Adjusting of the chemical coordination environment of the active constituent to enhance wide-temperature NH₃-SCR activity of Ce, Cu, and La modified TNU-9

A series of Ce, Cu, and La modified TNU-9 zeolite catalysts were synthesized by altering ion exchange sequence and calcinations sequence, and the relationship between the chemical coordination environment of the active ingredients and the catalytic activity in the selective catalytic reduction of NOx using NH3 as reductant (NH3-SCR) was revealed. The results showed that within the temperature window (150-450 degrees C), the catalyst (Cs-CL/T9) prepared by exchange copper ion, followed by roasting, then followed by simultaneous exchange of cerium and lanthanum ion had excellent wide-temperature NH3-SCR activity. Because after roasting, Cu2+ in the framework of TNU-9 could migrate under the high temperature to result in the stable structure, thereby reducing steric hindrance ions and exchanging more cerium and lanthanum ions. The increase of cerium ion content can produce more oxygen vacancies, so that NO is oxidized to NO2. Furthermore, electron paramagnetic resonance (EPR) results exhibits that there are Cu2+ active site in Cs-CL/T9, leading to the excellent NH3-SCR performance. In addition, altering ion exchange sequence and calcinations sequence increase the number of acidic sites and the redox ability etc.