Experimental Study on the Deactivating Effect of KNO 3 , KCl, and K 2 SO 4 on Nanosized Ceria/Titania SCR Catalyst

Nanosized Ce/TiO 2 is effective in selective catalytic reduction of NO with NH 3 . The NO conversion of Ce/TiO 2 is 93% at 370°C. However, addition of potassium using KNO 3 , KCl, or K 2 SO 4 as precursors effectively deactivates Ce/TiO 2 . NO conversion at 370°C is reduced to 45%, 24%, and 16% after addition of KNO 3 , KCl, and K 2 SO 4 , respectively, with a controlled K/Ce molar ration at 0.25. The deactivation may be attributed to the changes in the structural and chemical state of ceria and the degradation of surface acidity. The transformation of amorphous ceria into ceria crystals after potassium addition, together with the decrease of surface defects, is also determined. Oxygen diffusion in the process of ceria reduction is slow, and the redox cycle is slowed down. Moreover, the surface acid sites are markedly destroyed, leading to the reduced capacity of ammonia adsorption. These results may provide useful information for the application and life management of CeO 2 /TiO 2 in potassium‐rich environments such as biofuel‐fired boilers.