Ultrasonic-assisted synthesis of highly active catalyst Au/MnOx–CeO2 used for the preferential oxidation of CO in H2-rich stream

A series of nano-gold catalysts supported on binary oxides MOx–CeO2 (atomic ratio M/Ce = 1:1, M = Mn, Fe, Co, Ni) are prepared by deposition–precipitation (DP). An innovative and rather convenient ultrasonic pretreatment of the support is employed for Au/MnOx–CeO2 preparation. It is found that for preferential CO oxidation Au/MnOx–CeO2 is more active than Au/CeO2. Ultrasonic pretreatment of MnOx–CeO2 further promotes the performance of Au/MnOx–CeO2, with CO conversion increased by 24 % at 120 °C. Meanwhile, the selectivity of oxygen to CO2 is promoted in the whole temperature range, especially in 80–120 °C, the selectivity is increased by 15–21%. HR-TEM and XRD results indicate that ultrasonic pretreatment is favorable to the formation of much smaller gold nanoparticles (<5 nm). The characterization of XPS, UV–vis DRS, H2-TPR and CO-TPR confirms that the strong interaction between Au and the support effectively inhibits the dissociation and oxidation of H2 over the ultrasonically pretreated catalyst Au/MnOx–CeO2, making it highly selective to CO oxidation.