Microporosity and acidity properties of alumina pillared titanates

A titanate with lepidocrocite-like structure has been intercalated by hexyl ammonium (HA) and tetrabuthylammonium (TBA) organic cations, which were fur ther exchanged with aluminum polyoxocations. The pillared structure of thes e materials was found to be stable up to 500 degrees C and exhibited a basa l spacing of 1.4 nn. Nitrogen adsorption isotherms were measured to determi ne the surface areas and pore structure of these pillared titanates, and th e effect of intercalation temperature and heat treatment on these surface c haracteristics is discussed. The micropore volume values were related to th e amount of alumina and to the heat-treatment temperature. Most of the pill ared titanates prepared from HA-Ti showed a sharp distribution of micropore s with the average diameter of 2 nm, whereas the comparable materials obtai ned from TBA-Ti showed a broad distribution of pore diameter centered 4 nm in addition to micropores. Infrared spectroscopy monitoring the pyridine ad sorption showed the presence of Lewis acid sites, and evolution of surface Bronsted acid sites upon incorporation of the alumina pillars. There is a g ood correlation between the amount of alumina and the acidity in terms of p roton concentration (Bronsted) as determined by adsorption/desorption of cy clohexylamine.