Thermal Stability and Catalytic Activity of Flame-madeSilica-Vanadia-Tungsten oxide-Titania

摘要

Vanadia (0.9 or 2 wt%) and silica (0 – 5 wt%) doping of flame-made tungsten oxide/ titania nanostructure powders (anatase, 100 m2/g, 10 wt% WO3) is investigated. Theeffect of dopants on structural and chemical properties of these nanosized powders wereanalyzed by nitrogen adsorption, X-ray diffraction (XRD), temperature programmedreduction (TPR) and Raman spectroscopy. After calcination for 20 hours at 700°C in air,the thermally most stable composite powder conserved its specific surface area (SSA) to90 m2/g and its anatase content to 96 wt%. Tungsten oxide and vanadia form thinpolymeric layers (~1 nm) on the surface of the titania support. Catalytic properties arestrongly correlated to thermal stability of the catalyst. Adding silica improves the thermaland crystal stability of the catalysts even at higher reactor temperatures and as a resultNO conversion by selective catalytic reduction (SCR) with NH3 and turnover frequencywere increased.