Ibrahim, Abdulhaqq Ameen (2016-08). Effect of Pore Size Distribution on Multiphase Equilibrium of Fluids Confined in Porous Media. Master's Thesis. Thesis uri icon

abstract

  • It is a well-known fact that the thermophysical properties of confined fluids (intraparticle) can be significantly different from those of bulk phases (interparticle). Such difference becomes more pronounced as the pore size decreases. The effect of confinement on the phase behavior of fluids is important for many applications, such as in adsorptive separations, extraction of shale oil and gas, and heterogeneous catalytic systems. The characterization of the porous solid material is of great relevance because the interactions of the solid with the molecules of the fluid play a major role in any modeling of confined fluid behavior. However, many solids are heterogeneous, in the sense that they have complex network structures, and pores of different sizes and of different chemical affinity with respect to the adsorbed molecules. Their effect on the properties of fluids entrapped in the porous space is not well captured by many models. One of the most important pieces of information to characterize solids is their pore size distribution, which is an intrinsic property of the material. This thesis presents a method to account for the effect of pore size distributions on the phase behavior of fluids confined in porous media. Multiphase equilibrium calculations of confined fluids in solid adsorbents were carried out using the Peng-Robinson equation of state extended to confined fluids, while different pore size distributions of solid adsorbents were considered. The results obtained from the fitting of pure-component adsorption data revealed that the model correlations for fluids adsorbed in bipore solids were better when pore size heterogeneity was considered in the formulation, as opposed to the assuming a homogeneous solid. Adsorption of n-hexane on MCM-48 solids with multiple pore size distributions was simulated as a model system, showing a trend of increasing accuracy of adsorption data fitting as the number of pore sizes increases. The sensitivity of the model to adsorption temperature was established by a few examples, suggesting that the model agreement with experimental data is better at higher temperatures.
  • It is a well-known fact that the thermophysical properties of confined fluids (intraparticle) can be significantly different from those of bulk phases (interparticle). Such difference becomes more pronounced as the pore size decreases. The effect of confinement on the phase behavior of fluids is important for many applications, such as in adsorptive separations, extraction of shale oil and gas, and heterogeneous catalytic systems. The characterization of the porous solid material is of great relevance because the interactions of the solid with the molecules of the fluid play a major role in any modeling of confined fluid behavior. However, many solids are heterogeneous, in the sense that they have complex network structures, and pores of different sizes and of different chemical affinity with respect to the adsorbed molecules. Their effect on the properties of fluids entrapped in the porous space is not well captured by many models. One of the most important pieces of information to characterize solids is their pore size distribution, which is an intrinsic property of the material.

    This thesis presents a method to account for the effect of pore size distributions on the phase behavior of fluids confined in porous media. Multiphase equilibrium calculations of confined fluids in solid adsorbents were carried out using the Peng-Robinson equation of state extended to confined fluids, while different pore size distributions of solid adsorbents were considered. The results obtained from the fitting of pure-component adsorption data revealed that the model correlations for fluids adsorbed in bipore solids were better when pore size heterogeneity was considered in the formulation, as opposed to the assuming a homogeneous solid. Adsorption of n-hexane on MCM-48 solids with multiple pore size distributions was simulated as a model system, showing a trend of increasing accuracy of adsorption data fitting as the number of pore sizes increases. The sensitivity of the model to adsorption temperature was established by a few examples, suggesting that the model agreement with experimental data is better at higher temperatures.

publication date

  • August 2016