| Selective catalytic reduction?SCR?technology is a key technology in flue Cas denitrification process.NO2 as an important reaction intermediates in SCR reaction hua a strong oxidizing and is more easily to be reduced.Therefore,to study the NO catalytic oxidation technology has an important guiding significance on the improvement of SCR technology.Increasing the conversion efficiency of NO can effectively improve the denitrification efficiency of low temperature wet denitrification and SCR technology.Co-based catalyst has the characteristics of low cost,high oxidation activity and high oxygen storage capacity.It is a kind of catalyst suitable for operation in NO catalytic oxidation technology.Some Co-based composite oxide catalysts and Co-supported catalysts have exhibited good NO oxidation activity,but the alkali metal,alkaline earth metals,heavy metals and H2 O,SO2 in flue Cas will affect the catalytic oxidation activity of NO.In this paper,Co/TiO2 catalyst was prepared by using TiO2 prepared by sol-gel method as the carrier and the metal oxide Co as the active component.The effects of flue Cas fly ash on the NO catalytic oxidation of Co/Ti O2 catalyst was researched and the mechanism of flue Cas fly ash on Co/TiO2 catalyst was analyzed by means of various characterization methods.In this paper,fly ash?alkali metal,alkaline earth metal,heavy metal?was impregnated into Co/TiO2 catalyst to study the effect of fly ash on NO oxidation activity of Co/Ti O2 catalyst.Based on TPR,NO + O2-TPD and In situ DRIFT characterization technology,it was found that the fly ash composition had toxicity effects on the NO oxidation activity of Co/TiO2 catalyst.The effects of different concentrations of Na on the NO oxidation of Co/Ti O2 catalysts were compared.The addition of Na inhibit the activity of Co/Ti O2 catalyst especially at high temperature and also inhibited the adsorption of NOx species.The monodentate nitrates adsorption peak may play an inhibitory effect in this experiment due to the addition of Na.The presence of monodentate nitrates will compete with the nitrates which promote the NO oxidation activity.Secondly,the effects of different K salts on the catalytic activity of Co/Ti O2 catalyst were studied.After poisoning K salt,the poisoning of fresh catalyst was weak in the range of 100? 200?,and the poisoning was significant at high temperature?> 200??.The toxicity of KOH was the most serious.The doping of K reduces the oxygen storage capacity of the catalyst and reduces the adsorption capacity of NO and NO2.K salt changes the adsorbed state of the NOx species on the surface of the Co/Ti O2 catalyst rather than the thermal stability of adsorbed state.Besides,it also reduces the catalytic oxidation rate between NO and O2.The Co/TiO2 catalyst before and after the doping of Mg and Ca alkaline earth metals was studied.The poisoning of Mg on the fresh catalyst is relatively weak,and Ca is more obvious.In situ DRIFT analysis showed that the doping of alkaline earth metals did not change the state of adsorbed species on the surface of the catalyst.It mainly inhibited the adsorption capacity of NOx and weakened the thermal stability of NO2 and bidentate nitrates.Finally,we studied the Co/TiO2 catalysts which were prepared with Pb and Zn.The inhibition mechanization of heavy metal elements is revealed by characterization.In situ DRIFT characterization indicates that the exist of linear nitrates and monodentate nitrates adsorption peaks on the Co/Ti O2-Pb due to the decrease of the denitrification activity.The addition of Zn reduces its NOx adsorption capacity of NO2 adsorption peak and bidentate nitrates adsorption peak.The newly produced monodentate nitrates inhibits the denitrification activity,which reduces the NO oxidation activity.The addition of heavy metals reduced the thermal stability of Caseous NO2 and bidentate nitrates,and the thermal stability of linear nitrates and monodentate nitrates was strong which give no effect on NO oxidation activity. |
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