CYCLOHEXANE OXIDATION OVER RARE-EARTH EXCHANGED ZEOLITE-Y

Rare earth exchanged zeolites Y (REY) were prepared from HY with Si:Al ratios of 2.6, 12.5 and 28 by solid-state ion exchange with CeCl3, Nd Cl3, SmCl3, EuCl3 or YbCl3. The resulting REY were used as catalysts f or the liquid-phase oxidation of cyclohexane with tert-butyl hydropero xide. Cyclohexene, n-hexanal, cyclohexanone and cyclohexanol are the p rincipal products formed. The activity of the catalysts depends on the Si:Al ratio: 12.5 > 2.6 > 28, on the rare earth cations: Ce much grea ter than Yb > Sm > Eu > Nd, and on the temperature. Using CeY with a S i:AI ratio of 12.5, at 50, 70 and 90 degrees C, cyclohexane conversion s of 4.7, 7.3 and 10% and turnover numbers of 236, 366 and 505, respec tively, are observed after 24 h. However, at 90 degrees C large amount s of carboxylic acids are formed. Leaching experiments with CeY show t hat most of the products are formed in a heterogeneously catalysed rea ction. (C) 1998 Elsevier Science B.V. All rights reserved.