Selective semi-hydrogenation of phenyl acetylene by Pd nanocatalysts encapsulated into dendrimer networks

Abstract

A series of heterogeneous catalysts, based on Pd nanoparticles encapsulated into the networks, obtained from poly(propylene imine) (PPI) dendrimers, has been synthesized. Dendritic networks were designed using bi- and ter-functional coupling agents of various size, rigidity and polarity, influencing the catalyst morphology and hydrogenation activity. The catalysts obtained have demonstrated significant increase in selectivity on styrene in comparison with traditional Lindlard catalyst, maintaining at prolonged reaction time and quantitative conversions achieved. A positive dendritic effect was revealed when passing from dendrimers of the 1st generation in the carrier to those of the 3rd generation. The best results were obtained for the catalyst, synthesized using 3,3′-dimethoxy-4,4′-diphenyl diisocyanate in the presence of polymeric template (the selectivity of 90–95% at conversion of 98–100% and surface turnover frequency, TOFs, of 160–300 s−1). The same catalyst has demonstrated the best stability at recycling.