A study on the selective catalytic reduction of NO(x) by ammonia on sulphated iron-based catalysts

A series of sulphated iron-based catalysts was prepared via an impregnation method by changing the loading content of Fe(3+) and SO(4)(2−) on ZrO(2), and their performance in the selective catalytic reduction (SCR) of NO(x) by ammonia was investigated. The NO(x) conversion exhibited large differences among the sulphated iron-based catalysts. To explore the synergistic mechanism of iron and sulphates, XRD, BET, H(2)-TPR, XPS, TPD and in situ DRIFTS were used to characterize the catalysts, and it was found that among all the catalysts, the NO(x) conversion by Fe(2)SZr was greater than 90% at 350–450 °C. The results indicated that the interaction between Fe(3+) and SO(4)(2−) can have an effect on the redox ability, acid sites, and adsorption of NO(x) and NH(3). With an increase in the content of Fe(3+), the redox activity of the catalyst and the adsorption of ammonia improved at medium and low temperatures. However, at higher temperatures, an increase in Fe(3+) led to a decrease in the conversion of NO(x) due to the enhanced oxidation of NH(3). At medium and low temperatures, an increase in the content of SO(4)(2−) decreased the concentration of Fe(3+) on the surface of the catalyst and inhibited the adsorption of NO(x) and NH(3). The addition of SO(4)(2−) reduced the redox activity of the catalyst and inhibited the oxidation reaction of NH(3), which follows the Eley–Rideal mechanism at high temperatures, further enhancing the SCR activity of the Fe(x)S(y)Zr catalyst.