In situ synthesis of SiO2-doped CoMnFe layered double oxides catalyst: Mechanism for enhancing NH3-SCR activity and resistance to poisoning

Based on interface effects and structural optimization, the properties of SiO2 and layered double hydroxides (LDHs) material were integrated to prepare SiO2/CoMnFeOx composites for denitration technology. The optimum SiO2(0.5)/Co0.5Mn1.5Fe1Ox catalyst had excellent NOx conversion (>90%) and N2 selectivity (>80%) at 150-250°C. In addition, the stability of SiO2(0.5)/Co0.5Mn1.5Fe1Ox against SO2 and H2O was much higher than that of Co0.5Mn1.5Fe1Ox (14~20%) and Co-Mn-Fe/SiO2 (56~61%) operating at 200°C for 30 h. The enhanced N2 selectivity of SiO2(0.5)/Co0.5Mn1.5Fe1Ox catalyst was achieved by inhibiting the formation of N2O by-products through “NOx + NH3 + O2” pathway. The abundant surface adsorbed oxygen and active species, appropriate surface acid and redox ability promoted the NH3-SCR reaction of SiO2(0.5)/Co0.5Mn1.5Fe1Ox catalyst. In situ DRIFTS analysis and density functional theory (DFT) calculations were conducted to discuss the adsorption/activation of reactive species, reaction pathways, and mechanism of resistance to SO2 and H2O poisoning. This work provided a new strategy for the development of low-medium temperature NH3-SCR catalysts with excellent resistance to SO2 and H2O.