Praseodymium effects on great improving low-temperature hydrothermal stability of Cu/SAPO-34 NH3-SCR catalysts

Abstract

Based on the previous findings that the presence of hydroxyl groups on the outer surface is crucial for maintaining skeletal stability, we propose a strategy modified Cu/SAPO-34 using Pr ions in this study. Therefore, we conducted several measurements to investigate the effect of Pr ions on the low-temperature hydrothermal stability of Cu/SAPO-34. We find that Pr exists only on the surface of Cu/SAPO-34 as ions and oxides, with Pr ions playing a protective role in occupying surface acidic sites. The addition of small amounts of Pr leads to the re-dispersion of Cu, resulting in improved low-temperature selective catalytic reduction (SCR) activity in the as-synthesized samples. Furthermore, it enhances the resistance to decomposition of the Si–(OH)–Al framework during low-temperature hydrothermal aging, thereby preserving the framework structure and allowing detached active Cu species to return to exchangeable positions, ultimately restoring SCR activity. However, as the Pr content increases, the enhanced acidity causes some structural damage, gradually weakening the protective effect. Our work demonstrates that Pr modification is a simple and effective solution to the issue of poor low-temperature hydrothermal stability in Cu/SAPO-34, providing a promising way for the application of light rare earth elements.