An insight into the process involved in hydrothermal conversion of FAU to *BEA zeolite

The use of FAU zeolite as a starting material was found to enhance the crystallization rate of *BEA zeolite, suggesting that the dissolution of FAU zeolite provides locally ordered aluminosilicate species that assemble and evolve into *BEA zeolite. Here we show experimental findings that indicate the presence of such locally ordered aluminosilicate species in intermediate phases involved in the hydrothermal conversion of FAU zeolite into *BEA zeolite. On the basis of the previous fact that cetyltrimethylammonium (CTA(+)) cations seem to be able to preserve zeolitic fragments or seeds and retain them in the mesoporous framework, this method was applied to the characterization of the obtained intermediate phases. From the detailed characterization of mesoporous products, the different characteristics were found to be observed between intermediate phases. Namely, as the more disordered arrangement was found in the mesoporous products, the presence of evolved, locally ordered aluminosilicate species was strongly indicated.