Study Of Coated Cobalt-Based Oxides For Low-Temperature Catalytic Oxidation

Catalytic oxidation of CO is one of the effective environmental protection technologies to remove CO.There are many factors affecting the activity of CO oxidation,such as water vapor content,precursor solution,preparation method,calcination temperature and aggregation degree of catalyst,etc.Non noble metal oxides,especially cobalt based catalysts,have attracted increasing attention recently.Although cobalt based catalysts have excellent catalytic performance for CO oxidation at low temperature,they are easily inactivated under moisture-rich condition.Therefore,It has important research value and practical significance about how to improve the catalytic performance of CO oxidation at low temperature under moisture-rich condition.The major research results of this thesis are summarized as follows:(1)The research status of Co based,Cu based and Ce based non precious metal oxide catalysts in wet gas was reviewed.The mechanism of CO catalytic oxidation and water deactivation were discussed.At present,our group is working hard to construct a new type of water-resistant polymer nanofilm to improve the water-resistant performance,and then enhance the CO oxidation activity,and has achieved some results,and put forward suggestions for future research.(2)On the basis of our previous work,the use of manganese nitrate aqueous solution(50 wt.%)precursor instead of solid manganese nitrate has achieved the purpose of increasing the system dispersion and Co-Mn ion interaction.The coating of polymer nanofilm can not only improve the structural stability of transition metal oxide,but also improve its catalytic performance at low temperature and rich water.In this work,through the optimization of polymer nanofilm coated catalyst MnaCobOx,we achieved stable and effective CO oxidation(T100=50?)under the condition of rich water(0.6 vol.%H2O).The catalyst was characterized by TEM,TG,FTIR,XPS,XRD,TPD and other auxiliary technologies.The X-ray photoelectron spectroscopy(XPS)showed that the activity of the catalyst was related to the ratio of Co3+/Co2+and Mn2+/Mn3+and the percentage of oxygen vacancy(vO).In addition to the hydrophobicity of the coating polymer,the synergistic effect of Co-Mn ion and oxygen vacancy also played an important role in the low-temperature cross membrane CO oxidation.The mechanism of CO catalytic oxidation in polymer nanofilm coating was discussed.(3)The combustion activity and stability of Mn3Co32OX catalyst prepared above were tested.It was found that the conversion of CH4 could reach 90%at 335?.The high activity was due to the high content of oxygen vacancy(vO)and the interaction between Mn-Co ions.(4)The effect of KMnO4 doping on the activity of Fe3Co16Ox+XMn(X=0,0.3,0.6,1,3,6)catalyst for CO oxidation was studied.Fe3Co16Ox+XMn catalyst coated with polymer nanofilm was prepared by solid phase grinding.It was found that Fe3Co16Ox+1Mn had the highest activity(60?,0.6 vol.%H2O)for CO oxidation.Compared with pure Fe3Co16Ox(80?,0.6 vol.%H2O),its catalytic activity increased by 20?.The catalyst was characterized by XRD,TEM,XPS,BET and so on.The crystal structure and morphology analysis showed that the nano crystal size and spherical morphology.The synergism among Fe,CO and Mn affects the contents of Fe3+,Co3+and oxygen vacancy(vO)on the spherical surface,thus improving the oxidation property.The data extracted by XPS showed that the catalysts with high Co3+/Co2+(1.66),high Fe3+/Fe2+(1.43),and high vO(16.04%)had the highest catalytic activity for CO oxidation.