IR Investigation of Selective Reduction of NO by Ethene on Cu-ZSM-5

Article abstract of DOI:10.1246/bcsj.68.1905

Adsorbed species during the reaction of selective catalytic reduction of NOx by hydrocarbons (HC-SCR) on Cu ion-exchanged ZSM-5 (Cu-ZSM-5) were investigated by in situ FT-IR using isotopes as well as gas phase analysis.No oxygen-containing species was observed by IR and no reaction proceeded in the presence of gaseous O2 and C2H4 below 473 K, at which HC-SCR occurs.However, an extra NOx species (tentatively assigned to organic nitrite or nitrate species), other than inorganic NOx species derived from O2 and NO, appeared very rapidly in IR at 1670 cm^-1 at room temperature, in the presence of adsorbed NO2 species, gaseous C2H4 and NO.Afterwards, a carbonyl species (1677 cm^-1) was formed gradually at room temperature.When the extra NOx species was observed, N2 and N2O evolved even at room temperature, therefore, the extra NOx species is considered to be related to HC-SCR.In the O2+C2H4+NO reaction at 473 K, no nitrogen-containing species, except for quite a small amount of nitrile (2168 cm^-1), was observed in IR.At 473 K, N2, and CO evolved very rapidly with a steep increase in the IR intensity of carboxylate (1574 and 1375 cm^-1), while CO2 and carbonyl species increased more slowly.