Low-temperature selective catalytic reduction of NO with NH3 over Ni–Mn–Ox catalysts

Abstract

A series of manganese–nickel oxide catalysts with different Ni/Mn ratios were prepared using a hard template method with KIT-6 as the template. These mesoporous nanomaterials were characterized using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy and X-ray photoelectron spectroscopy (XPS). The low temperature selective catalytic reduction (SCR) of NO with NH₃ in the presence of excess O₂ was investigated. At a gas hourly space velocity (GHSV) of 38 000 h⁻¹, the Ni(1 : 3)–MnO_x (Ni/Mn = 1 : 3) catalyst had the highest activity, giving an NO conversion of 81.3% at 60 °C and 100% from 100 to 220 °C. The Ni(1 : 3)–MnO_x catalyst had high N₂ selectivity, excellent stability, good H₂O resistance and functioned well at various GHSVs. The BET, XRD and XPS results showed that the Ni(1 : 3)–MnO_x catalysts had large surface areas (187 m² g⁻¹) and that a more amorphous phase was formed as the nickel content was increased. The Mn⁴⁺ and chemisorbed oxygen are the main active species for the SCR reaction. These properties are desirable for low-temperature SCR catalysts.