表面活性剂对气体水合物生成诱导时间的作用机理

Reaction mechanism between surfactant and induction time of gas hydrate formation

利用可视化水合物实验设备,研究了摩尔浓度均为1.0×10-3mol/L的3组溶液(T40、T40/T80(1∶1)、T40/T80(4∶1))体系中表面活性剂对气体水合物生成诱导时间的影响,运用直接观测法测定了水合物广义诱导时间,基于物质传递模型、水合物晶核生长模型及相平衡驱动力方程对实验结果进行了分析。结果表明:表面活性剂的增溶作用促使气体分子在溶液中过饱和,促进了体相-水合物晶体之间的物质传递,为气体水合物反应过程中主体分子(水)和客体分子(气体)的络合提供了驱动力;表面活性剂的自身结构特性及其水溶液的状态决定了其在超过临界胶束浓度(CMC)后胶束化,进而束缚气体分子并与水分子形成团簇,团簇的增多、胶束内空余空间的减少,使团簇互相碰撞接触的机会增多,促进了晶核形成;表面活性剂的增溶作用显著降低了被增溶物的化学势,使体系变得更加稳定,促进了水合物生成相平衡。比较表明:表面活性剂T40在促进水合物晶核生成、缩短诱导时间方面的作用显著。

The influences of surfactants on induction time in three types of solution with equal concentration of 1.0×10^-3mol·L^-1（T40, T40/T80 （1： 1）, T40/T80 （4 ： 1）） were studied by means of visual hydrate experimental equipment and generalized induction time was measured by direct observation method. Then the experimental results were analyzed based on the mass transfer model, the model of hydrate crystal nucleus growth and the driving force equation of phase equilibrium. The results show that solubilization of surfaetant makes gas molecules supersaturated which promotes the mass transfer from bulk phases to hydrate, and provides driving force for eomplexation of host molecules （water） and guest molecules in the reaction process of gas hydrate formation, the structural characteristics of surfaetant and its aqueous solution state determine itself to become mieelle when CMC is exceeded which binds gas molecules and forms clusters with water molecule, the increase of clusters and decrease of unoccupied space in micelle increase the opportunities of clusters collision which promotes the crystal nucleus formation; solubilization of surfactant evidently decreases the chemical potential of solubilized mass, thus stabilizing the reaction system and promoting the phase equilibrium of hydrate formation. It is found by comparisons that surfactant T40 has notable effects on promoting hydrate nucleus formation and shortening induction time.