As-synthesized oleic amido propyl betaine surfactant mixture was developed through a slight modification of a conventional two-step betaine synthesis process of amidation and quaternization reactions. This method is a “direct formulating through synthesis” to achieve a targeted interfacial property (interfacial tension or IFT) of the as-synthesized surfactant. Oil–water IFT was measured in the crude oil–seawater system at 96 °C. The result showed that the as-synthesized surfactant was able to reduce crude oil–seawater IFT to the ultra-low level (<0.01 mN/m). As the finding emerged, the investigation was conducted to identify the elements that would bring the characteristic of ultra-low IFT. The characterization of the surfactant using FTIR, TG-IR, and HPLC suggested that unreacted materials associated with the surfactant remained, such as the carryover of a fatty amide from the intermediate process, residues of N, N trimethylene dimethylamine and sodium chloride as a by-product, and the important newly formed sodium oleate compound that was inadvertently generated via the reaction. The performance of the as-synthesized in seawater condition has been verified and the surface tension plot shows the lowest surface tension point at 0.05 wt.% concentration before developing a plateau region at higher surfactant concentration, indicating that the formation of surfactant micelles has been interrupted by the presence of other components in the solution. The dynamic IFT test performed on the as-synthesized product revealed that it was still able to reduce the crude oil–seawater IFT to an ultra-low level, despite the multiple undesirable components in the surfactant. IFT as low as 3.4 × 10⁻⁴ mN/m for the specific seawater and crude oil composition was obtained at a temperature of 96 °C.

中文翻译：

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合成的油酸酰胺基丙基甜菜碱表面活性剂混合物及其对原油-海水界面张力的影响

通过对酰胺化和季铵化反应的常规两步甜菜碱合成工艺进行稍加修改，可以开发出合成的油酸酰胺基丙基甜菜碱表面活性剂混合物。该方法是“通过合成直接配制”以实现合成后的表面活性剂的目标界面性能（界面张力或IFT）。在原油-海水系统中于96°C下测量了油水IFT。结果表明，合成后的表面活性剂能够将原油-海水IFT降低至超低水平（<0.01 mN / m）。随着发现的出现，进行了调查以识别将带来超低IFT特性的元素。使用FTIR，TG-IR和HPLC对表面活性剂进行表征表明，与表面活性剂相关的未反应物质得以保留，例如中间过程中残留的脂肪酰胺，副产物N，N，三亚甲基二甲胺和氯化钠的残留物以及通过反应无意中生成的重要的新形成的油酸钠化合物。海水条件下合成后的性能已得到验证，表面张力图显示在浓度较高的表面活性剂浓度较高的稳定区域之前，在浓度为0.05 wt。％时最低的表面张力点，表明表面活性剂胶束的形成已被中断解决方案中存在其他组件。对合成后的产品进行的动态IFT测试表明，尽管表面活性剂中存在多种不良成分，但仍能够将原油-海水IFT降低至超低水平。IFT低至3。对于特定的海水和原油成分，在96°C下获得^-4 mN / m。