Copper-manganese Based Composite Oxide Catalysts For CO Oxidation Reaction

Low-temperature CO oxidation has important practical application value and theoretical research significance.Copper-manganese composite oxides,cheap and easy to obtain,have excellent activity for CO oxidation.It would change the physical chemical properties of the catalysts and the synergistic effect between copper and manganese through adjusting the structure,which can improve catalytic activity for CO oxidation.Based on this,the thesis studied the effect of the modification of the copper-manganese-based composite oxide on the CO oxidation reaction,further,explored its structure-activity relationship.In this thesis,the optimal composition and processing conditions of the catalysts were obtained by researching the preparation conditions of the copper-manganese-based composite oxide.The N₂adsorption-desorption,XRD,H₂-TPR,TEM,CO-TPD and O₂-TPD were used to systematically investigate the structure and the surface characteristics of the catalysts.These catalysts are used for CO oxidation reactions,and how the synergy between copper and manganese species influenced the catalyst activity was investigated.The main experimental contents were listed below:（1）The effects of calcination temperature,catalyst composition,and pretreatment conditions during the catalysts preparation process on the CO oxidation reaction were explored.The catalysts calcined at 450°C had pure structure and exhibited excellent activity for CO oxidation.Thus,the calcination temperature of the subsequent catalysts was 450°C.Changing the Cu/Mn molar ratio was used to obtain catalysts of different compositions.Such as,Cu_1.5Mn_1.5O₄modified with Cu O(namely Cu O-Cu_1.5Mn_1.5O₄)was prepared when the Cu/Mn molar ratio was 2/1;Cu_1.5Mn_1.5O₄was prepared when the Cu/Mn molar ratio was 1.5/1.5;Cu_1.5Mn_1.5O₄modified with Mn₃O₄(namely Mn₃O₄-Cu_1.5Mn_1.5O₄)was prepared when the Cu/Mn molar ratio was1/2.The activity tests manifested that the catalyst Cu O-Cu_1.5Mn_1.5O₄showed the most outstanding behavior for CO oxidation.Reduction pretreatment and reduction-oxidation pretreatment of the copper-manganese composite oxide catalysts both enhanced the activity of CO oxidation reaction.（2）The effect of copper-manganese spinel-type composite oxide catalysts with different composition on the CO oxidation reaction was further explored.For CO oxidation reaction,Cu O-Cu_1.5Mn_1.5O₄performed the highest catalytic activity,which was due to the synergy of Cu O and Cu_1.5Mn_1.5O₄on the surface,which originated from the combination of O₂activated by Cu O and CO activated by Cu_1.5Mn_1.5O₄,resulting in the promotion of the activity.（3）The effect of pretreatment conditions（reduction pretreatment）on the copper-manganese composite oxide catalysts for CO oxidation was further explored.A series of Cu_x/（Mn O）_ycatalysts were prepared by reducing the precursor of the copper-manganese spinel composite oxide.The experimental results revealed that the synergistic effect of Cu and Mn O in the catalysts Cu_x/（Mn O）_yobtained after reduction pretreatment could increase the adsorption of CO and O₂,thereby enhancing its CO catalytic performance.Among them,Cu₁/（Mn O）₂had the best performance because of its largest non-dissociative CO adsorption and chemisorption oxygen content.