Role of CeO2 in Three-Component Au/CeO2/SiO2 Composite Catalyst for Low-Temperature CO Oxidation

Hierarchical composite nanostructure composed of Au, CeO2, and SiO2 was fabricated by sequentially depositing ceria nanoparticles through impregnation and calcination, and then gold nanoparticles through a deposition-precipitation method on hierarchical monolithic silica (HMS) with multi-length scale pore structure. The Au/CeO2/HMS composite nanostructure was characterized by X-ray diffraction, temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy. The results indicate that the presence of ceria had a significant effect on targeted deposition and stabilization of small metallic gold nanoparticles on the support. The temperature for complete conversion of CO to CO2 over Au/CeO2/HMS is ca. 60°C at a space velocity of 80000 ml/(g·h). The highly dispersed metallic gold nanoparticles can activate CO and the small ceria nanoparticles supply oxygen in the reaction. The catalytic activity remains considerably stable during 48 h stability testing. The interaction between gold and ceria contributed greatly to CO oxidation and the presence of silica improved the stability of the gold catalyst.

摘要采用具有分等级孔道结构的 SiO2 (HMS) 为载体, 通过润湿浸渍引入少量 CeO2, 经焙烧得到 CeO2/HMS 复合载体, 然后采用沉积沉淀法负载上 Au 纳米粒子, 得到 Au/CeO2/HMS 三元复合催化剂. 通过 X 射线衍射、程序升温还原和原位红外光谱等手段表征了催化剂的结构. 结果表明, CeO2 的存在可控制 Au 颗粒的沉积并稳定载体上的纳米 Au 颗粒. Au/CeO2/HMS 上 CO 低温氧化反应完全转化温度为 60 °C. 高度分散的 Au0 可以活化 CO, CeO2 颗粒则可以提供反应需要的氧. 稳定性测试结果显示, 反应 48 h 催化剂活性维持不变.

Hierarchical composite nanostructures composed of Au, CeO2, and SiO2 were fabricated by sequentially depositing ceria nanoparticles through impregnation and calcination and then gold nanoparticles through deposition-precipitation on hierarchical monolithic silica (HMS). The presence of ceria had a significant effect on controlled on target deposition and the stabilization of small metallic gold nanoparticles on the support.Figure optionsDownload as PowerPoint slide