H₂O₂ synthesis by selective oxidation of H₂ over Pd-Au bimetallic nano colloid catalyst under addition of NaBr and H₃PO₄

Effects of additives on H₂O₂ formation rate and yield were studied to prevent H₂O₂ decomposition and it was found that high yield and the formation rate of H₂O₂ can be obtained by using NaBr-H₃PO₄ additives in spite of much smaller amount compared to NaCl-H₂SO₄ system,. Since Br^- adsorbed strongly on Pd-Au nano colloid surface, relatively high formation rate of H₂O₂ was attained at 298 K. Therefore, from industrial point of view, addition of NaBr (2 mM) and H₃PO₄ (0.5 mM) to reaction media for H₂O₂ direct synthesis, was highly beneficial. However, the H₂O₂ accumulation experiment, it was found that the H₂O₂ became negligibly small after 20 h and the decomposition of formed H₂O₂ became dominant reaction after 40 h. Deactivation of catalyst seems to be related with the decrease in Br^- concentration, surface segregation of Pd and particle size growth. After 25 h, H₂O₂ concentration was reached a value of 5.8 wt% at 298 K.