This work studied the effects of a water-soluble quaternary ammonium salt (called DA 50) on the growth, wettability, and agglomeration of cyclopentane (CP) hydrate crystals and methane (CH₄)/propane (C₃H₈) hydrate crystals. The impact on these properties of adding 4 wt % NaCl to the DA 50 solution was also investigated. The hydrates were formed from water/CP, water/(CP + n-octane (n-C8)), and water/(CP + n-dodecane (n-C12)) mixtures at atmospheric pressure and from a water/n-C8/(CH₄ + C₃H₈) mixture under pressure (about 67 bar). Experiments were performed at a subcooling of 6 °C in the case of the CP hydrates and 9–10 °C in the case of the CH₄/C₃H₈ hydrates. In both hydrate systems, adding NaCl to the surfactant solution of 0.1 or 1 wt % DA 50 led to the formation of individual oil-wettable pyramidal crystals. Without salt, the hydrate formed a water-wettable shell that covered the water/oil interface just as the system without surfactant did. The antiagglomeration performance of the 1 wt % DA 50 solution was evaluated by performing torque measurements in an agitated batch reactor at a water cut of 30 vol %. Without NaCl, torque increased with the amount of CP hydrates. The system formed a nonflowable jelly-like phase, with water as the continuous phase, until a phase inversion occurred. From there on torque significantly decreased and the system became a flowable dispersion of large hydrate particles (∼700 μm) in the CP phase. With 4 wt % NaCl, the system consisted of small (∼70 μm) hydrate particles dispersed in the CP phase and the torque signal remained constant throughout the hydrate crystallization process. The torque profiles obtained at concentrations of 0 or 4 wt % NaCl for the CP hydrates and the CH₄/C₃H₈ hydrates were similar, suggesting analogous states for both systems. For both hydrate systems, adding NaCl to the DA 50 solution led to the formation of oil-wettable hydrates and drastically improved the antiagglomeration performance of the surfactant molecules, revealing a correlation between the formation of individual crystals and the antiagglomeration performance of the surfactant. The similarity between the growth patterns and shapes of the CP–hydrate crystals and the CH₄/C₃H₈–hydrate crystals confirmed that CP hydrates are an interesting model for evaluating the antiagglomeration performance of surfactants.

中文翻译：

---

季铵盐对II型水合物晶体生长，润湿性和团聚的影响

这项工作研究了水溶性季铵盐（称为DA 50）对环戊烷（CP）水合物晶体和甲烷（CH ₄）/丙烷（C ₃ H ₈）水合物晶体的生长，润湿性和附聚的影响。还研究了向DA 50溶液中添加4 wt％NaCl对这些性能的影响。水合物是从水/ CP，水/（CP +形成ñ -辛烷（Ñ 1 -C 8）），和水/（CP + Ñ -dodecane（Ñ -C12））在大气压力和从水/混合物Ñ - C8 /（CH ₄ + C ₃ H ₈）混合物在压力下（约67 bar）。对于CP水合物，在6°C过冷条件下进行实验；对于CH ₄ / C ₃ H ₈，在9–10°C过冷条件下进行实验水合物。在两种水合物体系中，将NaCl添加到0.1或1 wt％DA 50的表面活性剂溶液中会导致形成单个可油润湿的棱锥体晶体。没有盐时，水合物形成了可水润湿的壳，覆盖了水/油界面，就像没有表面活性剂的系统一样。通过在搅拌的分批反应器中以30vol％的含水量进行扭矩测量来评估1wt％DA 50溶液的抗附聚性能。如果没有NaCl，扭矩随CP水合物的量而增加。该体系以水作为连续相形成了不可流动的果冻状相，直到发生相转化。从那时起，扭矩显着降低，系统变成了在CP相中可流动的大水合物颗粒（〜700μm）分散体。用4 wt％的氯化钠，该系统由分散在CP相中的小水合物颗粒（约70μm）组成，扭矩信号在整个水合物结晶过程中保持恒定。CP水合物和CH在0或4 wt％NaCl浓度下获得的扭矩曲线₄ / C ₃ H ₈水合物相似，表明两个系统的状态相似。对于两种水合物体系，在DA 50溶液中添加NaCl导致形成可油润湿的水合物，并显着改善了表面活性剂分子的抗附聚性能，揭示了单个晶体的形成与表面活性剂的抗附聚性能之间的相关性。CP水合物晶体和CH ₄ / C ₃ H ₈水合物晶体的生长模式和形状之间的相似性证实，CP水合物是评估表面活性剂抗附聚性能的有趣模型。