Reactant diffusion efficiency plays a critical role in heterogeneous catalytic reactions. In this study, Beta zeolite with a unique needle-like morphology was obtained through a designed cascade of post-synthesis treatments [1].
Experimental
The cascade treatment of HBEA (Si/Al = 12.5, CP814E) was performed with acid treatment and a subsequent alkaline treatment while maintaining the same post-treatment conditions as above. The resulting zeolites were denoted as xMAc-HBEA_AkyD, where x represents the concentration of nitric acid during the acid treatment, and y represents the alkaline treatment days.
Results and Discussion
The needle-like Beta zeolite was prepared via a step-by-step multiple post-treatment process. The XRD patterns demonstrate that, with the extension of alkaline treatment time, the samples continue to exhibit the characteristic Beta zeolite structure and only a slight decrease in intensity. At the same time, the peaks at 2θ = 21.3 and 22.9° were increased after the alkaline treatment, indicating the change in the crystal framework.
The parent Beta zeolites exhibit a morphology of nano-sized aggregates. After 2 days of alkaline treatment, only a tiny amount of needle-like Beta zeolite was present, imparting a sea-urchin-like morphology to the zeolite. As the duration of the alkaline treatment was extended, there was a distinct increase of the needle-like Beta zeolites with a width of around 10 nm. A proposed formation mechanism suggests that isolated silanol nests and cetyltrimethylammonium bromide (CTAB) synergistically contribute to the recrystallization process, leading to the development of the needle-like morphology.
REFERENCE
[1] Y. Liu, T. Yokoi, et.al., ACS Applied Nano Materials, 8 (2025) 1042.