Preparation Of Mn-Based Catalyst And Its Performance In Catalytic Combustion Of Toluene Exhaust

Volatile organic compounds(VOCs)have a wide range of sources and complex types,which are the main sources of air pollution.They can result in serious air pollution such as photo-chemical smog,ozone layer destruction,and cause an adverse effect on human's health.Catalytic combustion is one of the most commonly used methods for the treatment of VOCs because of its advantages of low energy consumption,high efficiency and no secondary pollution.The core of catalytic combustion method is the catalyst,which can be divided into noble metal catalyst and non-noble metal catalyst according to different active components.Although the noble metal catalyst has the advantages,such as low ignition temperature and good catalytic activity,the high price limits its industrial application.Therefore,the development of catalysts with low price,good catalytic activity and good stability has become a research hotspot in the field of VOCs treatment.In this paper,copper-manganese composite oxide catalysts with different ratio of copper and manganese(1:1,1:2,1:4)were prepared by impregnation and hydrothermal methods respectively,and their catalytic performance for toluene oxidation was investigated.The structure and performance of the catalysts were analyzed by means of XRD and H2-TPR.The experimental results show that:(1)When the ratio of copper to manganese is 1:2,the catalyst prepared by impregnation method has the best catalytic performance.When the inlet concentration of toluene is 1000 ppm,the space velocity is 10000 h-1,and the reaction temperature is 282?,the toluene can be completely converted.The sequence of activity is Cu1Mn2>Cu1Mn1>Cu1Mn4.XRD shows that with the increase of the proportion of copper and manganese,the diffraction peak of Mn3O4 appears.H2-TPR shows that the reduction peak of catalyst shifts to high temperature with the increase of Cu/Mn ratio.A 48 h stability test result illustrates that the catalysts have good thermal stability.(2)The catalyst prepared by hydrothermal method has the best catalytic performance when the ratio of copper and manganese is 1:2.When the inlet concentration of toluene is 1000 ppm,the space velocity is 10000 h-1,and the reaction temperature is 250?,toluene can be completely converted.The sequence of activity is Cu1Mn2>Cu1Mn1>Cu1Mn4.XRD shows that there are a few diffraction peaks of MnCO3 in Cu1Mn2 and Cu1Mn4,and H2-TPR result is consistent with the activity.A 48 h stability test result illustrates that the catalysts have poor thermal stability.(3)The catalyst with the best catalytic activity was chosen to burn toluene under the same experimental conditions.The results show that the catalyst prepared by hydrothermal method has better catalytic performance.(4)The kinetic studies of all the catalysts prepared by the two preparation methods illustrate that the kinetic data is consistent with the catalytic activity.The better the catalytic activity of the catalyst,the greater the reaction activation energy and the pre-finger factor.The results indicate that the catalyst activation energy is sensitive to temperature,and the size of the pre-factor is closely related to the catalytic activity.