Aerogels of titania, silica, and vanadia

Aerogels of titania, titania-silica, and titania-vanadia were prepared with titanium butoxide, silicon ethoxide, and vanadium triisopropoxide as precursors. The titania and titania-silica aerogels were then used as supports for vanadia, introduced by the incipient wetness impregnation of vanadium triisopropoxide and the subsequent calcination at 773 K. 

With the prehydrolysis of TEOS, we expect a homogeneous distribution of the two oxides in our titania-silica support Coupled with the fact that silica is the major component, this sample should behave as the "silica-like" sample prepared by Handy et al. (8) with a two-stage hydrolysis procedure. In other words, there are no crystalline titania domains in the sample, consistent with the X-ray diffraction and Raman results. This titania-silica mixed oxide aerogel is therefore less effective in stabilizing surface vanadia species (see Figure 3) and less active in SCR (see Table II) than pure titania aerogel as observed. 

Two kinds of titania aerogels have been discussed pure titania and mixed- or composite oxides. The better photocatalytic activity of titania aerogel was reported already in early 1970s [3]. In order to improve its catalytic activity, addition of other transition metal oxides to titania aerogels, such as vanadia, was discussed [11,12]. Also, composite aerogels with highly adsorbable oxides, silica, and alumina were reported [13-18]. 

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