Effect of rhodium precursor and thermal treatment on the hydrogenation of 2-cyclohexenone on Rh/SiO2 Catalysts

The hydrogenation of 2-cyclohexenone in Liquid phase was studied at 298 K o n Rh/SiO2 catalysts. The kinetic parameters found were: zero order for the ketone and first order for the hydrogen. The hydrogenation of the C=C doubl e bond was affected by the carbonyl group, i.e., the C=O function of the un saturated ketone anchors on the metal surface thus increasing the residence time of the molecule on the substrate. In catalysts prepared either with R hCl3. 3H(2)O or with Rh-acetylacetonate, the reaction was found to be 'stru cture-insensitive'. A precursor effect was observed: the chlorinated cataly sts showed higher activity than the non chlorinated ones. Notable enhanceme nt of the activity per site was observed when the Rh catalysts were thermal ly treated under hydrogen + water vapor at high temperature. The enhancemen t in activity was related to the formation of 'weakly' adsorbed hydrogen on the metal surface. (C) 1999 Elsevier Science B.V. All rights reserved.