Synthesis And Properities Of Alkanolamide Surfactant

In EOR, reducing the oil/water interfacial tension to ultra-low (10-3 mN·m-1) has been proven to be the most important factor for screening the chemical flooding formula and study the mechanism of ultra-low interfacial tension. In this paper, we investigated how the synthesis condition and salt concentration influence the interfacial activity of nonionic surfactant alkanolamide. Combined with IR-ATR spectra, interfacial dilational rheology and molecule dynamic, the mechanism of alkanolamide achieving ultra-low interfacial tension and oil adaptation under different condition was studied to provide the theoretical basis for building up the structure-performance relationship of surfactants and finding the mechanism of ultra low interface tension.This thesis can be divided into three parts:In Chapter I, nonionic surfactant Laurel alkanolamide was synthesized by "one step" method using methyl laurate and diethanol amine as sunstrates and used Sodium methylate as catalyst. The crude product was purified via petroleum ether and water respectively. The Laurel alkanolamide with different purity degree was analyzed by IR and 1H-NMR characterizations. It was found that the nonionic surfactant Laurel alkanolamide synthesized by "one step" was able to decrease the oil/water interface tension to ultra-low at low concentration without co-surfactants and had surprising oil phase adaptability, which provided a perfect model not only to study the theoretical mechanism achieving ultra-low interface tension but also distinguish the contribution of the molecular interfacial array behavior of surfactants and the concomitants on the interfacial activity. The detailed molecular array behavior of LAA and the concomitants on oil/water interface was investigated by molecular dynamics (MD). It was found that the concomitants coexist at the oil/water interface with LAA and distribute at the different position in the interfacial layer, resulting in the high interfacial activity and oil phase adaptability. The interfacial tension activity of Lauric diethanolamide influenced by synthesized such as molar ratio, reaction time and amount of catalyst was studied by single variable method.In Chapter Ⅱ, we examined the role of Ca2+, Mg2+ on achieving the ultra-low interfacial tension (10-3mN/m) for lauryl alkanolamide at the dodecane-water interface, which provide a perfect model to study the theoretical mechanism of ultra-low interface tension phenomena. Molecular dynamic simulation combined with IR-ATR approach were used to investigate the interfacial molecular behavior, and it was found that the distribution of water molecules in the interfacial layer were changed when Ca2+, Mg2+ were added to the system. Ca2+, Mg2+ could hydrate water molecules through strong hydration interaction, so the number of water molecules within the interface were decreased which resulted in the decrease of the interaction between hydrophilic head group and water molecules, the hydrophobicity of alkanolamide was enhanced and the interfacial tension decreased. IR-ATR spectra also implied that the hydration capacity of Mg2+is stronger than Ca2+. Therefore, Mg2+ could enhance the hydrophobicity of the surfactants in larger degree than Ca2+, and the ability of Mg2+ to reduce the oil/water interfacial tension is stronger than Ca2+.In Chapter Ⅲ, oil/water interfacial dilational rheology of alkanolamide micelle with or without solubilized decane molecules was studied at different oscillation frequency using Tracker, France. It is very interesting to point out that the rheological behavior of alkanolamide solution is much more different from that of the solution of swelling micelle of alkanolamide solubilizing decane. It was found out that the the interfacial dilation modulus of the swelling micelle solution has low relevance with the bulk oil phase compared with surfactant solution to guarantee its oil phase adaptability, which is mainly because the interface formation energy decreased when decane molecules were solubilized between the hydrophobic chains of alkanolamide. When another oil phase was put in the solution, molecules in the swelling micelles were thermodynamically driven to assemble to form interface layer, as a result, the relaxation of alkanolamide is mainly influenced by decane molecules solubilized and has little associated with the added oil phase, therefore showed minor change in dilational modulus. The interface formation energy of the swelling micelle of alkanolamide solubilizing suitable amount of decane molecules was the lowest, which ensured oil phase adaptability.This paper mainly studied the influence of concomitants on the interfacial activities of lauric alkanolamide. The interfacial tension of alkanolamide soulution to alkane could be decreased to ultra-low by changing the salinity, which provided a perfect model to study the theoretical mechanism achieving ultra-low interface tension. Combined with IR-ATR spectroscopy, the mechanism of the effects of Ca2+, Mg2+ to the interfacial properties was brought out. The interface dilational rheology of alkanolamide swelling micelles was studied to find out the mechanism of getting oil phase adaptability. We hope to provide the theoretical basis for building up the structure-performance relationship of surfactants and guidance for designing EOR flooding agent with ultra low interfacial tension.The innovations of the thesis are listed as follows:(1) The concomitants of surfactant alkanolamide were found to have synergism effect with the surfactant and could increase the interfacial activities abruptly, which provide a new way not only enhance the interfacial capacity of surfactant, but also can avoid the energy waste and performance degradation.(2) Combined molecular dynamic with FT-IR (ATR), how the inorganic ions influence the interfacial activity of surfactant molecules was investigated, which provided important information revealing the theoretical mechanism achieving ultra-low interface tension.(3) Through interface dilational rheology, the mechanism how the swelling micelle of alkanolamide getting the oil adaptation was brought out, which provided useful guidance for designing the EOR flooding formula with oil phase adaptbility.