DES-induced Synthesis Of Cu-Mn-C-O Composite Catalyst And Its Catalytic Oxidation Of Methane

Ventilation air methane is difficult to be effectively used due to its low concentration（0.1～1vol%）,large emissions,and low calorfic value.As a typical catalys for catalyzing oxidation of methane,the oxides of Cu Mn₂O₄ has the advantages of low initiation temperature,excellent electron mobility and redox ability.However,the disadvantages of the oxides of Cu Mn₂O₄ are as follow,low proportion of high-valence metals,high burning temperature and insufficient high temperature activity.The main purpose of this paper is to synthesis high-performance Cu-Mn-C-O composite catalyst by deep eutectic solvents（DES）hydrothermally to achieve the control of catalyst structure components.1)The Cu Mn₂O₄ induced precursor,CM,was prepared by the co-precipitation method.Trough DES hydrothermal induvtion,A series of Cu-Mn-C-O composite catalysts were successfully prepared by hydrothermal induction of CM precursor using DES hydrothermal induction.Both the hydrothermal conditions and the amount of DES would affect the crystal growth of the catalyst.What the optimal induction conditions are 180℃,4 h,and 0.5 g the addition of DES.The crystal growth and the catalytic activity of the catalyst of methane were greatly enhanced,in which T_50%and T_90%values were 365℃and 425℃,respectively.2)The Cu-Mn-C-O composite catalysts were successfully induced and synthesized by the DES under the optimal induction conditions.Its catalytic performance was significantly better than the CM-induced precursor.The temperature of T_90%had dropped by 175℃.The Mn CO₃ was the main phase in composite catalysts,in which there were a small amount of Cu_1.5Mn_1.5O₄ phase,and had a rich pore structure.The generation of the new phase changed the number and distribution of acid-base sites on the catalyst surface,effectively improving the desorption of catalytic reaction products.Simultaneously,the internal electronic structure of the composite catalyst system had also undergone major changes.The high proportion of high-valence manganese and a large numble of absorbed oxygen species were conduction to methane oxidation at lower temperature.The stability test of the composite catalysts were carried out,and the catalytic performance remained above 90%after 100 h of catalytic reaction.3)The thermal analysis of Cu-Mn-C-O composite catalyst and Mn CO₃ catalyst were carried out.Through combustion kinetic calculations,it was found that the combustion mechanism of Cu-Mn-C-O composite catalyst was mainly the random nucleation and subsequent growth mechanism,while the combustion mechanism of the Mn CO₃ sample was mainly three-dimensional diffusion mechanism.The most important thing was that the activation energy of the composite catalyst was significantly higher than that of the Mn CO₃ material,indicating that the energy required to destroy the Cu-Mn-C-O composite catalyst structure during the combustion process was higher than the Mn CO₃ sample structure.In sum,the stability of Cu-Mn-C-O composite catalyst was higher than Mn CO₃catalyst during combustion.