SOLID-STATE NMR-STUDY OF ULTRASTABLE ZEOLITE-Y MODIFIED WITH ORTHOPHOSPHORIC ACID

Si-29, Al-27 and P-31 solid-state NMR under magic-angle spinning was u sed for the study of ultrastable zeolite Y modified with H3PO4. The ma terial is a potential candidate for a new generation of oil-cracking c atalysts. Bloch decay and cross-polarization spectra were compared. It was found that amorphous aluminium phosphate is formed during the P-i mpregnation and the following activation, and that it occupies the zeo lite surface and internal voids. For a high P-content under steaming c onditions, aluminium phosphate is converted into a crystalline form. N o evidence has been found for incorporation of P atoms into the zeolit e framework.