Oxidation-absorption process for simultaneous removal of NO x and SO 2 over Fe/Al 2 O 3 @SiO 2 using vaporized H 2 O 2 .

3% Fe/Al ₂ O ₃ and 3% Fe/Al ₂ O ₃ @SiO ₂ were prepared to investigate the performance in simultaneous removal of NO _x and SO ₂ using vaporized H ₂ O ₂ . Certain paraments were changed to explore the activity of catalysts, including temperature, H ₂ O ₂ concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al ₂ O ₃ @SiO ₂ . Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al ₂ O ₃ , 3% Fe/Al ₂ O ₃ @SiO ₂ exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO ₂ and 93.76% for NO _x . Moreover, 3% Fe/Al ₂ O ₃ @SiO ₂ kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO ₂ , which could improve the activity of catalyst at high temperature and high SO ₂ concentration. Besides, the mechanism of SO ₂ molecules on simultaneous removal was investigated. On one hand, a part of H ₂ O ₂ was consumed by SO ₂ molecules without catalyst, which resulted in the drop of NO _x removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO ₂ over the catalyst. On the other hand, the presence of SO ₂ was beneficial for NO _x removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO ₂ by NaOH solution.
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