The catalytic reduction of NOx in the real flue gas from a sintering furnace, with NH3 was studied by using V2O5 and Fe2O3 catalysts supported on δ-Al2O3 (Fig.1). Studies were focused on the dust components in the flue gas which would be harmful to the catalyst life. The dusts consist of such alkaline and alkaline earth metals as K, Na, and Ca (Table 1, 2). Fe and Si were also identified in the dust. The dust components gave different effects on the catalysts. Si and Ca permeated into the catalysts to diminish their micro pore structures (Fig. 8, 9). while K selectively reacted with iron ions in Fe2O3 catalyst and in the dusts. It was observed that the amount of K in the catalysts lowered the catalytic activities (Fig. 10, 11). X-ray diffraction spectra showed that K in the catalysts exists in the form of K2Fe(SO4)2. By means of ion microanalyzer, K was found to permeate into the surface of V2O5 catalyst (Fig. 5), while, in the case of Fe2O3 catalyst, it was concentrated on its surface (Fig. 6), and then migrated in the bulk of the catalyst deeper than 150 μ from its surface (Fig. 7). This fact resulted in more deactivation of Fe2O3 catalyst than that of V2O5 catalyst. It was also clarified in this study that S02 in the flue gas less affected the catalytic activities than the dust components. The poisoning effect of the dust components was also elucidated separately. © 1978, The Chemical Society of Japan. All rights reserved.
