Selective Catalytic Oxidation of Ammonia to Nitrogen over Iron and Copper Bimetallic Catalysts

Abstract

Iron and copper bimetallic catalysts with fixed total contents of copper and iron were prepared by a co-impregnation method, and then used for selective catalytic oxidation of ammonia to nitrogen. The properties of the catalysts were characterized by N2 adsorption-desorption, H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The iron and copper bimetallic catalysts exhibited good activity and high selectivity of N2 at the gas hourly space velocity (GHSV) of 100000 h-1. The activity and N2 selectivity in the low temperature range increased with increasing Cu loading, whereas in the high temperature range (above 400°C) the selectivity of N2 was directly related to the content of iron. The highest NH3 conversion was achieved at about 350°C for Fe0.25Cu0.75/ZSM-5, and the N2 selectivity was up to 97% at 300°C. On the other hand, the extremely high N2 selectivity about 98% was obtained over Fe0.75Cu0.25/ZSM-5 at 500°C. In addition, N2O as the by-product and greenhouse gas was obtained in very low amounts for all the catalysts. The characterization results showed that the activity was influenced by the acid content and the amounts of copper species. Moreover, the highly reducing capacity could improve the N2 selectivity.