High Temperature SCR Over Cu-SSZ-13 and Cu-SSZ-13+Fe-SSZ-13: Activity of Cu2+ and [CuOH]1+ Sites and the Apparent Promoting Effect of Adding Fe into Cu-SSZ-13 Catalyst

Cu-SSZ-13 catalysts were synthesized with Si: Al = 4.5 and 25, to obtain materials with isolated Cu2+ and [CuOH](1+) sites, respectively. The catalysts were tested for the selective catalytic reduction of NOx (SCR), NO oxidation and NH3 oxidation. Cu2+ sites presented the highest NO rates and lowest NH3 rates, as the temperature was increased from 300 degrees C to 650 degrees C, during SCR and NH3 oxidation, respectively. None of the Cu-SSZ-13 catalysts presented activity for NO oxidation, consistent with the absence of copper oxide clusters. In addition, catalysts composed by mechanical mixtures of Cu-SSZ-13 + Fe-SSZ-13 with Si: Al = 4.5 and 25 were tested for SCR, NO oxidation and NH3 oxidation, to study the effect of the presence of iron together with Cu-SSZ-13 for improving its SCR working temperature range. Higher reaction rates for NO oxidation and NH3 oxidation over Cu-SSZ-13 + Fe-SSZ-13 showed a more relevancy of side reactions that makes a combined effect of Fe-SSZ-13 and Cu-SSZ-13 not a real improvement in high temperature SCR.