Stereoselective hydrogenation of phenyl alkyl acetylenes on pillared clays supported palladium catalysts

The stereospecific hydrogenation of phenyl alkyl acetylenes at 298 K and atmospheric pressure of hydrogen over Pd supported catalysts has been studied. The catalysts were prepared by impregnation Al-PILC and Ca-Mont with Pd(acac)(2) precursor, with metal content close to 1 wt.%. All the solids were characterised by nitrogen adsorption-desorption isotherms at 77 K, TPR, H-2 and CO chemisorption, XRD and TEM measurements. The reactions were found to be zero order concerning the alkyne concentration. At conversion levels up to 80% (reaction time lower than 90 min), only a limited overhydrogenation occurred. It was found that at higher reactant molecule:Pd atom ratios (R:P = 7000), the activity is approximately half of that obtained at lower R:P (R:P = 3500). The results suggested that the hydrogenation of phenyl alkyl acetylenes to cis-alkene is structure insensitive. All catalysts displayed high selectivity to cis-alkene isomer being the 1% Pd/Al-PILC the most active catalyst. (C) 2004 Elsevier B.V. All rights reserved.