Effect of chelating agent 1,5-diaminopentane on the microstructures of sol-gel derived zirconia membranes

Zirconia is more chemically stable than silica and gamma-alumina, which are commonly used in the preparation of inorganic membranes. However, the hydrolysis of zirconia alkoxides, typical zirconia precursors, proceeds rapidly, leading to difficulties in preparing clear sols. Thus, an attempt was made to reduce the hydrolysis rate of zirconium propoxide by a ligand-exchange reaction with 1,5-diaminopentane (DAP). The availability of water was also reduced by the dropwise addition of glacial acetic acid, which produced an ester by reaction with the solvent, 1-propanol. The addition of DAP was effective in preparing zirconia with a narrow pore-size distribution and a high mesopore volume. DAP also decreased the phase transformation temperature of zirconia and had almost no effect on the micropore structures. The gas permeation properties of the prepared zirconia membranes were fundamentally controlled by the Knudsen diffusion mechanism.