A comparative study on the activity of metal exchanged MCM22 zeolite in the selective catalytic reduction of NOx

A series of MCM22 zeolites exchanged with copper and cobalt are studied for the selective catalytic reduction (SCR) of NO with C3H8 and the behavior compared with that of Cu and Go-beta and ZSM5 zeolites. The results show that Co and Gu-MCM22 samples are stable SCR catalysts. These zeolites give the maximum activity at 450 degrees C, Their behavior towards oxygen content in the reactant phase and exchange level of the metal in the catalyst, is qualitatively similar to that of metal exchanged beta and ZSMS zeolite, but the yields obtained with this zeolite are lower in any case. The infrared studies of adsorbed NO show, contrary to what is occurring in ZSMS in which only Cu+ sites are observed at low NO partial pressure, that in this condition, Cu+ and Cu2+ species are formed on MCM22. The results indicate that in MCM22, the copper located in the 10 member ring (MR) circular channels behaves similarly to that present in ZSMS, while the Cu present in the 12 MR cavities has a strong tendency to agglomerate forming non active CuO clusters.