Comparison of activities in selective catalytic reduction of NOx by C3H8 over Co/MFI, Fe/MFI, and H/MFI zeolite catalysts

Abstract

The Co/MFI(SiO2/Al2O3 = 30) were prepared by a precipitation method with NaOCl in alkali solutions exhibited high activities to N2 at 250°C for the selective catalytic reduction (SCR) of NOx. These catalysts showed two UV–vis bands at 700 and 400nm, indicating the presence of octahedral Co(III) as well as tetrahedral Co(II). The high SCR activity over such Co(III, II)/MFI(30) seems to come from Co(III)O moieties. The Co(II)MFI(30) catalysts prepared from Co(II)Cl2 exhibited low SCR activities due to the presence of tetrahedral Co(II) ions in MFI. Less CO formation occurred over Co/MFI catalysts. The Fe/MFI(30) catalyst exhibited high activity due to the presence of some FeO species in MFI but more amount of CO were produced during SCR. H/MFI(30) catalyst exhibited a good SCR activity. However, more amount of carbonaceous deposits were produced on it. The correlation between acid concentration and SCR activity was discussed over H/MFIs.