MESOPOROUS ALUMINOSILICATES PREPARED FROM ZEOLITES BY TREATMENT WITH AMMONIUM FLUOROSILICATE

The pore enlargement upon treatment of various A- and X-type zeolites with ammonium hexafluorosilicate (AFS), is strongly dependent on the Si : Al ratio and the preparation conditions (volumes of the AFS solution added and the ammonium acetate solution used). In particular, the higher the Si : Al ratio, the lower the average size of the mesopores for the resulting materials. The use of the buffer is necessary for sharp pore-size distributions. The materials thus obtained show very interesting ion-exchange capacities which may exhibit values up to 80% of the initial value.