Study Of Catalytic Oxidation Of Chlorobenzene By Manganese Cobalt Oxide Supported On Iron/manganese Ore

With the development of industry,the VOCs pollution has been widely concerned.Large amount of VOCs were produced in the process of industrial production,which has even threat to the ecological environment security and human health.Therefore,it is urgent to seek an efficient,environmentally friendly and low-cost VOCs control technology to achieve more stringent emission standards.In this paper,manganese ore and iron ore were used as precursors to prepare composite catalysts of minerals and metal oxides for the catalytic oxidation of gaseous chlorobenzene.The catalytic properties of the manganese ore/Co₃O₄composites were investigated by X-ray diffraction（XRD）,field emission scanning electron microscopy（FE-SEM）,N₂adsorption-desorption（BET）,X-ray photoelectron spectroscopy（XPS）and H₂-temperature programmed reduction（H₂-TPR）.The self-made device was used to test the catalytic oxidation efficiency of catalysts for gaseous chlorobenzene.The effects of doping ratio,calcination temperature and other factors on the catalytic activity of the composite catalyst were explored.The conclusions were as follows:1.Manganese ore/cobalt oxide composites were synthesized by using natural manganese ore and Co（NO₃）₂·6H₂O via oxalic acid-assisted sol-gel method and applied in the catalytic oxidation degradation of gaseous chlorobenzene.The results showed that the composite catalyst with the mass ratio of manganese ore/cobalt oxide was 0.4 and calcined at 450℃had the optimal catalytic performance.It could achieve 94%conversion of chlorobenzene,83%selectivity of CO₂and over 36 h sustainability at 300℃for the gaseous chlorobenzene with the initial concentration of1200 mg/m³.The composite catalyst had the abundant surface oxygen species,good anti-chlorine poisoning performance and strong redox properties of composites,which were due to the interaction between manganese ore and Co₃O₄,and played a key role in degradation of chlorobenzene.2.MnCoO_xcomposite was prepared by using manganese acetate and cobalt nitrate via oxalic acid-assisted sol-gel method.The results showed that the composite catalyst with Mn/Co molar ratio of 0.4:0.6 and calcined at 450℃for 3 h had good performance.The conversion of chlorobenzene can reach 95%at 300℃when the initial concentration of chlorobenzene was 1200 mg/m³and GHSV was 24000 h^-1.The experimental results showed that the improvement of catalytic performance of MnCoO_xcomposite catalyst was mainly related to the high concentration of surface oxygen produced by the interaction between Mn and Co.3.The Mn-Co/α-Fe₂O₃composite catalysts were prepared via oxalic acid-assisted sol-gel method by loading Mn-Co on goethite and was used to degrade chlorobenzene.The results showed that the composite catalyst with Mn:Co:Fe=0.3:0.45:1（mole ratio）calcined at 500℃had the optimal catalytic performance.When the reaction temperature was 350℃,the composite catalyst could reach more than 93%conversion of chlorobenzene.The degradation products of chlorobenzene and CO₂selectivity were analyzed by FTIR.Indicated that composite catalyst had the abundant surface oxygen species,high specific surface area and strong redox properties,which were beneficial to catalytic oxidation of chlorobenzene.4.（Mn-Co）/Siderite composite catalyst was prepared by oxalic acid-assisted sol-gel method.The results showed that the composite catalyst calcined at T=450℃with mass ratio of（Mn+Co）/Fe=0.6 had the best catalytic performance.When the reaction temperature was set at 350℃,the degradation of chlorobenzene could reach more than 90%,and the composite catalyst had deep oxidation performance and good stability.The results show that compared with Siderite,（Mn-Co）/Siderite composite catalyst had larger specific surface area,higher surface oxygen concentration and stronger oxidation-reduction performance,which were conducive to the catalytic oxidation of chlorobenzene.