CS-133 AND NA-23 MAS NMR-STUDIES OF ZEOLITE-X CONTAINING CESIUM

The local structures around cesium and sodium in the zeolites X contai ning cesium in excess of the ion-exchange capacity (cesium-added zeoli te X) were examined by Cs-133 and Na-23 MAS NMR to elucidate the locat ion of the added cesium and the formation of the basic sites caused by addition of the excess cesium. The cesium species located in the intr acrystalline cavities of zeolite and those on the outer surface of zeo lite crystallites were distinguished by a combination of Cs-133 and Na -23 MAS NMR data. The excess cesium species are located in the superca ges for the samples containing an excess of 1.1 and 2.9 cesium atoms p er supercage, whereas for the samples containing 5.1 and 9.8 cesium at oms per supercage, parts of the cesium species are on the outer surfac e of the zeolite crystallites. The cesium-added zeolites which contain cesium species in the supercages and possess a high surface area exhi bit high activities for 1-butene isomerization. (C) 1997 Elsevier Scie nce B.V.