Amine groups functionalized gel-type resin supported Pd catalysts: Physicochemical and catalytic properties in hydrogenation of alkynes

Palladium catalysts (0.125-0.5wt.% Pd) supported by amine groups-functionalized gel-type resin (FCN) were studied in the hydrogenation of alkynes reagents, 2-butyne-1,4-diol and phenyl acetylene. The catalysts were prepared by two routes. The first, OAc is based on the immobilization of Pd-precursor in the pre-swollen resin from THF solution of Pd(OAc)(2), followed by chemical reduction of the Pd-centers. This method produces Pd particles of size in nano-scale. The second procedure, aq implies the deposition of Pd-species on dry resin beads using aqueous solution of PdCl2. Reduction of these Pd-species gives relatively large Pd particles, dominating are 30-50 nm in size. The SEM studies performed over the cross-section of catalysts grains showed location of Pd in outer shell of polymer beads in both OAc and aq catalysts; however, thinner layer of I'd appears in aq series catalysts. In the presence of all catalysts, prepared by OAc and aq methods the selectivity towards alkenes is high, above 90%. The catalysts of aq series are much more active and more selective than OAc analogues giving selectivity to alkene ca. 94% at almost complete conversion of alkynes. Moreover, catalytic performance of aq' series catalyst is unchanged under recycling use. The catalyst was recovered and reused 4 times, maintaining its catalytic efficiency. (C) 2008 Elsevier B.V. All rights reserved.