Lattice Monte Carlo Simulations of Phase Separation and Micellization in Supercritical CO_2/Surfactant Systems:Effect of CO_2 Density

摘要

Lattice Monte Carlo simulations are used to study the effect of nonionic surfactant concentration and CO_2 density on the micellizaiton and phase equilibria of supercritical CO_2/surfactant systems.The interacton parameter for carbon dioxide is obtained by matching the critical temperature of the model fluid with the experimental critical temperature.Various properties such as the critical micelle cocentration and the size,shape,and structure of micelles are calculated,and the phase diagram in the surfactant concentration-CO_2 density space is constructed.On increasing the CO_2 density,we find an increase in the critical micelle concentration and a decrease in the micreasing the CO_2 density,we find an increase in the critical micelle concentration and a decrease in the micellar size;this is consistent with existing experimental results.The variation of the micellar shape and structure with CO_2 density shows that the micelles are spherical of the micellar corona increases with increasing CO_2 density.The redicted phase diagram is in qualitative agreement experimental pahsediagrams for nonionic surfactactants in carbon dioxide.