Tin Oxide And Niobium Oxide Modified By Alkali Metals For Soot Particulate Combustion

Soot particulates have a great threat to people's living environment and their health,hence it is imminent to eliminate their pollution.Catalytic combustion is an effective method to eliminate soot particulate pollution,and its core issue is to develop a low-cost and highly active catalyst.Based on the characteristics of soot particulate combustion,in this paper,the reaction performance of SnO2 and Nb2O5 modified by different alkali metals have been investigated.By means of XRD,Raman,H2-TPR,XPS,EPR,In situ DRIFTS,FTIR,O2-TPD etc.,the structure-reactivity relationship of the catalysts have been characterized and elucidated.The main results are summarized here:Part 1:First,a series of SnCo solid solutions were prepared by a coprecipitation method.The lattice capacity of Co ions in the SnCo solid solution is 0.0934g Co3O4/g SnO2,which is calculated by XRD extrapolation method,equaling to a molar ratio of Sn/Co=85/15(SC85-15).By using SC85-15 as the support,a series of x%Cs/SC85-15 catalysts were prepared by an impregnation method for the reaction.Compared with the unmodified SnO2,the activity of SC85-15 catalyst is higher.After loading CsNO3 on SC85-15 surface,it is found that the combustion activity is further improved,and the activity increases with the increase of CsNO3 content.When the content of CsNO3 reaches 8%,its activity also reaches the highest.Through the characterization by H2-TPR,XPS,EPR and In situ DRIFTS,it has been found that the addition of CsNO3 can produce more active oxygen species(O22-,O2-)on SC85-15 surface.8%Cs/SC85-15 catalyst owns the largest amount of active oxygen species,thus it displays the highest activity among all the catalysts.Part 2:Nb2O5 modified by different alkali metal nitrates has been prepared as catalysts for soot particulate combustion by an impregnation method.The activity of all the modified catalysts is better than that of the unmodif ed Nb2O5.The activity sequence is CsNb1-9>KNb1-9>NaNb1-9>LiNb1-9>Nb2O5.By means of XRD,Raman,TGA-DSC methods,it has been found that LiNO3 and NaNO3 exist mainly in the form of Li2O and Na2O on Nb2O5 surface,while KNO3 and CsNO3 exist mainly in the form of nitrates on Nb2O5 surface.FTIR has proved that NO3-is the main active centers for the reaction.As a consequence,the activity of CsNb1-9 and KNb1-9 are much better than that of NaNb1-9 and LiNb1-9.