화학공학소재연구정보센터
Langmuir, Vol.15, No.4, 1090-1095, 1999
Microporosity and acidity properties of alumina pillared titanates
A titanate with lepidocrocite-like structure has been intercalated by hexylammonium (HA) and tetrabuthylammonium (TBA) organic cations, which were further exchanged with aluminum polyoxocations. The pillared structure of these materials was found to be stable up to 500 degrees C and exhibited a basal spacing of 1.4 nn. Nitrogen adsorption isotherms were measured to determine the surface areas and pore structure of these pillared titanates, and the effect of intercalation temperature and heat treatment on these surface characteristics is discussed. The micropore volume values were related to the amount of alumina and to the heat-treatment temperature. Most of the pillared titanates prepared from HA-Ti showed a sharp distribution of micropores with the average diameter of 2 nm, whereas the comparable materials obtained from TBA-Ti showed a broad distribution of pore diameter centered 4 nm in addition to micropores. Infrared spectroscopy monitoring the pyridine adsorption showed the presence of Lewis acid sites, and evolution of surface Bronsted acid sites upon incorporation of the alumina pillars. There is a good correlation between the amount of alumina and the acidity in terms of proton concentration (Bronsted) as determined by adsorption/desorption of cyclohexylamine.