静电作用构筑的新型表面活性剂及其性能.pdf

第 53 卷 第 8 期2023 年 8 月Vol.53 No.8Aug.2023865 日 用 化 学 工 业（中英文）China Surfactant Detergent&Cosmetics Preparation and properties of a novel surfactant constructed by electrostatic interactionsJunhuiWu,TingPan,XiaomeiPei*,ZhenggangCui（The Key Laboratory of Synthetic and Biological Colloids,Ministry of Education,School of Chemical and Material Engineering,Jiangnan University,Wuxi,Jiangsu 214122,China）Abstract:Taking stearic acid as the raw material,N-（2-（dimethylamino）ethyl）stearamide（C18N2N）was synthesized.A new surfactant was prepared by mixing C18N2N and cinnamic acid（TA）with fixed ratio.This surfactant was formed by non-covalent electrostatic interactions,which avoided complicated synthetic procedures.The surface activity and rheological properties of the surfactant were investigated with a surface tensiometer and a rheometer.The critical micelle concentration（cmc）and the surface tension at cmc（cmc）of the surfactant were 0.11 mmol/L and 32.4 mN/m,indicative of strong aggregation and adsorption ability.The maximum amount adsorbed（max）and the minimum molecular area occupied（Amin）were 2.77 mol/m2 and 0.6 nm2.Wormlike micelles were formed at the concentration of 25 mmol/L.When the concentration was over 100 mmol/L,the zero-shear viscosity（0）abruptly increased and then reached the maximum value for the surfactant of C18N2N/TA containing 150 mmol/L TA.The solution viscosity was as high as 1 761.38 Pa s.The effects of temperature on the rheological behavior were also considered.With the increase of temperature,the viscosity gradually increased.And when the temperature reached 40,0 of the solution with the concentration of 100 mmol/L achieved the maximum value of 1 370.386 Pa s.When the temperature continued to rise,0 began to decrease with further increasing temperature.A remarkable viscosity of 305.55 Pa s was still remained at 50.The viscoelastic solutions showed good temperature resistance and shear resistance.The surfactant solutions applied as the fracturing fluid were also investigated.This surfactant also showed excellent sand-carrying performance,and the settling rate of the sand was merely 0.26 cm/min.This surfactant could be simply prepared and showed excellent performance,which expanded the preparation and application field of novel surfactants.Key words:electrostatic interaction;stearic acid;viscoelasticity;fracturing fluidReceived:November 22,2022;Revised:July 17,2023.*Corresponding author.Tel.:[phone],E-mail:.国家自然科学基金（22272063）DOI：10.3969/j.issn.2097-2806.2023.08.002OO-+NNHHIncreasing ofconcentrationOThe illustration of the wormlike micelles formed by C18N2N/TA through electrostatic interactions in aqueous solutions866第 53 卷基 础 研 究日 用 化 学 工 业（中英文）The technology of oil production and exploitation in oil fields is of great importance for the national economy and daily life 1.With the development of society and modern industry,the energy requirement is getting more and more serious 2.The improvement of the efficiency of oil recovery has become particularly important.Fracturing fluid 3,4 is a working fluid used for fracturing oil and gas reservoirs.Through the pressure transmission of fracturing fluid,cracks can be created.It is helpful for oil and gas recovery with the assistance of proppants.Traditional fracturing fluids are mainly composed of polymer components,which can easily block gaps during use,resulting in environmental pollution and reduced recovery efficiency.To meet the needs of sustainable development and oilfield exploitation,the development and application of clean fracturing fluids 5-7 have become the focus of attention.Clean fracturing fluids are mainly composed of surfactants and certain additives,which show excellent performance 4.However,many formulations are considered to be high-cost and are not environmentally friendly.Natural organic acids are mainly from plants or agricultural products,which can be directly extracted and separated.Natural organic acids have the advantages of low toxicity,low cost,mild acidity,and negligible environmental pollution.Natural organic acids are multifunctional nutrients that have physiological effects such as softening blood vessels,promoting calcium and iron absorption,and eliminating fatigue 8.In terms of soil environmental remediation,natural organic acid is also a good leaching agent,which can effectively remove heavy metals in soil and improve soil structure 9.Cinnamic acid is a natural organic acid isolated from cinnamon or benzoin,which has good biocompatibility and renewability.In recent years,the use of non-covalent interactions to prepare surfactants has attracted attention.There are many reports on the use of various acids and amines to prepare surfactants.Similarly,the electrostatic attraction between positive and negative charges 10 have also been utilized to prepare mixed surfactants,e.g.,using 12-3-122Br-and three organic acids with benzene rings as raw materials.By comparing the rheological properties,it is found that the surfactant formed by trans-OHCA and 12-3-122Br-exhibit the most excellent rheological properties.By studying a mixed aqueous solution of trimethylstearylammonium chloride and sodium salicylate,it has been found that when the concentration of trimethylstearylammonium chloride exceeds 87.5 mmol/L,wormlike micelles can be formed in the system 11.This method is simple without cumbersome synthesis or purification processes.In this work,the natural organic acid cinnamic acid（TA）and N-（2-（dimethylamino）ethyl）stearamide（C18N2N）were simply mixed and a novel surfactant was prepared through intermolecular electrostatic interactions.This surfactant did not need complex synthesis and it contained no inorganic salts.静电作用构筑的新型表面活性剂及其性能吴俊辉，潘 婷，裴晓梅*，崔正刚（江南大学 化学与材料工程学院 合成与生物胶体教育部重点实验室，江苏 无锡 214122）摘要：以硬脂酸为原料，合成了长碳链的N-（2-（二甲基氨基）乙基）硬脂酰胺（C18N2N）。将C18N2N与天然有机酸肉桂酸（TA）按一定比例复配，即可得到一种新型表面活性剂。该表面活性剂通过非共价键的静电相互作用而形成，省去了繁琐的合成步骤。通过表面张力仪和流变仪测试了该表面活性剂的表面活性和流变性能，结果表明该表面活性剂的临界胶束浓度和cmc分别为0.11 mmol/L和32.4 mN/m，表现出很强的聚集和吸附能力。在浓度为25 mmol/L时，该表面活性剂即可形成蠕虫状胶束，形成的黏弹溶液具有较好的耐温耐剪切性能。还考查了该新型表面活性剂作为压裂液的应用性质，发现该新型表面活性剂还具有优良的携砂性能，沉降速率仅为0.26 cm/min。该表面活性剂制备简单，性能优良，拓展了新型表面活性剂的制备方法和应用范围。关键词：静电相互作用；硬脂酸；黏弹性；压裂液中图分类号：O647.2 文献标识码：A 文章编号：2097-2806（2023）08-0865-08867第 8 期基 础 研 究JunhuiWu,etal:Preparationandpropertiesofanovelsurfactantconstructedbyelectrostaticinteractions The system exhibited good solubility even at 300 mmol/L.This system also showed excellent rheological properties,forming wormlike micelles at 25 mmol/L,the concentration of which was lower than most wormlike micellar systems and did not require any salt additives 12,13.The newly prepared wormlike micellar system was considered to be applied as fracturing fluid in oilfields.1 Experimental section1.1 MaterialsStearic acid,cinnamic acid,sulfoxide chloride,CH2Cl2,triethylamine and 2-dimethylaminoethylamine were all analytical pure and purchased from Aladdin Reagents（Shanghai,China）.1.2 Methods1.2.1 Synthesis of N-（2-（dimethylamino）ethyl）stearamide（C18N2N）Synthesis of stearoyl chloride.A mixed solution of stearic acid（0.2 mol,56.8 g）and small amount of catalyst 4-dimethylpyridine（DMAP）were added to a three-necked flask.The flask was placed in a water bath.Thionyl chloride（0.3 mol,35.7 g）was added slowly to the above mixture from a dropping funnel.The generated gas was adsorbed by sodium hydroxide solution.After that,the mixture was stirred at 70 for 4 hours.After the reaction was completed,excess thionyl chloride was removed by evaporation under reduced pressure to obtain octadecanoyl chloride.Synthesis of N-（2-（dimethylamino）ethyl）stearamide.2-Dimethylaminoethylamine（0.3 mol,26.5 g）and excessive amount of triethylamine were added into a 250 mL three-necked flask.The mixture was cooled in an ice bath,followed by slowly adding the solution of octadecanoyl chloride in dichloromethane.After that,stirring was continued for further 2 hours.When completed,the reaction system was then poured into a 1 000 mL beaker and washed with weak alkaline water to remove the triethylamine.The residue solution was extracted three times with dichloromethane.The combined organic extracts were dried with magnesium sulfate and the solvent was then removed under vacuum to get the crude N-（2-（dimethylamino）ethyl）stearamide.This crude product was recrystallized from ethanol to get a pure product（43.0 g）.The yield was 60.7%.The synthetic route is shown in Fig.1.1.2.2 Preparation of sample solutionsSpecific amounts of C18N2N,TA and ultrapure water were added into a glass vial followed by mechanical agitation for several minutes at（40.00.1）.Generally,the surfactant was referred to“C18N2N/TA”for simplicity.The molar ratio of C18N2N/TA n（C18N2N）n（TA）was 11.Samples of lower concentrations were obtained by diluting the stock solution with ultrapure water.The concentrations of the solutions were given as the concentration of TA.All the samples were stored at（25.00.1）for about 24 h before measurements.1.2.3 Measurement of surface tensionSurface tension was determined according to the method reported in reference 14.1.2.4 Rheological measurementThe steady-state and dynamic rheological behavior of the system were measured on a rheometer（DHR-3）.The cone was made of standard ETC steel with a diameter of 40 mm and a cone angle of 2.The gap between the center of the cone and the plate was 48 m.To determine the linear viscoelastic region,the system was first subjected to a strain sweep with a frequency of 2.82 rad/s and the appropriate strain value was selected to ensure that subsequent tests of each sample were in the linear viscoelastic region.Each sample was allowed to equilibrate on the plate for 5 min before testing.The temperature was maintained at 25 throughout the experiments.1.2.5 Cryogenic transmission electron microscopy（cryo-TEM）The samples for cryo-TEM observations were prepared in a controlled environment vitrification system（CEVS）.A micro-pipette was used to load 3 mL of solution onto a TEM copper grid which was then blotted with two pieces of filter paper,resulting in the formation of a thin film suspended on the mesh.The grid was then quickly plunged into a-165 reservoir of liquid ethane（cooled by liquid OHOSOCl2ClOH2NNHNONFig.1 Synthetic route of N-（2-（dimethylamino）ethyl）stearamide868第 53 卷基 础 研 究日 用 化 学 工 业（中英文）nitrogen）.The vitrified samples were then stored in the liquid nitrogen until they were transferred to a cryogenic sample holder（Gatan 655）and examined using a Talos F200C（FEI）transmission electron microscope（200 kV）at approximately-174.The phase contrast was enhanced by the underfocus setting.The images were recorded on a Gatan multiscan CCD and processed using a Digital Micrograph.1.2.6 Static sand-carrying performanceThe static sand-carrying performance of a fracturing fluid can be judged by the static settling rate of the proppant.In the static settlement test,the fracturing sand with a diameter of 0.55-0.83 mm was selected.The surfactant fracturing fluid was put into a 100 mL measuring cylinder with stopper and then placed in a water bath of 25.After the fracturing fluid reached the specified temperature,the liquid level height（h）of the measuring cylinder was measured by a ruler.5 g uniform fracturing sand was gently placed at the liquid surface.The time（t）used for the uniform fracturing sand to reach the bottom of the measuring cylinder was recorded.The static settling rate of the proppant in this fracturing fluid was calculated using the equation Up=h/t.2 Results and discussion2.1 Characterization1H NMR spectrum of C18N2N is shown in Fig.2.Chemical shift（）:6.06（s,1H）,3.31（q,2H）,2.42（t,2H）,2.18-2.16（m,8H）,1.63（t,4H）,1.26（d,28H）,0.87（t,3H）.2.2 Surface activityThe surface tension of aqueous solutions of C18N2N/TA 00.51.01.52.02.53.03.54.04.55.05.56.06.57.07.58.03.0028.002.008.152.012.001.000.871.261.632.162.182.423.316.06Fig.2 1H NMR spectrum of C18N2Nat different concentrations was measured using the du Noy ring method.The surface tension curve of C18N2N/TA solution at 25 is shown in Fig.3.The concentration corresponding to the turning point of the curve is the critical micelle concentration（cmc）,and the corresponding surface tension（）is cmc.These two parameters represent the abilities of aggregation and surface tension reduction in aqueous solution,respectively.The smaller the cmc,the stronger the ability to form micelles.Fig.3 showed that the cmc of C18N2N/TA was relatively low.The cmc was 0.11 mmol/L.The cmc was 32.4 mN/m.It indicated that C18N2N/TA could aggregate at low concentration and had strong aggregation ability.In contrast,the system 15 made by mixing C16AMPM（N-3-（dimethylamino）propyl hexadecylamide）with sodium salicylate has cmc of 0.25 mmol/L and cmc of 34.86 mN/m,whose abilities of micellization and surface tension reduction were both weaker than that of C18N2N/TA.In addition,the traditional trimethylstearylammonium bromide has cmc of 0.34 mmol/L and cmc of 40.00 mN/m,which was also inferior to the C18N2N/TA system 16.The maximum amount adsorbed（max）of C18N2N/TA was 2.77 mol/m2.The minimum molecular area occupied at the gas/liquid interface was 0.6 nm2.It indicated that the molecules were arranged tightly at the interface.Meanwhile,it also supported that C18N2N and TA had formed surfactants through electrostatic attractions.2.3 Rheological properties2.3.1 Effect of surfactant concentration on rheological behaviorPlots of steady shear viscosity as a function of Fig.3 Surface tension curve of C18N2N/TA（25）110-7110-6110-5110-4110-3110-230354045505560657075 Surface tension/(mN/m)c/(mol/L)869第 8 期基 础 研 究JunhuiWu,etal:Preparationandpropertiesofanovelsurfactantconstructedbyelectrostaticinteractions shear rate for the C18N2N/TA systems with different concentrations are shown in Fig.4.At low concentrations（25 mmol/L）,C18N2N/TA exhibited shear thinning behavior,which was an uncommon wormlike micellar system at low concentration 12,13.It is known that,among the surfactant systems,shear thinning is a typical feature of forming rod-like or wormlike micelles 17,and the solution exhibits typical non-Newtonian fluid.As the shear rate increases,the wormlike micelles in the solution break under external forces,resulting in a decrease in the viscosity of the system 18.Zero-shear viscosity（0）can be obtained from Fig.4,and the 0-c curve is shown in Fig.5.When the concentration of C18N2N/TA was low,0 was relatively small.As the concentration of C18N2N/TA was increased,0 also increased.When the concentration of TA therein reached 150 mmol/L,the solution viscosity reached its maximum value of 1 761.38 Pa s,indicative of an increase in the length of wormlike micelles in the system.In contrast,in the C16AMPM/sodium salicylate system 15,it has been reported that when the concentration of C16AMPM is 150 mmol/L,0 does not exceed 100 Pa s.As shown in Fig.5,as the concentration of surfactant was further increased,0 would gradually decrease.This indicated that the wormlike micelles were undergoing branching.C18N2N and TA molecules formed