Synergistic Effects of Ceria and pH‐Controlled Strong Electrostatic Adsorption on Silver/Alumina Catalysts for Ethylene Epoxidation: A Structure–Performance and Durability Study

Abstract This study investigates the profound impact of support composition (α‐Al 2 O 3 vs. CeO 2 /α‐Al 2 O 3 ) and synthesis pH on the structural and catalytic properties of silver‐based catalysts for ethylene epoxidation. Catalysts were prepared via the strong electrostatic adsorption (SEA) technique, allowing for precise control over silver and promoter distribution. Characterization revealed that the CeO 2 /α‐Al 2 O 3 support (Cat‐105) exhibited a significantly enhanced BET surface area of 4.1 m 2 /g compared to pure α‐Al 2 O 3 (Cat‐101, 0.8 m 2 /g), coupled with exceptional thermal stability up to 550 °C due to semi‐crystalline, well‐dispersed CeO 2 . Electron dispersive spectroscopy (EDS) demonstrated that at pH f = 8.95 (Cat‐108), silver predominantly adsorbed onto CeO 2 particles, attributed to the neutral Al 2 O 3 surface and slightly negatively charged CeO 2 . Conversely, at higher pH f values (Cat‐106, Cat‐107), silver adsorbed on both CeO 2 and Al 2 O 3 . Notably, a synthesis pH f of 12.3 (Cat‐106) yielded the smallest silver crystallite size (30 nm) and highest CeO 2 surface coverage by silver. Ethylene epoxidation was employed as a diagnostic reaction to probe structure–performance correlations. Catalysts synthesized at pH ∼10.7–12.3, which displayed smaller Ag crystallites and higher Ce coverage, exhibited improved EO/CO 2 ratios. Accelerated aging studies at 300 °C for 6 weeks showed that ceria significantly mitigates silver particle aggregation; Cat‐106 (ceria‐containing) experienced less growth (from 51 to 81 nm average diameter) compared to Cat‐102 (ceria‐free), which saw growth from 76 to 192 nm. These findings highlight that ceria incorporation and precise pH control during synthesis are critical for enhancing silver dispersion, thermal stability, and ultimately, the lifespan of ethylene epoxidation catalysts.