Modification of Palladium Catalyst Properties by p-Elements (Sulfur and Phosphorus) in the Direct Synthesis of Hydrogen Peroxide: A Comparative Study.

Abstract

A combination of physical methods is employed to characterize Pd-S and Pd-P catalysts (Pd-nS/NaZSM-5, Pd-nP/NaZSM-5, Pd-nP/HZSM-5) prepared with varying [modifier]:[Pd] ratios using elemental sulfur or phosphorus as modifiers. These catalysts form solid solutions of sulfur or phosphorus in palladium and exhibit similar dispersity. A comparative study is conducted to evaluate the modifying effects of sulfur and phosphorus on the properties of palladium catalysts in the direct synthesis of hydrogen peroxide under mild conditions. The results demonstrate that sulfur incorporation significantly reduces hydrogen conversion while enhancing H₂O₂ selectivity. In contrast, Pd-P catalysts achieve a more balanced activity-selectivity profile and exhibit productivity levels an order of magnitude higher than those of the Pd-0.25S/NaZSM-5 catalyst. These findings provide critical insights for selecting p-elements as modifiers to optimize catalyst performance in hydrogen peroxide synthesis.