Ni-Modified Mil-100(Fe) Catalysts for Co-Scr and Reaction Mechanism

It is an economical and environmentally friendly denitrification technology using carbon monoxide, commonly present in flue gases, as a reducing agent for the selective catalytic reduction of NO (CO-SCR). However, the low reactivity of the catalysts under an oxygen atmosphere has always been the bottleneck of CO-SCR. To promote the activation of the catalysts in the presence of oxygen for CO-SCR reaction, iron-based metal-organic frameworks (MOFs) catalysts, called MIL-100 (Fe), were prepared by hydrothermal synthesis and further modified with Ni metal by wet impregnation method in this work. The study found that the NO conversion of MIL-100(Fe) and 5.8%Ni-modified catalysts under oxygen-free conditions was 96.6% and 100% at 325 °C, respectively. Additionally, when oxygen was present (2 vol%), the NO conversions of MIL-100(Fe) and 5.8%Ni modified catalysts at 250 °C were 37.2% and 96.6%, respectively, demonstrating that the Ni-doped MIL-100(Fe) catalyst has excellent oxygen resistance. The mechanism of antioxidant properties after Ni addition was investigated using UV-vis DRS, HRTEM, FTIR, TGA, and in situ DRIFTS techniques. The outcomes demonstrated that the incorporated Ni could engage in interactions with Fe material in the CO-SCR reaction resulting in the production of additional surface or surface synergistic oxygen vacancies (SOV and SSOV), thus improving the redox performance of catalysts. Additionally, the Ni-modified catalyst had better redox performance, which was beneficial to converting the adsorbed NO x substances into active substances. CO-SCR reaction followed the Langmuir- Hinshlwood (L-H) and Eley-Rideal (E-R) mechanisms.