Study of Selective Catalytic Reduction Performance of Ce-Modified Iron-Based SAPO-34 Catalysts

Abstract

Fe-SAPO-34 catalysts exhibit excellent structural stability and redox properties but possess limited low-temperature activity and a narrow temperature window for selective catalytic reduction of NO_X. To address these limitations, a series of Ce-modified Fe-SAPO-34 catalysts with varying Ce/Fe molar ratios are synthesized via the impregnation method. Characterization (including Brunauer–Emmett–Teller, X-ray diffraction, X-ray photoelectron spectroscopy, Hydrogen temperature programmed reduction, Ammonia temperature programmed desorption) reveal that optimal Ce doping (Ce/Fe = 0.1) increases the Fe³⁺/Fe²⁺ ratio from 56.74 to 68.83% and the chemisorbed oxygen content from 73.88 to 80.23%. Ce modification improves the dispersion of Fe species, increases the specific surface area from 474.78 to 517.74 m⁻² g⁻¹, and enhances surface acidity, as indicated by an increase in total NH₃ desorption from 1.18 to 1.87 mmol g⁻¹. Consequently, the Ce–Fe/SAPO-34 catalyst with Ce/Fe molar ratio of 0.1 achieves 98.82% NO_X conversion at 360 °C and maintains over 98% conversion in the range of 330–440 °C, while lowering the activation temperature by 40 °C compared to Fe-SAPO-34.