Temperature-efficiency Relationship And Degradable Performance Of Microwave-assisted Catalytic Combustion Of Toluene

Volatile Organic Compounds（VOCs）,as one of the main pollutants in the atmosphere,not only have serious harm to human health,but also are the precursors of PM_2.5.5 and O₃ which can aggravate the haze weather.In addition,VOCs can induce photochemical smog under sunlight irradiation and cause secondary pollution.At present,combustion method,regenerative thermal oxidizer and absorption-adsorption method are the major control techniques of VOCs treatment,but these technologies all have the problems of high cost and limited application scope.In recent years,catalytic oxidation technology has become a research hotspot on VOCs control because of its low light-off temperature,wide application range and complete degradation efficiency.However,the traditional electric heating method that are used in the technology has some shortcomings,such as the slow speed of temperature rise and fall,uneven heating and easy sintering of catalysts.Microwave heating,instead of electric heating,can effectively solve these problems while combined with catalytic oxidation,and shows the removl of pollutants more economically and effectively.In this study,Cu-Mn-Ce/cordierite honeycomb catalyst was prepared by incipient impregnation and then applied to treat gaseous toluene through a fixed bed under microwave heating.The catalytic activity and stability of the catalyst were investigated,and the temperature of the fixed bed was tested and analyzed.The microtopography,specific surface area,grain size and crystal phase structure of the catalyst were analyzed by means of SEM,XRD and BET.Based on the experimental research,the following research results were obtained:（1）The optimum reaction temperature is between 200℃and 300℃under different inlet conditions.The residence time of the bed is an important factor affecting the removal efficiency of toluene.When the bed residence time is more than 4⁷ s,the degradation rate of toluene can reach more than 80%.When the microwave power is 2kW,catalyst dosage is 40 L（weight 23.7 kg）,the volume flow is 40 m³/h and the toluene concentration is 3000 mg/m³,the removal rate of toluene can reach 70%by microwave-assisted catalytic combustion.（2）When the oxidation reaction of toluene is stable,the temperature of the catalyst bed increases gradually from 240℃to 380℃along the inlet side to the outlet side.And the temperature distribution on the cross section that is perpendicular to the airflow direction is slightly higher in the middle and lower on both sides,and the temperature difference is within 50℃.（3）The spinel single metallic oxide and the spinel composite metallic oxides of Cu-Mn-Ce are the main active components in the catalyst,and the catalytic combustion of toluene follows the pseudo-first order kinetics.The influence of high temperature on the structure of the catalyst is not obvious,Eight-time repeated tests have confirmed that the catalyst has high activity and good structural stability.（4）The pilot-scale study of microwave-assisted catalytic combustion technology on the spot has proved that it can be applied to treat industrial organic waste gas,but there are still some technical problems that needs to be further resolved and improved.The researches in the study have laid a theoretical foundation for the microwave-assisted catalytic combustion technology and carried out a beneficial exploration and practice for further real application of the technology.