Influence of calcination temperature on the catalytic activity of Mn/TiO₂ for NO oxidation

The influence of calcination temperature on the catalytic activity of Mn-based catalysts impregnated on TiO₂ for the oxidation of NO was studied. The results showed that, relatively low calcination temperature was beneficial to promote the catalytic activity of Mn/TiO₂ catalysts. The catalysts were characterized by various techniques to study the influence mechanism of calcination temperature, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), H₂ temperature programmed reduction (H₂-TPR) and O₂ temperature programmed desorption (O₂-TPD). It could be concluded that Mn₂O₃ played a dominant role in the process of NO oxidation, and the relatively lower calcination temperature could enhance the percentage of Mn₂O₃ in MnO_x, as well as promote the dispersion of MnO_x on TiO₂, thus raising the catalytic activity of Mn/TiO₂. When the calcination temperature was higher than 500 ℃, the agglomeration began to appear, and the crystalline phase of TiO₂ was transformed from anatase to rutile, Mn₂O₃ was, as well, transformed from amorphous phase to crystalline phase. The test results of H₂-TPR and O₂-TPD showed that relatively lower calcination temperature was beneficial to the reduction ability of Mn/TiO₂ catalysts and the desorption of chemisorbed O^2- on catalysts surface, the interaction of the two factors resulted in good mobility of chemisorbed O^2- on catalysts surface, which was good for the activity of catalysts.