Preparation of Organophilic Pd–Montmorillonite, An Efficient Catalyst in Alkyne Semihydrogenation

Palladium particles incorporated into organophilic montmorillonite (Pd–M) were prepared via a novel synthetic method, mediated by a cationic surfactant stabilizer. The materials were characterized by UV–Vis, ICP-AES, and TEM. Two representative samples (Pd–M1 and Pd–M2), with metal contents of 0.1% and 0.46%, respectively, were investigated in detail. TEM measurements indicated that the diameters of the Pd particles observed were in the range 1.5–6 nm. It is suggested that most of the Pd particles are situated on the external surface of the clay lamellae. Both Pd–M samples exhibited marked catalytic activities and stereoselectivities in the liquid-phase hydrogenation of 1-phenyl-1-butyne. For the production of the cis-alkene stereoisomer, Pd–M2 proved to be less active but more stereoselective than Pd–M1. The stereoselectivities obtained for Pd–M2 in n-hexane (86–88%) were nearly as high as those experienced for the Lindlar catalyst.