Packaging of sol-gel-made porous nanostructured titania particles by spray drying

Porous titania granules (1-20 mum) were made by spray drying titania solutions with and without peptization. An unpeptized titania slurry was prepared by hydrolyzing titanium tetraisopropoxide, while a peptized sol was prepared by adding nitric acid to the slurry. The characteristics of the granules depended on the feed solution properties. In particular, granules from the unpeptized slurry showed a bimodal pore size distribution (PSD), with a rough surface attributed to hard aggregates; granules from the peptized Sol showed a monomodal PSD, with a smooth surface of well-packed nanoparticles. The effect of dopants (alumina and zirconia) also was investigated. Doping slowed the crystallite growth of the titania granules, as well as the anatase-to-rutile phase transformation. All of the peptized granules exhibited a monomodal PSD of intraparticle pores, from 2 to 15 nm. However, the PSD of the pure titania granules collapsed at 600 degreesC, mainly by phase transformation.