xAu/α-MnO2催化剂的结构及催化氧化VOCs气体性能

以NaOH为沉淀剂,采用沉积-沉淀法制备了α-MnO2负载Au催化剂xAu/α-MnO2(x=1.0%～7.0%,质量分数),利用X射线衍射(XRD)、N2吸附-脱附、H2程序升温还原(H2-TPR)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等技术对所得样品进行了表征,并对其催化氧化挥发性有机化合物(VOCs,苯和甲苯)的性能进行了研究.XRD结果表明,负载Au对α-MnO2载体结构影响不大,但对其晶粒大小和比表面积略有影响.随着Au含量的增加,α-MnO2结晶度增强,颗粒增大,Au粒径明显增大.XPS结果表明,随着Au负载量的增加,xAu/α-MnO2的晶格氧(O2-),Mn4+和Au3+的浓度增加.H2-TPR结果表明,由于贵金属的溢氢作用,Au明显提升了xAu/α-MnO2的还原能力,其中3%Au/α-MnO2的还原能力最强.负载Au明显影响xAu/α-MnO2的催化性能,xAu/α-MnO2的催化性能与Au的颗粒分散性、低温还原性能及表面氧物种密切相关,其中3%Au/α-MnO2显示出最佳活性,其催化氧化苯和甲苯的T100分别为280和250℃.

xAu/α-MnO2 Catalysts: Structure and Catalytic Oxidation of Benzene and Toluene

α-MnO2-supported gold catalysts(xAu/α-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), N2 adsorption-desorption measurement, H2 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 α-MnO2 support were related with the Au loading over xAu/α-MnO2 samples and increased with Au loading. The result of XPS showed that the molar ratios of O2-/O2-, Mn4+/Mn3+ and Au3+/Au0 increase with adding of Au. It was shown that the loading of gold on α-MnO2 could significantly modify the catalytic activities. The catalytic performance of xAu/α-MnO2 strongly depended upon the Au loading, among which 3% Au/α-MnO2 performed the best activity, T100=280, 250 ℃ for the catalytic oxidation of benzene and toluene, respectively. The excellent performance of 3% Au/α-MnO2 was associated with the highly dispersed Au, good low-temperature reducibility, and synergism at the interface of Au and MnO2 nanodomains.