Preparation Of MOFs Derived Composite Metal Oxides And Its Catalytic Activity For Oxidation Of O-dichlorobenzene

Chlorinated volatile organic compounds（CVOCs）are one of the air pollutants,which are highly toxic and difficult to degrade.The elimination of CVOCs is an important issue in environmental protection.So far,catalytic combustion has been widely considered as one of the most effective and promising technologies that strictly meet the VOCs emission standards.Carcinogenic and toxic o-dichlorobenzene（o-DCB）was designed as a model gas to evaluate the catalytic properties of the catalyst.Manganese oxide,cobalt oxide and nickel oxide are considered to be effective transition metal oxide catalysts.Their activity is not only determined by chemical composition,but also closely related to synthesis method,size,morphology,structure and surface defects.In this project,we designed and synthesized MnO_xwith different morphologies catalyst for achieving stable and efficient oxidative decomposition of o-DCB at low temperature（<500℃）.It mainly includes the following contents:1.A series of porous catalysts（MnO_x-D,MnOx-D/H,MnOx-D/M and MnO_x-D/H/M）were prepared by regulator assisted synthesis.The catalytic performance of these MnOx catalysts for o-dichlorobenzene（o-DCB）combustion was evaluated.The catalysts were characterized by bet,XRD,Raman,SEM,TEM,XPS,H₂-TPR and O₂-TPD,and their physicochemical properties were tested.The effects of solvents on the morphology and properties were investigated.The results shown that the catalyst with N,N-dimethylformamide（DMF）as solvent has sponge like morphology and the best catalytic performance(T₉₀=321℃).2.A series of catalysts with different core-shell structures were prepared by hydrothermal method.Then,the effect of core-shell structure on the catalytic performance of o-dichlorobenzene was studied by activity,water resistance,thermal stability test and catalyst characterization.The catalyst coated with Nb₂O₅shell（Ce Co O_x@Nb₂O₅）has the best activity(T₉₀=362℃).It is mainly due to its special core-shell structure,large specific surface area,rich active species(Co³⁺,Ce³⁺,Nb⁵⁺),strong reducibility and more active oxygen vacancies.In addition,the catalyst coated with Ti O₂（Ce Co O_x@Ti O₂）was more stable.There was almost no decrease in activity within 1200 minutes.The possible reaction pathways of MVK and L-H models were speculated by means of O₂-TPD,XPS and In-situ FTIR.3.Nickel based catalysts with hollow spherical shell and nanoflower structure were prepared by hydrothermal method and used for the catalytic oxidation of o-dichlorobenzene.The effects of different preparation methods and metal doping（Mn-Co,Mn-Cu and Mn-Fe）on the catalytic oxidation of o-DCB were studied.The results shown that the Co doped catalyst synthesized in air（Ni O@MnCoO_x）showed that the best activity(T₉₀=375℃)and good thermal stability were observed.The main reasons are the unique core-shell structure,large specific surface area,lattice distortion or distortion residual stress,more surface species(Ni²⁺,Mn⁴⁺and Co³⁺),rich active oxygen species,strong redox ability and a large number of strong acid centers.This strategy provides a new way for the design of nickel based composite catalyst.