Fe_2O_3/HY Catalyst: A Microporous Material with Zeolite-Type Framework Achieving Highly Improved Alkali Poisoning-Resistant Performance for Selective Reduction of NO_x with NH_3

摘要

The commercially available V_2O_5/WO_3-TiO_2 is a well-known catalyst for selective catalytic reduction (SCR) of NO with NH_3. When alkali ions are present in the exhaust (e.g., as impurities such as dust) of a reactor containing commercial V_2O_5/ WO_3-TiO_2, alkali poisoning occurs, deactivating the catalyst. Consequently, there is substantial interest in the development of better-performing and more durable NH_3-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 Fe_2O_3/HY catalyst. Catalytic tests showed that the Fe_2O_3/HY retained 100% of its original catalytic reactivity for NH_3-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 V_2O_5/WO_3-TiO_2. The catalyst activity of Fe_2O_3/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 Fe_2O_3. 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.