Preparation Of Cobalt-manganese Composite Metal Oxides And Research On Catalytic Oxidation Of VOCs

Volatile organic compounds(VOCs)are one of the serious air pollutants,which are caused by industrial activities,oil field development and incomplete combustion of coal,and are harmful to human health.Catalytic oxidation technology has become one of the main methods to dispose volatile organic pollutants due to its advantages of high efficiency,wide application range and no secondary pollution,and it has a good application prospect.However,how to improve the activity and achieve its stability is currently a difficult problem in the design of VOCs degradation catalyst.Therefore,in order to improve the catalytic performance and achieve high stability and strong resistance to water,this paper prepared a series of transition metal oxide catalysts with high efficiency to eliminate VOCs.Metal-organic framework(MOFs)materials have relatively high specific surface area and abundant pore structures,and their derivatives can retain these characteristics,which showed excellent performance for the treatment of VOCs.Nickel Foam substrate has stable skeleton structure,abundant porous structure,and thermal stability,which is suitable for VOCs degradation in industrial production.However,its performance of catalytic oxidation of VOCs is not satisfactory,and it needs to be improved urgently.So we did the following two things:1.Mn promoted Co₃O₄ catalysts derived from MOF were prepared via a cooperative pyrolysis-adsorption-oxidation strategy,and the catalytic performance was evaluated by toluene oxidation.The obtained MnO_x/Co₃O₄ catalysts exhibited the superior catalytic activity compared with Co₃O₄ catalyst,which is related to the promoting effect of Mn.Mn species were mainly incorporated on the surface of Co₃O₄,exhibiting the high dispersion of Mn.X-ray absorption spectroscopy(XAS)revealed that the occupation of Mn cations in octahedral Co³⁺sites could give rise to the local lattice distortion of the spinel structure,resulting in highly exposed surface defect.The incorporation of Mn species also facilitated the good low-temperature reducibility,high mobility of lattice oxygen and predominately surface Co³⁺sites.As a result,MnO_x/Co₃O₄-10 catalyst exhibited the low temperature of toluene conversion and Ea value under the condition without or with 5.8 vol%H₂O.In situ DRIFTS results confirmed that the toluene oxidation was a continuous oxidation process,and the conversion of benzoate into maleic anhydride should be the rate-controlling step.2.A series of MnO_x/Co₃O₄@Ni Foam catalysts with stable structure were synthesized by an in-situ growth-sculpture-pyrolysis method.Its catalytic performance was evaluated by oxidation of benzene.XRD and electron microscope analysis can infer that Mn component is uniformly distributed on the surface of the catalyst.XPS results showed that CO³⁺and Mn³⁺species dominated on the catalyst surface,which were the active sites for VOCs oxidation in previous reports.At the same time,excellent low temperature reducibility and high lattice oxygen concentration improve the catalytic performance of benzene.MnO_x/Co₃O₄@Ni Foam-2 showed excellent catalytic stability,and the catalytic activity of MnO_x/Co₃O₄@Ni Foam-2 did not decrease for 80 h.This work provides a research basis for the combination of active metal and Ni Foam substrate for the industrial treatment of VOCs.