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