Screening of silver and cerium exchanged zeolite catalysts for the lean burn reduction of NOx with propene

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.