Catalytic decomposition performance for O3 and NO2 in humid indoor air on a MnOx/Al2O3 catalyst modified by a cost-effective chemical grafting method.

Abstract Processes based on non-thermal plasma (NTP) for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone (O 3) and nitrogen oxides (NO x). Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiO x , CoO x and MnO x with different weight percentage 1, 5 and 10 wt.%, deposited on a γ-Al 2 O 3 support. The O 3 removal efficiency (ORE) and the NO x removal efficiency (NRE) were very encouraging in dry air: about 65% and 80%, respectively, by using 2 g 5 wt.% MnO x /Al 2 O 3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity (RH) on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnO x /Al 2 O 3 catalyst with different trichloro(alkyl)silanes (TCAS). The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/g cat of modifying agent represents the best catalytic decomposition performance for O 3. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]