Catalytic oxidation of NO over MnO -CoO /TiO in the presence of a low ratio of O/NO: activity and mechanism.

In order to broaden the temperature range of NO oxidation reaction in flue gas and maintain high oxidation efficiency, various loading amounts of MnO -CoO /TiO mesoporous catalysts were tested in the catalytic oxidation of NO. It was found that 15%MnO -CoO (2 : 1)/TiO 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. O (O/NO < 1) combined with 15%MnO -CoO (2 : 1)/TiO 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 O over 15%MnO -CoO (2 : 1)/TiO were 5-13% higher than the calculated theoretical efficiencies. This indicated that there was a synergistic effect between O and 15%MnO -CoO (2 : 1)/TiO below 250 °C. Based on the results of DRIFTS studies, it was deduced that monodentate nitrates were the main intermediates that produced a synergistic effect due to the introduction of O. In addition, O 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.