Synthesis of hierarchical micro/mesoporous Y-zeolites by pseudomorphic transformation

The study focused on the synthesis of hierarchical Y zeolites by the pseudomorphic transformation of binder containing DAY zeolite cylinders. The transformation was carried out in dependence on the transformation time and the hydroxide concentration in the reaction mixture. While the transformed materials showed no typical MCM-41 structures after short transformation times, the variation of the hydroxide concentration resulted in micro/mesoporous composites with a high quality of the MCM-41 phase. Hierarchical materials with a flexible ratio between the volumes of the micro- and mesopores could be prepared via the second route. Even pure MCM-41 extrudates were synthesized on the basis of the starting zeolite. The samples were characterized by nitrogen physisorption, X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), transmission electron microscopy (TEM) and break resistance measurements. The DAY cylinders remained intact after a complete transformation of the zeolite phase.