Directed synthesis and characterization of zeolite nanoparticles

Abstract

Zeolites are a class of materials with ordered micropores (smaller than 2 nm), that can be used for gas separation, catalysis, and adsorption. Structurally, zeolites are composed of SiO₄ tetrahedra sharing corners in an ordered manner. The numerous arrangements of these SiO₄ tetrahedra give zeolites micropores in the forms of channels and cages. Although the applications of each zeolite depends on the spatial arrangements and the sizes of these micropores, size and morphology of zeolite particles are equally important. By preparing zeolite nanoparticles, diffusion paths of zeolite particles can be shortened, total surface area of zeolite particles can be increased, which are beneficial to reducing energy consumption in gas separation, reducing deactivation in catalytic reactions, and increasing adsorption capacities. This dissertation introduces various methods to prepare zeolite nanoparticles. Zeolite nanoparticles prepared with the help of mesoporous carbon templates (hard template) are firstly introduced where the shape and size of zeolite particles are imprinted from the templates. In addition to hard templates, the use of bifunctional surfactant (soft templates) to prepare ultra-small zeolite nanoparticles and lamellar zeolite membrane is also introduced. With only one structure-directing agent that is less intuitive than hard or soft templates, the preparation of hierarchical lamellar zeolite with 2 nm lamellae, the self-pillard pentasil (SPP) zeolite, is introduced, where the intrinsic growth patterns of the crystal played an important role. Finally, template-free synthesis of zeolite nanoparticles, where zeolite formation is totally driven by the intrinsic growth patterns, is introduced. In addition to the preparation methods, a series of computational methods to determine and study the structures of zeolite nanoparticles are also introduced.