New nano-structured sorbent materials for gas separation, purification and storage.

Abstract

Nanoporous sorbent materials have a large portion of their surface area in the nanopores, which is suited for adsorption of various molecules. This property provides scope for the synthesis and tailoring of new nano-structured materials towards specific gas separation, purification and storage needs. This dissertation discusses the synthesis, characterization and evaluation of several nano-structured sorbent materials for use in specific gas separation, purification and storage applications. These materials include carbon molecular sieves, natural/modified clinoptilolites, partially cerium exchanged zeolites, silver salts dispersed on silica gel, pi-complexation sorbents and activated carbon/carbon fiber. Two types of carbon molecular sieves were examined for CH₄/CO₂ separation and temperature was found to play a key role in kinetic PSA separations. Clinoptilolites were tailored for methane upgrading. Purified, mixed Mg/Na and Na/Ce clinoptilolites were shown to be competent with a commercial CH₄/N₂ separation process. Mixed Na-Ce-X zeolites were found to exhibit crossover of N₂ and O₂ isotherms leading to oxygen selectivity at very low pressures. Stable oxygen selective sorbents were developed with silver and cerium salts. AgBr dispersed on SiO₂ showed good oxygen selectivity for N₂ production by PSA. pi-complexation sorbents were found to be severely deactivated by H₂ exposure and the rejuvenation of pi-complexation capability was obtained by mild oxidation and the optimum conditions were identified. Pt dispersed on activated carbon fiber was found to influence H₂ storage by spillover.