Preparation Of Monolithic Molecular Sieve-based Catalysts And Study On Microwave Catalytic Combustion Of VOCs

With the development of social industrialization,the emission of volatile organic compounds(VOCs)continues to rise,and the resulting air pollution problem is also becoming more and more serious.VOCs are mostly toxic and accompanied by an irritating odor.They are the culprit or important precursor of atmospheric pollution such as photochemical smog,ozone,PM2.5 and the greenhouse effect,and can harm human health.Microwave catalytic combustion as a new technology for VOCs treatment has the advantages of mild reaction conditions,high degradation and mineralization efficiency,reasonable equipment investment and reasonable operating costs,and is favored by researchers and enterprises.The catalyst is the core of the catalytic combustion technology,and the development of a strong wave absorbing and high activity catalyst will help the efficient microwave catalytic combustion degradation of VOCs.In the experiment,a monolithic honeycomb molecular sieve was used as a carrier to prepare a copper-manganese-cerium supported catalyst.The catalytic performance and stability of multi-component VOCs(toluene,acetone and ethyl acetate)under microwave heating were investigated.Factors and the stability of the catalyst,and the bed temperature distribution characteristics were analyzed.The morphology,specific surface area,grain size and crystal structure of the monolithic catalyst were tested and analyzed by SEM,XRD,BET and other characterization methods.Based on the experimental research,the following research results are obtained:(1)The honeycomb molecular sieve carrier has a good ability of absorbing itself,and it heats up faster in the microwave field.The heating performance of the loaded molecular sieve carrier is significantly better than that of the molecular sieve carrier before loading.The specific surface area of the molecular sieve carrier forms a high temperature hot spot on the catalyst surface,thereby improving the overall wave absorbing performance of the catalyst and facilitating the catalytic degradation of pollutants;(2)The prepared Cu-Mn-Ce/molecular sieve honeycomb catalyst has high treatment efficiency for low and medium concentration VOCs waste gas under microwave heating.When the bed temperature exceeds 300?and the air volume is5m~3/h,the catalyst's degradation efficiency of VOCs gas with a concentration between200-2000 mg/m~3 is between 96%and 80%;(3)Temperature is a prerequisite for oxidative degradation of VOCs.After the bed temperature exceeds 300?,the effect of temperature on the degradation efficiency is no longer significant.The change of air volume,that is,residence time,has a more significant effect on degradation efficiency.The temperature in the catalytic reaction chamber shows a distribution of high in the middle and low in the periphery due to the influence of the structure.Therefore,strengthening the insulation of the chamber wall of the reaction chamber is beneficial to improve the efficiency of catalytic degradation;(4)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 VOCs follows the pseudo-first order kinetics.The influence of high temperature on the structure of the catalyst is not obvious,Six-time repeated tests have confirmed that the catalyst has high activity and good structural stability.The research in the study has 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.