Mesoporous materials are being widely used in the chemical industry in various environmentally friendly separation processes and as catalysts. Our research can be broadly described as an effort to understand the behavior of fluids confined in such materials. More specifically we try to understand the influence of state variables like temperature and pore variables like size, shape, connectivity and structural heterogeneity on both the dynamic and equilibrium behavior of confined fluids. The dynamic processes associated with the approach to equilibrium are largely unexplored. It is important to look into the dynamic behavior for two reasons. First, confined fluids experience enhanced metastabilities and large equilibration times in certain classes of mesoporous materials, and the approach to the metastable/stable equilibrium is of tremendous interest. Secondly, understanding the transport resistances in a microscopic scale will help better engineer heterogeneous catalysts and separation processes. Here we present some of our preliminary studies on dynamics of fluids in ideal pore geometries. The tool that we have used extensively to investigate the relaxation dynamics of fluids in pores is the dynamic mean field theory (DMFT) as developed by Monson[P. A. Monson, J. Chem. Phys., 128, 084701 (2008) ]. The theory is based on a lattice gas model of the system and can be viewed as a highly computationally efficient approximation to the dynamics averaged over an ensemble of Kawasaki dynamics Monte Carlo trajectories of the system. It provides a theory of the dynamics of the system consistent with the thermodynamics in mean field theory. The nucleation mechanisms associated with confined fluid phase transitions are emergent features in the calculations. We begin by describing the details of the theory and then present several applications of DMFT. First we present applications to three model pore networks (a) a network of slit pores with a single pore width; (b) a network of slit pores with two pore widths arranged in intersecting channels with a single pore width in each channel; (c) a network of slit pores with two pore widths forming an array of ink-bottles. The results illustrate the effects of pore connectivity upon the dynamics of vapor liquid phase transformations as well as on the mass transfer resistances to equilibration. We then present an application to a case where the solid-fluid interactions lead to partial wetting on a planar surface. The pore filling process in such systems features an asymmetric density distribution where a liquid droplet appears on one of the walls. We also present studies on systems where there is partial drying or drying associated with weakly attractive or repulsive interactions between the fluid and the pore walls. We describe the symmetries exhibited by the lattice model between pore filling for wetting states and pore emptying for drying states, for both the thermodynamics and dynamics. We then present an extension of DMFT to mixtures and present some examples that illustrate the utility of the approach. Finally we present an assessment the accuracy of the DMFT through comparisons with a higher order approximation based on the path probability method as well as Kawasaki dynamics.

Ce travail de thèse inclut deux parties : i) l'étude fondamentale de la formation de cristaux zéolithiques ; et ii) la préparation de massifs zéolithiques de taille centimétriques à porosité interparticulaire contrôlée. La première partie de ce travail est donc consacrée à l'étude de l'effet de la microstructure (propriétés physiques et texturales) et de la composition chimique du gel sur la vitesse de nucléation et la taille des cristaux formés. Les résultats de cette étude se résument par le rôle important que joue la composition du gel (plus particulièrement sa concentration en hydroxyde de cation alcalin) sur le degré de polymérisation des particules du gel, la détermination de sa microstructure et par conséquent sur la vitesse de nucléation des zéolithes et la taille des cristaux. Les connaissances acquises dans la première partie ont été utilisées dans le développement du deuxième objective. Notamment, la préparation de massifs zéolithiques de taille centimétrique de types structuraux *BEA et MFI. Le contrôle post-synthèse de la porosité interparticulaire de ces massifs était essentiel pour leur utilisation dans des applications bien précises. A cette fin, une méthode en deux étapes, comportant un assemblage de nanocristaux de zéolithes préformés (en présence ou en absence d'un liant) puis un traitement de croissance secondaire pour l'élimination de la porosité interparticulaire, a été mise en œuvre. Plusieurs traitements de croissance secondaire furent évalués selon le type de zéolithe étudié. Une attention particulière fut accordée à l'étude de l'évolution du liant au cours des processus de préparation et de calcination des massifs zéolithiques. / The present study includes two parts: i) fundamental study of zeolite nucleation-crystal growth mechanism; and ii) preparation of zeolite bodies with controlled interparticle porosity.Thus the first part of the present work deals with the study of the effect of physico-chemical characteristics of initial hydrogel on the nucleation and crystal growth kinetics of zeolite crystals. The obtained data revealed that the concentration of alkali metal hydroxide in the initial system controls the rate of polymerization of the aluminosilicate species, the size of initial gel particles, and the textural properties of the gel. Consequently, the following reaction was to great extent predetermined by the events taking place during mixing the initial reactants.The second part of this work was targeted at the preparation of centimeter-sized zeolite bodies of *BEA- and MFI-type with reduced to minimum inter-particle porosity. A preparation method consisting in assembling of zeolite nanocrystals (with or without a binder) was developed and further optimized. The preformed bodies were subjected to a hydrothermal treatrnent in a fresh zeolite synthesis solution in order to till up the inter-particle porosity. Depending onthe zeolite type, different methods of secondary growth treatrnents were employed. A particular attention has been paid on the study of the binder evolution during the calcination and secondary growth processes.