摘要：

Various silver and cerium exchanged zeolites were screened on their activity in the reduction of NOx with propene under lean burn conditions. Furthermore, the performance of co-exchanged Ag-Ce-H-BEA (beta) and Ag-Ce-H-FER (ferrierite) for this reaction was studied. The catalysts were tested in a simulated exhaust gas mixture, composed of 400 ppmv of NOx, 400 ppmv of propene, 10 vol.% of oxygen, 10 vol.% of water and balance nitrogen, at a space velocity of 47 700 h−1. The NOx conversion of the silver exchanged zeolites was ranked as Ag-Na-BEA>Ag-H-FER, Ag-H-BEA, Ag-K-FER>Ag-H-ZSM-5. Ag-Na-BEA showed 42% NOx conversion at 300 °C. The NOx conversion of the cerium exchanged zeolites decreased in the order of Ce-H-FER>Ce-H-ZSM-5>Ce-H-BEA. Ce(75)-H-FER showed 90% NOx reduction at 350 °C, which is high, also in comparison to Ag-H-FER, Pt-H-FER, Cu-H-FER and Co-H-FER. The NOx reduction over Ce-H-FER was above 40% in the temperature range of 300–500 °C. No synergetic effect on the NOx reduction activity with propene was observed for the co-exchange of silver and cerium in H-ferrierite.

展开