Studies on some zwitterionic surfactant gas hydrate anti-agglomerants

Low dosage hydrate inhibitors (LDHIs) are a recently developed hydrate control technology, which can be more cost-effective than traditional practices such as the use of thermodynamic inhibitors e.g. methanol and glycols. Two classes of LDHI called kinetic inhibitors (KHIs) and anti-agglomerants (AAs) are already being successfully used in the field. This paper describes efforts to develop new classes of AAs based on zwitterionic surfactants. The chemistry of the new surfactants is described along with experiments to determine their performance carried out in high pressure cells and a wheel loop. The results indicate positive performance for some products but not as good as a commercial quaternary ammonium-based surfactant AA. It was also shown that best results were obtained if the two ionic groups are spaced far apart from each other in the molecule. The best AA molecule tested was 3-[N,N- dibutyl-N-(2-(3-carboxy-pentadecenoyloxy)propyl)]ammonio propanoate. It performed well in sapphire cell tests at up to 15.9 °C subcooling. Its performance was fairly good in the wheel loop at 13.4 °C subcooling, but failed at 16.5 °C subcooling. 3-[N,N-dibutyl-N-(2- hydroxypropyl)ammonio]propanoate was also shown to be an excellent synergist for polyvinylcaprolactam KHIs.     

Crystal growth inhibition of tetrahydrofuran hydrate with bis- and polyquaternary ammonium salts

Small quaternary ammonium salts, particularly with butyl or pentyl groups, have been shown previously to be good Structure II tetrahydrofuran hydrate crystal growth inhibitors. This ability has been exploited in their use as synergists for certain kinetic hydrate inhibitor polymers, and in the design of commercial gas hydrate anti-agglomerants. We have now investigated the effect of bis- and polyquaternary ammonium salts, in which all the nitrogen atoms are in the backbone of the molecule, on the crystal growth of tetrahydrofuran hydrates. The results are compared with those of monomeric quaternary compounds previously reported. The new compounds tested contain 2 to over 100 quaternary centres with various structural geometries including linear and branched polymers. The size of the alkyl groups on the nitrogen atoms was varied and contained from 2 to 6 carbon atoms. Improved performance over monoquaternary ammonium salts was obtained with both bis-quaternary and polyquaternary ammonium products. The optimal distance between the nitrogen atoms in bis-quaternary ammonium salts for best THF hydrate inhibition appears to be with a chain of 6–8 aliphatic carbon atoms.     

咪唑啉基季铵盐型双子表面活性剂的合成与性能

以环氧氯丙烷为连接剂,油酸、二乙烯三胺分别为疏水和亲水基团的初始原料合成了一种咪唑啉基季铵盐型双子表面活性剂,通过IR1、HNMR确证了目标产物结构。研究了其在水溶液中对苯的乳化力、稳泡能力、亲水亲油平衡值、表面张力的影响。动态激光散射法测试了双子咪唑啉基季铵盐乳化制备O/W型乳状液的乳胶粒径尺寸,利用双子表面活性剂作为乳化剂,油酸为分散相。静态失重法评价了双子表面活性剂作为缓蚀剂对Q235钢在质量分数8%溶液中的缓蚀性能。结果表明,所合成的双子咪唑啉基季铵盐具有较好的表面活性,临界胶束浓度CMC约为2×10-4mol/L,γCMC为31.40 mN/m,HLB值为14.2,对苯的乳化能力及稳泡性能良好。该乳液稳定,在25~50℃时,O/W乳液的胶粒尺寸在216~236 nm,是一种性能良好的O/W型乳化剂。失重法测定结果表明,该双子咪唑啉基季铵盐型表面活性剂缓蚀性能优于相应单链咪唑啉季铵盐表面活性剂。     

Clay Swelling Inhibition Using Novel Cationic Gemini Surfactants with Different Spacers

Hydration of shale formation by water-based drilling fluids leads to several problems, such as the collapse of boreholes, tight holes, and stuck pipe, which may impede further drilling and time loss in rectifying the problems, leading to heavy economic losses. This study reports the development of new gemini cationic surfactants as shale-swelling inhibitors. These gemini surfactants are structurally similar but differ in terms of the spacer group. Saturated butyl group ( GS1 ) and unsaturated 2-butenyl ( GS2 ) and 2-butynyl ( GS3 ) were introduced as spacer groups of gemini surfactants. To assess the performance of new gemini cationic surfactants, two reliable clay sources were considered. The first clay is from an unconventional formation and the second clay is sodium bentonite. The inhibition characteristics of gemini surfactants were evaluated using dynamic swelling, hot rolling, rheology, and filtration experiments. Different formulations based on commercially available solutions for shale-swelling inhibitors were applied and compared with cationic shale inhibitors. It was observed that the new gemini cationic surfactants with different spacers (saturated and unsaturated) reduced the shale swelling by different percentages. The GS2 surfactant, containing an unsaturated double bond proved to be a good swelling inhibitor as compared to GS1 and GS3 . It also showed acceptable performance compared with the common shale inhibitor (KCl) used in the industry. The addition of surfactant has less impact on the rheological properties as compared to KCl. The filtration properties of the base mud were unchanged when surfactants were used. However, the commercial inhibitor, KCl, significantly increased the filtration volume that is associated with the disintegration of the clay. In summary, unlike commercial inhibitors, the synthesized surfactants reduced the clay swelling without affecting the other properties of the drilling fluids.     

Extended Surfactants Including an Alkoxylated Central Part Intermediate Producing a Gradual Polarity Transition—A Review of the Properties Used in Applications Such as Enhanced Oil Recovery and Polar Oil Solubilization in Microemulsions

The research published in the past half century indicates that surfactant interfacial performance in producing low tension or high solubilization with polar oils is not generally attained with pure conventional species exhibiting well-defined polar and nonpolar parts. The improvement trends reached with surfactant mixtures as well as the introduction of additives like cosurfactants and linkers lead to the introduction of the so-called extended surfactants, whose structure includes an intermediate polarity spacer between the hydrophilic head and the lipophilic tail. Recent investigations on different kinds of surfactants in a variety of applications—such as detergency, cosmetics, enhanced oil recovery or crude demulsifying, and vegetable oil extraction—indicate that these extended surfactants are likely to be particularly performing with oils containing polar groups, such as triacylglycerols and asphaltenic crudes. Possible applications of extended surfactants in enhanced oil recovery, crude emulsion breaking, detergency and cleaning, medicine and cosmetics vehicles, and natural oil extraction as well as some other cases are quickly reviewed.     

THF hydrate crystal growth inhibition with small anionic organic compounds and their synergistic properties with the kinetic hydrate inhibitor poly(N-vinylcaprolactam)

Small, cationic tetraalkylammonium ions (particularly for alkyl=butyl or pentyl) are known to inhibit tetrahydrofuran (THF) and natural gas hydrate crystal growth and have been used as synergists for commercial kinetic hydrate inhibitor polymers (KHIs), such as N-vinylcaprolactam polymers, for a number of years. The ability for small, organic anionic molecules to inhibit (THF) hydrate crystal growth and their potential as KHI synergists in blends with poly(N-vinylcaprolactam) have been investigated. Several series of sodium alkyl carboxylates, sulphates and sulphonates were synthesised. It was found that none of these molecules were capable of inhibiting THF hydrate crystal growth as well as the best tetraalkylammonium salts. Alkyl carboxylates appeared to be more effective as inhibitors than the sulphonates or sulphates. The most effective anionic THF hydrate crystal growth inhibitors had butyl or pentyl groups, with alkyl branching at the tail (i.e. iso- rather than n-isomers) being advantageous. Anionic carboxylate molecules, particularly with isopentyl or isobutyl groups, showed some kinetic inhibition synergy with poly(N-vinylcaprolactam) lowering the onset and catastrophic hydrate formation temperatures in high pressure (78 bar) constant cooling experiments with Structure II hydrates by 1–2 °C when dosed at 2500 ppm compared with using 2500 ppm polymer alone. This synergism was however less than the best tetraalkylammonium salts (alkyl=n-butyl or n-pentyl) at the same test conditions. Sodium butyl sulphonate and sodium 4-methylpentanoate did not prevent hydrate agglomeration with 3.6% brine and decane at 25% water cut in stirred sapphire cells when dosed at 20,000 ppm based on the aqueous phase, whereas 10,000–20,000 ppm active material of several commercially available anti-agglomerants gave fine transportable slurries and no hydrate deposits at the same conditions.     

羟基和酯基型Gemini双季铵盐表面活性剂在煤沥青表面的润湿特性

以自制的羟基和酯基型Gemini双季铵盐表面活性剂为研究对象,在考察其表面活性的基础上,进一步研究了表面活性剂在煤沥青表面的润湿性。研究表明,羟基型Gemini表面活性剂在煤沥青表面的接触角随疏水链长度的增长呈先减小后增大趋势,其中C₁₂-OH在煤沥青表面的润湿效果最好;对于m-n-m酯基型Gemini表面活性剂而言,接触角随疏水链长度的增长而降低。当疏水链长度一定时,m-6-m在煤沥青表面的润湿效果比m-2-m好。在一定浓度范围内,C₁₀-OH、C₁₂-OH和12-2-123种Gemini表面活性剂的表面张力与其在煤沥青表面黏附张力呈线性关系。煤沥青表面的Zeta电位随Gemini表面活性剂浓度的增大呈先增大后趋于平稳的趋势。     

Photopolymerization kinetics of poly(acrylate)-clay composites using polymerizable surfactants

Photopolymerization kinetics of polymer-clay nanocomposite systems utilizing polymerizable quaternary ammonium surfactants as dispersants were systematically investigated to determine the effects of surfactant type and clay morphology on polymerization behavior. For these studies, either polymerizable surfactants were mixed into a clay-monomer system or the surfactants were ionically anchored to clay surfaces and added to the monomer for in situ photopolymerization. Higher photopolymerization rates are observed with increasing polymerizable surfactant concentration, while no significant change or decreases in polymerization rate occur with incorporation of non-polymerizable surfactants. The higher rates observed for polymerizable surfactant systems are due to lower apparent termination rate parameters stemming from immobilization of the surfactants. For clay that is modified with ionically bonded quaternary ammonium surfactants, polymerization rates decrease in both polymerizable and non-polymerizable organoclay systems with increasing concentration, but this decrease is much smaller when polymerizable organoclays are utilized. For the same organoclay concentration, higher polymerization rates and double bond conversions result with increasing polymerizable surfactant concentration via cation exchange. Significant increases in polymerization rate also occur with increasing degree of clay exfoliation.     

三聚表面活性剂的研究进展

综述了三聚表面活性剂的分类、合成方法、结构对性能的影响以及应用。根据亲水头基的电性不同,三聚表面活性剂可分为阳离子型、阴离子型、非离子型和两性离子型4类。根据其结构特点,设计了不同亲水头基、不同中间连接基团和不同尾链的三聚表面活性剂的合成路线。最后介绍了三聚表面活性剂的性能及其在纳米材料的制备、乳液聚合等领域的应用,并对其未来的发展趋势进行了展望。     

煤层气水合化的基础研究

自行设计制造了一套可用于煤层气水合物生成与分解的可视化实验系统,利用该实验系统研究了阴离子表面活性剂、非离子表面活性剂和多孔介质煤对煤层气水合物生成的影响,进行了煤层气水合物生成相平衡参数和分解热力学方面的研究。结果表明:表面活性剂的加入促进了水合物的生长,但水合物的生成情况与表面活性剂的种类和浓度有关;表面活性剂的加入有效地改变了水合物生成的热力学条件;水合物分解过程所需热量较多,证实了利用煤层气水合化技术预防煤矿煤与瓦斯突出以及进行煤层气固化储运的可行性。     

不同季铵盐作用下的CO2水合物相平衡

CO₂气体水合物形成热力学性质是实施海水淡化、沼气纯化、碳捕集和封存、能源利用、天然气储存等技术的关键。采用恒容温度搜索法,在温度272.75~294.35 K,压力0.35~4.50 MPa的范围内,探究了四种季铵盐促进剂对CO₂气体水合物相平衡的影响。结果表明,相同条件下,季铵盐作用下CO₂水合物的相平衡温度由高到低分别为：四丁基氟化铵（TBAF）>四丁基溴化铵（TBAB）>四丁基氯化铵（TBAC）>苄基三乙基氯化铵（TEBAC）。基于Clausius-Clapeyron方程,计算了不同体系的相变潜热,探讨了其对水合物稳定性的影响。可以看出,水合物的相平衡压力对数与温度倒数呈线性关系,其中,TBAF、TBAB作用下的CO₂水合物相变潜热相接近且明显高于其他季铵盐,说明其促进效果最好,所对应的水合物生成条件也最为温和。利用Chen-Guo模型,结合PR状态方程和改进Joshi经验活度模型,分别计算了TBAF、TBAB、TBAC和TEBAC作用下CO₂水合物热力学相平衡数据,计算结果与实验数据吻合良好,最大平均相对误差为7.50%。     

Extraction of Rare Earth Metals Using Liquid Surfactant Membranes Prepared by a Synthesized Surfactant

Abstract

Three surfactants, l-glutamic acid dioleyl ester ribitol (nonionic, 2C ₁₈Δ⁹ GE), l-glutamic acid dioleyl ester quaternary ammonium chloride (cationic, 2C ₁₈Δ⁹ GEC ₂ QA), and dioleyl dimethyl quaternary ammonium chloride (cationic, 2C ₁₈Δ⁹ QA) were synthesized for potential use in liquid membrane operations. These surfactants have strongly hydrophobic, twin oleyl chains as the hydrophobic moiety. Using the synthesized surfactants, extraction of rare earth metals was carried out by liquid surfactant membranes in a stirred tank. The extraction behavior of 12 kinds of rare earth metals was systematically studied with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (commercial name: PC-88A) as a carrier. Different surfactants having an identical hydrophobic moiety can have significantly different behaviors in rare earth extractions by liquid surfactant membranes, where extraction efficiency appears to be governed by the nature of the interfacial microenvironment between oil and water. An interfacial reaction model which takes into account the adsorption of a surfactant at the interface has been proposed to evaluate the permeation rate of rare earth metals by liquid surfactant membranes. It was found that a cationic surfactant strongly enhances the extraction rate of rare earth metals compared with the conventional surfactant, Span 80. The cationic surfactant 2C ₁₈Δ⁹ GEC ₂ QA appears to be one of the best surfactants currently available for rare earth extraction by liquid surfactant membranes.     

油水界面上阴/阳离子型复配表面活性剂体系的分子动力学模拟

采油过程中阴/阳离子型表面活性剂复配使用可显著增强驱油效果,对其微观机理的深入研究有助于驱油用表面活性剂的结构优化设计及使用。采用分子动力学方法研究了不同摩尔比的阴离子表面活性剂聚醚羧酸钠(PECNa)和阳离子表面活性剂十八烷基三甲基氯化铵(OTAC)复配体系在油水界面上的分子行为和物理性质。结果表明,复配体系比单种表面活性剂体系更有利于降低油水界面张力。不同复配比体系中,两种表面活性剂头基相反电荷间的吸引作用使表面活性剂之间对各自反离子的静电吸引作用减弱,且等摩尔比体系尤为明显。阴离子表面活性剂的亲水头基对阳离子表面活性剂亲水头基形成的水化层内水分子的结构取向无显著影响,反之亦然。通过调节两种离子型表面活性剂的复配比例,可调整油水界面吸附层微观结构,有望降低油水界面张力,提高采收率。     

Effect of monovalent anions on cationic Gemini micro-emulsion

Micro-emulsion usually consists of water, oil, surfactants and co-surfactants, and each component has an effect on the phase behavior and solubilization of the micro-emulsion. When the surfactant in the micro-emulsion system is quaternary ammonium cationic Gemini surfactant, the surfactant mainly combines with the anions in the salt. With the increase of salt concentration, the phase transformation of Winsor I → Winsor Ⅲ → Winsor Ⅱ occurred, but the optimum salinity and salt width are different because of the type of salt. The effects of 5 different kinds of monovalent anions, including C₆H₅SO₃^-, I^-, Br^-, NO₃^- and Cl^-, on the phase behavior and solubilization of quaternary ammonium cationic Gemini micro-emulsion are researched by Winsor phase diagram. It is found that the effects of organic anions C₆H₅SO₃^- and I^- on the phase behavior and solubilization of quaternary ammonium cationic Gemini micro-emulsion are most significant, and the effects of Br^-, NO₃^- and Cl^- are less significant. Meanwhile, when the optimum solubilization is achieved, the amount of sodium benzoate is the least, indicating that the organic anion has stronger self-organization behavior with quaternary ammonium cationic Gemini surfactants.     

有机相变乳液中HCFC–141b水合物生成及稳定性

为了促进水合物形成，在HCFC–141b、有机相变材料（正癸酸和十二醇）和水体系中添加表面活性剂Tween 80和Span 80作为乳化剂，采用高速搅拌的方法制备了有机相变材料-表面活性剂-制冷剂-水乳液体系，增大水分子与制冷剂的接触面积。实验研究了静态条件下有机相变材料和表面活性剂添加量对水合物形成的影响。研究结果表明添加乳化剂可以有效提高水合物的蓄冷量，减少水合物形成诱导时间，降低水合物生成的随机性；温度越低，水合物促进效果越好。水合物生成/分解循环实验表明，添加Tween 80的乳液体系的稳定性好，有机相变乳液提高了水合物生成/分解循环过程的稳定性。     

Molecular thermodynamic model for compounding of multiple surfactants

Surfactants are widely used in the actual industrial production. Generally, it is a compound system of multiple surfactants to make use of the characteristics of different components, so that the compound system has better performance than a single surfactant. The compounding mechanism of multiple surfactants is still an interesting topic. In this paper, experimental and theoretical models are used to study the synergistic effect among the components of mixed surfactants. Firstly, based on Flory-Huggins theory, the molecular thermodynamic model of the multi-component surfactant system is derived. The interaction parameters of the two systems are correlated through the experimental data of the binary system. The critical micelle concentration (cmc) of the multi-component system and the phase composition of the mixed surfactant micelle can be predicted. The calculated results of the three-component surfactant system model are in good agreement with the experimental values.     

多元表面活性剂复配的分子热力学模型研究

表面活性剂在实际工业生产中有着广泛应用,一般多为多种表面活性剂的复配体系,利用不同组分的特性,使得复配体系具有比单一表面活性剂更优越的性能,而多元表面活性剂复配机理仍不是很清楚。采用实验与理论模型相结合的方法,研究混合表面活性剂各组分间的协同效应。首先以Flory-Huggins理论为基础,推导了多元表面活性剂体系的分子热力学模型,通过二元系实验数据关联出两两相互作用参数,可对多元体系临界胶束浓度(cmc)与混合表面活性剂胶束相组成进行预测,三元表面活性剂复配体系模型计算结果与实验值吻合较好。     

Improving Gas Sequestration by Surfactant‐Alternating‐Gas Injection: A Comparative Evaluation of the Surfactant Type and Concentration

Gas injection into porous subsurface geological formations for geological storage is currently considered the most preferable and practicable means of reducing greenhouse gases due to the huge capacity of deep saline aquifers. Residual trapping of gas plays an important role in immobilization of injected gas into an aquifer. Surfactant‐alternating‐gas (SAG) injection can be used as a mobility control method in gas sequestration and several simulation studies explained different aspects of residual‐gas trapping. However, research in this field is inconclusive and needs more attention to develop a better understanding. In this work, we used 3 different surfactants from different classes at various concentrations to assess gas‐sequestration efficiency using SAG methods in carbonate and sandstone rocks. This work is the first of its kind on the comparative performance of different surfactants for gas sequestration in different rocks. The surfactants were hydrocarbon zwitterionic, fluorinated zwitterionic, and nonionic. It was found that residual‐gas saturation increases by increasing the surfactant concentration. The increase in residual trapping with surfactant concentration also depends on the type of surfactant and rock. In both rock types considered, the best performance was achieved using fluorinated zwitterionic surfactants followed by hydrocarbon zwitterionic surfactants. In addition, a synergetic effect between hydrocarbon and fluorinated surfactants further improves the residual‐gas saturation. The residual‐gas trapping was higher in the tight sample compared to highly permeable samples. This will help in developing an understanding of surfactant optimization and selection for gas sequestration using the SAG method.     

Synergism and Performance for Systems Containing Binary Mixtures of Anionic/Cationic Surfactants for Enhanced Oil Recovery

The surfactant structure–performance relationship and application properties in enhanced oil recovery (EOR) for binary mixtures of anionic and cationic surfactants are presented and discussed. A polyoxyethylene ether carboxylate anionic surfactant was blended with a quaternary ammonium chloride cationic surfactant and tested for a high-temperature, low-salinity, and high-hardness condition as found in an oil reservoir. These mixtures were tailored by phase behavior tests to form optimal microemulsions with normal octane (n-C8) and crude oil having an API gravity of 48.05°. The ethoxy number of the polyoxyethylene carboxylate anionic surfactant and the chain length of the cationic surfactant were tuned to find an optimal surfactant blend. Interfacial tensions with n-C8 and with crude oil were measured. Synergism between anionic and cationic surfactants was indicated by surface tension measurement, CMC determination, calculation of surface excess concentrations and area per molecule of individual surfactants and their mixtures. Molecular interactions of anionic and cationic surfactants in mixed monolayers and aggregates were calculated by using regular solution theory to find molecular interaction parameters β ^σ and β ^M . Morphologies of surfactant solutions were studied by cryogenic TEM. The use of binary mixtures of anionic/cationic surfactants significantly broadens the scope of application for conventional chemical EOR methods.     

Formulation of ultralow interfacial tension systems using extended surfactants

Inspired by the concept of lipophilic and hydrophilic linkers, extended surfactants have been proposed as highly desirable candidates for the formulation of microemulsions with high solubilization capacity and ultralow interfacial tension (IFT), especially for triglyceride oils. The defining characteristic of an extended surfactant is the presence of one or more intermediate-polarity groups between the hydrophilic head and the hydrophobic tail. Currently only limited information exists on extended surfactants; such knowledge is especially relevant for cleaning and separation applications where the cost of the surfactant and environmental regulations prohibit the use of concentrated surfactant solutions. In this work, we examine surfactant formulations for a wide range of oils using dilute solutions of the extended surfactant classes sodium alkyl polypropyleneoxide sulfate (R-(PO) _x −SO₄Na), and sodium alkyl polypropyleneoxide-polyethyleneoxide sulfate (R-(PO) _y -(EO) _z −SO₄Na). The IFT of these systems was measured as a function of electrolyte and surfactant concentration for polar and nonpolar oils. The results show that these extended surfactant systems have low critical micelle concentrations (CMC) and critical microemulsion concentrations (CμC) compared with other surfactants. We also found that the unique structure of these extended surfactants allows them to achieve ultralow IFT with a wide range of oils, including highly hydrophobic oils (e.g., hexadecane), triolein, and vegetable oils, using only ppm levels of these extended surfactants. It was also found that the introduction of additional PO and EO groups in the extended surfactant yielded lower IFT and lower optimum salinity, both of which are desirable in most formulations. Based on the optimum formulation conditions, it was found that the triolein sample used in these experiments behaved as a very polar oil, and all other vegetable oils displayed very hydrophobic behavior. This unexpected triolein behavior is suspected to be due to uncharacterized impurities in the triolein sample, and will be further evaluated in future research.