The Study Of Catalytic Combustion For Dichloromethane Over Cerium-based Catalysts

Chlorinated volatile organic compounds?CVOCs?,used in many kinds of chemical production process,was one of the main pollutants for air.Catalytic combustion is one of most effective way to eliminate CVOCs pollution,mainly due to its lower energy consumption and higher efficiency.In the present work,Single CeO₂ catalyst with different shape and Nano-structured Mn-Ce mixed oxides catalysts were prepared,and the catalytic combustion of dichloromrthane?DCM?on these catalysts was investigated,The physical-chemical properties of catalysts were characterized by TEM,XRD,BET and H₂-TPR.The results showed as follows:?1?Nanorod,nanocubes and nanopolyhedra of cubic CeO₂ were successfully prepared by a hydrothermal method,with the bulk CeO₂ was prepared by the thermal decomposition method.The overall activity order of CeO₂ with different crystal shape was:CeO₂-rod>CeO₂-bulk>CeO₂-polyhedra>CeO₂-cubes.The CeO₂-rod was identified as the most active catalyst(T₅₀=278?and T₉₀=323?)for the abatement of 1000ppm DCM in air.The BET and H₂-TPR characterization results indicated that CeO₂-rod possesses high surface area?86.41m²/g?and excellent lower-temperature redox properties.The shape of the catalysts not only affect the catalytic avtivity,but also changed the selectivity of the products.?2?For CeO₂-rod support,the different Mn doping method was investigated.It found that the catalytic activity and product selectivity decreased with Mn-doping.However,using CeO₂-cubes as the support,Mn modification can improve the catalytic activity and product selectivity and exhibits the good catalytic activity and selectivitybecause of forming Mn-Ce solid solution.?3?Mn-Ce mixed oxides catalysts with various content of Mn were prepared by equivalent-volume impregnation,and tested for catalytic combusition of DCM.The result showed that the MnO_x-CeO₂ catalysts extent high catalytic activity and good chlorine resistant stability;4%Mn/CeO₂-cube exhibits high catalytic activity and selectivity(T₅₀=274?and T₉₀=314?).This could be due to the Mn²⁺changed the type and the amount of the CeO₂ crystal plan,then formed more oxygen vavancies and improved the mobility of reactive oxygen species,thus the catalytic activity of the catalysts increased.In addition Mn-doped can promoted the Deacon reaction,which is related to its high ability to remove Cl species adsorbed on the catalysts turned into HCl and Cl₂?...