Nature of cerium on improving low-temperature hydrothermal stability of SAPO-34

Abstract

To probe the function of Ce on enhancing low-temperature stability of SAPO-34, Ce/SAPO-34 with different Ce contents was prepared via one-pot method and further treated at 70 °C in 80% relative humidity for 24 h. The structural results prove that the one-pot synthesis is an effective way to introduce Ce (Ce < 0.325 wt%) without influencing micro-structural and chemical composition. The low-temperature hydrothermal stability of Ce/SAPO-34 is enhanced by Ce loading. More than 92% CHA structure and total acidity are maintained over 0.188 wt% Ce/SAPO-34, while only about 20% of that left on pure H/SAPO-34. As Ce exists as Ce3+ at exchange sites on the surface of SAPO-34, the results of the linear relationship between protected surface acidity and structure/acidity conservation manifest that Ce3+ effectively hinders the structural collapse. This study provides new insight into surface acidity protection for solving the problem of low-temperature hydrothermal stability of SAPO-34.