Ni-modified MIL-100(Fe) catalysts for CO-SCR of NO and reaction mechanism

Abstract

To promote the activation of the catalysts in the presence of oxygen and at lower temperatures for the selective catalytic reduction of NO with CO (CO-SCR), iron-based metal-organic frameworks (MOFs) catalysts, called MIL-100 (Fe), were prepared by hydrothermal synthesis and further modified with Ni by wet impregnation method. The CO-SCR of NO was evaluated in a fixed-bed reactor. Results proved that the NO conversion over MIL-100(Fe) and 5.8 %Ni-modified catalysts under oxygen-free conditions was 96.6 % and 100 % at 325 °C, respectively. When 2 vol% oxygen was present, the NO conversions over MIL-100(Fe) and 5.8 %Ni modified catalysts at 250 °C were 37.2 % and 96.6 %, respectively, demonstrating that the Ni-modified MIL-100(Fe) catalyst obviously improved the CO-SCR reactivity under O2 atmosphere. UV–vis DRS, HRTEM, FTIR, TGA, etc., and in situ DRIFTS techniques were used to characterize the physical and chemical properties of the catalysts and study the reaction mechanism. The outcomes demonstrated that the incorporated Ni engaged in interactions with Fe the CO-SCR reaction, resulting in the formation 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 NOx substances into active substances. The adsorption behavior of NO, CO, and the reaction intermediates were investigated by in situ DRIFTS and a preliminary reaction path was proposed.