Titania coatings on silica

Titania is an important catalytic material both as a support and as a catalyst for photocatalytic applications. It however suffers from poor thermal stability of its surface area, extrudability and mechanical strength. This dissertation is dedicated towards achieving titania coatings on silica with high thermal stability and its use in potential applications. In this dissertation, I first proved that uniform titania coatings on model silica spheres could be achieved by using both a non-aqueous precursor (Ti-(O-n-{dollar}rm Csb4Hsb9)sb4{dollar}: Titanium n-butoxide (TBOT)) and a water-soluble precursor {dollar}rm ((lbrack CHsb3 CH (O) COsb2 NHsb4rbrack sb2 Ti (OH)sb2):{dollar} Titanium bis-amino lactato dihydroxy (TALH)). Then, as an extension of this work for practical utilization, coatings were achieved on a set of precipitated silicas obtained from Norton Corporation that exhibited porosity. It was found that porosity did not affect the formation of coatings, even inside the pores, in the range of pore dimensions (100-180A) studied. The nature and morphology of the titania coatings was determined by using complementary techniques of nitrogen adsorption, SAXS, TEM, BET, XRF, SEM and isopropanol dehydration. The location of titania (either inside the pores or outside) was determined by analysis of nitrogen adsorption data. In addition, thermal stability of surface area was attained by the supported titania (up to 18 wt% for supported titania prepared from TBOT and up to 46 wt% for supported titania from TALH) up to a temperature of 823 K. In addition, {dollar}rm MoSsb2{dollar}/supported on titania coatings performed significantly better than MoS, supported on bulk silica and titania on a per gram basis for hydrodesulfurization of dibenzothiophene. Thus, in this dissertation, supported titania was synthesized by two different routes (including an aqueous route) and it was shown to have high thermal stability and also potential utility as a superior support for a commercially relevant hydrodesulfurization reaction. The coating methods developed in this dissertation can be applied to other systems where it is desirable to alter the surface chemistry of a support, or to prevent an adverse support interaction, for example {dollar}rm Fe/SiOsb2{dollar} for Fischer-Tropsch synthesis.