Bimetallic Gold-Palladium Supported on 5A Zeolite and Their Catalytic Activity for Vinyl Acetate Synthesis

5A zeolite supported Gold-Palladium (Au-Pd) bimetallic were prepared and used in vapor phase oxidation of ethylene to synthetize vinyl acetate (VA). The chemical composition of Au-Pd/5A zeolite catalyst was analyzed by a combination of atomic absorption spectrometry (AAS). The structure of Au-Pd/5A zeolite catalyst was characterized by a scanning electron microscopy (SEM) and X-ray diffraction (XRD). The catalytic activity of the Au-Pd/5A zeolite catalyst under laboratory conditions were investigated in vinyl acetate synthesis by a kind of the fixed bed reaction device. The AAS testing showed that Au and Pd supported rate were increased up to the optimum value 91.22% and 93.91% respectively at the ratio of Au/Pd=0.87. The SEM analysis results indicated that Au-Pd alloy particles of 5A zeolite catalyst can grown up and reunited obviously through before and after reaction. The XRD analysis results showed that diffraction peak of Pd(111), Pd(200), Au(111) and Au(200) became sharp gradually with the extension of reaction time, crystalline phase composition and grain size of catalyst became bigger gradually. The results about catalytic activity of the Au-Pd/5A zeolite catalyst shown that with the increasing of the Au/Pd ratio, the space-time yield and selectivity have a best value respectively; when the ratio of Au/Pd=0.87, the space-time yield were 702g/(L.h) and the selectivity were 92.8% at the ratio of Au/Pd =1.13.