Effect of water vapour on the selectivity in the reduction of nitric oxide with ammonia over vanadia supported on silica-titania

The effect of the presence of water vapor on the reduction of nitric oxide with ammonia was investigated using vanadia on SiO2-TiO2 as a catalyst. The selectivity towards nitrogen is greatly increased upon addition of water. Repeated use at temperatures of 825 K causes sintering of the catalyst and loss of activity as well as selectivity towards nitrogen. The formation of nitrous oxide is preferentially taking place on large crystals of presumably reduced vanadia. Removal of these crystals results in a more selective catalyst