carried out. The new model was parameterized to reproduce the density and showed good agreement with experimental values. The results showed that the surfactant will not cease to be effective with the increase of the temperature from 300 to 373 K but as it rises, the interfacial tension will have a reduction. This kind of surfactant can be proved to remain an activity at high concentration of monovalent and divalent cations. It has commendable salt tolerance.     

CMC系列高分子表面活性剂与原油 超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达28～35mN/m,界面张力达到10     

Adsorption Properties of Hydrocarbon and Fluorocarbon Surfactants Ternary Mixture at the Water-Air Interface

Measurements were made of the surface tension of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10 oxyethylene groups in the molecule (Triton X-100, TX100) and cetyltrimethylammonium bromide (CTAB) with Zonyl FSN-100 (FC6EO14, FC1) as well as with Zonyl FSO-100 (FC5EO10, FC2) ternary mixtures. The obtained results were compared to those provided by the Fainerman and Miller equation and to the values of the solution surface tension calculated, based on the contribution of a particular surfactant in the mixture to the reduction of water surface tension. The changes of the aqueous solution ternary surfactants mixture surface tension at the constant concentration of TX100 and CTAB mixture at which the water surface tension was reduced to 60 and 50 mN/m as a function of fluorocarbon surfactant concentration, were considered with regard to the composition of the mixed monolayer at the water-air interface. Next, this composition was applied for the calculation of the concentration of the particular surfactants in the monolayer using the Frumkin equation. On the other hand, the Gibbs surface excess concentration was determined only for the fluorocarbon surfactants. The tendency of the particular surfactants to adsorb at the water-air interface was discussed, based on the Gibbs standard free energy of adsorption which was determined using different methods. This energy was also deduced, based on the surfactant tail surface tension and tail-water interface tension.     

CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.     

Effects of a Novel Organic Alkali on the Interfacial Tension and Emulsification Behaviors Between Crude Oil and Water

Experiments have been carried out to investigate the interfacial tension (IFT) and emulsification behaviors between Shengli crude oil and a novel organic alkali (OA). The dynamic IFT and minimum IFT are adopted to characterize the IFT behaviors; the microscopic method, Turbiscan stability index, separated water rate, and laser particle size analysis method are used to show the emulsification behaviors. The dynamic and minimum IFT both decrease continuously with the increase of OA concentration whether surfactant is added or not; because of the synergy of OA and surfactant, the minimum IFT will be reduced to the ultralow value. The synergy is also crucial for the crude oil emulsification. When OA and surfactant are used together, owing to the mosaic and cross-multiple adsorption of OA, surfactant and in situ soap at the interfacial film, the oil can be emulsified more easily, the quantity of emulsified droplets is higher, and the emulsion is more stable with OA concentration increases. The relationship of the minimum IFT and emulsification is investigated; it indicates that the emulsion stability improves, the degree of dispersed homogeneity of oil droplets increases, and the median diameter of emulsified oil droplets decreases with the decline of the minimum IFT.     

Studies of Synergism in Binary Alkylbenzene Sulfonate Mixtures for Producing Low Interfacial Tensions at Oil/Water Interface

In order to study the synergism between alkybenzene sulfonate and alkybenzene sulfonate, five di-n-alkylbenzene sulfonates were used and the interfacial tensions of single sulfonates and their binary mixtures against a series of alkane homologues were measured. The effects of hydrophilic-lipophilic abilities of sulfonates and mixing ratio on synergism were discussed. It is revealed that the synergistic mechanism derives from the amelioration of the hydrophilic-lipophilic ability of the surfactant system, and the method to achieve synergism is adding the hydrophilic alkybenzene sulfonate to the lipophilic alkylbenzene sulfonate, and ultralow interfacial tensions can be obtained in proper mixing ratios. The results are useful for enhanced oil recovery.      

十二烷基硫酸钠与甜菜碱在气液和油水界面的复配协同作用研究

研究了十二烷基硫酸钠（SDS）和甜菜碱（Betaine）以及复配体系在油水界面和气液界面的排布行为,探讨了温度、无机盐和复配比例对表面活性剂界面活性和泡沫稳定性的影响,重点探讨了多价无机阳离子对表面活性剂界面吸附行为和复配协同加合增效作用的影响,得到了海水为介质条件下两方面性能均较好的体系,取得的认识为高盐条件下低张力泡沫驱油体系的设计与应用提供理论依据和指导.     

Synthesis and Applications of Alkylbenzene Sulfonate Gemini Surfactants

A series of anionic Gemini surfactants with the same structure except for the spacer and side chain length of the alkylbenzene sulfonate were synthesized based on dodecyl benzene and toluene. The structures of the compounds were confirmed by infrared and nuclear magnetic resonance spectroscopy, and elemental analyses. The effect of spacer and side chain length on the interfacial tension of Gemini surfactant solution was investigated by comparison of the critical micelle concentration (cmc) of the surfactants in aqueous solution using the drop volume method, and the surface tension at the cmc (γcmc). The Gemini surfactant with the best properties was used as emulsifier in emulsion polymerization of methyl methacrylate, and its foam stability was also determined.     

Silicon-Modified Carbohydrate Surfactants V: The Wetting Behaviour of Low-Molecular-Weight Siloxane,Carbosilane, Silane and Polysilane Precursors on Low-Energy Surfaces

The surface tensions, wetting tensions, contact angles and solid/liquid interfacial tensions of defined siloxanes as well as those of analogous carbosilanes, polysilanes and neopentyl substituted silanes were determined. The wetting experiments were carried out on a glass plate coated with perfluoroalkyl methacrylate (FC 722^®). The siloxanes possess the lowest surface tensions. Due to the presence of oxygen atoms in the siloxane backbone, a donor–acceptor portion (γ^+/−_lv) of the surface tension of about 1–2 mN/m was determined. The solid/liquid interfacial tension also contains a donor–acceptor portion (γ^+/−_sl). Its value is almost identical to that of γ^+/−_lv. The γ^+/−_sl differences between individual molecules of the same surface tension are responsible for contact angle differences of up to 4°. © 1997 John Wiley & Sons, Ltd.