Effect of Ag on deNOx performance of SCR-C3H6 over Fe/Al-PILC catalysts

Abstract

Silver has been used to modify the iron-based catalyst supported on alumina pillared montmorillonite to enhance its activity at lower temperature (<300°C). Bimetallic Ag-Fe/Al-PILC (Pillared interlayer clay) was prepared by the ultrasonic impregnation method and performance was tested on a fixed bed reactor. The experiment results showed that silver obviously improved the catalyst activity at a lower temperature. The NO conversion efficiency of Ag-Fe/Al-PILC at 250°C was 60%, which was higher than Fe/Al-PILC (20%). The maximum 82% NO conversion and 100% N2 selectivity were obtained by 2.1Ag-Fe/Al-PILC at 250°C. Moreover, Ag-Fe/Al-PILC revealed better resistance to H2O and SO2. The catalyst characterization was conducted by several techniques with respect to the microstructure and physicochemical properties. According to the effects of N2-adsorption and desorption tests, Ag-Fe/Al-PILC formed a stable overall structure and presented a large internal specific surface area. Besides, XRD and UV-vis proved that the Ag-Fe solid solution, Ag+ and Agδ+ n species formed on the surface of the catalyst were the key factors affecting its low temperature activity. XPS results suggested that there was electron transfer between Ag and Fe, which formed a synergistic effect of bimetals and changed the content of Ag and Fe and their valence state on the catalyst surface. The findings of H2-TPR indicated that the addition of Ag promoted the shift of the Fe/Al-PILC reduction peak toward low temperature, which boosted the low-temperature reduction capacity of the catalyst. The surface acidity analysis by Py-FTIR indicated that Lewis acid and Brönsted acid existed simultaneously and Ag enhanced the stability of Brönsted acid.