Influence of partial substitution of iron oxide by titanium oxide on the structure and activity of iron-cerium mixed oxide catalyst for selective catalytic reduction of NOx with NH3

The influence of partial substitution of iron oxide by titanium oxide on the catalytic activity of iron-cerium mixed oxide catalyst for the selective catalytic reduction (SCR) of NOx with NH3 has been investigated in this paper. The methods of X-ray diffraction (XRD) spectroscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (NH3/NO-TPD) were used to reveal the effects of titanium substitution on the structure of iron-cerium mixed oxide catalyst. The NH3-SCR activity of Fe0.95Ce0.05Oz is enhanced by partial substitution of iron oxide by titanium oxide, especially under low-temperature condition. This is primarily due to the increase of surface area, pore volume, adsorbed oxygen concentration and reactant adsorption capability. Among a series of Fe0.95−xCe0.05TixOz(x = 0, 0.1, 0.15, 0.2, 0.3 and 0.4) catalysts, Fe0.80Ce0.05Ti0.15Oz(Ti/(Fe + Ce + Ti) = 0.15) shows the highest NH3-SCR activity. On the other hand, thermal-stability of iron-cerium mixed oxide catalyst is also enhanced by titanium oxide substitution. At higher annealing temperature, the crystal content of Fe2O3 in Fe0.95Ce0.05Oz catalyst is depressed by the introduction of titanium oxide. Large surface area and pore volume can be achieved by Fe0.80Ce0.05Ti0.15Oz even calcined at 500 °C for 5 h. This catalyst shows the best NOx conversion in the low-temperature range of 100-300 °C.