Boosting low-temperature and high-temperature hydrothermal stability of Cu/SAPO-34 for NO removal via yttrium decoration

Cu/SAPO-34 SCR catalysts have been widely investigated for NOx removal in past decades. However, the inferior hydrothermal stability of these catalysts greatly limited their industrial application. In this work, Cu/SAPO-34 docorated by yttrium (Y) were synthesized and the effects of Y on the low-temperature (L-T, 70 °C) and high-temperature (H-T, 850 °C) hydrothermal stability of Cu-SAPO-34 as well as the mechanisms were systematically studied at atomic-level. The results showed that Y imbedding slightly enhanced L-T hydrothermal stability but significantly improved H-T one of Cu-SAPO-34. Typically, even suffering from H-T hydrothermal aging at 850 °C for 10 h at 10 vol.%H2O, the Y modified Cu-SAPO-34 (Cu/Y-S-850) still presented relatively higher NOx conversion (80–100 %) at a wide temperature window of 225–450 °C than the reference one (Cu/S-850) (<40 %), which is superior to those of most reported CHA-based SCR catalysts. This promotion could be due to the fact that Y decoration can minimize the broken of Si-O-Al bonds and inhibit the collapse of the zeolite skeleton, which in turn kept an intact CHA structure and helped active Cu2+ species disperse well, thus exposing abundant active Cu2+ component during harsh aging. Additionally, numerous Brønsted and Lewis acid sites over the Y modified catalysts were almost maintained. From this way, NOx was adsorbed, activated, and conversed smoothly via both “L-H” and “E-R” mechanisms.