Experimental study on selective catalytic reduction of NO by C3H6 over Fe-Ag/Al2O3 catalysts

Abstract

AbstractSol-gel and impregnation methods were used to prepare the Fe-Ag/Al2O3 catalysts supported on the monolithic cordierite with different Fe/Ag loading ratios. The catalytic performance to reduce NO with C3H6 was evaluated in a one-dimensional electrically heated temperature programmed ceramic tubular reactor in simulated flue gas atmosphere at 200–700°C. The results show that the NO reduction efficiency on 7.2Fe/1.9Ag/20Al2O3/CM with C3H6 is more than 90% and reaches about 100% at the temperatures of 500°C and 550°C respectively. Iron can effectively improve the ability of Ag/20Al2O3/CM catalysts to resist SO2 and H2O in flue gas. When SO2 and H2O are 0.02% and 8% in the flue gas, the NO reduction efficiency is almost not influenced on 7.2Fe/1.9Ag/20Al2O3/CM at 500°C. The 90% NO reduction efficiency is maintained during 6 h without decrease. However, the catalytic activity of 2Ag/20Al2O3/CM without iron modification is strongly influenced by SO2 and H2O in the flue gas. The NO reduction efficiency on Ag/20Al2O3/CM decreases rapidly from about 70% to 46% and 25% respectively, when the SO2 and H2O are 0.02% and 8% in the flue gas. The results of XRD and SEM of the catalyst show that AgFeO2 and Fe3+ are formed in the 7.2Fe/1.9Ag/20Al2O3/CM catalyst after the modification by iron, and the surface of the catalyst become loose and porous, forming Fe3O4-based needle-like and flaky crystals. H2-TPR results show that 7.2Fe/1.9Ag/20Al2O3/CM has better reduction properties than Ag/20Al2O3/CM in the wider temperature range. Pyridine adsorption Infrared Spectroscopy (Py-FTIR) experimental results show that Fe increases the Lewis acid sites in the catalyst surface.