(63d) Selective Catalytic Oxidation of Co in the Presence of Hydrogen over Au/Mno2-Ceo2 Catalysts

Supported gold catalyst has been a subject of intense investigation since the report of its exceptionally high CO oxidation activity at low-temperature and high selective oxidation of CO in hydrogen stream (PROX). For fuel cell system,proton exchange membrane fuel cells (PEMFC), a critical issue is to feed carbon monoxide free hydrogen to the anode. Therefore, removal of CO in H2 stream is an important subject in fuel cell performance. The catalyst should have the high activity to oxidize CO without oxidizing H2.It has been reported that Au/CeO2 catalyst has high CO conversion but low selectivity to oxidation of CO, and Au/MnO2 has low CO conversion but high selectivity to oxidize CO.The aim of this study was to investigate the effect of adding MnO2 in Au/CeO2 catalyst on PROX reaction,and to develop a catalyst which has the advantages of single oxide-supported catalyst. In this study, nanosized gold supported on CeO2, MnO2 and MnO2-CeO2 binary oxide were prepared by deposition-precipitation method. The catalytic properties of Au/MnO2-CeO2 were investigated for CO oxidation in H2 stream. The catalysts were characterized by powder X-ray diffraction, N2 sorption, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis. The results showed that gold particles prepared in this study were less than 4 nm. XPS showed that gold were in electron-deficient state. The presence of MnO2 increased the concentration of metallic gold species. The results of PROX reaction showed that the CO conversion of all samples increased with increasing reaction temperature ,whereas the selectivity to CO oxidation decreased with the increasing reaction temperature. For gold on single oxide-support, Au/CeO2 exhibited a much higher CO conversion than Au/MnO2. However, the selectivity of Au/CeO2 decreased with reaction temperature significantly than Au/MnO2. By regulating the preparation and pretreatment procedure and the compositions of Au/MnO2-CeO2 catalyst, we have developed a Au/MnO2-CeO2 catalyst demonstrating excellent performance on both CO conversion and selectivity to CO oxidation at 353 K. This catalyst was also very stable after 3000 h time on stream.