Performance Of Chlorobenzene Catalytic Oxidation By Birnessite Modified By Metalion

Chlorobenzene organic pollutants are persistent organic pollutants being widely found in industrial flue gas and chemical production,which cause great damage to the environment and pose a serious threat to human health.The catalytic oxidation technology can completely degrade CBs into small molecules,such as CO2 and HCl,under relatively mild conditions,which is the treatment technology with great potential for industrial waste gas purification.In this paper,chlorobenzene is the aiming pollutants,and layered manganese,?-MnO2,with specific structure as precursor,and then modificate layered manganese by metal U(Un+ = Co2+,Cu2+,Fe3+,Al3+,Ce3+)to made U doped-8-MnO2,abbreviated U/Mn.Next optimize the preparation of catalysts.Then systematically investigate the U/Mn catalytic materials'physical and chemical characteristics.And then design the two-stage catalytic system,and to reveal the mechanism of U/Mn degradate of chlorobenzene.Firstly,the characteristics of the catalytic materials,U doped-?-MnO2,were compared systematically.SEM,XRD,H2-TPR and other characterization methods were used to analyze the material structure and surface properties of U doped-?-MnO2.The results showed that the catalytic properties of the catalytic materials prepared from large to small were:Al/Mn ? Fe/Mn>Ce[Mn>Cu/Mn>Co/Mn(Reaction Condition:Catalyst=0.2 g,CB concentration= 100 ppm,GHSV= 15000h-1,O2=20%);Al/Mn has the highest specific surface area(539.82 m2·g-1)and the highest chlorobenzene catalytic degradation performance and it also has a compact pore structure and a high REDOX capability.Cu/Mn has the highest REDOX ability,and Fe/Mn has the highest the low temperature activity.Then,the catalytic performance of Al/Mn,Cu/Mn and Fe/Mn were further investigated,and a two-stage catalytic system was built according to the design concept of first adsorption and then redegradation.In two adiabatic fixed reaction beds,Al/Mn-Cu/Mn and Al/Mn-Fe/Mn,the ideal synergistic effect can be achieved,and the catalytic efficiency is significantly improved relative to the individual effect.However,under the same reaction conditions,the life of Al/Mn-Cu/Mn is longer,and after a 3 5-hours reaction,it still maintains a high catalytic activity of more than 90%chlorobenzene catalytic degradation performance.The above three catalytic materials,Al/Mn,Cu/Mn and Fe/Mn,were respectively carried out for the analysis of catalysts,as well as the investigation of chlorobenzene degradation of tail gas.The possible degradation mechanism of chlorobenzene was as follows:Under the react of Fe/Mn,chlorobenzene was first be degradated to benzene,phenol and 4-Hydroxy-4-methyl-2-pentanone,4-hydroxy-2-pentone,chloroacetone,2,5-diketone and intermediate products,such as benzene,formaldehyde,and then,by further oxidation,intermediate thoroughly be degradated into small molecule,such as CO2 and HCl,Osur plays a major role in active sites,but FeOx may promote the formation of a variety of intermediates,and Fe/Mn has low selectivity of CO2 and HCl;While,the role of Al/Mn and Cu/Mn are roughly the same,chlorobenzene was first be degradated to benzene,phenol and 4-Hydroxy-4-methyl-2-pentanone,and then,by further oxidation,intermediate thoroughly be degradated into small molecule,such as CO2 and HCl,Osur and Olatt play major roles in active sites,and Al/Mn and Cu/Mn own low selectivity of CO2 and HCl;Al/Mn-Cu/Mn has the highest selectivity of CO2 and HC1.