盐水中月桂酰胺丙基二甲铵基羟磺基甜菜碱的含量测定及热稳定性

随着注气技术在塔里木油田高温高盐油藏温度为110~150℃，水中盐含量为（22~27）×10⁴mg/L]的推广与应用，高温高盐条件下封堵气窜用泡沫的研究日益受到关注。月桂酰胺丙基二甲铵基羟磺基甜菜碱在高盐含量水溶液中具有优异的发泡性能，但该表面活性剂的热稳定性尚不明确。利用示差检测器，选择Shim-pack VP-ODS 250L×4.6型色谱柱以及甲醇和水组成的混合溶剂为流动相，通过优选甲醇和水的比例、流动相流速和柱温，建立了测定盐含量为25×10⁴mg/L的水溶液中月桂酰胺丙基二甲铵基羟磺基甜菜碱含量的高效液相色谱法。热稳定性评价表明，月桂酰胺丙基二甲铵基羟磺基甜菜碱经110℃处理90 d后含量保留率高于60%，经130℃处理90 d后含量保留率低于30%，其热解行为符合一级动力学方程。对热处理后的表面活性剂溶液进行液相色谱-质谱分析表明，月桂酰胺丙基二甲铵基羟磺基甜菜碱主要在酰胺处发生水解而失去表面活性。

Content determination of lauroamide propyl dimethylammonium hydroxylsulbetaine in brine and analysis of its thermal stability

With the popularization and application of gas injection technology in high-temperature and high-salinity reservoirs (temperature:110-150℃; salt content in water:(22-27)×10⁴ mg/L) of Tarim oilfield, increasing attention is paid to the research of using foam to plug gas channelling under high temperature and high salinity conditions. Lauramide propyl dimethylammonium hydroxylsulfobetaine (LHSB) is characterized by excellent foaming properties in high-salinity water, but the thermal stability of its surfactant is still not clear. By using differential detector and selecting Shim-pack VP-ODS 250L×4.6 chromatographic column and mixed solvent composed of methanol and water as the mobile phases, the high performance liquid chromatography (HPLC) for determining the content of LHSB in high-salinity water (25×10⁴mg/L) has been established by optimizing the ratio of methanol to water, flow rate of mobile phase and column temperature. Thermal stability evaluation shows that the reservation rate of LHSB content after treatment at 110℃ for 90 days was higher than 60%, while that after treatment at 130℃ for 90 days was lower than 30%, and its pyrolysis behavior is in line with the first-order kinetic equation. In addition, the LC-MS analysis of the surfactant after thermal treatment shows that LHSB hydrolysis mainly occurs at the amide site, thus losing its surface activity.