CATALYTIC DEHYDRATION OF ISOPROPANOL ON NEODYMIUM-Y AND X-ZEOLITES AND THE EFFECT OF GAMMA-IRRADIATION

Four different samples of NdX, NdY, NdNH4X and NdNH4Y-zeolites were pr epared by ion-exchange methods. DTA and XRD analyses have been carried out for the samples. The thermally activated zeolites were irradiated by 1.5 and 10.0 Mrad gamma-rays. The catalytic activities of these sa mples were tested in dehydration of isopropanol. The results of DTA in dicated that all samples showed endothermic peaks at about 215-degrees -C related to the release of physically adsorbed water and exothermic peaks at 850-950-degrees-C indicating the collapses of the zeolite. Th e X-ray analysis revealed that the exchange of sodium by neodymium or ammonium followed by neodymium ions did not change the crystal structu re but some decrease in the crystallinity was observed. The catalytic activities of these zeolites were measured in dehydration of isopropan ol as a function of temperature. It was found that the activity of the prepared Nd-zeolites depends on the crystallinity of zeolites and on the condensation products formed on catalyst surface. However, the irr adiated samples exhibited higher catalytic activities in isopropanol c onversion than the unirradiated ones. The observed higher activity for irradiated samples was attributed to the increase of the number of ac idic centers responsible for dehydration of alcohols. These centers we re formed as a result of the formation of tricoordinate aluminium atom s in gamma-irradiated zeolites.