SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY PROPANE OVER VANADIA-TITANIA AEROGELS

An investigation has been carried out of the effect of vanadia loading on the activity and selectivity of V2O5/TiO2 aerogel catalysts, prepa red by a two-step procedure, for the reduction of NO by propane. The s tructure of catalysts have been characterized by laser Raman spectrosc opy and XRD measurements. At vanadia loading levels below ca. 4.4 wt%, the vanadia is present in the form of coordinated polymeric species, whereas crystallites of V2O5 are formed at higher vanadia contents. At this critical level of 4.4 wt% V2O5, the kinetic measurements showed also a maximum in the activity per mass of catalyst which very likely indicated that the coordinated polymeric surface species are more acti ve than crystalline V2O5. The selectivity towards the formation of din itrogen decreased as the loading increased, presumably because of the formation of larger polymeric species and V2O5 crystallites, below and above the critical loading level, respectively. For the reduction of NO by propane, titania supported vanadia aerogel catalysts are signifi cantly more active, per mass of catalyst, and more selective towards N -2 formation than conventional V2O5/TiO2 and V2O5/Al2O3 aerogel cataly sts, at vanadia loading levels below ca. 11 wt%.