Promotional effect of aluminum doping on the sulfated Fe₂O₃ catalyst in selective catalytic reduction of NO with NH₃

Fe_mAl_nO_x catalysts were synthesized by the co-precipitation method and sulfated by (NH₄)₂SO₄ impregnation method. Among the catalysts, 1.2S/Fe₃Al₁O_x exhibits NO conversion exceeding 90% in the range of 260–410 °C both in the catalytic activity and resistance to K poisoning testing. Structures and physicochemical properties of catalysts were measured via different characterization techniques. Through comparative studies between 1.2S/Fe₂O₃ and 1.2S/Fe₃Al₁O_x, it reveals that doping Al into Fe₂O₃ can reduce its particle size, increase its specific surface area, and suppress the formation of crystalline phase Fe₂(SO₄)₃ at high calcination temperature, which is propitious to generate more surface sulfates in Fe_mAl_nO_x. NH₃-TPD and in-situ DRIFTS prove that K ions preferentially interact with surface sulfates, and more surface sulfates can provide more Brønsted acid sites to obtain higher ability of resistance to K poisoning. This work provides a simple strategy to improve the catalytic performances of Fe-based catalysts.

The relationships between catalytic performances and structures of sulfated Fe-based catalysts