Fe₂O₃/HY Catalyst: A Microporous Material with Zeolite-Type Framework Achieving Highly Improved Alkali Poisoning-Resistant Performance for Selective Reduction of NO_x with NH₃

The commercially available V₂O₅/WO₃–TiO₂ is a well-known catalyst for selective catalytic reduction (SCR) of NO with NH₃. When alkali ions are present in the exhaust (e.g., as impurities such as dust) of a reactor containing commercial V₂O₅/WO₃–TiO₂, alkali poisoning occurs, deactivating the catalyst. Consequently, there is substantial interest in the development of better-performing and more durable NH₃–SCR catalysts with an improved resistance to alkali deactivation. For the present study, the protonated (H⁺) form of zeolite Y, HY, was used as a support and acted as buffer zone, leading to trapping (sticking) of foreign alkali poisons in the zeolite pore structure, preventing alkali poisoning of the Fe₂O₃/HY catalyst. Catalytic tests showed that the Fe₂O₃/HY retained 100% of its original catalytic reactivity for NH₃–SCR reaction even after 1000 μmol Na⁺ g^–1 poisoning. 1000 μmol Na⁺ g^–1 treatment indicates a 26 000-h exposure under an alkaline dust-containing condition. In contrast, upon 1000 μmol Na⁺ g^–1 treatment, severe alkali deactivation occurred for a commercial V₂O₅/WO₃–TiO₂. The catalyst activity of Fe₂O₃/HY remained unchanged because of the intercalation of Na⁺ in the internal HY zeolite pores that impedes the blocking of Na⁺ poison to the external active sites of Fe₂O₃. The findings in this work suggest that the zeolite HY may be revealed as an attractive building block for designing an alkali poisoning-resistant catalyst.