Mn-Ce-Ti Catalysts On NH₃Selective Catalytic Reduction Of NO_x

Based on the selective catalytic reduction of NOx with NH3as the model reaction, we studied the catalytic performance of the Mn-Ce-Ti multiple oxide catalysts.By modulating the molar ratio of metal component, we found that the highest activity catalyst was Mn0.2Ce0.1Ti0.9, which could reach more than90%NOx conversion in150-300℃. Compared with Mno.2Ti0.8and Ce0.1Ti0.9catalysts, Mn0.2Ce0.1Ti0.9catalyst has higher activity, as well as great resistance to H2O and SO2.By using XRD, BET, XPS, SEM, Raman and DRIFTS characterization methods, we characterized and analysed the structure of the catalyst to explore mechanism of the Mn-Ce-Ti multiple oxide catalyst in reaction of eliminating the NOx. XRD, BET and SEM results showed that the catalysts of Mn-Ce-Ti mixed oxide prepared by the hydrothermal method have high specific surface area. The synergetic effect among Mn, Ce and Ti contributes to inhibt the catalysts from forming cystallizaion structure. The amorphous phase had formed in the Mn-Ce-Ti catalyst particlesthe. It meant that MnOx and CeO2have good dispersion on the TiO2surface. H2-TPR results showed that Mn0.2Ce0.1Ti0.7catalyst lowered the reaction temperature of Ce4+→Ce3+, which enhanced the reducibility of CeO2, and promoted the redox properties of catalyst. XPS results showed that the content of Mn3+in the catalyst was higher in Mn0.2Ce0.1Ti0.9catalyst, it might be due to the two reduction process of Ce4+→Ce3+and Ti4+→Ti3+which transfered electron to Mn4+and reduced to Mn3+. DRIFTS experiments showed that more active NH3and NO2species were absorb on the surface of Mn0.2Ce0.1Ti0.7catalyst. The production of the active intermediates, improved the catalytic reaction.In short, the synergetic effect among Mn, Ce and Ti of Mn0.2Ce0.1Ti0.9catalyst may produce a dual redox cycles (Mn4++Ce3+(?)Mn3++Ce4+, Mn4++Ti3+(?) Mn3++Ti4+) and the amorphous structure plays key roles for the high catalytic deNOx performance. in addition, The synergetic effect among Mn, Ce and Ti also contributes to the formation of reactive intermediate species, thus promoting the NH3-SCR to proceed.