Study On Structure Regulation And Catalytic Oxidation Of Composite Oxide Catalysts Of CVOCs

Chlorinated volatile organic compounds?CVOCs?have attracted extensive attention due to their extensive sources,strong acute toxicity,difficult degradation and easy formation of polychlorinated by-products.At present,catalytic oxidation has become the mainstream technology and development direction in the research and application of CVOCs management industry,and the preparation of efficient,stable and cheap catalysts is the core of catalytic oxidation technology.In this essay,a series of catalysts supported on cordierite were synthesized by the citric acid complex method,showing preferable catalytic oxidation of chlorobenzene.We studied Manganese base composite metal oxides,perovskite-type composite oxides and spinel-type oxides catalysts.We changed The types of doped metals,ratio and calcination conditions to explore the best preparation conditions.using XRD,BET,SEM,TEM,H₂-TPR,NH₃-TPD,IR and XPS technical to analyse the properties and microstructure of the catalysts.The results show that:1)The distribution of active oxides,surface areas,the structural morphology,water absorption,oxidation pathway and oxidation activity of M-MnO_x-CeO₂ catalysts varied with the different Mn/Ce and M/Mn molar ratios.The CuO-MnO_x-CeO₂ catalysts showed a higher chlorobenzene conversion than FeO_x-Mn Ox-CeO₂.Comparative analyses of two catalysts indicated that the main cause of the oxidation activities and mechanisms were different in the oxidation capacity and water absorbability of FeO_x and Cu O.2)Because of the special crystal structure of perovskite-type composite oxides,and the abnormal valence state and defect of b-site ions,the oxidation performance of the catalyst will be greatly affected.Researches have found that as the catalyst calcination temperature increasing to 650?,the oxide particles loaded on the catalyst surface is the most fragmented,and its oxidation activity is the best.and when the reaction temperature is 350?,catalyst oxided chlorobenzene conversion rate can reach 96.4%,the reason is high calcinations temperature for catalysts form LaCoO₃ perovskite-type composite oxides.3)The activities of CuM_xMn_2-xO₄ catalysts could be significant improvement accompanied by a low calcining temperature and time.Attributed to CeO₂ nano-rods structure conducive to increase the Oads,even higher than Olatt,a high dispersion of active oxides,the weak strength of weak acidity and a high surface areas and pore volume,CuCe_0.25Mn_1.75O₄ catalyst displayed the highest activity and stability.Moreover,it was noted that CuMn₂O₄ spinel-type with Ce doping exhibited a high performance in CVOCs elimination had attracted more attention ascribed to high storage capacity of oxygen,plentiful oxygen vacancies,effect in breaking C-Cl bond and the easy shuttles between Ce³⁺ and Ce⁴⁺.