Microstructure Constructed And Catalytic Performances Of Cobalt Based Catalysts

Co₃O₄ of AB₂O₄-type spinel structure exhibits activities as high as that of noble metals in many catalytic reactions.Researches did show that the enhanced activity of Co₃O₄ could be attributed to its high redox ability since there was much more mobile lattice oxygen and resulted active oxygen species such as O^-and O^2-.However,under high temperature conditions,Co₃O₄ is prone to sintering and structural recombination,resulting in a sharp decrease in catalyst activity and stability.Therefore,it’s an urgent and significant challenge to improve the sintering resistance of Co₃O₄-based catalysts which is critical for high stability and industrial application.In this work,Co₃O₄ material with high index（311）crystal facet selectively exposed,small particle size and large specific surface area was synthesized by simple chemical precipitation in which a small amount of glycerol was used as a structure-directing agent.The catalyst exhibits high activity in propane catalytic combustion which achieves 100%propane conversion at 210°C.The much lower complete conversion temperature（vs.270℃for Co₃O₄ prepared by normal method）avoids the sintering of catalyst at high temperatures and further increase the catalytic activity and stability.The Co₃O₄ coated with cobalt aluminate film was successfully prepared by the rational control of the inert cobalt aluminate generated at high temperature（T≥800℃）.In the following treatment with a reducing atmosphere,the cobalt aluminate film was destroyed,so that the Co₃O₄active component was re-exposed to obtain a high temperature stable supported Co₃O₄ catalyst.The catalyst calcined at 800°C and then reduced at 500°C could achieve 100%propane conversion at 280°C.The cerium-zirconium-aluminum solid solution supported on a Co₃O₄catalyst was further developed.The generated cobalt aluminate at interface firmly fixes the Co₃O₄ on the surface of the carrier and maintains a high dispersion of Co₃O₄.Cerium and zirconium provides active oxygen and promotes the high activity of Co₃O₄.After high temperature treatment at800℃,the 10%Co-Ce₁Zr₁Al₁ catalyst still has a good activity,with a light-off temperature of 230℃in propane catalytic combustion reaction.In this thesis,Co₃O₄ with high index crystal facet was synthesized with the assistance of structure directing agent under mild conditions using.The anti-sintering supported Co₃O₄ catalyst at high temperatures was prepared by rational regulation the strong interaction between the active component and the support.The obtained cobalt-based catalysts have high activity and stability,which is of great significance for promoting their industrialization.Meanwhile,this thesis provides a new idea for efficient and stable catalysts design and preparation.