Fe-Ti spinel for the selective catalytic reduction of NO with NH3: Mechanism and structure-activity relationship

A series of non-stoichiometric Fe-Ti spine! (Fe3-xTix)(1-delta)O-4 were synthesized using a co-precipitation method and then developed as environmental-friendly and low cost catalysts for the selective catalytic reduction (SCR) of NO with NH3. As Ti was incorporated into gamma-Fe2O3, the SCR reaction over (Fe3-xTix)(1-delta)O-4 through the Langmuir-Hinshelwood mechanism was restrained. Therefore, the SCR activity of (Fe3-xTix)(1-delta)O-4 (x not equal 0) was less than that of gamma-Fe2O3 at 150-250 degrees C. However, the SCR reaction over (Fe3-xTix)(1-delta)O-4 through the Eley-Rideal mechanism was promoted due to the incorporation of Ti. The SCR activity of (Fe3-xTix)(1-delta)O-4(x not equal 0) was mainly related to the oxidative ability of Fe3+ cation on the surface, the concentration of NH3 adsorbed on the surface and the concentration of reducible Fe3+ cation on the surface. Although the oxidative ability of Fe3+ cation on the surface decreased due to the incorporation of Ti into gamma-Fe2O3, the concentration of NH3 adsorbed on the surface and the concentration of reducible Fe3+ cation on the surface both increased. As a result, (Fe2Ti)(0.8)O-4 showed excellent activity, selectivity, and H2O/SO2 durability for the SCR reaction at 300-400 degrees C. (C) 2012 Elsevier B.V. All rights reserved.