NH ₄ HSO ₄ Loading-Dependent NH ₃ -Selective Catalytic Reduction Performance of a CeO ₂ /SiO ₂ Catalyst via High-Temperature Calcination

The formation of NH4HSO4 is a key factor in sulfur-induced catalyst deactivation in NH3 selective catalytic reduction with NOx (NH3-SCR). This study investigates the effects of interactions between NH4HSO4 and CeO2 under high-temperature conditions on the catalytic performance of CeO2/SiO2 by systematically modulating the NH4HSO4 loading. Physicochemical characterization indicates that low loadings predominantly produce surface sulfate species, enabling the catalyst to sustain over 90% NOx conversion efficiency between 250 and 450 °C. In contrast, excessive NH4HSO4 loading beyond 1.0 mmol·g–1 triggers bulk sulfate formation, resulting in progressive activity decline and complete deactivation at 2.5 mmol·g–1. In situ diffuse reflectance infrared Fourier transform spectroscopy analysis demonstrates that the sulfated CeO2/SiO2 catalyst initially follows the Eley–Rideal mechanism, while excessive sulfation induces NH3 overadsorption on catalytic sites, thereby suppressing this pathway. These results elucidate high-temperature sulfur poisoning mechanisms and offer guidelines for the design of robust CeO2-based catalysts.