Reaction of NO + CO over Ce-Modified Cu–FeO_x Catalysts at Low Temperature

Abstract

A series of Ce-modified Cu–FeO x catalysts were synthesized with a sol–gel hydrothermal method. These catalysts contained different molar ratios of Ce, Cu, and Fe, and were applied to the process of NO catalytic removal by CO (CO-deNO). The physical and chemical parameters of the samples were characterized by XRD, XPS, ESR, H2-TPR, NO-TPO, and NO-TPD techniques. Moreover, the CO-deNO mechanisms for the representative catalysts were investigated by in situ DRIFTS. The SO2 and H2O resistances, and their corresponding mechanisms, were also systematically investigated. The catalytic activity testing shows that the optimized molar ratio of Cu, Ce, and Fe is 1:0.5:1.5. At this ratio, the CO-deNO efficiency is highest, but the N2O selectivity is also relatively high. Increasing the Fe percentage could reduce the N2O concentration. The characterization indicates that, at the optimized ratio, the interaction between Fe and Cu is at its strongest, which could increase the formation probability of surface synergistic oxygen vacancies. The Ce existing in the catalysts plays a key role in the adsorption of NO and CO. Moreover, the increasing percentage of Fe could enhance the adsorption and dissociation of NO, and promote the evolution of CO, which can compensate for the effects of the weaker interaction. The NO and CO evolution pathway runs as follows: NO → M–NO2 → NO2 – → M–N2O/NO3 – → N2O/N2; CO → COO– → CO3 2– → CO2. The H2O and SO2 resistance tests suggest that the appropriate incremental increase in Fe percentage will increase the SO2 or H2O resistance, with the underlying mechanism being that Fe inhibits the formation of sulfates and produces more water adsorption sites, and the increasing Fe percentage would optimize the pore structure.

Recent advances in heighten sulfur resistance of SCR catalysts: A review

“…Sulfur dioxide and water vapor had little effect on the catalytic activity of Fe/Al-PILC. Wang et al [15] pointed out that an increase in Fe content is beneficial to the conversion of CO and NO adsorbed on the catalyst surface (NO → M−NO2 → NO2 − → M−N2O/NO3 − → N2O/N2; CO→ COO − → CO3 2− → CO2). The H2O and SO2 resistance test results showed that an appropriate increase in the proportion of Fe will promote the resistance of SO2/H2O.…”

IrSn Bimetallic Clusters Confined in MFI Zeolites for CO Selective Catalytic Reduction of NOx in the Presence of Excess O2

“…The selective catalytic reduction of NO x by using CO has been investigated. Many catalysts have been developed for the CO-SCR reaction, such as Cu-based, , Co-based, , Fe-based, , and Pt-based , catalysts. However, most catalysts have exhibited poor NO x removal efficiency in the presence of excess O 2 owing to the rapid combustion of CO at high temperatures.…”

Recent Advances of Cu-Based Catalysts for NO Reduction by CO under O2-Containing Conditions

“…Therefore, low-cost transition metal-based catalysts have attracted widespread attention [16]. Among them, Cu-based [17,18], Fe-based [19], and Co-based [20] catalysts are widely studied.…”

“…Many supported Cu-based catalysts such as Cu/CeO2-Fe2O3 [21], CuO/CeO2-Fe2O3 [22], Cu/Fe2O3-CeO2/ZrO2 [23], and CuOx/CeO2 [24] exhibit excellent catalytic performance, with NO conversion usually surpassing 90% at 200 °C. Moreover, non-supported catalysts such as CuCeOx [25] and Cu1Ce0.5Fe1.5O4.25 [18] also have high denitrification efficiency at 100-200 °C. However, the reaction conditions of the above catalysts are O2-free.…”