Role of phosphorus in the formation of selective palladium catalysts for hydrogenation of alkylanthraquinones

Effective Pd-P catalysts for the hydrogenation of 2-ethyl-9,10-anthraquinone in a toluene/1-octanol medium were obtained. Phosphorus modification increases the selectivity of the active quinones from 69% to 93%-97%, and the deposition of Pd-P catalyst particles on a carbon support increases their activity fivefold due to increased dispersion without a decrease in selectivity to the target product. Using energy dispersive X-ray spectroscopy, X-ray powder diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, the composition, size and state of the surface layers of Pd-P catalysts were determined. Surface enrichment by the electron-deficient palladium and structural disorder of Pd-P catalyst particles were shown to account for the increase in selectivity to active quinones during hydrogen peroxide production by the anthraquinone method.