Effect of dealumination on the structure and acidity of H-Y Zeolites

The effect of dealumination using ammonium hexafluorosilicate and steaming has been studied on a series of HY zeolites. The structure of the zeolites after dealumination was studied using XRD, 29Si NMR, 27Al NMR, and IR of the hydroxyl region. The effect of dealumination on the pore structure was investigated using 129Xe NMR experiments. Steam dealumination tends to result in the formation of a highly dispersed extralattice aluminum species within the zeolitic supercage. It is suggested that this extralattice species contributes to enhanced acidity.