Title : On the structural changes of zeolite Y upon interaction with Alumina binder
Abstract:
Zeolite Y is one of the most important solid acid catalysts that find immense applications in catalytic processes such as fluid catalytic cracking (FCC), acylation and cumene cracking. The technical grades of FCC catalysts require specifications that are met by dispersing the zeolite in amorphous binders. On contact with binders, zeolite properties in composite catalyst alter. This paper discusses the structural modification of Y zeolites caused by alumina binder incorporation. Experiments employing solid state MAS-NMR, N2 adsorption and FTIR techniques reveal alumina incorporation reorganizes zeolite framework in comparison of silica binder. USY and REY are more susceptible to the attack by alumina as binder due to polarization of the framework by extra-framework species (such as Al3+ and Al(OH)2 +), which is considered to be the operating mechanism for framework distortion by migration of aluminum atoms from the binder to the framework of zeolite and its subsequent framework structure reorientation. Compensating framework Na+ cations restrain the polarization of NaY framework. However, polarizability of the zeolite’s framework by extra-framework alumina species is independent of the exchanged cations (RE3+ or H+). The resulting catalyst is amorphizised by layers of alumina that implicates the Brönsted acidity as a function of its weight in the catalyst.
