TiO2 was deposited on SiO2 (5-15%) by impregnation with (i-PrO)(4)Ti and calcination at 500 degrees C or 700 degrees C to prep. oxidn. catalyst. The catalysts were studied for sp. surface (312-380 m(2)/g), acidity, basicity and catalytic activity in photochem. NH3-to-N-2 oxidn. under UV and visible light irradn. The irradn. resulted in a considerable enhancement of the NH3 conversion at 300-400 degrees C.