Study On Pd-base Membranes For The Direct Synthesis Of Hydrogen Peroxide From Hydrogen And Oxygen

γ-Al2O3 coating was coated on the surface of theα-Al2O3 ceramic tube to prepareγ-Al2O3 modified ceramic support which was used to prepare membrane catalysis, then Pd-Ag bimetallic membrane catalysts which contains 25% Ag, 50%Ag and 75% respectively, and Pd-Ag-Pt, Pd-Ag-Au trimetallic membrane catalysts were prepared on the surface of ceramic tubes modified byγ-Al2O3 coating. For the more, the modified supports and membrane catalysts were characterized by SEM, XRD, SEM-EDS, BET. Finally, the direct synthesis of hydrogen peroxide from hydrogen and oxygen was carried out in a membrane reactor in order to study the effects of the modification of supports and the membrane composition on the reaction.Theγ-Al2O3 coating on theα-Al2O3 ceramic tube was prepared by sol-gel method. The results show that the uniform and defect-freeγ-Al2O3 coating can be prepared by this method. After coating three times, the thickness ofγ-Al2O3 coating is about 10μm, specific surface area is 279.3831 m2/g.Three types of Pd-Ag bimetallic membrane catalysts which contain 25%Ag, 50%Ag and 75%Ag were prepared by the electroless plating technique. The thickness of membrane is about 13μm and the transition section formed between the support and membrane is about 12μm. Catalytic activity and selectivity of Pd-Ag membrane could be enhanced by modification withγ-Al2O3 coating. The concentration of H2O2 and selectivity to H2O2 were effective enhanced by the addition of halide into reaction media. The surface morphology and catalytic activity of Pd-Ag membranes are influenced by the amounts of Ag. The more Ag in the membranes, the better catalytic activity it has.The Pd-Ag-Pt, Pd-Ag-Au trimetallic membrane catalysts were prepared by the electroless plating technique. The thickness of membrane is about 10μm. The reaction results show that the concentration of hydrogen peroxide over Pd-Ag-Pt trimetallic membrane is higher than that over Pd-Ag bimetallic membrane with 75% Ag. Pd-Ag-Au membrane gave the low conversion of hydrogen and selectivity to hydrogen peroxide compared to Pd-Ag-Pt membrane.