Investigation on Fe-Co binary metal oxides supported on activated semi-coke for NO reduction by CO

•When Fe and Co species were co-loaded onto activated semi-coke support, there would be a mix crystalline effect increasing the possibility to form oxygen vacancies.•In a synergy surface oxygen vacancy, metal with higher electronegativity would act as the redox site, while another acts as assistance.•At low temperatures, Fe-Co oxides supported by activated semi-coke could adsorb NO species and transform them to nitrites, and with the presence of CO, these nitrites would be decomposed to N2O. While high temperature could promote NO species transforming to coordinated nitrates, which reacted with CO to produce N2.

In this study, different amounts of Fe and Co species were loaded on activated semi-coke (ASC) using a hydrothermal method for the reduction of NO by CO. The series of prepared catalysts were characterized by SEM, N2 physisorption, ICP, XRD, XPS, H2-TPR, and in situ DRIFTS, as well as ESR and Raman spectroscopy. In addition, the denitration (deNOx) performance and water/SO2 resistance were investigated. The precursor solution with a molar ratio of 0.8:0.2 for Fe:Co (Fe0.8Co0.2/ASC) produced spherical clusters that were uniformly dispersed on the surface. Moreover, Fe0.8Co0.2/ASC exhibited the most effective deNOx activity. The highest deNOx activity for Fe0.8Co0.2/ASC (determined from the characterization) was attributed to the high fraction of Brønsted acid sites, high possibility for the formation of oxygen vacancies, and a strong redox performance. The DRIFTS results suggested a possible mechanism involving the adsorption of NO on the Fe0.8Co0.2/ASC surface, followed by its transformation to nitrates or nitrite/nitro species. At low temperatures (<200 °C), nitrates were predominantly adsorbed on the surface and could react with CO species, affording CO2 and N2O. However, with increasing reaction temperatures (>200 °C), the coordinated nitrates and CO species on the surface reacted with the produced CO2 and N2. The effects of water and SO2 on the deNOx performance were examined. In the presence of only water, the deNOx performance decreased because of the competitive adsorption with NO, and in the presence of only SO2, reversible deactivation was observed; however, if both water and SO2 were present, irreversible catalyst deactivation was observed.

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