Study On The Novel Catalysts For Dichloromethane Purification

Dichloromethane（DCM）is an important chemical material and reaction solvent.If it is volatilized or released into the atmosphere during use,will be posing a huge threat to the environment and biological health.Catalytic combustion method can achieve high temperature and stable removal of DCM pollutants at low temperature.In this thesis,a series of iron-based transition metal oxide catalysts were designed for catalytic combustion to remove DCM.Their activity,selectivity,cyclic stability and long-term stability for catalytic oxidation of dichloromethane were investigated.The effects of reaction space velocity and preparation conditions on the conversion of DCM were studied,through a series of characterization to explore its reaction mechanism.The main research work is as follows:（1）The Fe-Zr catalyst was prepared by coprecipitation method and its catalytic oxidation performance to dichloromethane was tested.It is found that the catalytic activity of catalyst for dichloromethane increases with the increase of Fe/Zr atomic molar ratio.When the Fe/Zr ratio is 4:1,the calcination temperature is 550℃,the calcination time is 2.5 h,Fe₄Zr₁Catalyst performance is optimal,T₉₀=342℃.This is related to the crystal structure of the catalystα-Fe₂O₃and good redox properties;the Fe₄Zr₁catalyst is doped with the active component Mn.It is found that the addition of Mn improves the activity,selectivity and stability of the catalyst,Fe Zr-Mn_3.6（Fe/Zr/Mn=4:1:3.6）catalyst performance is optimal,T₉₀=331℃,T₅₀=186℃.The selectivity to CO₂reached 100%at 310℃.This is because the doping of Mn increases the oxygen concentration on the surface of the catalyst,and the presence of Mn⁴⁺-Mn²⁺enhances the low-temperature reduction performance of the catalyst,thus facilitating the redox reaction between the dichloromethane and catalyst.（2）A Fe-Ni catalyst was prepared and applied to the catalytic oxidation of dichloromethane.It is found that the catalytic activity of catalyst increases with the increase of Fe/Ni atomic molar ratio.The calcination temperature is 450℃and the calcination time is 1.5 h.The Fe₄Ni₁catalyst with Fe/Ni molar ratio of 4:1 has the best performance,T₉₀=306℃,T₅₀=230℃.This is because Fe₄Ni₁catalyst has a large amount of medium strong acid,stable crystal structure and excellent low-temperature redox property;the Fe₄Ni₁catalyst is doped with active component Cr,and it is found that the addition of Cr improves the performance of various aspects of the catalyst,The FeNi-Cr₂（Fe/Ni/Cr=4:1:2）catalyst has the best performance,T₉₀=256℃and T₅₀=175℃.This is because the doping of Cr makes the catalyst have a large amount of weak acid and medium strong acid,and a plurality of low-temperature redox peaks are favorable for the reaction between the catalyst and dichloromethane.The Cr species in the FeNi-Cr₂catalyst is not lost in the crystal lattice,thus maintaining the stability of the catalyst and high oxidation.