MORPHOLOGY OF TITANIA COATINGS ON SILICA-GEL

Control of the hydrolysis and condensation of soluble precursors of ti tanium is shown to yield oxide coatings of well-defined morphology. A ''smooth'' coating, consisting of patches of titania on silica, causes only a small increase in the surface area, from 130 m(2)/g for the un coated silica gel to 154 m(2)/g. On the other hand, the ''rough'' coat ing, which consists of 3 nm diameter titania particles dispersed over the silica surface, results in an increase in the BET surface area to 350 m(2)/g. The specific titania surface area was determined via isopr opanol dehydration activity and was found to be comparable to the BET surface area indicating that the titania phase is responsible for the increase in surface area. Small angle X-ray scattering (SAXS) and tran smission electron microscopy (TEM) provide definitive evidence for the coating morphology while X-ray photoelectron spectroscopy (XPS) was u sed to determine the dispersion of the titania. The supported titania maintains its surface area upon calcination at temperatures up to 873 K while unsupported titania looses much of its surface area. Also demo nstrated in this work is a novel preparation method using titanium bis -ammonium lactate dihydroxide (TALH), a water soluble precursor.