xAu/α-MnO2 catalysts: Structure and catalytic oxidation of benzene and toluene

alpha-MnO2-supported gold catalysts(xAu/alpha-MnO2, x = 1. 0% -7. 0%, mass fraction) were prepared by deposition-precipitation method using NaOH as precipitation agent and characterized by X-ray diffraction (XRD), N-2 adsorption-desorption measurement, H-2 temperature-programmed reduction(TPR), Transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy (XPS). Catalytic activities of the materials were evaluated for the oxidation of benzene and toluene. The sizes of Au particle and alpha-MnO2 support were related with the Au loading over xAu/alpha-MnO2 samples and increased with Au loading. The result of XPS showed that the molar ratios of O2-/O-2(-), Mn4+/Mn3+ and Au3+/Au-0 increase with adding of Au. It was shown that the loading of gold on alpha-MnO2 could significantly modify the catalytic activities. The catalytic performance of xAu/alpha-MnO2 strongly depended upon the Au loading, among which 3%Au/alpha-MnO2 performed the best activity, T-100 = 280, 250 degrees C for the catalytic oxidation of benzene and toluene, respectively. The excellent performance of 3%Au/alpha-MnO2 was associated with the highly dispersed Au, good low-temperature reducibility, and synergism at the interface of Au and MnO2 nanodomains.