Selective catalytic reduction of NO by C₃H₈ over Ce-Fe/Al₂O₃/cordierite catalysts

A series of monolithic cordierite-based Ce-Fe/Al₂O₃ catalysts were prepared by sol-gel and impregnation method. The selective catalytic reduction of NO with C₃H₈ over the catalysts were experimentally studied. Results indicated that when the addition of cerium increased from 1% to 5%, the C₃H₈-SCR of Ce-Fe/Al₂O₃/cordierite increased at first then decreased and 3.5Ce-Fe/Al₂O₃/cordierite showed the highest C₃H₈-SCR activity with 96.5% NO reduction in the presence of oxygen at 600℃. Cerium was able to improve the resistance to SO₂ in the flue gas for the Fe/Al₂O₃/cordierite catalysts. When 0.02% SO₂ was fed into the flue gas during the test, the NO reduction by 3.5Ce-Fe/Al₂O₃/cordierite with C₃H₈ was always kept at about 93%, while the NO reduction by the catalyst without Ce, i.e., Fe/Al₂O₃/cordierite, decreased from 88% to 80%. The catalysts were characterized using XRD, N₂ adsorption-desorption, SEM, H₂-TPR and Py-FTIR spectra of adsorbed pyridine. Results showed that the addition of cerium to iron oxide could form the solid solution, which could increase the Lewis acid concentration and redox property of the catalyst, thus improving the performance of catalytic reduction of NO with C₃H₈. However, the introduction of too much cerium would reduce the crystallinity of iron oxide nanorods, then inhibited the formation of the NO₂/NO₃^- species in the C₃H₈-SCR reaction, resulting in a decrease in the efficiency of NO reduction.