| Molecular Dynamics and Monte Carlo computer simulations are employed to model adsorption and diffusion of fluids composed of small molecules and their mixtures in molecular sieves, a family of crystalline adsorbents with a regular network of nanopores having dimensions on the order of 10 Angstroms. Because the dimensions of these nanopores are of the same magnitude as that of the adsorbate molecules, no simple models for adsorption or diffusion will correctly predict their behavior. Instead, simulations provide a molecular-level insight.; The foundations for understanding the behavior of the adsorbed fluid in terms of the fundamental thermodynamics and molecular physics are established. Using five progressively more complicated models of adsorption, which include adsorbents with smooth surfaces, rigid atomistic structures, and dynamic atomistic structures, ranging over twenty materials, for single component and binary fluids, adsorption isotherms are obtained and the dependence of the isotherms on nanopore size, nanopore shape, and bulk pressure are explained in terms of interaction energies, entropies, and density distributions.; Two models of diffusion in molecular sieves are developed and examined. These models incorporate (1) blockage and percolation in zeolite-A and zeolite-Y and (2) the transition from uni-directional to single-file diffusion in the one-dimensional sieve, AlPO{dollar}sb{lcub}4sp-{rcub}{dollar}5. For both models, computer simulations, NMR experiments, and analytical theories are presented. Agreements and discrepancies between the three approaches are discussed.; The impact of this thesis is that the fundamental principles of adsorption and diffusion in nanoporous materials are established, with the intention of harnessing this behavior for the design of novel industrial applications. |
