Hydrothermally Stable Cu‐SAPO‐34 From Attapulgite by Dual‐Silane Modification for NH ₃ ‐SCR

ABSTRACT

For ammonia‐selective catalytic reduction (NH ₃ ‐SCR) catalysts, critical performance metrics include a broad operating temperature window, high nitrogen oxides (NO _x ) conversion efficiency, near‐unity N ₂ selectivity, and long‐term durability under harsh hydrothermal conditions. This study introduces attapulgite—an abundant low‐cost silicon source—as the primary Si precursor, with partial substitution by silicon from silane coupling agents dimethoxydiphenylsilane (DMDPS) and dimethyloctadecyl[3‐(trimethoxysilyl)propyl]ammonium chloride (TPOAC) during hydrothermal synthesis. A dual‐modification strategy enables concurrent silanization and mesostructural engineering of the silicoaluminophosphate‐34 (SAPO‐34) framework. Cu‐SAPO‐34 catalysts, prepared via incipient wetness impregnation, exhibit tailored morphology, enhanced mesopore formation, and modulated acidity. CuDMDPS‐0.2 demonstrates the highest density of active isolated Cu ²⁺ species and superior low‐temperature NO _x conversion, whereas both CuDMDPS‐0.2 and CuTPOAC‐0.08 retain exceptional hydrothermal stability after aging at 700°C for 16 h. Compared to unmodified CuSAPO‐34‐Micr, modified catalysts maintain high NO _x conversion over a broad window, with minimal Brunauer–Emmett–Teller surface area loss (< 6.52%), high isolated Cu ²⁺ retention (> 88.47%), and preserved acidity (> 80.71%). This work establishes a cost‐effective mechanism‐guided approach for designing highly active hydrothermally stable NH ₃ ‐SCR catalysts, advancing their practical application in emissions control.