Significant promoting effect of La doping on the wide temperature NH3-SCR performance of Ce and Cu modified ZSM-5 catalysts

Different La doping Ce-Cu/Z5 catalysts were synthesized via ion-exchange way and then applied in the selective catalytic reduction of NOx via ammonia (NH3-SCR). The 2 wt% La doping Ce-Cu/ZSM-5 (CC-L2/Z5) catalyst exhibited better SCR activity compared to other catalyst in the wide reaction temperature window (200-500 degrees C). The addition of La can also enhance the SCR performance. It is because that the redox cycle Cu2++Ce3+ <-> Cu++Ce4+ facilitates the electron transfer, which further promotes the oxidation of NO into NO2 that could result in the "Fast SCR". The La can also increase the good surface acidic and redox properties and is conducive to the generation of oxygen vacancy. Furthermore, the more content of Ce3+ can generate oxygen vacancy, leading to improving catalytic performance. The CC-L2/Z5 has excellent water and SO2 resistance. At the same time, it has the outstanding stability for repeating six cycles. In-situ DRIFTS results illustrated that L-H mechanism was the main reaction mechanism for CC-L2/Z5 over 250 degrees C.