Preparation, Characterization And Catalytic Applications Of Highly Dispersed Au And Ru Catalysts

Strong metal-support interaction (SMSI) has a great influence on the size and morphology of noble metal nanoparticles, as well as their catalytic activities. Study on the SMSI has always been a hot topic in the field of catalysis in order to prepare highly dispersed supported noble metal nanoparticles with high activity. Supported Au and Ru nanoparticles were active for the catalytic reactions, such as CO oxidation (preferential oxidation of CO), N2O decomposition and CO2methanation. However, the nanoparticles were easily aggregated during the synthesis, and showed a lower selectivity or became inactive due to the aggregation during the reaction. Herein, we investigated the influence of supports on the metal particle size and morphology, and their catalytic performances in specific catalytic reactions.The LaAlO3-Al2O3s composite support, prepared by La-doped Al2O3, had brought an enhanced strong interaction between the support and Au nanoparticles. Thus a highly dispersed gold catalyst was obtained on this support. Compared with Au/Al2O3catalyst, the strength of CO adsorption on Au/LaAlO3-Al2O3catalyst was significantly improved while the reaction rate of H2oxidation was greatly decreased. So, the Au/LaAlO3-Al203catalyst showed a wide temperature range of CO100%conversion (50-100℃). In addition, the catalyst also exhibited a good stability during the reaction.We employed a rutile-type TiO2(r-TiO2) as a support for preparing Ru catalyst. The prepared Ru/r-TiO2catalyst was much more active and stable in CO2methanation than the anatase-type TiO2(a-TiO2) supported Ru catalysts. The results showed that r-TiO2could effectively prevent the aggregation of RuO2during calcining in air. The average particle size of Ru nanoparticles supported on a-TiO2was4.0±2.4nm, but Ru/r-TiO2catalyst presented a much narrower particle size distribution (1.1±0.2nm). The XAFS and H2-TPR results indicated that this unique property of Ru/r-TiO2catalysts was contributed to the strong interaction between r-TiO2and RuO2by forming the Ru-O-Ti bond. To great extent, this kind of strong interaction not only highly promotes the dispersion of Ru nanoparticles but also prevents the Ru from sintering during the reaction.In order to prevent the aggregation of RuO2at high temperatures under the oxidative atmosphere, the uniformly coated RuO2thin film on r-TiO2were prepared based on the high degree of lattice match between them. Compared with other supported RuO2catalyst, the RuO2/r-TiO2catalyst exhibited a much higher catalytic activity in N2O decomposition. A series of characterization results, such as XRD, HRTEM, Raman and XPS, confirmed that the formation of Ru-O-Ti bond at the interface of r-TiO2and RuO2produced a strong interaction between them and prevented the aggregation of RuO2particles.