Comparative Study of NO Oxidation under a Low O₃/NO Molar Ratio Using 15% Mn/TiO₂, 15% Co/TiO₂, and 15% Mn–Co(2:1)/TiO₂ Catalysts

Abstract

NO catalytic oxidation using 15% Mn/TiO 2, 15% Co/TiO 2, and 15% Mn–Co(2:1)/TiO 2 with a low molar ratio of O 3 /NO was investigated. O 3 improved NO catalytic oxidation performance, including the tolerance to H 2 O and SO 2 . Synergism occurred more clearly between 15% Mn–Co(2:1)/TiO 2 and O 3 (O 3 /NO = 0.5) than between the other two catalysts and O 3, below 250 °C. In situ diffuse reflectance infrared Fourier-transform spectroscopy indicated that O 3 accelerated the mass production of monodentate nitrates on 15% Mn–Co(2:1)/TiO 2 compared with 15% Mn/TiO 2 . Catalyst characterization results illustrated that cobalt-loading created lots of oxygen vacancies on 15% Mn–Co(2:1)/TiO 2, promoting redox capability and enhancing NO catalytic oxidation. In addition, 15% Mn–Co(2:1)/TiO 2 contained more Mn 2 O 3, Mn 3+, Mn 4+, and chemisorbed oxygen on its surface than 15% Mn/TiO 2 and 15% Co/TiO 2, which could promote the synergistic effect of the catalyst. This study could reduce the consumption of ozone and reduce the harm of ozone leakage in NO oxidation, which could guarantee a high efficiency of NO oxidation in a wide temperature range (50–400 °C).