A.2 Supported Oxides

A.2.1 Impregnation (Not Used In This Study)

 Impregnation involves the coating of silica with Ti by mixing with a titanium

precursor, such as TiC14 or a Ti-alkoxide. The following equation summarizes the

process:

 Si OH + Ti+4 Si-O-Ti

The homogeneity of the supported oxide is dependent on the concentration of surface

silanols, pretreatment temperature, and molecular size of precursor. A maximum

dispersion of TiO2 was found to be roughly 4.0 Ti atom/nm2. Consistent creation and

determination of the titania phase for catalytic purposes is a major problem with this

method.

A.2.2 Chemical Vapor Deposition (not used in this study)

 The TiO2 is deposited onto the porous silica surface from a gaseous metal

precursor. Consistent coating is difficult to attain from batch to batch and another

problem is the reduction in surface area after coating.