Formation of the Porous Structure of Titanium Dioxide Prepared by a Sol-Gel Method
Preparation of Catalysts VII : 7th International Symposium on Scientific Bases for the Preparation of Heterogeneous Catalysts
01-04 Sep 1998
||Preparation of Catalysts VII : Proceedings of the 7th International Symposium on Scientific Bases for the Preparation of Heterogeneous Catalysts, 1-4 September 1998, Louvain-la-Neuve, Belgium
987 c. ISBN 978-0-444-50031-1.
Studies in Surface Science and Catalysis
Boreskov Institute of Catalysis, pr. Lavrentieva 5
Effect of the precipitate conditions and ageing of titanium dioxide hydrogel on the formation of xerogel porous structure was investigated. Results obtained demonstrated that hydrogel precipitation with ammonia solution in a sol–gel method of hydrogel TiO2 synthesis, independently from pH, provides limiting dispersion of the primary oxide particles (5 nm). Porosity and the character of the porous volume distribution are determined by ions adsorption at the stage of hydrogel synthesis. Xerogels, received close to IEP, have the big porosity (0.78-0.79) and heterogeneous porous structure. A deviation of pH from IEP results in the formation of similarly fineporous xerogel. Hydrogel precipitated by NaOH solution leads to the formation of xerogels with a greater porosity (0.84-0.85) and smaller surface value. During ageing of the TiO2 hydrogel, firstly, the appearance of anatase results to disordering the skeleton of amorphous titania, decreasing the porosity and raising the xerogel strength. Long ageing is accompanied by aggregation of crystalline particles, resulting already to decrease of mechanical strength.