Study On Denitrification Performance Of SCR Catalyst Based On Mn At Low Temperature

Nitrogen xides(NOx)in life are mainly nitrogen xide(NO)and nitrogen dixide(NO2).When their content and time in the atmosphere reach a certain extent,they will produce uncountable consequences for human health and the natural environment.For example,inhalation of NOx in the deep part of the human lung may lead to emphysema or bronchitis;NOx and hydrocarbons react with ultraviolet radiation to form photochemical smog.Meanwhile,N2O react with water in the atmosphere to form nitric acid and nitrite,which is one of the main causes of acid rain.N2O can also reduce ozone in the stratosphere,and increase the amount of ultraviolet radiation to the earth.At present,there are two main measures to control NOx emissions:the first is combustion control technology,secondly,flue gas purification technology,and the most common and most commonly used is the SCR(Selective Catalytic Reduction)-selective catalytic reduction method.In the presence of a specific catalyst,the reductant NH3 has the choice of reducing NO and NO2 to N2,without the xidation of NH3 and O2.The most widely used commercial denitration catalyst is vanadium tungsten titanium(V2O5,-WO3(MoO5)/TiO2)catalyst.The catalyst has good catalytic effect in a relatively high temperature range,but there are many shortcomings.For example,low temperature efficiency is not high(active window 300-400 degrees),easy to generate toxic gas N2O,sulfur resistance is poor and catalyst is easy to poison and inactivate.Therefore,the development of low temperature catalytic activity and sulfur resistant SCR catalyst has high research value.In view of the above problems,hydrothermal synthesis of Mn-Ce/TiO2 catalyst is carried out in this paper,and its properties are improved in different ways.First,the effects of the time of the hydrothermal reaction,the proportion of drugs and the addition order,the temperature of water bath,the calcination temperature and the air velocity on the denitrification performance of the catalyst were investigated.The optimum time for the reaction of MIL-125(Mn)to the synthesis catalyst was 15h,and the optimum ratio of Mn:Ti to the addition of drugs was O.1.At the same Time,the best dosing order is terephthalic acid before isopropyl titanate.The best temperature of water bath for dissolving drugs is 30.The best roasting temperature is 400? in the muffle furnace after impregnation,and the best denitrification performance of the catalyst when the air velocity is 30000h-1.It has been proved that the addition of Ce in the catalyst has a low SCR activity in the high temperature range,but it has a good conversion rate at the low temperature range(125?300?).At the same time,the conversion rate of nitrogen xides can remain about 45%after 4 hours of SO2 influence.Finally,on the basis of this study,a comparative experiment was carried out by loading Mn on TiO2.The results showed that the catalyst showed the best denitrification activity when the load of Mn was about 10%in the Mn-TiO2 catalyst.However,when compared with MIL-125(Mn)catalyst,it is found that the denitrification effect of MIL-125(Mn)catalyst is much better than that of Mn-TiO2 catalyst when the reaction temperature is over 175?.At the same time,the addition of Ce in the catalyst will greatly help to improve the sulfur resistance of the catalyst.It is further proved that MIL-125(Mn-Ce)catalyst has great potential in the field of denitration catalyst.