Selective catalytic reduction of NO over CuO-CeO₂-MnO_x/γ-Al₂O₃ catalysts

CuO-CeO₂-MnO_x/γ-Al₂O₃ granular catalysts were prepared by sol-gel method. Performance of the CuO-CeO₂-MnO_x/γ-Al₂O₃ catalyst for the selective catalytic reduction (SCR) was explored in a fixed bed adsorption system. The optimum temperature ranges for SCR of NO over the CuO-CeO₂-MnO_x/γ-Al₂O₃ catalysts were 250℃～400℃. The maximum efficiency maintained near to 99% at 350℃. With higher loading of Ce, the SCR activity increased at low temperature range (100℃~300℃). Preliminary tests were carried out to study the behavior of NH3 and NO over catalyst in the presence of oxygen. The NH₃ oxidation experiments showed that both NO and N₂O were produced gradually with temperature rising. The NO oxidation experiments revealed that NO was oxidized to NO₂ over the catalyst. The NH₃ and NO desorption experiments showed that NH₃ and NO could be adsorbed on CuO-CeO₂-MnO_x/γ-Al₂O₃ granular catalysts. The less adsorption capacity and the over-oxidation of NH₃ were the main cause of lower activity at high temperature. The transient behavior of NH₃ and NO was also studied. It was found that the SCR reaction was zero order to NH₃ and first order to NO.