Studies On The Complete Oxidation Of Low-Carbon Oxygenates Over CeO₂-Supported Cu And Pt Catalysts

Low-carbon oxygenates such as alcohols and ethers have been regarded aspromising alternative fuels due to its high energetic density, much less pollutants andlow price. CeO2-supported catalysts have been the subjects of intensive researchesbecause of their unique catalytic performances in various applications. Thesignificant promoting effect of ceria is generally attributed to its high oxygen storagecapacity and facile Ce⁴⁺/Ce³⁺ redox cycle. In this dissertation, the oxidation ofoxygenates and CO over CeO₂-supported catalysts was explored, and the relationshipbetween catalytic performance and structure was investigated. In addition, thecatalytic activities of Pt-Sn/CeO₂ catalysts for the complete oxidation of ethanol weremeasured.The catalytic activity of CuO/CeO₂ catalysts strongly depends on preparation routeand metal loading. The changes of the degree of interaction can strongly affect theredox properties of supported copper catalysts, producing significant differences incatalytic performance for CO oxidation reaction. A strong reduction temperaturedependence of copper chemical states in the as-prepared CuO/CeO₂ catalyst wasobserved. A sequential change in copper states (Cu²⁺ →Cu⁰ →Cu⁺) occurs duringreduction with hydrogen through gradually increasing the reduction temperatures.Especially, Cu⁺ can stably exist as the dominant copper species after reductiontreatment with hydrogen at 500℃. A reaction pathway in CuO/CeO₂ system for COwas proposed involving surface reaction at the copper-CeO₂ interface.The activity and stability of the Pt/CeO2 prepared by modified polyol method aresuperior to that of the Pt/CeO2 prepared by HCHO liquid phase reduction, suggestingthe different metal-support interaction and distribution of Pt species play crucial rolesin governing the catalytic performance. The particle size of Pt as well as the Pt-ceriainteraction during the preparation process is controlled by the nucleation and thegrowth rates which depend on the reducing ability and solvent effect of differentagents. The modification of electronic configuration of Pt by Sn and theinteraction of Pt and Sn modify the nature of the active sitescontributing to the improvement of catalytic performances for thecomplete oxidation of ethanol. The separate SnO2 phase would cover activePt sites and impede ethanol chemisorption, suggesting that excess tincan decrease the catalytic performance of Pt-Sn/CeO2 catalyst. Thisresult shows important value of applications for exhaust control ofethanol gasoline and DEFCs。.