Design And Fabrication Of Microwave Set-up And Its Application In Catalytic Oxidation Of Gaseous Toluene

Volatile organic compounds（VOCs）as the precursors of PM_2.5.5 and photochemical smog,poses a serious threat to personal health.Therefore,VOCs treatment becomes an urgent task for government and researchers.Catalytic oxidation technology is simple,highly efficient and easy to control,which can effectively accelerate the oxidation of pollutants by using catalyst.Microwave heating has the advantages of selectivity,fast start-up and uniform heating.Therefore,the combination of catalytic oxidation and microwave heating could have a bright prospective for the treatment of VOCs.Because of the advantages of low cost and simple reaction,electrodeless UV lamp under microwave irradiation has been highly concerned and developed gradually.Therefore,the research of microwave-assisted catalytic oxidation and microwave electrodeless UV lamp on the oxidation of gaseous toluene should have a significant guideline for the treatment of VOCs.In this study,copper-manganese-cerium（Cu-Mn-Ce）composite metallic oxides was loaded on the surface of honeycomb silicon carbide（SiC）carrier as a catalyst that was prepared by the incipient impregnation method.A pilot-scale experimental setup that can be magnified controllably was designed and fabricated to be used in the process of both microwave catalytic oxidation and photodegradation of microwave electrodeless UV lamp.As one typical representative of VOCs,toluene is selected as the target pollutant to be used in the research work to check the catalytic activity of the catalyst and photodegradation efficiency of microwave electrodeless UV lamp.The temperature-rising curves of SiC carrier and Cu-Mn-Ce/SiC catalyst under microwave irradiation were investigated.The degradation of toluene in the process of microwave-assisted catalytic oxidation was checked under different reaction conditions,and the mineralization rate of toluene and the stability of the catalyst were both analyzed in this research.The degradation of toluene by microwave electrodeless low-pressure mercury lamp as UV source was studied.The catalyst was characterized by SEM,XRD and BET respectively.The research results were summarized and listed as below.（1）Design and fabrication of microwave setup:In consideration of the adoption of honeycomb monolithic catalyst and the treatment of high flow,the reactor was designed and calculated in view of the maximum airflow during reaction,and a combined pilot-scale experimental setup was fabricated with up-flow gas inlet and outlet tubes,microwave sources in both two sides,electrodeless lamp and catalytic chamber in the middle of the reactor.（2）The microwave-absorbing ability and temperature-rising property of the catalyst were improved after loaded Cu-Mn-Ce active components,which could be due to a strong microwave-absorbing performance of transition metallic oxides that accelerating the transformation of microwave energy to heat energy.（3）The degradation rate and mineralization rate of toluene by microwave-assisted catalytic oxidation reached 98%and 78%respectively at 240℃approximately of reaction temperature.After 30 hours of continuous reaction,the degradation efficiency of toluene by Cu-Mn-Ce/SiC catalyst was still higher than 90%.（4）In the process of photodegradation by microwave electrodeless UV lamp,the degradation efficiency and mineralization rate of toluene were higher than 37%and24%,respectively.（5）It was showed that by SEM and XRD characterizations that the specific surface area of the catalyst was increased,and the adsorption capacity and temperature-rising ability were both improved apparently after loading Cu-Mn-Ce active components onto the surface of the catalyst.The active components loaded were spinel species of multi-metallic oxides that enhancing the adsorption of toluene on the catalysts’surface to ensure the high activity of the catalyst.The paper studies the effect of microwave-assisted catalytic oxidation and microwave electrodeless UV lamp on toluene degradation.The large-volume monolithic SiC carrier is used to prepare Cu-Mn-Ce/SiC honeycomb catalyst and the catalytic activity is tested in the oxidation and mineralization of toluene with a high flow rate,which will provide a solid theoretical foundation for VOCs treatment by microwave electrodeless UV lamp and thermal catalytic oxidation technology and further pilot-scale research work.