A series of Cu-Mn-O oxides were prepared by homogeneous precipitation (labeled as U) and hydrothermal method (labeled as H), respectively. The catalysts have been characterized by means of XRD, BET, XPS, and FT-IR analyses. The activity of the catalysts for the reduction of NO with propane was evaluated. The results indicate that the composition of Cu-Mn-O system had dependence on preparation method and calcination temperature, which influenced the catalytic performance for the reduction of NO by propane. In the case of sample from hydrothermal method, Cu_1.5Mn_1.5O₄ and CuMn₂O₄ were predominant phases with the calcination temperature at range of 500～600 ℃. Then the Cu_1.5Mn_1.5O₄ disappeared as calcination temperature above 700 ℃. As for the samples prepared by urea homogeneous precipitation method, Cu_1.5Mn_1.5O₄ was main phase in all these samples calcined above 500 ℃. Therefore, for hydrothermal method, a phase transition from Cu_1.5Mn_1.5O₄ to CuMn₂O₄ occurred with the calcination temperature increasing from 600 to 700 ℃. This phase transition not only affected the grain size and specific surface area but also enhanced the catalytic activity in the reduction of NO by C₃H₈. According to the results of XRD, XPS and the structural character of spinel, the detailed structure formulas for Cu_1.5Mn_1.5O₄ and CuMn₂O₄ were obtained respectively, and by which the difference of catalytic performance of both spinels could be explained to a certain degree. XRD results demonstrated that the spinel structure of catalysts collapsed with appearance of MnO, CuO and Cu after reaction run over temperature of 600 ℃. It was so surprised that these mixed material possessed good activity for reaction, even higher than the fresh catalysts H-CuMn-700 and U-CuMn-700 in catalytic performance. Furthermore, according to FT-IR spectra, a great deal of (NO₂)_ad. and small amounts of (NO₃)_ad adsorbates, that were considered as intermediates, were observed over the catalysts after reaction. This result was in fair agreement with the “synergetic reaction mechanism”.

Key words: reduction of NO by propane, Cu_1.5Mn_1.5O₄, CuMn₂O₄