Research On Improving The Firmness Of Honeycomb Cordierite-based Catalysts And Microwave Catalytic Combustion Of VOCs

Volatile Organic Compounds?VOCs?have a great toxic effect on the atmosphere and human health.Microwave catalytic combustion as a new technology for VOCs treatment that owning mild reaction conditions,high degradation and mineralization efficiency,reasonable equipment investment and operation cost and other advantages has been favored by the researchers in the environmental field.The catalyst is the core of the catalytic combustion technology.At present,the active components on the surface of the catalyst that prepared by the equal volume impregnation method,is easy to fall off from the carrier due to some factors such as the erosion of the air flow during longtime operation,high temperature reaction condition,and catalyst loading and unloading,etc.The shedding affects the activity and stability of the catalyst to a certain extent and would greatly reduce the service life of the catalyst.In view of the problem that the active components of the monolithic catalyst is easy to fall off,this paper uses different acid-base solutions to pre-treat the honeycomb cordierite?CH?carrier under two conditions of normal temperature and high temperature,and improves the firmness of active components on the carrier by adding a variety of additives.The firmness of the adhesion is investigated by microwave catalytic combustion of typical VOCs-toluene and the actual VOCs exhaust gas of the enterprise to check the absorbing performance,catalytic activity,mineralization performance and stability of the catalyst.Simultaneously,SEM,BET,XRD and other characterization analysis for the high firmness catalyst were carried out.Based on the experimental research work,the following results are obtained:?1?At normal temperature,the carrier was subjected to acid etching treatment with10%hydrochloric acid.When m_{silica sol}/m_{water absorption}=0.125,the catalyst could obtain the best firmness,and the active components shedding rate?0.0165%?was far lower than the control group catalyst?0.950%?,m_{pseudo boehmite}/m_{water absorption}=0.12 also had a low shedding rate?0.0258%?,the addition of additives increased the firmness of the active components load to some degrees.?2?The active components had excellent microwave-absorbing properties.Compared with Cu-Mn-Ce?pseudo boehmite?/CH catalyst,Cu-Mn-Ce?silica sol?/CH catalyst had higher catalytic activity and lower temperature activity.Under the conditions of intake air concentration 1000mg/m³,intake air volume 0.12m³/h,microwave power 200W and bed temperature 350?,the microwave catalytic combustion degradation rate and mineralization rate of gaseous toluene were 98.9%and87.9%,respectively.Under continuous experiment of 43h,the catalyst activity remained stably,and the active components shedding rate?0.0328%?was lower than that of the control group catalyst?0.363%?.?3?Combined with the catalyst characterization test,it was confirmed that the addition of silica sol resulted in a high dispersion of active components and enhanced the physical force between the active components and the carrier.The resulting siloxane chemical bond greatly improved the adhesion of the active components.Thereby prolonging the service life of the catalyst,more spinel active materials and copper-manganese solid solution on the surface of the catalyst ensured the activity and stability of the catalyst.?4?The high firmness catalyst was applied to the on-site pilot test of the enterprise,and it was found that when the light-off temperature was reached,the heat released by the combustion reaction could be used as the heat source to maintain the temperature of the catalyst bed.The bed temperature is the decisive factor that affects the activity of the catalyst,the T₉₀ of the actual multi-component VOCs exhaust gas was about 450°C.The catalyst volume is 0.33m³,When the intake air volume is increased from 440m³/h to982m³/h,the VOCs can still maintain a degradation rate of more than 90%.The research of the thesis has made effective attempts to enhance the loading strategy of microwave thermal catalyst,and applied it to the field of catalytic combustion of VOCs,the catalytic degradation and mineralization effect is good,which has laid a certain theoretical foundation for the preparation of high-activity and long-life catalysts,and provided technical support for further pilot tests and subsequent applied research.