双十二酰胺基甜菜碱的结构及界面性能

Structure and Interfacial Properties of N, N-bis(dodecylamidoethyl)-carboxybetaine

刘学民 李丹萍 杜光劲 贾国亮 崔正刚

LIU Xue-Min LI Dan-Ping DU Guang-Jin JIA Guo-Liang CUI Zheng-Gang

以十二酸、二乙烯三胺等为原料，经酰胺化、甲基化反应合成了N, N-双-(十二酰胺乙基)-N-甲基胺，继而与氯乙酸钠反应制得双十二酰胺基甜菜碱。用红外光谱、质谱分析表征了目标产物的结构。结果表明，所合成的双十二酰胺基甜菜碱具有较好的表面活性，25℃时的临界胶束浓度ccmc为1.2×10-5 mol/L，最低表面张力γcmc为25.38 mN/m，饱和吸附时在气/液界面上的分子截面积为0.28 nm2，小于双十二烷基甲基甜菜碱。双十二酰胺基甜菜碱的耐盐能力较好，0.01 mol/L NaCl对其表面活性的影响很小，ccmc和γcmc有微小下降。将双十二酰胺基甜菜碱与其他表面活性剂复配，在无碱和混合表面活性剂质量分数0.05%~0.3%范围内，大庆原油与模拟地层水相间的界面张力最低达7.16×10-4 mN/m (45℃)。

N, N-bis(dodecylamidoethyl)-carboxybetaine was prepared using sodium chloroacetate and N, N-bis(dodecylamidoethyl)-N-methylamine, which was synthesized by amidation and methylation reaction from dodecanoic acid and diethylenetriamine. And its chemical structure was confirmed by FT-IR and ESI-MS spectrometry. The results showed that N, N-bis(dodecylamidoethyl)-carboxybetaine had superior surface and interfacial activity, with 1.2×10-5 mol/L critical micelle concentration (Ccmc), and 25.38 mN/m the lowest surface tension (γcmc) at 25℃. The minimum area per surfactant molecule at air/solution interface was of 0.28 nm2 at saturated adsorption, which was less than N, N-didodecyl-N-methyl-carboxybetaine. The product had a good tolerance to electrolytes, while 0.01 mol/L NaCl had little effect on Ccmc and γcmc. When N, N-bis(dodecylamidoethyl)-carboxybetaine was mixed with other surfactants, the interfacial tension between Daqing crude oil and connate water reduced to 7.16×10-4 mN/m at 45℃ over a wide surfactant dosage range from 0.05% to 0.3% without adding any alkaline agent.