Towards understanding mesopore formation in zeolite Y crystals using alkaline additives via in situ small-angle X-ray scattering

The formation of micro/mesoporous zeolites by treating zeolite crystals with alkaline hydroxides has received a lot of interest, but fundamental understanding is still lacking. Here, we study the reactivity of a crystalline zeolitic material with various alkaline hydroxides, to close this knowledge gap. The use of ex situ and in situ small-angle X-ray scattering has allowed us to determine the reactivity of faujasite (FAU) type zeolite Y at different pH and Si/Al ratio (SAR), with a variety of different organic ammonium hydroxides. Supplemented with ex situ XRD and BET isotherm measurements, we show that the pH of the starting mixture and SAR of the zeolite significantly influence the stability of the microporous structure and the extent of formation of mesoporous material.