Manganese oxides supported on ACF N by a one‐step redox method for the low‐temperature NOx reduction with NH 3 : effect of acid addition

BACKGROUND In this study, manganese dioxide (MnO 2 ) was formed in situ on the surface of ACF N (nitric acid modified activated carbon fibres) by a one‐step redox method for the selective catalytic reduction (SCR) of nitric oxides (NOx) with ammonia (NH 3 ) at low temperature. Meanwhile, the water and sulfur dioxide (H 2 O and SO 2 ) deactivation mechanism were investigated. RESULTS Each acid, including hydrochloric, nitric and acetic (HCl, HNO 3 and CH 3 COOH), released H + in solution at different rates, which lead to distinct pH environments. As the driving force, it has an effect on the redox reaction, resulting in the different MnO 2 amount and performance of the MnO 2 /ACF N catalysts. The MnO 2 /ACF N (CH 3 COOH) catalyst exhibited good NH 3 ‐SCR activity, water resistance and sulfur resistance. CONCLUSION The MnO 2 /ACF N (CH 3 COOH) catalyst showed 3D growth and uniform distribution of MnO 2 sheets on the surface of the support, which resulted in a larger specific surface area and better redox properties. The CH 3 COOH can gradually decompose H + so that H + is given priority to internal diffusion. The redox reaction preferentially took place in the interior, thereby promoting the formation of more MnO 2 , which is beneficial to the NH 3 ‐SCR reaction. © 2019 Society of Chemical Industry