Iron, lanthanum and manganese oxides loaded on γ-Al 2O 3 for selective catalytic reduction of NO with NH 3 at low temperature

Abstract

A series of Mn/Al 2O 3, La-Mn/Al 2O 3 and Fe-La-Mn/Al 2O 3 catalysts were prepared by an impregnation method and investigated for selective catalytic reduction of NO with NH 3 at low temperature. The experimental results revealed that NO conversion over La-Mn/Al 2O 3 was obviously improved after La doping. Addition of Fe increased both NO conversion and the resistance to H 2O and SO 2. The catalyst Fe 0.04La 0.03Mn 0.06/Al 2O 3 with a load mass of MnO 2=6%, La 2O 3=3% and Fe 2O 3=4% exhibited relatively high catalytic activity and yielded 98% NO conversion at 260° with a space velocity of 15, 000 h −1. Meanwhile, the catalytic activity was slightly decreased in the presence of H 2O and SO 2. Moreover, the catalysts were characterized by N 2 adsorption measurement, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that the doping of La enhanced the dispersion and oxidation states of Mn on the surface of Al 2O 3. On the surface of the Fe 0.04La 0.03Mn 0.06/Al 2O 3 catalyst, La was highly dispersed and a mixed oxidation state of Mn existed, while iron ions were only in the Fe 3+ state. The mechanism of selective catalytic reduction over these catalysts is also discussed. In this experiment, metal oxides loaded on the support were catalytic centres which served as electron transfer during NO reduction. The electron transfer between Mn 3+ and Fe 3+ might also exist and the mixture oxidation states of Mn on the surface of the Fe 0.04La 0.03Mn 0.06/Al 2O 3 catalyst contributed to the SCR activity.