Influence of the Nature of Medium Modifiers on the Properties of Palladium–Phosphorus Catalysts in Direct Synthesis of Hydrogen Peroxide

The influence of the nature and concentration of a medium modifier (Brønsted acid, halide) on the yield of H₂O₂ in direct synthesis under mild conditions was studied using two samples of Pd–P catalysts supported on ZSM-5 zeolite in the H and Na forms. The acid modifier and the halide have opposite effects on the yield of H₂O₂. Unlike HCl, potassium chloride has an inhibitory effect on the catalyst activity, partially suppressing the formation of H₂O₂. Based on the experimental data, a hypothesis was formulated about the diverse nature of the active sites responsible for H₂O₂ formation in direct synthesis and H₂O₂ hydrogenation. The main functions of the acid modifier in direct synthesis under the action of the Pd–P catalysts are considered.