Poisoning Effect of SO₂ on NO Reduction by i-Butane over Fe/ZSM-5 Prepared by Sublimation Method

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.203, Iss.2, 2001-10, pp. : 369-374

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Abstract

X-ray photoelectron spectroscopy (XPS) in situ electron paramagnetic resonance (EPR), in situ Fourier transform infrared spectroscopy (FT-IR), SO₂ temperature-programmed desorption (TPD), and reaction tests were performed to investigate the poisoning effect on the selective catalytic reaction of NO by i-butane over Fe/ZSM-5. Kinetic studies at 623 K, showed that the presence of SO₂ in the reaction mixture poisoned Fe/ZSM-5 irreversibly. XPS studies of Fe/ZSM-5 after reaction with SO₂ at 623 K revealed the formation of sulfate species, which corresponds well to the SO₂ TPD result. in situ EPR spectra showed that the lines arising from the distorted tetrahedral Fe³⁺ ions at g≈5.8 and 6.5, which were known to be reactive species, disappeared and a new and sharp one at g≈1.9978 assigned to paramagnetic coke species appeared. The preadsorption of SO₂ suppressed the formation of the IR bands arising from Fe–NO₂ (1623 cm^-1) and Fe–NO₃ (1573 cm^-1). On the basis of these results, SO₂ deactivated Fe/ZSM-5 by suppressing the formation of Fe–NO_y (y=2, 3) complexes and promoting the formation of carbonaceous deposits, which resulted in consumption of the active Fe³⁺ sites.