The development of supported vanadia catalysts for the combined catalytic removal of the oxides of nitrogen and of chlorinated hydrocarbons from flue gases

Supported vanadia catalysts are commercially used to remove the oxides of nitrogen contained in oxygen-containing flue gases by selective catalytic reduction (SCR) using ammonia as reductant. This paper examines the possibility of using the same catalysts for the complete oxidation of chlorinated hydrocarbons (ethyl chloride or chlorobenzene) in the presence of NO and ammonia. It is shown that vanadia supported on an alumina-modified zirconia is capable of giving 100% conversion of the chlorinated molecules while giving also 100% conversion of the NO over a relatively wide range of temperature (593-683 K). This material also shows a resistance to poisoning by HCl but it is slowly poisoned by SO₂ if present. The addition of tungsten oxide to the formulation has no significant effect on the catalytic behaviour towards NO and ethyl chloride but it improves the resistance to SO₂.