Effects of different manganese precursors as promoters on catalytic performance of CuO-MnOx/TiO2 catalysts for NO removal by CO

Two different precursors, manganese nitrate (MN) and manganese acetate (MA), were employed to prepare two series of catalysts, i.e., xCuyMn(N)/TiO2 and xCuyMn(A)/TiO2, by a co-impregnation method. The catalysts were characterized by XRD, LRS, CO-TPR, XPS and EPR spectroscopy. The results suggest that: (1) both xCuyMn(N)/TiO2 and xCuyMn(A)/TiO2 catalysts exhibit much higher catalytic activities than an unmodified Cu/TiO2 catalyst in the NO + CO reaction. Furthermore, the activities of catalysts modified with the same amount of manganese are closely dependent on manganese precursors. (2) The enhancement of activities for Mn-modified catalysts should be attributed to the formation of the surface synergetic oxygen vacancy (SSOV) Cu+-square-Mny+ in the reaction process. Moreover, since the formation of the SSOV (Cu+-square-Mn-3(+)) in the xCuyMn(N)/TiO2 catalyst is easier than that (Cu+-square-Mn2+) in the xCuyMn(A)/TiO2 catalyst, the activity of the xCuyMn(N)/TiO2 catalyst is higher than that of the xCuyMn(A)/TiO2 catalyst. This conclusion is well supported by the XPS and EPR results.