In order to broaden the temperature range of NO oxidation reaction in flue gas and maintain high oxidation efficiency, various loading amounts of MnO x -CoO x /TiO2 mesoporous catalysts were tested in the catalytic oxidation of NO. It was found that 15%MnO x -CoO x (2 : 1)/TiO2 demonstrated the best adsorption performance to oxygen species and contained more oxygen vacancies, as well as the best surface oxygen mobility, thus exhibiting excellent NO catalytic oxidation activity. O3 (O3/NO < 1) combined with 15%MnO x -CoO x (2 : 1)/TiO2 improved the oxidation efficiency of NO at 50-400 °C, especially below 250 °C. When the temperatures were less than 250 °C, the oxidation efficiencies of NO by O3 over 15%MnO x -CoO x (2 : 1)/TiO2 were 5-13% higher than the calculated theoretical efficiencies. This indicated that there was a synergistic effect between O3 and 15%MnO x -CoO x (2 : 1)/TiO2 below 250 °C. Based on the results of in situ DRIFTS studies, it was deduced that monodentate nitrates were the main intermediates that produced a synergistic effect due to the introduction of O3. In addition, O3 accelerated the transformation between nitrate species, decreased the decomposition temperature of nitrate species, and inhibited the accumulation of nitrate ions, thus improving the oxidation efficiency of NO.
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