POSITIONS OF CATIONS AND MOLECULES IN ZEOLITES WITH FAUJASITE-TYPE FRAMEWORK .V. LA-EXCHANGED TYPE X ZEOLITE AT 25 425 AND 735 DEGREES C

La-exchanged Type X zeolite activated at 500° and 600° shows three OH infra-red bands which are not completely removed even after vacuum activation at 730°C. At room temperature, the La atoms occupy sites I′, II and V. At 425 and 735°C in a helium stream the La atoms occupy sites I, I′ and II. The simplest interpretation is that La atoms tend to occupy sites I and II when X zeolite is strictly dehydrated and dehydroxylated, and that they prefer site I′ when some residual molecules are available for bonding. © 1969.