XE-129 NMR-STUDIES ON LANAY ZEOLITES WITH VARIOUS LANTHANUM CONTENTS

The location of cations in LaNaY zeolites with various lanthanum conte nts (from 1.5 to 18.7 La ions/u. c.) has been studied by Xe-129 NMR te chnique. It is found that all LaNaY samples pretreated at 350 degrees C in vacuum, even with low lanthanum content, have some lanthanum cati ons remaining in supercages, and the amount of cations in supercages d epends on the total content of lanthanum in zeolites, When the lanthan um content exceeds 8 La ions/u. c., couples of lanthanum cations appea r in sodalites (beta cages), and irreversibly form bridging lanthanum oxide or oxyhydroxide species at temperature 350 degrees C, but below this content, the reaction doesn't occur, and lanthanum cations locate d in different sodalites, respectively, Usually, Na+ cations in Y zeol ite as a whole are considered as being independent of the chemical shi ft of Xe atoms, but according to our result of Xe-129 NMR, the unlocat ed Na+ cations in supercage have an interaction with Xe and affect the chemical shift of xenon.