ADSORPTIVE PROPERTIES AND STABILITY OF VPI-5, A LARGE-PORE MOLECULAR-SIEVE

The unusual adsorptive properties and the reported instability of VPI-5 have been investigated in some detail. The VPI-5 framework was found to undergo an irreversible but incomplete phase transformation to AlPO4-8 during the removal of the zeolitic water. Furthermore, ill-defined constrictions are believed to be introduced into the framework during the course of this transformation. These have a great effect on the resulting adsorptive properties of dehydrated VPI-5. The adsorptive properties of the dehydrated material are dependent on factors such as the outgassing conditions, the sample history, the concentration of intracrystalline P-OH and other defect sites and the method of sample synthesis.