Formation and the nature of activity of Ziegler systems based on palladium β-diketonate complexes in hydrogenation catalysis

The catalytic properties and nature of Ziegler-type Pd(Acac)₂ and Pd(Acac)₂PPh₃ based catalysts are studied in the hydrogenation of unsaturated compounds. The causes of an extremum appearing in the dependence of the specific activity of the catalyst in styrene and phenylacetylene hydrogenation on the proportions of the starting components are considered. The increase in the specific activity of the Pd(Acac)₂ + AlEt₃ catalytic system in hydrogenation as a function of the Al/Pd ratio arises from an increase in the degree of dispersion of the microheterogeneous system, an increase in the fraction of reduced palladium, and changes in the nature of the ligand shell. The inhibiting effect is caused by triethylaluminum adsorption on palladium nanoparticles. Palladium nanoparticle models are suggested.