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 gamma-Al2O3 catalysts were synthesized for NO catalytic oxidation with low O-3/NO ratio of 0.5 at 80-200 degrees 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/gamma-Al2O3 calcined at 500 degrees C exhibited excellent performance. Meanwhile, there was a clear synergy between 20%-MnOx/gamma-Al2O3 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 H2O and SO2 exerted negligible impact on the catalytic activity of 20%-MnOx/gamma-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 O-3 was proposed.

Automated summary

The study found that 20%-MnOx/γ-Al2O3 exhibited excellent catalytic performance at 500 degrees Celsius, with a clear synergy between O-3 and the catalyst. In the NO oxidation reaction, lowering the NO concentration, increasing the O-2 content, and reducing the GHSV all led to improved NO conversion rates.