Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes

Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P-SiO2) were prepared via a one-pot methodology. The series of P-SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4-2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P-SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.

Automated summary

In this study, Pd, Cu, and PdCu nanocatalysts stabilized by triphenylphosphine were prepared and supported on carbon nanotubes or phosphorus functionalized silica. The catalysts exhibited differences in reactivity in the semi-hydrogenation of alkynes, which could be correlated with the size and composition of the metallic nanoparticles and the nature of the support. Carbon-supported catalysts generally showed higher activities than silica-supported catalysts, with the bimetallic PdCu/CNTs catalyst being the most selective for alkyl substituted alkynes. This catalyst also showed good recyclability without loss of activity or selectivity.