https://orcid.org/0000-0002-2067-6011
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ABSTRACT
The chromium, iron or zirconium oligomer cations pillared interlayered montmorillonite supported 10 wt% MnOx were synthesized and studied for the flue gas NOx removal in metallurgical sintering process. The physicochemical properties of these catalysts were detected by some characterization methods, such as XRD, N2 adsorption–desorption, SEM, H2-TPR, and NH3-TPD. The Mn/Zr-PILM catalyst had the highest NOx conversion with 91.8% at 200°C. And the Mn/Fe-PILM catalyst had the highest NOx conversion between 140°C and 160°C. This is because zirconium or iron pillared montmorillonite increases the specific surface area and acidic sites of catalyst, which provided more adsorption sites and activation sites for NO and NH3, thus promoting low-temperature catalytic activity. The XRD results expressed that the pillared elements successfully pillared into Na-montmorillonite and the manganese active components had good dispersibility on the surface of catalyst. The N2 adsorption–desorption isotherm indicated that the metal pillared carrier had fractured mesoporous structure and the specific surface area was increased. The Mn/Zr-PILM and Mn/Fe-PILM catalyst had abundant acidity with 61.56 μmol/g and 57.71 μmol/g, respectively. The large amount of acid sites favored the adsorption of ammonia in the Langmuir–Hinshelwood or Eley–Rideal mechanisms in the low-temperature NH3-SCR process. The Mn/Fe-PILM catalyst had the best N2 selectivity and Mn/Cr-PILM has poor N2 selectivity. This was due to that iron element restrains the side reaction for N2O production and chromium promoted the N2O production by strong oxidation.