Supported palladium nanomaterials as catalysts for petroleum chemistry: 1. Specifics of palladium diacetate reduction with hydrogen on silica gel in catalyst synthesis

The reduction reaction of Pd(II) diacetate, a precursor in nanocatalyst synthesis, with molecular hydrogen on silica gel has been studied. A kinetic model involving the autocatalytic mechanism of Pd(II) reduction to Pd(0) and adequately describing the experimental data has been proposed. Similarities and dissimilarities in the mechanism of this process on silica gel and carbon have been revealed. On the basis of quantum-chemical simulation data, it has been suggested that the differences are due to both a high bond energy of the precursor with the support and modifications in geometry of various Pd(II) diacetate species adsorbed on the surface. The controllable reduction of the precursor makes it possible to manufacture materials with a metal particle size of 1.7–2.8 nm according to transmission electron microscopy data. The materials catalyze the reaction of phenylacetylene hydrogenation to styrene with a high activity and selectivity at 25°C and 1 atm of hydrogen.