Preparation of Au/xCeO2-Al2O3 catalysts with enhanced catalytic properties for the selective acetylene hydrogenation

Abstract

In this work, Au/Al2O3 and Au/xCeO2-Al2O3 catalysts were prepared by incipient wetness impregnation method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), raman spectroscopy, temperature programmed hydrogen reduction (H2-TPR) and temperature programmed NH3 desorption and C2H2 desorption (NH3-TPD, C2H2-TPD). TEM and XRD results showed that there was no obvious difference for the structures and morphologies compared with Au/Al2O3 and Au/xCeO2-Al2O3. However, enhanced catalytic performance was found in the selective acetylene hydrogenation to ethylene. Raman spectra showed that no coke was obtained for Au/xCeO2-Al2O3. NH3-TPD confirmed that with the increase of CeO2 loading, the surface acidity was decreased and an appropriate CeO2 addition was needed for the improvement of catalytic activity. The charge transfer between metallic Au and CeO2 leads to positively charged Au (Auδ+).The basic character of CeO2 and the positively charged Au may play a positive role in the selective acetylene hydrogenation reaction. A possible reaction mechanism was proposed in this paper.