The promotion effect of Fe to Cu-SAPO-34 for selective catalytic reduction of NOx with NH3

摘要

A number of Fe loaded Cu-SAPO-34 (Fe: Cu-SAPO-34 = 0.5, 1 and 1.5 wt.%) catalysts were prepared with incipient wetness impregnation of iron acetate solution on a one-pot synthesized Cu-SAPO-34 sample. The Fe/Cu-SAPO-34 sample with 1 wt.% Fe loading shows the best selective catalytic reduction performance among the samples tested at temperatures above 200 degrees C. The results of ultraviolet-visible diffuse reflectance spectroscopy indicate that isolated Fe3+ ions, FexOy oligomers, and Fe2O3 particles coexist in the Fe incorporated samples. Further examinations tell that the bulk CuO on the surface in the Cu-SAPO-34 sample with appropriate amount of Fe addition transforms to isolated Cu2+ ions, which enhances its catalytic activity in the temperature range of 200-350 degrees C. The Fe: Cu-SAPO-34 = 1 wt.% sample exhibits a lower NH3 oxidation ability at high temperatures than that of Cu-SAPO-34, which is due to the reduced amount of bulk CuO species on the surface. Both the reduced NH3 oxidation ability and the additional isolated Fe3+ sites contribute to the excellent activity of the Fe: Cu-SAPO-34 = 1 wt.% sample above 350 degrees C.