The molecular distribution and diusion of water confined in hydrophobic nanopores were studied by molecular dynamics simulations (MD). We found these water molecules have some unusual behavior than that of the bulk. The density profiles are extremely inhomogeneous and some vacuums and clusters occur in small-size pores at lower density. The diusivity in nanopores is much lower than that of the bulk, and it decreases as the pore width decreases. The diusivity in channel parallel direction oDxp are 4-10 times larger than that in channel perpendicular direction oDy; Dzpat higher temperatures.

The azeotropic data of the cyclohexane+2-propanol+ethyl acetate+butanone quaternary system were measured by using a stainless steel azeotrope apparatus developed by the authors at elevated pressures of 101.3, 302.0, 502.0, 702.0, and 902.0 kPa and predicted by using the Wilson and NRTL activity coefficient models with the paired energy parameters obtained from binary azeotropic data of the six corresponding systems. The calculated results demonstrate that the predicted data are in good agreement with the experimental, and the Wilson and NRTL equations are of comparable accuracy in the prediction of azeotropes for this miscible quaternary system at elevated pressures.

A new stainless steel apparatus for measuring azeotropic points of binary as well as multicomponent systems at elevated pressures has been developed. The azeotropic temperatures and compositions of six binary systems composed of cyclohexane, 2-propanol, ethyl acetate, and butanone were determined at elevated pressures, correlated by empirical equations with pressure, and predicted by the UNIFAC group contribution method. The calculations demonstrate that the correlated data are in good agreement with experimental values.

The transport properties, including the diffusivity and viscosity, of water confined in hydrophobic nanopores and nanoslits were studied by molecular dynamics simulations. The results show that the diffusion coefficient in nanopores and nanoslits is markedly lower than that in the bulk. But the viscosity is much larger than that in bulk. The parallel diffusion coefficient is obviously larger than the perpendicular ones. The diffusion coefficient in the channel pore is ever less than that in the slit pore at the same pore width, but the viscosity is larger. The temperature and density affect significantly the diffusivity and viscosity in nanopores and nanoslits. Lower density water exhibits some special characteristics on density profiles in nanopores and nanoslits at lower temperatures, and the density profiles show a change from homogeneous to inhomogeneous as the pore width is educed. Even clusters occurred in micropores.

The self-diffusion coefficients were calculated by molecular dynamics simulations and the effects of pore width, temperature, and fluid density on diffusion behavior of simple fluid argon and polar fluid water confined in micropores were analyzed and studied.Amathematical model describing diffusion behavior of fluids confined in micropores was proposed from the theories of molecular dynamics and molecular kinematics, and validated on the basis of the simulation results at various conditions. The model indicates that the diffusion coefficient is proportional to the square root of the pore width and to the temperature divided by the density squared. It is applicable to either liquid or gas states and only two parameters are required.