Characterization of the amorphous phases formed during the synthesis of microporous material AlPO4-5

We have used several solid-state NMR techniques in conjunction with powder X-ray diffraction (XRD) and Raman spectroscopy to characterize the structure of the intermediate amorphous phases of AlPO 4 -5 molecular sieve synthesis. The evolution of the gel phases as a function of crystallization time was followed by 31 P and 27 Al magic-angle spinning (MAS) NMR to obtain information on the local environments of Al and P atoms and by powder XRD to detect the long-range ordering of the gel samples. We have utilized 27 Al/ 31 P double-resonance techniques such as heteronuclear correlation spectroscopy (HETCOR) to select the 31 P–O– 27 Al bonding connectivities and transfer of populations by double-resonance (TRAPDOR) to obtain information regarding the degree of condensation for P sites in the amorphous phases. The 1 H → 31 P cross-polarization (CP) was used to identify the P sites with hydroxyl groups attached. Raman spectroscopy was also employed to follow the evaluation of the pore system. The 13 C CP MAS spectra provide information regarding the chemical environment of template molecule in the gel. The work shows that a combination of the above-mentioned techniques can provide more detailed information on the structure of amorphous phases formed during hydrothermal synthesis.