Hydrotalcite-supported palladium catalysts Part I: Preparation, characterization of hydrotalcites and palladium on uncalcined hydrotalcites for CO chemisorption and phenol hydrogenation

Hydrotalcites (HTs) are prepared by low supersaturation and high supersatur ation methods, containing CO32-, Cl-, SO42- interlayer anions and with diff erent Al(III)/Al(III)+Mg(II) (x=0.33 and 0.25) ratios. Palladium hydrotalci te catalysts are obtained by impregnation of PdCl2 aqueous solution on HTs. Different precursors of palladium are used for loading the metal onto HT p repared at high supersaturation. HT and palladium HTs are well characterize d by XRD, surface area, IR, SEM, DTA. CO chemisorption is used to estimate palladium dispersion and metal area. The activity is evaluated for phenol h ydrogenation reaction. The selectivity to cyclohexanone is always greater t han or equal to 90% even though phenol conversion varies with metal area. ( C) 1998 Elsevier Science B.V. All rights reserved.