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

In order to further improve the low-temperature oxidation performance of NO in flue gas, various manganese loadings supported on γ-Al 2 O 3 catalysts were synthesized for NO catalytic oxidation with low O 3 /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 Mn 3+ /Mn 4+ and abundant chemisorbed oxygen were conducive to catalytic activity, thereby 20%-MnO x /γ-Al 2 O 3 calcined at 500 °C exhibited excellent performance. Meanwhile, there was a clear synergy between 20%-MnO x /γ-Al 2 O 3 and O 3 . NO conversion was significantly higher in O 3 system and catalyst + O 3 system than that in catalyst + O 2 system, meanwhile catalyst + O 3 system exhibited higher NO conversion than O 3 system. Besides, NO conversion could be further improved with lower NO initial concentration, about 10% O 2 content and lower GHSV. Both H 2 O and SO 2 exerted negligible impact on the catalytic activity of 20%-MnO x /γ-Al 2 O 3 , but SO 2 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 O 3 was proposed. • 20%-Mn/γ-Al 2 O 3 calcined at 500 °C exhibited excellent performance of 82% NO conversion at 200 °C in the presence of O 3 . • The strong redox behavior, high Mn 3+ /Mn 4+ ratio and abundant chemisorbed oxygen are conducive to its high activity. • The NO initial concentration, O 2 content, GHSV, H 2 O and SO 2 on NO conversion over catalyst were also investigated. • The dynamic reaction process was recorded by in-situ DRIFTS, and possible reaction mechanism was proposed.