Preparation, Characterization And The Application Of CeO₂-Co₃O₄ Catalyst In Low-temperature CO Catalytic Oxidation

The process of low-temperature CO catalytic oxidation has become an important research topic due to its many potential areas of applications. Particularly, these applications include air-purification devices for respiratory protection, carbon monoxide gas sensors, closed-cycle carbon dioxide lasers, and removing trace quantities of CO from the ambient air in sealed cabins. In addition, in the aspect of academic study the CO oxidation has been regarded as a probe reaction to show the relationship between the structure and the performance, and also to investigate the reaction mechanism.The research about the base metal oxide Co₃O₄ catalyst for low-temperature CO catalytic oxidation has become a hotspot over the years. Although showing very high catalytic activity, the Co₃O₄ catalyst has many defects, such as the problems of stability and water resistance. The preparation, characterization and the catalytic performance of CeO₂-Co₃O₄ catalysts for low-temperature CO catalytic oxidation have been studied in dissertation. Firstly, the effect of the preparation method such as impregnation,precipitation and sol-gel, on the catalytic performance have been studied; secondly, the effect of doping CeO₂ by impregnation on structure and catalytic performance of Co₃O₄ catalyst have been studied, the catalysts have been characterized by XRD, N₂-adsorption, TEM, TPR, FT-IR, by compared the structure exchange of catalyst with or without CeO₂ and the result of water resistance evaluation, the possible reason for the excellent water resistance of the CeO₂-Co₃O₄ catalyst has been given. The main results and conclusions are as follows:1. By investigation the impregnation, co-precipitation, sol-gel method, CeO₂-Co₃O₄ catalyst with 5 wt% CeO₂ prepared by impregnation has the lowest initiation temperature, and the highest catalytic activity.2. By investigation the effect of different calcined temperature on CeO₂-Co₃O₄ with 5 wt% CeO₂, prepared by impregnation, the catalyst calcined at 400℃has the highest catalytic activity. With the calcined temperatue increasing, the activity decreases, especially when the catalyst calcined at 800℃,the catalytic activity decreases remarkablely and the initiation temperature is 100℃.3. Investigation the effect of CeO₂ doping on structure and catalytic performance of Co₃O₄ catalyst for low-temperature CO oxidation. Combined with many chracterization methods, the possible reason of the better catalytic activity,stability and excellent water resistance of CeO₂-Co₃O₄ catalyst after doping CeO₂ have been given.(1) At room temperature, the CeO₂-Co₃O₄ catalyst has the better catalytic stability and activity, compared with the single component Co₃O₄ catalyst, while the pure CeO₂ catalyst has much lower catalytic performance.(2) From the investigation of water resistance, at room temperature, the Co₃O₄ and CeO₂-Co₃O₄ catalyst have low catalytic stability and can only maintain CO complete conversion for 20 min; when the reaction temperature rising to 110℃, the CeO₂-Co₃O₄ catalyst can maintain CO complete conversion at lease 8400 min, showing excellent water resistance, while the Co₃O₄ catalyst can only maintain CO complete conversion 100 min. The pure CeO₂ catalyst has very low activity.(3)Characterization by XRD,TEM,N₂-adsorbtion,TPR,FT-IR, the CeO₂-Co₃O₄ catalyst possesses smaller particles, larger surface area and there is the interaction between CeO₂ and Co₃O₄ in the catalyst due to the doping of CeO₂. all of these characteristic can contribute to the better catalytic activity,stability and excellent water resistance. Moreover, the detection of H₂ in the reactor outlet gas seems to show that the water-gas shift reaction occurs in the reaction, but there is no H₂ detected under the single Co₃O₄ catalyst. This result shows the doping of CeO₂ induces the water-gas shift reaction, and this reaction is possible to be the more directive reason for the excellent water resistance of the CeO₂-Co₃O₄ catalyst.