Performance and mechanism of MnOx/γ-Al2O3 for low-temperature NO catalytic oxidation with O3/NO ratio of 0.5

Abstract

In order to further improve the low-temperature oxidation performance of NO in flue gas, various manganese loadings supported on γ-Al2O3 catalysts were synthesized for NO catalytic oxidation with low O3/NO ratio of 0.5 at 80–200 °C, the key factors effecting NO conversion and the reaction mechanism were also investigated. Characterization results showed that strong redox behavior, high Mn3+/Mn4+ and abundant chemisorbed oxygen were conducive to catalytic activity, thereby 20%-MnOx/γ-Al2O3 calcined at 500 °C exhibited excellent performance. Meanwhile, there was a clear synergy between 20%-MnOx/γ-Al2O3 and O3. NO conversion was significantly higher in O3 system and catalyst + O3 system than that in catalyst + O2 system, meanwhile catalyst + O3 system exhibited higher NO conversion than O3 system. Besides, NO conversion could be further improved with lower NO initial concentration, about 10% O2 content and lower GHSV. Both H2O and SO2 exerted negligible impact on the catalytic activity of 20%-MnOx/γ-Al2O3, but SO2 inhibited its catalytic activity irreversibly due to the deposition of S-species on the catalyst surface. According to the in-situ DRIFTS analysis, the intermediate by-products and their changes during the NO adsorption were recorded. Furthermore, a possible reaction mechanism of NO catalytic oxidation with O3 was proposed.