Removal of NO by Reversible Adsorption on Fe−Mn Based Transition Metal Oxides

A series of Fe−Mn-based transition metal oxides were prepared and used for NO adsorption at 25 °C in the presence of O2. The sorbents were also characterized by BET surface area, TPD, XRD, and FTIR spectroscopy. Both TGA and chemiluminescent NO/NOx analyzer experiments showed that the mixed oxides were efficient and reversible sorbents for NO removal. The NOx capacity decreased in the order of Fe−Mn−Ti, Fe−Mn−Zr > Fe−Mn−Ce, Fe−Mn−Ni > Fe−Mn−Co > Fe−Mn−Cu, Fe−Mn. The maximum NOx capacity reached 42−45 mg/g of sorbent for the Fe−Mn−Ti and Fe−Mn−Zr oxides. SO2 and CO2 decreased the NOx adsorption amount only slightly. H2O decreased the NOx adsorption significantly, but the inhibition was reversible. TPD profiles indicated that NOx species could desorb at temperatures below 400 °C. The high efficiency for NO removal on these oxides was related to their high activities in NO oxidation to NO2 at 25 °C. FTIR spectra showed that the nitrate was the final species for NO adsorption. NO2 and nitrite were the intermediates during nitrate formation on the oxides.