Experimental study on the selective catalytic reduction of NO by C₃H₆ over Cu modified Fe/Al-PILC catalysts

In order to improve the low temperature activity of Fe/Al-PILC catalysts for SCR of NO, copper doping was used for the modification. xCu-Fe/Al-PILC catalysts were prepared by ultrasonic impregnation technique and characterized by XRD, N₂ adsorption-desorption, H₂-TPR, UV-vis, XPS and Py-FTIR. The SCR of NO with C₃H₆ tests were carried out in a fixed bed reactor. The experimental results showed that the xCu-Fe/Al-PILC catalysts can effectively solve the problem of insufficient SCR activity of Fe/Al-PILC catalysts at low temperature and as well as improve the activity at medium and high temperature. High NO reduction efficiency, 80% and beyond could be achieved at a wide temperature range of 200-500℃ by the catalysts, among which 0.13Cu-Fe/Al-PILC exhibited 90% of the NO conversion at 250-500℃ and maximum NO reduction efficiency of 93% at 250℃. XRD and N₂ adsorption-desorption results proved that the catalysts modified by copper provided more active sites and increased the reaction rate. The results of H₂-TPR indicated that the doping of copper improved the catalyst's redox ability at lower temperature, while enhanced the catalyst's redox ability at medium and high temperature. UV-vis and XPS study showed that the doping of copper not only increased the higher oxidation state of iron but also produced more isolated Fe³⁺ which is the low-temperature active species. Py-FTIR test illustrated that Lewis acid and Brönsted acid existed simultaneously on the catalyst surface, and Lewis acid sites were the activity center of the SCR reaction.