Promoting effect of calcium doping on the performances of MnOx/TiO2 catalysts for NO reduction with NH3 at low temperature

In this paper, the Ca doped MnOx/TiO2 catalysts were synthesized through a sol–gel method, which exhibited promoting effects on selective catalytic reduction (SCR) of NO with NH3 at low temperature. The NO conversion of MnOx/TiO2 had been greatly improved from ca. 40% to 90% at 140 °C after Ca doping. After the catalysts being subjected to a variety of analytical measurements, we observed that the addition of Ca could result in better dispersion of MnOx on TiO2, leading to the enhancement of BET surface area and pore volume. This could be attributed to the strong interactions among calcium, manganese oxides and titania. Furthermore, an obvious increase in the amounts of ad-NOx species, especially monodentate nitrate and NO2− species, was also observed. All of these would give the contributions to the great improvement of catalytic activity by the addition of Ca.

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► The addition of Ca has strong promoting effect on low temperature SCR activity over MnOx/TiO2.
► The strong interaction after Ca doping leads to the increase in surface area and dispersion.
► The doping of Ca greatly increases the adsorption and oxidation of NO.