SELECTIVE CATALYTIC REDUCTION OF NO BY NH3 OVER AEROGELS OF TITANIA, SILICA, AND VANADIA

Abstract

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. The structures of vanadia and titania in these samples were characterized by X-ray diffraction and Raman spectroscopy, and their catalytic properties by the selective catalytic reduction (SCR) of NO with NH3. With H2O and SO2 in the feed stream, the SCR activity decreased with increasing vanadia loading. Samples of high activity all contained anatase TiO2, but an active vanadia species only needed to be in close proximity and interacting with, and not necessarily deposited on the surface of crystalline titania. Co-gelling was thus an effective way to prepare an active sample in a single step, as demonstrated by the SCR data of the titania-vanadia aerogel. The addition of niobia, up to 10 weight %, did not appreciably change the surface area, structure, or SCR activity of the titania aerogel supported vanadia.