Catalytic Mechanism of NaY Zeolite Supported FeSO₄ Catalyst for Selective Catalytic Reduction of NO_x

The experimental results suggested that FeSO₄-NaY and FeSO₄-ZSM-5 prepared by impregnation method performed well in NO_x removal. The NO_x removal rates of the prepared catalyst were 20–35% higher than those of pure FeSO₄, The effective temperature window was largely expanded with the best performance temperature shifted from 440 to 340°C. SO₂ and H₂O in flue gas had no obvious effect on catalyst performance. Mössbauer spectrometry, XPS and in-situ infrared spectra analysis had been employed to investigate the catalytic mechanism of catalysts. It had been found that FeSO₄, Fe(OH)SO₄ and Fe₂O(SO₄) were the major components existing in the prepared catalyst, with their portions related to carrier type and preparing condition. FeSO₄ combined tighter with carriers after de-NO_x reaction. Fe₂O₃ and the chemical bond between Fe and Al had been found. Fe(OH)SO₄ was better in terms of NO_x removal than that of Fe₂O(SO₄). NH₃ absorbed on FeSO₄-NaY catalyst generated the spectra of NH ₄ ⁺ and NH₃, suggesting the Eley-Rideal mechanism. FeSO₄-ZSM-5 absorbed both NH₃ and NO and the carrier (ZSM-5) itself demonstrated some catalytic effect, indicating a different reaction mechanism. \( {\text{SO}}_4^{{2 - }} \) from FeSO₄ and hydroxyl from carrier jointly enhanced the adsorption of reaction gas. Fe provided the active sites for the reaction between NH₃ and NO.