P-31, AL-27, XE-129 NMR-STUDY OF PHOSPHORUS-IMPREGNATED HZSM-5 ZEOLITE CATALYSTS

Phosphorus-impregnated HZSM-5 zeolite has been characterized by 31P and 27Al magic angle spinning NMR and 129Xe NMR spectroscopy. All the NMR data clearly indicate that the phosphorus compound reacts initially with the framework aluminum, modifying the chemical environment of the internal zeolite surface. Excessive impregnation of phosphorus did not change the physicochemical environment of the channel any further, as the chemical shift in 129Xe NMR indicated. This reaction of the phosphorus compound with the framework aluminum is responsible for changes in the adsorption and catalysis of the zeolite. © 1990.