III International Conference

PP-II-107Au SUPPORTED ON CeO 2 -ZrO 2 MIXED OXIDES AS THE EFFECTIVECATALYSTS FOR CO OXIDATIONRynkowski J.M., Dobrosz I.Institute of General and Ecological Chemistry, Technical University of Lodz, 90-924 Lodz,Żeromskiego 116, PolandE-mail: jacryn@p.lodz.plCeO 2 -ZrO 2 mixed oxides were found promising supports for Au nanoparticles in COoxidation. Au/Ce 0.75 Zr 0.25 O 2 washed in ammonia presents the highest activity, already at roomtemperature. This study confirms the poisoning effect of the residual chloride on the catalyticperformance of Au/Ce 1-x Zr x O 2 catalysts. The average Au particle size is bigger for thecatalysts containing residual chloride, as confirmed by TEM, SEM-EDS and TOF-SIMS. Theactivity depends on Ce/Zr molar ratio and increases with the increasing reducibility of thesupports and catalysts, as confirmed by TPR. It indicates the role of the support properties,especially reducibility, in the creation of catalytic performance of Au/oxide catalysts.Catalytic oxidation of CO is one of the important reactions due to its relevance inpractical applications such as purification of breathing air in closed spaces, safety masks, gassensors for the detection of trace amounts of CO in air, closed-cycle CO 2 lasers, automotiveexhaust treatments, etc. The possibility of using supported gold nanoparticles as efficientcatalysts for low temperatures reactions has attracted a lot of interest, since the pioneeringwork of Haruta which showed high activity towards CO oxidation with gold deposited onvarious metal oxides (1). Compared to a highly dispersed supported Pt catalysts, Au catalystsare much more active than other noble metal catalysts at temperatures below 130 °C (2).The aim of this work was an attempt to understand the fundamental problems related tothe catalysis on supported Au including the effect of: individual stages of the catalystspreparation, size of Au particles, presence of the residual Cl - on the catalytic performance ofAu/Ce 1-x Zr x O 2 catalysts in CO oxidation. Special attention was paid to the specific role ofsupport, not only as a stabilizer of Au dispersion and modifier of its electronic state but also asa participant in activation of oxygen.CeO 2 -ZrO 2 mixed oxides, CeO 2 and ZrO 2 as a supports for Au were used. CeO 2 -ZrO 2materials possess unique redox properties and high mobility of lattice oxygen, strongly dependanton Ce/Zr molar ratio. Furthermore, ceria is known to be active for the removal of post-combustionpollutants (3). It should be also noted that so far, CeO 2 -ZrO 2 systems widely studied in otherapplications (4), have not been examined as Au supports in the CO oxidation.A series of Ce 1-x Zr x O 2 solid solutions, CeO 2 and ZrO 2 was prepared by sol-gel method,based on a thermal decomposition of mixed propionates and calcined at 550 °C. The catalystswith the nominal Au content 2 wt. % and 5 wt. % supported on Ce 1-x Zr x O 2 (x = 0, 0.25, 0.5,360