Multinucleax solid-state NMR was employed to study the silicon-substitutedmolecular sieve Si-VPI-5. 29Si and 27Al NMR suggest that Si can be incorporated intothe framework of VPI-5 and the substitution of two silicon atoms for an aluminium atomplus a phosphorus atom is predominant. Such substitution is limited in a certain domainof the crystal and "silicon rich" regions are thus generated. 1H MAS spectra reveal that asmall arnount of silicon atoms substitute phosphorus only and SiOHAl groups are formed,which provides the acidic source for the molecular sieves. Si-VPI-5 prepared with silicagel as the silicon source exhibits a higher content of SiOHAl groups than that preparedwith (EtO)4Si.
The relaxation properties of water saturated in porous core are discussed and the dis-tribution of proton transverse relaxation time and bi-exponential model of longitudiual relaxationtime are obtained, which provide an illustration for two-model of fluids saturated in porous media.The cutoff value of T1 based ou relaxation specific property of fluids in porous core is adopted toimprove the correlation between permeability
