Low Temperature Scr Denitration with Nh3 Via Synergistic Effect of Highly Dispersed Fe-Co Sites

Abstract

Environmentally friendly Fe-based catalysts have the potential to be alternatives to commercially used but toxic V-based catalysts for controlling nitrogen oxide emissions via selective catalytic reduction (SCR). However, traditional Fe-based catalysts, with their narrow active temperature range, struggle to adapt to the decreased flue gas temperatures that occur when boilers operate at low loads. Here, we design a Fe-Co/TiO2 catalyst to investigate the synergistic effect of Fe and Co in SCR by constructing highly dispersed Fe-Co paired sites. Compared to Fe/TiO2, the catalyst exhibits excellent low-temperature activity, with the T90 reduced by 92 °C and the active temperature range expanded fourfold. A series of characterization results, coupled with density functional theory calculations, reveal a strong electronic interaction within the Fe-Co active sites, leading to lower apparent activation energy (Ea = 31.1 kJ/mol), higher reactivity (TOF = 2.65 × 10-3 s-1). In addition, it is concluded that the SCR reaction process on Fe-Co/TiO2 follows both Eley-Rideal (E-R) and Langmur-Hinshelwood (L-H) mechanisms. The Fe-Co synergism dynamically promotes electron transfer from Fe to Co, thus activating the Fe(II)/Fe(III) self-healing cycle, which not only enhances the adsorption of reactants and desorption of products at the Fe site but also accelerates the activation of O2 at the Co site.

Keywords: NOx removal, NH3-SCR, Fe-Co/TiO2, highly dispersion catalysts, synergestic effect sites