Effects of Na+ on Cu/SAPO-34 for ammonia selective catalytic reduction

Copper-exchanged chabazite(Cu/CHA) catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na~+ ions on Cu/SAPO-34 for ammonia selective catalytic reduction(NH_3-SCR) are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na~+ ion-exchanges with H+and Cu~(2+)of Cu/SAPO-34. The exchange of H+is easier than that of isolated Cu~(2+). The exchanged Cu~(2+)ions aggregate and form "CuAl_2O_4-like" species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu~(2+)and acid sites is responsible for the activity loss.