Effect of Supports and Additions (Metal Oxides) on Iron (III) Sulfate Catalysts for the Reduction of Nitrogen Oxide with Ammonia -Selection of Coprecipitated Fe2(SO4)3-α-Fe2O2-TiO2-MoO3(WO3) Catalysts-

Abstract

For the purpose to obtain catalysts with high activity and durability for the reduction of nitrogen oxide with NH3, various catalysts containing oxides of Fe, Cr, Cu, Al, Ti, and Mg were prepared from the precipitates formed by the reaction of sulfates with NH3 aq.The catalytic activity and the effect of SO r were tested by using a flow reactor (I. D.: 12.0 mm) under atmospheric pressure and at 250-500°C.The average diameter of the granular catalysts was 1.0 mm. Inlet gas concentration was 500 ppm NO-667 ppm NH3-0 or 1000 ppm SO2-5% O2-10% 1120-N2 balanced and the total gas flow rate was 1000 Ncm'imin (space velocity: 1.1 x 105 hr-) toward O.55 cm (bulk volume) of the catalysts.On the basis of these results, the catalyst, Fe, (SO4)3-ce-Fe3O2-iO3(Fe2O2-TiO3 system), was found to be highly active both in the presence and in the absence of SOS. Furthermore, it was proved that the addition of MoO3 or WO, to this iron catalyst increases the stability against SO r and selectivity for the reduction of NO.On the basis of the study of the reduction of NO with NH, or the oxidation of NH3 with O2- over the catalysts pretreated with pure H2 or 1000 ppm NH3-N2 mixture, it was confirmed that SO4 in the catalysts promotes the stable and selective reduction of NO. Also, only TiO2 of anatase type is active and the addition of MoO8 or WO, to this TiO2 was found to be very effective for the reduction of NO.