Improved stability of Co-Ferrierite catalyst by Mn in dry–wet cycles of lean CH4-SCR of NOx

Ion-exchanged Co, Mn and Co,Mn-FER zeolite was tested as catalyst for the selective reduction of NOx with CH4 in the presence of O2 under dry and wet (1 vol% H2O) cycles. Under hydrothermal conditions Co-FER undergoes a progressive loss of activity, while Co,Mn-FER catalyst shows an increased water resistance. UV-VIS spectra of monometallic and bimetallic catalysts collected before and after dry–wet catalytic cycles show a change of Co species distribution within the zeolite upon heating and exposure to water. However, the presence of Mn prevents the decrease in the population of the most active Co2+ site in the presence of water and stabilises the catalytic activity, as evidenced in 80 h time on stream run.