Study On Construction Of Composite Metal Active Phases In Pd/ZrO₂ Catalysts For Propane Combustion

In this work,based on the understanding of decoration mechanism of acetylacetone on zirconium hydroxide gel,the protection of capping agent and the extent of metal and support interaction(SMI),we designed a novel nanoengineered method for the preparation of catalysts in which in-situ reduced palladium supported on zironia substrate.It shows no lattice fringes by TEM technique,however,a palladium microdomain about 6 nm on zirconia detected with HAADF-STEM.At the same time,compared with catalysts prepared by conventional impregnation route,the removable oxygen and stronger interaction between the metal and support existed,which investigated systematically by H2,TPR(TPD),XPS and in situ CO-DRIFTS.The results showed that the reducibility of support ZrO2 was enhanced,while the hydrogen desorption amount of PdHx decreased.Besides,with the help of SMI,Pd-O-Zr entities or PdZr alloy might formed within palladium microdomain after reducing treatment.On the other hand,the electronic interactions resulted in electrons transferring from Zr to Pd,and the signal of CO adsorption on catalyst around 1980 cm-1 protruding.Above all,it leaded to high performance for propane oxidation relative to other catalyst.Focused on increasing the catalyst's activity and stability while reducing the amount of noble metal by alloying it with different transition metals,which had comparatively high oxidization property.We prepared catalysts with higher activity by the same route referred above than impregnation sample,for the existed SMI within the microdomian.What's more,we confirmed PdCo alloy had advantage on propane oxidation over PdNi with HEXRD-PDF,resulting from the higher oxidation property of Co.The activity of PdNi alloy supported catalyst was enhanced after aged at high temperature,and the same to toluene oxidation reaction after catalyst reduction within C3H8 atmosphere,due to the modification of support via SMI.Therefore,the mechanism with interaction between nanoalloy and support was useful for improving activity of catalyst.It offered a good way to synthesis heterogeneous catalysts for VOCs complete oxidation.