The effect of the vanadium component on the life of the WO3-TiO2 catalyst used for the reduction of NOx with NH3.

The 5000-h life test of the WO3–TiO2 catalyst for the reduction of NOx with NH3 has been investigated in real flue gases containing vanadium and SOx on a pilot plant. When the present catalyst was used in a residual-oil-fired-boiler flue gas, steady activities over 90% of NOx reduction were achieved for 5000 h at 400 °C (space velocity: 2700 h−1). On the other hand, when the catalysts were taken out of the reactors at certain intervals and studied by means of a laboratory reactor, they were much more active than fresh catalyst at lower temperatures (250–350 °C). Also, the SO2 oxidation efficiency increased with the reaction time. This activation was considered to be due to the vanadium component in the flue gas.