(202c) Thermal and Crystalline Stability of Silica-Tungsta/Titania Particles Made by Flame Spray Pyrolysis

The effect of doping with silica flame-made WO₃/TiO₂ powders (anatase, 100 m²/g) on their specific surface area, crystallinity and catalytic activity was investigated. The silica content was 0-5 wt% while tungsta was constant at 10 wt%. The structural and chemical properties of these nanosized powders were analyzed by nitrogen adsorption (BET), X-ray diffraction (XRD), temperature programmed reduction (TPR), transmission electron microscopy (TEM) and Raman spectroscopy. The thermal and crystal stability was improved by adding up to 5 wt% silica. After calcination for 20 hours at 700^°C in air, the thermally most stable powder conserved a SSA of 90 m²/g and 96 wt% of the anatase. Tungsta form thin polymeric layers (~1 nm) on the surface of the titania support.