Effect of Zr Addition on the Low-Temperature SCR Activity and SO2 Tolerance of Fe–Mn/Ti Catalysts

Zr is added to the Fe–Mn/Ti catalyst to increase NO conversion and improve SO 2 tolerance. It is found that 0.03 is the optimal ratio for Zr/(Ti + Zr). With this ratio, the NO conversion below 150 °C increases, and the SO 2 poisoning is alleviated, while the further increase of Zr does not have a positive effect on NO conversion and SO 2 tolerance. With Zr additive, more manganese oxides are reduced in the form of MnO 2 and Mn 2 O 3 at lower temperature in H 2 -TPR, and the total amount of H 2 consumption rises, indicating better redox properties. It leads to the increase of NO complexes on the catalysts. Despite the small decrease of NH 3 adsorption, the reaction via the L–H way is promoted and NO conversion increases. Furthermore, more nitrates and NO 2 are formed in the reaction with SO 2 on Fe–Mn/Ti–Zr(0.03) compared to Fe–Mn/Ti, so the L–H reaction way is less inhibited by SO 2 with Zr additive, and the SO 2 tolerance of this catalyst is also improved.