Ultra-stable Pd ions at Al T1/T2 sites on a dealuminated Pd/beta passive NOx adsorber
CATALYSIS SCIENCE & TECHNOLOGY(2023)
摘要
Pd ions as NO adsorbing sites on zeolites for PNA materials showed evident deactivation when exposed to reducing agents or treated under hydrothermal conditions. In this study, stable Pd2+ species are mainly obtained by loading palladium on a dealuminated beta zeolite, and can survive during cyclic evaluations with reducing agents and hydrothermal treatment at 850 degrees C. On the dealuminated beta zeolite, a large amount of framework Al T1/T2 is reserved by design. CO-DRIFTS and H-2-TPR results reveal that [Pd-OH] and isolated Pd(iso)(b) are mainly present on the dealuminated beta zeolite and are quite stable because of their higher energy. These [Pd-OH]/Pd(iso)(b) on the dealuminated beta zeolite contribute stable NOx storage performance. Al-27 MAS NMR suggests that the Al T1/T2 sites of PDB-F are more stable and the [Pd-OH]/Pd(iso)(b) simultaneously protects the occupied Al T1/T2 sites from being destroyed. NH3-TPD shows that [Pd-OH]/Pd(iso)(b) on the dealuminated beta zeolite contributes a more stable acid concentration after cycle evaluation or hydrothermal aging. Thus, the dealuminated Pd/beta materials, with ultra-stable Pd2+ species, can meet real exhaust conditions.
更多查看译文
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要