Promotion of transition metal oxides on the NH3-SCR performance of ZrO2-CeO2 catalyst

Chromium oxide and manganese oxide promoted ZrO2-CeO2 catalysts were prepared by a homogeneous precipitation method for the selective catalytic reduction of NOx with NH3. A series of characterization including X-ray diffraction （XRD）, high-resolution transmission electron microscope （HR-TEM）, Bmnaue-Emmett-Teller （BET） surface area analysis, H2 temperature- programmed reduction （H2-TPR）, and X-ray photoelectron spectroscopy （XPS） were used to evaluate the influence of the physicochemical properties on NH3-SCR activity. Cr-Zr-Ce and Mn-Zr-Ce catalysts are much more active than ZrO2-CeO2 binary oxide for the low temperature NH3-SCR, mainly because of the high specific surface area, more surface oxygen species, improved reducibility derived from synergistic effect among different elements. Mn-Zr-Ce catalyst exhibited high tolerance to SO2 and H2O. Cr-Zr-Ce mixed oxide exhibited〉80% NO,. conversion at a wide temperature window of 100 ℃ 300℃. In situ DRIFT studies showed that the addition of Cr is beneficial to the formation of Bronsted acid sites and prevents the formation of stable nitrate species because of the presence ofCr6 ＋. The present mixed oxide can be a candidate for the low temperature abatement of NOx.