Preparation Of Copper-manganese Catalysts Based On High-gravity Technology And Its Catalytic Combustion Performance Of Toluene

Volatile organic compounds（VOCs）are a typical atmospheric pollutant and an important precursor to the formation of PM_2.5 and O₃.They can cause environmental problems such as acid rain,photochemical smog,haze,ozone pollution,and the greenhouse effect,posing serious threats to human health and natural ecology.In recent years,China has formulated a series of VOCs-related emission standards and control policies,raising higher requirements for VOCs management.The 20th National Congress report mentioned the need to continuously promote the prevention and control of volatile organic compounds to improve the ecological environment.Catalytic combustion technology has been widely used in VOCs management due to its high efficiency,wide applicability,and no secondary pollution.The key to this technology is the development of efficient,low combustion temperature catalysts.Copper-manganese catalysts have advantages such as strong bimetallic synergistic effect,good stability,and low cost,making them a research hotspot in the field of VOCs catalytic combustion catalysts.Liquid-phase coprecipitation has become the main preparation process of copper-manganese catalysts due to its controllable conditions,simple process,and low cost.However,in this process,the magnetic stirrer only causes disturbance in a local area,resulting in poor liquid-liquid phase mixing and a wide particle size distribution of the prepared catalysts,as well as uneven Cu-Mn element distribution,which limits the industrial application of copper-manganese catalysts.The impinging stream-rotating packed bed（IS-RPB）is a high-gravity reactor with excellent liquid-liquid micromixing and mass transfer capabilities,and has been widely researched and applied in the field of nano-catalyst preparation.With the continuous development of high-gravity technology,IS-RPB has gradually become a highly efficient,low energy consumption,stable,and continuous process intensification device.In this study,copper-manganese catalysts were prepared using IS-RPB as a reactor combined with coprecipitation for VOCs catalytic combustion,and the effects of copper-manganese molar ratio,IS-RPB operating parameters,and calcination temperature on catalytic combustion performance of toluene were investigated.The optimal preparation conditions of copper-manganese catalysts using IS-RPB were determined to be:copper-manganese molar ratio of 1:2,initial impact velocity u=5.31m/s,high-gravity factorβ=105.81,and calcination temperature of 500°C.Under these conditions,the average particle size of the prepared copper-manganese catalysts was 160nm with a uniform particle size distribution,mainly ranging from140nm to 220nm.The catalyst exhibited the best catalytic combustion performance(T₉₀=216°C),which is comparable to that of precious metal catalysts,showing a good catalytic activity.Compared with the traditional liquid-phase precipitation method,the T₉₀ of the prepared copper-manganese catalysts was reduced by 9°C,which is mainly attributed to the stronger Cu/Mn synergistic effect providing more active oxygen and improving catalytic activity.Through a series of characterizations,it was found that the IS-RPB reactor can make the Cu²⁺and Mn²⁺in the coprecipitation reaction more uniformly distributed at the microscopic level,resulting in a more uniform Cu-Mn element distribution and stronger Cu-Mn bimetallic synergistic effect in the prepared copper-manganese catalysts.The application performance of the prepared copper-manganese catalysts by high-gravity method was studied.The results showed that the T₉₀ of the copper-manganese catalysts prepared by high-gravity method for catalytic combustion of toluene at a space velocity of 18000-54000 m L/g/h was 216°C-248°C,exhibiting good catalytic performance.After 40 hours of catalytic combustion of toluene at245°C,the catalyst still had a removal rate of over 90%for 1000 ppm toluene,demonstrating good stability.Kinetic studies found that the rate constant of catalytic combustion of toluene by copper-manganese catalysts prepared by high-gravity method was 0.0716s^-1,which was higher than the rate constant of 0.0144s^-1 for catalytic combustion of toluene by copper-manganese catalysts prepared by magnetic stirrer,indicating that the copper-manganese catalysts prepared by high-gravity method had a faster catalytic combustion rate of toluene.In this study,low-temperature,efficient,and inexpensive VOCs catalysts were successfully prepared by enhancing the liquid-liquid phase micromixing and mass transfer efficiency in the coprecipitation process using IS-RPB.This not only further expands the application of IS-RPB in the field of nano-catalyst material preparation but also lays a theoretical and practical foundation for the industrial production of copper-manganese catalysts.