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.