Abstract
Mesoporous zirconia was prepared by the hydrolysis of zirconium tetrapropoxide (ZTP). Crystal structure of zirconia was controlled by using different hydrolysis procedures. A large amount of water and subsequent calcination led to the formation of mesoporous monoclinic zirconia with the pore size of 20 nm, while non-porous tetragonal zirconia was prepared with a small amount of water. Mesoporous tetragonal zirconia with controlled pore size was prepared from ZTP and carboxylic acids with different alkyl-chain length. The average pore size of the tetragonal zirconia increased from 4.8 to 7.5 nm with increasing alkyl-chain length of carboxylic acids. A complex of ZTP and carboxylic acid formed a hexagonal mesophase at the molar ratio of carboxylic acid to ZTP≥1.5. The lattice parameter of the hexagonal mesophase increased with increasing alkyl-chain length of carboxylic acid. The hexagonal mesophase, however, disappeared when the precursor melted over 58°C. The calcined zirconia consisted of the aggregates of crystallites, and the mesopores were located at interparticles. The appropriate coordination state and alkyl-chain length of carboxylic acid are probably effective in preparing mesoporous tetragonal zirconia and controlling the mesopores.
